A method and apparatus for selectively sintering a layer of powder to produce a part comprising a plurality of sintered layers. The apparatus includes a computer controlling a laser to direct the laser energy onto each layer of the powder to produce a sintered mass corresponding to a cross-section of the part. For each cross-section, the aim of the laser beam is scanned over a layer of powder and the beam is switched on to sinter only the powder within the boundaries of the cross-section. Powder is applied and successive layers sintered until a completed part is formed. Also disclosed is a method of forming a part by interaction of material in the powder layer with reactants in the surrounding atmosphere, at locations of the powder irradiated by the energy, or laser, beam. The reaction may be nitridation, oxidation or carburization of the powder, with the product being a chemical compound of one or more constituents in the powder with one or more gases in the atmosphere. Alternatively, reduction of the powder may be so enabled by the energy beam so that a metallic phase product is formed at the irradiated locations. Particular benefits of the invention include the densification of the material of the part as a result of the reaction, and the ability to form high temperature materials by way of a relatively low temperature process.

The economies associated with conventional part production methods are generally, related directly to the quantity of parts to be produced and the desired material characteristics of the finished parts. For example, large scale manufacture casting and extrusion techniques are often cost effective, but these production methods are generally unacceptable for small quantities--i.e. replacement parts or prototype production. Many such conventional part production methods require expensive part specific tooling. Even powder metallurgy requires a die for shaping the powder, making powder metallurgy unattractive as a method for producing a small number of parts.
Where only a small number of parts are desired, conventional production methods involving a subtractive machining method are usually used to produce the desired part. In such subtractive methods, material is cut away from a starting block of material to produce a more complex shape. Examples of subtractive machine tool methods include: milling, drilling, grinding, lathe cutting, flame cutting, electric discharge machine, etc. While such conventional machine tool subtractive methods are usually effective in producing the desired part, they are deficient in many respects.
First, such conventional machine tool subtractive methods produce a large amount of waste material for disposal. Further, such machine tool methods usually involve a large initial expense for setting up the proper machining protocol and tools. As such, the set-up time is not only expensive, but relies a great deal on human judgment and expertise. These problems are, of course, exacerbated when only a small number of parts are to be produced.
Another difficulty associated with such conventional machining techniques involves tool wear - which not only involves the cost of replacement, but also reduces machining accuracy as the tool wears. Another limit on the accuracy and tolerance of any part produced by conventional machining techniques is the tolerance limits inherent in the particular machine tool. For example, in a conventional milling machine or lathe, the lead screws and ways are manufactured to a certain tolerance, which limits the tolerances obtainable in manufacturing a part on the machine tool. Of course, the tolerances attainable are reduced with age of the machine tool.
The final difficulty associated with such conventional machine tool subtractive processes is the difficulty or impossibility of making many part configurations. That is, conventional machining methods are usually best suited for producing symmetrical parts and parts where only the exterior part is machined. However, where a desired part is unusual in shape or has internal features, the machining becomes more difficult and quite often, the part must be divided into segments for production. In many cases, a particular part configuration is not possible because of the limitations imposed upon the tool placement on the part. Thus, the size and configuration of the cutting tool do not permit access of the tool to produce the desired configuration.
There are other machining processes which are additive, for example, plating, cladding, and some welding processes are additive in that material is added to a starting substrate. In recent years, other additive-type machining methods have been developed which use a laser beam to coat or deposit material on a starting article. Examples include U.S. Pat. Nos. 4,117,302; 4,474,861; 4,300,474; and 4,323,756. These recent uses of lasers have been primarily limited to adding a coating to a previously machined article. Often such laser coating methods have been employed to achieve certain metallurgic properties obtainable only by such coating methods. Typically, in such laser coating methods the starting article is rotated and the laser directed at a fixed location with the coating material sprayed onto the article so that the laser will melt the coating onto the article.
The above-referenced U.S. Pat. Nos. 4,944,817 and 4,863,538, as well as U.S. Pat. No. 4,938,816, issued Jul. 3, 1990, and PCT publication WO 88/02677, published Apr. 21, 1988, all of which are incorporated herein by this reference, describe a method of producing complex parts directly from a CAD data base which is not subject to the above-described limitations of the various subtractive and additive methods; this new method will be referred to hereinbelow as the "selective beam sintering" or "selective laser sintering" processes. The selective laser sintering process is particularly advantageous in forming prototypes for parts which may subsequently be mass produced, for example by investment casting, or by the use of tooling.
To provide a part having the necessary strength, stability, and integrity to meet the mechanical and temperature stress requirements of its end use, it is of course desirable to form parts of high melting point materials. Accordingly, the formation of ceramic parts by selective beam sintering is desirable. However, many ceramic powders have sintering or melting temperatures which are sufficiently high that selective sintering or melting by a directed energy beam, such as a laser, while still maintaining high dimensional resolution and close tolerances, is not easily achievable at this time.
By way of further background, the above-referenced copending applications Ser. No. 624,419 filed Dec. 7, 1990, and Ser. No. 657,151 filed Feb. 19, 1991, each describe methods and material systems for utilizing composite powders to form high temperature materials by way of the selective beam sintering processes, such high temperature materials including intermetallics and ceramics. The materials formed according to these methods and systems include those with higher melting points than in the constituent powders, thus allowing relatively low power lasers to form high temperature materials.
It is an object of this invention to provide a method of producing a part by the application of energy to selected portions of a powder layer, where the part is defined by the reaction of the powder material with gases in the atmosphere.
It is a further object of this invention to provide such a method where the shape and dimensions of the part are defined by such a method performed in layerwise fashion.
It is a further object of this invention to provide such a method where the part is formed of a composite material.
It is a further object of this invention to provide such a method where the powder includes multiple materials, so that the part is formed of a composite material.
It is a further object of this invention to provide such a method wherein the part being formed densifies as a result of the reaction.
It is a further object of this invention to provide such a method where the part formed has a higher melting point than that of the constituent powder.
Other objects and advantages of the invention will be apparent to those of ordinary skill in the art having reference to the following specification, together with the drawings.

Method of producing parts by selective beam interaction of powder with gas phase reactant

Board of Regents, The University of Texas System


Two implementations of the inverse wavelet transform for use in an image decompression system do not waste computation power on the zero-valued values inserted into the data stream during an upsampling process. The implementation optimized for low-bandwidth applications toggles between even and odd modes each clock cycle. In even/odd mode, the transformed values are multiplied by the even/odd filter coefficients. The implementation optimized for high-bandwidth applications multiplies the transformed values by the even and odd filter coefficients seperately in two sets of multipliers and outputs two different results each clock cycle.

Recently, there has been growing demand for multimedia computing and communication. This growing demand has motivated searches for better bandwidth management techniques, including newer and more efficient compression methods.
Today's mainstream compression methods, such as JPEG for still images and MPEG for video, use the Discrete Cosine Transform (DCT). The sinusoidal basis functions of the DCT have infinite support and so each sinusoidal basis function provides perfect frequency resolution but no spatial resolution. At the other extreme, impulse basis functions have infinitesimal support, so each impulse basis function provides perfect spatial resolution but no frequency resolution. However, neither sinusoidal nor impulse basis functions are very well suited for the purposes of image and video compression. Better suited are basis functions which can trade-off between frequency and spatial resolution.
The wavelet basis functions of a wavelet transform are such basis functions in that each wavelet basis function has finite support of a different width. The wider wavelets examine larger regions of the signal and resolve low frequency details accurately, while the narrower wavelets examine a small region of the signal and resolve spatial details accurately. Wavelet-based compression has the potential for better compression ratios and less complexity than sinusoidal-based compression. The potential for wavelet-based compression is illustrated by FIGS. 19, 20, and 21. FIG. 19 is an original 8 bits per pixel 512.times.512 image of "Lena." FIG. 20 is a reconstructed image of Lena after JPEG compression at a compression ratio of approximately 40. FIG. 21 is a reconstructed image of Lena after wavelet compression at a compression ratio of approximately 40 using a preferred embodiment of the present invention. FIG. 21 appears less "blocky" than FIG. 20 because of the varying widths of the wavelet basis functions.
For a practical discussion of wavelet-based compression, see, for example, "Compressing Still and Moving Images with Wavelets," by Michael, L. Hilton, Bjorn D. Jawerth, and Ayan Sengupta, in Multimedia Systems, volume 2, number 3 (1994). Another useful article is "Vector Quantization," by Robert M. Gray, in IEEE ASSP Magazine, April 1984. Both the above articles are herein incorporated by reference in their entirety.
Prior systems and methods for inverse wavelet filtering use conventional filters. A conventional filter does not efficiently compute the inverse wavelet transform of an image because it does not take advantage of the fact that its input is an upsampled stream of data.

System and method for implementation of inverse wavelet transforms


A terminal portion (11) of a spark plug (10) and a connecting terminal (22) of an ignition coil (20) are connected through a coil spring (30) serving as a conductive member which in turn is covered with an insulating member (40) having a cap (41), a sleeve (47) and a bushing (48) and extending from the terminal portion (11) to a high-tension tower (21). A first air vent hole (44) is defined by an upper surface of a collar portion (42) of the cap (41) and a bottom surface of an ignition coil body (23) in intimate contact with the upper surface, and a plurality of reservoir spaces (45) having a greater volume than the first air vent hole (44) are formed in circumferentially spaced apart relation along the first air vent hole (44). A second air vent hole (46) is formed in the cap (41) for communication between the first air vent hole (44) and the interior of a plug hole (H). This provides a structure for connecting the spark plug and the ignition coil which prevents water from entering the plug hole through the air vent holes when a cylinder head is subjected to high-pressure water.

1. Field of the Invention
The present invention relates to a structure for connecting an ignition coil and a spark plug for use in an internal combustion engine.
2. Description of the Background Art
Referring to FIGS. 6 and 7, a spark plug 51 mounted in the bottom of a plug hole H formed in a cylinder head C and an ignition coil 52 fixed on the cylinder head C are electrically connected in a manner to be described below.
A connecting terminal 53 projecting downwardly from the underside of the ignition coil 52 is electrically connected to a terminal 54 of the spark plug 51 which projects upwardly in the cylinder head C through a conductive member 55 such as a single spring, a metal round bar, and a metal cylinder. An insulating member 56 covers an outer periphery of the conductive member 55 to extend from the connecting terminal 53 to the terminal 54.
There are two types of insulating members 56. One type is an insulating member comprised of three members: a cap for covering the range from the connecting terminal 53 to the conductive member 55, a bushing for covering the range from the terminal 54 to the conductive member 55, and a sleeve for covering the conductive member 55 to extend from the cap to the bushing. The other type is an insulating member comprised of the cap, bushing and sleeve which are formed integrally. In either case, the cap or a portion corresponding to the cap is fitted in an upper portion of the plug hole C in such a manner that an upper surface thereof is in intimate contact with the underside of the ignition coil 52 and an outer periphery thereof is in intimate contact with an inner peripheral surface of the plug hole H.
A first air vent hole 57 is formed in the contact portion between the upper surface of the cap or the portion corresponding to the cap and the bottom surface of the ignition coil 52 and extends from the outer edge of the contact portion. A second air vent hole 58 for communication between the first air vent hole 57 and the interior of the plug hole H is formed in the cap or the portion corresponding to the cap.
When the air in the plug hole H is heated to expand, the expanded amount of air may be escaped through the first and second air vent holes 57 and 58, preventing changes in pressure in the plug hole H.
The above stated connecting structure presents no significant problem when the cylinder head C is exposed to a small amount of water. However, when the cylinder head C is subjected to high-pressure water, for example, during car washing, water might enter the plug hole H through the first and second air vent holes 57 and 58.

Structure for connecting spark plug and ignition coil for internal combustion


A system for an asset monitor includes a reader, a tag, and a router. The router actively transmits a location identification to the tag in a coverage area by using a radio frequency (RF). The tag is mounted on an article (or a user). The tag directly sends a signal to the reader or indirectly forwards to the reader via the router when the location identification of the tag is different from a current location identification or the location identification is repeatedly received up to a preset value. The sent signal includes a location identification and a current location identification that are received by the reader to determine the location of the article.

1. Field of the Invention
The present invention relates to an RFID monitor system, and more particularly to an asset monitor system.
2. Description of the Prior Art
Generally speaking, the radio frequency identification (RFID) applied to a zone location are divided into two groups. The first one is RFID reader location and the second one is IR (infrared rays) location.
In the RFID reader location, a plurality of RFID readers are installed in monitored spaces and radiated power of the RFID readers are set to adjust the coverage area. The RFID readers are connected to a rear terminal by a network, and the RFID readers receive a signal sent from a remote tag to acquire a location of the tag. However, the RFID reader location is unfavorable to apply in an accurate small-area location because of higher cost for using a large number of RFID readers.
In the IR location, a plurality of IR transmitters are installed in monitored spaces. The IR transmitter sends a location identification to an electronic tag with an IR receiver, and the electronic tag transmits a signal included the location identification to a reader. However, the location identification easily disappears when the IR receiver of the tag is covered by clothes or other objects.
ZigBee is a wireless technology developed as an open global standard to address the unique needs of low-cost, low-power, wireless sensor networks. However, ZigBee has two main disadvantages: first one is a large number of data are received by readers to increase electricity consumption of electronic tags. The second one is a plurality of routers are used to pass through responded messages to increase difficulty of certifying the actual location.

System and method for RFID asset monitor


A microfluidic chip assembly having a plurality of microfluidic flow channels is provided. Each channel has a switching region. The microfluidic chip may further include at least one surface acoustic wave generator configured to generate a pressure pulse in the switching regions of the channels to selectively deflect particles in the flow. Attenuation elements and/or channel configurations may be used to prevent acoustic signals from interfering with neighboring switching regions. Alternatively, a microfluidic particle processing system may include a microfluidic chip assembly, a particle processing instrument, and a coupling element. The surface acoustic wave generator may be provided on the particle processing instrument. The microfluidic chip assembly may be configured for operative engagement, via the coupling element, with the particle processing instrument. The coupling element may transmit acoustic energy from the surface acoustic wave generator to the switching regions and/or to focusing regions of the flow channels.

Particle separation is of great interest to many biological and biomedical applications. Hydrodynamic and bulk acoustic-based techniques have been used to focus sample core flows within sheath fluid. With respect to hydrodynamic focusing, conventional devices that have been employed to implement sheath flow have relatively complex designs and are relatively difficult to fabricate. Bulk acoustic wave (BAW) techniques, which may provide focusing of particles based on size and density in microfluidic chips, typically require that the microfluidic channels be formed of a material having excellent acoustic reflection properties (such as silicon and glass). Unfortunately, some less expensive, more commonly used, polymeric materials generally do not have such excellent acoustic reflection properties. Moreover, BAW transducers may be bulky.
More recently, surface acoustic wave (SA techniques have been developed to focus, manipulate and/or separate particles flowing within microfluidic channels. A SAW preferentially travels along the surface of a material rather than through the bulk of the material (generally, the amplitude of the acoustic wave decays exponentially transverse to the surface of the material). "Leakage" of SAWs into the fluid within the microfluidic channel results in pressure gradients in the fluid and/or streaming of the fluid. Acoustic particle manipulation may be applied to virtually any type of particle as it does not depend on the charge, polarity or labeling of the particles.
In general, surface acoustic waves propagate along a stress-free plane surface of an elastic solid substrate. Surface acoustic waves have an essentially exponential decay of amplitude into the substrate and therefore most of the displacement of the substrate occurs within about one wavelength of the surface.
A surface acoustic wave may be generated using an inter-digitated transducer (IDT) supported by a piezoelectric substrate. The transducer may be formed of two comb-shaped electrodes having interlocking teeth or fingers. An IDT converts periodically-varying electrical signals into mechanical vibrations or acoustic waves able to travel along the surface of a material. The frequency of the SAW generated by an IDT may be controlled by controlling the periodic spacing of the teeth or fingers of the IDT. As a non-limiting example, a piezoelectric substrate may be formed of a ferroelectric material such as lithium niobate.
SAW techniques may involve standing surface acoustic waves (SSAW) or travelling or streaming surface acoustic waves (TSAW). For example, a SSAW may be generated using a pair of IDTs that may be placed on the substrate on opposite sides of the microfluidic channel, with a particle focusing region being defined between the SSAW generators, The SSAW induces standing pressure waves, i.e., pressure forces or gradients associated with nodes or anti-nodes, within the fluid in the particle focusing region, and these gradients may be used to manipulate suspended particles.
U.S. Pat. No. 8,573,060 to Huang et al. discloses a microfluidic device wherein particles associated with a sample flowing within a channel are concentrated within a particle focus region of the channel by the effects of the SSAW. Referring to prior art FIG. 1 (taken from U.S. Pat. No. 8,573,060) a standing surface acoustic wave focusing device is schematically illustrated as a pair of IDTs deposited on a piezoelectric substrate and a microfluidic channel formed in a layer bonded to the substrate and positioned between the two IDTs. The pair of IDTs 18, 20 generates interfering surface acoustic waves, thereby creating a standing surface acoustic wave with pressure nodes (or anti-nodes) within the channel 10. Particles 12 suspended within a fluid medium 13 flowing within the channel 10 are focused to a narrow particle stream 14 at a pressure node located at the center of the channel as they flow through the particle focusing region. The lower portion of FIG. 1 schematically illustrates an enlarged cross section of the microfluidic channel to show how the standing surface acoustic wave pressure field inside the channel induces particles to collect at the pressure node. U.S. Pat. No. 8,573,060, issued Nov. 5, 2013 (U.S. Ser. No. 12/631,059) is incorporated by reference herein in its entirety.
US Patent Publication No. 2013/0213488 to Weitz et al. discloses a microfluidic device for sorting droplets or particles using TSAW. As with U.S. Pat. No. 8,573,060, US 2013/0213488 discloses that the surface acoustic waves may be created using a surface acoustic wave generator such as an IDT coupled to a material such as a piezoelectric substrate. However, in contrast to U.S. Pat. No. 8,573,060, US 2013/0213488 does not use the IDT to create interfering surface acoustic waves and a concomitant standing surface acoustic wave (SSAW), but rather to create traveling surface acoustic waves (TSAW). Referring to prior art FIG. 2 (taken from US 201310213488), the TSAW propagates on the surface of a piezoelectric substrate (1) and leaks into the fluid within the microfluidic channel (4) as a longitudinal wave. This leaked longitudinal wave causes acoustic streaming as a result of the compressibility of the bulk fluid. Particles located within the plug or droplet of acoustically streamed bulk fluid may be moved with the droplet. By controlling the applied voltage to the DT, streaming of the fluid within the microfluidic channel may be generated and used to individually direct or sort selected droplets within the microfluidic channel to particular channels or regions. As such, the traveling surface acoustic wave may act as a particle switch on a particle-by-particle basis. In FIG. 2, the SAW is shown additionally coupled to the microfluidic channel (4) via a water/glass coupling region. The SAW traveling along the piezoelectric substrate (1) is refracted as a longitudinal wave into a layer of water (2) and is subsequently refracted as a transverse wave into a layer of glass (3). At the top of the glass layer (3), the wave is refracted again, entering the water-filled channel (4) and causing acoustic streaming as indicated. US Patent Publication No. 2013/0213488 (U.S. Ser. No. 13/818,146, filed Aug. 23, 2011) is incorporated by reference herein in its entirety.
US Patent Publication No. 2014/0008307 to Guldiken et al. discloses a two-stage microfluidic device for focusing and separating particles flowing within a channel using standing surface acoustic waves. The two-stage microfluidic device has both a particle focusing stage and a particle separating stage, which is located downstream of the particle focusing stage. The particle focusing stage includes a pair of IDTs that generate a standing surface acoustic wave for focusing particles to a single pressure node (or anti-node) in the center of the channel, similar to the SSAW of U.S. Pat. No. 8,573,060. The particle separating stage includes a second pair of IDTs that also generates a standing surface acoustic wave. However, in this particle separating stage, the SSAW forms a periodic distribution of a plurality of pressure nodes and anti-nodes within the channel, thereby dividing the particles as they flow along a length of the channel into a plurality of particle streams aligned with the plurality of nodes or anti-nodes. The particles may be segregated based on their volume, density, compressibility or other acoustic contrast factor. Downstream of the particle separating stage, the various segregated streams of particles may flow into multiple collection outlets that are aligned with the streams. Guldiken also describes a method for fabricating and integrating the two-stage microfluidic device for focusing and separating particles flowing within a channel using IDTs to generate standing surface acoustic waves. US Patent Publication No. 2014/0008307 (U.S. Ser. No. 14/007,483, filed Mar. 30, 2012) is incorporated by reference herein in its entirety.
IDTs that are tunable have also been developed. US Patent Publication No. 2013/0192958 to Ding et al. discloses variable frequency or "chirp" IDTs having a gradient in their finger period, allowing them to resonate over a range of frequencies when the input frequency is varied. By varying the input frequency of a single pair of chirp IDTs, the pressure nodes may be generated at different locations across a microfluidic channel, such that depending upon the selected input frequency, particles flowing within the channel may be directed to a specific collection channel. In another embodiment, orthogonally positioned pairs of chirp IDTs may create SSAWs having pressure nodes (or anti-nodes), the location of which can be precisely adjusted by varying the input frequency to the IDTs. US Patent Publication No. 2013/0192958 (U.S. Ser. No. 13/755,865, filed Jan. 31, 2013) is incorporated by reference herein in its entirety.
US Patent Publication No. 2014/0033808 to Ding et al. discloses a pair of IDTs for creating a SSAW having a pressure node (or anti-node) that is obliquely aligned with the longitudinal axis of the flow channel. Thus, certain particles traveling down the channel will be repositioned within the channel due to the acoustic radiation forces created by the obliquely aligned pressure nodes (or anti-nodes). US Patent Publication No. 2014/0033808 (U.S. Ser. No. 13/995,709, filed Jul. 31, 2013) is incorporated by reference herein in its entirety.
PCT Publication WO 2014/004630 to Weitz et al. discloses using a pair of IDTs to create a "traveling" or "shifting" standing surface acoustic wave (TSSAW). U.S. Pat. No. 8,573,060, discussed above, employs a pair of IDTs, each generating a surface acoustic wave having the same frequency as the other, such that the interference of these surface acoustic waves creates stationary pressure nodes or antinodes. WO 2014/004630 discloses employing a pair of IDTs wherein each generates a surface acoustic wave having a frequency that slightly differs from the other. This slight mismatch in frequency creates standing waves having pressure nodes that slowly shift or move toward one of the pair of IDTs. PCT Publication WO 2014/004630 (Application No. PCT/US2013/047829 filed Jun. 26, 2013) is incorporated by reference herein in its entirety.
None of the above-cited documents disclose the use of SAW techniques for multiple channels provided on a single chip.

Microfluidic device and system using acoustic manipulation


A system (10) is disclosed for testing a watchdog timer (22). The watchdog timer is associated with a system (14) which is controlled by a control program executed by a programmed processor (20) and which is monitored by a supervisory system (18) in which the watchdog timer generates an interruption signal (NMI) which interrupts the control program when the watchdog timer does not generate a reset signal within a time window measured from a last reset signal. The supervisory system contains a circuit coupled to the watchdog timer for initiating testing of the watchdog timer. The watchdog timer contains a circuit for disabling the generation of the interruption signal during testing of the watchdog timer. Furthermore, the watchdog timer contains a circuit for shutting down the system which is controlled by the control program when the control program does not resume normal operation in response to an interruption signal. The watchdog timer has a circuit for disabling the circuit for shutting down the system which is controlled by the control program during testing of the watchdog timer.

Watchdog timers are well known for detecting failures in processors. A watchdog timer is particularly useful for protecting processors against failures caused by noise induced software malfunctions which can cause control or protection malfunctions. A typical watchdog timer monitors software functions by producing a non-maskable interrupt when a reset pulse is not produced within a predetermined time interval. The reset pulse is typically produced cyclically by a monostable multivibrator during execution of the software by the processor when a fault condition does not exist. During normal operation, the watchdog timer is cleared by a reset signal before the watchdog timer times out. U.S. Pat. Nos. 3,795,800, 3,909,795, 3,919,533, 4,405,982, 4,477,870 and 4,538,273 disclose examples of timers utilized for monitoring the operation of processors. Patent No. 3,919,533 discloses a watchdog timer which periodically provides a code to a decoder network cyclically during an interval having a period shorter than a predetermined time interval of the timing network so that a fault is continuously inhibited as long as the code is continuously supplied with the desired periodicity. None of the aforementioned systems disclose testing procedures for watchdog timers.
In applications where critical functions are performed under the control of a programmed processor, such as aircraft power generating systems or control mechanisms for wing actuators, it is of importance to insure that the watchdog timer itself is operational. For example, electromagnetic interference (EMI) noise could produce a false reset pulse which would mask the presence of a malfunction in the watchdog timer. Furthermore, a line for coupling reset pulses to the processor could fail in a high state or the processor could be in a loop which is a fault condition which causes reset pulses to be sent continually within the cyclical time interval of the watchdog timer which masks the presence of a fault condition.


A method and system are provided for transmission of m information signal combinations over a known transmission medium at a high rate of speed without crosstalk between data transferred through the transmission medium. The technique employed is to convert each of the m information signal combinations to a unique line signal corresponding to one of n intrinsic orthogonal modes of the defined transmission medium through which the information is to be transmitted (wherein m>n). The encoded line signals, propagated via the orthogonal modes, are received and decoded at a remote location along the transmission medium to restore the original information data. The problem of assigning m unique line signals to each of the m possible information signal combinations is addressed by amplitude modulation of the transmission medium's n intrinsic orthogonal modes.

A well documented and inherent difficulty in the parallel transmission of analog/digital information over a transmission medium, such as a plurality of parallel transmission lines, is signal crosstalk resulting from capacitive and inductive coupling within the transmission medium. The error rate due to crosstalk signal degradation typically increases with increasing speed of data transmission. This is because higher transmission speeds involve a greater number of possible values which make it increasingly difficult to distinguish between signals in the presence of an electrical impairment. The open literature contains a vast number of references which in general attempt to address the problem of signal noise on transmission lines, and in particular, to minimize crosstalk between information transmitted in parallel through a transmission medium having defined characteristics.
One interesting approach is discussed by T. H. Nguyen and T. R. Scott in an IBM Technical Disclosure Bulletin entitled "Propagation Over Multiple Parallel Transmission Lines Via Modes,+ Vol. 32, No. 11, April, 1990. As discussed therein, it is known that electromagnetic waves propagating over two conductors and a ground line have two orthogonal modes referred to as the "even mode" and the "odd mode." In general, n conductors and a ground line have n such orthogonal modes. Because of its orthogonal properties, each mode propagates independent of all other modes. The resolution of line voltages into orthogonal modes is analogous to the concept of resolving a pulse waveform into its orthogonal Fourier components. Just as the Fourier components can be studied separately because they are orthogonal, and hence independent of each other, so the intrinsic orthogonal modes of a plurality of transmission lines can be studied separately since they are also independent of each other.
The above-referenced IBM Technical Disclosure Bulletin describes the simplicity of orthogonal mode determination for those transmission lines having 2, 4, 8, . . . , 2.sup.n conductors symmetrically arranged on a cylindrical surface with respect to a coaxial ground conductor. The calculation of orthogonal modes for certain such transmission line configurations is presented. Although the mathematical groundwork for transmission of intrinsic orthogonal modes over a plurality of parallel transmission lines is discussed in this Technical Disclosure Bulletin, a practical implementation of the concept is lacking. The difficultly encountered is that the propagation of binary signals (for example) via modes is often not possible with only digital (i.e., on/off) signals since the number of modes is equal to the number of conductors (which can be doubled by using plus/minus designations), but the number of binary combinations is exponential, i.e., two raised to the number of conductors n. Therefore, a need exists in the art for a practical approach (such as described herein) to allow the encoding of, for example, each possible binary signal combination as a unique orthogonal mode signal for transmission through a transmission medium having defined characteristics.

Modal propagation of information through a defined transmission medium

International Business Machines Corporation


A method of forming an O.sub.3 -TEOS oxide film, including the steps of supplying a reactant gas into a plasma CVD apparatus in which a waver is stored and applying a plasma generating voltage to form a plasma silicon oxide film on the wafer; performing a hydrophobic process by stopping supply of the reactant gas into the plasma CVD apparatus and application of the plasma generating voltage, introducing TEOS gas into the plasma CVD apparatus to make an atmosphere of the TEOS gas in a process chamber of the plasma CVD apparatus, and allowing the plasma silicon oxide film on the wafer to react with the TEOS gas in the process chamber; and allowing O.sub.3 to react with TEOS gas to form an O.sub.3 -TEOS oxide film on the plasma silicon oxide film subjected to the hydrophobic process. According to this method, the substrate dependency of the O.sub.3 -TEOS oxide film can be improved without the need for any additional apparatus for hydrophobic treatment of the plasma silicon oxide film and an increase in number of process steps.

1. Field of the Invention
The present invention relates to a method of forming an O.sub.3 -TEOS oxide film, and more particularly to a method of forming an O.sub.3 -TEOS oxide film with improved substrate dependency.
2. Description of the Related Art
An O.sub.3 -TEOS oxide film formed by oxidation of TEOS (Tetraethylorthosilicate, Si(OC.sub.2 H.sub.5).sub.4) with O.sub.3 exhibits various superior film characteristics in planarization, step coverage, electrical insulation, etc. It has also received attention as an oxide film that can be formed by low-temperature growth at 400.degree. C. or less.
However, in forming an SiO.sub.2 film by oxidation of TEOS with O.sub.3, the film growth rate is extremely dependent on the property of a substrate layer formed on a substrate. That is to say, the so-called substrate dependency is remarkable. More specifically, the film growth rate of an SiO.sub.2 film to be formed by oxidation of TEOS with O.sub.3 on a hydrophobic substrate film such as an Si film, A1 film, or AP-CVD film (a substrate film incorporating a small quantity of H.sub.2 O) is different from that on a hydrophilic substrate film such as an SiO.sub.2 film formed by thermal oxidation (a substrate film incorporating a large quantity of H.sub.2 O). That is, the film thickness of the SiO.sub.2 film on the hydrophobic substrate film is small, whereas the film thickness of the SiO.sub.2 film on the hydrophilic substrate film is large. Further, the film growth rate depends also on the condition of end groups of components constituting the substrate film, thus rendering it unstable.
As described above, the SiO.sub.2 film formed by oxidation of TEOS with O.sub.3 is non-uniform in film quality and film thickness because of its substrate dependency, thus reducing the subsequent process margin and thus reducing product yield. To cope with this problem, it has been attempted to improve the substrate dependency of the SiO.sub.2 film produced using O.sub.3 -TEOS, by using HMDS (Hexamethyldisilazane, (Si(CH.sub.3).sub.3).sub.2 NH) and ethanol (C.sub.2 H.sub.5 OH) to carry out a treatment of the surface of a hydrophilic substrate film in a manner which renders it hydrophobic.
However, this conventional method requires additional apparatus for the hydrophobic conversion treatment of the substrate film, causing an increase in installation costs and in the number of process steps. Thus, there is a problem of increased operating costs inclusive of labor costs as well as costs involved with the transfer of the substrate between apparatuses.


A structure is provided with a self-aligned resist layer on an insulator surface and non-lithographic method of fabricating the same. The non-lithographic method includes applying a resist on a structure comprising at least one of interconnects formed in an insulator material. The method further comprises exposing the resist to energy and developing the resist to expose surfaces of the interconnects. The method further comprises depositing metal cap material on the exposed surfaces of the interconnects.

Electromigration is the transport of material caused by the gradual movement of ions in a conductor due to the momentum transfer between conducting electrons and diffusing metal atoms. The effect of electromigration is an important consideration to take into account in applications where high direct current densities are used, such as in microelectronics and related structures. In fact, electromigration is known to decrease the reliability of integrated circuits (ICs) and hence lead to a malfunction of the circuit. In the worst case, for example, electromigration leads to the eventual loss of one or more connections and intermittent failure of the entire circuit.
The effect of electromigration becomes an increasing concern as the size of the IC decreases. That is, as the structure size in ICs decreases, the practical significance of this effect increases. Thus, with increasing miniaturization the probability of failure due to electromigration increases in VLSI and ULSI circuits because both the power density and the current density increase.
In advanced semiconductor manufacturing processes, copper is used as the interconnect material. Basically, copper is preferred for its superior conductivity and electromigration resistance, for example, as compared to the prior Al(Cu) alloy interconnects. However, even copper interconnects have been facing the limitation of the electromigration lifetime or the upper limitation of the current density because of electromigration failure. To solve this problem, though, capping copper interconnects with CoWP or CoWB has been widely investigated. It has been found that the copper interconnects can have higher electromigration resistance when capped with CoWP or CoWB. This is because the top surface of the copper interconnects, which heretofore was capped with a dielectric barrier such as SiN or SiCN, and which resulted in this top surface being the fast diffusion path for copper electromigration, is effectively shut down for fast copper diffusivity and electromigration by a metal cap.
However, the CoWP or CoWB and even other metal capping materials can pose issues to the IC. For example, during the deposition of the CoWP or CoWB or other metal capping materials, residual metal can be deposited on the surface of the dielectric insulator material between the copper interconnects. Since the distance between the neighboring copper lines is becoming smaller as the device shrinks, the potential for shorting between the interconnects is becoming even more serious, especially if residual metal remains on the dielectric insulator material between the interconnects.
Accordingly, there exists a need in the art to overcome the deficiencies and limitations described hereinabove.

Structure with self aligned resist layer on an insulating surface and method of making same

International Business Machines Corporation


A pressure sprayer is pressurized automatically with movement of the sprayer and maintains adequate pressure during non-movement to allow the ejection of an amount of liquid before needing re-pressurization. The pressure sprayer includes wheels that allow the pressure sprayer to be mobile. A cam is attached to the axle of the wheels which rotates with the rotation of the axle/wheels. A pressure pump is associated with the cam such that movement of the cam causes the pressure pump to pump liquid from a holding tank to an accumulator or directly to a spray wand in communication with the pump. The liquid may be sprayed (ejected) from the accumulator during both movement (pumping) and non-movement (no pumping) of the sprayer, while the liquid may be directly sprayed from the holding tank only during movement (pumping) thereof. Thus, as the wheels rotate due to moving the pressure sprayer, the cam causes movement of the pressure pump to fill the accumulator with the liquid under pressure. The pressure pump is adapted to obtain liquid from the holding tank and provide that liquid to the pressure accumulator. A relief valve is provided to relieve the buildup of pressure during movement of the wheels when no spraying is taking place.

The present invention relates to pressure sprayers and, more particularly, to portable, self-pumping pressure sprayers.
Pressure sprayers are well known in the art, having been developed many years ago. They essentially consist of a tank that is adapted to hold a liquid and become pressurized with air. The tank becomes pressurized via a pump. When a spray head and/or wand that is attached to the pressurized tank is opened, the liquid within the tank is ejected from the spray head/wand by the pressure in the tank. Eventually, the pressure within the tank decreases with the ejection of liquid therefrom. When the pressure against the liquid within the tank drops to a particular value, the liquid will not be ejected from the tank due to lack of pressure. Therefore, in order to maintain (have) adequate pressure within the tank in order to eject the liquid therefrom, the pressure must be periodically increased. This is accomplished by a manually actuated pump associated with the pressure sprayer.
Such pressure tanks may be used for spraying insecticides, pesticides, biocides, and herbicides, as well as paints, stains, water, and virtually any other non-viscous liquid. Small, portable (i.e. hand-carried) pressure tanks of one to five gallons in size have been used by the home and business industry. Early pressurized tanks were metal canisters with a manually actuated pump. When these metal tanks were filled with a liquid, and manually pumped to the appropriate pressure, they were quite heavy and cumbersome to carry. Currently, most pressure sprayers are formed from a suitable plastic. While plastic tanks are lighter than metal tanks when filled with a liquid and pumped to an adequate pressure, they are still cumbersome and somewhat heavy.
Wheels were added to larger pressure sprayers in order to alleviate the above problems by allowing a user to pull or push the pressure sprayer to its intended location rather than carry the pressure sprayer. These portable pressure sprayers were, however, still pressurized by manually actuated pumps. Thus, although these mobile pressure sprayers obviated the need to carry the heavy pressure sprayers, they were still pressurized by manual pumps.
Still another type of wheeled pressure sprayer in existence includes a pump which is actuated by rotation of the wheels of the sprayer. Upon actuation, the pump generates pressure which causes fluid to be sprayed out of the tank of the sprayer. However, this type of sprayer does not store pressure for spraying when the sprayer is not being moved (i.e. when the wheels are not being rotated). In other words, when movement of the sprayer is stopped so that the wheels are no longer rotating, the sprayer stops pumping fluid from the tank of the sprayer to the environment (e.g. onto a lawn).
What is needed is a portable pressure sprayer that develops its own pressure for ejecting a liquid and stores such pressure for later use by the sprayer even when the wheels of the sprayer are no longer being rotated.
What is further needed is a portable pressure sprayer that develops it own pressure for ejecting a liquid wherein adequate ejection pressure is maintained at least transiently.
What is still further needed is a portable pressure sprayer that develops pressure for ejecting a liquid through movement of the pressure sprayer, wherein adequate pressure is maintained for liquid ejection during periods of non-movement (i e. during periods when the wheels of the sprayer are no longer being rotated).
The present invention is a self-energizing pressure sprayer in which movement of the sprayer creates and maintains adequate pressure to expel an amount of liquid held therein during both movement and non-movement of the sprayer.
In one form thereof, a pressure sprayer having a holding tank includes a pressure pump that is adapted to pump a liquid from the holding tank to the accumulator during movement of the sprayer (i.e. rotation of the wheels of the sprayer).
In another form thereof, a pressure sprayer includes a holding tank, an accumulator and a pressure pump in communication with the holding tank and the accumulator. The pressure sprayer further includes wheels carried on an axle that rotates during pushing and/or pulling movement of the pressure sprayer. The pressure pump is associated with the axle such that rotation of the axle causes the pressure pump to pump fluid from the holding tank to the accumulator wherein the fluid is pressurized for ejection from the sprayer even at times when the wheels of the sprayer are being maintained stationary.
In yet another form thereof, a pressure pump of a pressure sprayer having a holding tank and an accumulator both in fluid communication with the pressure pump, is coupled to a cam assembly affixed on an axle for wheels of the pressure sprayer that drives the pressure pump during pushing and/or pulling movement of the pressure sprayer. The pump is in communication with a tank adapted to hold a liquid to be ejected and a pressure accumulator. During movement of the pressure sprayer, the cam assembly rotates to cause the pressure pump to reciprocate and thus pump (operate). Once the pressurized fluid has been depleted, movement of the pressure sprayer re-energizes (re-pressurizes) fluid for ejection.
According to still another embodiment of the present invention, there is provided a pressure sprayer which includes a tank for holding fluid, and an accumulator for storing fluid therein under pressure. The sprayer further includes a number of wheels for supporting the tank. Moreover, the sprayer includes a pump which advances fluid from the tank into the accumulator in response to rotation of the number of wheels. The pressure within the accumulator is increased when fluid is advanced into the accumulator by the pump.
Yet in accordance with another embodiment of the present invention, there is provided a pressure sprayer which includes an accumulator for storing fluid therein under pressure, and at least one wheel which rotates when the pressure sprayer is moved. The sprayer also includes a pump which advances fluid into the accumulator in response to rotation of the at least one wheel. An increased pressure is generated within the accumulator in response to fluid being advanced into the accumulator by the pump. Further, the increased pressure within the accumulator is maintained when the at least one wheel is stationary.
In accordance with still another embodiment of the present invention, there is provided a method of spraying fluid with a portable pressure sprayer having a tank, an accumulator, and a number of wheels. The method includes the steps of (i) moving the portable pressure sprayer so as to cause the number of wheels to rotate, (ii) advancing fluid from the tank into the accumulator in response to rotation of the number of wheels, (iii) generating an increased pressure within the accumulator in response to fluid being advanced into the accumulator, and (iv) maintaining the increased pressure within the accumulator after the moving step when the number of wheels are stationary.
In accordance with yet another embodiment of the present invention, there is provided a method of spraying fluid with a pressure sprayer having at least one wheel. The method includes the step of moving the portable pressure sprayer so as to cause the at least one wheel to rotate. The method also includes the step of generating an increased pressure within the sprayer in response to rotation of the at least one wheel. In addition, the method includes the step of maintaining the increased pressure within the sprayer after the generating step when the at least one wheel is stationary.

Portable self-energizing pressure sprayer


A semiconductor processing method of chemical mechanical polishing a predominately copper containing metal layer on a semiconductor substrate includes, a) providing a chemical mechanical polishing slurry comprising H.sub.2 O, a solid abrasive material, and a third component selected from the group consisting of HNO.sub.3, H.sub.2 SO.sub.4, and AgNO.sub.3 or mixtures thereof; and b) chemical mechanical polishing a predominately copper containing metal layer on a semiconductor substrate with the slurry. Such slurry also constitutes part of the invention. Such slurry may also contain an additional oxidant selected from the group consisting of H.sub.2 O.sub.2, HOCl, KOCl, KMgO.sub.4 and CH.sub.3 COOH or mixtures thereof to form a copper oxide passivating-type layer at the copper surface.

Metal films are utilized in semiconductor technology to wire together various components formed on a semiconductor wafer. Metal in semiconductor processing can also be used to function as gate electrodes in MOS structures, and as electrodes in thin film capacitors. Elemental aluminum and its alloys have been the traditional metals utilized. Advantages of aluminum include its low resistivity, superior adhesion to SiO.sub.2, ease of patterning, and high purity.
However, aluminum is not without drawbacks. First, the electrical contact of aluminum with silicon while adequate for large scale integration (LSI) level technology, has reached its limit in the very large scale integration (VLSI) era. Another drawback associated with aluminum is electromigration. This is a phenomenon that occurs in aluminum metal leads while the circuit is in operation, as opposed to a failure occurring during fabrication. Electromigration is caused by the diffusion of the aluminum in the electric field set up in the lead while the circuit is in operation. It is also enhanced by thermal gradients that arise in the lead from the heat generated by the flowing current. The metal thins and eventually separates completely, causing an opening in the circuit. Electromigration occurs over time and may not show up until a device has had many hours of operation. This problem is presently overcome by designing wide overlap regions at contacts, using a constant film thickness, or alloying aluminum with other materials such as copper or silicon.
Electromigration becomes more of a worry as the level of integration increases. The higher number of circuit components in VLSI, ultra large scale integration (ULSI) and beyond creates more current flow and generates more heat. Accordingly, as integrated circuit patterning schemes continue to miniaturize into to submicron dimensions, aluminum-based metallurgies will become increasingly marginal for handling the increased circuit speed and current density requirements.
Elemental copper or its alloys would be an attractive alternative as the primary conductor in VLSI and ULSI multilevel metallization systems. Copper has an even lower resistivity than aluminum, and significantly higher electromigration resistance. However, a primary problem with integrating copper metal into multilevel metallization systems is the difficulty of patterning the metal using etching techniques. For devices of submicron minimum feature size, wet etch techniques for copper patterning have not been acceptable due to, a) liquid surface tension, b) isotropic etch profile, and c) difficulty in over-etch control.
Several promising methods for producing patterned predominately Cu interconnects have been proposed, including selective electroless plating, selective chemical vapor depositing, and high temperature reactive ion etching. Lift off processing is also another alternative for patterning copper. One alternate technique of metal wiring of copper, and in accordance with an aspect of the invention, would comprise the patterning and etching of a trough and/or contact within a thick layer of insulating material such as SiO.sub.2. Thereafter, a thin layer of a barrier metal, such as Ti, TiW or TiN, is provided atop the insulating layer and within the trough and/or contact. Such functions as a diffusion barrier to prevent inter-diffusion between the metal to be subsequently deposited and silicon, and between such metal and oxide. After barrier metal deposition, a layer of metal is deposited to completely fill the trough. With troughs, which would be created prior to metal deposition, a desired metal pattern is defined such that a planar metal removing technique down to the surface of the insulating layer will leave remaining desired patterned electrically conductive metal lines.
One such planarizing technique is chemical mechanical polishing. However to date, chemical mechanical polishing of copper and it alloys has not been well understood or developed. Accordingly, a need remains for improved chemical mechanical polishing techniques and chemical mechanical polishing slurries for copper and its alloys.

Method of chemical mechanical polishing predominantly copper containing metal layers in semiconductor processing


An interceptive type electric probe for mapping the radial current density rofile of high energy and high current electron beams comprises an input sensor, an interface support connector and an output support connector. The entire structure of the electric probe is configured to closely approximate a coaxial transmission line of a predetermined impedance that is opened ended but yet shielded. The nature of the construction of the probe, in terms of materials and techniques, allows for survival thereof in high temperature and intense beam environments.

1. Field of Invention
The present invention relates to an apparatus for measuring the current density profile of intense electron beams, but more specifically it relates to an interceptive type electric probe for mapping the radial current density profile of high energy and high current electron beams.
2. Description of the Prior Art
The use of interceptive type probes for measuring the current density profile of electron beams is a common technique in accelerators producing low current, i.e., less than one ampere. Severe requirements are imposed on interceptive devices when current densities of the order of kiloamperes per square centimeter are encountered. In this case, space charge effects, large secondary electron production and probe heating are important considerations.
At the present time, measurement of the beam current density profile of an intense electron beam involves the monitoring of x-rays produced by probes fabricated from high atomic number wires inserted into the electron beam. This measurement system suffers the disadvantages of requiring extensive shielding and elaborate measurement equipment including an x-ray collimator, photomultiplier tube, a fast scintillator and a power supply powering the photomultiplier tube. Accordingly, this type of measurement system is necessarily bulky and expensive.
In practice, when a high energy electron beam hits a high atomic number wire probe, radiation is produced in the x-ray region of the electromagnetic spectrum. The amount of x-radiation produced depends on how much of the electron beam is intercepted by the probe. This measuring technique is very viable for mapping the radial current density profile of an intense electron beam; however, the technique suffers from a number of problems in addition to the previously mentioned ones. One problem is that the materials used to fabricate the probes heat excessively. Thus, from an engineering standpoint, probes made out of these materials have short lives and melt after a short period of time when used in the environment of the intense electron beams. Also, the monitoring system used has to be very sensitive, and, hence, will be sensitive to background x-radiation. This is the reason for the substantial amount of shielding. The shielding is made from lead and has to be configured to surround the monitoring system which makes it bulky, non-portable, very heavy, and, accordingly, very expensive.
Consequently, there is a need in the prior art to configure a probe for measuring the current density of an intense electron beam that is long lived, compact, easy to deploy, portable, and yet inexpensive and requires minimum support equipment for proper operation.
Another technique attempted in the prior art for measuring the beam current of intense electron beams was to make an electrical measurement rather than a measurement of x-rays. As far as it is known, no investigator has obtained an electrical signal, from which useful current density data could be elicited, from an intense electron beam using a bare wire type of interceptive probe. In actual practice, if a bare wire type probe is connected to a coaxial line and interfaced with an oscilloscope, and then inserted into an intense electron beam, a signal is produced which can be observed on the oscilloscope. This signal is very difficult to analyze. One reason is that when the probe is placed into an associated accelerator tube in which the intense electron beam is generated, and the electron beam is not intercepted, a zero response is desirable. On the other hand, when the probe is placed so as to intercept the electron beam an increase in response is desirable. However, with a bare wire the moment that the probe is placed inside the accelerator tube, a response is observed which indicates that there is field coupling between the bare wire probe and the the electron beam within the accelerator tube. The nature of the coupling has been found to be capacitive and, as aforementioned, is field produced.
There is yet another kind of problem that the bare wire electric probe encounters. When an intense electron beam travels through an accelerator tube, it produces a substantial amount of noise of the radio frequency (RF) type. The bare wire electric probe is susceptible to this RF noise which makes the extraction of any useful data from the probe signals about the electron beam very difficult. Thus, the bare wire probe suffers from the undesirable effects of being affected by both electric and magnetic fields which are external to the actual beam charge.
Consequently, there is a need in the prior art to eliminate the effects of field coupling, both electric and magnetic, between a probe for measuring the current density profile of intense electron beams and the electron beam being measured. There is an additional necessity to eliminate the effect of RF type noise which affects the accuracy of the measurements.
There is yet another problem with the bare metal wire probe. When the wire probe is used in the environment of an accelerator tube which pulses on and off very rapidly, there is a tendency for it to melt after continual use. Thus, this probe and the x-ray monitor system which also uses a metal wire probe, are limited in their useful lives.
Consequently, there is a need in the prior art to configure a probe for measuring the beam current density profile of intense electron beams, but yet be configured to have a long life time.
The representative prior art, as outlined hereinabove, include some advances in the measurement of the current density profiles of intense electron beams; however, insofar as can be determined, no prior art device incorporates all of the features and advantages of the present invention.

Coaxial probe for measuring the current density profile of intense electron beams

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


Systems and methods for demodulating a plurality of contiguous channels contained within a bandlimited portion of a radio-frequency (RF) input signal are provided. In an embodiment, the bandlimited portion of the RF input signal is down-converted to baseband. After down-conversion, the bandlimited portion overlaps at baseband with a mirror image of the bandlimited portion. The plurality of contiguous channels within the down-converted signal similarly overlap at baseband and subsequently occupy a bandwidth substantially equal to half that required before down-converting. Image rejection is performed in the digital domain to recover each of the plurality of overlapping channels.

Radio receivers, or tuners, are widely used in applications requiring the reception of electromagnetic energy. Applications can include broadcast receivers such as radio and television, set top boxes for cable television, cable modems, receivers in local area networks, test and measurement equipment, radar receivers, air traffic control receivers, and microwave communication links among others. Transmission of the electromagnetic energy may be over a transmission line or by electromagnetic waves.
Many applications require a receiver that can tune to multiple channels at the same time. For example, Picture in Picture (PiP) is a feature that is enabled by some television receivers and set top boxes. The PiP feature allows for one program to be fully displayed on a television screen, while one or more additional programs are displayed in inset windows at the same time.
Similarly, the Data Over Cable System Interface Specification (DOCSIS) 3.0 requires compliant cable modem receivers to have the ability to tune to multiple downstream channels at the same time. The term DOCSIS generally refers to a group of specifications published by CableLabs that define industry standards for cable headend and cable modem equipment. In part, DOCSIS sets forth requirements and objectives for various aspects of cable modem systems including operations support systems, management, data interfaces, as well as network layer, data link layer, and physical layer transport for data over cable systems. The most current version of the DOCSIS specification is DOCSIS 3.0.
In order to stay competitive with providers offering telecommunications services over fiber, and to better support bandwidth intensive applications, such as video-over-IP, DOCSIS 3.0 provides for a new feature referred to as channel bonding. This new feature calls for the bonding of any four channels in a contiguous 64 MHz bandwidth centered anywhere between 54 MHz and 1 GHz. In downstream transmissions, from a cable headend to a cable modem located at a subscriber premise, each downstream channel occupies a separate 6 MHz or 8 MHz frequency band and is capable of carrying a payload of approximately 38 Mbps (50 Mbps in Euro DOCSIS compliant systems). Channel bonding allows for a load to be distributed among multiple RF channels, allowing for a maximum throughput of n*38 Mbps (with n being the number of bonded channels).
Traditional cable modem receivers utilize a dual-conversion tuner architecture that is capable of down-converting a single channel. This dual conversion architecture typically utilizes two complex mixers and a surface acoustic wave (SAW) filter. The SAW filter is a mechanically resonant device that is typically fabricated on a ceramic substrate, and therefore cannot be integrated on-chip with the other tuner components. As such, the SAW filter remains a discrete component in many tuner designs, preventing the tuners from being fabricated on a single silicon substrate.
A simple approach to comply with the channel bonding standard specified in DOCSIS 3.0 is to use four instances of the traditional single channel tuner. Although this implementation can provide for the greatest flexibility in selecting multiple, non-contiguous channels in the downstream bandwidth, this solution requires a high component count, including four separate SAW filters, and a large amount of area in an IC implementation.
Alternatively, a single tuner architecture can be used that can down-convert four or more RF channels within any 64 MHz bandwidth. A single tuner architecture can provide for reductions in power consumption and silicon area. However, conventional implementations of this architecture typically require a SAW filter, as well as a large analog-to-digital converter (ADC) capable of handling bandwidths up to and in excess of 64 MHz.
Therefore, what is needed is new receiver and tuner architectures that provide flexibility in the selection and down-conversion of multiple RF channels, while at the same time eliminating the need for expensive, area-consuming components, such as SAW filters and high-bandwidth ADCs.
The present invention will be described with reference to the accompanying drawings. The drawing in which an element first appears is typically indicated by the leftmost digit(s) in the corresponding reference number.

Variable low IF receiver for multi-channel applications


A method of mounting a piezoelectric element with a substrate. First, a compliant material (206) is dispensed on at least one side of the substrate (102) and cured. Next, a first conductive adhesive (216) is applied on the other side of the substrate (106). Third, a piezoelectric element (102) is positioned over the substrate (106). And thereafter, a second compliant conductive adhesive (222) is selectively dispensed such that it contacts an upper portion of one side of the piezoelectric element (102) and the substrate (106).

Piezoelectric devices, such as piezoelectric quartz filters, piezoelectric quartz resonators and the like, typically include a piece of piezoelectric material mounted to a substrate. In quartz devices, the quartz element of necessity has thin metallic electrodes attached to it through which electrical signals are coupled into and out of the piezoelectric quartz material. Common problems with piezoelectric devices are adequately isolating the piezoelectric device from mechanical shock and dealing with thermal expansion coefficient mismatches between the piezoelectric material and the substrate material.
Quite often, the piezoelectric devices, such as a piezoelectric quartz material and the substrate have mismatched thermal expansion coefficients. This mismatch can cause mechanical stresses to be induced in the quartz as time goes by during the life of such devices, as the quartz and substrate expand and contract over temperature variations. Further, mechanical shock transferred to the quartz through its mounting structure can increase mechanical stresses that in addition to the thermal stress, adversely affect the frequency, accuracy and longevity of such devices.
Various attempts over the years have been developed to compliantly mount piezoelectric quartz devices to a substrate. For purposes of this application, a compliant mount for a piezoelectric device, is a mounting device, apparatus or other mounting means that attempts to reduce or minimize mechanical stresses on the piezoelectric quartz element. Some prior art compliant mounting devices have used thin foil tabs that act as spring-type mounting structures that attempt to isolate the quartz element from its substrate. Other types of compliant mounting structures have attempted to use substrate materials having thermal expansion coefficients which more closely match the thermal expansion coefficient of the quartz material itself.
Examples of two prior art devices are shown in FIG. 1a and FIG. 1b.
In FIG. 1a, a loose tolerance clock oscillator 10 is shown. It is made as follows. Epoxy 12 is deposited onto a ceramic package 14. A quartz crystal 16 is placed onto the epoxy 12 and the epoxy 12 is cured in an oven. Two time consuming wirebonds 18 are then made between the quartz 16 and the ceramic 14. The coupling between the quartz 16 and the package 14 is rigid and direct and the frequency stability of the device is marginal, requires meticulous detail to assemble, and is not easily adapted to mass production. Also mechanical shock performance is poor because the mounting is rigid and the wirebonds can easily break.
In FIG. 1b, a cantilever type crystal mount 20 is shown. It is made as follows. First, epoxy 22 is dispensed on a left side of the ceramic 24. Next, a crystal 26 is suitably placed so that a bottom electrode 30 contacts epoxy 22. Thereafter, the cantilever mount 20 is turned upside down and inserted into a mating tool that sets the gap between the crystal and the ceramic 24 at the other side 28 at about 0.003" (0.08 mm). The cantilever mount 20 is then cured in an oven while upside down in the mating tool. Thereafter, an upper electrode 32 of the crystal 26 is coupled to a lead in the left side of the ceramic 24 with a conductive adhesive 34 extending from the upper electrode 34 to the lead (not shown) on the left side of the ceramic 24. The adhesive 34 is then cured. This operation is very difficult if not impossible to automate, and the cantilever mount 20 has marginal mechanical shock performance.
Most if not all of the prior art compliant mounting schemes are difficult to use because of the small physical dimensions that modern piezoelectric quartz elements have. Using bent foil tabs alone, for example, to compliantly mount a small sliver of quartz onto a substrate is not a structure that lends itself to economic mass production of quartz crystal devices.
There is a need for an improved method of mounting piezoelectric elements with ceramic substrates: (i) to minimize the mechanical stresses induced due to the thermal expansion mismatch between the two; (ii) to provide a mechanically sufficient coupling such that the device can withstand mechanical shocks; and (iii) to provide a method of crystal attachment which is adaptable to mass production. Accordingly, a low cost, readily-manufacturable, compliant mount for a piezoelectric device would be an improvement over the prior art. A method by which quartz devices can be easily and reliably attached to a substrate and which isolates the quartz element from mechanical stresses would be an improvement over the art.

Method of mounting a piezoelectric element to a substrate using compliant conductive materials


A dielectric ceramic has a ceramic structure of crystal grains and grain boundaries between the crystal grains. The crystal grains are of a main component represented by the formula ABO3 and an additive containing a rare earth element wherein A is at least one of barium, calcium, and strontium, barium being an essential element, and B is at least one of titanium, zirconium, and hafnium, titanium being an essential element. The average rare earth element concentration in the interior of the crystal grains is about 50% or less the average rare earth element concentration at the grain boundaries. Furthermore, about 20% to 70% of the crystal grains have a rare earth element concentration in the center of the crystal grain of at least about {fraction (1/50)} the maximum rare earth element concentration in a region extending inward from the surface by a distance corresponding to about 5% of the diameter of the crystal grain.

1. Field of the Invention
The present invention relates to dielectric ceramics, methods for making and evaluating the same, and monolithic ceramic electronic components. In particular, the present invention relates to thin monolithic ceramic electronic components such as thin monolithic ceramic capacitors.
2. Description of the Related Art
Monolithic ceramic capacitors, as an example of monolithic ceramic electronic components relating to the present invention, are typically produced as follows.
Green ceramic sheets, each composed of a dielectric ceramic material and provided with an internal electrode pattern of a conductive material, are prepared. The dielectric ceramic material may comprise BaTiO3, for example.
A plurality of green ceramic sheets, including the above sheets provided with the internal electrode patterns, is stacked and is thermally compressed to form a green composite.
The green composite is fired to prepare a sintered composite, which has internal electrodes formed of the above-described conductive material.
External electrodes are formed on outer faces of the composite so that the external electrodes are electrically connected to predetermined internal electrodes. The external electrodes are formed, for example, by applying a conductive paste containing a conductive metal powder and a glass frit on the outer faces of the composite and baking the composite. A monolithic capacitor is thereby formed.
In order to reduce production costs of the monolithic ceramic capacitors, relatively inexpensive base metals such as nickel and copper are often used nowadays as the conductive materials for the internal electrodes. Unfortunately, the green composite must be fired in a neutral or reducing atmosphere to prevent oxidation of the base metal in the production of monolithic ceramic capacitors having such internal electrodes formed of base metals. As a result, the dielectric ceramic used in the monolithic ceramic capacitor must have resistance to reducing atmosphere.
BaTiO3-rare earth oxide-Co2O3 compositions for such dielectric ceramics having resistance to reducing atmosphere are disclosed in Japanese Unexamined Patent Application Publication Nos. 5-9066, 5-9067, and 5-9068. Dielectric ceramics having a high dielectric constant, a small change in dielectric constant with temperature and a long life at high-temperature load are disclosed in Japanese Unexamined Patent Application Publication Nos. 6-5460 and 9-270366.
Trends toward miniaturization and higher capacitance are noticeable in monolithic ceramic capacitors with the rapid miniaturization of electronic components as a result of recent great advances in electronics technologies.
The requirements regarding reliability for dielectric ceramics which are fired in an atmosphere which does not oxidize base metals used in internal electrodes are a high dielectric constant, a small change in dielectric constant with temperature and time, and high electrical insulation for thinner dielectric ceramic layers. The above-described known dielectric ceramics, however, do not completely satisfy these requirements.
For example, the dielectric ceramics disclosed in Japanese Unexamined Patent Application Publication Nos. 5-9066, 5-9067, and 5-9068 above satisfy the X7R characteristics in the EIA Standard and exhibit high electrical insulation, but do not always satisfy the demands of the market, namely, they may be sufficiently reliable, when the thicknesses of the dielectric ceramics are reduced to about 5 xcexcm or less and particularly 3 xcexcm or less.
In the dielectric ceramic disclosed in Japanese Unexamined Patent Application Publication No. 6-5460, the particle size of the BaTiO3 powder used is large. Thus, its reliability decreases and the change in electrostatic capacitance with time increases as the thickness of the dielectric ceramic layer decreases.
Also, the reliability of the dielectric ceramic disclosed in Japanese Unexamined Patent Application Publication No. 9-270366 decreases and the change in electrostatic capacitance with time increases while applying a DC voltage as the thickness of the dielectric ceramic layer decreases.
When the same rated voltage is applied to a dielectric ceramic layer having a reduced thickness, which agrees with miniaturization and higher capacitance requirements of the monolithic ceramic capacitor, a larger electric field is applied to each layer of the dielectric ceramic. Thus, the insulating resistance at room or high temperature decreases, resulting in significantly decreased reliability. Accordingly, the rated voltage must be reduced when the thickness of the dielectric ceramic layers in the known dielectric ceramic is reduced.
There have been demands that monolithic ceramic capacitors have high insulation resistance in high electric fields and have high reliability, and that they can be used at high rated voltages even when the thicknesses of the dielectric ceramic layers are reduced.
It is known that the electrostatic capacitance of a monolithic ceramic capacitor varies over time because a DC voltage is applied in use. As the thickness of the dielectric ceramic layers decreases, the DC electric field per dielectric ceramic layer increases. As a result, the electrostatic capacitance changes more significantly over time.
Thus, there have been demands that monolithic ceramic capacitors have a small change in electrostatic capacitance when a DC voltage is applied in use.
Also, monolithic ceramic electronic components other than the monolithic ceramic capacitors have the above-described problems and demands.
Accordingly, an object of the present invention is to provide a dielectric ceramic exhibiting a high dielectric constant, small changes in dielectric constant with temperature and over time when a DC voltage is applied in use, a high product of insulation resistance and electrostatic capacitance (CR product), and a prolonged lifetime, in terms of insulation resistance, under accelerated testing at high temperature and high voltage.
Another object of the present invention is to provide a method for making the dielectric ceramic.
Another object of the present invention is to provide a method for evaluating the dielectric ceramic in which dielectric ceramics having the above superior characteristics can be readily and efficiently selected, for example, in a designing process.
Another object of the present invention is to provide a monolithic electric component comprising the above dielectric ceramic.
The present invention is directed to a dielectric ceramic having a ceramic structure comprising crystal grains and grain boundaries between the crystal grains, the crystal grains comprising a main component represented by the formula ABO3 and an additive containing a rare earth element wherein A is at least one of barium, calcium and strontium, barium being an essential element, and B is at least one of titanium, zirconium and hafnium, titanium being an essential element.
This dielectric ceramic further satisfies the following conditions: (1) the average rare earth element concentration in the interior of the crystal grains is about 0.5 or less the average rare earth element concentration at the grain boundaries, and (2) about 20% to 70% of the crystal grains have a rare earth element concentration in the center of the crystal grain of at least about {fraction (1/50)} the maximum rare earth element concentration in a region extending inward from the surface by a distance corresponding to about 5% of the diameter of the crystal grain.
This dielectric ceramic exhibits a high dielectric constant, small changes in dielectric constant with temperature and over time when a DC voltage is applied in use, a high product of insulation resistance and electrostatic capacitance (CR product), and a prolonged lifetime, in terms of insulation resistance, under accelerated testing at high temperature and high voltage.
A thin monolithic ceramic electronic component including dielectric ceramic layers composed of this dielectric ceramic is highly reliable for a long time.
The present invention is also directed to a method for making such a dielectric ceramic. The method for making the dielectric ceramic comprises the steps of mixing fractions of AO, BO2 and the rare earth element, calcining the mixture in air, and pulverizing the mixture to prepare a modified ABO3 powder in which the rare earth element is present in the interiors of the particles; mixing the remaining fractions of the AO and BO2, calcining the mixture in air, and pulverizing the mixture to prepare an ABO3 powder in which the rare earth element is not present in the interiors of the particles; and mixing the modified ABO3 powder, the ABO3 powder and the remaining fraction of the rare earth element, and firing the mixture.
Since the ABO3 powder, the modified ABO3 powder and the rare earth element are mixed at two stages, the above-described concentration profile of the rare earth element is readily achieved in the crystal grains. In conventional one-shot mixing, such a concentration profile is barely achieved.
Furthermore, the present invention is directed to a method for evaluating a dielectric ceramic that has a ceramic structure comprising crystal grains and grain boundaries between the crystal grains, the crystal grains comprising a main component represented by the formula ABO3 and an additive containing a rare earth element wherein A is at least one of barium, calcium and strontium, barium being an essential element, and B is at least one of titanium, zirconium and hafnium, titanium being an essential element.
This method comprises the steps of measuring the average rare earth element concentration in the interiors of the crystal grains and the average rare earth element concentration at the grain boundaries; determining whether or not a first condition that the average rare earth element concentration in the interior of the crystal grains is about xc2xd or less the average rare earth element concentration at the grain boundaries is satisfied; measuring the rare earth element concentration in the center of each crystal grain and the maximum rare earth element concentration in a region extending inward from the surface by a distance corresponding to about 5% of the diameter of the crystal grain; determining whether or not a second condition that about 20% to 70% of the crystal grains each have a rare earth element concentration in the center of the crystal grain which is at least about {fraction (1/50)} of the maximum rare earth element concentration in the region is satisfied; and assuming the dielectric ceramic to be nondefective when the dielectric ceramic satisfies the first and second conditions.
This method condenses a cycle of designing, making and evaluation of a dielectric ceramic.
The present invention is also directed to a monolithic ceramic electronic component comprising a composite comprising a plurality of stacked dielectric ceramic layers; and internal electrodes formed along predetermined interfaces between the dielectric ceramic layers, the dielectric ceramic layers comprising the above-described dielectric ceramic.
Preferably, the internal electrodes comprise a base metal.
Since the dielectric ceramic according to the present invention exhibits high resistance to reducing environments, the base metal can be used as a conductive component of the internal electrodes.
The monolithic ceramic electronic component is preferably a monolithic ceramic capacitor. In such a case, the monolithic ceramic electronic component further comprises a first external electrode and a second external electrode formed on outer faces of the composite, wherein the internal electrodes are arranged in the stacking direction of the composite and are alternately and electrically connected to the first external electrode and the second external electrode to define the monolithic ceramic capacitor.
This monolithic ceramic capacitor has a large capacitance regardless of its compactness and can be used at conventional rated voltages. Thus, the thickness of the dielectric ceramic layers in the monolithic ceramic capacitor can be reduced to, for example, about 1 xcexcm without problems.

Dielectric ceramic, methods for making and evaluating the same, and monolithic ceramic electronic component


A pliers for gripping small pieces of glass to be ground as a support foot which can ride on a surface from which the grinder projects and a clamping jaw which can hold the piece of glass against a resting surface formed on this foot.

In the grinding of glass, for example, in the production of leaded glass, stained glass, or other forms of ornamental glass, especially Tiffany-type lamps, glass decor, mirrors and the like, to form small pieces of glass of particular colors or textures in very specific shapes or dimensions by cutting the pieces from a larger piece of glass, the cutting operation generally involves scoring and breakage against a score line. In the breaking of the glass to form such pieces, sharp edges may result and these edges must be ground at least in part for safe handling. It is also necessary in many cases to grind glass pieces for shaping or for imparting a certain degree of dimensional accuracy thereto.
In the grinding of small glass pieces, it has been found that it is difficult to hold the glass piece with the requisite pressure against the grinder. In practice, this has been recognized in the past and indeed rods, bars or other pushers have been used to press a glass piece along a guide surface against a grinder. In most cases, however, the fingers must also be used and there is a substantial danger of injury to the finger.

Device for holding small glass pieces for grinding


A heat-treating method for an indium-doped dislocation-free gallium arsenide monocrystal having a low carbon concentration and grown in the Liquid Encapsulated Czochralski method, comprising a two-step heat treatment:. (i) heating the monocrystal at a temperature between 1050.degree. C. and 1200.degree. C. for a predetermined time length, and cooling the monocrystal quickly; and PA0 (ii) heating the monocrystal at a temperature between 750.degree. C. and 950.degree. C. for a predetermined time length, and cooling the monocrystal quickly.

The present invention relates to a method for heat-treating indium-doped dislocation-free gallium arsenide monocrystal with a view to improve properties of the gallium arsenide monocrystals.
Gallium arsenide monocrystal is grown horizontally by the horizontal Bridgman's method or vertically by the liquid encapsulated Czochralski (LEC) method. The monocrystal body obtained by means of the latter method is generally cylindrical except at the end portions (FIG. 4) so that wherever the body is cut by a plane normal to the axis of the body the cross section of the body is circular. This is propitious for obtaining circular wafers, which are the industrial standard wafers and are, therefore, acceptable as they are to the device processing lines where the wafers are further processed. Also the liquid encapsulated Czochralski method is regarded very highly for the facts that it is easier to render a wafer dislocation-free in this method and that it is relatively easy to obtain monocrystal gallium arsenide wafers of relatively large diameters in this method.
The gallium arsenide monocrystal is extensively used as a material to make substrates for various devices such as light emitting diode, light sensing device (i.e., light detector), devices for microwave communication system. Since the electron mobility is far greater in gallium arsenide monocrystal than it is in silicon semiconductor, the development of the substrates for integrated circuits having high electron mobility has become very active recently. Therefore, to reduce the density of or to completely eliminate the existence of the dislocation in gallium arsenide monocrystal is an increasingly acute subject of many researchers in this field of technology.
Incidentally, it is generally accepted that the stresses exerted on a crystal grown from the melt by a thermal shock is a chief cause of dislocations in the crystals.
As a result of the efforts made with the view of obtaining dislocation-free gallium arsenide monocrystal, various techniques have been developed to render the gallium arsenide monocrystal dislocation-free, and among them are procedures specially applicable in the liquid encapsulated Czochralski method. An example of the procedures usefully adopted in the liquid encapsulated Czochralski method is disclosed by B. C. Grabmaier et al., in Journal of Crystal Growth 13/14 635-639 (1972). According to the disclosure, the increase in dislocation density caused by sealing or a seal crystal itself in the grown crystal especially in the vicinity of the seed crystal/grown crystal interface is hindered by means of necking, which is a procedure comprising growing a 10 to 20 mm-long thin monocrystal portion having a diameter of 1 or 2 mm from the seed, and adopting a small temperature gradient at the seed crystal/grown crystal interface.
As a method for decreasing the dislocation density in gallium arsenide monocrystal, a technique is proposed wherein additives such as Si, Te, Sb, Al, In, and B are added to the gallium arsenide monocrystal. According to the method, these additives have a tendency of adhering to the dislocations as the dislocations develop in the growing crystal whereby the propagation and growth of the dislocations are prevented. Among the additives, indium has proved a successful dopant for industrially obtaining a dislocation-free gallium arsenide monocrystal. According to an example disclosed in Japanese Kokai No. 61-222991, it is possible to obtain dislocation-free gallium arsenide monocrystal without applying necking operation, if a molten gallium arsenide containing indium in an amount of about 6 weight % is prepared in a quartz crucible to be employed as the melt, and the seed to raise the monocrystal from the melt is doped with indium in an amount of 0.7 weight %. More generally, Japanese Kokai No. 61-222991 teaches that to obtain dislocation-free gallium arsenide monocrystal the seed should be doped with indium as much as kC weight % where k is a segregation coefficient of indium and C is the concentration of indium in the melt of gallium arsenide.
The indium-doped dislocation-free gallium arsenide monocrystal thus obtained is certainly free of dislocations, and from this fact it appears that the gallium arsenide is crystallographically uniform. However, it has been observed that thus grown indium-doped dislocation-free gallium arsenide monocrystal rod, as it is, exhibits ununiformity in axial direction in such respects as electric properties, the concentrations of traps such as EL2, the concentration of carbon that substituted arsenic, and occurrence of the micro precipitates. Even if such a monocrystal is in semi-insulation state, the monocrystal substrates cut therefrom will be such that when they are made into transistors by means of the ion-implantation procedure, the resulting transistors have inconsistent threshold voltages Vth, which determine the on-off positions in switching action.
An In-doped dislocation-free gallium arsenide monocrystal is ordinarily obtained by the liquid encapsulated Czochralski (LEC) method. As shown in FIG. 3, the liquid encapsulated Czochralski method employs a pressurized chamber (furnace) schematically drawn by the frame designated by 1, and this pressurized chamber 1 is filled with an inert gas. A PBN (pyrolytic boron nitride) crucible 2 is installed in the middle of the chamber 1 such that the crucible 2 is capable of being rotated around its center line by means of a shaft. Reference numeral 3 designates an In-doped melt of gallium arsenide contained in the crucible 2. The surface of the melt 3 is entirely covered with a layer of another melt 4, which is of B.sub.2 O.sub.3 whereby the melt 3 is sealed from the gaseous environment. A heating means 5 is provided to controllably heat the melt 3. The seed is lowered to the melt 4 and, penetrating the layer of the melt 4, it is caused to touch the surface of the melt 3. Then, while the crucible is slowly rotated by the shaft in the direction indicated by a curved arrow below (FIG. 3), the seed is moved upward very slowly as it is rotated in the opposite direction as indicated by a curved arrow above. The monocrystal grows from the lower tip of the seed as the seed is raised, and a monocrystal ingot 10 as shown in FIG. 4 is obtained in the end. In FIG. 3, reference numeral 6 designates a heat shield.
The In-doped dislocation-free monocrystal ingot or rod 10 thus obtained tends to have inconsistent properties along the axial direction, as stated above, and it is postulated that this is a result of the fact that the thermal history experienced by different portions of the monocrystal rod is not always the same. Especially the conditions under which the cooling process is conducted are difficult to maintain fixed or uniform in time with respect to the different portions of the monocrystal rod.
Koji Yamada et al reported in their preparatory treatise for the 47th Autumn Season Applied Physics Symposium, 22a-K-8 (1986), that as they analyzed an In-doped gallium arsenide monocrystal rod grown by the LEC method by means of the infrared transmission method (IRT) as well as the KOH etching method, they observed the existence of microdefects which were not dislocation in the monocrystal rod. Further, they reported in their preparatory treatise for the 34th Spring Season Applied Physics Symposium, 30a-Z-3 (1987), that the formation of the same microdefects was strongly dependent upon the thermal history below 1000.degree. C.
These reports showed that there exist microdefects which are not dislocations and are distributed ununiformly, in the In-doped dislocation-free gallium arsenide monocrystal rod and that the formation of the microdefects is affected by the thermal history during the monocrystal pulling-up operation. However, there has been disclosed no solution for making the distribution of the microdefects uniform throughout the monocrystal rod nor for eliminating the microdefects.
It is an object of the invention, therefore, to provide a method for thermally treating an indium-doped dislocation-free gallium arsenide monocrystal rod which method is capable of making homogeneous in the axial direction of the monocrystal rod the electric properties such as resistivity, the concentrations, i.e., the densities of deep traps such as EL2, the concentration of carbon that substituted arsenic at arsenic sublattice site (C.sub.As), and the density and size of microprecipitates, and thereby producing a gallium arsenide monocrystal from which it is possible to obtain high quality gallium arsenide monocrystal substrates desirous for manufacturing semiconductor devices.

Method for heat-treating gallium arsenide monocrystals