Disclosed is a single mode optical waveguide having a core refractive index profile defined by upper and lower boundary profiles on a chart of relative index percent versus radius. The relative refractive index as a function of radial dimensions of the core are selected to provide an optical waveguide fiber having properties suitable for a high performance telecommunication system operating in the wavelength window of about 1530 nm to 1625 nm. Refractive index profile designs encompassing the wavelength window 1250 nm to 1350 nm are also disclosed. The embodiments of the core waveguide have exceptionally low total dispersion slope and attenuation over these wavelength windows.

The invention is directed to a single mode optical waveguide fiber, more particularly to a waveguide fiber in which the total dispersion is maintained at a low value over a selected wavelength range.
Because of the high data rates and the need for long regenerator spacing, the search for high performance optical waveguide fibers designed for long distance, high bit rate telecommunications has intensified. An additional requirement is that the waveguide fiber be compatible with optical amplifiers, which typically show an optimum gain curve in the wavelength range 1530 nm to 1570 nm. Consideration is also given to the potential of expanding the usable wavelength into the L-Band range of about 1570 nm to 1700 nm, more preferably in the range of about 1570 nm to 1625 nm. Another optical waveguide fiber operating wavelength range is the band that extends from about 1250 nm to 1350 nm. Although attenuation in this lower band is greater in comparison to the higher wavelength windows of operation, this lower wavelength band can provide additional information channels that significantly increase overall system capacity.
In cases where waveguide information capacity is increased by means of wavelength division multiplexing (WDM) technology, an additional waveguide fiber property becomes important. For WDM, high bit rate systems, the waveguide should have exceptionally low, but non-zero, total dispersion over the wavelength range of operation, thereby limiting the non-linear dispersion effect of four wave mixing.
Another non-linear effect that can produce unacceptable dispersion in systems having a high power density, i.e., a high power per unit area, is self phase modulation. Self phase modulation may be controlled by designing a waveguide core which has a large effective area, thereby reducing the power density. An alternative approach is to control the sign of the total dispersion of the waveguide so that the total dispersion of the waveguide serves to counteract the dispersion effect of self phase modulation.
A waveguide having a positive dispersion, where positive means shorter wavelength signals travel at higher speed than those of longer wavelength, will produce a dispersion effect opposite that of self phase modulation, thereby substantially eliminating self phase modulation dispersion.
Such a waveguide fiber is disclosed and described in U.S. patent application Ser. No.08/559,954, incorporated herein in its entirety by reference. The present novel profile improves upon the Ser. No.08/559,954 fiber by increasing effective area. In addition the waveguide of this disclosure has a total dispersion over the wavelength window of operation that is everywhere positive and has a lower limit greater than about 2.0 ps/nm-km to further reduce the power penalty due to four wave mixing.
Thus there is a need for an optical waveguide fiber which:
is single mode over at least the wavelength range 1530 nm to 1570 nm, and preferably over a range that extends to the lower wavelength 1250 nm;
has a zero dispersion wavelength outside the range 1530 nm to 1570 nm;
has a positive total dispersion over the wavelength range 1530 nm to 1625 nm which is not less than about 2.0 ps/nm-km;
has low attenuation, less than about 0.25 dB/km, over the range of about 1570 nm to 1625 nm; and
retains the usual high performance waveguide characteristics such as high strength and acceptable resistance to bend induced loss.
The concept of adding structure to the waveguide fiber core by means of core segments, having distinct profiles to provide flexibility in waveguide fiber design, is described fully in U.S. Pat. No. 4,715,679, Bhagavatula. The segmented core concept can be used to achieve unusual combinations of waveguide fiber properties, such as those described herein.
Definitions
The following definitions are in accord with common usage in the art.
The refractive index profile is the relationship between refractive index and waveguide fiber radius. The core refractive index profiles of the invention are described in terms of upper and lower profile boundaries. In addition particular embodiments are described in terms of the relative index xcex94(r)% (defined below) value at a number of radius points. The points chosen fully describe the refractive index profile in each case.
The radii descriptive of the index profiles disclosed herein appear in the drawings.
The effective area is,
Aeff=2xcfx80(∫E2r dr)2/(∫E4r dr),
where the integration limits are 0 to ∞, and E is the electric field associated with the propagated light. An effective diameter, Deff, may be defined as,
Aeff=xcfx80(Deff/2)2.
The initials WDM represent wavelength division multiplexing.
The initials SPM represent self phase modulation, a non-linear optical phenomenon wherein a signal having a power density above a specific power level will travel at a different speed in the waveguide relative to a signal below that power density. SPM causes signal dispersion comparable to that of linear dispersion having a negative sign.
The initials FWM represent four wave mixing, the phenomenon wherein two or more signals in a waveguide interfere to produce signals of different frequencies.
The term, xcex94%, represents a relative measure of refractive index defined by the equation,
xe2x80x83xcex94%=100xc3x97(ni2xe2x88x92nc2)/2ni2,
where ni is the maximum refractive index in region i, unless otherwise specified, and nc is the average refractive index of the cladding region unless otherwise specified.
The term xcex1-profile refers to a refractive index profile, expressed in terms of xcex94(b) %, where b is radius, which follows the equation,
xcex94(b)%=xcex94(bo)(1xe2x88x92[|bxe2x88x92bo|/(b1bo)]xcex1),
where bo is the maximum point of the profile and b1 is the point at which A(b)% is zero and b is in the range bixe2x89xa6b xe2x89xa6bf, where xcex94% is defined above, bi is the initial point of the xcex1-profile, bf is the final point of the xcex1-profile, and xcex1 is an exponent which is a real number.
In a computer model of the profile, in order to bring about a smooth joining of the xcex1-profile with the profile of the adjacent profile segment, the equation is rewritten as;
xcex94(b)%=xcex94(ba)+[xcex94(bo)xe2x88x92xcex94(ba)]{(1xe2x88x92[|bxe2x88x92bo|/(b1xe2x88x92bo)]xcex1},
where ba is the first point of the adjacent segment.
The pin array bend test is used to compare relative resistance of waveguide fibers to bending. To perform this test, attenuation loss is measured when the waveguide fiber is arranged such that no induced bending loss occurs. This waveguide fiber is then woven about the pin array and attenuation again measured. The loss induced by bending is the difference between the two attenuation measurements. The pin array is a set of ten cylindrical pins arranged in a single row and held in a fixed vertical position on a flat surface. The pin spacing is 5 mm, center to center. The pin diameter is 0.67 mm. The waveguide fiber is caused to pass on opposite sides of adjacent pins. During testing, the waveguide fiber is placed under a tension just sufficient to make the waveguide conform to a portion of the periphery of the pins.
Another bend test referenced herein is the lateral load test. In this test a prescribed length of waveguide fiber is placed between two flat plates. A #70 wire mesh is attached to one of the plates. (The market code #70 mesh is descriptive of screen made of wire having a diameter of 0.178 mm. The screen openings are squares of side length 0.185 mm.) A known length of waveguide fiber is sandwiched between the plates and a reference attenuation is measured while the plates are pressed together with a force of 30 newtons. A 70 newton force is then applied to the plates and the increase in attenuation in dB/m is measured. This increase in attenuation is the lateral load attenuation of the waveguide.
The low attenuation, large effective area waveguide fiber disclosed and described herein meets the requirements listed above and, in addition, lends itself to reproducible manufacture. The fiber usually is configured to propagate a single mode over the wavelength range of about 1530 nm to 1625 nm. Index profiles designs for use around the 1310 wavelength window are also disclosed. However the invention includes configuration of core and clad refractive index profiles that propagate more than one mode over all or part of the operating wavelength range. In the case in which more than one mode is propagated, all but the lowest order mode is strongly attenuated in the fiber. Thus the higher order modes disappear within a distance less than 1 km of fiber. Thus, in terms of typical transmission distances, the fiber effectively propagates only a single mode.
A first aspect of the invention is an optical waveguide fiber having a core region and a surrounding clad layer. The clad layer is in contact with the outside surface of the core region. The core region and clad layer are each characterized by respective refractive index profiles. That is, a value of relative index xcex94(r) % is defined for each radius point of the core region and clad layer. In the case of the core region, the radius points are in the range zero, at the core centerline, to ro, the radius drawn from the centerline to the interface of the core region and clad layer. At the centerline, the zero radius point, xcex94(r)%=xcex94o% is in the range of 0.25% to 1%. The core to clad interface radius, ro, is in the range 5.8 xcexcm to 18 xcexcm. The value of xcex94(r)% at the interface radius is zero. At radius points between the centerline and the interface, the relative index is bounded by an upper and a lower refractive index profile curve. The boundary profiles are selected so that the effective area of the waveguide is greater than or equal to 80 xcexcm2 and has attenuation less than 0.20 dB/km, where both of these values are taken at a wavelength of 1550 nm.
In a first embodiment of this aspect of the invention, the respective upper and lower boundary profiles are given as curves AB and CD in FIG. 3.
In a second embodiment of the invention, the respective upper and lower boundary profiles are given as curves EF and GH in FIG. 4.
The properties of waveguide fibers made in accord with the embodiments of the first aspect of the invention are set forth in Tables 1 and 2 below.
In a second aspect of the invention, the refractive index profile of the core region is described in terms of specific values of xcex94(r)% at a sufficient number of points to fully describe the core region profile. In particular, the xcex94(r)% on centerline is in the range 0.8% to 0.9%. The profile shape of core region is an xcex1-profile with xcex1=1 over the radius range zero to 1+/xe2x88x920.2 xcexcm. The final point of xcex1-profile has a relative index percent in the range 0.35% to 0.41 %. The remainder of the core region refractive index profile is a straight line joining the last point of the xcex1-profile and the core to clad interface point ro on the horizontal axis. The distance from centerline to core to clad interface is in the range 9 xcexcm to 10 xcexcm. Waveguide fibers made in accord with this aspect are predicted to have dispersion slope at 1550 nm in the range 0.065 ps/nm 2-km to 0.067 ps/nm2-km, effective area at 1550 nm in the range 100 xcexcm2 to 105 xcexcm2, and attenuation at 1550 nm in the range 0.182 dB/km to 0.186 dB/km.
A third aspect of the invention is a waveguide fiber having a relative index percent on centerline in the range 0.6% to 0.7%. The radius from the core region centerline to the core to clad interface is in the range 11.5 xcexcm to 12.5 xcexcm. The profile shape is defined by specifying points on the chart of relative refractive index percent versus radius xcex94(r)% versus r. In particular, xcex94(r)% is defined over the radius range 0xe2x89xa6rxe2x89xa65+/xe2x88x920.2 xcexcm by the respective values, xcex94(r)% at r=1+/xe2x88x920.1 xcexcm in the range 0.48% to 0.5%, xcex94(r)% at r=2+/xe2x88x920.1 xcexcm in the range 0.35% to 0.37%, xcex94(r)% at r=3+/xe2x88x920.1 xcexcm in the range 0.24% to 0.26%, xcex94(r)% at r=4+/xe2x88x920.1 xcexcm in the range 0.14% to 0.16%, and xcex94(r)% at r=5+/xe2x88x920.1 xcexcm in the range 0.05 % to 0.08%. The relative index profile is formed by connecting adjacent points by straight lines. For the remainder of the profile, xcex94(r)% is a rounded step index profile in the radius range of 5+/xe2x88x920.1 xcexcmxe2x89xa6rxe2x89xa6ro, and xcex94(r)% at r=5+/xe2x88x920.1 xcexcm is in the range 0.05 % to 0.08%. As is stated above, the relative index percent at the ro point is zero unless stated otherwise. Waveguide fibers made in accord with this aspect of the invention are predicted to have total dispersion slope at 1550 nm in the range 0.066 ps/nm2-km to 0.068 ps/nm2-km, effective area at 1550 nm in the range 80 xcexcm2 to 85 xcexcm2, and attenuation at 1550 nm in the range 0.186 dB/km to 0.190 dB/km.
A fourth aspect of the invention is a waveguide fiber having a relative index percent on centerline in the range 0.40% to 1.05%. The radius from the core region centerline to the core to clad interface is in the range 5.3 xcexcm to 7 xcexcm. The remaining points of the profile, xcex94(r)% for 0 less than r less than ro, are less than or equal to an upper boundary curve JK and greater than or equal to a lower boundary curve LM shown in FIG. 5. The upper and lower boundary curves are selected to provide, at 1310 nm, an effective area greater than or equal to 80 xcexcm2 and an attenuation less than 0.335 dB/km and an attenuation at 1550 nm less than 0.25 dB/km. The attenuation at 1550 nm is preferably less than 0.22 dB/km, and more preferably less than 0.20 dB/km.
The profile shape of this aspect is defined by specifying points on the chart of relative refractive index percent versus radius, i.e., xcex94(r)% versus r. In particular, xcex94(r)% is defined over the radius range 0xe2x89xa6rxe2x89xa66+/xe2x88x920.2 xcexcm by the following values. xcex94(r)% at r=1+/xe2x88x920.2 xcexcm is in the range 0.30% to 0.40%, and the profile shape over the radius range 0 to 1+/xe2x88x920.2 xcexcm is an xcex1-profile having an xcex1 of in the range of 0.8 to 1.2. xcex94(r)% is in the range 0.23% to 0.33% at radius 4+/xe2x88x920.2 xcexcm. xcex94(r)% is a straight line in the radius range of 4+/xe2x88x920.2 xcexcmxe2x89xa6rxe2x89xa65+/xe2x88x920.2 xcexcm and A(r)% is in the range 0.05% to 0.15% at radius 5+/xe2x88x920.2 xcexcm. xcex94(r)% is a straight line in the radius range of 5+/xe2x88x920.2 xcexcmxe2x89xa6rxe2x89xa66+/xe2x88x920.2 xcexcm, and, xcex94(r)% is zero at radius 6+/xe2x88x920.2 xcexcm.
A fifth aspect of the invention is a waveguide fiber preform having a core region and a clad layer, each having respective refractive index profiles. A waveguide fiber is drawn from the preform. The preform refractive index profiles are selected to produce a waveguide having structure and properties in accord with any of the aspects and embodiments set forth above and claimed in any one of claims 1 through 23. The waveguide fiber dimensions scale linearly with the dimensions of the draw preform, so that the geometry of a particular size preform may be readily determined by multiplying the waveguide fiber dimensions by an appropriate constant. This constant depends upon the pre-selected outside diameter of the desired preform.


Systems and methods for viewing, storing, transmitting, searching, and editing application-specific audiovisual content (or other unstructured data) are disclosed in which edge devices generate content on the fly from a partial set of instructions rather than merely accessing the content in its final or near-final form. An image processing architecture may include a generative model that may be a deep learning model. The generative model may include a latent space comprising a plurality of latent codes and a trained generator mapping. The trained generator mapping may convert points in the latent space to uncompressed data points, which in the case of audiovisual content may be generated image frames. The generative model may be capable of closely approximating (up to noise or perceptual error) most or all potential data points in the relevant compression application, which in the case of audiovisual content may be source images.

Traditional compression algorithms encode a data source using fewer bits than the original representation. These algorithms are either lossless or lossy, depending on whether they do or do not reproduce the original data source without any loss of information. Lossy compression is particularly useful for visual and audio data, since what matters is often the human perception of the quality of the reproduced data, as opposed to an identical bitwise reproduction. Lossy compression works by eliminating both statistical redundancy and nonessential details. Lossless compression algorithms are often used in conjunction with lossy ones to improve compression rates. The algorithms that encode and decode the compressed signal are referred to as the encoder and decoder, the pair is called a codec.
A widely used tactic for lossy codecs for audio and visual data is a transform coding, where a transformation is applied to the original signal so that it is now re-expressed as a sum of discrete or quantized components. This re-expression is constructed so that, although all components are needed to fully reconstruct the original signal, most of the perceptually relevant information is in a smaller proportion of the components. These relevant components can then be used to reconstruct a non-identical, but perceptually similar copy of the original.
There are some key shortcomings to existing, commonly used lossy compression algorithms including being unable to take advantage of conditional distributions (i.e., the use of mathematical transforms that are agnostic to the content of the data), manual feature (statistical regularities) selection, and limited readability and malleability of compressed content, to name but a few.

Systems and methods for searching audiovisual data using latent codes from generative networks and models


Aspects of the present disclosure relate to systems and methods for active depth sensing. An example apparatus configured to perform active depth sensing includes a projector. The projector is configured to emit a first distribution of light during a first time and emit a second distribution of light different from the first distribution of light during a second time. A set of final depth values of one or more objects in a scene is based on one or more reflections of the first distribution of light and one or more reflections of the second distribution of light. The projector may include a laser array, and the apparatus may be configured to switch between a first plurality of lasers of the laser array to emit light during the first time and a second plurality of laser to emit light during the second time.

For active depth sensing, a device may include a projector to emit a distribution of light, for which reflections of the distribution of light are sensed and measured to determine distances of objects in a scene. For example, a device may include a light projector that projects a distribution of infrared (IR) light (such as a distribution of IR light points) onto a scene. An active light receiver receives reflections of the IR light during a frame capture, and the device determines depths or distances of objects in the scene based on the received reflections.

Alternating light distributions for active depth sensing


In some embodiments, a frequency dependent gain circuit is coupled to an output of an amplifier. The gain circuit provides at least two ranges of frequency dependent gain characteristics in response to the output of the amplifier. A control circuit provides one of the at feast two gain values as an output. Other embodiments are described and claimed.

Point-to-point interconnects between two ICs (Integrated Circuits) or ASICs (Application Specific Integrated Circuits) are becoming a widely accepted bus technology for high speed data transfer applications. The signaling scheme for such links can be single-ended or differential. Inter-symbol interference (ISI) due to the interconnect frequency dependent insertion loss characteristics becomes an even larger problem with current printed circuit board (PCB) technology. ISI is one of the primary bottlenecks in implementation of point-to-point high speed interconnection technology.
Various on-die receiver equalization techniques can be used to reduce the inter-symbol interference (ISI) generated by the frequency dependent loss characteristics of PCB traces. Some known receiver equalization techniques include equalization schemes with a digital filter and equalization schemes with an active linear filter.
Receiver equalization techniques using a digital filter use an appropriate active digital FIR filter (finite impulse response filter) or an IIR filter (infinite impulse response filter) at the receiver end to cancel out the frequency dependent loss characteristics. One example of such a digital filter is an adaptive-tapped-delay-line-filter implemented at the receiver end. Digital filter receiver equalization techniques at the receiver end are advantageous, but difficult to implement in silicon. Digital filter receiver equalization circuits using FIR or IIR filters dissipate a lot of power. The coefficient of such a digital adaptive filter can be determined using a suitable training sequence and a high order filter scheme is possible, but implementation is extremely complex. It is difficult to obtain gain during implementation of this stage due to limited available voltage headroom.
Equalization schemes with an active linear filter is easy to implement and circuits using these schemes are able to dissipate power appropriately. Additionally, interconnects with a large loss can be equalized. This can lead to use of longer length interconnects. However, active filters are typically implemented using gm-c circuit elements, which have limited bandwidth.

Apparatus, system and method for receiver equalization


A semiconductor device according to the present invention includes: a semiconductor layer made of silicon; a trench formed by digging in from a top surface of the semiconductor layer; a gate insulating film formed on an inner wall surface of the trench and made of silicon oxide; a gate electrode embedded in the trench via the gate insulating film and made of a polysilicon doped with an impurity; and an oxidation-resistant metal film disposed on a top surface of the gate electrode and covering the top surface.

1. Field of the Invention
The present invention relates to a semiconductor device, having a vertical double diffused metal oxide semiconductor transistor having a trench gate structure, and a method for manufacturing the same.
2. Description of Related Art
A trench gate structure is generally known as an effective structure for refining a vertical double diffused metal oxide semiconductor field effect transistor (VDMOSFET).
FIG. 5 is a schematic sectional view of a conventional semiconductor device including a trench gate VDMOSFET.
A semiconductor device 101 includes an N+ (high concentration N) substrate 102. An N− (low concentration N) epitaxial layer 103 is laminated onto the N+ substrate 102. A base layer portion of the N− epitaxial layer 103 is an N− region 104, and at a top layer portion of the N− epitaxial layer 103, a P− body region 105 is formed vertically adjacent to the N− region 104.
A trench 106 is formed by digging in from a top surface of the N− epitaxial layer 103. The trench 106 penetrates through the P− body region 105, and a deepest portion thereof reaches the N− region 104. Inside the trench 106, a gate insulating film 107 made of SiO2 (silicon oxide) is formed so as to cover an inner surface thereof. A gate electrode 108 made of a polysilicon (doped polysilicon) doped with a high concentration of an N impurity is embedded at an inner side of the gate insulating film 107.
On top layer portions of the P− body region 105, N+ source regions 109 are formed along the trench 106. Further, on top layer portions of the P− body region 105, P+ body contact regions 110 are formed so as to penetrate through the N+ source regions 109.
An interlayer insulating film 113 is laminated onto the N− epitaxial layer 103. A gate wiring 114 is formed on the interlayer insulating film 113. The gate wiring 114 is contacted (electrically connected) to the gate electrode 108 via a contact hole 115 formed in the interlayer insulating film 113. A source wiring 116 is electrically connected to the N+ source regions 109 and the body contact regions 110 via contact holes (not shown) formed in the interlayer insulating film 113.
A drain electrode 117 is formed on a rear surface of the N+ substrate 102.
In a process of manufacturing the semiconductor device 101, a silicon oxide film is formed on the top surface of the N− epitaxial layer 103, including the inner surface of the trench 106, and a deposition layer of the doped polysilicon is formed on the silicon oxide film. The doped polysilicon deposition layer fills the interior of the trench 106 completely and is formed to a thickness covering the silicon oxide film outside the trench 106. Thereafter, by etch back, the portion of the doped polysilicon deposition layer present outside the trench 106 is removed, and the gate electrode 108 made of the doped polysilicon is formed inside the trench 106.
After the gate electrode 108 is thus formed, a cleaning process for cleaning the top surface of the N− epitaxial layer 103 is performed before ion implantation for forming the N+ source regions 109. In this cleaning process, first, HF (hydrofluoric acid) is supplied to the silicon oxide film exposed by etch back of the doped polysilicon, and the portion of the silicon oxide film outside the trench 106 is removed. Then, by a thermal oxidation process, a sacrificial oxide film is formed on a top surface of the gate electrode 108 and the top surface of the N− epitaxial layer 103. HF is then supplied to the sacrificial oxide film, and the sacrificial oxide film is removed by the HF.
After the cleaning process, the N+ source regions 109 and the body contact regions 110 are formed. Thereafter, by a CVD method, the interlayer insulating film 113 of a predetermined thickness is formed on the N− epitaxial layer 103. The contact hole 115 is then formed in the interlayer insulating film 113 by photolithography and etching.
However, the doped polysilicon is more readily oxidized (for example, is about three times in oxidation rate) compared to silicon that is not doped with an impurity. Thus, in the cleaning process, the sacrificial oxide film that is thicker than the oxide film formed on the top surface of the N− epitaxial layer 103 is formed on the top surface of the gate electrode 108. Thus, after removal of the sacrificial oxide film, the top surface of the gate electrode 108 becomes lower than the top surface of the N− epitaxial layer 103. That is, in the cleaning process, the gate electrode 108 develops a greater film thickness loss than the N− epitaxial layer 103.
Such film thickness loss of the gate electrode 108 causes variation of height (depth) among gate electrodes 108 (among a plurality of gate electrodes 108 formed on the semiconductor device 101 and/or among respective gate electrodes 108 of a plurality of semiconductor devices 101). Variation of height among gate electrodes 108 may cause variation of transistor characteristics. Further, when the top surface of the gate electrode 108 becomes excessively lower than the top surfaces of the N+ source regions 109 (N− epitaxial layer 103), desired transistor characteristics may not be exhibited.
Still further, when the top surface of the gate electrode 108 becomes lower than the top surface of the N− epitaxial layer 103, the interlayer insulating film 113 partially increases in thickness on the gate electrode 108. Thus, when the contact hole 115 for contact with the gate electrode 108 and the contact holes for contact with the N+ source regions 109 are formed simultaneously in the interlayer insulating film 113, the contact hole 115 may not penetrate through the interlayer insulating film 113 as shown in FIG. 5 and a contact failure may be caused between the gate electrode 108 and the gate wiring 114.
Yet further, during forming of the gate electrode 108, the doped polysilicon deposition layer grows from the top surface of the N− epitaxial layer 103 including the inner surface of the trench 106. On the surface of the doped polysilicon deposition layer, a recess recessed toward the trench 106 is thus formed at a position opposing to the trench 106. As etch back of the doped polysilicon deposition layer progresses, the recess in the top surface of the doped silicon deposition layer increases, and a recess is finally left in the top surface of the gate electrode 108. Due to both the recess and the film thickness loss of the gate electrode 108 during the cleaning process, when the thickness of the portion of the interlayer insulating film 113 on the gate electrode 108 increases more, it is more likely to cause a contact failure between the gate electrode 108 and the gate wiring 114.

Semiconductor device and method for manufacturing the same


A preparation method of silver nanostructure for use as substrate of surface-enhanced Raman scattering (SERS), which can ensure the ‘hot spot’, which provides the considerably very intense electromagnetic field in which the silver nano-structures have uniform average size and very strong forms of particles, by characterizing a variety of conditions such as, for example, concentration of AgNO3 and reductant, reaction temperature, stirring velocity, single dropwise addition quantity, dropwise addition rate, or total dropwise addition quantity, which were unpredictable in the conventional silver nanoparticle preparation method using AgNO3 aqueous solution and NaBH4 reductant, so that the preparation method can be advantageously applied for the mass production of silver nano-structures for use as substrate of SERS because the method can provide multimer form with enhanced SERS signals and reproducibility, and also ability to selectively control the particle size.

1. Field of the Invention
The present invention relates to a silver nano-structure for surface enhanced Raman scattering (SERS) substrate and silver nano-structure thereby.
2. Description of the Related Art
High sensitivity detection of biological sample or other samples to the level of single molecule detection can be widely utilized in a variety of areas including diagnostics, pathology, toxicology, environmental sampling, or chemical analysis. For this purpose, nano-particles and chemicals labeled with specific substances have been widely used in researches on metabolism, distribution and binding of small amount of synthetic materials and biomolecules. For example, radioisotopes, organic fluorescent dyes or inorganic quantum dots have been widely used.
The method using radioisotopes generally uses 3H, 14C, 32P, 35S, or 125I which are radioactive isotopes of 1H, 12C, 31P, 32S, or 127I. The radioisotopes have almost identical chemical properties as non-radioactive isotopes and thus are arbitrarily substitutable, and their relatively large emission energy enables even a small amount detection. For the above advantages, the radioisotopes have been used for a long period of time. However, using radioisotopes also has shortcomings. That is, it is not easy to conduct the process because of harmful radiation, and it is not convenient to store or conduct experiment with certain isotopes despite large emission energies, particularly those with short half-lives.
One of the representative replacements for the radioisotopes is the organic fluorescent dyes. The organic fluorescent dyes emit light with unique wavelength, as these are excited by the light at certain wavelengths. As the detection methods pursue minimization, radioactive materials showed limited sensitivity, taking long time until detection result is obtained. Compared to this, fluorescent dyes can emit several thousands of photons per molecule when placed under proper conditions, and in theory, it can detect even a single molecule level.
However, using fluorescent dyes also has shortcomings. That is, unlike radioisotopes, it is not possible to directly substitute the atoms of the active ligand, and it is required to connect the fluorescent dyes by distorting certain portions that have relatively less influence on activity based on structure-activity relationship. The fluorescent dyes suffer photobleaching as time passes, and very narrow light wavelength of activation and very wide wavelength of the light emission cause interferences between different fluorescent dyes. Furthermore, the number of available fluorescent dyes is limited.
The quantum dots, which are semiconductor nano materials, are composed of CdSe, CdS, ZnS, ZnSe and emit different colored lights depending on sizes and types. Compared to organic fluorescent dyes, the quantum dots have broader activity wavelengths, while these represent narrow light emission wavelength. Accordingly, there are more quantum dots than organic fluorescent dyes that emit different colors. For the above reasons, quantum dots are more generally used recently, as a method for overcoming drawbacks of the organic fluorescent dyes. However, the quantum dots also have shortcomings such as high toxicity and other constraints that prevent mass production. While there are a variety of quantum dots theoretically, in actual use, the number of quantum dots that can be used is quite limited.
The Raman spectroscopy and/or labeled substances for surface plasmon resonance have thus been suggested to resolve the problems mentioned above.
The surface enhanced Raman scattering (SERS) is the spectroscopic method that utilizes abrupt surge of Raman scattering intensity by more than 106˜108 times higher, where the molecules are adsorbed on roughened surfaces of metal nano-structures such as gold or silver. When the light passes a concrete medium, a certain amount of different types of lights are generated other than the original wavelength of the light, which is the Raman scattering. Some of the scattered lights have varied frequencies from the originally excited light as the vibrating state of the molecules are excited to higher energy level, and the Raman scattering spectrum wavelengths represent chemical composition and structural properties of the light-absorbing molecules in the sample. Accordingly, Raman spectroscopy, in combination with the fast-advancing nano technology, is anticipated to be the future technology that can directly measure single molecules with high sensitivity, and also as the essential tool for medical sensing. The SERS effect is associated with Plasmon resonance phenomenon, in which metal nanoparticles show clear optical resonance in response to incident electromagnetic radiation due to collective coupling among the conductive electrons within the metal. Basically, the nanoparticles of gold, silver, copper and certain other metals can act as a small antenna to enhance centralization of the electromagnetic radiations. Molecules located adjacent to such particles show considerably higher sensitivity than ordinary Raman scattering.
Therefore, researches have actively conducted to perform early diagnosis of genes or proteins (i.e., biomarkers) associated with a variety of disease, using SERS sensors. The Raman spectroscopy provides several advantages that other analysis methods (including infrared spectroscopy) cannot. Compared to infrared spectroscopy which can obtain strong signal only from the molecule with dipole moment, Raman spectroscopy can obtain strong signals even from non-polar molecules which have variations in induced polarizability, which means all the organic molecules have their own Raman shifts (cm−1). In addition, Raman spectroscopy is free from the interference by water molecules, and thus is more suitable for the detection of biomolecules such as proteins or genes. However, the relatively low signal strength hinders the practical use of the Raman spectroscopy despite the long period of researches.
Following the discovery of SERS, researches continued. After the report about SERS which is capable of signal detection in a single molecular level in chaotic aggregates of nanoparticles to which fluorescent molecules are adsorbed (Science 1997, 275(5303), 1102; Phys. Rev. Lett. 1997, 78(9), 1667), researchers reported about SERS potentiation using a variety of nano-structures (nanoparticles, nanoshells, nanowires). To utilize the high sensitivity SERS phenomenon in the development of biosensors, Mirkin Research Group (Northwestern Univ.) has recently successfully conducted high sensitivity DNA analysis using DNA-gold nanoparticles, with the detection limit of such format reaching 20 fM (Science, 2002, 297, 1536). However, none has shown any progress since the initial research about method for preparing single molecule SERS substrate based on salt induced aggregation of silver (Ag) nanoparticles with Raman-active molecules (e.g., Rhodamine 6G). Report said that only fraction (below 1%) of the colloids with heterogeneous aggregation has single molecular SERS activity (J. Phys. Chem. B 2002, 106(2), 311). Although the random heterogeneous (i.e., roughened) surfaces provide a great amount of interesting and essential data associated with the SERS, such strategy is basically not reproducible, because the enhancement is subject to considerable change even by a small change on surface morphology. Recently, Fang et al. reported about quantitative measurement on distribution of enhancement in SERS. While the most concentrated parts (EF>109) were 64 out of total 1,000,000, such only contributed to 24% of the total SERS intensity (Science, 2008, 321, 388). If any structure that can maximize SERS signal is ensured, very useful, high-sensitivity, and high-reliability biomolecule analysis will be made available. This will be also very useful for imaging technology both in vitro and in vivo.
Most SERS detections or, various analytes used colloidal metal particles coated on substrate and/or supports such as aggregated silver nanoparticles. However, while such arrangement enables SERS detection with sometimes 106 to 108 times greater sensitivity, this cannot detect single molecule of the small analyte such as nucleotide. Despite the advantages of SERS, the SERS phenomenon has incompletely elucidated mechanism, and attempts to develop and commercialize nano-biosensors and to apply the SERS phenomenon are still faced with many challenges that have to be tackled with, such as lack of accurate, structurally-defined nanoparticle synthesis and control, and difficulty in reproducibility and reliability due to variation of enhancement efficiency depending on wavelength of the light for use in spectrum measurement, or direction of polarization. Therefore, to resolve the problems explained above, accurate understanding of optical properties of well-defined nano-structures and accurate control on SERS phenomenon at the same time is necessary.
L. Brus et al. (JACS. 2002) reported that SERS signal was enhanced in the metal particle dimmers, when very strong electromagnetic field (hot spot or interstitial field) was formed between two or more nanoparticles, and according to electromagnetic theory calculation, approximately 1012 SERS enhancement is expected from the hot spot. The enhanced sensitivity of Raman detection varies depending on presence or absence of the hot spot, although it is not clearly regular in the colloid particle aggregation. However, none has suggested about the relationship between the physical structure of the hot spot, distance range from the nanoparticles with enhanced sensitivity, and spatial relationship between the analyte to enhance the sensitivity and nanoparticle aggregations. Furthermore, the nanoparticle aggregation is basically unstable in solution, and gives adverse effect on the reproducibility of the single molecular analyte detection.
By amplifying the optical signal, the electromagnetic signals at the external junctions on two or more nano-structures are amplified, thus enabling detection of unique amplified signals (e.g., Raman, fluorescence, scattering) of the molecules at the gap emitting optical signals. However, to obtain SERS signals using such structures, issues like signal quantification, reproducibility of the result, convenience and simplicity of synthesis, cost or stability of probe still remain as the problems to be tackled with.
From the microscopic prospect, the fact that different physical properties appear depending on sizes and shapes of particles can mean hindrance to infinite utilization in the application fields like catalysts, nano devices, nano sensors or medicines. Accordingly, researches focus on inventing nano-structures that are accurately defined structurally. Currently, many preparation methods are available for preparing nanoparticle colloid with regular size distribution and high dispersive powder in 10-100 nm range.
However, it is still necessary to invent SERS substrate with high-sensitivity SERS activity and reproducibility, from the prospect of principles of spectroscopic structure analysis or detection with SERS on molecules adsorbed to metal surfaces. The principle that explains SERS effect is generally categorized into mainly, electromagnetic theory and charge transfer theory. The electromagnetic theory car, be explained with local field enhancement. That is, upon exposure to light that meets plasmon resonance conditions of gold, or silver nanoparticles, the electromagnetic field of electromagnetic radiation is amplified near the surface of the metal nanoparticle. The adsorbed molecules have amplification of Raman scattering due to enhanced electromagnetic radiation. On the other hand, the charge transfer theory is based on chemical enhancement, according to which the metal-molecule complex in charge transferable state theoretically act as resonant condition which mediates resonant Raman scattering. The intensity of SERS mainly relies on the resonance structure of surface plasmon, which is determined according to metal nano-structures. Accordingly, it is necessary to design nano-structures that can increase SERS cross sectional area and to enhance reproducibility.
The SERS phenomenon is comprehensively understood in its mechanism or aspect of spectroscopic structure analysis on adsorbate. The general SERS spectrum for measurement characteristically represents molecules adsorbed on the metal surface. Accordingly, SERS is done mainly to determine orientation of the molecules adsorbed to the nano-structures or vibrational structure thereof, based on the analysis on size of enhancement or vibrational mode (peak intensities and locations) rather than analysis on peak profiles by metal nanoparticles. Generally, gold nanoparticles provide larger SERS cross section area than silver nanoparticles, and better reproducibility. However, due to less competitive price of the gold nanoparticles, demands increases for silver nano-structures with high sensitivity SERS activity and reproducibility. Accordingly, silver nanoparticle colloids are considered to be a good candidate for SERS substrate development. A silver nano-structure preparation method is thus necessary, which can provide silver nano-structures with high sensitivity SERS activity in both adsorbate spectroscopic structural analysis and principle of detection and reproducibility, and which can provide silver nano-structures with hot spots having large SERS cross section areas based on the same.
The present inventors discovered that, in the conventional silver nanoparticle preparation method using AgNO3 aqueous solution and NaBH4 reductant, by characterizing a variety of unpredictable conditions such as, concentration of AgNO3 and reductant, reaction temperature, stirring velocity, single dropwise addition quantity, dropwise addition rate, or total dropwise addition quantity, it is possible to ensure the 'hot spot', the considerably very intense electromagnetic field in which two to four particles are agglomerated in the prepared silver nano-structures in such a form to enhance SERS signals, and also to provide uniform-sized silver nano-structures and provide reproducibility of the silver nano-structures, and therefore, completed the present invention based on such finding.

Preparation method of silver nano-structure for surface enhanced, raman scattering substrate and silver nano-structure thereby

Kangwon National University-Industry Cooperation Foundation


Provided is a dynamometer system provided with a shaft-torque meter, and capable of an equivalent evaluation to that of a system provided with a load cell. A dynamometer system is provided with an encoder for detecting the angular velocity, a shaft-torque meter for detecting the shaft torque, and a control device (6A) for controlling the dynamometer on the basis of the angular velocity (omegaM) of the dynamometer and the detection value (Tsh) of the shaft-torque meter. The torque-control device (6A) is provided with: a computed-torque calculation unit (61A) for calculating a computed-torque value (Tcal) by adding the detection value (Tsh) to a value obtained by multiplying the angular acceleration (omegaMss) by the moment of inertia (TM); and a computed-torque controller (62A) for calculating a torque-current-command value (Tdyref), on the basis of an externally inputted command value (Tref) and a computed-torque value (Tcal).

With a dynamometer system, by connecting a load device such as an electric motor, engine and roller with a dynamometer that absorbs the dynamic force generated by this load device with a common shaft, as well as controlling the dynamometer based on the detection signals of various sensors detecting the angular velocity, torque, etc., and controlling the output of the load device while applying an appropriate load to the load device, various performance tests thereof are carried out.
Such dynamometer systems are roughly classified into two types based on the difference in the torque detection means.
One is a system equipped with an oscillation-type dynamometer like that shown in Patent Document 1. With this system, an oscillator provided to the dynamometer is supported to freely swing via a floating bearing over a base, and between a leading end of a torque arm of this oscillator and the base are coupled by a load cell, torque is detected from the deformation detected by this load cell, and a control system is constructed with this as a controlled variable.
The other one is a non-oscillation-type system, i.e. provided on a base so as not to allow the dynamometer to oscillate as mentioned above. With this system, since detection of torque using the above-mentioned load cell becomes difficult, a control system is constructed that detects the shaft torque between the dynamometer and load device by a shaft-torque meter as shown in Cited Publication 2, and defines this as a controlled variable.
Patent Document 1: Japanese Unexamined Patent Application, Publication No. 2009-109309
Patent Document 2: Japanese Unexamined Patent Application, Publication No. 2011-257205


An infrared camouflage coating system for application to the strategic surfaces of jet engine components comprised of a metal alloy substrate having an oxidized surface and a ferrous sulfide containing silicate glass bonded thereto.

This invention relates to a countermeasure system for protecting jet aircraft from detection by infrared detection systems. More particularly, this invention concerns itself with a high temperature, low reflectance coating system which, when applied to the strategic surfaces of aircraft jet engine components, will effectively reduce the level of emitted energy radiating from the aircraft and render it undetectable by airborne and ground-base infrared detection systems.
Tactical aircraft are prime targets for a variety of infrared seeking missiles and other infrared detection devices. These aircraft are especially vulnerable to air launched missiles while cruising at altitude or during a low level attack. In close support missions, they are vulnerable to ground launched missiles, such as Redeye, which are capable of providing an effective defense against low flying attacking aircraft. The low cost, ease of operation and high reliability of infrared seeking missiles make them an effective threat in all categories of military tatics where aircraft are utilized.
The missile's attack capability to seek out and destroy tactical aircraft could be nullified if the intensity of the jet engine radiation could be decreased in the missile's wavelength and bandwidth of response and the emitted radiation from the engine could be shifted to wavelengths outside of the response range of the missile's detectors. In the last analysis, the reduction of an aircraft's infrared signature requires a combined effort which includes both the incorporation of an efficient cooled exhaust system and the application of an optically, chemically and mechanically stable emissive/reflective coating to the surfaces of jet engine components.
For application to aircraft using advanced jet engines, and particularly for countermeasure purposes, a judicious selection of low reflectance and low emissivity surfaces on critical engine components is required to optimize the trade-off between emission and reflection. Also, the air-breathing environment limits the utilization of previously known coatings designed for thermal control of space oriented countermeasure coating systems. The severe environmental conditions encountered during the operation of a jet engine aircraft include the influences of high temperature stress, overtemperature, erosion, impact by foreign objects and the metallurgical instability of coatings.
As a consequence, a research effort evolved in an attempt to solve the problems encountered by prior art coating systems by providing a low reflective, high temperature, camouflage, coating system which, when applied to the strategic surfaces of jet engine aircraft, will reduce effectively their level of emitted energy and render them undetectable from infrared detection devices. The diminution should be restricted to the 1 to 6 micron wavelength region while the bulk of the radiation in the other wavelength regions should be allowed to propagate freely from the aircraft.
It was found that the problems referred to above could be overcome by the application of a coating system which comprised a glass-ceramic coating having ferrous sulfide as an essential additive ingredient. The coating of this invention overcomes the problems of mechanical instability and lack of mechanical strength that was exhibited by prior art camouflage coatings. Further, the present invention provides a coating that gives emittance values greater than those obtained heretofore. The distinct advantages of mechanical and chemical stability exhibited by this invention favor the use of this coating system as an infrared suppression coating for jet engine aircraft.

Low reflectance infrared camouflage system

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


A linear actuator is provided with an outer tube and an inner tube inserted in the outer tube so as to be free to slide axially. A rod is erected at a central axis part of the inner tube, forming an annular space between the rod and the inner tube. Permanent magnets are retained along an axial direction in the rod, and a holder is fixed to the outer tube for retaining coils which are disposed face to face with the permanent magnets. The holder includes a cylindrical coil holding portion inserted in the annular space such that an extreme end of the cylindrical coil holding portion can move further into and backward from the annular space. The coil holding portion retains the coils within an inner peripheral surface, and a flange portion joined directly to a proximal end of the coil holding portion is fixed to the outer tube.

JP2007-274820A published by the Japan Paten Office proposes a linear actuator which is mounted on a railroad car to produce an damping force. This linear actuator is provided with a cylindrical outer tube having a bottom and a cylindrical inner tube having a bottom that is inserted so as to be free to slide in the outer tube.
The linear actuator disclosed in JP2007-274820A is provided with a columnar inner rod which is disposed on a common axis with the inner tube and fixed to a bottom portion thereof and a cylindrical outer rod which is disposed on a common axis with the outer tube and fixed to a bottom portion thereof. The inner rod is inserted into the outer rod in such a manner that the inner rod can be moved farther into and backward from the outer rod.
The linear actuator is also provided with a magnetic field generator comprising a plurality of annular permanent magnets arranged and retained along an axial direction on an outer peripheral surface of the outer rod and a plurality of coils placed face to face with the magnetic field generator. In this linear actuator, a thrust for relatively driving the inner tube and the outer tube along the axial direction is produced by a magnetic force generated between the magnetic field generator and the coils.
The linear actuator is further provided with a position sensor for detecting the relative positions of the permanent magnets and the coils and a controller for controlling the magnitude and direction of the thrust by regulating currents that flow through the individual coils. The damping force produced by the linear actuator is controlled by the controller.
The coils are retained on an inner periphery of a cylindrical holder which is fixed to an inner periphery of the inner tube. Specifically, there is formed a mating groove in which the holder is fitted in the inner periphery of the inner tube at an open end side thereof. The mating groove is made of a groove portion in which an outer periphery of the holder correctly fits, the groove portion being formed by increasing the inside diameter of the inner tube, and an annular stepped portion formed at a distal end of the groove portion.
An extreme end of the holder is fitted in the groove portion so as to abut against the stepped portion. A flange with an outer periphery having a greater diameter than the inner tube is fixed to an open end of the inner tube. The holder is thereby prevented from falling off from the open end of the inner tube.
When the linear actuator is most extended, the flange comes into contact with a bearing holder provided on an inner periphery of the outer tube at an open end thereof. The bearing holder retains a bearing that slides an outer periphery of the inner tube. When the linear actuator is most contracted, on the other hand, the flange comes into contact with the bottom of the outer tube, whereby the stroke of the inner rod of the linear actuator is restricted.


The motor including a stator having a stator core, and an insulator provided to the stator core for winding a coil thereon, a rotor rotatably provided with respect to the stator, and a tap terminal provided to the insulator for positioning an end of the coil, wherein the coil includes a core wire of aluminum.

1. Field of the Invention
The present invention relates to motors, and more particularly, to a motor which reduces production costs and can enhance productivity and reliability.
2. Discussion of the Related Art
In general, a motor transmits rotating force of a rotor to a rotating shaft which drives a load. For example, the rotating shaft can drive a drum of a washing machine, or a refrigerator fan connected thereto for supplying cold air to a required space.
Also, inside the motor the rotor rotates in an electromagnetic interaction with a stator. For this, the stator has coils wound thereon and, upon application of a current, the rotor rotates with respect to the stator.
Typically, the coil is formed of copper because copper has good electric conductivity, and good ductility that is good for winding. However, the high costs of copper tends to increase the cost of the motor. Moreover, because of the a lack of a stable supply of the raw material which is used to produce copper, international demands for copper occasionally rise sharply.
Therefore, it is required to use a coil made from another material besides copper in order to reduce the production cost of the motor while maintaining the quality of a motor manufactured with copper.

Washing machine motor having insulator accommodating aluminum wire windings


A vessel transfer system utilizes a larger, surface effect vessel with a hull and a cargo deck, having a pressurized volume of air under its hull. The larger vessel cargo deck is lowered relative to a water surface in order to receive a smaller vessel. Lowering is achieved by depressurizing the volume of pressurized air under the hull. Movable propulsors on an air cushion vehicle permit efficient operation under way in an outer position, while minimizing the envelope dimensions for stowage in a well deck, providing clearance from bridges, docks, etc. in an inner position. In the outer position, the propellers operate in more uniform inflow conditions, resulting in improved performance and lower noise levels. In addition, the craft can be arranged to use a full width stern ramp resulting in time saved during cargo loading/unloading. The propellers will be less likely to ingest green water in high sea states.

1. Field of the Invention
The present invention relates to the deep water transfer of a first, smaller marine or amphibious vessel to a second, larger vessel that is a surface effect or air cushion vessel that travels upon a pressurized volume of air, wherein transfer includes depressurizing of the air cushion under the second vessel so that its cargo deck is lowered to an elevation that is at or near the water surface. Such transfer can optionally include a combination of ballasting and a lowering of pressure (or depressurization) of the volume of air under the second vessel.
The present invention also relates to an improved air cushion vehicle having a multiple lane loading ramp and deck arrangement with air propulsors that move between inner and outer positions for enabling transfer to a larger vessel (inboard propulsion position) and increased propulsion efficiency (outboard propulsion position).
2. General Background of the Invention
In the prior art, transfer of a smaller vessel to and from a larger vessel (or a first vessel to a second vessel) has typically been achieved by ballasting with water. Usually, a larger marine vessel is ballasted until a cargo deck of the larger marine vessel is at an elevation sufficiently low in the water to enable the smaller marine vessel to float on the water surface while traveling to the cargo deck of the larger vessel.
In general, air cushion vehicles or "ACV's" (also known as surface effect ships or hovercraft) are known. Examples of such ACV's are disclosed in the US Patents listed in the following table. The following table also lists some patents that involve transfer of item(s) to or from a surface effect vessel.
TABLE 1U.S. DocumentDateNo.Title(MM/DD/YYYY)1,976,046Waterfoil10/09/19342,405,115Floating Structure08/06/19463,065,723Supercavitating Hydrofoils11/27/19623,077,173Base Ventilated Hydrofoil02/12/19633,141,436Hydrofoil Assisted Air07/21/1964Cushion Boat3,458,007Captured Air Bubble (CAB)07/29/1969Ground Effect Machine3,589,058Toy Ground Effect Vehicle06/29/1971With Adjustable StabilizingWeight3,621,932Gas-Cushion Vehicles11/23/19713,817,479Helicopter Powered Air06/18/1974Cushioned Platform3,893,538Ground Effects Vehicle and07/08/1975An Air Terminal3,917,022Twin Cushion Surface Effect11/04/1975Vehicle3,987,865Gas-Cushion Vehicle Skirt10/26/19764,469,334Sealing System For The Air09/04/1984Cushion Of An Air-CushionVessel4,489,667Surface Effect Ship Seals12/25/19844,506,618Propeller And Keel03/26/1985Arrangement For SurfaceEffect Ships4,535,712Variable Air Cushion Mode08/20/1985Vehicle4,543,901Surface Effect Ship Air10/01/1985Cushion Seal System4,646,866Surface Effect Type, Side03/03/1987Keel Vessel Fitted With AnImproved Forward BuoyancyCushion Seal Apparatus4,660,492Catamaran Air Cushion Water04/28/1987Vehicle4,708,077Hull Shapes For Surface11/24/1987Effect Ship With Side WallsAnd Two Modes OfOperation4,714,041Structure of surface effect12/22/1987ship with side walls4,739,719Movable bow seal air ride04/26/1988boat hull4,767,367Integrated Combination08/30/1988Propeller Drive ShaftFairing and Water IntakeSea Chest Arrangement, ForHigh Speed Operating MarineCraft4,984,754Heli-Hover Amphibious01/15/1991Surface Effect Vehicle5,651,327Displacement, Submerged07/29/1997Displacement, Air CushionHydrofoil Ferry Boat5,711,494Aero-Hydroglider01/27/19985,860,383Displacement, Submerged01/19/1999Displacement, Air CushionHydrofoil Ferry Boat5,934,215Stabilized Air Cushioned08/10/1999Marine Vehicle6,293,216Surface Effect Ship (SES)09/25/2001Hull Configuration HavingImproved High SpeedPerformance and HandlingCharacteristics6,439,148Low-Drag, High-Speed Ship08/27/20022002/0164231Craft for Embarking/Landing11/07/2002On Unequipped Shorelines6,487,981Air Assisted Landing Craft12/03/20022003/0000440Air Assisted Landing Craft01/02/20036,526,903High speed M-shaped boat hull03/04/20036,609,472Stable efficient air08/26/2003lubricated ship2005/0211150Variable Hybrid Catamaran09/29/2005Air Cushion Ship2005/0236200Wrapped-cone fingers for10/27/2005skirt systems7,013,826Hybrid Catamaran Air Cushion03/21/2006Ship
Incorporated herein by reference are the foregoing and U.S. Pat. Nos. 4,767,367; 4,984,754; 6,293,216; and 6,439,148. These incorporated by reference patents relate generally to air cushion vehicles, surface effect ships or hovercraft.


An optical amplifying apparatus which includes an optical amplifier, an optical attenuator and a controller. The optical amplifier amplifies a light signal having a variable number of channels. The optical attenuator passes the amplified light signal and has a variable light transmissivity. Prior to varying the number of channels in the light signal, the controller varies the light transmissivity of the optical attenuator so that a power level of the amplified light signal is maintained at an approximately constant level that depends on the number of channels in the light signal prior to the varying the number of channels. While the number of channels in the light signal is being varied, the controller maintains the light transmissivity of the optical attenuator to be constant. Subsequent to varying the number of channels in the light signal, the controller varies the light transmissivity of the optical attenuator so that a power level of the amplified light signal is maintained at an approximately constant level that depends on the number of channels in the light signal subsequent to the varying the number of channels.

1. Field of the Invention
The present invention relates to a fiber optic communication system which uses wavelength division multiplexing to transmit a wavelength-multiplexed optical signal. More specifically, the present invention relates to a controller which controls an optical attenuator or an optical amplifier to change the power level of the wavelength-multiplexed optical signal when the number of channels are varied.
2. Description of the Related Art
Wavelength division multiplexing is used in fiber optic communication systems to transfer a relatively large amount of data at a high speed.
FIG. 1 is a diagram illustrating a conventional fiber optic communication system which uses wavelength division multiplexing to transmit, for example, four channels through a single optical fiber. Referring now to FIG. 1, transmitting units 20-1, 20-2, 20-3 and 20-4 transmit individual carriers having wavelengths .lambda.1-.lambda.4, respectively. Each carrier is modulated with information and represents an individual channel. The different carriers are multiplexed together by an optical multiplexer 22 into a wavelength-multiplexed optical signal. The wavelength-multiplexed optical signal is transmitted through an optical fiber 24 to an optical demultiplexer 26. Optical demultiplexer 26 branches the wavelength-multiplexed optical signal into four separate optical signals having the wavelengths .lambda.1-.lambda.4, respectively. The four separate branched optical signals are then detected by receiving units 28-1, 28-2, 28-3 and 28-4, respectively.
While the above optical fiber communication system multiplexes four carriers together, it is common practice to multiplex more than four carriers. More specifically, many different carriers may be multiplexed together. In this manner, a relatively large amount of data can be transmitted through an optical fiber.
An optical amplifier (not illustrated) or an optical repeater (not illustrated) is typically inserted between optical multiplexer 22 and optical demultiplexer 26, to amplify the wavelength-multiplexed optical signal travelling through optical fiber 24. Such an optical amplifier is typically a rare-earth doped optical fiber amplifier which directly amplifies the wavelength-multiplexed optical signal. That is, a rare-earth doped optical fiber amplifier amplifies the wavelength-multiplexed optical signal without converting the wavelength-multiplexed optical signal into an electrical signal.
Unfortunately, the use of a rare-earth doped optical fiber amplifier causes several problems when the number of channels in the wavelength-multiplexed optical signal is varied. More specifically, during the variation (that is, before the variation in the number of channels is complete), the optical power of each channel can undesireably be varied, thereby causing non-linear degradation or S/N degradation of the wavelength-multiplexed optical signal.

Controller which controls a variable optical attenuator to control the power level of a wavelength-multiplexed optical signal when the number of channels are varied


Techniques for detecting one or more documents that are duplicate or near-duplicate of a first document are provided. The techniques include obtaining a first document, obtaining one or more additional documents, retrieving a set of one or more document signatures for each document, and detecting one or more documents that are duplicate or near-duplicate of the first document by detecting each of the one or more additional documents that have at least a minimum number of signatures in common with the first document, wherein detecting each of the one or more additional documents that have at least a minimum number of signatures in common with the first document comprises dynamically using at least one of a user-configurable similarity definition and a user-configurable similarity threshold value.

Some enterprises and/or companies desire (or can be required) to manage all digital information including emails such that it is not prematurely destroyed or lost and is easily discoverable (for example, to provide the correct information to a court or outside companies in response to a lawsuit). By way of example, electronic discovery (e-discovery) techniques in the legal community can concern the detailed analysis of e-mails gathered in response to a lawsuit. Existing approaches, however, include primarily manual processes, which are labor and cost intensive.
Existing approaches can also include a brute force approach of comparing all sub-strings of a pair of documents. However, such an approach is computationally prohibitive. Further, a primary focus of existing approaches has been on finding near duplicates, but not on dynamic detection of near duplicates or on an online version of the challenge.

Dynamically detecting near-duplicate documents

International Business Machines Corporation


Disclosed is a system for and a method of registering images captured by a computer-controlled microscope. The imaging system of the present invention includes a computer-controlled microscope electrically connected to a controller having a display device. The microscope further includes a barcode reader, a camera, a serial interface, one or more sensors, one or more motors, a light source, a turret, and a data interface. The method of image registration includes the steps of defining areas of interest on a microscope slide, creating a database of microscopic image locations, commanding a microscope to each location, capturing and storing an image, calculating correlation with neighbors, registering correlation scores and offsets, determining an anchor, and attaching neighbors using correlation scores and offsets.

In the field of anatomic pathology, a piece of human tissue is typically inspected and analyzed by marking a sample with a stain that reveals a visual indicator of diagnostic significance and then placing the stained tissue on a slide for viewing under a microscope. Automated imaging systems exist today that capture microscopic image data using a scanning instrument, such as a digital camera in combination with a computer-controlled microscope. Capturing areas of the slide sample at high magnification is necessary for examining minute features of the tissue. A single image of an entire tissue specimen at a high magnification such as 40× requires significant computer storage space and involves lengthy retrieval times. Alternatively, by collecting and storing the sample as any number of contiguous micro images at high objectives, the system can perform various compression techniques and make improvements to data acquisition, retrieval, display, and storage of the images.
A challenge relating to microscopy for anatomic pathology involves assembling micro images captured at high magnifications into a variety of fields of view. This could include a composite image of the entire slide sample or a field of view spanning any portion of the specimen. For example, U.S. Pat. No. 6,404,906, entitled, "Method and apparatus for acquiring and reconstructing magnified specimen images from a computer-controlled microscope," describes a method of using a computer-controlled microscope system to provide a reconstructed, seamless image from several contiguous fields of view to show the architecture and spatial relationship of biological material in a specimen. A macro image of contiguous image titles at a low magnification and optical resolution is obtained, and the user navigates within the macro image and selects areas. Higher magnification titles for the selected area are assembled and viewed at a higher magnification and optical resolution as a composite micro image of the selected area. Both the macro and micro images may be displayed simultaneously. Preferably, the user may scroll and cause additional fields of view to be added to previously displayed fields of view.
While the '906 patent provides a means of reconstructing micro images into other fields of view, it does not ensure that the system captured the expected image in the first place, nor does it explain what to do if image capture was imprecise. Calibration of such a system is frequently performed, but it is still unfeasible to account for every minor inaccuracy when working with images at very high magnification levels. One example of a calibration inaccuracy in the system might occur while moving the turret from one microscopic image to another. Because this process involves mechanical precision in measurements of microns, a slightly different image from what was expected may be captured. As a result, significant tissue samples may be overlooked. In addition, visible discontinuities may exist for any macro image including micro images where capture was inaccurate. What is needed is a means of seamlessly aligning microscopic images into larger fields of view.
Furthermore, if image capture by an automated microscope system is consistently inaccurate, this may indicate a need to calibrate the system. By analyzing the offset of each image, the system may be able to determine the variable by which inaccuracy is occurring. What is needed is a means of distinguishing between reasonable system inaccuracies and recurring system inaccuracies.

System and method of registering field of view


The disclosure relates to a method of configuring end-to-end ODUj (lower order ODU) network trails across OTN (Optical Transport Network), in which the tributary port number (TPN) of the lower order ODUj inside higher order ODUk is specified. The time-slot value associated with the TPN is not to be specified by the user. The time-slots are dynamically allocated on the transmit side. On the receive side, there would be a capability in the ODUk adaptation sink function to find the set of time-slots associated with the TPN based on the received multiplex structure identifier (MSI). That is for an ODUj entity with a fixed TPN, the transmitted time-slots can change and the receive end can detect this change and based on that de-multiplex the ODUj from the ODUk.

Optical Transport Network (OTN) is a set of standards defined by the ITU-T for transmission of optical signals over fiber using wavelength division multiplexing (WDM). These standards cover the physical layer, signal rate, format specification, equipment functional requirements and OAM&P (Operation, Administration, Maintenance and Provisioning) for the network.
OTN provides a method to transport a client signal such as an STM-16/OC-48 or a 10G Ethernet or a storage area network (SAN) signal efficiently over fiber. Multiple client signals can be carried in the same fiber using time-division multiplexing (TDM) and WDM. OTN is significantly less complex compared to SONET/SDH and this reduced complexity offers optimized overhead and substantial reduction in costs. Further, the multiplexing bandwidth granularity is one or two orders of magnitude greater than SONET/SDH making OTN much more scalable to higher rates. It also provides an integrated forward error correction (FEC) mechanism that allows for greater reach between subsequent nodes and higher bit rates on the same fiber. This, too, adds to reduction in costs.
The Optical Channel Payload Unit (OPU) is the basic container that carries the client signal. The client signal is mapped into the payload area of the OPU using either the Asynchronous Mapping Procedure (AMP) or Generic Mapping Procedure (GMP). It is a set of overhead bytes containing information to support adaptation of the client signal. This overhead is terminated wherever the client signal is assembled or disassembled. The payload area of the OPU consists of 4 rows×3808 columns (columns 17-3824). The overhead area consists of 4 rows×2 columns (columns 15-16).
The Optical Data Channel Unit (ODU) consists of the OPU and an ODU overhead area. The ODU overhead area is 4 rows×14 columns (columns 1-14). Note that row 1 of this overhead area is reserved for the frame alignment bytes and the Optical Channel Transport Unit (OTU). The ODU overhead contains information for the maintenance and operational functionality to support optical channels. It also has provision for end-to-end path monitoring of the ODU path and up to six level of tandem connection monitoring. The overhead is terminated wherever the ODU is assembled or disassembled.
The Optical Channel Transport Unit (OTU) conditions the ODU for transport over an optical channel network connection. The OTU consists of a Framing Alignment (FA) overhead, OTU overhead and a FEC. The FEC is 4 rows×256 columns (columns 3825-4080). The FA overhead is a fixed standardized pattern that is used to detect the start of the OTU frame and a one byte multi-frame alignment signal to indicate the multi-frame number of the current OTU frame. The OTU overhead contains information for operational functional to support the transport via one or more optical channel connections. This overhead is terminated wherever the OTU is assembled or disassembled.
The following explains OTN Multiplexing Structure. At the ODU level, OTN supports a single level of multiplexing. The higher order ODU is designated as ODUk and the lower order ODUs contained within the ODUk as ODUj. The ODUk is divided into timeslots of 1.25 G (ODU0 capacity) in case of equipment adhering to the newer standard, while older equipment uses 2.5 G (ODU1 capacity) timeslots. The Table-I below illustrates the number of timeslots each ODU has.
TABLE IODUk type2.5G timeslots1.25G timeslotsODU112ODU248ODU31632ODU4—80
Thus, an ODU2 may contain a maximum of 4 ODU1s or 8 ODU0. An ODU3 may contain a maximum of 16 ODU1, 4 ODU2 or 32 ODU0 and so on. The ODUk may contain a mix of ODUjs within the limit of the capacity of the ODUk.
The multiplexing of the ODUjs within the ODUk is done based on interleaving timeslots. FIG. 1 illustrates multiplexing of the ODUjs within the ODUk for k=2 and ODUj (j=1). The ODU1 overhead for each of the ODU1s repeats every four ODU2 frames. This is locked to bits 7 and 8 of the MFAS byte. Hence, for each ODU1 that is multiplexed as part of the ODU2 may have a justification opportunity every four ODU2 frames.
For inter-operating with older equipment that uses the 2.5 G timeslot scheme with newer equipment that use the 1.25 G timeslots, standards define that an ODU1 that is multiplexed into ODU2 uses the 'i' (i=1, 2, 3, 4) and the 'i+n' (n=4) timeslots. This ensures that the receiver would see the 'i'th ODU1 in every fourth column of the ODU2 payload area. Similarly for ODU3 i=1, 2 . . . 16 and n=16. This takes care of the overhead repeating exactly once every four frames.
The complete multiplexing hierarchy for ODUk through ODUj is shown in the FIG. 2.
In OTN based equipments it's a common requirement to map/de-map lower order ODUjs inside higher order ODUk's using an ODU connection function to route, groom and multiplex the ODUjs clients in an ODUk server.
In some of the HO ODUk's a mix of different LO ODUjs are allowed. If a restriction is imposed on the timeslot usage for a particular LO ODUj, it can lead to possible fragmentations at time slot level depending on the order of connections created. To avoid such fragmentations and ensure usage of complete bandwidth available in ODUk, the ODUjs are allowed to be flexibly mapped into any of the timeslots available.
The SDH systems have a connection model centered on connections identified by STM port number and timeslots S, K, L and M. Similarly, in the current state of the art, for OTN networks too the connection model is centered on time-slots occupied by the LO ODUj inside the HO ODUk. As illustrated in FIG. 3, the 'A' and 'Z' ends for an ODUj trail agree upon the set of time-slots which the ODUj will occupy inside the ODUk. The time-slots used at the originating end for the ODUj ('A') and those used at the receive end ('Z') hence must be the same. This agreement henceforth will be referred to as "policy" for a connection. Similarly, the "identity" of the ODUj in the network is based on the set of time-slots with which it's associated.
At either of the end-points of the network connection, the child ODUj (as a client) inside parent ODUk (as a server) is identified as follows:                ODUj identifier=[ODUk identifier],                    [Set of timeslots in HO ODUk]
Since, the identity for the ODUj involves a set of time-slots, the 'A' and 'Z' ends have to agree upon their respective transmit (at 'A' end) and receive time-slots (at 'Z' end) if the intended ODUj trail is the transport entity being connected end-to-end.
As an example ODU3 is taken as an example of HO ODUk and ODU2 as a LO ODUj. An OPU3 (one to one mapped with the ODU3) when partitioned into 2.5 G timeslots looks as shown in FIG. 4 (taken from ITU-T G.709/Y.1331).
As shown in the FIG. 4 there are 16 tributary time-slots in each OPU3 frame. If one has to multiplex 4 ODU2s inside this OPU3 there is a flexibility provided in terms of each ODU2s taking any set of 4 timeslots out of these 16 timeslots. FIG. 5 shows the multiplex structure being carried in the PSI bytes over an ODU3 multi-frame.
The tributary port numbers (TPNs) are a way to group the time-slots and convey which single ODUj they conform to. The TPN to TS mapping is carried in the multiplex structure identifier (MSI). The ODTU type tells if the time-slot is carrying an ODTU13 or ODTU23.
The ODTU type field takes different meanings based on the OPUk type; here it's shown for an OPU3. For example for OPU4, the ODTU type field is absent and instead there's a 1 bit field which just says "allocated" or "unallocated".
As an example, when multiplexing 4 ODU2s in an OPU3 (mapped into ODU3 finally), the TPN values range from 1 to 4 with each value representing a single ODUj.                [TPN=1] represents an ODU2 in [TS=1, 10, 11, 16]        [TPN=2] represents an ODU2 in [TS=2, 4, 6, 8]        [TPN=3] represents an ODU2 in [TS=3, 13, 14, 15]        [TPN=4] represents an ODU2 in [TS=5, 7, 9, 12]
So, as an entity identification of an ODU2 on end-to-end basis one can set a policy between A and Z ends as shown in FIG. 3 that states as follows:
'A' end will transmit an ODU2 in question on [TS=1, 10, 11, 16]
'B' end must receive the same ODU2 in question on [TS=1, 10, 11, 16]
In this case, if one end has to setup a connection in the network, that end is expected to choose these 4 ODU2 time-slots inside the ODU3. This is a traditional method by specifying the time-slots.

Method for configuring end-to-end lower order ODU network trails across optical transport network


A dispensing device for dispensing a predetermined amount of solid materials in powder or granular form allows a predetermined quantity, say for example a spoonful of sugar, to be dispensed into a coffee cup. The dispensing device allows measured quantities to be dispensed which avoids having to use a teaspoon or other measuring device. The device has a container, a body member below the container having a longitudinal passage therein, a top opening from the container to the longitudinal passage, a sliding member with a substantially rectangular cross-section, the sliding member having a sliding fit within the longitudinal passage, movable from a first position to a second position. A dispenser aperture extends through the sliding member and is positioned under the top opening from the container when the sliding member is in the first position, and a bottom opening in the body member from a bottom surface of the longitudinal passage to permit solids to dispense from the body member when the sliding member is in the second position, the bottom opening not overlapping the top opening.

The present invention relates to a dispensing device and more specifically to a dispensing device for dispensing a predetermined amount of solid materials in powder or granular form.
Dispensing devices positioned beneath hoppers, containers and the like are well known. In some cases these devices dispense solid materials in the form of powder or granular materials by pushing or pulling a lever such that a measured quantity of the material is dispensed. Examples of such dispensing devices are disclosed by Hammer in U.S. Pat. No. 2,561,696 and Jones in U.S. Pat. No. 559,386. Both of these patents disclose a dispensing aperture or chamber which is positioned first under an opening from a container, hopper or the like so material fills the chamber. The chamber is then moved over a discharge opening so that the material is dispensed.
Castro in U.S. Pat. No. 4,109,835 shows another embodiment of a dispensing device wherein a dispensing aperture or chamber is fixedly positioned with a top or filling aperture in a top sliding plate and a bottom or discharge aperture in a bottom sliding plate. The plates are moved together from a first position to a second position, in the first position the chamber fills and in the second position the chamber empties. The patents described herein are but a few of the known types of dispensers. Furthermore liquid dispensers for soap and the like having similar types of mechanisms are known.
It is an aim of the present invention to provide a portable dispensing device that can be used for dispensing food such as coffee, sugar, salt and the like and which can be hand held over for example a cup of coffee. By squeezing or depressing a handle or dispensing knob, a predetermined measure of sugar can be dispensed into the coffee. The device can preferably be used with one hand. Such a device avoids having to use a spoon to measure a specific quantity of sugar. In existing types of sugar jars it is difficult to control the exact quantity of sugar dispensed and the present measuring device provides a dispenser which always dispenses the same quantity of sugar or other particulate material every time the handle or knob is depressed.
The present invention provides a device for dispensing a predetermined amount of solids comprising a container, a body member below the container having a longitudinal passage therein, a top opening from the container to the longitudinal passage, a sliding member with a substantially rectangular cross-section, the sliding member having a sliding fit within the longitudinal passage movable from a first position to a second position, a dispenser aperture extending through the sliding member and positioned under the top opening from the container when the sliding member is in the first position, a bottom opening in the body member from a bottom surface of the longitudinal passage to permit solids to dispense from the body member when the sliding member is in the second position, the bottom opening not overlapping the top opening.
In another embodiment there is provided an adjustment mechanism for varying the volume of the dispenser aperture so that the amount of solids being dispensed can be varied.

Device for dispensing a predetermined amount of solids


A vehicle has a motor and an engine each serving as a driving source for running the vehicle, and assembled batteries each capable of supplying an electric power to the motor. The assembled batteries include a high-power assembled battery and a high-capacity assembled battery. The high-power assembled battery is capable of charge and discharge with current relatively larger than that in the high-capacity assembled battery, and the high-capacity assembled battery has energy capacity relatively larger than that of the high-power assembled battery. In running of the vehicle using output from the motor with the engine stopped, the high-capacity assembled battery supplies more electric power to the motor than that in the high-power assembled battery. The high-power assembled battery is placed in a vehicle-inside space accommodating a passenger or baggage, and the high-capacity assembled battery is placed in a vehicle-outside space located on an outer face of a vehicle body.

A battery system described in Patent Document 1 includes a high-capacity battery and a high-power battery which are connected in parallel to a load. The high-capacity battery has an energy capacity larger than that of the high-power battery. The high-power battery allows charge and discharge with a current larger than that in the high-capacity battery.


A method for chemical-mechanical polishing two adjacent structures of a semiconductor device is provided. The method for mechanical polishing comprising: (a) providing a semiconductor device comprising a recess formed in a surface thereof, a first layer formed over the surface, and a second layer filled with the recess and formed on the first layer; and (b) substantially polishing the first and second layer with a pad and a substantially inhibitor-free slurry, wherein the pad comprising a corrosion inhibitor of the second layer.

1. Field of the Invention
The invention relates in general to a pad and a method for chemical mechanical polishing, and more particularly to a pad comprising a corrosion inhibitor and method for chemical mechanical polishing using the same.
2. Description of the Related Art
Reliably producing sub-half micron and smaller features is one of the key technologies for the next generation of very large scale integration (VLSI) and ultra large-scale integration (ULSI) of semiconductor devices. However, as the limits of circuit technology are pushed, the shrinking dimensions of interconnects in VLSI and ULSI technology have placed additional demands on processing capabilities. Reliable formation of interconnects is important to VLSI and ULSI success and to the continued effort to increase circuit density and quality of individual substrates and die.
Multilevel interconnects are formed using sequential material deposition and material removal techniques on a substrate surface to form features therein. As layers of materials are sequentially deposited and removed, the uppermost surface of the substrate may become non-planar across its surface and require planarization prior to further processing. Planarization or "polishing" is a process where material is removed from the surface of the substrate to form a generally even, planar surface. Planarization is useful in removing excess deposited material, removing undesired surface topography, and surface defects, such as surface roughness, agglomerated materials, crystal lattice damage, scratches, and contaminated layers or materials to provide an even surface for subsequent photolithography and other semiconductor processes.
Chemical mechanical planarization, or chemical mechanical polishing (CMP), is a common technique used to planarize substrates. In conventional CMP techniques, a substrate carrier or polishing head is mounted on a carrier assembly and positioned in contact with a polishing article in a CMP apparatus. The carrier assembly provides a controllable pressure to the substrate urging the substrate against the polishing pad. The pad is moved relative to the substrate by an external driving force. Thus, the CMP apparatus effects polishing or rubbing movement between the surface of the substrate and the polishing article while dispersing a polishing composition to effect both chemical activity and mechanical activity.
However, materials deposited on the surface of a substrate 10 to fill feature definitions formed therein often result in unevenly formed surfaces. Polishing of surfaces with excess material, called overburden, may result in the retention of residues from inadequate metal removal over one feature definition 15. Overpolishing processes to remove such residues may result in excess metal removal over another feature definition 25. Excess metal removal can form topographical defects, such as concavities or depressions known as dishing 30, over features 25, as shown in FIG. 1.
Dishing of features and retention of residues on the substrate surface are undesirable since dishing and residues may detrimentally affect subsequent processing of the substrate. For example, dishing results in a non-planar surface that impairs the ability to print high-resolution lines during subsequent photolithographic steps and detrimentally affects subsequent surface topography of the substrate, which affects device formation and yields. Dishing also detrimentally affects the performance of devices by lowering the conductance and increasing the resistance of the devices, causing device variability and device yield loss. Residues may lead to uneven polishing of subsequent materials, such as barrier layer materials (not shown) disposed between the conductive material and the substrate surface. Uneven polishing will also increase defect formation in devices and reduce substrate yields.
Therefore, there is a need for compositions and methods for removing material from a substrate that minimizes damage to the substrate during planarization.

Pad and method for chemical mechanical polishing


A process for producing defect free multilayer printed circuit boards using low pressure lamination with a cyanate ester laminate. Alternate layers of cyanate ester core and prepreg materials are stacked and at least partially cured under pressure and elevated temperatures to produce a multilayer laminated printed circuit board. The use of a low pressure cure avoids the storage of stress within the laminate. Such stress would otherwise produce microcracking and/or delamination of the circuit board when the stress is released during the subsequent thermal cycling or exposure to caustics attendant with working and reworking of the printed circuit board.

1. Technical Field
The present invention relates to multilayer printed circuit boards. More particularly, the present invention relates to the use of cyanate ester laminates to produce multilayer printed circuit boards.
2. Description of the Prior Art
Multilayer printed circuit boards are manufactured from various resins, which are mixed with solvents and other chemicals, and then coated onto a glass fabric. The resulting board material is available in a partially cured form, referred to `prepreg`, and in a cured form, usually having a metal coating on one or both sides, and which is referred to as a `core`.
The cores are patterned, typically using an image etch process, to produce an electrical interconnect on the metal coated surface of each core. The patterned cores, each of which makes up one or two layers of a multilayer printed circuit board, are then stacked. One or more layers of prepreg material are placed between each core in the stack. The stacked materials are then cured to form a multilayer laminate.
The curing process involves the application of heat and pressure using various techniques: for example, press molding, with or without vacuum assist; and autoclave molding, with or without vacuum bags. The FR-4 materials are laminated over a very wide range of pressures, e.g. 25-450 psi, based on economic convenience, but more typically in the 200-350 psi range. Manufacturers may adjust the heat rise and pressure to affect cycle times in a variety of beneficial ways. The laminating temperature varies according to the degree of cure needed to produce physical and mechanical properties required for the end product. A typical temperature of 180.degree. C. is produced by gradually raising the temperature, holding the temperature constant for a period of time, and then lowering the temperature to room temperature.
After curing, the boards are drilled, imaged and plated to electrically connect surface and internal conductive layers, and components are mounted to the board, by wave soldering or surface mount techniques.
Of the various resins available, FR-4, has been the most commonly used and widely accepted material for making printing circuit boards. Other resins that are in use in the printed circuit board industry include polyimides, BT epoxy, and cyanate esters, among yet others. Polyimides, due to their high cost, have found limited acceptance; while BT epoxy is difficult to process and therefore expensive.
Cyanate esters have several advantages over both FR-4 and polyimides and are therefore an attractive alternative to these and other materials. Cyanate esters are less expensive than polyimides; they are better suited for thick multilayer structures than FR-4 because they have a low thermal coefficient of expansion; and they are better suited for high frequency applications than FR-4 because they have a lower dielectric constant and low loss factors. Thus, in high frequency applications, e.g. 50-100 MHz, printed circuit boards made of FR-4 require special design considerations, including component placement, and load calculations to take into account the RF characteristics of the board. Additionally, it is very difficult to make thick boards of FR-4 because the vias used to interconnect the various layers of a multilayer FR-4 printed circuit board are subjected to considerable stress due to expansion of the board under conditions of thermal cycling, such that the vias often fail.
Cyanate ester resins, such as Arocy B-40S, are available from chemical manufacturers, such as Ciba Geigy of Switzerland, among others; cores and prepreg materials made from cyanate ester resins, such as N8000, are available from laminators, such as Nelco of Fullerton, Calif., among others.
One of the major drawbacks of cyanate ester printed circuit board laminates has been the tendency of such laminates to form microcracks during normal (i.e. FR-4 type) board fabrication processes. Microcracks form around the drilled holes in a printed circuit board and sometimes on the laminate surface when the cyanate ester material comes into contact with caustic solutions as are typically used in processing printed circuit boards. Such caustic solutions are used for a variety of purposes, e.g. electroless Cu plating, image resist development, and de-smearing of drilled holes.
These microcracks can cause long term electrical reliability problems on finished assemblies in products. For example, the cracks allow electrolytes to accumulate within the board material which, in time, may grow dendrites that become metal connections, and, that ultimately create short circuits. This process is referred to as anodic cathodic filamentosis. It is important to note that the cracks form in the cyanate ester polymer resin in pure and alloyed forms of the material (this includes catalysts, flame retardants, and solvents), with and without glass reinforcement.

Process for producing defect free multilayer printed circuit boards