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Showing papers by "Varian Associates published in 1989"


Patent
26 May 1989
TL;DR: In this article, a modular wafer processing machine is provided which is based on interconnected handling units having wafer handling arms, each unit can pass a wafer to another unit in the same vacuum environment to a processing module.
Abstract: A modular wafer processing machine is provided which is based on interconnected handling units having wafer handling arms. Each unit can pass a wafer to another unit in the same vacuum environment to a processing module.

244 citations


Patent
07 Dec 1989
TL;DR: In this article, a symmetric set of fundamental-mode waveguides are used to couple energy in phase from the operating electromagnetic mode but in anti-phase with respect to an unwanted mode of lower cutoff frequency than the operating mode, thereby neutralizing coupling to the unwanted mode.
Abstract: In a gyrotron cavity resonator, generated energy is extracted into a symmetric set of fundamental-mode waveguides (34) by ports (30, 32) disposed to couple energy in phase from the operating electromagnetic mode but in anti-phase with respect to an unwanted mode of lower cutoff frequency than the operating mode, thereby neutralizing coupling to the unwanted mode. A second set of interspersed ports may be disposed to load degenerate, orthogonal modes.

161 citations


Journal ArticleDOI
TL;DR: In this article, a method for computing the resonant frequency in a complex cavity consisting of a series of waveguide sections is derived, restricted to transitions in which one waveguide is wholly contained in the other.
Abstract: A method for computing the resonant frequency in a complex cavity consisting of a series of waveguide sections is derived. The analysis is restricted to transitions in which one waveguide is wholly contained in the other. An eigenvalue problem is formed by cascading the scattering matrix from a given section outwards to the ends of the complex cavity, with appropriate boundary conditions at the ends. The eigenvalue equation is solved numerically by searching for a complex frequency, the cavity Q being determined by half of the ratio of the real to the imaginary part of the frequency. The technique is easily implemented numerically and shows good agreement with experiment. This method is suitable for modeling both abrupt changes in radius and smoothly varying tapers. >

127 citations


Patent
22 Nov 1989
TL;DR: In this paper, a radiotherapy unit with a beam of rays propagating from a focal point along a beam axis comprises a radiator head arranged on the beam axis with a double-focus multi-leaf collimator.
Abstract: A radiation therapy unit with a beam of rays propagating from a focal point along a beam axis comprises a radiator head arranged on the beam axis with a double-focus multi-leaf collimator. The multi-leaf collimator exhibits a plurality of adjacently arranged diaphragm plates which in each case have two side faces, two front faces and an inside and an outside face. Each side face of each diaphragm plate forms a part of a surface area of a cone, all such cones having both a common cone axis which extends perpendicularly to the beam axis through the focal point, and a common cone point which coincides with the focal point. Means are provided for guiding the diaphragm plates so that each diaphragm plate performs a pure rotation about the cone axis during its displacement.

84 citations


Patent
13 Dec 1989
TL;DR: In this article, a high voltage, high power DC power supply with a single turn primary winding driven through a resonating capacitor by an AC source having a frequency in excess of about 100 kHz is described.
Abstract: A high voltage, high power DC power supply includes a single turn primary winding driven through a resonating capacitor by an AC source having a frequency in excess of about 100 kHz The primary winding includes a pair of concentric cylindrical metal walls having opposite ends electrically connected to each other A volume between the walls includes plural secondary winding assemblies, having different axial positions along the walls Each of the assemblies includes an annular magnetic core surrounding the interior wall, a winding on the core and a voltage doubler rectifier DC voltages developed across each secondary winding assembly by the rectifier are added together to provide the high voltage, high power output The power supply energizes an X-ray tube having a grounded anode and a cathode at a DC voltage of approximately -150 kV, with a power requirement of between 15 and 60 kW The power supply and X-ray tube are mounted on a rotatable gantry including a slip ring assembly for coupling a relatively low voltage excitation source to the power supply

73 citations


Journal ArticleDOI
01 Jan 1989-Toxicon
TL;DR: Comparisons in the HPLC analyses of extracts from toxic shellfish, plankton tows and cultured dinoflagellates from the Rias Vigo and Pontevedra clearly indicate that Gymnodinium catenatum Graham is the organism responsible for recent PSP episodes.

73 citations


Patent
07 Nov 1989
TL;DR: An ion beam scanning method and apparatus produce a parallel, scanned ion beam with a magnetic deflector having, in one instance, wedge-shaped pole pieces that developed a uniform magnetic field as discussed by the authors.
Abstract: An ion beam scanning method and apparatus produce a parallel, scanned ion beam with a magnetic deflector having, in one instance, wedge-shaped pole pieces that develop a uniform magnetic field. A beam accelerator for the scanned beam has a slot-shaped passage which the scanned beam traverses. The beam scan and the beam traverse over a target object are controlled to attain a selected beam current and corresponding ion dose on a target object. Methods and apparatus are disclosed for increasing ion beam utilization efficiency without adversely effecting dose accuracy.

65 citations


Patent
09 Jun 1989
TL;DR: In this article, a mechanical scanning system for a batch ion implanter includes a disk (40) for mounting wafers at sites near its periphery and a disk drive assembly (50) for rotating the disk.
Abstract: A mechanical scanning system for a batch ion implanter includes a disk (40) for mounting wafers (39) at sites (42) near its periphery and a disk drive assembly (50) for rotating the disk (40). The disk (40) and the disk drive assembly (50) are supported in an end station vacuum chamber (30) by a scan arm (44) which extends through a sealed opening (64) in an access door (60). A scan drive assembly (52) attached to the access door (60) scans the scan arm (44) and the disk (40) in an arc-shaped path. Simultaneous rotation and scanning of the disk cause the ion beam (20) to be distributed over the surfaces of the wafers (39) mounted on the disk (40). A pivot drive assembly (54) rotates the scan arm (44) and the disk (40) about a pivot axis (C) between an implant position and a load/unload position. A bellows (102) seals the scan arm (44) to the vacuum chamber (30) while transmitting arc-shaped movement into the vacuum chamber (30). A bellows guide apparatus guides an intermediate portion of the bellows so as to limit lateral distortion caused by pressure differences applied to the bellows in the combination with asymmetrical deflection thereof.

48 citations


Journal ArticleDOI
01 Nov 1989
TL;DR: In this paper, high-temperature magic-angle-spinning (MAS) NMR spectroscopy was used to observe the exchange of Na+ among the alkali sites in a high-Na nepheline at temperatures as high as 500° C.
Abstract: Dynamics in minerals at time scales from seconds to microseconds are important in understanding mechanisms of displacive phase transitions, diffusion, and conductivity. High resolution, magic-angle-spinning (MAS) NMR spectroscopy can directly show the rates of exchange among sites, potentially providing less model-dependent information than more traditional NMR relaxation time measurements. Here we use a newly developed high temperature MAS probe (Doty Scientific, Inc.) to observe the exchange of Na+ among the alkali sites in a high-Na nepheline at temperatures as high as 500° C. Observed exchange rates are consistent with correlation times derived from cation diffusivity.

35 citations


Patent
07 Sep 1989
TL;DR: In this paper, a broadband interconnection between a microstrip and a coplanar waveguide is provided without use of via holes by using anisotropic etching to form a sloped surface between connection points.
Abstract: A broadband interconnection between a microstrip and a coplanar waveguide is provided without use of via holes by using anisotropic etching to form a sloped surface between connection points. The sloped surface is then metallized to provide the interconnection.

32 citations


Journal ArticleDOI
TL;DR: In inspection of the high-energy X-ray depth doses for a 10 x 10 cm field at an SSD of 100 cm, it was found that the dose-weighted average energy of the filtered beam plotted smoothly against depth dose, and it was suggested that this parameter be used as a true measure of beam quality, removing the discrepancies introduced by the use of nominal MV.
Abstract: Supplement 17 of the British Journal of Radiology is a survey of central-axis depth doses for radiotherapy machines, patterned largely on BJR Supplement 11 published some 11 years earlier. Inspection of the high-energy X-ray depth doses for a 10 x 10 cm field at an SSD of 100 cm disclosed large differences between the two sets of data, especially for qualities above 8 MV. For example, a depth dose of 80% at 10 cm is rated at about 19 MV according to BJR Supplement 11, and 23 MV according to BJR Supplement 17. It was found that the Supplement 17 depth-dose data above 8 MV were erratic, but that the Supplement 11 data could be represented by an analytical expression, providing a unique means of assigning MV quality. It was also found that the dose-weighted average energy of the filtered beam plotted smoothly against depth dose. For dosimetric purposes, it is suggested that this parameter be used as a true measure of beam quality, removing the discrepancies introduced by the use of nominal MV for this purpose.

01 Jan 1989
TL;DR: A recent Symposium on Rapid Thermal Annealing (RTP) and Chemical Vapor Deposition (CVD) was held at the University of Sheffield as mentioned in this paper, with a focus on the integration of rapid thermal processing into manufacturing environments.
Abstract: This volume contains papers presented at the symposium on rapid thermal annealing/chemical vapor deposition and integrated processing. Rapid thermal processing is growing in many directions. The seven sessions presented during this symposium cover recent developments in the traditional RTP subjects such as ion implant annealing in Si and III-V materials, metals processes (silicides and contact alloying), and oxide growth in addition to newer areas of CVD using RTP techniques, integrated processing and complex dielectric structures (such as ONO). Work in all aspects of RTP is progressing and it appears that the integration of rapid thermal processing into manufacturing environments is finally occurring.

Patent
06 Mar 1989
TL;DR: In this paper, a pair of coupled surface coils are arranged to provide active detuning whereby the shape of the RF field due to the RF current in one coil is modified in a calibrated fashion by the RF currents in the second coil.
Abstract: A pair of coupled surface coils are arranged to provide active detuning whereby the shape of the RF field due to the RF current in one coil is modified in a calibrated fashion by the RF current in the second coil whereby a selected fraction of the RF field of one coil may be selectively added or subtracted from the RF field of the one other coil thereby shaping the RF field.

Patent
15 Feb 1989
TL;DR: In this paper, a field effect transistor (FET) structure suitable for use at microwave frequencies is fabricated on a planar surface of a semi-insulating single crystal GaAs substrate which has been cut and polished to present the (110) surface.
Abstract: A field effect transistor (FET) structure suitable for use at microwave frequencies is fabricated on a planar surface of a semi-insulating single crystal GaAs substrate which has been cut and polished to present the (110) surface. This orientation is selected because of its non-polar and other unique surface and interface properties. The (110) crystal axis is tilted from the normal of the planar surface in the direction to expose more of the (111) Ga face about 5° to facilitate molecular beam epitaxial (MBE) growth of smooth, defect-free thin films. An elongate gate electrode is formed along the bottom of an anisotropically etched trench having a pair of longitudinal sidewalls, one vertical and the other tilted outwardly. The trench is selectively oriented on the substrate to facilitate such anisotropic etching. Source and drain electrodes are respectively formed proximate the outwardly tilted and vertical trench sidewalls thereby forming a FET with a higher drain-to-gate breakdown voltage combined with lower parasitic resistance between the source and gate electrode. The invention has demonstrated potential for high speed digital circuits as well a microwave power FET applications.

Patent
08 Feb 1989
TL;DR: In this article, a high-intensity rotating anode X-ray tube with a liquid or fluid-cooled rotating-anode is described. But no ferrofluid-type rotating joints or O-ring gasket-type seals are required so that the interior of the tube maintains a high vacuum.
Abstract: Several different embodiments of high-intensity rotating-anode X-ray tubes are shown which use a liquid or fluid-cooled rotating-­anode. No ferrofluid-type rotating joints or O-ring gasket-­type seals are required so that the interior of the tube maintains a high vacuum without pumping. A bellows (18) permits mechanical coupling to interior structures of the tube while providing a completely vacuum tight enclosure. All joints may be hard soldered or brazed together so the entire system can be baked at a high temperature during pumpdown.


Journal ArticleDOI
TL;DR: In this paper, the authors studied the Be incorporation and diffusion in heavily doped MBE grown GaAs epilayers and found that the profile is significantly different from the designed structure.

Patent
Eric L. Mears1
25 Oct 1989
TL;DR: In this paper, the surface film is formed by oxygen plasma treatment of the silcone rubber layer and a high purity polymer layer is fabricated by evacuating the mold cavity and the resin container prior to injection of resin.
Abstract: Thermal transfer between a semiconductor wafer and a platen during vacuum processing is provided through a soft, thermally-conductive polymer layer having a thin, hard surface film. The soft polymer layer, which is preferably silicone rubber containing thermally-conductive particles, conforms to surface irregularities on the wafer and has low thermal resistance. The surface film is preferably silicon dioxide in the form of a multiplicity of flat plates integrally formed on the silicone rubber. Adherence of the wafer and of foreign matter to the polymer layer is prevented by the surface film. In addition, the underlying polymer layer is protected by the surface film. A high purity polymer layer is fabricated by evacuating the mold cavity and the resin container prior to injection of resin. The mold for the polymer layer utilizes a hard, smooth mold release surface and a resilient gasket between the platen and the mold release surface. The gasket establishes the dimensions of the polymer layer and seals the mold cavity. The surface film is formed by oxygen plasma treatment of the silcone rubber layer.

Journal ArticleDOI
TL;DR: In this paper, an elastic inner wall coating in the fused silica capillaries used for Micro-LC (LC on packed fused-silica capillary columns) stabilizes the packed bed and increases column efficiency and life expectancy.
Abstract: An elastic inner wall coating in the fused silica capillaries used for Micro-LC (LC on packed fused silica capillary columns) stabilizes the packed bed and thus increases column efficiency and life expectancy. Probably the particles of packing material are partly forced into the elastic polymer layer which thus holds the packing in position. Bonded polymers of very different chemical polarity can be used with equally good results. Variation of the coating layer thickness shows that there is an optimum value around 0.3 μm. A discussion of various wall effects in LC columns is presented. The i.d. of the columns is a most important parameter in this respect.

Patent
21 Mar 1989
TL;DR: An isolation valve includes a housing having a port and a seal plate for sealing the port as mentioned in this paper, where the seal plate first moves linearly with the shaft until the guide frame stops against the housing.
Abstract: An isolation valve includes a housing having a port and a seal plate for sealing the port. The seal plate is linked to a shaft which carries a guide frame. To close the port, a drive mechanism drives the shaft linearly in one direction. The seal plate first moves linearly with the shaft until the guide frame stops against the housing. The seal plate then moves linearly in a direction perpendicular to a surface of the housing containing the port until it seals the port. Motion of the drive shaft in the opposite direction causes the seal plate to retrace its path. In one embodiment, the valve includes a second seal plate for sealing a second port. A spring between the guide means and the shaft provides pre-load which maintains the seal plates in a retracted position until the frame stops against the housing. An extension spring between the first and second seal plates eliminates play in the link mechanism and extends valve life.

Patent
Albert P. Zens1
17 Mar 1989
TL;DR: In this paper, the inductor is split to form two generally semi-cylindrical members (40,42), each member being H-shaped, with the cross piece of the H acting as a generator of the cylinder and the tips of the upright portions of H lying adjacent the corresponding tips of other member, and connected by chip capacitors.
Abstract: A double tuned circuit for NMR appartus normally has a single inductor common to the two resonant circuit portions. In the present case the inductor is split to form two generally semi-cylindrical members (40,42), each member being H-shaped, with the cross piece of the H acting as a generator of the cylinder and the tips of the upright portions of the H lying adjacent the corresponding tips of the other member, and connected by chip capacitors (44-47). Capacitors and inductors connect portions of the H to ground and to two sources of RF energy of different frequency (64, 66), and a bridge capacitor (69) is provided between the two input circuit portions from the sources.

Patent
13 Feb 1989
TL;DR: In this article, a free-electron laser has a wiggler for a linear electron beam comprising two sets of magnetic polepieces 26, 28 periodically spaced along opposite sides of the beam, and the polepieces of one set 28 are displaced along the beam from the other set 26 by one-half period.
Abstract: A free-electron laser has a wiggler for a linear electron beam comprising two sets of magnetic polepieces 26, 28 periodically spaced along opposite sides of the beam. The polepieces of one set 28 are displaced along the beam from the other set 26 by one-half period. A uniform longitudinal magnetomotive force generates fields between polepieces having transverse components 22 alternating between the sets 26, 28, providing a very short periodicity and hence, high frequency wave radiation.

Patent
10 Oct 1989
TL;DR: In this paper, the surface film is formed by oxygen plasma treatment of the silicone rubber layer and a high purity polymer layer is fabricated by evacuating the mold cavity and the resin container prior to injection of resin.
Abstract: Thermal transfer between a semiconductor wafer and a platen during vacuum processing is provided through a soft, thermally-conductive polymer layer having a thin, hard surface film. The soft polymer layer, which is preferably silicon rubber containing thermally-conductive particles, conforms to surface irregularities on the wafer and has low thermal resistance. The surface film is preferably silicon dioxide in the form of a multiplicity of flat plates integrally formed on the silicone rubber. Adherence of the wafer and of foreign matter to the polymer layer is prevented by the surface film. In addition, the underlying polymer layer is protected by the surface film. A high purity polymer layer is fabricated by evacuating the mold cavity and the resin container prior to injection of resin. The mold for the polymer layer utilizes a hard, smooth mold release surface and a resilient gasket between the platen and the mold release surface. The gasket establishes the dimensions of the polymer layer and seals the mold cavity. The surface film is formed by oxygen plasma treatment of the silicone rubber layer.

Patent
14 Jun 1989
TL;DR: In this paper, the authors proposed means to reduce current without seriously reducing energy, or producing unwanted x-rays, by spreading the beam in a scattering foil and subsequently absorbing the outer portion with a blocking wall.
Abstract: A microwave electron accelerator has a very limited range over which pulse beam current can be adjusted without destabilizing the operation of the machine. Therefore, means must be devised to reduce current without seriously reducing energy, or producing unwanted x-rays. One means includes spreading the beam in a scattering foil and subsequently absorbing the outer portion with a blocking wall. In order to make the means adjustable the foil thickness, the size of a passing aperture in the blocking wall or the position of the blocking wall can be adjusted.

Journal ArticleDOI
TL;DR: In this paper, the echo selection COSY phase cycle is compared and the results demonstrate that RF phase cycling is a powerful method for quenching transverse interference, thus improving the quality of the data.

Proceedings ArticleDOI
28 Nov 1989
TL;DR: InP Gunn diodes with current limiting cathodes have proven to be highly efficient, medium power devices at millimeter wave frequencies up to 110 GHz. as discussed by the authors used these basic InP devices in planar microstrip circuits along with special flip chip GaAs varactors.
Abstract: InP Gunn diodes with current limiting cathodes have proven to be highly efficient, medium power devices at millimeter wave frequencies up to 110 GHz. Device and circuit designs have continously improved and cw efficiencies of 21% and 6.3% have recently been obtained at 35 GHz and 94 GHz respectively. Using these basic InP devices in planar microstrip circuits along with special flip chip GaAs varactors, wide band tunable planar VCO's have been developed for these millimeter wave frequencies. Also as a result of the current limiting design, these InP Gunn diodes work well as stabilized reflection amplifiers and stable amplifier designs have been made up to 110 GHz with output power levels sufficient to drive very high output power tubes.

Patent
31 Mar 1989
TL;DR: In this article, a signal processor is used for estimating the position of a scanned ion beam in a ion implantation system, where nonlinear functions such as hyperbolic tangent and logarithm are contained in programmable read only memories to obtain high speed operation.
Abstract: A signal processor receives random input signals from a pair of sensors such as beam sensing electrodes, antennas, microphones or optical position sensors. An estimation equation implemented by the signal processor uses weighted integration of log ratios where the weighting is adaptive and depends upon the values of signal samples being processed. The signal processor uses digital signal processing to provide an estimate of the desired parameter. Nonlinear functions such as hyperbolic tangent and logarithm are contained in programmable read only memories in order to obtain high speed operation. When the signal processor is used in conjunction with channel switching, errors due to channel mismatch are completely eliminated. In a preferred embodiment, the sensors are beam sensing electrodes and the signal processor is used for estimating the position of a scanned ion beam in a ion implantation system.

Journal ArticleDOI
TL;DR: In this paper, As-controlled incorporation rates were investigated under Ga accumulation at the surface of the substrate, and at fluxes and substrate temperatures common for 1.0 micron/hr GaAs growth.
Abstract: RHEED intensity oscillations were used to investigate As-controlled incorporation rates. The measurements were made under Ga accumulation at the surface of the substrate, and at fluxes and substrate temperatures common for 1.0 micron/hr GaAs growth. The results between the dimer and tetramer As species were compared. The transition between Ga and As controlled incorporation rates was constant within 2.5°C for a constant As flux and was independent of the substrate temperature. Also, the As-controlled incorporation rate curves shows two regions as the substrate temperature increases. At low substrate temperatures, the As incorporation rate is substrate temperature independent. Then at higher substrate temperatures, the As incorporation rate has an arrhenius dependence with a positive activation energy. An interpretation of these results is possible by assigning the maximum sticking coefficient of the tetramer to the region where the As incorporation rate is independent of substrate temperature. This assignment allows one to derive the As (dimers and tetramers) sticking coefficient dependence with substrate temperature. The dimer sticking coefficients are greater that the tetramer sticking coefficients for a given substrate temperature and As flux, and the maximum sticking coefficient of the As dimer was determined to be 0.8 in these experiments.

Patent
22 Nov 1989
TL;DR: In this article, a heat sink element is held forcibly in contact with a heat transmitting surface of a heat source for thermal conduction of heat therefrom, and the effectiveness of thermally conductive contact between the heat sink and heat source does not deteriorate during prolonged use.
Abstract: A heat sink element (26), preferably one formed with a relatively large surface area from which thermal energy can be transferred convectively and radiatively to an ambient atmosphere, with or without forced fluid flow, is held forcibly in contact with a heat transmitting surface of a heat source (22) for thermal conduction of heat therefrom. A heat sink attachment element (28) affixed to the heat sink element has flexibly attached castellated extensions (56) formed with tapered end teeth contacting a correspondingly inclined surface of the heat source. The castellated extensions are each subjected to a continual externally applied force and the total resultant force thereof, holding the heat sink element to the heat source, thereby can be maintained or will increase as the assembly experiences thermal cycling and mechanical disturbances during use. The effectiveness of thermally conductive contact between the heat sink and heat source therefore does not deteriorate during prolonged use.

Patent
22 Mar 1989
TL;DR: In this paper, a very fine-mesh, non-emissive shadow grid is formed on the smooth emissive surface 16 of a thermionic cathode by deposition from a vapor a continuous layer 22 of non-EMissive conductive material.
Abstract: A very fine-mesh, non-emissive shadow grid is formed on the smooth emissive surface 16 of a thermionic cathode 12 by deposition from a vapor a continuous layer 22 of non-emissive conductive material. Between the elements 24 of the grid the non-emissive material is removed by bombardment through an apertured mask to restore emissivity between the elevated grid elements 24.