Methods of forming a semiconductor device structure at advanced technology nodes and respective semiconductor device structures are provided at advanced technology nodes, i.e., smaller than 100 nm. In some illustrative embodiments, a fluorine implantation process for implanting fluorine at least into a polysilicon layer formed over a dielectric layer structure is performed prior to patterning the gate dielectric layer structure and the polysilicon layer for forming a gate structure and implanting source and drain regions at opposing sides of the gate structure.

1. Field of the Invention
The present invention generally relates to integrated circuits, and, more particularly, to semiconductor device structures with gate structures having a fluorine doping profile and methods of forming according semiconductor device structures.
2. Description of the Related Art
The majority of present-day integrated circuits (ICs) are implemented by using a plurality of interconnected field effect transistors (FETs), also called metal oxide semiconductor field effect transistors (MOSFETs) or simply MOS transistors. Typically, present-day integrated circuits are implemented by millions of MOS transistors which are formed on a semiconductor substrate with a given surface area.
Basically, MOS transistors act as electronic switching elements wherein a current through a channel region, formed between source and drain regions of a MOS transistor, is controlled by a gate electrode which is typically disposed over the channel region, independent from whether a PMOS transistor or an NMOS transistor is considered. Particularly, the conductivity state of a transistor is changed by a voltage applied to the gate electrode passing a so-called threshold voltage (Vt). In general, the threshold voltage depends nontrivially on the transistor's properties, such as size, material, etc.
In efforts to build integrated circuits with a greater number of transistors and faster semiconductor devices, developments in semiconductor technologies are directed to ultra large scale integration (ULSI), which resulted in ICs of ever-decreasing size and, therefore, of MOS transistors having reduced sizes. Herein, a critical dimension (CD) is represented by a width or length dimension of a line or space that has been identified as critical to the device under fabrication for operating properly and, furthermore, which dimension determines the device performance. In present-day semiconductor technology, the CDs of microelectronic devices have been approaching the deep sub-micron regime so as to continually meet the demand for faster and also less power-consuming semiconductor devices, so-called low power devices, which allow fabricating advanced microprocessors and digital circuits. In general, it is attempted to provide semiconductor device structures having improved high energy efficiency.
However, as semiconductor devices and device features have become smaller in order to comply with requirements set by advanced integration densities, conventional fabrication techniques have been pushed to their limits, challenging their abilities to produce finely defined features at presently required scales. Consequently, developers are faced with increasing challenges and constraints due to scaling limitations which arise as semiconductor devices continue to decrease in size.
Normally, millions of individual semiconductor devices, such as PMOS transistors or NMOS transistors, are provided on a microchip for implementing IC structures. As transistor performance depends crucially on several factors, for example, on the threshold voltage, it is easy to see that it is highly nontrivial to control a chip's performance. Therefore, controlling a chip's performance generally requires keeping many parameters of individual transistors under control, especially for strongly-scaled semiconductor devices. For example, deviations in the threshold voltage of transistor structures across a semiconductor chip strongly affect the reliability of the whole chip under fabrication. In order to ascertain a reliable controllability of transistor devices across a chip, a well-defined adjustment of the threshold voltage for each transistor has to be maintained to a high degree of accuracy. As the threshold voltage alone already depends on many factors, it is necessary to provide a carefully controlled process flow for fabricating transistor devices which reliably meets all factors.
In practice, fabricated chips are often provided to customers in so-called technology platforms with which many electrical parameters are to be specified as a function of device geometries. In this regard, the dependency of the threshold voltage variation on the device geometry, and particularly on the gate length, is an important example of the parameters to be specified.
FIG. 1 illustrates very schematically a relation between a length of a semiconductor device (L in μm) plotted against the linear threshold voltage (VtLin in V). As shown in FIG. 1, scaling down transistor devices in their length dimension induces a roll-up or roll-off of VtLin. By way of example, when starting from a length dimension of around 1 μm, a VtLin roll-up of roughly around 0.1 V may be expected when scaling down to about 72 μm.
It is generally accepted that so-called short channel effects and reverse short channel effects represent an important factor when discussing the dependency of the threshold voltage on the gate length as they become more relevant at smaller scales. Herein, the relative strength of well dosages, halo dosages and the dosages of extension regions in turn may strongly affect the reverse short channel effect. In conventional device engineering, it is attempted to carefully choose implant settings for meeting as much of the device performance criteria as possible, while showing a reasonable behavior for the dependency of the threshold voltage on the gate length. However, this does not allow actively adjusting the dependency of the threshold voltage on the gate length to a desired degree because it is rather a mere consequence of the implant settings as the performance criteria (in a broad sense, covering threshold voltage, on-current, off-current etc.) dominate over possible ranges of the implant settings.
In particular, all devices with different threshold flavors (low-threshold voltage or LVT devices, super-low threshold or SLVT devices, regular threshold voltage or RVT devices and high threshold voltage or HVT devices) in advanced high-k metal gate technologies show reverse short channel effects. In practice, no solution has been proposed for reducing the above-discussed degrading effects without deteriorating the device performance.
This may be understood by considering that although, in theory, a stable and flatter dependency of the threshold voltage on the gate length may be obtained by changing implant settings of well implantation, halo implantation and source/drain extension implantation, it is not possible to simultaneously improve all performance criteria. Therefore, in practice, such approaches only provide limited space for adjustments of the dependency of the threshold voltage on the gate length, mostly on cost of lower device performance.
US Patent Publication 2010/0148271 relates to a method for gate leakage reduction and threshold voltage shift control by implanting fluorine ions into a gate dielectric. This effect is based on the observation that the threshold voltage increases by 6.7 mV when a fluorine implant dosage is increased by 1×1015 atoms/cm2 for NMOS devices (NMOS roll-up), while the threshold voltage of PMOS devices is increased by 20 mV when an implant dosage of fluorine is increased by 1×1015 atoms/cm2 (PMOS roll-up). In the framework of US Patent Publication 2010/0148271, the threshold voltages of PMOS and NMOS devices may be matched by appropriately raising the threshold voltage of PMOS devices relative to NMOS devices.
US Patent Publication 2005/0136579 discloses a method for manufacturing a metal oxide transistor having reduced 1/f noise by implanting a fluorine dopant into a polysilicon layer and diffusing the fluorine dopants into a gate dielectric material layer formed underneath the polysilicon layer by thermal annealing and to subsequently form gate electrodes.
However, these conventional approaches basically raise the threshold voltage, while, for, advanced semiconductor devices, low performance and low power consumption is desired. Therefore, it is desirable to continue in lowering threshold voltages of semiconductor devices at advancing technology nodes.
It is desirable to provide technologies at smaller technology nodes which enable reducing variations in the threshold voltage of semiconductor devices.
It is desirable to provide a method which allows for tuning the dependency of the threshold voltage on the gate length without degrading the rest of the performance indicators. Furthermore, it is desirable to provide semiconductor device structures having a stable and flat dependency of the threshold voltage on the gate length and simultaneously meeting required advanced high device performance criteria.

Method of forming a semiconductor device structure employing fluorine doping and according semiconductor device structure


A device for moving plate-shaped objects from a removal point, in which the objects are oriented substantially perpendicularly, to a delivery point, in which the objects are oriented substantially horizontally, includes a removal gripper moveable to and fro between the removal and the delivery points by a drive and which is rotated during the movement. The removal gripper is arranged on a lever so as to rotate with respect to the lever, which is pivoted to and fro by a drive. The removal gripper is connected to a shaft mounted rotatably in the lever and on which a wheel is fastened. An elongate, flexible element is placed over the wheel and fixed immovably in the direction of the longitudinal extension thereof. During pivoting of the lever, the wheel rolls on the elongate element. The movement of the gripper is thus superimposed with a rotational movement of the removal gripper.

Devices that gather plate-shaped objects stacked on top of one another in a magazine are known from AT 241 565 B and AT 352 198 B. This superimposed arrangement of the plate-shaped objects in a stack results in substantial friction when the bottommost plate-shaped object is removed, especially in the case of larger stacks; this friction impedes separation of the plate-shaped objects. This is particularly true when the plate-shaped objects, gathered in a magazine, are plates or separators for storage batteries. For this reason it was previously proposed in AT 352 198 B that a clamping device, operable independent from the removal device, be provided at some distance from the removal point, in order to hold the weight of the stack during the withdrawal process.
Devices that move plate-shaped objects are known from GB 1,522,154 A and GB 1,581,764 A. These known devices require retractable restraints that are provided at the removal point. These restraints are problematic in that they must be synchronized with the movements of the removal gripper. Such restraints, in the form of retainer plates or retainer wings, are, however, necessary with the known devices, as they call for conveyor chains that seize the plate-shaped objects from below, in order to move them forward.
Devices for the removal of plate-shaped objects from stacks of such objects are further known from AT 387 294 B, U.S. Pat. No. 5,503,519 A, and EP 1 044 151 A.
Further devices for moving plate-shaped objects are known from AT 379 565 B and AT 389 256 B.
AT 398 256 B concerns a device for the removal of storage-battery plates from a stack and the depositing of the storage-battery plates on a conveyor. This device possesses two alternating grippers that each grasp a storage-battery plate. The grippers are moved alternatingly to and fro to a removal point, which gathers the first storage-battery plate of the stack, and to a delivery point, which is assigned to a conveyor. The grippers are mounted on levers, which swivel in the device. Each gripper is mounted on its lever such that it can rotate 360° about an axis of rotation aligned parallel to its pivot axis and can be turned in one direction with a drive. In order to improve the grasping of a storage-battery plate, the grippers stand still relative to the lever which is carrying them when said levers are located in their rotated position corresponding to the removal point.
WO 1992/01619 A discloses a device for moving plate-shaped objects, whereby the objects are oriented perpendicularly and are delivered horizontally. A removal gripper is movable to and fro and is twisted during movement. The removal gripper is arranged to twist on a lever opposite the lever, so that the lever can be pivoted to and fro by a drive. Furthermore, the removal gripper is associated with a rotating shaft.
JP 7242335 A and WO 1998/39240 A1 disclose devices for moving plate-shaped objects from a removal point, at which the removal gripper is moved only to and fro or the removal gripper is set on a revolving disc.
All known devices for handling plate-shaped objects, especially battery- or storage-battery plates, employ comparatively elaborate controls and lever configurations in order to move the removal gripper between the removal point and the delivery point, since during this motion the removal gripper must not only be moved to and fro between the positions mentioned, but must also pivot the plate-shaped objects in its grip by an angle on order of 90°.
A device for handling battery plates has become known as a component of a jacketing and stacking machine, type BMV10, from Rosendahl Maschinen GmbH in Pischelsdorf (Austria). With this known device the removal gripper is moved to and fro between the removal point and the delivery point by a sophisticated lever mechanism. In order to accomplish the movement between the removal point and the delivery point, a lever mechanism, which can pivot to and fro by means of a crank mechanism comprising a connecting rod and a crank, is assigned to the removal gripper. Since the removal gripper at the removal point must be pivoted at an angle on the order of 90° opposite the delivery point, the removal gripper is guided during the previously described to and fro movement via a link and in connection with a lever that has one fixed pivot point on the suspension and one on the removal gripper, pivoted at an angle on the order of 90°.
This device has proved its value per se; however, it has, with regards to its performance capability, run up against mechanical limits. As a result, there exists a need for a device of the type mentioned at the beginning; one which works faster and more reliably than the known devices.

Device for handling plate-shaped objects


A method for dynamic allocation of communication resources includes (1) determining a risk-return characterization of a plurality of communication resource allocations across a plurality of communication channels in a communication system, (2) selecting a first allocation of the plurality of communication resource allocations from the risk-return characterization according to at least one predetermined criterium, and (3) automatically allocating communication resources among the plurality of communication channels according to the first allocation.

Communication systems can be grouped into wireline communication systems, wireless communication systems, and hybrid communication systems. Wireline communication systems rely on a tangible communication medium, such as an optical cable, a coaxial electrical cable, and/or a twisted-pair electrical cable, to transmit data. Wireless communication systems do not require a tangible communication medium, and wireless communication systems transmit data using techniques such as optical and radio frequency data transmission. Hybrid wireline-wireless communication systems include at least one wireline communication system and at least one wireless communication system.
Both wireline and wireless communication systems often include two or more communication channels. For example, a base station in a wireless communication system may transmit data via a plurality of communication channels in the form of wireless subcarriers. As another example, each wireless base station of an array of wireless base stations may transmit data via a respective communication channel. As yet another example, a digital subscriber line access multiplexer (DSLAM) may communicate with multiple clients via respective communication channels in the form of twisted-pair cables.

Methods, devices, and systems for dynamic allocation of communication resources


A method for controlling a transmission/reception timing of a BS antenna for TDD wireless communications is provided, in which a control signal and an RF signal are separated from a modulated signal received from a BTS, a TDD synchronization signal is monitored from the received modulated signal, a periodic RF signal is checked from downlink transmission and uplink reception RF signals, an error between the TDD synchronization signal and the periodic RF signal is calculated, and a transmission/reception switching control signal is output according to the error.

In a TDD wireless communication system that distinguishes transmission from reception by time-division of the same frequency, a Transmit/Receive Antenna Switch (TRAS) for switching between a high-power Radio Frequency (RF) transmission signal and a low-power RF reception signal protects a Low Noise Amplifier (LNA) at a receiver by blocking transmit power from the LNA in transmission mode and reduces noise introduced from a transmitter in reception mode. To implement the TRAS function, an RF switch is usually used, of which the switching is controlled based on a TDD synchronization signal. However, it may occur that the transmission/reception timing of the TDD synchronization signal is not identical to that of the RF transmission/reception signal in a BS. Then a downlink RF transmission signal whose power was amplified much may be introduced into the uplink reception path of a reception signal amplification/division module 70 and devices residing in the uplink reception path, such as an LNA may be damaged. To avoid this problem, an isolator is inserted at the output end of the LNA in hardware. However, if the isolator is damaged, the highly power-amplified downlink transmission RF signal may be introduced into the LNA, resulting in damage to the LNA.

Method for controlling transmission/reception timing of base station antenna for TDD wireless communications and base station antenna using the same


Systems and techniques are disclosed for an enhanced automated protocol for secure application testing. An example method includes receiving, via a first component of a system and from a user device, selection of testing information, the testing information including a test device to perform one or more selected test suites, and the test suites being associated with an application. Test suite information is generated via a second component of the system based on the selected test suites, with the first component instructing the second component to generate the testing information according to the particular protocol. The test suite information is provided via the second component to the test device, with the test suite information being provided in response to polling from the test device. Test results are received via the second component, with the test results being routed by the second component to the first component for presentation via the user device.

Applications (e.g., 'apps') are increasingly being relied upon to provide easy-to obtain discrete units of functionality. For example, a mobile device may enable access to an online application store. The application store may include applications from which a user may select. Upon selection, the user's mobile device may then execute the application to provide its associated functionality. Due to the breadth of such applications, the mobile device may provide a platform that enables far-reaching functionality. Additionally, the same applications may be utilized on different devices. For example, an application for editing documents may be utilized on a mobile phone. In this example, a user may additionally utilize the application on a tablet. In this way, the user may easily switch between devices while retaining a similar look/feel, functionality, and so on, across the devices.
It should be appreciated that ensuring an application successfully works across multiple devices requires a substantial amount of testing. Each device may have a unique operating system executing on the device. Thus, the application may have to be designed to work within different guidelines and with different application programming interface (APIs) calls. Additionally, the application may have to work with different versions of devices, operating systems, and so on. While testing of the application may, at least in part, be accomplished using software-based emulators, the applications may still need to be fully tested as working on actual device hardware.
For example, an application may undergo integration testing with respect to different devices. Integration testing may include the testing of different components of an application. It should be appreciated that an application may include native components, such as components which rely upon APIs associated with the devices, and scripting components, such as components which interface with native components. To perform integration testing, different combinations of components may undergo a series of tests to ensure consistency in functionality and performance.

Enhanced automated protocol for secure application testing


Associating subimages is disclosed. A first set of one or more subimages associated with a first image and a second set of one or more subimages associated with a second image are received. It is determined that a first subimage of the first set corresponds to a second subimage of the second set based at least in part on spatial information associated with the first subimage. The first subimage and the second subimage are associated.

Automatic detection processes can be used to find items in an image and can be a powerful tool. For example, a face detection process can detect faces of people in an image. With digital cameras becoming increasingly popular, more and more digital images are being created. Face detection technology enables management of the increasing number of digital images for personal and commercial use.
In some cases, two images are similar to each other. For example, a photographer may take multiple photographs of a group of people. However, it may be difficult for a user to view objects detected from similar images using existing display techniques. In some applications, a screen size may be relatively small, or a face detected in an image may be small with respect to the image. Techniques to assist users in viewing objects detected from similar images may be useful.

Structured comparison of objects from similar images


An austenitic stainless steel with minimized deformation by heating and cooling treatment after cold working, which consists of, % by mass, C: 0.03% or less, Si: 2 to 4%, Mn: 0.1 to 2%, P: 0.03% or less, S: 0.03% or less, Ni: 9 to 15%, Cr: 15 to 20%, N: 0.02 to 0.2%, Nb: 0.03% or less, each of Mo and Cu or a total of Mo and Cu: 0.2 to 4%, and the balance Fe and impurities, and satisfies the following formulas (1) and (2). This steel can also have good weldability when the following formula (3) is also satisfied in addition to the formulas (1) and (2);16.9+6.9Ni+12.5Cu−1.3Cr+3.2Mn+9.3Mo−205C−38.5N−6.5Si−120Nb≧40  (1)450−440(C+N)−12.2Si−9.5Mn−13.5Cr−20(Cu+Ni)−18.5Mo≦−90  (2)8.2+30(C+N)+0.5Mn+Ni−1.1(1.5Si+Cr+Mo)+2.5Nb≦−0.8  (3)                wherein each element symbol in the formulas (1), (2) and (3) represents the content, % by mass, of each element included in the steel.

The present invention relates to an austenitic stainless steel, more specifically, an austenitic stainless steel with minimized deformation by heating and cooling treatment after cold working. The steel is suitable for structural members of automobiles.
Austenitic stainless steels have been used for various structures because of their excellent workability, strength, corrosion resistance, and the like. In most cases, they are cold worked prior to use.
In the austenitic stainless steels, work-induced martensite may generate during cold working depending on their chemical compositions. In order to prevent this, the following invention is disclosed.
Publication of Japanese Unexamined Patent Application Hei-8-283915 discloses an invention relating to an austenitic stainless steel, which has improved workability due to adjusting the chemical composition, which reduces the generation of work-induced martensite, and also due to controlling the crystal grain size, which reduces work hardening. However, in this invention, the deformation by heating and cooling treatment after cold working is not taken into consideration at all.
It is reported that austenitic stainless steels deform when annealed at a relatively low temperature after cold working. Such a deformation is explained with several different indicators such as stacking fault energy and martensitic transformation quantity.
For example, the shrinkages during low-temperature heat treatment of cold rolled austenitic stainless steels of SUS 301 to SUS 310S are reported in the following literatures 1 to 4. However, in these non-patent literatures, the quantity of shrinkage is explained only with the stacking fault energy of the steel. The deformation and weldability, which is necessary for structure, of high-Si austenitic stainless steels containing Cu, Mo and the like has not been examined at all. Improvement of such high-Si austenitic stainless steels is an objective of the present invention.    Literature 1: CAMP-ISIJ, vol. 15 (2002)-559    Literature 2: TETSU TO HAGANE, Vol. 81 (1995), No.5, pp. 65–70    Literature 3: TETSU TO HAGANE, Vol. 81 (1995), No.9, pp. 32–37    Literature 4: TETSU TO HAGANE, Vol. 82 (1996), No.10, pp. 37–42
Publication of Japanese Unexamined Patent Application 2001-323341 discloses a stainless steel plate having high strength and improved flatness, in which shape correction is performed by use of the work-induced martensite during cold working and by use of shrinkage due to the reverse transformation from martensitic phase to austenitic phase in low-temperature annealing. However, this literature describes neither the inhibition of deformation by heating and cooling treatment after cold working nor the weldability necessary for structure.


The invention relates to a display device using the DLP (Digital Light Processing) technology. This invention is in the field of digital cinema and content protection, where camcorder acquisition followed by immediate illegal distribution creates important revenue losses for content owners. According to the invention, the addressing of the display device is modified in order to introduce an anti-copy processing. The display device comprises modulation means for modulating the color or brightness of video data of video pictures received at a first rate and for outputting at a second rate modulated video data, said second rate being a multiple of the first rate, subfield coding means for coding said modulated video data into subfield data, said subfield data being delivered at the second rate, and addressing means for addressing the array with said subfield data at a third rate. Advantageously, the third rate is not a multiple of the first rate.

Visual contents, be they still or moving images, are in general creations which benefit from copyright-related exclusivity guarantees. Their reproduction is in general permitted only within a strongly defined framework which allows for remuneration of authors and their beneficiaries.
In order to ensure that these legal rules are correctly adhered to, numerous systems have been develop to prevent illegal copies or sufficiently impair their quality as to render them unusable.
Within this framework, patent application EP 1 237 369 aims to combat the copying of images by picture-taking during their display, for example with a camcorder in a cinema auditorium. With this aim, it is proposed that the brightness of the pixels of a pattern be modulated around the value to be displayed at a frequency which renders the pattern invisible to the human eye but which generates artefacts on the sequence filmed by the camcorder. This pattern is commonly called anti-copy pattern. The shape of the pattern can be determined so as to inscribe messages of the type "ILLEGAL COPY" which will appear in the images displayed by the camcorder.
In order for the pattern to be invisible to the human eye, the modulation consists in alternating images in which the pattern is bright with images in which it is dark, the mean brightness of the pattern over several images corresponding to that to be displayed in the images in the absence of a pattern. During the display of these images, the eye carries out integration and in fact perceives the mean brightness. This technique may be also applied to the colour of the images by alternating images in which the pattern is more coloured with images in which it is less so, the mean colour of the pattern over several images corresponding to that to be displayed in the absence of the pattern.
In practice, each image of the initial sequence received at 24 Hz is decomposed into several images at N*24 Hz in which the brightness and/or the colour of some parts of the images are modulated to create the anti-copy pattern as indicated above.


Cellulose ethers are described which are useful in compositions for extrusion-molded bodies. In these cellulose ethers the ether substituents are methyl groups, hydroxyalkyl groups, and optionally alkyl groups being different from methyl, the cellulose ether has an MS (hydroxyalkyl) of 0.11 to 1.00, and hydroxy groups of anhydroglucose units are substituted with methyl groups such that [s23/s26−0.2*MS (hydroxyalkyl)] is 0.35 or less, wherein s23 is the molar fraction of anhydroglucose units wherein only the two hydroxy groups in the 2- and 3-positions of the anhydroglucose unit are substituted with methyl groups and wherein s26 is the molar fraction of anhydroglucose units wherein only the two hydroxy groups in the 2- and 6-positions of the anhydroglucose unit are substituted with methyl groups.

Extrusion molding of inorganic masses, such as ceramic-forming materials has been performed by passing a green body or composition, which is obtained by mixing and kneading adjuvants such as organic binders, surfactants, lubricants, and plasticizers with inorganic materials, particularly ceramic-forming materials, through dies having a desired shape into a sheet, a bar, a hollow tube, a rectangular column, a hollow rectangular column, or a honeycomb structure. In particular, the extrusion-molded body in the form of ceramic honeycombs has been in use as a carrier for exhaust gas cleaning catalysts, filters, and heat exchangers in the fields of automobiles and various industries.
A well-known adjuvant is methyl cellulose. It forms strong gels at elevated temperatures. Methylcellulose in the extrusion molding of inorganic masses is desired for improving the wet green modulus and wet green strength of the extruded mass, often colloquially referred to as "green strength" Improved green strength facilitates the extrusion of thin-walled honeycomb structures from ceramic batches and reduces production failures. Unfortunately, the well-known low gelation temperature of methyl cellulose has disadvantages in some processes for extrusion-molded bodies.
U.S. Pat. No. 4,551,295 relates to the extrusion of a plastic ceramic batch into articles of widely-differing profiles and shapes such as, for example, dinnerware and electrical insulators, and especially the extrusion of thin-walled honeycomb structures. The U.S. patent discusses that a methyl cellulose, such as METHOCEL™ A4M cellulose ether having a viscosity of 4000 mPa·s, measured as a 2 wt. % aqueous solution at 20° C. according to Ubbelohde, has a low gelation temperature. According to FIG. 8 of the U.S. patent a sharp rise in extrusion pressure is observed when increasing the extrusion temperature in the range of 23-30° C. The U.S. patent discusses that such rise in extrusion pressure is not observed when using as a binder/plasticizer METHOCEL™ F4M cellulose ether which is commercially available from The Dow Chemical Company and has a viscosity of 4000 mPa·s, measured as a 2 wt. % aqueous solution at 20° C. according to Ubbelohde. METHOCEL™ F4M cellulose ether has a methoxyl substitution of 27.0-30.0 weight percent and a hydroxypropoxyl substitution of 4.0-7.5 weight percent. The U.S. patent suggests using a hydroxypropyl cellulose having a viscosity of 25,000-100,000 mPa·s, measured as a 2 wt. % aqueous solution at 20° C. according to Ubbelohde to permit the use of working temperatures greater than 35° C. in a twin screw extrusion apparatus.
Unfortunately, hydroxyalkyl methylcelluloses are known to have a low storage modulus, compared to methyl cellulose. Hydroxyalkyl methylcelluloses which exhibit a low storage modulus do not form strong gels. High concentrations are needed to form even weak gels (Hague, A; Richardson, R. K.; Morris, E. R., Gidley, M. J and Caswell, D. C in Carbohydrate Polymers 22 (1993) p. 175; and Hague, A. and Morris, E. R. in Carbohydrate Polymers 22 (1993) p. 161). For example, at the same concentration of 2 wt.-%, at elevated temperatures the maximum storage modulus of a METHOCEL™ K4M HPMC is typically less than about 100 Pa, whereas that of a METHOCEL™ A4M methylcellulose is typically above about 1000 Pa. It is concluded that the hydroxyalkyl substituents inhibit intermolecular associations.
In line with the above-mentioned teachings, gel strength is known to be lost with rising hydroxyalkyl substitution of known hydroxyalkyl methyl celluloses. N. Sarkar discusses in the Journal of Applied Polymer Science, 24 (1979), pp. 1073-1087 the thermal gelation properties of methylcellulose and hydroxypropyl methylcellulose. FIG. 9 of the article, which is included as FIG. 1 in the present patent application, illustrates the gel strength of 2 weight-% aqueous hydroxypropyl methylcellulose (HPMC) gels after 4 hours at 65° C. as a function of hydroxypropyl molar substitution. The graph illustrates that gel strength of a HPMC with an MS (hydroxypropyl) of 0.15 is only about one third of the gel strength of methylcellulose (MC).
To resolve the issue of low gel strength of hydroxyalkyl methyl celluloses, European Patent Application EP 1 983 004 discloses a water-soluble hydroxyalkyl methyl cellulose having a molar substitution of hydroxyalkyl groups of 0.05 to 0.1 and a substitution degree of methoxyl groups of 1.6 to 1.9, wherein the hydroxyalkoxyl groups are classified into substituted hydroxyalkoxyl groups having hydroxyl groups of hydroxyalkoxyl groups substituted further with methoxyl groups and unsubstituted hydroxyalkoxyl groups having hydroxyl groups of hydroxyalkoxyl groups not further substituted; and a ratio (A/B) of a molar fraction (A) of the substituted hydroxyalkoxyl groups to a molar fraction (B) of the unsubstituted hydroxyalkoxyl groups is 0.4 or greater. However, it would be desirable to increase the gel strength in another way than only lowering the molar substitution of hydroxyalkyl groups because lowering the molar substitution of hydroxyalkyl groups in hydroxyalkyl methyl celluloses typically leads to an increased fiber content, which is undesirable in some applications where hydroxyalkyl methyl celluloses are used, such as extrusion-molded bodies having a ceramic honeycomb structure.
To optimize the use of cellulose ethers as adjuvants in the extrusion of inorganic masses, such as ceramic-forming materials, it would be desirable to provide new cellulose ethers, particularly new hydroxyalkyl methylcelluloses, which have a higher gel strength than known comparable hydroxyalkyl methylcelluloses.
Moreover, it would be desirable to provide new cellulose ethers which are useful as an adjuvant in inorganic masses to produce extrusion-molded bodies and which provide the produced extrusion-molded bodies with a higher wet green modulus than when known hydroxypropyl methylcelluloses are included in the inorganic mass.

This patent is subject to a terminal disclaimer.


An apparatus for processing a digital image signal includes a pseudo-luminance generator configured to generate pseudo-luminance signals from the image signal. An edge detector detects an edge in the image signal using a part of an interpolated image signal as a luminance signal for a line of the image signal including a pixel subjected to edge detection and using the pseudo-luminance signals for adjacent lines. A color suppressor suppresses pseudo-color present in the chrominance component of the image signal in response to a detected edge. A compensator may be provided to generate a second edge metric relative to the image signal to compensate for an edge detection error occurring in the edge detector. A color suppression coefficient calculator to generate a color suppression coefficient using a first edge metric generated by the edge detector and the second edge metric. Corresponding systems and methods are disclosed.

A digital image signal processing apparatus digitally processes an analog or digital Bayer pattern signal provided from a complementary metal oxide semiconductor (CMOS) image sensor and/or a charge coupled device (CCD) to provide a displayable image signal. Accordingly, the digital image signal processing apparatus operates to restore an original signal as fully as possible from the Bayer pattern signal.
In order to facilitate storage and processing thereof, an image signal may be digitized. Accordingly, the original analog signal may be subjected to analog-to-digital conversion in an image sensor or a digital image signal processing apparatus. As is well known, digitizing is performed by sampling an analog signal. According to sampling theory, if a sampling frequency is not at least double the highest frequency component of the original signal, then aliasing, in which an incorrect frequency signal is output, may occur. To prevent aliasing, a low pass filter is typically used at a position where a signal is input to a digital image signal processing apparatus to attenuate high-frequency components of the input signal. However, the cut-off frequency of the low pass filter may be higher than the sampling frequency, potentially causing aliasing to occur due to high-frequency components of the input signal.
When aliasing occurs, a color component that does not exist in the original image, i.e., a pseudo-color, may appear at or near a high frequency edge of the digitized image. In particular, a pseudo-color may appear as noise in a high-frequency region of the digital image signal in which only a luminance component should be present. In this situation, the outline of an image may appear jagged in a stair-stepping appearance, which may reduce image quality.
FIG. 1 is a block diagram of a conventional digital image signal processing apparatus 100 having a line memory 10 including four lines and using a 5*5 edge detection mask to provide five line signals a−2 to a+2. FIG. 11 illustrates a Bayer signal corresponding to five lines provided through the line memory 10. Hereinafter, a conventional method of processing a digital image signal will be described with reference to FIGS. 1, 11 and 12.
The conventional digital image signal processing apparatus 100 includes a line memory 10 having a plurality of lines LM1 through LM4 to store a Bayer digital signal in line units. An interpolator 12 performs interpolation using Bayer pattern signals simultaneously provided in line units from the line memory 10 to generate interpolated RGB values for each pixel, and a color space converter 13 is configured to convert the interpolated RGB signal to a YCbCr format including a luminance component Y and chrominance components Cb/Cr. A pseudo-luminance generator 11 is configured to generate pseudo-luminance values to be used for edge detection using the Bayer pattern signals provided from the line memory 10. An edge detector 14 detects an edge in the image signal using the pseudo-luminance values, and an edge enhancer 15 enhances an edge of a luminance component signal Y obtained through color space conversion using an output of the edge detector 14. A color suppression coefficient calculator 16 performs a non-linear conversion using edge information provided from the edge detector 14 to calculate a color suppression coefficient, and a color suppressor 17 suppresses pseudo-color components included in the chrominance components Cb/Cr of the converted signal using the color suppression coefficient.
The pseudo-luminance generator 11 calculates a pseudo-luminance value using only green color values, which may primarily influence luminance from among the red, green, and blue (RGB) color values of a pixel.
Since an edge may be considered to be located at a portion of an image where the brightness of pixels changes rapidly, the luminance value Y, which corresponds to the brightness of a corresponding pixel, may be used for edge detection. Conventionally, after a signal is processed by the interpolator 12, i.e., after an RGB value is allocated to each pixel, a Y value of each pixel is extracted and used for edge detection. Since the Y value depends more on the green (G) than the red (R) or blue (B), the G value is typically directly used as the Y value. However, in order to use an interpolated G value as a pseudo-luminance value for edge detection, G values need to be provided for pixels in a window, e.g., a 5*5 window, needed for the edge detection, and, therefore, a line memory having almost the same size as the line memory 10 may be needed to store the interpolated G values for use in edge detection.
In order to reduce the burdens associated with an increase in the density of integration of a digital image processing device, a pseudo-luminance generator 11 as shown in FIG. 1 may be provided. That is, by using a pseudo-luminance generator 11 to generate pseudo-luminance values for use in edge detection, a separate line memory may not be required. For example, if the line memory 10 uses about 50,000 gates, the pseudo-luminance generator 11 may use less than about 1,000 gates, thus providing a significant advantage in terms of size.
FIG. 12 illustrates a 5×5 window, and FIG. 13 illustrates a Bayer pattern for all pixels in the 5×5 window illustrated in FIG. 12. Hereinafter, a conventional procedure of generating pseudo-luminance values YG−2, YG−1, YG, YG+1, and YG+2 will be described briefly with reference to FIGS. 12 and 13.
Usually, two kinds of methods are used to generate luminance. In both methods, a G value may be used as is when a pixel has G color.
In a first method, for example, for a pixel P11, a mean of four pixels P11, P12, P21, and P22, i.e., (P11+P12+P21+P22)/4 is used as a YG value.
In a second method, for example, for a pixel P33 having R color, a mean of two pixels, which are adjacent to the pixel P33 and have a least difference between their G values among a pair of pixels adjacent thereto in a horizontal direction and a pair of pixels adjacent thereto in a vertical direction, is used as a YG value. In other words, if a difference between pixels P32 and P34 is less than a difference between pixels P23 and P43, a mean of the two pixels P32 and P34, i.e., (P32+P34)/2 is used as the YG value.
When the YG value is provided to each line with this method, the edge detector 14 creates a 5×5 or 3*3 window comprised of YG values and detects an edge using the window. Edge detection is performed by generating an edge metric based appropriate G values and comparing the edge metric to a threshold to identify the presence or absence of an edge.
In conventional edge detection techniques, the pseudo-luminance values YG−2 through YG+2 for respective lines are calculated by taking a mean using a Bayer pattern signal, which is not converted into an RGB format through interpolation. Accordingly, the pseudo-luminance values YG−2 through YG+2 may be less accurate than Y values calculated using the color space converter 13 from RGB values that are obtained through interpolation,.
As a result, high-frequency components of an original image may be lost due to inaccurate Y values, and edge detection may increasingly fail. Pseudo-colors may appear at a portions of an image where edge detection fails.

Apparatus for processing a digital image signal and methods for processing a digital image signal


A wiring structure of a semiconductor device may include an insulation interlayer on a substrate, the insulation interlayer having a linear first trench having a first width and a linear second trench having a second width, the linear second trench being in communication with a lower portion of the linear first trench, the first width being wider than the second width, and a conductive layer pattern in the linear first and second trenches.

1. Field of the Invention
Exemplary embodiments of the present invention relate to wiring structures of a semiconductor device, methods of forming such wiring structures, non-volatile memory devices including such a wiring structure, and methods of manufacturing such a non-volatile memory device. More particularly, exemplary embodiments of the present invention relate to wiring structures of a semiconductor device that has an increased contact margin with respect to a contact plug on the wiring structure, methods of forming the wiring structure, non-volatile memory devices including such a wiring structure, and methods of manufacturing such a non-volatile memory device.
2. Description of the Related Art
Generally, memory devices may be classified as volatile memory devices or non-volatile memory devices based on whether the memory devices stores or removes data when current is not provided to the memory device. Examples of volatile memory devices may include erasable programmable read only memory (EPROM) devices, electrically EPROM (EEPROM) devices, flash memory devices, etc. Merits of EPROM and EEPROM are embedded in the flash memory. That is, the flash memory generally uses a process substantially the same as that of the EPROM when data is programmed and the flash memory generally uses a process substantially the same as that of the EEPROM when the data is erased. Further, the flash memory generally has a smaller chip size than those of the EPROM and the EEPROM, and thus, the flash memory may have a higher capacity. Furthermore, information in the flash memory may be immediately renewed through a system.
Flash memories may be classified as a NOR type flash memory or a NAND type flash memory in accordance with constitutions of a cell. A memory cell of the NAND type flash memory may include cell strings in a cell array to which, e.g., sixteen or thirty-two cell transistors are connected. A string selection transistor for selecting strings may be connected to one end of each of the cell strings. Further, a ground selection transistor may be connected to the other end of each of the cell strings.
Gate electrodes of each of the string selection transistors may be connected to each other. The gate electrodes of the string selection transistors may serve as a string selection line (SSL). Further, gate electrodes of each of the ground selection transistors may be connected to each other. The gate electrodes of the ground selection transistors may serve as a ground selection line (GSL).
A common source line may be electrically connected to source regions of the ground selection transistors. The common source line may extend in a direction substantially perpendicular to an extending direction of the cell strings. Further, a contact plug and a bit line may be formed on the common source line so that the contact plug and the bit line may be electrically connected to the common source line.
In the above-mentioned memory cell of the NAND type flash memory, the contact plug must be accurately formed on the common source line. Thus, a process for forming a contact hole may be carried out in advance to precisely expose an upper surface of the common source line through the contact hole.
However, when the contact hole is misaligned during, e.g., a photolithography process for forming the contact hole, the common source line may not be exposed through the misaligned contact hole so that an insulation interlayer on a sidewall of the common source line may be etched. Further, the misaligned contact hole may partially expose an upper surface of a semiconductor substrate adjacent to the common source line. As a result, a short between the contact plug in the misaligned contact hole and, e.g., the exposed upper surface of the semiconductor substrate or a gate of an adjacent transistor may be generated.

Wiring structure of a semiconductor device, method of forming the wiring structure, non-volatile memory device including the wiring structure, and method of manufacturing the non-volatile memory device


Methods related to Generalized Mutual Interdependence Analysis (GMIA), a low complexity statistical method for projecting data in a subspace that captures invariant properties of the data, are implemented on a processor based system. GMIA methods are applied to the signal processing problem of voice activity detection and classification. Real-world conversational speech data are modeled to fit the GMIA assumptions. Low complexity GMIA computations extract reliable features for classification of sound under noisy conditions and operate with small amounts of data. A speaker is characterized by a slow varying or invariant channel that is learned and is tracked from single channel data by GMIA methods.

Signal detection in continuous or discrete time is a cornerstone problem in signal processing. One particularly well studied instance in speech and acoustic processing is voice detection, which subsumes a solution to the problem of distinguishing the most likely hypothesis between one assuming speech presence and a second assuming the presence of noise. Furthermore, when multiple people are speaking, it is difficult to determine if the captured audio signal is from a speaker of interest or from other people. Speech coding, speech/signal processing in noisy conditions, and speech recognition are important applications where a good voice/signal detection algorithm can substantially increase the performance of the respective system.
Traditionally, voice detection approaches used energy criteria such as short-time SNR estimation based on long-term noise estimation as for instance described in "[22] Srinivasan K, Gersho A (1993) Voice activity detection for cellular networks. In: IEEE Speech Coding Workshop, pp 85-86", likelihood ratio test of the signal and exploiting a statistical model of the signal as described in "Cho Y, Al-Naimi K, Kondoz A (2001) Improved voice activity detection based on a smoothed statistical likelihood ratio. In: International Conference on Acoustics, Speech and Signal Processing, IEEE, Los Alamitos, Calif., vol 2, pp 737-740", or attempted to extract robust features (e.g., the presence of a pitch as described in "[9] ETSI (1999) Digital cellular telecommunication system (phase 2+); voice activity detector VAD for adaptive multi rate (AMR) speech traffic channels; general description. Tech. Rep. V.7.0.0, ETSI", the formant shape as described in "[15] Hoyt J D, Wechsler H (1994) Detection of human speech in structured noise. In: International Conference on Acoustics, Speech and Signal Processing, IEEE, vol 2, pp 237-240", or the cepstrum as described in "[13] Haigh J, Mason J (1993) Robust voice activity detection using cepstral features. In: IEEE Region 10 Conference TENCON, IEEE, vol 3, pp 321-324") and compare them to a speech model. Diffuse, non-stationary noise, with a time-varying spectral coherence, plus the presence of a superposition of spatially localized but simultaneous sources make this problem extremely challenging when using a single sensor (microphone).
Not surprisingly, during the last decade researchers have focused on multi-modality sensing to make this problem tractable. Multiple channel voice detection algorithms take advantage of the extra information provided by additional sensors. For example in "[21] Rosca J, Balan R, Fan N, Beaugeant C, Gilg V (2002) Multichannel voice detection in adverse environments. In: European Signal Processing Conference" the mixing model is blindly identified and a signal is estimated with maximal signal-to-interference-ratio (SIR) obtainable through linear filtering. Although the filtered signal contains large artifacts and is unsuitable for signal estimation it was proven ideal for signal detection. Another example is the WITTY (Who is Talking to You) project from Microsoft as described in "[24] Zhang Z, Liu Z, Sinclair M, Acero A, Deng L, Huang X, Zheng Y (2004) Multisensory microphones for robust speech detection, enhancement and recognition. In: International Conference on Acoustics, Speech and Signal Processing, IEEE, pp 781-784", which deals with the voice detection problem by means of integrated heterogeneous sensors (e.g., a combination of a close-talk microphone and a bone conductive microphone).
Even further, multi-modal systems using both microphones and cameras have been studied as described in "[17] Liu P, Wang Z (2004) Voice activity detection using visual information. In: International Conference on Acoustics, Speech and Signal Processing, Montreal, Canada, vol 1, pp 609-612".
Improved and novel methods and systems to perform voice (or signal) detection for the source of interest with the reliability of multi-modal approaches such as WITTY but in the absence of additional sensors such as a bone conducting microphone are beneficial but are believed to be currently not available and are required.

Channel detection in noise using single channel data


A stuck drill bit having a KCS shank can be removed using an article with a body structure. The body structure has an opening that fits onto the shank, and an inward-facing surface around the opening is at least partially complementary to the surface of the shank. The surfaces engage sufficiently that rotary manual force is transferred from the inward-facing surface to the surface of the shank.

Various methods and apparatus are known for producing holes in durable material. Among these, rotary drills and hammer drills employ drill bits that include cutting and/or breaking surfaces arranged to remove a portion of the substrate material as the drill bit is advanced. In certain drill bits, one or more helical features, such as helical grooves or channels, serve to withdraw the removed substrate material away from the cutting and/or breaking surfaces. In some cases, the helical features extend over much of the length of the drill bit so that removed material is extracted out of the substrate material altogether.

The United States of America as represented by the Secretary of the Navy


A steering system for non-track vehicles, and a method of controlling a steering transmission ratio of a non-track vehicle, in which the steering transmission ratio between the adjusting paths of the steering handle and the steered wheels is changed corresponding to a characteristic diagram as a function of the driving speed as well as of the adjusting paths of the steering handle or the steered wheels.

This invention relates to a steering system for a non-track vehicle having a steering handle or a steering wheel, and at least one steered vehicle wheel operated thereby, with a variable steering transmission ratio existing between the adjusting movement of the steering handle and the adjusting movement of the steered wheels which changes with the steering angle. This invention also relates to a method of controlling a steering transmission ratio of a non-track vehicle
In the case of steering systems of passenger cars, the steering kinematics, as a rule, are constructed such that the steering becomes more direct with an increasing steering angle (the angle of the steered wheels with respect to a straight-ahead position). In other words, the steering transmission ratio between the adjusting movement of the steering handle and the adjusting movement of the steered wheels becomes smaller with an increasing steering angle. For example, in the case of a rack and pinion steering, this can be achieved by varying the base tangent length over the path of the steering rack.
In the case of conventional vehicle steering systems, the steering handle and the steered wheels are mechanically coupled with one another in a securely fixed manner in order to ensure a high safety under all conditions. U.S. Pat. No. 4,658,927 and U.S. Pat. No. 5,072,083 show known vehicle steering systems.
However, control systems without a mechanically fixed coupling are known in principle. For example, in airplanes, the horizontal stabilizers and landing flaps can also be operated by way of a control system without direct mechanical coupling. The position of the control handle operated by the pilot is sensed to generate a desired position signal having a value corresponding to a desired position of the horizontal stabilizers and landing flaps. The desired position signal value is read by a control system, which in turn sends out signals to motors which adjust the horizontal stabilizers and landing flaps to the desired position, as a function of a comparison between the desired position and the actual position. This concept, which is also called "fly by wire", has become so safe and developed that it is also used in passenger planes.
It is an object of the invention to provide an advantageous steering system for a non-track vehicle.
This and other objects have been achieved according to the present invention by providing a steering system for a non-track vehicle, and a method of controlling a steering transmission ratio of a non-track vehicle, having at least one steered wheel operated by a steering handle, the steering handle having a center position corresponding to a straight-ahead position of the steered wheel, the steering handle being movable between the center position and an adjusting position to move the steered wheel between the straight-ahead position and a steering angle, wherein a steering transmission ratio between an adjusting movement of the steering handle and an adjusting movement of the steered wheel is controlled according to a characteristic diagram at least as a function of the adjusting position of the steering handle or the steering angle of the steered wheel and of the vehicle speed.
According to the present invention, the steering transmission ratio between the adjusting movements of the steering handle and the steering angles of the steered wheels are varied at least as a function of the steering angle and the driving speed according to a characteristic diagram.
It is preferable that the steering handle and the steered wheels are operatively connected only by way of a controlled system which generates a desired steering angle value as a function of the position of the steering handle, and which uses at least one motor to adjust the steering angle of the steered wheels, the motor being controlled by the system to adjust the steering angle as a function of a comparison between the desired position and the actual position.
Since there is no direct mechanical coupling between the steering handle and the steered wheels, the steering transmission ratio between the steering handle and the vehicle wheels may be designed in a very flexible, parameter dependent manner, independently of the kinematics of the adjusting elements of the steered wheels. Furthermore, the present invention advantageously reduces the steering system space requirements in the vehicle, and allows increased flexibility in the design and layout of not only the steering system components themselves, but of other vehicle components, since a direct mechanical coupling between the steering handle and the steered wheels is no longer necessary.
According to one aspect of the present invention, the steering ratio between the steering handle and the steered wheels is advantageously controlled to be more direct, i.e., lower, in the case of larger steering angles as well as at low vehicle speeds.
In addition, the automatic change of the steering transmission ratio can easily be carried out such that, when the steering handle is held still, the respective adjusted steering angle of the steered wheels can also not change or change only in a delayed manner during changes of the parameters changing the steering transmission ratio.
In order to ensure that the straight-ahead position of the steered wheels always coincides with a center position of the steering handle, it is provided that, after a steering adjustment, the steered wheels will always reach the straight-ahead position exactly when the steering handle returns into the center position.
These and other objects, features and advantages of the present invention will become more readily apparent from the following detailed description when taken in conjunction with the accompanying drawings.


A catalyst system and process for the polymerization of cyclic olefins, such as dicyclopentadiene, are disclosed. The catalyst system contains a transition metal hydrotrispyrazolylborate complex having the formula: EQU Tp--M--L.sub.3. wherein Tp is a hydrotrispyrazolylborate ligand, M is tungsten or molybdenum, and L is independently a ligand selected from the group consisting of oxo, phenoxy, alkoxy, and halides, provided that at least one L is a halide, and a co-catalyst.

Cyclic olefins are subjected to ring-opening metathesis polymerization to produce thermoplastic and thermoset polymers having physical properties which make them suitable for structural and electronic applications, such as molded plastic items and electrical laminates. Such polymerizations are commonly carried out in reaction injection molding (RIM) processes, in which a metathesis catalyst and a cyclic olefin monomer are charged to a heated mold, and polymerization of the monomer and forming of the polymer into the desired shape are carried out simultaneously in the mold.
In such RIM processes, it is important that the polymerization reaction occur rapidly and with as complete incorporation of the charged monomers as possible. For example, the presence of unreacted monomers in molded polydicyclopentadiene has been found to result in a molded part with an unpleasant odor, and less than optimum physical properties. Finding a RIM process that reacts in as short a cycle time as possible and at mold temperatures at or near room temperature is economically desirable. Further, it is desirable in such a system to have catalyst systems which are thermally stable and resistant to reaction with oxygen and water.
For most cyclic olefin metathesis catalyst systems, the presence of reactive materials such as water and oxygen should be avoided because they foul the polymerization process. As a result, it is usually necessary to thoroughly dry the cyclic olefin monomers prior to contact with the polymerization catalyst, and to conduct the polymerization in an inert environment.
A tungsten(VI) oxo alkylidene complex with an aluminum chloride co-catalyst is disclosed in an article by J. A. Boncella et al., J. Am. Chem. Soc., 113, 7066-7068 (1991) as an air and moisture-stable ring opening metathesis catalyst system However, alkylidene or alkylidyne complexes, e.g. W.dbd.CR or W.dbd.CR, are generally difficult to manufacture and expensive. Therefore, it is desirable to produce a simpler and less expensive, air and moisture-stable ring opening metathesis catalyst system.
It is therefore an object of the present invention to provide an improved air and moisture-stable ring opening metathesis catalyst system.

Catalyst system for olefin polymerization


An apparatus includes an integrated circuit having at least one input/output terminal comprising copper formed thereon. A metal cap layer overlies an upper surface of the at least one input/output terminal. A substrate includes at least one conductive trace formed on a first surface, and a metal finish layer overlies a portion of the at least one conductive trace. A lead free solder connection is disposed between the metal cap layer and the metal finish layer, and a first intermetallic compound is disposed at an interface between the metal cap layer and the lead free solder connection. The lead free solder connection has a copper content of less than 0.5 wt. %, and the first intermetallic compound is substantially free of copper.

A current common requirement for an advanced electronic circuit and particularly for circuits manufactured as integrated circuits ("ICs") in semiconductor processes is the use of a solder bump, solder ball or solder column connections. In a "flip chip" approach to packaging and interconnections, the solder bumps are used to couple the external terminals of a monolithic integrated circuit (which may be a silicon substrate with active or passive circuit elements and connections formed upon it, or other substrate materials including gallium arsenide (GaAs) and silicon on insulator (SOI), and silicon germanium (SiGe) may be used) to a package substrate or circuit board. These integrated circuit devices may have tens or hundreds of input and output terminals for receiving, and sending, signals and/or for coupling to power supply connections. In some IC designs the terminals are placed at the periphery of the integrated circuit and away from the active circuitry. In more advanced and complex integrated circuits, the terminals may be placed over the active area and lie over the active devices. In memory ICs, sometimes a center pad arrangement is used.
In a "flip chip" application, the integrated circuit (IC) is sometimes mounted face down (flipped). Terminal openings are formed in a protective insulating layer, called a passivation layer that overlies the face of the device. The input/output terminals are exposed and solder bumps, solder columns or solder balls are placed on these terminals, usually referred to as pads or lands, which may be formed as columns of conductive material extending away from the surface of the integrated circuit. The solder balls are then used to form the external connections to the integrated circuit. These solder balls may be provided already formed on the completed integrated circuit, using a "wafer scale" approach, or, may be added later after the devices are singulated into individual devices called "dice", or even disposed on a substrate or circuit board, and the integrated circuit then aligned with these balls and carefully placed on it. In any case, a thermal solder reflow process is typically used to complete the solder connection between the flip chip integrated circuit, and a substrate, film, printed circuit board or even another silicon device. In thermal reflow the solder bumps, balls, or columns form a permanent mechanical and electrically conductive connection between the terminals of the integrated circuit and the substrate. The combined flip chip IC and substrate may then be packaged as a single integrated circuit. Alternatively, in a multiple chip module form, the flip chip may be combined with other integrated circuits which may also be "flip chips" or wire bond connections may be used. For example sometimes memory devices such as FLASH nonvolatile devices, and processors that would use the FLASH device for program or data storage, are combined in a single packaged device. IC devices may be stacked vertically, or placed alongside one another using a larger substrate or circuit board.
Recently the semiconductor industry has been moving to "lead (Pb) free" packaging and device connector technology. This trend increasingly results in the use of lead free solder bumps and lead free solder balls to form connections with integrated circuits and packages. These lead free solder materials are formed of tin and tin alloys which may include, for example, silver, nickel, copper and other metals. The use of lead free solder balls is safer for the environment, safer for workers in the industry and safer for consumers than lead based solder bumps or solder balls. However, the quality and reliability of the final solder connections formed has not always been as great as desired. During thermal cycle (TC) testing, for example, cracks in the completed solder connections have been observed. A typical thermal cycle test will perform 500 thermal cycles (TC 500) ranging from the minimum specified temperature (typically −55 degrees Celsius) to the maximum specified temperature (typically +125 degrees Celsius), and then the solder connections may be inspected. Often following TC500 testing using conventional solder lead free solder connections, ball cracks are found. Ball cracks are an indicator that during actual use in an application, a solder connection is going to fail by pulling apart. Clearly this is unacceptable in a useful product.
Further, recent advances in interconnection technology for integrated circuit have caused a transition from aluminum or aluminum alloy conductors used within the integrated circuit and extending to the terminals, to copper based interconnect technologies. Often copper conductors are formed over the substrate using a damascene or dual damascene approach. In this technology, a trench or trench and via combination is formed in an insulation dielectric material that forms inter-layer dielectric (ILD) or inter-metal dielectric (IMD), a seed layer of copper or copper alloy is formed within the trench, electroplating or electroless chemical deposition (ECD) is used to fill the trench and/or via opening with the copper based interconnect material, and sometimes a chemical mechanical process (CMP) tool is used to mechanically and chemically abrade any excess copper material above the surface of the trench to form a planar surface at the top of the trench or via. In this way the pattern of the trench in the dielectric finally determines the pattern of the conductors. Many levels of interconnect may be formed above the transistors and active devices, which are typically formed at the surface of the underlying semiconductor substrate. The interconnect material of copper or copper alloy may extend to the terminal pads or ball lands or columns of the integrated circuit, and in such a conventional case copper or an alloy of copper is the material that the solder bumps or balls would be then be deposited upon.
TC500 tests and analysis of lead free solder balls or bumps formed on copper pads indicate that the use of copper as a metallization material at the solder ball terminals of the integrated circuit and/or on the trace of the corresponding circuit board that receives the flip chip integrated circuit may cause the balls to exhibit ball cracks. During solder reflow, which is a thermal process, an intermetallic compound (IMC) is formed within the solder ball between the integrated circuit terminal, which is a copper pad or column, and the solder materials. However if the ball does not adhere well at the interface between the solder and the IMC, then ball cracks are likely to occur.
Accordingly, methods and apparatus for packaging integrated circuits and for forming low resistance electrical connections to circuit boards that form robust and high quality electrical and mechanical connections, while using lead free solder materials, are needed.

Apparatus for lead free solder interconnections for integrated circuits

Taiwan Semiconductor Manufacturing Company, Ltd.


Improved techniques are provided for managing and optimizing network resources and spectrum access in a Self-Organizing Network (SON). A Spectrum Access System (SAS) collects network-related information from a plurality of network sources, such as base stations and user equipments (UEs), to perform optimization and organization across different networks, network operators, and network technologies. In some embodiments, the SAS may use the network information and a Radio Environment Map to optimize TDD synchronization in the SON. In other embodiments, the SAS may use the network information to populate a global Neighbor Relation Table. The SAS also may use the network information to optimize one or more network parameters, such as Physical Cell Identities or Root Sequence Indexes, antenna parameters, transmit power levels, handover thresholds, channel assignments, and so on, for use in the SON. Advantageously, the SAS's optimized network parameters may be used to improve network performance, reduce signal interference, and adjust to network failures in the SON.

Radio frequency (RF) spectrum is the foundation for many wireless communications systems in use today, including radar and cellular communications systems. Specified frequency ranges, sometimes identified as bands or channels, in the RF spectrum may be allocated for use by different entities, for different purposes, or in different geographic locations. As used in this disclosure, "spectrum" refers to any frequencies, frequency bands, and frequency channels in the RF spectrum that may be used or allocated for wireless communications.
Because the available RF spectrum is finite, frequency allocations in the spectrum are highly valued and often highly regulated. In the United States, for example, the Federal Communications Commission (FCC) and the National Telecommunication and Information Administration (NTIA) regulate and manage spectrum allocations, allotments, and assignments. Frequency allocation is the process by which the entire RF spectrum is divided into frequency bands established for particular types of service. These frequency allocations are then further subdivided into channels designated for a particular service or "allotment." Assignment refers to the final subdivision of the spectrum in which a party gets one or more frequency assignments, in the form of a license, to operate a radio transmitter on specific frequencies within a particular geographic location.
The system of spectrum allocation, allotment, and assignment is failing to keep pace with the increasing demand for spectrum. There is therefore a need to improve how the available spectrum can be efficiently allocated, allotted, and assigned in the face of growing demand. Unless otherwise noted, "allocation" is used in the present disclosure to generally refer to the process by which spectrum is allocated, allotted, and assigned to licensed users.
In view of this increasing demand for spectrum, a dynamic spectrum access (DSA) system may be used to share available spectrum among multiple users. A DSA system, for example, may include a Spectrum Access System (SAS) that manages access to a shared spectrum, such as the 3.5 GHz band recently made available for commercial use in the United States. In another example, a DSA system may be used to share access to unlicensed spectrum, such as TV Whitespace. Coordinating and managing multi-user access to a shared spectrum present challenges in a DSA system.
There has been research and development of computer-automated techniques for the optimization and organization of spectrum allocation in standalone wireless networks, e.g., Self-Organizing Network (SON) techniques in 3rd Generation Partnership Project (3GPP) networks. A SON may comprise one or more interconnected standalone networks, e.g., sharing access to at least one SAS. These standalone networks typically use a single radio access technology, such as described in the 3GPP standards for Long Term Evolution (LTE). Further, these networks are usually managed by a single operator, e.g., Verizon or AT&T, which has an exclusive license to use a portion of spectrum in a geographical area.
As wireless demands grow, shared spectrum usage is becoming more common, e.g., in Television Whitespace (TVWS) bands and in the 3.5 GHz Federal band. In these environments, a SAS may control spectrum access among users assigned to different priority levels (or "tiers") of spectrum-access privileges. The SAS may implement spectrum management policies for users in each tier. For example, the SAS may be configured to protect spectrum usage by higher-priority "primary users" in shared bands from harmful interference that would result from communications by lower-priority "secondary users." As used herein, a "user" may refer to a user equipment (such as a mobile phone) or a person using a user equipment as will be apparent in context. In many cases where there are relatively few primary users, spectrum usage by primary users is low, so secondary users can dominate overall resource usage. Nonetheless, in regions with primary users, the SAS should ensure that any spectrum allocations to secondary users will not create unacceptable levels of interference with the primary users.
To assist the SAS with spectrum management, base stations serving secondary users are often required by regulation (e.g., FCC requirements) to share their operating parameters (e.g., location, antenna characteristics, desired operating power, air interface technology, requested data rates) and measurements (e.g., neighboring base station interference, overall interference, bit/block/frame error rates, latencies, buffer status) with the SAS. Secondary users may also opt to share operating parameters and measurements with the SAS, since such sharing may result in improved secondary user performance.
The SAS may employ a Radio Environment Map (REM) to manage spectrum access in one or more wireless networks. The REM describes the propagation environment between each pair of devices (e.g., base stations or mobile users) in the overall shared spectrum system. A REM can be as simple as a table of location, time, and energy detected. It may include items such as, but not limited to, location, time, day, strength of signal, whether users are mobile and when they are roaming, travel directions, and so on. This information can be combined with geographic data such as terrain, tree cover, season of the year, elevation, potential tall buildings, and many other possible relevant items that can affect radio signals. The REM may be used to track historical and geo-located spectrum data. For example, the REM may reflect that every day at 5 PM at a major office park, cell phone usage peaks as people leave from work to head home. However, at 6 PM, there may be little cell phone usage.
The SAS can create an accurate and high-resolution REM because it can leverage powerful and distributed processing (e.g., cloud-based processing instances) and large databases (e.g., building data, floor plans, clutter models, terrain models, base station and mobile user models) for propagation and interference modeling, and may apply machine learning based on measurements to refine these models. The SAS can use its REM to create a global and precise view of the shared spectrum environment.
It is desirable that the SAS manages multi-user spectrum access in a manner that minimizes signal interference between the users, base stations, and other devices communicating in the network. Undesired interference may result when multiple devices transmit at the same time, for example, in a Time Division Duplex (TDD) system. TDD operation is proposed for many shared spectrum applications given the need for secondary-user uplink and downlink operation in a single frequency range. TDD operation generally involves the use of fixed-duration frames which include uplink and downlink time slots. For example, time division LTE (TD-LTE) uses 5 ms or 10 ms frames containing ten subframes (each with two time slots) that can be designated for uplink or downlink use. The uplink subframes are used for mobile users to communicate with the base station, whereas the downlink subframes are used by the base station to communicate with the mobile users. Other TDD systems may employ different frame structures, e.g., containing different configurations of subframes and/or time slots. As used herein, a "subframe" may contain one or more time slots and is not limited to any particular implementation.
A significant concern with TDD operation is interference caused by unsynchronized base-station transmissions from other operators. A base station's transmission power is typically much larger than the transmission power of the mobile users. As a result, in an uplink transmission from a mobile user to a target base station, interference from another base station's transmissions can dwarf the mobile user's signal at the target base station's receiver. Such interference can be caused by base stations operating on the same frequency channels or on channels that are not sufficiently separated in frequency (e.g., base stations operating in adjacent frequency channels 101 and 102 as shown in FIG. 1).
Single operator networks typically resolve this issue by having synchronized TDD networks where each base station transmits in the same time slots. FIG. 2 illustrates frames 201A and 201B for communicating with base stations 202A and 202B, respectively, with synchronized uplink ("U") and downlink ("D") subframes 203, including special ("S") subframes that provide a guard interval between transitions from D to U subframes. The synchronized uplink subframes are reserved for mobile-user transmissions. Therefore, during an uplink subframe, a base station will only receive signals from mobile users, avoiding interference from other base stations. This avoids the severe interference that would result if the base stations were uncoordinated, e.g., if some base stations were transmitting while others were receiving.
Synchronization is complicated because some networks desire a larger portion of the TDD frame reserved for downlink transmissions. For example, some networks may predominantly support mobile users desiring downlink video streaming. In contrast, other networks may support symmetric uplink traffic and downlink traffic, e.g., voice networks. Air interfaces such as WiMAX and LTE provide predetermined TDD frame configurations, with known distributions of uplink and downlink subframes and/or time slots, and allow the network (e.g., via static or dynamic configurations) to select a known TDD configuration with a given frame structure to accommodate expected traffic load for each network.
Further complicating TDD network synchronization is that some base stations may lack the ability to determine accurate timing. Frame timing is typically achieved using GPS, Precision Time Protocol (PTP), or network-listen capabilities at the base station. However, some base stations may lack such timing capability and, hence, these base stations cannot align the beginning of their TDD frames with other base stations.
In scenarios with multiple networks, operators, and/or air interfaces, it is difficult to provide TDD network synchronization in shared frequency channels. Shared channel networks may lack interfaces between them, making it difficult for them to share the network parameters and measurements necessary for TDD network synchronization. In addition, networks employing different radio interface technologies (e.g., WiMAX, LTE) may not have TDD frame sizes and configurations that can be aligned without significant uplink/downlink conflicts. Other shared-channel base stations may not have accurate timing capability.

Spectrum access optimization for self organizing networks


The invention relates to a process for producing spherical, non-fibrillar cellulose particles with a particle size in the range of from about 1 μm to about 400 μm from a solution of cellulose in which the solution is cooled down to below its solidification temperature wherein it is flowing freely, the solvent is washed out, the solidified cellulose solution is disintegrated to form cellulose powder comprising particles, and the disintegrated and washed out particles are dried. The invention also relates to the cellulose powder and particles made in accordance with the process of the invention.

1. Field of the Invention
The present invention relates to a cellulose powder of spherical, non-fibrillar cellulose particles and a process for the production of this.
2. Description of Related Art
The applications for cellulose powder are diverse and range from the pharmaceutical sector to the construction industry. Cellulose powders can be found in the laboratory as a chromatography column filler as well as in large-scale technical processes as auxiliary filter materials. In the food stuff and cosmetics industry they are widely used as auxiliary and carrier substances. In general a trend is noticeable that there are attempts to replace inorganic powders (e.g. of silica) with cellulose powders (O. Schmidt, "washing filtration of wine: with kieselgur or cellulose", The German Wine Magazine, pp. 29-35, 2004).
Cellulose powders are mainly obtained by preparing and grinding pulp or even wood and annual plants. As a result of an additional hydrolysis step, so-called microcrystalline cellulose (MCC) can be obtained. FIG. 1 shows the production of cellulose powders out of cellulose in diagram form in accordance with the state of the art.
Depending on the complexity of production, powders of different qualities (purity, size, etc.) are obtained. What all these powders have in common is that they reveal a fibrous structure since natural cellulose has a pronounced tendency in any order of magnitude to form fibrous structures like this. Likewise MCC, which is also described as spherical, is consisting of crystalline fiber fractions.
Depending on their microstructure, structure types of the cellulose can be differentiated, in particular cellulose-I and cellulose-II. The differences between these structural types can be determined by radiography and they are described in detail in the scientific literature.
All of the powders described above are consisting of cellulose I. There are a large number of patents for the production and application of cellulose-I-powders. Numerous technical details are also patented in these e.g. with regard to grinding. As described above, cellulose-I-powders are of a fibrous nature which is a hindrance for a number of applications. Thus, for example, suspensions of powders of this kind have a viscosity which depends to a considerable extent on the shear strain. In the same way fibrous powders often display a limited pourability since the fibers can get caught up.
Cellulose powders on the basis of cellulose-II can be found on the market. Cellulose powders with this structure can either be obtained from a solution (mostly viscose) or via the disintegration of cellulose-II-powders (e.g. cellophane). In the same way very fine powders are procurable but only in small quantities (10 μm and less).
U.S. Pat. No. 5,244,734 describes the production of spherical particles with diameters of lower than 20 μm from a viscose dispersion.
WO 99/36604 describes fibrous particles which are obtained from the regeneration of viscose with the highest possible shear strain. For example a stream of 500 ml/min of a diluted viscose solution with a cellulose concentration of 1 to 4 weight percentage is led through a 3 mm nozzle into a stirred precipitation bath. This results in fibrous, fibrillar particles due to the high shear strain and the low cellulose concentration.
WO 2007/003699 describes the production of cellulose particles as a result of the regeneration of a cellulose solution in an acid (e.g. by spraying or mixing) with a particle size of preferably 0.05-10 μm. The production of cellulose solution is performed by the enzymatic treatment of the pulp followed by a reaction with an alkali. The cellulose particles are used as a filling material and coating pigment for paper since they are light and eco-compatible, as a cellulosic powder for the food stuff industry as well as for the pharmaceutical industry. One variant described is the modification of cellulose before or after regeneration e.g. via acetylation and the increase in porosity by adding substances which dissolve in these regeneration conditions.
WO 2007/003697 describes the coating of cellulose particles (0.05-10 μm) with substances which disperse light (e.g. silicates, titanium oxide). These particles are likewise used as a filling material and may be useful as a coating pigment for paper and carton.
According to WO 2006/034837, cellulose particles with a length of preferably 50 μm and a thickness of 1 μm are produced in water by exerting shear forces on a suspension of a starting product containing cellulose. These are to be used as a ceramic aggregate for paper, carton and coating colors to increase the tenacity, improve the print image, increase the color intensity and as a carrier material for other substances. These cellulose particles are fibrous and/or fibrillar.
The production of cellulosic micro particles for cosmetic applications via the incorporation of powder-like substances in viscose can be found in JP 63092603. In this respect a dispersion is formed of viscose, inorganic filling material and a water-soluble anionic, high molecular weight substance. The coagulation is, for example, produced by heating. There are no precise details about the size of the cellulose particles obtained.
WO 93/13937 describes the production of cellulose balls with a diameter of preferably lower than 25 μm with a dense surface which reveals no pores, scratches or anything similar: first of all an emulsion is made of viscose in oil. The coagulation takes place for example in water-free, alcoholic salt solutions. Finally washing takes place with concentrated salt solutions containing alcohol to prevent swelling and then this is regenerated with acid solutions containing alcohol. The particles produced in this way are applied in chromatography particularly as carrier materials, so-called carriers for ligands (enzymes, antibodies, peptides, proteins). Due to the dense surface of the ball-shaped cellulose particles, no interfering diffusion processes occur.
In U.S. Pat. No. 5,196,527 the production of porous, ion-exchanging, ball-shaped, e.g., oval, cellulose particles with a size of 3-400 μm is described using the following steps: first of all coagulated viscose particles are made by forming a dispersion which contains cellulose xanthate and finally coagulating the viscose parts as a result of heating or with the help of a coagulation reagent. These viscose parts are regenerated by an acid or via a crosslinking followed by regeneration. As a result of the crosslinking, a high pressure resistance is attained in the particles. In a final step, ion-exchanging groups are introduced to the cellulose molecule. These cellulose particles have a cellulose-II-structure and an x-ray crystallinity of 5-50%, and preferably 20-40%.
These particles are also used in chromatography as well as for cleaning and separating different substances. If the cellulose particles are to be used as carriers, then certain ligands are introduced instead of ion-exchanging groups e.g., antibodies to separate antigens and/or peptides to separate enzymes.
U.S. Pat. No. 5,026,841 deals with the production of porous, ball-shaped cellulose particles with a preferred particle size of 5-80 μm. To this end a cellulose ester of an aromatic carboxylic acid, which is dissolved in an organic solvent, is introduced to an aqueous solution of an anionic tenside while stirring vigorously, the organic solvent is removed, the parts are isolated and finally the carboxylic acid groups are separated. These particles are used as filling materials, carriers for filtration, cleaning, adsorption, carriers, to set inorganic or organic materials as well as in the form of carriers for enzyme and for protein immobilization and cleaning.
KR 950000687 describes the production of a cellulose powder (1-20 μm) for cosmetic products of Ramie fiber according to the following process: Treatment with alkaline hypochlorite solution, washing, dispersing in water and finally spray drying.
JP 2006028452 describes the production of a cellulose solution as a pouring aid for powder-shaped food stuffs e.g., common salt, whereby 50% of the parts possess a particle size of between 1-50 μm.
According to U.S. Pat. No. 4,415,124, a micro powder of cellulose is produced by reinforcing/condensing, followed by grinding (at least 90% of the parts with a particle size of lower than 125 μm). The particles received are used as an additive for mortar, plaster masses, wallpaper paste, filling material for molding mass and plastics as well as in the form of carrier materials in the pharmaceutical industry.
EP 1693402 describes, among other things, the production of a cellulosic body with a preferred size of 1 μm-5 mm, preferably 10 μm-500 μm of porous cellulosic parts (also regenerated). In one variant, cellulosic parts are distributed in an alkaline medium which contains a binder (e.g., waterglass). The suspension is converted in droplet form and finally coagulated in a corresponding coagulation solution whereby the cellulose particles join so that intermediate spaces are left. These particles are used as carriers to mobilize enzymes, as carriers or a matrix for adsorption or as cosmetic additives. The advantages are the high mechanical resistance and the high throughput rates which are possible.
U.S. Pat. No. 4,659,494 describes the production of a powder to clean carpets which contains cellulose powder with a particle size of preferably 5-50 μm as an adsorption agent. No more details are given of the production of the cellulose powder but it would appear to be obtains as a result of disintegrating pulp.
Viscose processes which proceed via the intermediate stage of cellulose xanthate are not desirable nowadays due to the manifold environmental burdens, among other things, with sulphurous waste gases which require complex waste gas purification in their production.
Starting from viscose technology WO 02/00771 and U.S. Pat. No. 6,174,358 utilize NMMO as an alternative solvent for the production of cellulose particles. However, both patents deal with fibrillar and not spherical particles.
According to WO 02/00771 cellulose particles are made by dispersing a cellulose solution (of cellulose or cellulose derivatives, solvent acetone, N-methylmorpholine-N-oxide, aqueous caustic lye of soda, etc.) in a precipitation medium. Additives such as cationization agents or filling materials may also be contained in the solution. Dispersing is done via the shear stress produced with the help of a refiner.
DE 19755353 describes a similar method whereby a solution of cellulose in NMMO is formed to a jet which is divided into individual segments by means of rotating cutting beams. The solution parts are intercepted in a dispersion medium. The pearl-shaped cellulose parts are then received by cooling down the dispersion or by precipitating with a precipitation agent. The process is used to produce porous pearl celluloses with a particle size of 50-1000 μm which are used as separation and carrier materials for medical and diagnostic purposes, as adsorber materials e.g., for blood detoxification and as cell culture carriers.
DE 10221537 describes the production of hybridic molded bodies with a size of 1-1000 μm in which polysaccharide solutions containing additives are dispersed in an inert solvent so that solvent drops form. This is preferably cellulose dissolved in N-methyl morpholine-N-oxide-monohydrate. The additives are for example ceramic powders. Finally the dispersion developed from this is cooled down whereby the solvent drops solidify. These are separated off and introduced to a precipitating medium. Drying then takes place and/or a thermal treatment.
WO 02/57319 describes the production of cellulose pearls using the NMMO process whereby different additives in large quantities are added to the cellulose solution prior to forming, for example titanium oxide or barium sulphate and materials acting as ion exchangers. The products obtained can be used as ion exchangers or catalysts.
The production of a titanium oxide suitable as an ion exchanger for example for waste water purification is described in U.S. Pat. No. 6,919,029. Particularly high absorption capacities and speeds are achieved with this material since the titanium oxide material is activated via a special treatment on the surface. This titanium oxide material can be described as a "substoichiometric titanium oxide". This means that the ratio of the oxygen atoms to the titanium atoms in the material is smaller than 2. Reference is made to the description in U.S. Pat. No. 6,919,029 for a more detailed description of this surface activation.
Other possibilities to produce titanium oxides which are particularly well suited to waste water treatment, are in the so-called "doping" of titanium oxide with iron and sulphur atoms. These substances have a photocatalytic activity.
All of these processes have the disadvantage that an orientation of the cellulose molecules develops in the resulting particles when exposing the cellulose solution to only very slight shear forces which, following complete coagulation or regeneration, leads to a fibrillar, i.e., fibrous particle structure. The demand for spherical instead of fibrillar powders is, however, constantly on the increase since fibrillar powders reveal various disadvantages. Thus fibrillar powders are not suitable for some applications (e.g., viscosity modifiers) because they change the flow behavior of the liquid, to which they are added, so that it is dependent on the shear strain, i.e. in the direction of non-Newtonian behavior. This is not desirable with printing inks, for example. Moreover, spherical cellulose powders flow more readily and can be more easily conveyed, dosed and dispersed. This plays an important role particularly with applications in the pharmaceutical, cosmetics and foodstuff industry and when replacing silica gel and other inorganic substances. However, these particles must have a sufficient absorption capacity for the different substances despite the non-fibrillar structure e.g., pharmaceutical active agents, aromas, oily and fatty substances.

Cellulose powder and processes for its production