Various methods for forming surface micromachined microstructures are disclosed. One aspect relates to executing surface micromachining operation to structurally reinforce at least one structural layer in a microstructure. Another aspect relates to executing the surface micromachining operation to form a plurality of at least generally laterally extending etch release channels within a sacrificial material to facilitate the release of the corresponding microstructure.

The present invention generally relates to making a microstructure by surface micromachining. One aspect relates to making a structurally reinforced microstructure to provide a flatter profile on one or more of its structural layers. Another aspect relates to providing a plurality of at least generally laterally extending etch release channels to facilitate the release of the microstructure from the substrate.
There are a number of microfabrication technologies that have been utilized for making microstructures (e.g., micromechanical devices, microelectromechanical devices) by what may be characterized as micromachining, including LIGA (Lithographie, Galvonoformung, Abformung), SLIGA (sacrificial LIGA), bulk micromachining, surface micromachining, micro electrodischarge machining (EDM), laser micromachining, 3-D stereolithography, and other techniques. Bulk micromachining has been utilized for making relatively simple micromechanical structures. Bulk micromachining generally entails cutting or machining a bulk substrate using an appropriate etchant (e.g., using liquid crystal-plane selective etchants; using deep reactive ion etching techniques). Another micromachining technique that allows for the formation of significantly more complex microstructures is surface micromachining. Surface micromachining generally entails depositing alternate layers of structural material and sacrificial material using an appropriate substrate which functions as the foundation for the resulting microstructure. Various patterning operations may be executed on one or more of these layers before the next layer is deposited so as to define the desired microstructure. After the microstructure has been defined in this general manner, the various sacrificial layers are removed by exposing the microstructure and the various sacrificial layers to one or more etchants. This is commonly called xe2x80x9creleasingxe2x80x9d the microstructure from the substrate, typically to allow at least some degree of relative movement between the microstructure and the substrate. Although the etchant may be biased to the sacrificial material, it may have some effect on the structural material over time as well. Therefore, it is generally desirable to reduce the time required to release the microstructure to reduce the potential for damage to its structure.
Microstructures are getting a significant amount of attention in the field of optical switches. Microstructure-based optical switches include one or more mirror microstructures. Access to the sacrificial material that underlies the support layer that defines a given mirror microstructure is commonly realized by forming a plurality of small etch release holes down through the entire thickness or vertical extent of the mirror microstructure (e.g., vertically extending/disposed etch release holes). The presence of these small holes on the upper surface of the mirror microstructure has an obvious detrimental effect on its optical performance capabilities. Another factor that may have an effect on the optical performance capabilities of such a mirror microstructure is its overall flatness, which may be related to the rigidity of the mirror microstructure. xe2x80x9cFlatnessxe2x80x9d may be defined in relation to a radius of curvature of an upper surface of the mirror microstructure. This upper surface may be generally convex or generally concave. Known surface micromachined mirror microstructures have a radius of curvature of no more than about 0.65 meters.
The present invention is generally embodied in a method for making a microstructure by surface micromachining. In this method, at least one and more typically a plurality of at least generally laterally extending etch release channels or conduits are formed within a sacrificial material. This sacrificial material is used to fabricate the microstructure on an appropriate substrate. At least some of this sacrificial material is removed when the microstructure is released from the substrate (and thereby encompassing the situation where all of this sacrificial material is removed).
A first aspect of the present invention is embodied in a method for making a microstructure by surface micromachining that includes forming a first structural layer over a sacrificial material. xe2x80x9cOverxe2x80x9d includes being deposited directly on the substrate or being deposited on an intermediate layer that is disposed between the subject sacrificial layer and the substrate. xe2x80x9cOnxe2x80x9d in contrast means that there is an interfacing relation. In any case, a plurality of hollow etch release pipes, channels, conduits, or the like extend at least generally laterally through/within this sacrificial material. Lateral or the like, as used herein, means that the etch release conduits are disposed or oriented in a direction which is at least generally parallel with the substrate. Although the etch release conduits will typically extend laterally at a constant elevation relative to the substrate, such need not necessarily be the case. Ultimately, at least some of the sacrificial material is removed at least in part by allowing an etchant to flow through any and all of these hollow etch release conduits (and thereby encompassing the situation where all of this sacrificial layer is removed).
Various refinements exist of the features noted in relation to the first aspect of the present invention. Further features may also be incorporated in the first aspect of the present invention as well. These refinements and additional features may exist individually or in any combination. In one embodiment, at least one end of at least one etch release conduit may be disposed at least generally at the same radial position as a perimeter of the first structural layer. Hereafter, xe2x80x9cat least generally at the same radial positionxe2x80x9d in relation to any end of any etch release conduit or structure used to define the same means within 50 xcexcm of the radial position of the perimeter of the relevant structural layer in one embodiment, more preferably within 25 xcexcm of the radial position of the perimeter of the relevant structural layer in another embodiment, and even more preferably at the same radial position as the perimeter of the relevant structural layer. As such, the etchant does not have to etch in from the perimeter xe2x80x9ctoo farxe2x80x9d before encountering an open end of one or more etch release conduits associated with the first aspect. Reducing the time required for the etchant to reach the etch release conduits should at least to a point reduce the overall time for accomplishing the release of the microstructure from the substrate.
Various layouts of the plurality of etch release conduits in the noted lateral dimension may be utilized in relation to the first aspect. In one embodiment, each of the plurality of etch release conduits may be disposed in non-intersecting relation, in another embodiment the plurality of etch release conduits are disposed in at least substantially parallel relation, and in yet another embodiment at least some of the etch release conduits intersect. The plurality of etch release conduits may extend at least generally toward (and thereby including to) a common point, such as one that corresponds with a center of the first structural layer in the lateral dimension. All etch release conduits need not extend the same distance toward this common point, although such may be the case. Some of the plurality of etch release conduits may extend at least generally toward (and thereby including to) a first common point (e.g., one that corresponds with a center of the first structural layer in the lateral dimension), while some of the plurality of etch release conduits may extend toward a different common point. The plurality of etch release conduits may also extend in the lateral dimension in a variety of configurations. In one embodiment, the plurality of etch release conduits are at least generally axially extending, while in another embodiment the plurality of etch release conduits are non-linear (e.g., in a sinusoidal configuration that is at least generally parallel with the substrate).
In one embodiment of the first aspect, the laterally extending etch release conduits are completely defined before the stack that includes the microstructure being fabricated by the methodology of the first aspect is exposed to a release etchant for removing the first sacrificial layer. One particularly desirable application for the first aspect is in the formation of a mirror microstructure or multiple mirror microstructures for a surface micromachined optical system that has at least some degree of movement relative to the first substrate. Because of the presence of the plurality of laterally extending etch release conduits, there is no need to have a plurality of etch release apertures or holes that extend entirely down through the entire vertical extent of the first structural layer to remove the sacrificial material that directly underlies this first structural layer. That is, there is no need for a plurality of vertically disposed etch release apertures, with xe2x80x9cverticalxe2x80x9d being at least generally opposite xe2x80x9clateral.xe2x80x9d As such, the upper surface of the first structural layer retains a very smooth surface that lacks any such vertically disposed etch release apertures, which makes the microstructure that is made by the methodology of the first aspect particularly suited for use in optical applications. This is true whether the upper surface of the first structural layer is the actual optical surface for the mirror microstructure, or whether a film or other layer is deposited on the first structural layer to provide more desirable optical properties/characteristics.
The sacrificial material that directly underlies the first structural layer used by the first aspect may actually be defined by the sequential deposition of multiple sacrificial layers, one on top of the other. That is, a lower portion of this sacrificial material may be formed as one layer, and an upper portion of this sacrificial material may be subsequently formed in overlying relation. Consider a case where a first sacrificial layer is formed over the first substrate, and where a first intermediate layer is formed on this first sacrificial layer. The first intermediate layer may be patterned to define a first subassembly (e.g., a plurality of strips). Portions of the first sacrificial layer are exposed by a patterning of the first intermediate layer to define the first subassembly. An upper portion of the first sacrificial layer (i.e., something less than the entirety of the first sacrificial layer) may be etched an amount after this patterning such that at least part of the first sacrificial layer that underlies at least part of the first subassembly is removed (e.g., using a timed etch). The first subassembly may be disposed directly on the first sacrificial layer, directly on a structural layer, or directly on both the first sacrificial layer and a structural layer (e.g., for the case where there is both a sacrificial material and a structural material at the same level within a stack which contains the microstructure being fabricated by the methodology of the subject first aspect).
The xe2x80x9cgapxe2x80x9d that now exists between the first subassembly and that portion of the etched first sacrificial layer that is directly beneath the first subassembly may be characterized as an undercut. A second sacrificial layer may be formed on at least the first sacrificial layer. One could characterize this as xe2x80x9cbackfilling.xe2x80x9d Notwithstanding this characterization of the backfilled sacrificial material as a xe2x80x9csecond sacrificial layerxe2x80x9d, the first and second sacrificial layers may in fact be indistinguishable from each other and may in effect define a continuous structure. Nonetheless, the sacrificial material that has been characterized as the second sacrificial layer will not fill the entire extent of each of the undercuts. This failure to fill the undercuts defines the plurality of etch release conduits that are associated with the first aspect of the present invention. One could visualize that the first subassembly acts as an umbrella of sorts that prevents the material that has been characterized as the second sacrificial layer from totally filling the noted undercuts that are protected by the first subassembly. Typically the second sacrificial layer will also cover the first subassembly. In this case and possibly in other instances during the fabrication of the microstructure associated with the first aspect, it may be desirable to planarize an upper surface of a given layer before depositing the next layer thereon. One appropriate technique for providing this planarization function is chemical mechanical polishing.
The first subassembly may be a reinforcing structure for the first structural layer, in which case the first subassembly would exist in the microstructure that is defined by the methodology of the first aspect. Reinforcement may be provided by structurally interconnecting the first structural layer with the first subassembly through the above-noted second sacrificial layer which may be deposited on the first subassembly in addition to the first sacrificial layer as noted. Further reinforcement of the first structural layer may be accomplished by structurally interconnecting the first subassembly with a structural layer that underlies the first sacrificial layer. In both cases, the actual reinforcement structure could be in the form of a plurality of posts or columns that are disposed in spaced relation, in the form of a plurality of at least generally laterally extending ribs or rails, or in the form of a grid-like reinforcement structure.
The first subassembly need not remain in the microstructure that may be defined by the methodology of the first aspect. That is, the first subassembly need not be part of the final microstructure that is ultimately fabricated by the methodology of the first aspect. In this case, the only purpose of the first subassembly would be to at least assist in the formation of the plurality of etch release conduits that are associated with the first aspect of the present invention. This xe2x80x9ctemporaryxe2x80x9d first subassembly may be in the form of a plurality of rails that are formed on or in a sacrificial material that is used in the methodology of the first aspect. Removal of the first subassembly from the final microstructure being made by the subject first aspect may be desirable in order to retain a low mass for this microstructure (e.g., in an upper structural layer of such a microstructure).
One way in which the first subassembly may be removed or alleviated from the final microstructure being made by the first aspect of the present invention is to form the first subassembly from a material that would be etched away along with the various sacrificial layers, although possibly at a different rate. Appropriate materials for the first subassembly in this case include silicon nitride, poly-silicon-germanium, or any other material that is soluble in the release etch or other etchant that will not have an adverse effect on any of the structural layers that may be included in the microstructure being made by the methodology of the subject first aspect. Having the first subassembly be of a reduced thickness may also contribute to the first subassembly being removed along with the sacrificial material within a desired time when releasing the microstructure made by the methodology of the first aspect. In one embodiment where the first subassembly is formed from silicon nitride and in the form of a plurality of strips, the first subassembly has a thickness or vertical extent of typically less than about 1,500 xc3x85 for this purpose.
Another option for creating the plurality of at least generally laterally extending etch release channels in accordance with the first aspect entails forming a first intermediate layer that will underlie the first sacrificial layer. This first intermediate layer may be patterned to define a plurality of at least generally laterally extending strips that are disposed in non-intersecting relation over at least a portion of their length. These strips are spaced relatively close to each other such that when the first sacrificial layer is deposited on the first intermediate layer, the sacrificial material is unable to entirely fill the space between the adjacent strips. More specifically, an upper portion of the space between adjacent strips will xe2x80x9cclose offxe2x80x9d during the deposition of the material that defines the first sacrificial layer before a lower portion of the space between the adjacent strips has had a chance to be filled with the material that defines the first sacrificial layer. Each xe2x80x9cunfilledxe2x80x9d void between adjacent pairs of strips defines one of the plurality of etch release channels referenced in relation to the first aspect. The manner in which the voids are formed may be characterized as xe2x80x9ckeyholing.xe2x80x9d Keyholing in relation to the first aspect is a result a relatively close spacing between adjacent strips in relation to their thickness or vertical extent. In one embodiment, a ratio of the height of these strips to the spacing between adjacent strips is at least about 1:1.
Further options exist for creating the plurality of at least generally laterally extending etch release channels in accordance with the first aspect. One way is to use multiple, different etchants. A first etchant that is not selective to the first sacrificial layer may be used to form the plurality of at least generally laterally extending etch release channels. A second, different etchant that is selective to the first sacrificial layer may thereafter be directed through the plurality of at least generally laterally extending etch release channels or conduits (again created/defined by the first etchant) to remove the first sacrificial layer. The first etchant may be selective to a material that forms a plurality of at least generally laterally extending etch release rails that are embedded or encased within the first sacrificial layer or at least in a sacrificial material. Any appropriate layout may be utilized for these plurality of at least generally laterally extending etch release rails, including a plurality of separate and discrete etch release rails, a network or grid of interconnected etch release rails, or some combination thereof.
The intermediate structure in the fabrication of the microstructure in accordance with the first aspect may be characterized as a stack, and includes the various layers that are sequentially deposited on the substrate, and thereafter possibly patterned. This stack includes an exterior surface that is opposite the first substrate. Access to at least one of the etch release rails in the above-noted two etchant example may be provided by a first runner that extends from this exterior surface of the stack and at least generally toward the first substrate to a level such that it may structurally interconnect with at least one of the plurality of etch release rails. The same material that defines the etch release rails may define this first runner, such that the first etchant will first remove the first runner, and then each etch release rail that is structurally interconnected therewith (either directly or indirectly). Multiple first runners may be provided for accessing the plurality of etch release rails, multiple etch release rails may be accessed by a single first runner, or some combination thereof.
A second aspect of the present invention is embodied in a method for making a microstructure in which a plurality of at least generally laterally extending etch release channels or conduits are formed within a sacrificial material that is used to build/assemble the microstructure on an appropriate substrate, but which is at least in part removed when the microstructure is released from this substrate. These etch release channels do not exist until the release of the microstructure is initiated in the second aspect. In this regard, the method of the second aspect includes forming a first intermediate layer on top of a first sacrificial layer or possibly on top of the substrate. This first intermediate layer is patterned to define a plurality of at least generally laterally extending first strips that sit on top of the first sacrificial layer. A second sacrificial layer is thereafter deposited on that portion of the first sacrificial layer which was exposed by the patterning of the first intermediate layer so as to be disposed at least alongside the first strips. Although not fundamentally required by the second aspect, the second sacrificial layer may also be disposed on top of the first strips as well. In any case, a first structural layer is formed on top of the second sacrificial layer. Both the first and second sacrificial layers are removed at least in part using an appropriate etchant. Generally, those portions of the second sacrificial layer that interface with or are disposed adjacent to the first strips etch at a greater rate than other portions of the second sacrificial layer which effectively defines a plurality of at least generally laterally extending etch release pipes, channels, conduits or the like. A plurality of hollow and at least generally laterally extending etch release channels or conduits (e.g., disposed at least generally parallel with an upper surface of the first substrate) are thereby formed in the second sacrificial layer by this differential etch rate. Although these etch release conduits will typically be disposed at a constant elevation relative to the substrate, such need not necessarily be the case. Ultimately, at least part of the second sacrificial layer, as well as the first sacrificial layer, are removed at least in part by allowing an etchant to flow through any and all of the noted conduits after the formation of the same in the releasing operation (and thereby encompassing the situation where all of the first and second sacrificial layers are removed, as well as the first intermediate layer if the same is not a structural material as discussed below).
Various refinements exist of the features noted in relation to the second aspect of the present invention. Further features may also be incorporated in the second aspect of the present invention as well. These refinements and additional features may exist individually or in any combination. The noted differential etch rate is believed to be based upon the density of that portion of the second sacrificial layer in proximity to the first strips being less than a density of the remainder of the second sacrificial layer, as well as a density of the first sacrificial layer as well for that matter. The differential density is due to the sticking characteristics of the depositing atoms or molecules, which depends on the characteristics of the deposition technique. For example, the density of add-on molecules in a plasma-enhanced chemical vapor deposition (PECVD) system depends on directional orientation of the surface to the plasma body. In this way, atoms or molecules striking the surface have different energy available to them to aid in their positioning in low-energy (i.e. high-density) positions on the surface.
In one embodiment of the second aspect, at least one end of at least one first strip may be disposed at least generally at the same radial position as a perimeter of the first structural layer. Since the first strips effectively define the etch release conduits, at least one end of at least one etch release conduit may be disposed at this same radial position as well. As such, the etchant does not have to etch in from the perimeter xe2x80x9ctoo farxe2x80x9d before encountering a region that will have a higher etch rate, and that again defines a corresponding etch release conduit. The parameters mentioned above in relation to the first aspect regarding this feature are equally applicable to this second aspect.
Various layouts of the plurality of first strips (and thereby the etch release conduits) in the noted lateral dimension may be utilized in accordance with the second aspect. In one embodiment, each of the plurality of at least generally laterally first strips are further disposed in non-intersecting relation, in another embodiment each of the plurality of first strips are disposed in at least substantially parallel relation, and in yet another embodiment at least some of the first strips intersect. The plurality of first strips may extend at least generally toward (and thereby including to) a common point, such as one that corresponds with a center of the first structural layer in the lateral dimension. All of the first strips need not extend the same distance toward this common point, although such may be the case. Some of the plurality of strips may extend at least generally toward (and thereby including to) a first common point (e.g., one that corresponds with a center of the first structural layer in the lateral dimension), while some of the plurality of first strips may extend toward a different common point. The plurality of first strips utilized by the second aspect may also extend in the lateral dimension in a variety of configurations. In one embodiment, the plurality of first strips are at least generally axially extending, while in another embodiment the plurality of first strips are non-linear (e.g., in a sinusoidal configuration within a plane that is parallel with the substrate).
One particularly desirable application for the second aspect is in the formation of a mirror microstructure or multiple mirror microstructures for a surface micromachined optical system that has at least some degree of movement relative to the first substrate. Because of the different etch rates that result from the way in which the microstructure is made by the methodology of the second aspect, there is no need to have a plurality of vertically disposed etch release apertures that extend down entirely through the second structural layer to release the mirror microstructure from the first substrate by the removal of the underlying first and second sacrificial layers. As such, the upper surface of the second structural layer retains a very smooth surface that lacks any such vertically disposed etch release apertures, which makes the microstructure that is made by the methodology of the second aspect particularly suited for use in optical applications. This is true whether the upper surface of the second structural layer is the actual optical surface for the mirror microstructure, or whether a film or other layer is deposited on the second structural layer to provide more desirable optical properties/characteristics.
Typically the second sacrificial layer will also cover the first strips (again, formed from the first intermediate layer) such that they are effectively embedded between the first and second sacrificial layers. In this case, it may be desirable to planarize an upper surface of the second sacrificial layer before depositing the first structural layer thereon. It may also be desirable to planarize an upper surface of other layers within the microstructure made in accordance with the methodology of the second aspect as well before depositing another layer thereon. One appropriate technique for executing this planarization function is chemical mechanical polishing.
The first strips may be a reinforcing structure for the first structural layer and would then exist in the microstructure that is made by the methodology of the second aspect. Reinforcement may be provided by structurally interconnecting the first structural layer with the first strips through the above-noted second sacrificial layer which may be deposited on the first strips in addition to the first sacrificial layer as noted. Further reinforcement of the first structural layer may be accomplished by structurally interconnecting the first strips with a structural layer that underlies the first sacrificial layer and thereby the first structural layer. In both cases, the actual reinforcing structure could be in the form of a plurality of posts or columns that are disposed in spaced relation, in the form of a plurality of at least generally laterally extending ribs or rails, or in the form of a grid-like reinforcement structure.
A third aspect of the present invention is embodied in a method for making a surface micromachined microstructure. A first sacrificial layer is formed over a first substrate in a manner so as to define a plurality of at least generally laterally extending low density regions therein. A first structural layer is thereafter formed over the first sacrificial layer. The release of the first structural layer from the first substrate is affected by removing the first sacrificial layer with an appropriate etchant. The etching rate within the low density regions of the first sacrificial layer is greater than in other regions of the first sacrificial layer.
Various refinements exist of the features noted in relation to the third aspect of the present invention. Further features may also be incorporated in the third aspect of the present invention as well. These refinements and additional features may exist individually or in any combination. The higher etch rate in the low density regions of the first sacrificial layer may define a plurality of at least generally laterally extending etch release pipes, channels, conduits, or the like, which in turn should reduce the time required to completely release the microstructure from the first substrate. Although the low density regions will typically be disposed at a constant elevation relative to the substrate, such need not be the case.
In one embodiment of the third aspect, at least one end of at least one low density region may be disposed at least generally at the same radial position as a perimeter of the first structural layer. Since the low density regions effectively define the etch release conduits, at least one end of at least one etch release conduit may be disposed at this same radial position as well. As such, the etchant does not have to etch in from the perimeter xe2x80x9ctoo farxe2x80x9d before encountering a low density region for definition of an etch release conduit(s). The parameters mentioned above in relation to the first aspect regarding this feature are equally applicable to this third aspect.
Various layouts of the plurality of low density regions, and thereby the etch release conduits, in the noted lateral dimension may be utilized in accordance with the third aspect. In one embodiment, each of the plurality of at least generally laterally extending low density regions are disposed in non-intersecting relation, in another embodiment each of the plurality of low density regions are disposed in at least substantially parallel relation, and in yet another embodiment at least some of the low density regions intersect. The plurality of low density regions may extend at least generally toward (and thereby including to) a common point, such as one that corresponds with a center of the first structural layer in the lateral dimension. All of the low density regions need not extend the same distance toward this common point, although such may be the case. Some of the plurality of low density regions may extend at least generally toward (and thereby including to) a first common point (e.g., one that corresponds with a center of the first structural layer in the lateral dimension), while some of the plurality of low density regions may extend toward a different common point. The plurality of low density regions utilized by the third aspect may also extend in the lateral dimension in a variety of configurations. In one embodiment, the plurality of low density regions are at least generally axially extending, while in another embodiment the plurality of low density regions are nonlinear (e.g., in a sinusoidal configuration within a plane that is at least generally parallel with the substrate).
One way in which the low density regions associated with the third aspect may be formed is by forming a second sacrificial layer over the first substrate, and then patterning the same to define a plurality of at least generally laterally extending etch release conduit apertures. Each of these etch release conduit apertures is defined by first and second sidewalls that are disposed in spaced relation to each other. The first sacrificial layer is formed such that the material of the first sacrificial layer is deposited within these etch release conduit apertures. The first sacrificial layer may be deposited on the top of the second sacrificial layer as well. In any case, the low density regions associated with the third aspect will thereby exist along the first and second sidewalls of each of the etch release conduit apertures.
One advantage of the above-noted method for defining the low density regions in accordance with the third aspect, and thereby for defining a plurality of etch release channels, is that a layout of the low density regions may define a network or grid-like structure or such that a plurality of these low density regions cross and/or are interconnected in some manner. For instance, the patterning of the second sacrificial layer could define a repeating pattern of interconnected xe2x80x9cdiamonds,xe2x80x9d a honeycomb or honeycomb-like structure, or the like. This ability to define a network could further enhance the distribution of the etchant during the release of the first structural layer from the first substrate. Another advantage of this particular method for defining the low density regions, and thereby for defining a plurality of etch release channels, is that the same does not require the use of any structural layer or material for the formation thereof. Therefore, this particular embodiment of the third aspect could be used to enhance the release of a simple, single structural layer in a microstructure.
The above-noted methodology for defining the low density regions in accordance with the third aspect may also be utilized where structural reinforcement of the first structural layer is desired. Structural reinforcement of the first structural layer may be realized by having an appropriate reinforcement structure cantilever downwardly from a lower surface of the first structural layer. Another way to structurally reinforce the first structural layer is to structurally interconnect the first structural layer with an underlying structural layer. The only limitation on the use of any such reinforcement structure is that it should not extend downwardly through any of the noted low density regions so as to cut off any etch release channels. This may be done in variety of manners. Consider the case where the second sacrificial layer is patterned in the form of a honeycomb. A plurality of columns or posts could extend downwardly from the first structural layer through the xe2x80x9cclosed cellxe2x80x9d portions of the honeycomb without intersecting with any of the low density regions which define the profile of the honeycomb (in plan view).
Notwithstanding the advantages of the above-noted method for forming the low density regions in accordance with the third aspect, these low density regions may also be defined in the manner discussed above in relation to the second aspect. Therefore, those features discussed above in relation to the second aspect may be used in this third aspect as well.
A fourth aspect of the present invention is embodied in a method for making a surface micromachined microstructure. A first sacrificial layer is formed over a first substrate. A first structural layer is formed over the first sacrificial layer. The release of the first structural layer from the first substrate is affected by what may be characterized as a two step etch. In this regard, a first etchant may be used to form a plurality of at least generally laterally extending etch release channels or conduits within the first sacrificial layer or so as to otherwise be embedded within a sacrificial material. A second, different etchant that is selective to the first sacrificial layer may thereafter be directed through the plurality of at least generally laterally extending etch release channels (again created/defined by the first etchant) to remove the first sacrificial layer.
Various refinements exist of the features noted in relation to the fourth aspect of the present invention. Further features may also be incorporated in the fourth aspect of the present invention as well. These refinements and additional features may exist individually or in any combination. The first etchant may be selective to a material that forms a plurality of at least generally laterally extending etch release rails that are embedded or encased within the first sacrificial layer or at least in a sacrificial material. Any appropriate layout may be utilized for these plurality of at least generally laterally extending etch release rails, including a plurality of separate and discrete etch release rails, a network or grid of interconnected etch release rails, or some combination thereof.
The intermediate structure in the fabrication of the microstructure in accordance with the fourth aspect may be characterized as a stack, and includes the various layers that are sequentially deposited on the substrate, and thereafter possibly patterned. This stack includes an exterior surface that is opposite the first substrate. Access to at least one of the noted etch release rails may be provided by a first runner that extends from this exterior surface of the stack and at least generally toward the substrate to a level such that it may interconnect with at least one of the plurality of etch release rails. The same material that defines the etch release rails may define this first runner, such that the first etchant will first remove the first runner, and then each etch release rail interconnected therewith. Multiple first runners may be provided for accessing the plurality of etch release rails, multiple etch release rails may be accessed by a single first runner, or some combination thereof.

Method for making a microstructure by surface micromachining


A new variety of shrub rose plant suitable for garden decoration, having flowers of white coloration.

This invention relates to a new and distinct variety of shrub Rose, Rosa L. The varietal denomination of the new variety is xe2x80x98Orawichkayxe2x80x99. It has as its seed parent the unpatented variety known as xe2x80x98DIComonoxe2x80x99 and as its pollen parent, an unnamed and unpatented cultivar of the species rose known as Rosa wichuriana. It is believed that botanically, the new variety would be classified as a hybrid species of Rosa wichuriana.
Among the features which distinguish the new variety from other presently available and known commercial rose cultivars are the following combination of characteristics: xe2x80x98Orawichkayxe2x80x99 bears small, pure white, single blooms with showy golden yellow stamens borne in large pyramidal clusters throughout the growing season.
The new variety is low, about xc2xd meter, and spreading, between about 1 to 1xc2xd meters and bears small, Dark Green, lustrous foliage that shows good resistance to Powdery Mildew, Blackspot and Rust.
Since the variety is, for all practical purposes, sterile, no deadheading is required and the vitality of the new variety that would normally go to producing seed apparently is spent in producing more bloom. The fact that the blooms have virtually no scent does not in any way detract from its value as a landscape cultivar. The new variety is a bushy, spreading plant, suitable for outdoor garden decoration.
Asexual reproduction of the new variety by budding as performed in Clackamas County, Oregon shows that the foregoing and other distinguishing characteristics come true to form and are established and transmitted through succeeding propagations. xe2x80x98Orawichkayxe2x80x99 may be asexually propagated by cuttings, budding, grafting, layering or tissue culture. Budding and grafting have been successful on the major propagation understocks; namely, Rosa multiflora, Rosa laxa, and Rosa canina, as well as the cultivar known as xe2x80x98Dr. Hueyxe2x80x99.
The new variety may be distinguished from its seed parent, xe2x80x98DICimonoxe2x80x99 by the following combination of characteristics: xe2x80x98DICimonoxe2x80x99 is a free blooming floribunda rose cultivar. The flowers of xe2x80x98DICimonoxe2x80x99 are salmon pink and are well formed with about 35 petals. The seed parent variety is upright and slightly spreading.
The new variety may be distinguished from its unnamed Rosa wichuriana pollen parent, by the following combination of characteristics: (Rosa wichuriana is a species rose indigenous to Northeastern Asia). The pollen parent is nearly prostrate with creeping branches and has few flowers which are small, single to semi-double White and borne in pryamidal corybs only once in early summer.

Shrub rose plant named xe2x80x98Orawichkayxe2x80x99


Structures and methods of fabricating of a floating gate non-volatile memory device. In a first example embodiment, We form a bottom tunnel layer comprised of a lower oxide tunnel layer and a upper hafnium oxide tunnel layer; a charge storage layer comprised of a tantalum oxide and a top blocking layer preferably comprised of a lower hafnium oxide storage layer and an upper oxide storage layer. We form a gate electrode over the top blocking layer. We pattern the layers to form a gate structure and form source/drain regions to complete the memory device. In a second example embodiment, we form a floating gate non-volatile memory device comprised of: a bottom tunnel layer comprised essentially of silicon oxide; a charge storage layer comprised of a tantalum oxide; a top blocking layer comprised essentially of silicon oxide; and a gate electrode. The embodiments also comprise anneals and nitridation steps.

1) Field of the Invention
This invention relates generally to the structure and fabrication of semiconductor devices and more particularly to the fabrication of a dielectric materials for memory devices.
2) Description of the Prior Art
A key issue for floating-gate nonvolatile semiconductor memories (NVMs) is the scaling of the tunneling oxide because the stress-induced leakage current (SILC) limits the tunnel oxide to ˜8 nm. This scaling issue is a formidable challenge especially for the emerging system-on-chip (SOC) integrated circuits designs in which programming voltage must be scaled for the NVMs to be compatible with the low voltage logic circuits. Therefore, silicon-oxide-nitride-oxide-silicon (SONOS) charge-trapping based NVM is replacing floating-gate NVM due to its advantages of lower programming voltage, smaller cell size and better endurance over the floating-gate devices. However, retention and erase speed remain as the major challenges for conventional SONOS devices as device and voltage further scale in the future.
The relevant technical developments in the literature can be are described below.
U.S. Pat. No. 6,803,275—Park, et al.—Oct. 12, 2004—NO fabrication process for reducing oxygen vacancy content in bottom oxide layer in flash memory devices.
U.S. Pat. No. 6,680,509—Wu, et al.—Nitride barrier layer for protection of ONO structure from top oxide loss in fabrication of SONOS flash memory.
U.S. Pat. No. 6,790,755—Jeon—Preparation of stack high-K gate dielectrics with nitrided layer.
Bunmi Adetutu, Jiankang Bu, Hsing Tseng, "A Novel Floating Trap NVSM".
US 20030194853 A1—Jeon, Joong—Preparation of stack high-K gate dielectrics with nitrided layer.
U.S. Pat. No. 6,764,898B1—En et al.—shows a SONOS device with High k layers.
US 20030219947—Shin, Yoo-Cheol—Memory device and fabrication method thereof.
U.S. Pat. No. 6,740,605B1—Shiraiwa et al. shows a SONOS like device.

Method for forming high-K charge storage device

Chartered Semiconductor Manufacturing, Ltd


Example methods and systems for controlling operation of a laser device are provided. A method may include receiving an output of a proximity sensor that is positioned adjacent to a laser device, and determining based on the output of the proximity sensor that an object is within a threshold distance to the laser device. The method may also include based on the laser device emitting laser pulses, providing, by a computing device, instructions to discontinue the emission of laser pulses by the laser device based on the object being within the threshold distance. The method may further include based on the laser device being inactive, providing, by the computing device, instructions to prevent the emission of laser pulses by the laser device based on the object being within the threshold distance.

Unless otherwise indicated herein, the materials described in this section are not prior art to the claims in this application and are not admitted to be prior art by inclusion in this section.
LIDAR (laser imaging detection and radar) sensors emit high power infrared light that can be harmful to human eyes. As light become spread by the sensor during a scanning of an environment, potential for damage or harm is present. Traditional mitigations for eye safety involve spreading the laser beam on a wide aperture or reducing optical power to bring peak intensity under a safe threshold. However, such techniques reduce a range of the sensor and can cause the sensor to be overly complex.
In some instances, LIDAR sensors may be operated in close proximity to humans. For example, autonomous vehicles use various computing systems to aid in the transport of passengers from one location to another, and such vehicles are typically equipped with various types of sensors to detect objects in the surroundings. An autonomous vehicle may include lasers, sonar, radar, cameras, and other devices which scan and record data from surroundings of the vehicle. Sensor data from one or more of these devices may be used to detect objects and their respective characteristics (position, shape, heading, speed, etc.). This detection and identification is useful for the safe operation of autonomous vehicle; however, such detection and identification may be harmful for anyone in close proximity to the laser devices.

Methods and systems for controlling operation of a laser device


A rotary impact tool includes a drive power source for producing rotational power, a drive shaft driven by the rotational power supplied from the drive power source, an output shaft operatively connected to the drive shaft for receiving the rotational power, an impact mechanism operatively couplable with the drive shaft. The rotary impact tool further includes a changeover unit for changing over an impact mode in which the impact mechanism is operated and a drill driver mode in which the rotational power produced by the drive power source is transferred to the output shaft without operating the impact mechanism and a multi-stage speed reduction mechanism for transferring the rotational power produced by the drive power source to the output shaft through the drive shaft at variable speeds in at least three speed modes including a low speed mode, a middle speed mode and a high speed mode.

Conventionally, there is known a multi-purpose rotary impact tool capable of changing over an impact mode in which bolts, nuts or screws are tightened by an impact mechanism having a hammer and an anvil and a drill driver mode in which drilling tasks such as pilot hole forming and screw tightening are performed while restraining the impact operation of the impact mechanism.
When drilling operations or other operations are carried out in the drill driver mode, it is necessary to reduce the operation speed to a value smaller than available in the impact mode in order to prevent occurrence of cracks or other trouble in a drill bit. In addition to the impact mechanism being restrained or released when changing over the respective modes, the speed reduction ratio is changed in each of the modes.
For example, Japanese Patent No. 3911905 (Patent Document 1) discloses a rotary impact tool that can be changed over between a low speed mode in which a planetary reduction mechanism operates and a high speed mode in which the planetary reduction mechanism does not operate. The high speed mode is used as an impact mode and the low speed mode as a drill driver mode.
Japanese Patent Laid-open Publication No. 2005-288682 (Patent Document 2) discloses a rotary impact tool in which a high speed mode can be changed between an impact mode and a drill driver mode depending on whether an impact mechanism is restrained or released. Thus, the drill driver mode can be changed between two different speed modes, i.e., a low speed mode for drilling purposes and a high speed mode for screw-tightening purposes.
However, the drill driver mode of the rotary impact tool disclosed in Patent Document 1 lies generally halfway between a high speed mode and a low speed mode available in a drill-driver-single-function rotary tool, such as an electric drill or the like. For that reason, the rotary impact tool disclosed in Patent Document 1 poses a problem in that the screw tightening speed thereof is slower than that available in the high speed mode of the single-function rotary tool. Another problem resides in that the rotary impact tool cannot perform an operation of drilling large-diameter holes as is available in the low speed mode of the single-function rotary tool.
With the rotary impact tool of Patent Document 2 in which the drill driver mode can be changed between two different speed modes, the performance in the low speed mode does not substantially differ from the performance in the low speed mode achieved by the rotary impact tool disclosed in Patent Document 1. Therefore, the rotary impact tool of Patent Document 2 cannot perform an operation of drilling large-diameter holes. Since the speed reduction ratio in the high speed drill driver mode is the same as that available in the impact mode, the rotary impact tool is apt to come into a locked state if the load thereof is increased during a heavy tightening operation or other operations. This makes it difficult to use the rotary impact tool.

Panasonic Electric Works Power Tools Co., Ltd.


A vehicle control apparatus and method use speech recognition and include: a passenger recognizing device configured to recognize passengers including a first passenger and at least one second passenger in a vehicle; a voice recognizing device configured to receive and to recognize a voice utterance by the first passenger or the at least one second passenger and to output a speech recognition result based on the received voice utterance; and a processor configured to additionally query the at least one second passenger or the first passenger based on the speech recognition result of the voice utterance of the first passenger or the at least one second passenger, respectively, to provide each of the first passenger and the at least one second passenger with a customized service.

With the development of speech recognition technology, speech recognition is being applied to vehicles to improve user convenience and driving concentration of the user. The speech recognition system in the vehicle recognizes a single voice query based on a driver utterance or speech, outputs a speech recognition result, and then performs a single action on the speech recognition result.
When there are two or more passengers in a vehicle, the conventional speech recognition system outputs the speech recognition result or performs an action (function) corresponding to the speech recognition result, based on the words uttered by one of the passengers.
In addition, when processing the speech recognition result and when a personal preference is set up, such as vehicle control, song search, or the like, the conventional speech recognition system may provide an incorrect service that passengers do not want.

Vehicle control apparatus and method using speech recognition


Systems for valve actuation in internal combustion engines provide configurations for hydraulic lash adjusters and valve actuation valvetrain components that are particularly suitable for prevention of HLA jacking in dedicated cam environments including Type II valvetrain architectures. In one implementation, a lash adjuster loading component, which may comprise a stroke-limited spring biased piston associated with the main event valvetrain keeps the lash adjuster under a constant compressive force to prevent jacking.

Internal combustion engines require valve actuation systems to control the flow of combustible components, typically fuel and air, to one or more combustion chambers during operation. Such systems control the motion and timing of intake and exhaust valves during engine operation. In a positive power mode, intake valves are opened to admit fuel and air into a cylinder for combustion and exhaust valves are subsequently opened to allow combustion products to escape the cylinder. This operation is typically called a "positive power" operation of the engine and the motions applied to the valves during positive power operation are typically called "main event" valve actuation motions. Auxiliary valve actuation motion, such as motion that results in engine braking (power absorbing), may be accomplished using "auxiliary" events imparted to one or more of the engine valves.
Valve movement during main event positive power modes of operation is typically controlled by one or more rotating cams as motion sources. Cam followers, push rods, rocker arms and other elements disposed in a valvetrain provide for direct transfer of motion from the cam surface to the valves. The use of a valve bridge may impart motion to plural valves from a single upstream valvetrain. For auxiliary events, "lost motion" devices may be utilized in the valvetrain to facilitate auxiliary event valve movement. Lost motion devices refer to a class of technical solutions in which valve motion is modified compared to the motion that would otherwise occur as a result of actuation by a respective cam surface alone. Lost motion devices may include devices whose length, rigidity or compressibility is varied and controlled in order to facilitate the selective occurrence of auxiliary events in addition to, or as an alternative to, main event operation of valves. Auxiliary events may also be facilitated by dedicated cam systems in which a separate auxiliary or braking cam and valvetrain may be used to impart auxiliary motion to one or more valves to facilitate the selective occurrence of auxiliary events.
Lash adjustment features are typically provided on valve actuation systems to facilitate the elimination of lash, which is excessive clearance between valvetrain components that can lead to excessive noise, vibration, impact forces and wear. For example, during braking events, substantial lash may be introduced into the engine valvetrain. Lash adjusters, which are typically hydraulic lash adjusters ("HLA's"), may include mechanical components that cooperate to expand under hydraulic pressure in a lash take-up mode during one portion of the valve cycle, typically when the valvetrain is under zero lift or unloaded, and then assume a hydraulically "locked" or incompressible mode during valve opening portion of the valve cycle, typically when the valvetrain is under high load, for example, during a main event actuation. One challenge related to the use of HLA's is the prevention of over-extension or "jacking" of the HLA, which may occur when the HLA is permitted to extend too far in the take-up mode and becomes hydraulically locked in the over-extended position. This can result in excessive valvetrain forces and other undesirable consequences. As such measures have been taken in the prior art to prevent jacking by maintaining suitable loads on the HLA or to limit HLA extension.
Lost motion cam systems typically use at least one cam with different profiled lift sections on the same cam lobe to impart motion for respective main event and one or more auxiliary events. These different profiled lift sections are activated or deactivated using a separate lost motion mechanism, such as a piston or actuator, located in the valvetrain. Example auxiliary events include engine braking, early exhaust valve opening (EEVO), or late intake valve closing (LIVC) lift events, and can be imparted to one or more valves in a valve set (i.e., two exhaust valves for a respective cylinder). Lost motion auxiliary valve lift systems, such as lost motion braking systems may employ a single rocker associated with the lost motion cam and a valve bridge associated with the rocker for actuating two engine valves in main event motion. Auxiliary valve lift or braking motion on one of the valves is facilitated by an auxiliary valve lift or braking actuator, which is a lost motion device that may be housed in the rocker and may selectively impart auxiliary or braking motion to the valve by way of a bridge pin disposed in the bridge and providing for independent motion relative thereto. The auxiliary valve lift or braking actuator is selectively activated and deactivated such that the auxiliary or braking event lift profile section or lobe on the lost motion cam only results in auxiliary or braking motion on the valve when an auxiliary event, such as engine braking is desired.
On the other hand, dedicated cam valve actuation systems may utilize a dedicated auxiliary motion source and dedicated auxiliary valvetrain components, at least some of which are separate from the main event motion source and valvetrain, to facilitate auxiliary events. U.S. Pat. No. 8,851,048 to Meistrick, for example, the subject matter of which is incorporated herein by reference in its entirety, describes a dedicated cam system in which main event motion is imparted to a valve bridge and ultimately to two engine valves cooperating therewith. Auxiliary motion of one of the engine valves may be facilitated by a dedicated auxiliary motion source (cam) which cooperates with an auxiliary rocker to transmit auxiliary motion through a bridge pin in the valve bridge, and ultimately to one engine valve to cause auxiliary events, such as braking events.
Dedicated cam valve actuation systems may include systems commonly known as "Type II" valvetrain architectures, as described in SAE Technical Paper 2007-01-1285, titled "Design and Development of a 2-Step Rocker Arm." These architectures may include a rocker arm that pivots about a fulcrum at one end, with an opposite end engaging a valve or valvetrain components cooperating with a valve. Main event motion may be imparted at a central or intermediate location on the rocker arm by a main event motion source, such as a main event cam. These systems may utilize lash adjusters. In Type II architectures, the lash adjuster may not be disposed directly in the main event load path but may instead serve as a reaction force to the main event load and be disposed, for example, in a position in which lash is adjusted by relative movement of the rocker arm pivot.
In engine environments where auxiliary motion is facilitated by a dedicated auxiliary motion source, such as a dedicated cam and rocker, or a bolt-on master/slave brake, which may be separate from the main event motion source, in the above-described Type II architectures and other environments, challenges in preventing lash adjuster over-extension may be presented.
It would therefore be advantageous to provide systems that address the aforementioned shortcoming and others in the prior art.

Lash adjuster control in engine valve actuation systems


A flexible cover plate is described that includes a base layer, a hard coating layer, on the base layer and a cover layer on a side of the hard coating layer away from the base layer. The cover layer is made of a linear organic polymer having a hydrogen bond crosslink network.

With the development of various display techniques, the requirements for various performance of a screen are increasing due to wide use of display devices. As flexible screens have bendable and rolling characteristics, it is possible to bend, fold, or roll the display device, so as to bring convenience of carrying and using the display device. Wearable display devices with flexible display panels are popular, show great potential in entertainment and other fields, and thus have been listed into the main competitive market in the industry.

Flexible cover plate, display module and display device

Beijing BOE Technology Development Co., Ltd.


A hybrid gas-electric turbine engine for turboprop or turboshaft applications is disclosed together with associated methods. In various embodiments disclosed herein, the turbine engine comprises a turbine configured to be driven by a flow of combustion gas; a turbine shaft configured to be driven by the turbine and transfer power to a load coupled to the turbine engine and an electric motor configured to transfer power to the load coupled to the turbine engine. The rotor may have a rotor axis of rotation that is radially offset from a shaft axis of rotation of the turbine shaft. In some embodiments, the electric motor may be a multi-rotor electric motor.

Hybrid (gas-electric) automobiles have become an alternative to automobiles that are powered exclusively by gasoline. The use of hybrid power plants in automobiles has been shown to provide operational advantages such as improved fuel economy, reduced noise and reduced emissions. However, hybrid power plants for propelling aircraft have not yet reached widespread use.


An improved process for producing near-alpha and alpha+beta titanium alloy axisymmetric components with high fatigue resistance which comprises the steps of:. (a) providing a beta processed near-alpha or alpha+beta titanium alloy component; PA1 (b) torque deforming the component; and PA1 (c) alpha+beta recrystallization annealing the resulting torque-deformed component.

This invention relates to the processing of rotating titanium alloy articles to improve the microstructure of such articles.
A wide range of titanium alloys are used in airframe and gas turbine engines for aerospace applications. Considerable research has been directed toward increasing strength and fatigue properties of critical titanium alloy parts, such as airframe and gas turbine compressor components.
Due to the nature of titanium transformation and alloying stabilization behavior, titanium grades can be grouped into three major classes, depending on the phase or phases present in their microstructures. These are alpha/near-alpha, alpha+beta, and near-beta/beta types.
Most titanium alloys currently used for high performance aerospace applications are alpha+beta (e.g., Ti-6Al-4V, a typical airframe alloy) and near-alpha (e.g., Ti-6Al-2Sn-4Zr-2Mo, a typical gas turbine engine compressor alloy) alloys. Commercial emphasis for the manufacture of these alloys has been largely placed on alpha+beta processing to assure adequate strength and ductility. Alpha+beta alloys are the most commonly used titanium alloys and are designed for intermediate strength and high fracture resistance in both airframe and engine applications. Near-alpha alloys possess excellent high temperature properties and are generally designed for high creep properties at high temperatures. Because of lack of toughness in the solution treated and aged condition and relatively poor hardenability, alpha+beta alloys have commonly been used in the annealed condition. As a result, the strength capability of titanium alloys cannot be effectively utilized.
Forging of near-alpha or alpha+beta titanium alloys is one of the most common methods for producing high integrity components for fatigue-critical airframe and gas turbine engine applications. Currently, forging of these classes of alloys is done at temperatures below the beta transus temperature of the alloys because the microstructures developed have a good combination of tensile and fatigue properties. On the other hand, forging near or above the beta transus temperature provides certain advantages in terms of reduced press load and much better shape definition, since the alloy plastic flow resistance is greatly reduced. Unfortunately, the microstructure developed as a result of such forging is a lenticular beta microstructure which is inferior in terms of fatigue performance.
Fatigue failures account for the majority of aircraft in-service component failure. Fatigue failure is divided into crack initiation and crack propagation stages.
In recent years, more and more rotating axisymmetric components are made of titanium alloys. This is due to the relatively low density of titanium which lowers the centrifugal and hoop stresses and subsequently reduces the bearing loads in rotating jet engines. At the same time, high frequency rotation exerts high levels of mechanical vibration, the result of system imbalance or interruption in air or gas flow. This leads to fatigue failure so common in these components.
It is known from titanium metallurgy that fine equiaxed structure, such as that developed during recrystallization treatment, is highly fatigue crack initiation resistant, while beta processed lenticular alpha structure, such as developed during beta extrusion, beta forging or beta anneal, is highly fatigue crack propagation resistant, but inferior in fatigue crack initiation resistance.
By locating fine equiaxed structure in potential crack initiation sites and lenticular beta processed structure in the crack propagation sites, it is possible to obtain components with superior fatigue resistance. It should be noted that in most components, fatigue cracks initiate at or close to the surface and propagate into the bulk of the material. To date, it has been necessary to resort to processing methods such as shot-peening to achieve such partitioned microstructure. Shot-peening of beta processed titanium alloy components has not been successful due to inherent surface cracking, the result of shear band deformation at the surface during the shot peening impact.
What is desired is a method for producing two different microstructural zones in one component or article in a relatively simple manner.
Accordingly, it is an object of the present invention to provide an improved process for producing near-alpha and alpha+beta titanium alloy axisymmetric components with high fatigue resistance.
Other objects, aspects and advantages of the present invention will become apparent to those skilled in the art from a reading of the following detailed description of the invention.

Method to produce fatigue resistant axisymmetric titanium alloy components

The United States of America as Represented by the Secretary of the Air Force


The certificate issued by a certificate authority used in authenticating a user terminal can be scrambled prior to being set to an access point. In one embodiment, the present invention includes a user terminal having a memory in which a user terminal certificate is stored. The user terminal also has a processor coupled to the memory to scramble the user terminal certificate using a shared secret to be known only by the user terminal and an access point of the wireless access network, and a transmitter coupled to the processor to send a message to the access point, the message including the scrambled user terminal certificate.

1. Field of the Invention
The present invention applies to the field of hardware authentication, in particular to terminal authentication in a wireless network.
2. Description of the Prior Art
Hardware authentication, also sometimes referred to as entity authentication, is the process of verifying a claimed or presumed identity. In the context of a wireless access network, hardware authentication is used to verify that a an entity is indeed the entity it is claiming to be. For example, a hardware authentication can verify that a terminal claiming to have a certain MAC address really has the claimed MAC address. Without hardware authentication, unauthorized user terminals could steal the resources of the wireless access network, and uplink and downlink communications between legitimate user terminals and access points may be intercepted and eavesdropped.
Hardware authentication in wireless networks is currently accomplished by time varying challenge-response protocols. In a typical challenge-response protocol a claimant proves its identity to a verifier by demonstrating knowledge of a secret known to be associated with the claimant.
One problem with challenge-response protocols is that the verifier needs access to a secure database to identify the secret the claimant should have. Furthermore, such protocols require several message exchanges and on-the-fly encryption that can slow down network access.
User terminals getting their sense of time from access points can cause another problem in some wireless access networks. The access point can get their time from wired networks, or the Global Positioning System. Before the terminal can authenticate the access point it may need a sense of time. However, the access point is not yet authenticated. Thus, its time reference cannot always be trusted.

Terminal identity masking in a wireless network


A method and an apparatus of scheduling in a multi-cell cooperative wireless communication system is provided. Scheduling is performed, and scheduling results are transmitted to a neighbor base station (BS). The scheduling results comprise certain information for scheduling to be sequentially performed among base stations. Inter-cell interference can be reduced and scheduling can be performed simply by exchanging signals without a central scheduler.

The next-generation multimedia wireless communication system, on which research is actively ongoing, is requested to process various information such as image data, radio data, and the like, beyond the early voice-oriented services, at a high data transmission rate.
Recently, orthogonal frequency division multiplexing (OFDM) supporting a high data transmission rate receives much attention. The OFDM is a multi-carrier modulation scheme in which a frequency band is divided into a plurality of orthogonal subcarriers to transmit data. Orthogonal frequency division multiple access (OFDMA) is a scheme providing multiplexing of multiple users by combining frequency division multiple access (FDMA), time division multiple access (TDMA), or code division multiple access (CDMA) to the OFDM.
A wireless communication system includes a base station (BS) and one or more mobile stations (MSs). MSs may be fixed or mobile, and may be referred to by other names such as user equipment (UE), user terminal (UT), subscriber station (SS), wireless device, etc. The BS generally refers to a fixed station that communicates with the MSs and may be called by other names such as node B, base transceiver system (BTS), access point (AP), etc. In the following description, uplink (UL) refers to transmission from the MSs to the BS, and downlink (DL) refers to transmission from the BS to the MSs.
The wireless communication system has a cell structure to configure an effective system. Cells refer to zones formed as a large area is divided in order to effectively use frequency. In general, a BS is installed in a central portion of a cell to relay MSs, and the cell refers to a service area provided by the single BS.
When neighboring cells in the OFDM/OFDMA system in a multi-cell environment use the same subcarrier, it potentially causes interference between users. This is called an inter-cell interference. In particular, the inter-cell interference is much problematic to an MS located near a cell boundary. In downlink, an MS located near the cell boundary is strongly affected by a neighboring cell. In uplink, an MS located near the cell boundary strongly affects a neighboring cell and has a low transmission rate due to a path loss in its serving cell.
In order to reduce the inter-cell interference, neighboring cells may use different sub-carriers, which, however, causes a problem in that radio resources used by the single BS are reduced.
Thus, in order to reduce the inter-cell interference in the multi-cell environment, a multi-cell cooperative method has been proposed. The use of the multi-cell cooperative method can improve a communication performance of the MS located near the cell boundary. In line with this, an effective scheduling method of a BS using the multi-cell cooperative method is required.

Method and apparatus of scheduling in multi-cell cooperative wireless communication system


The present invention relates to a tunable quadrature phase shifter comprising an input (IN) for inputting an input signal (vin), splitting means (10) for splitting the input signal into two essentially orthogonal first and second signals (i1, i2), adding means (6) for adding said first and second signals (i1, i2), subtracting means (7) for subtracting said first and second signals (i1, i2), a first output (OUT+) for outputting a first output signal (vo1) based on the output signal from said adding means (6), and a second output (OUTxe2x88x92) for outputting a second output signal (vo2) based on the output signal from said subtracting means (7), wherein that said splitting means (10) is provided as an all-pass.

The present invention relates to a tunable quadrature phase shifter comprising an input means for inputting an input signal, splitting means for splitting the input signal into two essentionaly orthogonal first and second signals, adding means for adding said first and second signals, subtracting means for subtracting said first and second signals, a first output for outputting a first output signal based on the output signal from said adding means, and a second output for outputting a second output signal based on the output signal from said subtracting means.
Such a phase shifter which provides two output signals in quadrature are used in e.g. mobile communication systems and other radio transmitter and receiver systems where an accurate 90 degrees phase shift is necessary to obtain a sufficient image rejection in the transmitter and to have a correct 90 degrees phase difference between the I (In-phase) and Q (Quadrature-phase) base band phase vector signals in the receiver. In particular, a possible application is the I/Q generation for RC/LC oscillators with large tuning range (xe2x80x9cSonetxe2x80x9d/xe2x80x9cSDHxe2x80x9d applications). Further, such a phase shifter is used in polyphase filters, QUAMs, Low IF/Zero IF receivers as well as Data and Clock Recovery (DCR) and Phase-Looked-Loop (PLL) circuits.
Among the first known techniques for quadrature signal generation is the RC-CR technique shown in FIG. 1. Here, an input signal vin is shifted by xe2x88x92xcfx80/4 to form a first output signal vo1 and by +xcfx80/4 to form a second output signal vo2. The phase difference between the output signals vo1 and vo2 is always xcfx80/2, but the amplitudes of the output signals vo1 and vo2 are equal at one frequency fo=1/(2xcfx80RC) only.
After shifting, limiting stages (not shown in FIG. 1) can be used, but amplitude limiting becomes difficult in the GHz range unless several stages are connected in cascade. This operation is possible in case only zero crossings of the signal are relevant. Nevertheless, there is always a mismatch in gain and amplitude between both the output signals vo1 and vo2 in the two parallel paths. Moreover, due to nonlinear effects, slew-rate (dvin/dt) like AM to PM conversion occurs. When the RC time constant varies with process and temperature, the cutoff frequency at which the amplitudes of both the output signals vo1 and vo2 are equal varies, too. Besides, the mismatch between passive components results also in a phase mismatch.
Another conventional method for quadrature generation is the Havens technique according to FIG. 2. The input signal is splitted into two branches by using a quadrature circuit 2 which has approximately quadrature outputs. The precision of this circuit is not mandatory. These two signals are:
v1(t)=A cos (xcfx89t)
v2(t)=A cos (xcfx89t+xcex8)xe2x80x83xe2x80x83(1).
After each of these two signals vo1 and vo2 is limited in amplitude by a limiter 4 and 5, respectively, these two signals are added by an adder 6 and also subtracted by a subtracter 7. Each of the signals from the outputs of the adder 6 and subtracter 7 are again limited in amplitude by limiters 8 and 9, respectively, to form the output signals vo1 and vo2. The interesting part comes from the fact that a phase imbalance from xcfx80/2 gives afterwards an amplitude mismatch between the two signals v1 and v2 cancelled away by the limiting action. This operation is explained below:                                                         v                                            xe2x80x83                                          1                        +                          v                                            xe2x80x83                                          2                                =                      2                        A                                      xe2x80x83                                                  cos                                            (                                  θ                  2                                )                                                                cos                                            (                                                      ω                                                              xe2x80x83                                                            t                                    +                                      θ                    2                                                  )
                                                            v                                            xe2x80x83                                          1                        -                          v                                            xe2x80x83                                          2                                =                      2                        A                                      xe2x80x83                                                  sin                                            (                                  θ                  2                                )                                                                sin                                            (                                                      ω                                                              xe2x80x83                                                            t                                    +                                      θ                    2                                                  )                                                                                (          2          )                .
The amplitudes A of the sum and difference signals are equal if the phase shifter has two outputs in quadrature (xcex8=xcfx80/2). Assuming that in the second signal v2 there is an amplitude mismatch of magnitude xcex5, the equation for the second signal v2 reads as follows:
v2=(A+xcex5) cos (xcfx89t+xcex8)xe2x80x83xe2x80x83(3).
The effect of such error is that v1+v2 rotates counterclockwise by "PHgr"1 and v1xe2x88x92v2 clockwise by "PHgr"2. In FIG. 3 the phasor diagram of the signals is shown. The two situations depicted correspond to the situation when no amplitude errors are present (FIG. 3a) and the situation when amplitude errors are present (FIG. 3b). From FIG. 3 one can find the phase errors "PHgr"1 and "PHgr"2 and the local phase error "PHgr"1+"PHgr"2 under the assumption that the amplitude error xcex5 is small when compared with the amplitude A, i.e. xcex5 less than  less than A.
The equations for the phase errors "PHgr"1 and "PHgr"2 are                                                         tan                                            (                                  Φ                                                        xe2x80x83                                                      1                                )                                      =                                          ϵ                                                  xe2x80x83                                                                  sin                                                        (                                          θ                      2                                        )                                                                                2                                    A                                                        xe2x80x83                                                                          cos                                                              (                                              θ                        2                                            )                                                                      +                                  ϵ                                                        xe2x80x83                                                                          cos                                                              (                                              θ                        2                                            )
                                          tan                                      (                              Φ                                                  xe2x80x83                                                2                            )                                =                                    ϵ                                            xe2x80x83                                                          cos                                                  (                                      θ                    2                                    )                                                                                2                                A                                                  xe2x80x83                                                                  sin                                                        (                                          θ                      2                                        )                                                              +                              ϵ                                                  xe2x80x83                                                                  sin                                                        (                                          θ                      2                                        )
                                  When                                xe2x80x83                              ϵ                                xe2x80x83                                           less than  less than             A                                          xe2x80x83                              the                                xe2x80x83                              result                                xe2x80x83                              is                                :                                                        (          4          )                .                                          Φ1          +          Φ2                ≅                  ϵ                      A                                      xe2x80x83                                                  sin                                            (                θ                )                                                                                (          5          )                .
The amplitude mismatch xcex5 leads to a phase mismatch. 1% amplitude mismatch generates 0.6xc2x0 in phase. Although this method is better in terms of robustness to errors, the disadvantage consists in the use of the four limiters 4, 5, 8 and 9 which convert amplitude modulation into phase modulation. Another critical disadvantage is that even some amplitude errors are tolerated, the input quadrature generator produces for different frequencies unequal amplitudes. Therefore, when the above described quadrature generation circuit is coupled to oscillators for I/Q processing by tuning the oscillator within an octave for example, the amplitude of the two paths drastically varies.
FIG. 2 shows the closest prior art from which the invention proceeds.
EP 0 707 379 A1 discloses a tunable quadrature phase shifter including two branches each constituted by cascade connection of a filter, an amplifier and a summing circuit, and two cross-connections constituted by amplifiers interconnecting the filter of one branch to the summing circuit of the opposite branch. An accurate 90xc2x0 phase shift between the two output signals is obtained by controlling the tail currents of the four amplifiers.
WO 92/11704 A1 describes a quadrature signal generator including a phase-locked loop configuration which comprises a voltage control phase-shift network, limiters, an exclusive-OR phase detector, a low phase filter, a differential voltage to current converter and a loop filter. The voltage controlled phase-shift network generates a phase shift for the differential quadrature signals. The exclusive-OR phase detector determines the phase error between the differential quadrature signals. The phase error is related to a voltage control signal which is coupled back to the voltage controlled phased-shift network to maintain a precise 90xc2x0 phase relationship between the differential quadrature signals.
Due to the control mechanism, both the devices according to EP 0 707 379 A1 and WO 92/11704 A1 require a complex and expensive construction.
Accordingly, it is an object of the present invention to provide a simple construction which avoids the amplitude mismatch and can be used for oscillators with more than one octave frequency tuning.
In order to achieve the above and other objects, according to the present invention, there is provided a tunable quadrature phase shifter comprising an input means for inputting an input signal, splitting means for splitting the input signal into two essentially orthogonal first and second signals, adding means for adding said first and second signals, subtracting means for subtracting said first and second signals, a first output for outputting a first output signal based on the output signal from said adding means, and a second output for outputting a second output signal based on the output signal from said subtracting means, characterized in that said splitting means is provided as an all-pass.
Since an all-pass produces two quadrature signals with equal amplitudes and the gm/C time constant of an all-pass tracks the oscillation frequency (using the same tuning mechanism) of the input signal outputted by the oscillator, the amplitude mismatch is well reduced. This further allows to avoid limiters at the input and also at the output. So, the present invention uses gm/C tuning schemes with inherent I/Q matching.
Preferably, a first output buffer means for buffering said first output signal and a second output buffer means for buffering said second output signal are provided.
A further preferred embodiment of the present invention comprises a first transimpedance converter having its input connected to said input means. A modification of this embodiment still comprises a second transimpedance converter having its output connected to said first output and a third transimpedance converter having its output connected to said second output. The provision of transimpedance converters is recommended in case the input and output signals are provided as voltage signals. Usually, the transimpedance converters are transimpedance amplifiers.
In accordance with a still further preferred embodiment of the present invention, the first and second output buffer means are provided as said first and second transimpedance converters, respectively, since the transimpedance converters have buffering functions, too.
A further preferred embodiment of the present invention is characterized by at least a first transistor with its collector connected to its base and its emitter coupled to a predetermined potential, a second transistor with its base connected to the base of said first transistor and its emitter coupled to said predetermined fixed potential, and a capacitor coupled between the junction of the bases of said first and second transistor and said predetermined potential.
In case the tunable quadrature phase shifter is provided as a differential phase shifter, further preferred embodiment is characterized by at least a first transistor with its collector connected to its base and its emitter coupled to a predetermined potential, a second transistor with its base connected to the base of said first transistor and its emitter coupled to said predetermined potential, a third transistor with its collector connected to its base and its emitter coupled to a predetermined potential, a fourth transistor with its base connected to the base of said third transistor and its collector coupled to said predetermined potential, and a capacitor coupled between a first junction of the bases of said first and second transistors and a second junction of the bases of said third and fourth transistors.
In both recently above mentioned embodiments, the transistors can be npn transistors and/or the predetermined potential is zero (ground).

Tunable quadrature phase shifter using an all-pass circuit


A magnetic recording and reproducing device according to an embodiment includes a magnetic recording medium and a controller. The magnetic recording medium includes in sequence a substrate, a storage layer, an exchange layer, and a surface recording layer. The controller executes following steps (1) to (6):                (1) magnetically recording first information on the surface recording layer;        (2) transferring the first information recorded on the surface recording layer to the storage layer;        (3) magnetically recording second information on the surface recording layer;        (4) magnetically reproducing the second information from the surface recording layer;        (5) transferring the first information recorded on the storage layer to the surface recording layer; and        (6) magnetically reproducing the first information transferred to the surface recording layer.

In recent years, thermally assisted magnetic recording (TAMR) and microwave assisted magnetic recording (MAMR) are studied for improving the recording density of hard disk drive (HDD). Any of them uses a granular magnetic recording medium in which fine magnetic grains are surrounded by a non-magnetic matrix. Typically 10-20 magnetic grains constitute a recording unit (reversed magnetic domain) as 1 bit. However, when the magnetic grains are made finer so as to make the reversed magnetic domain smaller, they cause a problem of large deviation in magnetic properties. On the other hand, decreasing the number of magnetic grains per 1 bit to make the reversed magnetic domain smaller has a problem of small signal to noise ratio (SNR). These problems make it difficult to increase the recording density by using TAMR and MAMR technologies.
A technique called three-dimensional recording or volume recording is studied to solve these problems. In the volume recording, the recording density per unit area is increased by recording information along the film thickness direction as well as in-plane direction of the magnetic recording medium. That is, information is also recorded in the additional layers under the topmost recording layer.
However, the volume recording method has following three problems when it is applied to a current HDD system.
The first problem is low recording resolution.
High density magnetic recording on the granular medium needs narrow magnetization transition region, which is an interface between two magnetic domains. Therefore, a recording magnetic field generated by a recording magnetic pole needs to be steeply decreased along down track direction (needs to have large magnetic field gradient).
Generally, the magnetic field gradient decreases with increasing a distance from the recording magnetic pole along the film thickness direction. Therefore, current HDD system is designed to have the recording layer as thin as possible and the flying height (distance between the recording head and the medium) as small as possible in order to make magnetic field gradient as large as possible. For the case of the conventional volume recording, high density recording can be achieved only on the topmost layer close to the recording magnetic pole, but is difficult on underlying layers far from the recording magnetic pole. The storage capacity of the whole magnetic recording medium can be increased to some extent but not by twice compare to the case of current single layer recording.
This problem can be solved to some extent by using a bit-patterned recording medium with multilayer structure. In the bit-patterned medium, the recording layer is etched into a magnetic dot having a size of 1 bit. Since it is not necessary to form the magnetization transition by the recording magnetic field, high density recording is achieved even in the underlying layers where the magnetic field gradient is not so large.
However, low magnetic field gradient increases the probability of accidental reversal of adjacent dots, and therefore the problem cannot be completely solved.
The second problem is low reproduction resolution.
In principle, a leakage magnetic field from each bit on the recording medium decreases in intensity with distance from the recording magnetic medium, and also the change in the magnetic field intensity on the magnetization transition region decreases with distance. In other words, a spatially blur reproduced signal is generated.
This phenomenon is a fundamental property as in the case of the recording magnetic field. Accordingly, current HDD system requires recording layer as thin as possible and the flying height as small as possible. Therefore, as in the case of the first problem, high density reproduction can be achieved only on the topmost layer close to the reproducing head for the current volume recording system.
This problem cannot be solved even using the bit-patterned medium. No matter how clearly the magnetization is spatially changed in underlying layers of the bit-patterned medium, it is recognized as a blur spatial magnetization change by the reproducing head far from it.
The third problem is a decrease in signal intensity due to the superimposing of multiple magnetization states.
Assume that a volume recording medium is composed of two layers (first layer and second layer) and a magnetization of the first layer is M1 and its thickness is t1, a magnetization of the second layer is M2 and its thickness is t2, and M1×t1≠M2×t2. When the combination of directions of the magnetizations of the first layer and the second layer are (up, up), (up, down), (down, up), (down, down), reproduced signal intensity is proportional to M1×t1+M2×t2, M1×t1−M2×t2, −M1×1+M2×t2, −M1×t1−M2×t2 respectively, and all of the cases can be distinguished by the amount of the reproduced signal in principle.
However, for the case of magnetized in different directions (the cases of M1×t1−M2×t2 and −M1×t1+M2×t2), the reproduced signal becomes lower than that in the case of conventional single layer recording. This means a decrease in SNR. High density recording is necessary just because the SNR in the conventional single layer recording reaches its lowest limit. High density recording technology that decreases SNR does not make sense. Furthermore, when the thickness of each layer is reduced to solve the aforementioned two problems (low recording resolution and low reproduction resolution), the problem of the low SNR becomes worse.

Magnetic recording and reproducing device and magnetic recording and reproducing method


A material fastener apparatus having one or more buttons which are attached to a first section of the material. The apparatus may have a layer of stretchable material which may be positioned under the first section of the material. The apparatus may also have one or more button holes which are attached to a second section of the material. The one or more button holes may be angled to the horizontal and are configured to receive the one or more buttons. The button holes may also be further configured to fasten the first section of the material with a second section of the material when the one or more buttons are buttoned with the one or more button holes.

Sections of material such as those used in clothing, home textiles, leather, knit or woven products etc. are normally fastened together using a button in conjunction with a button hole configuration. The buttons in these configurations are normally attached or sewn in position onto the material using rigid thread. This normally fixes the button in place with little or no movement. Movement may be required in order to insert the button into the button hole on another section of the clothing, home textiles, leather, knit or woven products products/material. However, this movement may be constrained by way of the rigid thread and as a result, users may have to pull on the button which ultimately would lead to a weakening of the attached thread. Pulling on the button may also lead to a loosening of the knot (which affixes the button in place) and the subsequent loss of the button, immediately or after continued use, as it falls off from the loosened knot. In addition, elderly or disabled individuals generally have difficulty grasping small objects including buttons, thereby making the buttoning process difficult. This problem may be further exacerbated by health conditions such as arthritis in which case fastening a button may result in pain for the arthritis sufferer.
In light of these problems, there exists a need for an apparatus designed to ease the fastening process for clothing, home textiles, leather, knit or woven products/material. There also exists a need for an apparatus that reduces or eliminates the pain normally suffered by disabled individuals when they are buttoning their garments or apparel.