Showing papers by "Varian Associates published in 1984"

Regulated dc to dc converter

Abstract: A DC-DC converter includes first and second switches to be opened and closed at mutually exclusive times at a predetermined frequency. The first switch is connected to an inductor and a transformer primary winding so that a first current component from a DC input supply flows through it via the inductor. A second current component having a sinusoid component flows through the first switch in response to discharge of energy stored in a resonant circuit coupled to the transformer. The second component begins approximately simultaneously with closure of the first switch. The second switch, when closed, is connected so that a bidirectional current component flows through it in response to energy stored in the inductor. The rectifier is connected between the secondary winding and the load so the secondary winding supplies substantial current to the load.

Method for gas-assisted, solid-to-solid thermal transfer with a semiconductor wafer

Abstract: Apparatus and method are provided for effecting gas-assisted, solid-to-solid thermal transfer with a semiconductor wafer. A semiconductor wafer is loaded at its periphery onto a shaped platen. Sufficient contact pressure from the loading is produced between the wafer and the platen so that significant gas pressure may be accommodated against the back side of the wafer without having the wafer bow outwardly or break. Gas under pressure is introduced into the microscopic void region between the platen and the wafer. The gas fills the microscopic voids between the platen and semiconductor wafer. The gas pressure approaches that of the preloading contact pressure without any appreciable increase in the wafer-to-platen spacing. Since the gas pressure is significantly increased without any increase in the wafer-to-platen gap, the thermal resistance is reduced and solid-to-solid thermal transfer with gas assistance produces optimum results.

Narrow bore micro-particulate column packing process and product

Abstract: A process for packing narrow bore chromatographic columns and the resulting product are provided. A flexible column, preferably of fused silica, of inner diameter less than 500 μm is selected. A slurry is formed in a reservoir from a mobile solvent and particles of specified diameter. For liquid chromatography the particle size ranges from 3 μm to 10 μm; for gas chromatography the particle size ranges from 3 μm to 100 μm. An end restriction is placed in the end of the column to permit the flow of mobile solvent and to restrict the passage of particles out the end of the column. The reservoir is attached to the column and the slurry is caused to flow under pressure into the column. A two-step pressure sequence is used to first set up the bed of particles and then to compress the bed. First, an initial pressure is maintained for an initial period, preferably less than 10 minutes. Next, the pressure is raised from the initial pressure to a maximum pressure and is maintained at the maximum pressure for a second period. The product in either case is a stable, loose packed column having a high plate number per unit length.

Deformable chuck driven by piezoelectric means

Abstract: A deformable vacuum pin chuck includes a thin silicon chuck for supporting a semiconductor wafer during lithographic processing and a number of piezoelectric transducers for selectively deforming the chuck. Chuck deformation caused by application of electric potentials to selected transducers may be used to correct flatness deviations in the wafer and, thereby, a desired degree of flatness of the semiconductor wafer may be obtained.

Load lock pumping mechanism

Abstract: In a vacuum system for processing workpieces, a vacuum chamber has a workpiece-entrance opening. Load lock means for said entrance opening include a door for sealing the outside of said opening, a movable closure member within the chamber to seal the entrance opening from the interior of the vacuum chamber, and forming a load lock chamber when the door and closure member are both in closed positions. The load lock chamber is connected to a roughing pump and is separately connected to a high vacuum pump through a pumping opening in one or the other of said internal closure member or said door. A large aperture valve is provided in said pumping opening. In one embodiment said pumping opening is connected via suitable conduits and valves to a roughing pump and also to a high vacuum pump. In another embodiment said pumping opening is connected only to the high vacuum pump, and the roughing pump is connected to the load lock chamber via an aperture in the edge of the entrance opening in the processing chamber wall.

Apparatus for controlling thermal transfer in a cyclic vacuum processing system

Abstract: Apparatus for providing thermal transfer between a semiconductor wafer and a heat sink or source in a vacuum processing chamber includes a platen against which the wafer is sealed to define a thermal transfer region therebetween. The platen includes a passage for gas flow between the chamber and the thermal transfer region and a conduit for circulation of a cooling fluid. The platen further includes a fluid-actuated valve responsive to the pressure of the cooling fluid for closing the passage. When the pressure in the chamber reaches a predetermined value, the cooling fluid is turned on and closes the valve. Gas at the predetermined pressure, typically in the range of 0.5 to 100 Torr, is trapped in the thermal transfer region and conducts thermal energy. In a preferred embodiment, a plurality of platens are positioned on a rotating disc in an ion implantation system.

Transfer plate rotation system

Abstract: The system for rotating the transfer plate of a coating system in a vacuum chamber consists of a transfer plate driver assembly on the outside of the chamber at the axis and a transfer plate rotator assembly inside the chamber. The driver assembly consists of a pneumatic actuator for linear motion, a barrel cam which translates the linear motion into rotary motion with high torque at starting and stopping positions, and a rotary feedthrough all in a structural housing. The rotator assembly comprises a central hub with means for supporting the end walls, a transfer plate hub assembly and a ratchet arm connected to the rotary feedthrough. As the pressure plate assembly is drawn back by the ram, it in turn draws back the transfer plate and engages the ratchet arm with the transfer plate hub. The actuator then rotates the transfer plate. The ram then reverses direction, the ratchet arm disengages and is returned to its initial position.

System for igniting and controlling a wafer processing plasma

Abstract: A circuit for impedance matching an RF source to a plasma load comprises an impedance magnitude control shunted with a parallel-resonant tank circuit to provide a phase control. A DC-blocking capacitor and RF filter are used to monitor the self-bias voltage on a workpiece in the plasma. An ignition control is used to provide prompt ignition of the plasma and a rotating magnet is used to stabilize the plasma.

Stabilized microwave power amplifier system.

Abstract: A power amplifier (28) including a Klystron is stabilized against variations in output power with a simplified servo-loop system and cooperating temperature compensation. The system is fully solid-state, digital, and includes an operator-presettable initial power selector, a power output sensor (46), comparator logic (48), variable attenuation responsive to error signals indicative of deviation from the preset power, and temperature compensation means (14), for assured accuracy and stability.

Immobilized antigen-antibody displacement process

Abstract: A method and apparatus for quantitatively analyzing, in a flowing stream, materials in a biological or chemical sample utilizes immobilized antobodies reversibly precharged with fluorescently labeled antigens. The labeled antigens are competitively displaced by unlabeled antigens in the sample, after the sample antigens have been segregated into zones by a chromatographic device, such as the reverse phase high performance liquid chromatograph. Displaced labeled antigens are measured by a fluorescence detector. A plurality of antibody species may be concurrently utilized, thereby allowing quantification of a plurality of antigens from a single sample.

Counterflow leak detector with cold trap

Abstract: A counterflow helium mass spectrometer leak detector includes a test port for receiving a gas sample including the tracer gas helium, a high vacuum pump such as a diffusion pump and a mass spectrometer tuned to detect the helium. The mass spectrometer is coupled to the inlet of the high vacuum pump. The leak detector further includes a cold trap containing liquid nitrogen coupled between the test port and the foreline, or outlet port, of the high vacuum pump. The helium received at the test port passes in reverse, or counterflow, direction through the high vacuum pump to the mass spectrometer. One or more mechanical vacuum pumps insure that the pressure at the foreline of the high vacuum pump is maintained at a prescribed level during a leak test. The cold trap condenses contaminants, water vapor and other gases from the gas sample and prevents backstreaming of oil from mechanical vacuum pumps.

Heating and cooling apparatus for chromatography column

Abstract: A baffle divides a housing into first and second compartments. The first compartment includes a chromatography oven having a fan for circulating heated air over the columns while the oven is closed and for sucking ambient temperature cooling air in the first compartment into the oven while the oven is open. Ambient air is sucked into a tortuous path in the first compartment. Cooling air from the second compartment flows into the first compartment via openings in the baffle. The cooling air flows over the oven exterior and is at least partially sucked into the oven by an oven fan while the oven is open. The oven heater, coaxial with the blades, is located between an oven wall and blades. A ring baffle, having approximately the same diameter as and coaxial with the blades, is located between the wall and the blades. A fan outside of the oven sucks air from the oven through an outlet while the oven is open. The second fan is separated from an inlet for the oven by a baffle having an opening through which air is sucked by the second fan while the oven is closed. The second compartment includes a casing for fluid flow controllers for the columns, which casing is maintained at constant temperature by ambient air sucked around the second compartment.

Three-terminal solar cell circuit

Abstract: Photovoltaic solar cells have improved efficiency when constructed in monolithic form with two different band gap energy junctions. Solar light goes first through an upper layer containing a high band gap energy junction which absorbs the short-wavelength components of light. Then the remaining long-wavelength components are absorbed in a second active layer containing a low band gap energy junction. The cell may comprise p-n-n-p type layers. According to the invention, each low band-gap, low-voltage junction is made to have 1/2 the voltage of the high band-gap high-voltage junctions. The junctions are then connected such that the high-voltage junctions are in parallel and the series connection of low-voltage junctions is also in parallel with them. The junction voltages are invariant so the parallel connection works for any light spectrum.

H2Se “memory effects” upon doping profiles in GaAs grown by metalorganic chemical vapor deposition (MO-CVD)

Abstract: A chemical vapor deposition “memory effect” is the tendency of a source material to adsorb onto the internal walls of the system and subsequently desorb after nominal source shutoff. H2Se, the most common Se transport agent in metalorganic chemical vapor deposition (MOCVD), adsorbs onto stainless steel and glass surfaces. Among the consequences are: graded doping profiles at the end of Se-containing epitaxial layers and the depletion of H2Se gas mixtures with time. By contrast, SiH4, the most common Si transport agent, exhibits negligible memory effect and is recommended as an alternate n-dopant source when memory effects must be entirely eliminated. Capacitance-voltage measurements are used to quantify the extent of the t2Se “memory effect” in GaAs to identify methods for its reduction or elimination, and to distinguish the effects of diffusion and memory upon observed doping profiles. Memory effects are also anticipated when Se is a primary constituent of a semiconductor and H2Se the transport agent.

Solute focusing technique for on-column injection in capillary gas chromatography

Abstract: A solute focusing method is applied to the on-column injection of a liquid sample in gas chromatography so that relatively large sample sizes can be used without causing intolerable column flooding. The injection zone of the column is kept originally at a temperature below the solvent boiling point but the temperature in the adjacent downstream zone is kept higher than the solvent boiling point so that the solvent will evaporate and flow downstream, leaving the solute molecules concentrated within a relatively limited length along the column.

Hydraulic pulse dampener employing stiff diaphragm and nesting member

Abstract: A hydraulic pulse dampener of liquid compressibility type has a flexible tubing wound around a form within a liquid-tight housing filled with a compressibility liquid and a stiff diaphragm placed adjacent a recess formed in a receiving member. As the fluid flowing inside the tubing experiences pressure pulses, the walls of the tubing expand and transmit the pulse energy through the compressibility liquid and causes the diaphragm to gradually flex towards the recess until it may completely nest in it. The recess in the receiving member preferably has a central flat portion so that the flexing diaphragm will first contact the receiving member at the center and the nesting will spread outwardly therefrom.

Transport properties of n-type metalorganic chemical-vapor-deposited Al x Ga 1-x As (0<=x<=0.6)

Abstract: Temperature-dependent measurements in the range 20< or =T< or =600 K have been made on undoped and Si-doped metalorganic chemical-vapor-deposition--grown Al/sub x/Ga/sub 1-x/As (0< or =x< or =0.6) on GaAs. Data obtained from Hall and high-field measurements with the use of the probe technique have been analyzed. The transport parameters in the samples have been obtained from analysis of data and the relative importance of the various scattering mechanisms in different composition ranges have been elucidated. It is found that space-charge scattering plays an important role in limiting electron mobility at 300 K for 0 or =0.4 at 300 K and similar features observed in some samples with x<0.4 at high temperatures have been attributed to electron transfer from the substrate to the epitaxial layers.

Applicateur pour hyperthermie par ultrasons avec coherence variable par focalisation en spirales multiples

Abstract: L'INVENTION CONCERNE LE MATERIEL MEDICAL. UN APPLICATEUR POUR HYPERTHERMIE PAR ULTRASONS COMPREND UN CERTAIN NOMBRE DE TRANSDUCTEURS QU'ON PEUT FAIRE FONCTIONNER EN DIFFERENTS MODES DE GROUPEMENT, DE FACON A DEFINIR UN NOMBRE VARIABLE D'ELEMENTS EMETTEURS 11 QUI EMETTENT DES FAISCEAUX INDIVIDUELLEMENT COHERENTS. CES FAISCEAUX SONT FOCALISES INDIVIDUELLEMENT POUR DONNER LIEU A UNE SUPERPOSITION NON COHERENTE DANS UN PLAN CIBLE 15, CONFORMEMENT A UNE TECHNIQUE DE FOCALISATION EN SPIRALE OU EN SPIRALES MULTIPLES. APPLICATION AU TRAITEMENT DE TUMEURS.

Ball-type vacuum valve for leak detection apparatus

Abstract: In a system for leak detection having many valves, it is desirable to have high vacuum valves operated by solenoids at opposite ends of a diffusion pump in order to isolate the diffusion pump during powr failure or during an intentional shutdown. A valve having a hard spherical ball fitting a vacuum seal and having a spring means to bias the ball in a closed position will close during a power failure. A bell-shaped actuator connected to a solenoid can be used to open the valve with built-in mechanical advantage. A circuit means can be used to supply high starting voltage to the solenoid and then lower voltage to hold the valve open.

Dual filament ion source with improved beam characteristics

Abstract: A Freeman type electron bombardment ion source includes dual filament electrodes positioned in an arc chamber having a slit for extraction of an ion beam. The filament electrodes are symmetrically positioned with respect to the extraction slit. The filament electrode currents are equal in magnitude and oppositely directed. As a result, lateral magnetic fields in the region of the extraction slit are substantially eliminated.

Lens system for acoustic transducer array

Abstract: A lens system for directing and focussing acoustic energy from an array of acoustic transducers on a small target can be made lightweight, low in absorption and dispersion by incorporating plastic Fresnel lenses with prisms into a monolithic tray of the same plastic with one lens for each transducer.

Automatically-insertable case suitable for wire-wound magnetic cores

Abstract: A case for holding a wire-wound magnetic core or other electrical component so that the leads can be automatically inserted on a circuit board which employs a base portion that is shaped and dimensioned for compatibility with conventional automatic insertion equipment. The base includes both plastically-deformable cantilever lead traps for mechanically gripping the leads to secure the component on the base as well as circular notches in the slots that define predetermined positions on the base at which to grip the leads to enable use of the case for automatic insertion.

Monolayer heterointerfaces and thin layers (~10 å) in alxga1-xas-gaas superlattices grown by metalorganic chemical vapour deposition

Abstract: Transmission electron microscopy (TEM) and lattice fringe images are used to show that metalorganic chemical vapour deposition (MOCVD) is capable of growing highly uniform AlxGa1-xAs-GaAs quantum-well heterostructures (QWHs) and superlattices (SLs) with monolayer heterointerfaces and layers as thin as ~10 A.