A test signal supplying device includes a first external terminal, a second external terminal being applied with a predetermined electric potential, an internal load, a first terminal that is connected to the first external terminal through the internal load, a second terminal that is connected to the first external terminal without passing through the internal load, a test signal generating section that generates a test signal and supplies the test signal to the second terminal, a detecting section that detects an amplitude of the test signal, and a controlling section that measures an impedance of an external load connected to the first and second external terminals based on the detected amplitude of the test signal.

1. Technical Field
The present invention relates to a technique for measuring an impedance by supplying a test signal to an external load. Also, the present invention relates to a technique for adjusting an amplitude of an output signal in accordance with the external load.
2. Background Art
In a sound output circuit that amplifies a sound signal and outputs the amplified signal to an external load, one which measures an impedance of the external load and switches between sound signals in accordance with a measured value of the external load, is known (JP-A-2003-179441). A speaker or a headphone to be connected as the external load, can have an impedance of 4, 8, 16 or 32Ω. In a conventional technique, since a sound signal is switched in accordance with the external load connected to the sound output circuit, the technique has an advantage that it is possible to prevent a device connected to the sound output circuit as the external load from being damaged by an excessive input, in advance.
Meanwhile, it is thought that a test signal is supplied to an external load in order to measure an impedance of the external load. In this case, an output signal and the test signal are switched to be supplied to the external load.
However, from a view point of protection of the external load, it is general that the output signal is supplied to the external load through an internal load such as a protection resistor or the like in a signal amplifying device. In this case, when the test signal is supplied to the external load through the internal load, a problem arises that a total impedance of the internal load and the external load is to be measured so that the impedance of the external load is not accurately measured.
Also, in a signal amplifying circuit that amplifies an input signal and outputs the amplified signal to an external load, a technique is known in which a test signal is supplied to an external load and determination is made as to whether the external load is a stereo plug or a monaural plug (JP-B-4182802). In the technique, a frequency of the test signal is set to a high frequency out of an audible band so that a user does not hear a sound of the test signal.
A speaker or a headphone to be connected as an external load has a reactance component so that an impedance thereof varies due to a change in a frequency. Therefore, when a test signal is set to a high frequency out of an audible band, the impedance in the high frequency may be possibly deviated from an impedance in the audible band. Consequently, the impedance in a required audible band is not able to be accurately obtained. In addition, the test signal may be attenuated in the external load so that it may become difficult to measure the impedance at a high SN ratio. Moreover, it is necessary to expand a frequency characteristic of a circuit for generating the test signal up to a high frequency out of an audible band so that it is necessary to cause components constituting a signal amplifying circuit such as transistors to correspond to the high frequency.

Test signal supplying device and semiconductor integrated circuit


A method, apparatus, and system are disclosed for incrementally derating a torque applied by a drivetrain in response a number of traction control events detected by a traction control system over a predetermined time period.

Environmental concerns and limited natural resources are highlighting the desire for reduced fuel consumption. One promising avenue toward the reduction of fuel consumption is the use of hybrid and electric powertrains. Such powertrains utilize regenerative braking to increase the overall efficiency of the system. Regenerative braking provides negative torque to the driveline and recovers kinetic energy from a moving vehicle and utilizes the recovered energy to store electrical potential energy. Vehicles may also include other types of braking systems that create negative torque, such as compression release braking and exhaust braking, and of course accelerator pedals to create positive torque.
Most vehicles today are provided with a traction control system, such as an anti-lock brake system (ABS). The traction control system detects loss of traction between the wheels and the road surface such as may occur during a torque change. The traction control system intervenes in response to a traction control event during a torque change by sending a command to the engine/motor controller or retarder controller to derate traction and/or retard torque on the driveline during the traction control event. When the traction control event is over, the derate is removed at a controlled rate to avoid problems with a sudden reapplication of torque.
In presently available hybrid and electric powertrain systems, regenerative and other braking is typically triggered by means other than actuation of the brake pedal, such as at the low end of the accelerator pedal when it is lifted or released. As a result, by lifting of the accelerator pedal a significant amount of braking is automatically applied, which may create a traction control event in slick conditions. Since the amount of negative torque that is applied is predetermined and typically based on dry road conditions and other factors, poor traction road conditions are likely to produce multiple traction control events because the same amount of negative torque is re-applied to the powertrain each time the braking event occurs, regardless of any history of traction loss. Therefore, further technological developments are desirable in this area.

Torque deration in response traction control events


A bulk material transport vehicle access structure includes an elongated service platform for workers which is pivotally supported at its opposite ends to cantilever arms on parallel horizontal axes to avoid binding between the roller carriages of the cantilever arms and a pair of support pillars. The floor of the platform includes a walkway and a doorway covered by a plurality of side by side doors which may be selectively opened. Electric controls are provided to automatically stop operation of the power means used to control the elevation of the cantilever arms should the service platform become tilted a predetermined extent. Electric controls are also provided to stop lowering of the service platform when it reaches the top of a bulk material transport vehicle.

An access structure is needed to enable workmen to have access to the top of bulk material transport vehicles such as bulk material tank trucks used to transport fluid material. In one form of such an access structure, a pair of cantilever arms supporting a service platform are mounted on a pair of upright supports or pillars and are reciprocated up and down by a pair of linear acting fluid actuators. Although fluid may be supplied to the actuators by way of a flow divider, it is possible for the flow to the actuators to be slightly unequal. Thus over time one cantilever arm may be somewhat elevated relative to the other, thereby creating an unsafe, non level service platform and binding in the carriage roller connection between the cantilever arms and the upright supports. It is desired to provide structures which keep a safe inclination and avoid binding in the roller carriage connection. Prior bulk material access platforms have an elongated tank access opening extending along their entire length and a narrow walkway along one side of the elongated opening. Thus platform support for workers was provided only on one side of the opening. It has been found desirable to provide platform support for workers positioned on more than one side of the tank area being serviced.

Bulk material transport vehicle access structure


An apparatus for treating a surface bounding a space within which a bulk supply of flowable material can be contained. The apparatus has an elongate support with a proximal region and a distal region. At least one flexible tube is provided at the distal region of the elongate support through which a fluid from a pressurized supply can be directed. The at least one flexible tube is movable continuously in a whipping action to thereby cause a force to be applied to a surface at or adjacent to which the flexible tube is located to thereby at least one of: a) apply a fluid; and b) separate matter adhered, to a surface at or adjacent to which the flexible tube is located. The apparatus further has a moving assembly for the elongate support. The moving assembly is operable to controllably reposition and/or reconfigure the elongate support, thereby to controllably place the at least one flexible tube at different selected locations with respect to a surface to be treated by the apparatus.

1. Field of the Invention
This invention relates to environments wherein there are exposed surfaces bounding a space within which a bulk supply of flowable material can be contained and, more particularly, to an apparatus for at least one of: a) applying a fluid; and b) separating matter adhered, to the surface.
2. Background Art
Cargo ships, especially dry-bulk cargo and liquid-bulk cargo ships, are used to transport a wide range of products and materials on waterways worldwide. In one known dry-bulk cargo ship construction, multiple cargo holds are formed in the ship's hull to accept bulk quantities of particulate material. Each cargo hold is bounded by a metallic wall structure and has an overhead access for loading and unloading of the materials. A typical cargo hold may have length and width dimensions on the order of 100 feet, a height on the order of 60 feet, and in excess of 220,000 square feet of exposed, interior, surface area.
A description of the transportation of powdered cement in a dry bulk cargo ship will be provided hereinbelow to demonstrate some of the problems that have plagued this industry. In a typical operation, a cargo hold will be filled with the cement at a load port. At the destination port, the cement is discharged. Loading and discharge of the cement is carried out using any of a number of different, well-known techniques and equipment. These techniques are designed to remove the majority, but not all, of the bulk cargo. The balance of the residual cargo, as well as residues of previous cargo, other debris, loose rust, scale, loose paint and other potential contaminants such as stains, must also be removed prior to loading another cargo at the same or a different load port.
In the event that the hold is refilled with cement, the preparation of the hold for reloading may be minimal. However, if the next cargo is different, all interior surfaces of the hold, including the walls of the hold, may have to be thoroughly cleaned so as to not contaminate the new product with the cement residue that adheres to the walls, overhead and other structures, fittings within the hold, and hatch covers.
The shipping industry is highly competitive. Consequently, efficiency becomes a primary focus of those in this industry. A ship in port is doing nothing more for its owner/operator/charterer than generating expenses. Any crew that is not participating in the cleaning process is being paid for down time. Docking, fuel, and other fees accrue on a daily basis. Charter times are usually calculated in six minute intervals. Thus, it is clearly in the interest of the owner/operator to quickly, safely and efficiently clean the cargo holds and refill the same to allow transportation of materials and generation of income after the ship is certified clean and placed "on hire". Unfortunately, an emphasis on efficiency may cause a compromise in safety in the cleaning operations. Even on an expedited schedule, however, the preparation of five to nine separate cargo holds may take as long as 3-5 days, or longer.
Many of the above problems are inherent to cargo ship holds by reason of their significant expanse. However, other exposed surfaces in those environments in which discrete, flowable/pourable matter is stored and/or conveyed present a particular problem to those that are required to treat them, either by reason of separating matter therefrom or applying a surface preparation product thereto.
There are a number of exposed surfaces, both flat and contoured, that exist in cargo holds, on hatch covers, and in other environments, that require special measures to separate adhered matter. The matter may be foreign matter that becomes adhered to a surface by reason of contact with that surface, such as in the event of a separately stored material that contacts the surface. Alternatively, the matter may have been generated from the surface itself, be it by rust, corrosion, loose paint, interaction with a component, or infliction of some damage to the surface. Regardless of the origin of the matter, it is often present in such a manner that it is either a) adhered with a significant tenacity to the surface or b) located at a contour, scar, indentation, or obstruction such that is not readily accessible to be directly contacted and dislodged, as by a brush or scraper, or impacted by a pressurized supply of gas, liquid, or solid.
These conditions may be present in ship cargo holds and other environments, such as silos, storage tanks, barns, bulk rail hopper cars, storage and transfer hoppers, etc. The surfaces thereof may be made from any of a number of different materials, such as metal, concrete, plastic, wood, etc. Further, these conditions are not peculiar to environments in which materials are stored. As one example, material conveyors have surfaces, which support and transport matter and otherwise come into contact with the matter, that must be cleaned during use. For purposes of explanation herein, the number of field conditions which the present invention is adapted to address will be described with respect to the shipping industry, with it being understood that the application is not so limited and may be used in any environment wherein materials are in contact with surfaces in both static and dynamic states.
In a ship's cargo hold, a number of surface configurations are routinely encountered. In addition, each cargo hold may have its own unique configuration which impairs access and complicates the process of separating matter from exposed surfaces thereon.
Typical to ship holds are corners at which side walls, floors, and ceiling surfaces meet. Ladders and stairs for ingress and egress are also common to this environment. A crew cleaning a ship's cargo hold can also anticipate encountering ledges, hatches with various recessed contours, etc. It is also common in the shipping industry to bound cargo holds with corrugated panels and steel beams.
Heretofore, those cleaning ship cargo holds have had essentially two options. The first option is to use currently available equipment to access these hard-to-reach areas directly by the worker on a lift or ladder. This typically involves using lifts for higher surfaces to situate the worker in close proximity to the particular condition. While some such surfaces may be reasonably accessible, most surfaces are not, due in part to their height. At some locations, the matter to be separated, by reason of inaccessibility due to either height or some obstruction, may be accessed as by a blast of pressurized air, potentially at medium or high pressure, which causes light particles to become entrained in the surrounding area. This may create a health risk to the workers and also potentially obstructs vision.
It is also known to impact liquid against such surfaces either alone or in combination with gas augmentation. One such method utilizes a water cannon delivered by a hose. Another method utilizes a water cannon with pressure assist through medium pressure air. Alternatively, the liquid, which may be water, is impacted at high pressures.
It is further known to use shotguns to blast regions with pellets to break loose matter that is difficult to remove either by reason of the height at which it is located, or the tenacity with which it is adhered.
These latter processes are limited in the sense that they generally require an unobstructed path between the unit propelling the gas or liquid and the area to be impacted and thereby treated. Most shipping environments include contours, obstructions, indentations, etc., that preclude direct linear access.
Some structures also create other unique conditions that must be contended with by those cleaning surfaces in these environments. For example, at upwardly facing ledges and other transition areas, a significant accumulation of matter may occur. Breaking up a large accumulation of such matter typically is accomplished by directly accessing the accumulations, potentially at dangerously high locations. Alternatively, blasting such accumulations may aggravate the aforementioned problem of entraining the lighter particles, which creates health risks and obscures workers' vision within the hold.
Accordingly, a second option in the industry to avoid these time consuming efforts is to focus the cleaning operation on bulk recovery, without spending the time required to separate matter by accessing these surfaces. This practice may contribute to the deterioration of surfaces over time. The residue may also contaminate subsequently loaded materials. This latter option is almost inevitable in certain environments in which surface intricacies are such that it would be impractical for workers to directly access and/or break loose the matter at a number of different locations.
The cleaning process is not limited to separately adhered matter, but may also involve removing stain and rust and scale that is adhered with a tenacity sufficient that it is not easily broken loose, as by a brush passing thereagainst. Consequently, there is a need to take other measures to remove this type of potential contaminant. In a large volume space, in which there may be over 220,000 square feet of surface to treat, such a cleaning operation may represent an enormous amount of down time as crews maneuver and use equipment that requires that the ship be at rest in port.
Heretofore, individual workers have generally employed tools in the form of small brushes and scrapers. These tools may require a significant force application, depending upon surface conditions, and make surface contact over only a small area as they are used. Thus, treatment of the full expanse of a surface within a ship's hold is labor intensive and fatiguing when carried out with this conventional equipment. If the size of the tools is increased to increase surface contact area, the manipulation of the tools, either directly or through elongate poles, becomes more onerous and fatiguing. Even with smaller tools, worker fatigue is a significant problem, potentially in a relatively short time frame. To minimize down time, it becomes necessary to use large crews that require relief after fatigue sets in. It may not be practical, or even possible, to keep available the number of persons necessary to meet reasonable cleaning deadlines imposed by those with a financial stake in the shipping operations.
Another operation that is commonly undertaken is the application of a component preparatory to storage of a particular type of material. Ideally, an additive would be applied to each surface which the material contacts. This may be a labor intensive process, particularly in large spaces wherein workers have been required to be placed in close proximity to the surfaces to which the additive is applied. Conventional application techniques may be inadequate to apply the additive to surfaces that are intricate, in tight spaces, or not readily accessible.
The shipping industry has for the most part contended with the above problems, most notable which are significant down time, expensive cleaning processes, and potentially ineffective cleaning of ship cargo holds. The industry continues to be in need of improved methods and apparatus for cleaning foreign matter from, and treating, such surface areas.

Apparatus for treating a surface bounding a space within which a bulk supply of flowable material can be contained


There is provided an adjustable harmonic distortion detector that includes a clock signal source, means for the detection of a first period of evaluation, and means for the detection of a second period of evaluation. The detector has the characteristic that a first block memorizes a number equal to the clock pulses present in the first period of evaluation, a multiplier block performs a multiplication between the number stored in the first block and a multiplicative factor during the second period of evaluation, and a second block memorizes the outcome. The second block is adapted to generate an output signal when the outcome in the second block is equal to zero.

1. Field of the Invention
The present invention relates to an adjustable harmonic distortion detector and method for using the same, particularly for linear (AB class) and switching (D class) amplifiers.
2. Description of Related Art
The term distortion designates any undesired deformation in the time trend of a signal and we distinguish two types of distortion: a) linear; and b) non linear.
The linear distortion happens when an input sinusoidal signal having a given amplitude and a given phase causes a still sinusoidal output signal having a different amplitude and/or phase.
The non linear distortion happens when an input sinusoidal signal causes an output signal which is no longer as such.
Particularly, in this last case, the distortion is measured in function of the deformation that the sinusoidal signal suffers, being founded on the possibility of dividing the deformed signal, into a sinusoidal oscillation having the same frequency (called fundamental oscillation) and into a number "n", with "n" rising to infinity, of oscillations having multiple frequencies of the fundamental (called harmonic oscillations).
We assume as convention, as a measure of the total harmonic distortion T.H.D., the ratio, usually expressed percent, between the total efficacious value of the harmonics and the efficacious value of the fundamental.
The distortion entity has a particular importance in the acoustic frequency amplifiers, that is for audio amplifiers, because it can modify the signal intelligibility.
An usual function in the audio amplifiers is the so called distortion detector function, called "clipping function", that has the role to detect when an amplifier has reached the peak power.
Using this information we can limit the distortions that a signal outgoing from the amplifier suffers, distortions due to the reached threshold of saturation of the same amplifier.
In this way by means of opportune circuits we can define "a priori" a fixed level of acceptable distortion, that is we can define at which distortion level the clipping function can interfere so as to reduce the amplifier gain, limiting, therefore, the distortion inside desiderated ranges.
The circuits now used are essentially of three categories: a) by a sensor of the saturation of the output power transistor of the audio amplifier, able to detect a distortion at a prefixed threshold value, as shown in FIG. 1 wherein we note an ideal output signal 1, a distorted signal 2 and a prefixed intervention threshold 3; b) by a comparison between the peak voltage of the input signal and the peak voltage of the same signal at the output of the audio amplifier when this last output signal is distorted, as shown in FIG. 2; c) by a measurement of the unbalance of the input pins of the audio amplifier (in fact during the normal working the input pins are at the same voltage, while when the amplifier saturates the pins assume a voltage difference that depends on the input signal amplitude).
The circuits heretofore described work correctly only in the case of AB class amplifiers, give troubles if the amplifier is D class and mostly if the amplifier is implemented in an integrated circuit wherein the output signal is not available inside the same integrated circuit.

Adjustable harmonic distortion detector and method for using the same


A semiconductor wafer having a plurality of chip die areas arranged on a wafer in an array, each chip die area including a seal ring area with one or more first sets of polygonal structures. The wafer further comprises scribe line areas between the chip die areas, the scribe line areas including one or more second sets of polygonal structures. The presence of proximate polygonal structures between the scribe line and seal ring areas balance stresses between the chip die areas during wafer dicing operation.

A semiconductor chip or die (e.g., an image sensor chip) is typically fabricated on a single semiconductor wafer along with hundreds, and in some cases thousands, of copies of the same die. Cutting is needed to separate individual dies from a semiconductor wafer. Such cutting is known as dicing or wafer dicing and is typically performed using a die saw. A common die saw used for dicing is a diamond saw. Conventionally, cuts are made along non-functional areas of semiconductor material, known as scribe lines, which separate the dies on the wafer from each other. Using a diamond saw introduces mechanical stress to the semiconductor wafer and can result in cracking at the die edges thereby compromising the integrity and reliability of integrated circuit (IC) devices present on the die. One alternative to using a diamond saw is laser scribing. Laser scribing involves scanning a laser beam over the scribe lines of a semiconductor wafer; however, laser scribing typically provides a low throughput and is expensive.
Typically, scribing or cutting is carried out on the active side of the semiconductor wafers where the IC devices are formed and the scribe lines are defined. Conventional scribe line areas do not have circuit elements of the die areas, and because each die is an independent device, metal features for interconnect wiring conductors are also confined to the die areas and do not extend into or across the scribe lines where the die saw will cut through the wiring layers. Some wafer-level reliability and functionality test pads, however, can be located in the scribe line areas to facilitate wafer-level testing. In such wafers, the scribing or cutting across the test pads generally results in severe dielectric peeling and cracking. These de-laminations become sources of defects that detrimentally affect the integrity and reliability of the diced chips.
Further, an increasing demand for image sensors having faster processing speeds and better image quality has led to smaller pixel cells sizes and smaller photosensitive regions or photodiodes. Advances in semiconductor technology including the use of low-k or extremely low-k (ELK) dielectric materials to reduce cross coupling and parasitic capacitance between metal layers are employed to match the pace of decreasing image sensor chip size. Such low-k and ELK dielectrics, however, are brittle due to their porous nature subsequently making image sensors with such materials prone to peeling and cracking when diamond saws are used to separate dies on a semiconductor wafer.
Another conventional method of increasing the size of a photodiode in a pixel cell is to use a backside illuminated ("BSI") image sensor. BSI image sensors typically include a pixel array fabricated on the frontside of the semiconductor wafer, but receive light through a back surface of the image sensor. During fabrication of a BSI image sensor, the image sensor chip or device is first fabricated on a semiconductor wafer, and when the necessary elements have been formed in or on the wafer, the device wafer is bonded to a carrier wafer for further processing. Due to the tradeoff of parameters such as bonding strength and wafer distortion, bonding strength can be maximized, but this can cause weakness at the bonding interface. This combination of low-k or ELK dielectrics in the device wafer and weak bonding interface can increase the occurrence of peeling and cracking when a diamond saw is used to dice BSI dies from the combined wafer. Thus, there is a need for improved scribe line structures in the semiconductor industry.

System and method for die to die stress improvement

Taiwan Semiconductor Manufacturing Co., Ltd.


A magnetic storage device includes a magnetoresistive element. A pair of side faces of the magnetoresistive element are at least partially opposed to end faces of a pair of open ends of a magnetic yoke. Moreover, the pair of side faces of the magnetoresistive element and the end faces of the pair of open ends of the magnetic yoke have predetermined angles, respectively. Thus, the magnetic storage device can reduce writing current while the magnetic storage device has a small and simple structure.

1. Field of the Invention
The present invention relates to a magnetic storage device that can store information therein by using a magnetoresistive effect.
2. Description of the Related Art
Conventionally, a magnetic storage device called as a magnetic random access memory (MRAM) that can store information therein by using a magnetoresistive effect is widely known as a nonvolatile memory device that can operate at high speeds.
The magnetic storage device is required to efficiently perform writing to a magnetoresistive element in order to achieve improvement of an operation speed, reduction of writing current, and the like. For example, a magnetic storage device is proposed that includes an approximately annular magnetic yoke for concentrating a magnetic flux generated around a wiring on a magnetoresistive element (see Japanese Patent Laid-Open Publications Nos. 2000-90658 and 2004-128430, for example).
However, it is necessary to increase the magnetic flux concentrated on the magnetoresistive element by making the magnetic yoke larger in order to further reduce the writing current in the conventional magnetic storage device. Thus, the reduction of the writing current in the magnetic storage device that has to be made compact has a limitation.


In the present resistive memory array, included are a substrate, a plurality of source regions in the substrate, and a conductor connecting the plurality of source regions, the conductor being positioned adjacent to the substrate to form, with the plurality of source regions, a common source. In one embodiment, the conductor is an elongated metal body of T-shaped cross-section. In another embodiment, the conductor is a plate-like metal body.

1. Technical Field
This invention relates generally to memory devices, and more particularly, to a memory array which includes a plurality of resistive memory devices.
2. Background Art
FIG. 1 is a schematic representation of a portion of a DRAM memory array 100 proposed for 1-mega-bit class density. The array 100 includes a plurality of word lines (two shown at WL0, WL1), and a plurality of bit lines (one shown at BL0). The array includes a large number of similar memory cells (two memory cells MC0, MC1 shown in FIG. 1). The memory cell MC0 includes a capacitor C0 having one plate C0P1 connected to bit line BL0 and the other plate C0P2 connected to the drain D0 of an MOS transistor T0. The word line WL0 is connected to the gate G0 of the transistor T0. Likewise, the memory cell MC1 includes a capacitor C1 having one plate C1P1 connected to bit line BL0 and the other plate C1P2 connected to the drain D1 of an MOS transistor T1. The sources S0, S1 of these transistors T0, T1 are connected together, resulting in what is called a common-source (CS) memory array 100. It will be understood that the two cells MC0, MC1 shown and described are part of a large number of such memory cells in the array 100.
The data storing mechanism of each memory cell is based upon the presence or absence of electric charge accumulated in the capacitor. The presence or absence of the electric charge in the capacitor can be sensed by means of sense amplifier SA (connected to a bit line BL0), sensing current in the bit line BL0.
FIG. 2 is a cross-sectional view of an implementation of the structure of FIG. 1. As shown, the structure of FIG. 2 includes a p type silicon semiconductor substrate SS having spaced n+ diffused regions n+1, n+1, n+3 therein. The region n+1 and the region n+2 make up the drain and source of transistor T0 which includes gate oxide and gate WL0 (G0), while the region n+3 and the region n+2 make up the drain and source of transistor T1 which includes gate oxide and gate WL1 (G1). Polycrystalline silicon layers C0P2, C1P2 are provided in contact with the respective drain regions n+1, n+3 of the transistors T0, T1, and a dielectric film I is provided as shown, separating the layers C0P2, C1P2 from the gates WL0, WL1 of the transistors T0, T1. A layer of metal BL0 is formed over the dielectric film I. The metal layer BL0 is separated from the polycrystalline silicon layers C0P2, C1P2 by the dielectric film I, so that metal layer BL0 and layer C0P2 form capacitor G0, while metal layer BL0 and layer C1P2 form capacitor C1. The central n+ region n+2, commonly used by the transistors T0, T1, acts as the common source of the transistors T0, T1.
FIG. 3 is a graph illustrating typical drain-to-source (IDS) current flow through a transistor of the array as described above, for increasing drain-to-source voltage (VDS), based on increasing steps in the gate-to-source voltage (VGS) of the transistor. If VDS and VGS are kept relatively low (for example with VGS limited to 2 V, and VDS limited to 3 V, current through the transistor is limited to 30 ua).
FIG. 4 illustrates a two-terminal metal-insulator-metal (MIM) resistive memory device 130. The memory device 130 includes a metal, for example copper electrode 132, an active layer 134 of for example copper oxide on and in contact with the electrode 132, and a metal, for example copper electrode 136 on and in contact with the active layer 134. With reference to FIG. 5, initially, assuming that the memory device 130 is unprogrammed, in order to program the memory device 130, ground is applied to the electrode 132, while a positive voltage is applied to electrode 136, so that an electrical potential Vpg (the "programming" electrical potential) is applied across the memory device 130 from a higher to a lower electrical potential in the direction from electrode 136 to electrode 132. Upon removal of such potential the memory device 130 remains in a conductive or low-resistance state having an on-state resistance.
In the read step of the memory device 130 in its programmed (conductive) state, an electrical potential Vr (the "read" electrical potential) is applied across the memory device 130 from a higher to a lower electrical potential in the direction from electrode 136 to electrode 132. This electrical potential is less than the electrical potential Vpg applied across the memory device 130 for programming (see above). In this situation, the memory device 130 will readily conduct current, which indicates that the memory device 130 is in its programmed state.
In order to erase the memory device 130, a positive voltage is applied to the electrode 132, while the electrode 136 is held at ground, so that an electrical potential Ver (the "erase" electrical potential) is applied across the memory device 130 from a higher to a lower electrical potential in the direction of from electrode 132 to electrode 136.
In the read step of the memory device 130 in its erased (substantially non-conductive) state, the electrical potential Vr is again applied across the memory device 130 from a higher to a lower electrical potential in the direction from electrode 136 to electrode 132 as described above. With the active layer 134 (and memory device 130) in a high-resistance or substantially non-conductive state, the memory device 130 will not conduct significant current, which indicates that the memory device 130 is in its erased state.
FIG. 6 is a schematic representation of a portion of a typical resistive memory device array 200. The array 200 includes a plurality of word lines (two shown at WL0, WL1), and a plurality of bit lines (one shown at BL0). The array 200 includes a large number of similar memory cells (two memory cells M0, M1 shown in FIG. 6). The memory cell M0 includes a resistive memory device RM0 as described above and as illustrated in FIG. 4, having one electrode RM0E1 connected to bit line BL0 and the other electrode RM0E2 connected to the drain D0 of an MOS transistor T0. The word line WL0 is connected to the gate G0 of the transistor T0. Likewise, the memory cell M1 includes a resistive memory device RM1 having one electrode RM1E1 connected to bit line BL0 and the other electrode RM1E2 connected to the drain D1 of an MOS transistor T1. The sources S0, S1 of these transistors T0, T1 are connected together, resulting in a common-source (CS) memory array. It will be understood that the two cells M1, M2 shown and described are part of a large number of such memory cells in the array 200. A sense amplifier SA is connected to bit line.
It will be seen that the structure of FIG. 6 is similar to that of FIG. 1, but with the capacitors replaced by resistive memory devices.
FIG. 7 illustrates a larger portion of the array 200 of FIG. 6, with the common source CS connected to ground. Typically, the programming and erasing of a resistive memory device of the array 200 requires a substantially larger current therethrough than the current described above for a DRAM cell. In addition, and with reference to FIG. 7, with a large number of bit lines connected to each word line (for example bit lines BL0-BL7 connected to a word line WL0, or in actual implementation more than 256 bit lines connected to the same section driving line to minimize array area), it will be seen that upon selection of a word line, for example word line WL0, all current in the bit lines BL0-BL7 will flow through the common source CS to ground. These conditions result in the common source CS carrying high levels of current. In such situation, it is highly desirable to provide a low common source resistance, to reduce voltage drop therein, so as to keep the operating speed at an appropriate level, and to also provide high transistor drivability attributable to the grounded source bias condition to insure high performance of the array.
Therefore, what is needed is a resistive memory device array which includes a low-resistance common source and high drivability characteristics.

Memory cell array with low resistance common source and high current drivability


A metallic nickel powder exhibits superior oxidation behavior and sintering behavior in a process for production of a multilayer ceramic capacitor, and as a result, can prevent delamination, a process for production of the metallic powder is provided. The metallic nickel powder is treated with a carbonic acid water solution. The metallic nickel powder has an average particle diameter of not more than 1.0 μm, oxygen content in a range of from 0.3 to 2.0 wt %, and oxide layer having a thickness in a range of from 2 to 10 nm over the entire surface. In the process for production of the metallic nickel powder, the powder is treated with a carbonic acid water solution and is heated in an oxidizing atmosphere.

Conventionally, noble metallic powders such as those of silver, palladium, platinum, and gold or base metallic powders such as those of nickel, cobalt, iron, molybdenum, and tungsten are used in conductive pastes as electrical materials, and in particular, in internal electrodes of multilayered ceramic capacitors. Generally, a multilayer ceramic capacitor is made by alternately laminating ceramic dielectric layers and metallic layers which are used as internal electrodes, and by forming external electrodes which are connected to the metallic layer of internal electrodes on two outside faces of the ceramic dielectric layers. Materials which contains a high dielectric constant material as a main component such as barium titanate, strontium titanate, and yttrium oxide are used in the dielectric substances. On the other hand, the noble metallic powders or the base metallic powders mentioned above may be used to form the internal electrodes. However, since more inexpensive electrical materials are required recently, multilayer ceramic capacitors in which the latter base metallic powders are used have been greatly developed. In particular, nickel powder has been mainly developed.
A multilayer ceramic capacitor may be made by the following method. First, a dielectric powder such as one of barium titanate is mixed with an organic binder so as to be suspended. Next, the suspension is formed into a sheet by a doctor blade method to form a dielectric green sheet. On the other hand, metallic powder for an internal electrode is mixed with organic compounds such as organic solvent, plasticizer, or organic binder to form a metallic powder paste, and this paste is coated on the green sheet mentioned above by screen printing. After they are dried, laminated, and pressed, the organic component is removed by heat treatment. Furthermore, they are burned at 1000 to 1300° C. or at more than 1300° C., and outer electrodes are baked on both sides of the dielectric ceramic layer to obtain a multilayer ceramic capacitor.
In the process for production of the multilayer ceramic capacitor described above, the heating treatment in which organic components are vaporized and removed after the laminating process and the pressing process is ordinary performed at 250 to 400° C. in air. In this way, since the heating treatment is performed under an oxidizing atmosphere, metallic nickel powder is oxidized, and therefore, volume expansion occurs. At the same time, the metallic nickel powder begins to be sintered, and volume shrinkage occurs.
Due to this, in the process for production of the multilayer ceramic capacitor, volume change occurs due to expansion or shrinkage of the metallic powder by oxidizing, reducing, and sintering reaction beginning at a low temperature of about 300° C. In this case, if the oxidation behavior or sintering behavior of the metallic nickel powder at low temperature is unstable, deformation may easily occur between the dielectric layer and the electrode layer. As a result, breaking of the layer structure, which is called delamination, such as cracking or exfoliation, may occur.
Many techniques have been suggested to overcome the delamination problem. For example, Japanese Unexamined Patent Application Publication No. Hei 08-246001 discloses metallic nickel power having a tap density of more than a certain limit value versus a certain particle diameter. In this publication, by producing a capacitor in which such a metallic nickel powder and a dielectric is contained in a paste thereof, delamination is unlikely to occur.
The above-mentioned conventional technique is efficient for improving sintering behavior to some extent; however, it is not sufficient to prevent delamination, and further improvement is required.

Metallic nickel powder and process for production thereof


The present invention has an object to provide a method for producing particulate barium carbonate having desired properties such as high purity, fineness, and has a spherical shape. The present invention relates to a method of producing substantially spherical barium carbonate, including (A) mixing, in an aqueous medium, a barium compound with at least one first ingredient selected from the group consisting of gluconic acid or salts thereof, gluconolactone, glucoheptonic acid or salts thereof, and glucoheptonolactone, to prepare a mixture; and (B) reacting the barium compound with carbon dioxide or a water-soluble carbonate in the mixture, to produce substantially spherical barium carbonate.

Barium carbonate is one of main raw materials of barium titanate, which is used for electronic materials. Recent development for downsizing and upgrade of electronic devices requires improvement of the capacity and performance of monolithic ceramic chip capacitors. For such improvement, barium titanate, which is a raw material of monolithic ceramic chip capacitors, has been required to have higher purity and finer size.
Barium titanate is generally produced by mixing barium carbonate and titanium dioxide in a wet form, and drying, followed by calcination. To produce high quality barium titanate, it is desired to perform uniform wet mixing and uniform calcination. A titanium dioxide particle has a relatively low aspect ratio (namely, more spherical). Thus, it is also desired to use barium carbonate with a low aspect ratio for uniform calcination.
Generally, barium carbonate, which can be used for electronic materials, is produced by first eliminating impurities from barium salts (such as barium hydroxide, barium chloride, barium nitrate) through, for example, recrystallization or filtration, then preparing an aqueous solution of purified barium salts, and blowing gaseous CO2 to the aqueous solution, or mixing a solution of a water-soluble carbonate (ammonium carbonate, sodium carbonate, potassium carbonate, etc.) with the aqueous solution.
However, when barium carbonate fine particles are dispersed in water, particles tend to aggregate to decrease the surface energy of particles. Generally, the finer particles are, the higher aggregation force between particles is. Thus, finer particles tend to aggregate more firmly. Additionally, barium carbonate produced through a reaction of barium salts with gaseous CO2 or a water-soluble carbonate generally has a spicular shape.
To produce uniform titanium dioxide from such spicular barium carbonate, methods which include fine grinding of spicular barium carbonate during mixing with titanium dioxide are conventionally employed. One of examples of such methods include the step of finely grinding spicular barium carbonate with a bead mill (in which zirconia beads, etc. are enclosed) in a wet state to finely grind particles to be almost spherical shape. However, sufficient strength of grinding is required and it takes long time to produce fine particles with a low aspect ratio. Thus, a special apparatus is generally required for such fine grinding.
Some trials to omit such a complicated and costly step of grinding have been made on processes of forming fine and spherical particles from raw material barium carbonate. Examples of chemical approaches in such trials include methods, which includes adding a carboxylic acid such as citric acid or tartaric acid, or pyrophosphoric acid during the reaction, as described in the Patent Document 1 or Patent Document 2.
As physical approaches, Patent Documents 3 and 4 suggest some methods for producing barium carbonate with a low aspect ratio by grinding synthesized spicular barium carbonate with a grinder which utilizes grinding by ceramic beads.

Generally spherical barium carbonate particles, and method for producing generally spherical barium carbonate particles


An optical system for an optical disc drive includes a light source, an objective lens and a collimator lens. The light source emits first and second light beams. The first light beam is for reproducing data from a digital versatile disc while the second light beam is for a compact disc. The objective lens is provided with a diffraction structure which is designed to focus the first light beam on a recording layer of the digital versatile disc and the second light beam on a recording layer of the compact disc. The collimator lens is disposed between the light source and the objective lens. The collimator lens adjusts the diverging/converging angle of the first and second light beams entering the objective lens. The change in spherical aberration of the first light beam caused by wavelength deviation from a design wavelength due to individual specificity of the light source is corrected by adjusting the diverging/converging angle of the first light beam emerging from the collimator lens.

The present invention relates to an optical system for an optical disc drive handling different types of optical discs having protective layers of different thickness.
There are several types of optical discs such as a digital versatile disc and a compact disc. The thickness of the protective layers, i.e., the transparent substrate covering a recording layer of the optical disc, depends on the type of the optical disc. For example, the protective layer of the compact disc (CD) is 1.20 mm thick while that of the digital versatile disc (DVD) is 0.60 mm thick. The protective layers having different thickness cause spherical aberrations of different amount. Therefore, an optical system for an optical disc drive that handles different types of optical discs should be designed by taking into account the difference of the spherical aberrations between each type of optical disc.
Since the recording density of the digital versatile disc is much higher than that of the compact disc, size of the beam spot to be formed on the digital versatile disc is required to be much smaller than that for the compact disc. The difference between the beam spot sizes requires the optical disc drive to utilize shorter wavelength laser beam for the digital versatile disc, i.e., 635-665 nm, than for the compact disc, i.e., 780-830 nm, since the beam spot size can be made smaller as the wavelength decreases.
Recently, it is proposed to employ an objective lens provided with a diffraction structure for the optical system of the optical drive handling different types of optical disc. The diffraction structure is a large number of concentric ring-shaped steps and converges each of the laser beams of different wavelengths onto the recording layer of the corresponding optical disc.
The diffraction structure is configured so that the spherical aberration generated thereby varies in accordance with the wavelength of the entering laser beam. In other words, the diffraction structure is designed so as to have wavelength dependency.
The spherical aberration caused by the objective lens provided with the diffraction structure mentioned above increases/decreases as the wavelength of the laser beam passed therethrough changes, and cancels the increase/decrease of the spherical aberration caused by the difference of the protective layer thickness of the optical disc to be handled. As a result, the optical system can form a beam spot of a desired size on the recording layer of each type of the optical disc.
Recently, a large amount of the objective lenses are made of plastic in order to reduce the cost. The spherical aberration caused by the plastic lens has a temperature dependency. That is, the spherical aberration varies with the temperature of the plastic lens since shape and refraction index of the lens changes as the temperature of the lens increases or decreases. Accordingly, if a plastic lens is employed for the objective lens, the lens should be designed by also taking into account the temperature dependency of the spherical aberration.
However, if the diffraction structure mentioned above is also designed to suppress the temperature dependency of the spherical aberration, both of the acceptable range of the laser beam wavelength and the acceptable range of the objective lens temperature become significantly restricted. The narrow wavelength range does not allow large wavelength deviation of the laser beam from the design wavelength and forces the use of high-end laser sources which are costly. The narrow temperature range restricts the environment in which the optical disc drive can be operated.
Therefore, there is a need for an optical system for an optical disc drive that handles different types of optical discs, which optical system is capable of correcting spherical aberration caused by the protection layer of the optical disc while allowing the laser beam wavelength deviating from the design wavelength.
There is also a need for an optical system for an optical disc drive that handles different types of optical discs, which optical system is hardly affected by temperature change even if plastic lens is employed as an objective lens thereof.

Optical system with objective lens having diffraction structure


There is provided a thermal transfer recording medium capable of obtaining high transfer sensitivity during high-speed printing, that is, decreasing the amount of a dye used in a dye layer; and preventing abnormal transfer during printing even after storage in a high-temperature and high-humidity environment. The thermal transfer recording medium (1) contains: a heat-resistant sliding layer (40) that is formed on one surface of a substrate (10); and an undercoat layer (20) and a dye layer (30) that are sequentially laminated on the other surface of the substrate (10), in which the undercoat layer (20) contains, as major components, a polyvinyl pyrrolidone and a polyvinyl alcohol having a crystallinity degree of 15% or higher, and the dye layer (30) contains an anthraquinone-based thermal transfer dye.

Typically, a thermal transfer recording medium is called a thermal ribbon and refers to an ink ribbon used in a thermal transfer printer. In such a thermal transfer recording medium, a thermal transfer layer is formed on one surface of a substrate, and a heat-resistant sliding layer (so-called, "backcoat layer") is formed on the other surface of the substrate. The thermal transfer layer described herein is a layer containing ink, in which this ink is sublimated (sublimation thermal transfer type) or fused (fusion thermal transfer type) by heat generated in a thermal head of a printer to be transferred to a transfer medium side.
Currently, by using the sublimation thermal transfer type among the thermal transfer types in combination with high-performance printers, various full-color images can be simply formed. Therefore, the sublimation thermal transfer type is widely used for self-printing of digital camera photos and for printing cards such as ID cards, printed materials for fun, and the like. Along with such diversification of uses, demands for decrease in size, increase in speed, decrease in cost, and durability of printed materials to be obtained have increased. In addition, recently, a thermal transfer recording medium including, on the same side of a substrate sheet, a protective layer or the like that imparts durability to printed materials and plural thermal transfer layers that are provided so as not to overlap the protective layer or the like has been widely used.
In such circumstances, along with the diversification and the expansion of uses, the printing speed of printers has been further increased. As a result, in a thermal transfer recording medium of the related art, a problem that a sufficient print density is not obtained has occurred. Therefore, in order to increase transfer sensitivity, an attempt to improve transfer sensitivity during printing has been made by decreasing the thickness of a thermal transfer recording medium. However, when the transfer sensitivity is increased, during the manufacturing of a thermal transfer recording medium or printing, wrinkling may occur due to heat, pressure, or the like. In addition, in some cases, a thermal transfer recording medium may be broken.
In addition, an attempt to improve print density and transfer sensitivity during printing has been made by increasing a ratio of dye/resin (Dye/Binder) on a dye layer of a thermal transfer recording medium. However, when the amount of a dye is increased, not only the cost increases, but also a part of the dye may be transferred (set off) to a heat-resistant sliding layer of a thermal transfer recording medium during winding in a manufacturing process. In addition, during rewinding as a subsequent process, the transferred dye may be transferred again (set off again) to another color dye layer or a protective layer. When this contaminated layer is thermally transferred to a transfer medium, a different color from a designated color may be printed, or so-called scumming may occur.
In addition, an attempt to increase energy during image forming not only on a thermal transfer recording medium side but also on a printer side has been made. However, when the energy during image forming is increased, power consumption is increased, and the service life of a thermal head of a printer may be decreased. In addition, fusion bonding between a dye layer and a transfer medium, so-called, abnormal transfer is likely to occur. To deal with this problem, when a large amount of release agent is added to a dye layer or a transfer medium to prevent abnormal transfer, bleeding or scumming may occur on an image.
In order to satisfy the above-described demands, several methods are proposed. For example, PTL 1 proposes a thermal transfer sheet including an adhesive layer between a substrate and a dye layer, the adhesive layer containing a polyvinyl pyrrolidone resin and a modified polyvinyl pyrrolidone resin.
In addition, PTL 2 proposes a thermal transfer sheet including an adhesive layer between a substrate and a dye layer, the adhesive layer containing a thermoplastic resin such as a polyvinyl pyrrolidone resin or a polyvinyl alcohol resin and colloidal inorganic pigment ultrafine particles.


Locking bolt assembly comprises a bush (9) fixed in use with respect to a structure to which a bolt of the assembly is to be engaged and a socket (1) carried on the bush (9) and provided with locking means (6) for preventing rotation of the socket (1) on the bush (9) but permitting limited longitudinal movement thereon. The bolt is threaded and has a head (3) dimensioned for rotational locking engagement within socket (1). A coil spring (7) urges the head (3) and socket (1) into rotational locking engagement. In use the socket (1) may be moved longitudinally with respect to said bush (9) against the action of the spring (7) from a position in which the head (3) and the socket (1) are radically locked, to a position in which the head (3) is freed for rotation and engagement with a co-operating nut fixed to the structure.

This invention relates to Screw Threaded Locking Bolt assemblies, and in particular to such assemblies for holding or securing items of equipment in aircraft.
According to the invention there is provided a locking bolt assembly comprising:
bush means for axially supporting a threaded bolt of said assembly, said bush means being adapted to be fixed in use with respect to a structure to which said bolt is to be engaged;
socket means carried on said bush means and being internally dimensioned for rotational locking engagement of a head of said threaded bolt and comprising means for preventing rotation of said socket means on the bush but permitting limited longitudinal movement thereon, said head of said threaded bolt being correspondingly dimensioned for rotational locking engagement within said socket; and,
resilient means for urging said head and said socket means into said rotational locking engagement,
so that in use said socket means may be moved longitudinally with respect to said bush means against the action of said resilient means from a position in which said head and said socket means are radically locked, to a position in which said head is freed for rotation and engagement with a co-operating nut of said assembly fixedly mounted on said structure.
We have found our invention particularly useful in situations where the nut portion of a nut and bolt assembly for equipment installation is inaccessibly built into an aircraft structure and such that the nut per se cannot have any self-locking element in it due to the high frequency of equipment removal for maintenance purposes.

British Aerospace Public Limited Company


This invention features an antithrombosis enzyme extracted and purified from the snake venom of Southern-Anhui Agkistrodon acutus and pharmaceutical uses thereof.

This invention relates to an antithrombosis enzyme derived from the snake venom of an acutus species.
Anti-thrombus drugs extracted from acutus venom have been reported in the literature, e.g., xe2x80x9cPreparation and Study of Anti-thrombus Enzymes No. 1, 2, and 3xe2x80x9d, Journal of the Medical Univ. of China, 1989.18 (special issue); and xe2x80x9cTechnique for Extracting Definriogenase from the venom of Agkistrodon acutus,xe2x80x9d CN 92102645.5 (CN 1065680.A). These anti-thrombus drugs are proteinase components extracted from the snake venom. They act like thrombase with hemorrhagic side-effect. In addition, some of these products are not single component proteinase, but a mixture of different components, which limits the pharmaceutical application of these drugs in human.
Other snake venom derived pharmaceutical products include Ancrod, Trigtamin and Integrilin (see Matsuzaki et al., Biochem. Biophy. Res. Com. 220(2):382-387, 1996; Morita et al., Natural Toxins II, pp187-196, Edited by B. R. Singh and A. T. Tu, Plenum Press, New York, 1996; U.S. Pat. Nos. 5,196,403, 5,242,810, 5,453,370, 4,017,012, 5,344,783, 5,686,571, 5,523,292, 5,066,592 and 5,342,830).
Within the scope of this invention, Applicant has extracted, purified and cloned an antithrombosis enzyme (ATE, also called a fibrinolytic enzyme in the provisional application) from the venom of Southern-Anhui Agkistrodon acutus in China. This enzyme degrades both fibrinogen and fibrin, and inhibits platelet aggregation. It is useful for preventing and treating vaso-occulusive and thromboembolic disorders, including, but not limited to, myocardial infarction, restenosis, peripheral anginaphraxis, angiopathic thrombosis, cerebral thrombosis, ischemic cerebral vascular diseases, unstable angina, acute thrombosis, unstable stenocardia and hemiparalysis caused by cerebral thrombosis.
The present invention provides methods and compositions for preventing or treating diseases and processes mediated (caused or aggravated) by undesired and/or uncontrolled thrombosis by administering to a human or animal a composition containing or capable of expressing the antithrombosis enzyme in a dosage sufficient to prevent, reduce, eliminate or inhibit thrombosis. The antithrombosis enzyme may be substantially purified or in a crude extract. The antithrombosis enzyme may be produced from snake venom, chemically synthesized or expressed from a recombinant vector. It may also be combined with a pharmaceutically acceptable excipient or carrier, and optionally sustained-release compounds or compositions, such as biodegradable polymers, to form therapeutic compositions.
The present invention is particularly useful for treating or preventing acute and recurrent cerebral thrombosis, myocardial infarction, restenosis, peripheral anginaphraxis, angiopathic thrombosis, ischemic cerebral vascular thrombosis, unstable angina, unstable stenocardia, and thromboangitis obliterans. Administration of the antithrombosisi enzyme can prevent blood clot formation and reduce, diminish or dissolve blood clot. The antithrombosis enzyme may also be used in combination with other compositions and procedures for the treatment of thrombosis. For example, it may be used in combination with a thrombolytic agent known in the art, which includes, but is not limited to, tissue plasminogen activator purified from natural sources, recombinant tissue plasminogen activator, streptokinase, urokinase, prourokinase, anisolated streptokinase plasminogen activator complex (ASPAC), animal salivary gland plasminogen activators and known, biologically active derivatives of any of the above. In these combination compositions, the antithrombosis enzyme and other thrombolytic agent work in a complementary fashion to dissolve blood clots, resulting in decreased reperfusion times and increased reocclusion times in patients treated with them. The use of the antithrombosis enzyme in the compositions of this invention advantageously allows the administration of a thrombolytic reagent in dosages previously considered too low to result in thrombolytic effects if given alone. This avoids some of the undesirable side effects associated with the use of thrombolytic S agents, such as bleeding complications. The compositions of this invention may also be used before, concurrent with, or after angioplastic or fibrolytic treatment to prevent or treat restenosis.
Thus, in a first aspect, this invention features an isolated, purified or recombinant antithrombosisi enzyme which has (i) a molecular weight of between about 28 kD and about 32 kD when analyzed by polyacrylamide gel electrophoresis, (ii) an aspartic acid content of between about 2% and about 5%, and (iii) a glutamic acid content of between about 2% and about 5%. This enzyme has the ability to hydrolyze fibrin, dissolve thrombus, inhibit platelet aggregation, and inhibit the formation of thrombus.
In a preferred embodiment, the enzyme has fibrinolytic activity of no less than one fibrinolytic activity unit per mg protein. In another preferred embodiment, the enzyme has fibrinolytic activity of between about one and about three fibrinolytic activity units per mg protein. This enzyme specifically hydrolyzes the A (xcex1) chain of fibrinogen. This enzyme completely or almost completely inhibits human platelet aggregation induced by agonists such as ADP, Epinephrine, Thrombin and collagen. This enzyme has no detectable hydrolysis effect on casein. The enzyme dissolves arterial and venous thrombus in a mammal, prevent thrombosis, reduce blood viscosity, and improve microcirculation. At the same time, this enzyme has minimum effect on the thromosystem, resulting in little possibility of hemorrhage. This enzyme is different from related enzymes from other Acutus species (e.g., IX/X binding proteins, Matsuzaki et al., Biochem. Biophy. Res. Com. 220(2):382-387, 1996; Morita et al., Natural Toxins II, pp187-196, Edited by B. R. Singh and A. T. Tu, Plenum Press, New York, 1996) in that this enzyme has both fibrinolytic activity and antiplatelet aggregation activity, and less hemorrhagic activity.
In other preferred embodiments, this enzyme is purified from Southern-Anhui Agkistrodon acutus. The enzyme is a heterodimer of A chain and B chain each with a molecular weight of about 14 KD to about 16 KD. The A chain has at its amino end the following sequence Sequence ID No. 3:
Asp-Cys-Ser-Ser-Asp-Trp-Ser-Ser-Tyr-Glu-Gly-His-Cys-Tyr-Lys-Val-Phe-Lys-Gln-Ser-Lys-Thr-Trp-Thr-Asp-Ala-Glu-Ser-Phe-, and the B chain has at its amino end the following sequence Sequence ID No. 4:
Asp-Cys-Pro-Ser-Glu-Trp-Ser-Ser-Tyr-Glu-Gly-Phe-Cys-Tyr-Lys-Pro-Phe-. Preferrably, the A chain and the B chain are linked by one or more disulfide bond.
In other preferred embodiments, this antithrombosis enzyme contains Ca++ and/or has aspartic acid at its amino terminus.
By xe2x80x9cisolatedxe2x80x9d in reference to a polypeptide is meant a polypeptide isolated from a natural source or synthesized. The isolated polypeptides of the present invention are unique in the sense that they are not found in a pure or separated state in nature. Use of the term xe2x80x9cisolatedxe2x80x9d indicates that a naturally occurring amino acid sequence has been removed from its normal cellular environment. Thus, the sequence may be in a cell-free solution or placed in a different cellular environment. The term does not imply that the sequence is the only amino acid chain present, but that it is the predominate sequence present (at least 10-20% more than any other sequence) and is essentially free (about 90-95% pure at least) of non-amino acid material naturally associated with it.
By xe2x80x9cenrichedxe2x80x9d in reference to a polypeptide is meant that the specific amino acid sequence constitutes a significantly higher fraction (2-5 fold) of the total of amino acids present in the cells or solution of interest than in normal or diseased cells or in the cells from which the sequence was taken. This could be caused by a person by preferential reduction in the amount of other amino acids present, or by a preferential increase in the amount of the specific amino acid sequence of interest, or by a combination of the two. However, it should be noted that enriched does not imply that there are no other amino acid sequences present, just that the relative amount of the sequence of interest has been significantly increased. The term xe2x80x9csignificantlyxe2x80x9d here is used to indicate that the level of increase is useful to the person making such an increase, and generally means an increase relative to other amino acids of about at least 2 fold, more preferably at least 5 to 10 fold or even more. The term also does not imply that there is no amino acid from other sources. The amino acid from other sources may, for example, comprise amino acid encoded by a yeast or bacterial genome, or a cloning vector such as pUC19. The term is meant to cover only those situations in which man has intervened to elevate the proportion of the desired amino acid.
By xe2x80x9cpurifiedxe2x80x9d in reference to a polypeptide does not require absolute purity (such as a homogeneous preparation); instead, it represents an indication that the sequence is relatively purer than in the natural environment (compared to the natural level this level should be at least 2-5 fold greater, e.g., in terms of mg/ml). Purification of at least one order of magnitude, preferably two or three orders, and more preferably four or five orders of magnitude is expressly contemplated. The substance is preferably free of contamination at a functionally significant level, for example 90%, 95%, or 99% pure.
By xe2x80x9crecombinantxe2x80x9d is meant a polypeptide or enzyme produced by recombinant DNA techniques such that it is distinct from a naturally occurring polypeptide either in its location (e.g., present in a different cell or tissue than found in nature), purity or structure. Generally, such a recombinant polypeptide will be present in a cell in an amount different from that normally observed in nature. This invention features recombinant ATE and its fragments obtainable using techniques known to those skilled in the art, including those described in McDonnell et al., U.S. patent application Ser. No. 08/223,943 filed Apr. 6, 1994, Evans et al., U.S. Pat. No. 5,071,773, and PCT application, PCT/US91/00399 filed Jan. 22, 1991 (International Publication No. WO 91/12258), incorporated by reference herein.
In a second aspect, this invention features isolated, purified or recombinant polypeptide fragments of the A chain and the B chain of the antithrombosis enzyme. Preferably, these fragments contain no less than 15, 20, 30 or 40 contiguous amino acid residues from the A or B chain. For example, these fragments may contain no less than 15, 20, 30 or 40 contiguous amino acid residues from SEQ ID NO: 2. Such polypeptide fragments can be synthesized chemically or expressed from recombinant vectors. They are useful for generating monoclonal antibodies which bind to both the polypeptide fragments and the intact antithrombosis enzyme (see U.S. Pat. Nos. 5,733,738, 5,015,571, incorporated by reference herein). Monoclonal antibodies so generated can be attached to solid support and used to purify the antithrombosis enzyme from crude venom extract or cell extract by affinity chromatography.
The recombinant polypeptide fragments of the A chain and the B chain can be expressed from recombinant nucleic acid encoding such polypeptide fragments. For example, polypeptide fragments of the A chain can be expressed from recombinant nucleic acid containing no less than 45, 60, 90 or 120 contiguous nucleotides from SEQ ID NO: 1 or its fully complementary strand of the same length and a promoter effective to initiate transcription of the contiguous nucleotides in a host cell.
In yet another aspect the invention features an isolated, enriched, or purified antibody (e.g., a monoclonal or polyclonal antibody) having specific binding affinity to the antithrombosis enzyme or a fragment thereof. The antibody contains a sequence of amino acids that is able to specifically bind to the antithrombosis enzyme. The antibody may be prepared with techniques known to those skilled in the art, including, but not limited to, those disclosed in Niman, PCT application PCT/US88/03921 (International Publication No. WO 89/04489), incorporated by reference herein. By xe2x80x9cspecific binding affinityxe2x80x9d is meant that the antibody will bind to the ATE in a certain detectable amount but will not bind other polypeptides to the same extent under identical conditions.
In another aspect the invention features a hybridoma which produces an antibody having specific binding affinity to the antithrombosis enzyme or a fragment thereof. By xe2x80x9chybridomaxe2x80x9d is meant an immortalized cell line which is capable of secreting an antibody.
In another aspect, the invention features an isolated, purified, enriched or purified recombinant nucleic acid encoding the antithrombosis enzyme, a chain of the enzyme, or fragments of the A chain or B chain. For example, the recombinant nucleic acid contains a sequence contiguously encoding SEQ ID NO: 2 and a promoter effective to initiate transcription of the conding sequence in a host cell. In particular, the recombinant nucleic acid contains SEQ ID NO: 1 operably linked to a promoter.
By xe2x80x9cisolatedxe2x80x9d in reference to nucleic acid is meant DNA or RNA isolated from a natural source or synthesized. The isolated nucleic acid of the present invention is unique in the sense that it is not found in a pure or separated state in nature. Use of the term xe2x80x9cisolatedxe2x80x9d indicates that a naturally occurring sequence has been removed from its normal cellular environment. Thus, the sequence may be in a cell-free solution or placed in a different cellular environment. The term does not imply that the sequence is the only nucleotide chain present, but does indicate that it is the predominate sequence present (at least 10-20% more than any other nucleotide sequence) and is essentially free (about 90-95% pure at least) of non-nucleotide material naturally associated with it. Therefore, the term does not encompass an isolated chromosome encoding the ATE.
By xe2x80x9cpurifiedxe2x80x9d in reference to nucleic acid does not require absolute purity (such as a homogeneous preparation); instead, it represents an indication that the sequence is relatively purer than in the natural environment (compared to the natural level this level should be at least 2-5 fold greater, e.g., in terms of mg/ml). Individual clones isolated from a cDNA library may be purified to electrophoretic homogeneity. The claimed DNA molecules obtained from these clones could be obtained directly from total DNA or from total RNA. The cDNA clones are not naturally occurring, but rather are preferably obtained via manipulation of a partially purified naturally occurring substance (messenger RNA). The construction of a cDNA library from mRNA involves the creation of a synthetic substance (cDNA) and pure individual cDNA clones can be isolated from the synthetic library by clonal selection of the cells carrying the cDNA library. Thus, the process which includes the construction of a cDNA library from mRNA and isolation of distinct cDNA clones yields an approximately 106-fold purification of the native message. Thus, purification of at least one order of magnitude, preferably two or three orders, and more preferably four or five orders of magnitude is expressly contemplated.
By xe2x80x9cenrichedxe2x80x9d in reference to nucleic acid is meant that the specific DNA or RNA sequence constitutes a significantly higher fraction (2-5 fold) of the total DNA or RNA present in the cells or solution of interest than in normal or diseased cells or in the cells from which the sequence was taken. This could be caused by a person by preferential reduction in the amount of other DNA or RNA present, or by a preferential increase in the amount of the specific DNA or RNA sequence, or by a combination of the two. However, it should be noted that enriched does not imply that there are no other DNA or RNA sequences present, just that the relative amount of the sequence of interest has been significantly increased in a useful manner and preferably separate from a sequence library. The term xe2x80x9csignificantlyxe2x80x9d here is used to indicate that the level of increase is useful to the person making such an increase, and generally means an increase relative to other nucleic acids of about at least 2 fold, more preferably at least 5 to 10 fold or even more. The term also does not imply that there is no DNA or RNA from other sources. The DNA from other sources may, for example, comprise DNA from a yeast or bacterial genome, or a cloning vector such as pUC19. This term distinguishes from naturally occurring events, such as viral infection, or tumor type growths, in which the level of one mRNA may be naturally increased relative to other species of mRNA. That is, the term is meant to cover only those situations in which a person has intervened to elevate the proportion of the desired nucleic acid.
By xe2x80x9crecombinantxe2x80x9d in reference to a nucleic acid is meant the nucleic acid is produced by recombinant DNA techniques such that it is distinct from a naturally occurring nucleic acid.
By xe2x80x9ccomprisingxe2x80x9d is meant including, but not limited to, whatever follows the word xe2x80x9ccomprisingxe2x80x9d. Thus, use of the term xe2x80x9ccomprisingxe2x80x9d indicates that the listed elements are required or mandatory, but that other elements are optional and may or may not be present. By xe2x80x9cconsisting ofxe2x80x9d is meant including, and limited to, whatever follows the phrase xe2x80x9cconsisting ofxe2x80x9d. Thus, the phrase xe2x80x9cconsisting ofxe2x80x9d indicates that the listed elements are required or mandatory, and that no other elements may be present. By xe2x80x9cconsisting essentially ofxe2x80x9d is meant including any elements listed after the phrase, and limited to other elements that do not interfere with or contribute to the activity or action specified in the disclosure for the listed elements. Thus, the phrase xe2x80x9cconsisting essentially ofxe2x80x9d indicates that the listed elements are required or mandatory, but that other elements are optional and may or may not be present depending upon whether or not they affect the activity or action of the listed elements.
The invention also features a nucleic acid probe for the detection of a nucleic acid encoding the antithrombosis enzyme, its A chain or B chain, or fragments thereof. In an example, the nucleic acid probe contains nucleic acid that will hybridize to SEQ ID NO: 1, but not to the nucleic acid sequence of the IX/X-binding protein (Matsuzaki et al., Biochem. Biophy. Res. Com. 220(2):382-387, 1996) under high stringency hybridization conditions. By xe2x80x9chigh stringency hybridization conditionsxe2x80x9d is meant those hybridizing conditions that (1) employ low ionic strength and high temperature for washing, for example, 0.015 M NaCl/0.0015 M sodium citrate/0.1% SDS at 50xc2x0 C.; (2) employ during hybridization a denaturing agent such as formamide, for example, 50% (vol/vol) formamide with 0.1% bovine serum albumin/0.1% Ficoll/0.1% polyvinylpyrrolidone/50 mM sodium phosphate buffer at pH 6.5 with 750 mM NaCl, 75 mM sodium citrate at 42xc2x0 C.; or (3) employ 50% formamide, 5xc3x97SSC (0.75 M NaCl, 0.075 M Sodium pyrophosphate, 5xc3x97 Denhardt""s solution, sonicated salmon sperm DNA (50 g/ml), 0.1% SDS, and 10% dextran sulfate at 42xc2x0 C., with washes at 42xc2x0 C. in 0.2xc3x97SSC and 0.1% SDS. Under stringent hybridization conditions only highly complementary nucleic acid sequences hybridize. Preferably, such conditions prevent hybridization of nucleic acids having 1 or 2 mismatches out of 20 contiguous nucleotides.
In another aspect, the invention describes a recombinant cell or tissue containing an exogenous nucleic acid coding for the antithrombosis enzyme, its A chain or B chain, or fragments thereof.
In another aspect, this invention features a pharmaceutical composition for reducing or eliminating thrombosis in a human or animal subject. This composition contains a pharmaceutically effective amount of the antithrombosis enzyme and a pharmaceutically acceptable carrier.
By xe2x80x9cpharmaceutically effective amountxe2x80x9d is meant an amount of a pharmaceutical compound or composition having a therapeutically relevant effect on thrombosis or diseases or pathological conditions related to thrombosis. A therapeutically relevant effect prevents or relieves to some extent one or more symptoms of thrombosis or diseases or pathological symptoms related to thrombosis in a patient or returns to normal either partially or completely one or more physiological or biochemical parameters associated with or causative of thrombosis or diseases or pathological symptoms related to thrombosis, e.g., reducing or inhibiting thrombosis; curing, reducing, or inhibiting diseases and processes that are mediated by thrombosis.
In another aspect, this invention features a method of reducing or inhibiting thrombosis in a human or animal subject by administering to the subject a pharmaceutically effective amount of the antithrombosis enzyme.
In another aspect, this invention features a method of isolating and/or purifying the antithrombosis enzyme. In this method, a crude extract containing the antithrombosis enzyme, e.g., a crude extract of the snake venom of Southern-Anhui Agkistrodon acutus, is dissolved in a buffer and brought into contact with an anion exchange column, the elution sample with fibrinolytic activity and antiplatelet aggregation activity is collected, concentrated and separated by gel permeation chromatography, and the elution sample with fibrinolytic activity and antiplatelet aggregation activity is collected and desalted. This invention features an antithrombosis enzyme isolated by this process.
The present invention also provides recombinant DNA molecules characterized by a DNA sequence encoding the antithrombosis enzyme alone or fused to a DNA sequence which codes for a conventional anti-thrombosis polypeptide. The synthesis of these DNA molecules may be achieved by methods well known in the art. For example, these recombinant DNA molecules may be isolated from an Agkistrodon acutus venom gland cDNA library. The synthesis of cDNA libraries and the choice of vector into which the cDNA molecules may be cloned are conventional techniques. The invention also relates to hosts transformed with these recombinant DNA molecules, as well as to the recombinant products expressed by these hosts. And the present invention relates to chemically synthesized antithrombosis enzyme. Such synthetic polypeptides may be prepared by conventional chemical synthesis techniques, for example, synthesis on a solid support.
This invention further relates to pharmaceutically acceptable compositions and combinations, and methods utilizing these natural, recombinant or synthetic antiplatelet polypeptides in the treatment extracorporeal blood.
By xe2x80x9cextracorporeal bloodxe2x80x9d is meant blood that is removed from a patient, subjected to extracorporeal treatment, and returned to the patient in processes such as dialysis, blood filtration or blood bypass during surgery. The term also includes blood products which are stored extracorporeally for eventual administration to a patient. Such products include whole blood, platelet concentrates and other blood fractions in which inhibition of platelet aggregation and platelet release is desired.
Other features and advantages of the invention will be apparent from the following drawing and detailed description of the invention and from the claims.

Antithrombosis enzyme from the snake venom of agkistrodon acutus

Hefei-Siu-Fung USTC Pharmaceutical Co., Ltd.


A composite shadow ring that is constructed of an upper ring and a lower ring assembled together by a plurality of dowel pins and a method for using the ring. The upper ring and the lower ring each has a predetermined outside diameter that is substantially the same, a planar top surface and a planer bottom surface parallel to the planar top surface. Each of the planar bottom surface of the upper ring and the planar top surface of the lower ring has at least two blind holes formed therein. A plurality of dowel pins are used to frictionally engage the at least two blind holes in the upper ring and the at least two blind holes in the lower ring.

In the fabrication of modern integrated circuit devices, one of the key requirements is the ability to construct plugs or interconnects in reduced dimensions such that they may be used in a multi-level metalization structure. The numerous processing steps involved require the formation of via holes for the plug or interconnect in a dimension of 0.5 μm or less for high-density logic devices. For instance, in forming tungsten plugs by a chemical vapor deposition method, via holes in such small dimensions must be formed by etching through layers of oxide and spin-on-glass materials at a high etch rate. A high-density plasma etching process utilizing a fluorine chemistry is thus used for such via formation process.
The via hole formation process can be enhanced by improving the etch directionality by a mechanism known as sidewall passivation to improve the anisotropy of the etching process. By utilizing a suitable etchant gas and suitable reactor parameters, an etch-inhibiting film of a polymeric nature can be formed on vertical sidewalls. The etch-inhibiting film slows down or completely stops any possible lateral etching of horizontal surfaces in the via hole. For instance, when a fluorine-containing etchant gas such as CFH3 is used, a fluorine-type polymeric film is formed on the sidewalls. Many photoresist materials may also contribute to the formation of polymeric films on the sidewalls. After the sidewall is coated with a polymeric film, it is protected by the inhibitor film to preserve the line width or via hole diameter control.
In a modern etch chamber, an electrostatic chuck (or E-chuck), is frequently used in which the chuck electrostatically attracts and holds a wafer that is positioned on top. The use of E-chuck is highly desirable in the vacuum handling and processing of wafers. In contrast to a conventional method of holding wafers by mechanical clamping means where only slow movement is allowed during wafer handling, an E-chuck can hold and move wafers with a force equivalent to several tens of Torr pressure. Another advantage for the E-chuck is that no particle generation or contamination problem can occur since there are no moving parts acting on the wafer. Moreover, the electrostatic force utilized on an E-chuck is sufficient in preventing bowing of a wafer which normally occurs in mechanical clamping and thus promotes uniform heat transfer over the entire wafer surface.
In an etch chamber equipped with a plasma generating device and an E-chuck, a shadow ring may be utilized as a seal around the peripheral edge of the wafer. The shadow ring, also known as a focus ring, is utilized for achieving a more uniform plasma distribution over the entire surface of the wafer and for restricting the distribution of the plasma cloud to only the wafer surface area. The uniform distribution function may be further enhanced by a RF bias voltage applied on the wafer during a plasma etching process. Another function served by the shadow ring is sealing at the wafer level the upper compartment of the etch chamber which contains the plasma from the lower compartment of the etch chamber which contains various mechanical components for controlling the E-chuck. This is important since it prevents the plasma from attacking the hardware components contained in the lower compartment of the etch chamber. In order to survive high temperature and hostile environments, a shadow ring is frequently constructed of a ceramic material such as quartz.
In an etch chamber equipped with a high density plasma and an E-chuck, problems sometimes arise in the operation of the E-chuck. High density gas plasma formed has a short debye length and consequently very small sheaths are formed at boundaries of objects that are present in the gas plasma. The debye length is defined as the distance from the plasma at which the electron density drops to 1e/ of the electron density in the bulk plasma. The debye length can be calculated by first dividing the electron temperature by the electron density, and then taking the square root. The typical electron temperature in a high density plasma is low, i.e., on the order of a few eV. On the other hand, the electron density is high, i.e., on the order of 1011˜1012 electrons per cubic centimeter. This leads to a small debye length on the order of approximately several tenths of a millimeter. Gaps found in a process chamber that is larger than a few debye length may either cause a gas breakdown or the plasma may be extracted into the sufficiently large gaps.
In order to prevent the plasma from affecting the voltage on the electrode of the E-chuck, the electrode positioned in a plasma chamber must be sufficiently isolated from the plasma. In a typical E-chuck positioned in a high density plasma, the electrode has a voltage applied to it with respect to a ground reference point. The wafer is referenced back to the same ground reference by the plasma. The effective voltage for the electrostatic clamping of the wafer is then the voltage which appears across the E-chuck dielectric layer between the isolated electrode and the wafer. The voltage applied to the isolated electrode may be positive or negative with respect to the chamber ground. However, the electrostatic force depends on the algebraic difference between the wafer and the isolated electrode.
When the gaps around an E-chuck exceed several debye lengths, plasma may either be generated in the gaps or may be extracted into the gaps. When the plasma contacts the electrostatic chuck which has an imperfect dielectric layer or the E-chuck electrode, a current may flow between the E-chuck and the plasma. The voltage at the E-chuck electrode is therefore affected. Typically, the magnitude of the E-chuck voltage is reduced when a current flows between the chuck and the plasma which leads to a reduction in the electrostatic force. The efficiency of the E-chuck for holding a wafer is therefore affected. Ideally, the solution to the problem is to shield the E-chuck from the high density plasma by limiting gaps between the E-chuck and a shadow ring around the E-chuck to less than several debye lengths. In such an ideal situation, plasma can be prevented from being generated in the gaps or being extracted into the gaps. Since the ideal equipment conditions cannot be achieved in a manufacturing environment, the generation of plasma in the gaps or the extraction of plasma into the gaps and therefore attacking a shadow ring which is normally fabricated of quartz cannot be avoided. In a normal fabrication environment, it has been found that a quartz shadow ring would only survive about one preventive maintenance cycle or about 2,000 wafers. The corrosion occurred on the surface of the quartz shadow ring is usually severe enough that it must be replaced during a preventive maintenance procedure.
Referring initially to FIG. 1, wherein a conventional etch chamber 10 which is equipped with a shadow ring 12 installed around an electrostatic chuck 16 is shown. The etch chamber 10 is equipped with a coil antenna 14 as a plasma source in a reaction chamber 20 formed by a silicon ceiling block 22, a dome-shaped sidewall 24, a chamber wall liner 26 and the electrostatic chuck 16. The dome-shaped sidewall 24 and the chamber wall liner 26 are normally fabricated of quartz. The chamber wall liner 26 may be equipped with an opening for the passage of a wafer paddle in loading and unloading wafers. It may be removed from the vacuum chamber 10 for cleaning.
The shadow ring 12 is positioned inside the plasma reaction chamber 20 which can be lifted up to a process position by positioning pins 32. The positioning pins 32 lift the shadow ring 12 away from the wafer when a wafer is being loaded or unloaded. A multiplicity of cooling gas channels 34 is provided inside the electrostatic chuck 16 at near its top surface 36. A high heat conductivity gas such as helium can be circulated through the cooling gas channels 34 to provide a suitable gas pressure on the bottom side of wafer 30 for transferring heat away from the wafer to the water-cooled E-chuck 16 during an etch process. The supply lines for the cooling gas to channel 34 are not shown. The electrostatic chuck 16 is aligned by an electrostatic chuck collar 38. The etching gas is fed into chamber 20 through gas inlet 28. A thermal coupler 42 is mounted in the silicon ceiling block 22 for controlling temperature.
U.S. Pat. No. 6,022,809, issued to Fan, and assigned to the common assignee of the present invention, discloses a composite shadow ring that has a body portion of a ring shape made of a material substantially of silicon oxide and an insert portion which is intimately jointed to the body portion and is concentric with the body portion. The composite shadow ring 12 is further shown in FIGS. 1 and 1A. As shown in a detailed view in FIG. 1A, the shadow ring 12 is constructed by two major parts of a body portion 18 and an insert portion 48. The body portion has a ring shape and is made of a material that is substantially of silicon oxide, while the insert portion is intimately joined to the body portion 18 by frictional engagement and is juxtaposed to a plasma cloud formed in the etch chamber when the shadow ring 12 is positioned around wafer 30. The insert ring 48 has a diameter that is smaller than a diameter of the body portion 18 and is fabricated of a material that does not generate oxygen upon bombardment by a plasma, particularly by a fluorine-containing plasma. The insert ring 48 is engaged to the body portion 18 by frictional engagement or by any other mechanical means. U.S. Pat. No. 6,022,809 is hereby incorporated by reference in its entirety.
In still another improved design of composite shadow ring, shown in FIGS. 2 and 2A, the composite shadow ring 50, shown in a cross-sectional view in FIG. 2 and in a plane view in FIG. 2A, is constructed by an upper ring 54 and a lower ring 56. The advantage of this configuration of two flat, concentric rings assembled together by locating pins 60 is that only the upper ring 54 is exposed to the plasma ions in the etch chamber and therefore, only the upper ring 54 is subjected to the etching effect of the plasma. As a result, only the upper ring 54 needs to be replaced after repeated usage of the composite shadow ring 50. For instance, a commercially available composite shadow ring 50 is constructed by an upper ring 54 fabricated of silicon and a lower ring 56 fabricated of silicon dioxide.
While the composite shadow ring 50 shown in FIG. 2 presents the benefit that only the upper ring 54 is subjected to plasma corrosion and therefore only the upper ring 54 needs to be replaced, it presents a processing problem in that the lower ring 56 is difficult to clean during a preventive maintenance procedure. The locating pins 60 which are formed of quartz material integrally with or inserted into the lower ring 56 are frequently subjected to breakage during the cleaning procedure. When one or more of the locating pins 60 break off from the lower ring 56, the lower ring can no longer engage the upper ring 54 and must be scrapped. Broken locating pins 60 therefore leads to the complete replacement of the composite shadow ring 50.
It is therefore an object of the present invention to provide a composite shadow ring that is constructed of an upper ring and a lower ring that does not have the drawbacks or shortcomings of the conventional composite shadow ring.
It is another object of the present invention to provide a composite shadow ring wherein the likelihood of damaging the ring during a preventive maintenance cleaning procedure is reduced.
It is a further object of the present invention to provide a composite shadow ring that is constructed of an upper ring and a lower ring each equipped with a plurality of apertures.
It is another further object of the present invention to provide a composite shadow ring that is constructed of an upper ring and a lower ring which are assembled together by a plurality of dowel pins inserted into apertures provided in the upper and lower rings.
It is still another object of the present invention to provide a composite shadow ring that is constructed of an upper ring and a lower ring assembled together by a plurality of reinforced plastic pins engaging apertures in the upper and lower rings.

Composite shadow ring assembled with dowel pins and method of using