Showing papers by "Varian Associates published in 1994"

Method of high mass resolution scanning of an ion trap mass spectrometer

Abstract: A method of using a quadrupole ion trap mass spectrometer for high resolution mass spectroscopy is disclosed High resolution of a mass spectrum of a desired species is achieved by first using a slow scanning rate and by first ridding the trap of unwanted ions Accurate mass calibration is achieved by using a reference compound of known mass and using a second supplemental AC dipole voltage to eject the reference ions at nearly the same time as the sample ions of interest are ejected from the trap This eliminates the need to scan the trap between the masses of the sample and reference ions Space charge in the trap is held constant, thereby eliminating a major source of mass axis instability, by using the results of one scan to control the ionization time during the next scan Preferably, during ionization a broadband supplemental dipole voltage is applied to the ion trap to rid it of unwanted ions During a portion of the ionization time the broadband signal is constructed to retain only sample ions in the ion trap, and during the remainder of the ionization time the broadband signal is constructed to retain both sample and reference ions in the ion trap By adjusting the relative lengths of the two portions of the ionization time the total space charge in the ion trap can be held constant notwithstanding variations in sample ion concentration

Radiotherapy apparatus equipped with low dose localizing and portal imaging X-ray source

Abstract: Apparatus equipped for both megavoltage radiotherapy and a diagnostic X-ray source for portal imaging Both the high energy therapeutic and low energy diagnostic source of radiation are physically located at the same point in apparatus space, and utilize a single moveable target converter that is physically positioned according to the desired use, either therapy or diagnostics

Clamp with wafer release for semiconductor wafer processing equipment

Abstract: An apparatus for releasably clamping a substrate to a support platform, or other support system, at a face of the substrate is described. In one embodiment, a retractable clamp holds a substrate near its edges on a support platform when the clamp is in its fully extended position. One or more leaf springs are mounted to the clamp and apply force to the substrate at respective points in the event the substrate adheres to the clamp, thereby releasing the substrate from the clamp. In a preferred embodiment of the present invention, one or more activators are positioned in cooperative relationship to the leaf springs to cause the leaf springs to retract into recesses in the clamp when the clamp is extended against the substrate. In their retracted position, the leaf springs do not contact the substrate so as to minimize the generation of particle contamination and the chance of the release leaf springs themselves adhering to the substrate.

Atomic-layer engineering of cuprate superconductors

Abstract: A technique for atomic layer-by-layer synthesis of cuprate superconductors and other complex oxides has been developed. Thin films with excellent transport properties and atomically flat surfaces and interfaces are obtained. The samples are engineered by stacking molecular layers of different compounds to assemble multilayers and superlattices, by adding or omitting atomic monolayers to create novel compounds, and by doping within specified atomic monolayers to fabricate, for the first time, intra-cell barriers. Apart from manufacturing trilayer Josephson junctions withI cRn>5 mV, this technique enables one to customize both the materials and the devices according to the needs of a specific experiment. A number of fundamental issues, such as the dimensionality of the HTSC state, existence of long-range proximity effects, occurrence of resonant tunneling with a specified number of hops, etc., have been addressed in this way. Synthesis of the first “artificial” metastable HTSC compounds is also reported.

Superconducting oxide multilayers and superlattices: Physics, chemistry, and nanoengineering

Abstract: A technique has been developed for synthesis of heterostructures containing various Bi- and Dy-based cuprates and other complex oxides, with a high level of control of deposition of individual atomic monolayers as well as capability for atomic-layer engineering. It produces multilayers and superlattices which display striking long-range crystalline order and atomically abrupt interfaces; this enables deposition of one-unit-cell thick 2212 layers which display HTSC, and of barriers less than 1 nm thick with no pinholes over macroscopic areas. Employing Dy-doped 1278 barriers, trilayer Josephson junctions with I c R n =5−7 mV have been fabricated. Phase locking is seen in stacked junctions. Tunneling transport (but no supercurrent) is observed in junctions with insulating titanate barriers. Modulation doping is attained by omitting or inserting entire monolayers, and artificial metastable high-T c compounds have been synthesized in this way. Finally, long-range proximity effects are seen in 2212-2201-2212 trilayers.

Plasma etch equipment

Abstract: A microwave powered electron cyclotron resonance reactor employing a low pressure, high electron density plasma for rapid oxide etching using hydrogen and argon incorporates an alumina-coated quartz dielectric microwave window to couple microwave energy into an etch chamber while preventing oxygen in the window from contaminating the etch chamber or its contents. The etch chamber side of the dielectric microwave window is coated with alumina.

Ion trap mass spectrometer method and apparatus for improved sensitivity

Abstract: An ion trap mass spectrometer system providing superposition of an AC dipole and/or monopole field on the quadrupole field to provide one preferential ejection direction.

Method for controlling a collimated sputtering source

Abstract: A method for automatically controlling a collimated sputtering source that is controllable by a computer to compensate for the build-up of sputtered material on the collimator. The method involves providing software for the computer including a formula to calculate a multiplier as a function of the age of the collimator, sequentially depositing film on a series of substrates using the sputtering source, monitoring the age of the collimator, and using the software to periodically adjust the value of a controllable sputtering parameter as a function of the multiplier. The sputtering parameter is automatically adjusted by the software such that a property of the film deposited by the source on the series of substrates does not substantially vary among the substrates as sputtered material builds up on the collimator.

Usability testing in the field: bringing the laboratory to the user

Abstract: Usability testing is not always best accomplished within the confines of a specially equipped usability laboratory. Logistics and resource constraints sometimes necessitate taking the testing out on the road. Field testing provides an opportunity to sample from a distributed customer base . . a requirement of significant relevance when competing in a global market. What’s more, usability testing in the field can offer benefits in both marketing and public relations that in-house testing may miss. This paper describes some of the issues surrounding a field testing program, and gives suggestions about how such an undertaking can be accomplished under strict financial, resource and schedule limitations. A case study is presented to help illustrate the planning and evaluation process, and to provide insights into the types of problems such an endeavor is likely to encounter, as well as some valuable lessons learned along the way.

Method of space charge control for improved ion isolation in an ion trap mass spectrometer by dynamically adaptive sampling

Abstract: A method of using a quadrupole ion trap mass spectrometer for high resolution mass spectroscopy is disclosed. In the preferred embodiment, the space charge in the ion trap is controlled to high accuracy. This is done by using a prescan of the trap before each analytical scan, where the ionization parameters used in the prescan are not fixed, but rather are based on the previous analytical scan. The method is especially useful in connection with performance of high resolution MS/MS experiments of the type described in the inventor's prior U.S. Pat. No. 5,198,665.

Anisotropic pyrolytic graphite heater

Abstract: A heater for an indirectly heated vacuum tube cathode is formed of anisotropic pyrolytic graphite in which current passes through the graphite in the "c" direction.

Phase locking of two long-pulse, high-power magnetrons

Abstract: We have phase locked a pair of long-pulse, high-power, secondary-emission magnetrons to an RF-isolated low-power driver via a waveguide directional coupler. With the 3 dB hybrid coupler, the peak and average power sent back towards the driver were lower than the total power by factors of 20 and 100, respectively. A dual-channel, thyratron-switched line-type modulator was used to power the magnetrons in parallel. In this experiment the total microwave power from the pair of phase-locked high-power magnetrons was limited to 48 MW for 700 ns pulses and 46 MW for 900 ns pulses because one of the high-power magnetrons would only operate at or below half power. Experimental results from this repetitively-pulsed (10 Hz) phase-locked magnetron pair are presented which show excellent phase stability of several degrees both during the pulse and from pulse-to-pulse. >

X-ray tube noise and vibration reduction

Abstract: An X-ray tube construction of the rotating anode type for reducing acoustic noise and vibration by using granules (20) which are placed loosely within an anode cavity formed between the outer surface (26) of an anode shank (25) and a wall (27) of an anode sleeve in proximity to a bearing (24) journaled to a rotor shaft (23) for rotation of an anode structure (22).

Measurements ofH c2(T) in Bi-Sr-Cu-O

Abstract: Hc2(T) has been measured for thin BSCO films at temperatures down to 65 mK and pulsed fields up to 35 T.Hc2(T) diverged anomalously as the temperature decreased. At the lowest temperature, it was five times that expected for a conventional superconductor.

Non-centric improved pumping stage for turbomolecular pumps

Abstract: The present invention refers to a pumping stage particularly designed for turbomolecular pumps, having increased compression ratio, and capable of extending the operating range of the turbomolecular pump towards high pressure. The new pumping stage comprises a casing housing, a rotor disk, and a substantially coplanar stator ring. The stator ring consists of two plates connected with each other along their circumferential periphery, thereby defining a region of close tolerance with the opposite surfaces of the rotor. The rotor and stator cooperate to define a tapered, free annular channel having a suction port and a discharge port at the opposite ends of this channel. The channel tapers in a functional, predetermined fashion, having the largest cross-sectional area near the suction port, and converging, according to the rotational direction of the rotor, at the discharge port.

Method and structure for reducing short circuits between overlapping conductors

Abstract: Method and apparatus for reducing current leakage between overlapping conductive structures in a multi-layered integrated circuit device such as a thin film capacitor is described. A conductive structure operating as a raised lower electrode is preferably fashioned by step-like erosion using a photolithographic techniques atop a dielectric substrate. In accordance with this invention, the dielectric substrate itself is allowed to erode as well to space the conductive structure away from the problemmatic inner corners of the step. By so distancing such conductive structures, like electrodes, from these inside corners, even conventional deposition techniques can be used to fabricate a capacitive device of operational tolerance suitable for DRAM application without risk of unwanted electrode current leakage and possible shorting. By so separating, the capacitance of the device can be reliably increased by increasing the available three dimensional capacitor area and decreasing the film thickness rather than relying primarily on high permittivity dielectrics.

Tunable RF probe for use in NMR spectroscopy experiments and method of tuning.

Abstract: of EP0579473A tunable element of an RF resonant circuit in an NMR RF probe including: an inner conductor having a variable length and a first and second end; a movable contact strip at the second end; and the inner conductor electrically connected to an outer grounded conductor via the contact strip. A tunable element, which has an electrical length with a first and second end, including: components for varying the electrical length; the second end connected to near ground; and a matching element electrically connected to the tunable element between the first and second ends. An NMR RF probe having: an RF terminal, a sample coil, and an RF resonant circuit with a matching element electrically connected to a tunable element between a top and bottom end of the tunable element. The tunable element's electrical length can be varied. Furthermore, a method for tuning and matching an RF resonant circuit of an NMR RF probe is described.

Effect of electron cyclotron resonance H/sup +/, Ne/sup +/, Ar/sup +/, and Xe/sup +/ plasma precleaning on titanium silicide formation

Abstract: A vacuum integrated cluster tool process incorporating electron cyclotron resonance plasma cleaning, Ti sputter deposition, and rapid thermal annealing in N/sub 2/ is used to form a TiN/sub x 150 eV Ne/sup +/ promotes silicidation, thereby minimizing nitride thickness. The effects of precleaning are significant as the activation energy for TiSi/sub y/ formation is reduced from 1.8 eV characteristic of a BOE cleaned surface to 1.2 eV on Si etched with 250 eV Ne/sup +/. Mechanistically, the silicide kinetics are shown to be inhibited by the presence of a thin amorphous layer that is formed only when cleaning Si with Ar/sup +/ and Xe/sup +/ with the effect that both knock-on oxygen atoms and implanted noble gas atoms trapped within the amorphous layer retard the requisite solid-phase epitaxial regrowth kinetics. Recrystallizing the amorphous Si surface prior to metallization appears to restore the near-normal silicide kinetics that is characteristic of Ne/sup +/ cleaning. >

Wafer retaining platen and lifting means

Abstract: An apparatus for releasably holding a workpiece in semiconductor processing systems such as a batch ion implanter which comprises a linkage mechanism mounted onto the backside of a platen for clamping a wafer (2) against a fence (1A) of a supporting means (1) and a pusher means (11) mounted on a wafer lift means (13) for engagement with a lever mechanism (5, 6, 7, 9, 10, 15) for locking and unlocking the device, and sensing any misclamp of the workpiece.

Ion trap mass spectrometer

Abstract: An ion trap mass spectrometer system providing superposition of an AC dipole and/or monopole field on the quadrupole field to provide one preferential ejection direction.

Microanalytical study of defect formation in thin bismuth strontium calcium copper oxide films

Abstract: Thin bismuth strontium calcium copper oxide (BSCCO) films and BSCCO/insulator/BSCCO trilayers have been prepared on SrTiO 3 and MgO substrates by evaporation from elemental sources in ozone atmosphere. Accurate control of the stoichiometry is achieved through monitoring of the atomic fluxes by use of in situ atomic absorption spectroscopy, as well as by reflection high-energy electron diffraction. Nevertheless, nanometer-scale second- phase precipitates are sometimes observed. These defects and the flat regions around them have been probed by a variety of microanalytical techniques, including Rutherford backscattering spectroscopy, particle-induced x-ray emission, atomic force microscopy, microscopic secondary ion mass spectroscopy and transmission electron microscopy.

The RF system of a typical clinical linear accelerator

Abstract: The author describes the RF system of a typical clinical linear accelerator used for radiotherapy purposes. Having worked on the Varian Clinac 2100 (CL2100) series and its predecessors for several years, he chooses it as typical. It is a very complex electromechanical device weighing over 10 tons and capable of being serviced by a moderately trained technician. The CL2100 is a klystron driven machine, but there are few differences between these and magnetron driven systems (CL600) series. >

The Klystrode® IOT a New, Compact, High Efficiency Electron Tube

Abstract: The Klystrode® (IOT) is a new high power electron tube which combines the features of Klystron and the Tetrode. During the past six years it has virtually taken over the UHF-TV market and has demonstrated its capabilities in high power research applications. This paper describes the principles of Klystrode IOT operation and the power and frequency ranges where it is most useful. Field experience with over fifty (50) transmitters in UHF TV service is reported as well as test results from high power scientific devices operated at 267 MHz, 250 kW (CW) and 425 MHz, 500 kW (pulse). Finally, future improvements in the Klystrode IOT to reduce cost, improve efficiency and optimize the tube for industrial applications.

Apparatus for detection of leaks

Abstract: of EP0632258A non-helium expansion leak test technique is used to detect large leaks in a test part. The technique does not require the presence of helium or any other trace gas in the part being tested. The non-helium expansion technique is preferably used in conjunction with a helium mass spectrometer leak detector to permit leak detection over a large range of leak rates. A test part is placed in a sealed test fixture, and a valve between the test fixture and an expansion chamber is opened. The pressure in the expansion chamber is measured after the valve is opened. When the measured pressure is less than a reference pressure, a sealed part is indicated. When the measured pressure is greater than the reference pressure, a leaking test part is indicated. When a sealed test part is indicated, a helium mass spectrometer leak test is performed to determine the presence of small leaks in the test part. An atmospheric gross leak test can be performed simultaneously with the non-helium expansion leak test to detect large leaks in situations where some helium remains in the test part at the time of test.

Tangential flow pumping channel for turbomolecular pumps

Abstract: The present invention relates to turbomolecular pumps comprising one or more tangential flow pumping stages in addition to axial flow pumping stages, so as to raise the pump exhaust pressure up to the atmospheric pressure, wherein at least one tangential flow pumping stage having a tangential flow pumping channel of improved design. The channel is located between the lateral surface of the rotor disk and the annular inner wall of stator and comprises an upper closure plate provided with suction port and a lower closure plate provided with diskharge port wherein these ports operably coupled to the tangential flow pumping channel. The cross-section area of the channel is enlarged from its periphery portion defined by the lateral surface of the rotor disk to a central portion defined by the upper and lower closure plates.

Recent developments for trace vapor detection

Abstract: A transmission quadrupole mass spectrometer has been incorporated in an integrated trace vapor detection system. The system includes high performance sample acquisition and inlet provisions to maximize detectability at very low levels. To characterize performance credibly, a precision sample generator with a down stream switching capability at levels below part per billion has been constructed. Construction and operation is reported.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.