Showing papers on "Chamber pressure published in 1988"

CVD of silicon oxide using TEOS decomposition and in-situ planarization process

Abstract: A high pressure, high throughput, single wafer, semiconductor processing reactor is disclosed which is capable of thermal CVD, plasma-enhanced CVD, plasma-assisted etchback, plasma self-cleaning, and deposition topography modification by sputtering, either separately or as part of in-situ multiple step processing. A low temperature CVD process for forming a highly conformal layer of silicon dioxide is also disclosed. The process uses very high chamber pressure and low temperature, and TEOS and ozone reactants. The low temperature CVD silicon dioxide deposition step is particularly useful for planarizing underlying stepped dielectric layers, either along or in conjunction with a subsequent isotropic etch. A preferred in-situ multiple-step process for forming a planarized silicon dioxide layer uses (1) high rate silicon dioxide deposition at a low temperature and high pressure followed by (2) the deposition of the conformal silicon dioxide layer also at high pressure and low temperature, followed by (3) a high rate isotropic etch, preferably at low temperature and high pressure in the same reactor used for the two oxide deposition steps. Various combinations of the steps are disclosed for different applications, as is a preferred reactor self-cleaning step.

Process for PECVD of silicon oxide using TEOS decomposition

Abstract: A high pressure, high throughput, single wafer, semiconductor processing reactor is disclosed which is capable of thermal CVD, plasma-enhanced CVD, plasma-assisted etchback, plasma self-cleaning, and deposition topography modification by sputtering, either separately or as part of in-situ multiple step processing. The reactor includes cooperating arrays of interdigitated susceptor and wafer support fingers which collectively remove the wafer from a robot transfer blade and position the wafer with variable, controlled, close parallel spacing between the wafer and the chamber gas inlet manifold, then return the wafer to the blade. A combined RF/gas feed-through device protects against process gas leaks and applies RF energy to the gas inlet manifold without internal breakdown or deposition of the gas. The gas inlet manifold is adapted for providing uniform gas flow over the wafer. Temperature-controlled internal and external manifold surfaces suppress condensation, premature reactions and decomposition and deposition on the external surfaces. The reactor also incorporates a uniform radial pumping gas system which enables uniform reactant gas flow across the wafer and directs purge gas flow downwardly and upwardly toward the periphery of the wafer for sweeping exhaust gases radially away from the wafer to prevent deposition outside the wafer and keep the chamber clean. The reactor provides uniform processing over a wide range of pressures including very high pressures. A low temperature CVD process for forming a highly conformal layer of silicon dioxide is also disclosed. The process uses very high chamber pressure and low temperature, and TEOS and ozone reactants. The low temperature CVD silicon dioxide deposition step is particularly useful for planarizing underlying stepped dielectric layers, either alone or in conjunction with a subsequent isotropic etch. A preferred in-situ multiple-step process for forming a planarized silicon dioxide layer uses (1) high rate silicon dioxide deposition at a low temperature and high pressure followed by (2) the deposition of the conformal silicon dioxide layer also at high pressure and low temperature, followed by (3) a high rate isotropic etch, preferably at low temperature and high pressure in the same reactor used for the two oxide deposition steps. Various combinations of the steps are disclosed for different applications, as is a preferred reactor self-cleaning step.

Method and apparatus for making gas flushed packages

Abstract: A method and apparatus for making gas flushed packages in a vacuum chamber machine which includes a bag mouth clamp spaced apart form seal bars disposed to transversely seal the bag neck. A vertically moveable piercing blade and nozzle penetrate the upper wall of the bag neck as the chamber pressure is lowered and the bag "balloons" thereby causing the upper and lower neck walls to separate. Once the bag is pierced and the residual air escapes, a predetermined amount of gas is injected and then the bag is sealed. If desired, sufficient gas can be injected to make a pillow pack.

Ion-beam sputtering apparatus for deposition of multilayered films

Abstract: Multilayered films are,composed of repeated alternate deposition of ultrathin layers of different materials. These films are of interest for their unique properties not intrisically found in conventional monolithic substances. Multilayered films have been prepared by several methods: molecular beam epitaxy [1], thermal evaporation [2, 3], chemical vapour deposition [4], and sputtering [5-7]. In an attempt to deposit thin films of tin oxide, we used an ion-beam sputtering (IBS) apparatus with a simplified accelerator system [8]. The IBS method is particularly attractive for deposition because a high-purity thin film with an improved adhesion to the substrate can be obtained. In the present letter we describe the construction of the IBS apparatus specially designed for the synthesis of multilayered films. The constructed apparatus is simple, relatively inexpensive and convenient to control. The results of analysing periodic structures of Pt/SnOx multilayers deposited by this apparatus are also presented. The outline of the apparatus used to prepare multilayered films is shown in Fig. 1. The vacuum chamber is a vertical cylinder, 40 cm in diameter and 80 cm tall, of which only the upper-half is actually used. The base pressure is below 1 x 10 5 torr. Argon gas of 99.9995% purity is fed into the ionsource chamber and the chamber pressure during the run is maintained at (1 + 0.1) x 10 4torr. The target is placed at about 45 ° to both the axis of the beam and the substrate. The distance from the centre of the target to the ion-source chamber and to the substrate is 3.5 and 5 cm, respectively. The target assembly can contain four different targets and the targets are screwed to the aluminium target-holders of 8-cm diameter. In this experiment two targets, platinum foils and a sintered tin oxide disc, were used. The rotation of the targets was carried out using an ordinary stepping motor (Oriental motor, PH266-01) in the vacuum chamber. Generally the vacuum hinders the rapid heat transfer, thus heat tends to accumulate in the running motor and augments its temperature. To avoid this temperature increase of the stepping motor, the motor is mounted on a water-cooled copper plate; flexible hoses are used to conduct the cooling water. Although the placing of the stepping motor in the vacuum chamber induces a possible contamination from the gaseous species from the organic materials in the motor, it makes the overall design of the apparatus very simple. A microcomputer (NEC, PC-8801) and a driver/controller (Cosmotron, PMC-14C) together with the stepping motor control the rotation of the targets. When the sputtering time to form a layer reaches a preset value, the control system turns the target assembly by 90 ° to the other target. It takes about 1 sec for this rotation. The substrate assembly contains eight different substrate holders that can be selected manually via a d.c. motor. The shutter has a window (2 c m x 4 cm) through which sputtered particles deposite on a designated substrate. During the pre-sputtering of the targets, the window is closed. The substrate-shutter separation is held at 4 mm so that all particles passing through the window hit the planned substrate, thus contamination of other substrates by the sputtered particles is avoided. The electrical connections for the system are shown schematically in Fig. 2. It is similar to that used in our previous experiment [8], however the stability of the discharge current increased markedly by employing a d.c. current supply (Metronix, 411A-32) and an insulation transformer instead of a voltage slider. The electrical system is run typically at a discharge voltage of 50 V, a discharge current of 600 mA, a beam voltage of 1000 V, an accelerator voltage of 150 V and an ionbeam current (defined here as the current between the target and the ground) of 0.8 mA. The temperatures of the substrate and the target reached 90 and 130°C, respectively after 3h; they were measured by a CA-thermocouple during the sputtering of an

Pressure build-up at the metal delivery tube orifice in ultrasonic gas atomization

Abstract: The effects of geometry (diameter and tip design) and position (relative to the gas nozzles) of the metal delivery tube in an ultrasonic gas atomization (USGA) device on the pressure condition in the gas-metal interaction zone at the tube orifice have been studied. Simulation of ultrasonic gas (argon or nitrogen) atomization has been conducted, both at low (3.5 to 14 atm) and high (15 to 75 atm) atomization pressures. Low gas atomization pressures are generally used in spray deposition processes such as liquid dynamic compaction (LDC), while high pressures are used for powder production. Depending on the experimental conditions, i.e. the shape and angle of the taper at the metal delivery tube orifice or its position with respect to the nozzles' gas exit common plane, either partial vacuum (equivalent to downward aspiration of the melt) or overpressures (equivalent to back-pressurization of the melt) at the metal delivery tube was detected. Underpressure and overpressure effects were found to increase with gas atomization pressure. The maximum pressure differences measured with respect to the atomization chamber pressure were about 0.15 to 0.25 atm for the low-pressure experiments, and 0.50 to 0.60 atm for the high-pressure experiments. Underpressures or overpressures of these magnitudes have a large effect on the metal flow rate during gas atomization, either enhancing or reducing it, and thus changing significantly the gas to metal flow ratio. Because this is a crucial parameter for both the USGA and the LDC processes, the state of pressure at the delivery tube's orifice has to be monitored carefully, in order to ensure optimal processing conditions.

Effect of chamber pressure on particle velocities in low pressure plasma spray deposition

Abstract: A laser velocimeter has been used to measure spray particle velocities in a low pressure plasma spray system at chamber pressures ranging from 6.7 to 80 kPa (50 to 600 Torr). For Al2O3 spray powder with a mean diameter of 44 μm, peak particle velocities were of the order of 200 – 400 m s-1. The measured velocity distributions were strongly dependent upon spray chamber pressure, with the highest particle velocities at intermediate pressures of about 40 kPa (300 Torr). Particle velocities predicted with a simple analytical model are in reasonable agreement with experimental results close to the spray gun, where drag due to chamber gases can be neglected. This simple model also correctly predicts a particle velocity maximum at 45 kPa (340 Torr).

Optimizing poly(chloro-p xylylene) or Parylene C synthesis

Abstract: Current interest for implantable insulating biomaterials has resurrected a class of polymers synthesized from p-xylylene and its derivative dimers. Important kinetic aspects for the synthesis of the polymer are derived from measurements of chamber pressure and total weight of film deposition. Reduction of peak chamber pressure during polymer deposition was found to improve film quality, uniformity of deposit, adhesion, and transparency. A low-cost reactor design is proposed which simplifies the deposition characterization steps needed for producing high quality films.

Simplified multicolor fluid system for continuous ink jet printer

Abstract: An improved construction for a continuous ink jet printing system of the kind having a chamber for receiving a plurality of ink cartridges, a plurality of ink supply sub-systems for delivering ink from the cartridges to respective print heads and a plurality of ink return sub-systems for returning ink from the print heads to respective cartridges. The cartridge chamber is constructed to be substantially air-tight and the ink cartridges have a vent opening to their interior. The chamber itself is coupled to a vacuum source and the cartridges in the chamber are maintained at the chamber pressure via their vent openings. The chamber evacuating source includes a source of compressed air and a venturi devcie coupled to the housing interior and the compressed air source. The compressed air source also can be coupled, via check valves structure, to provide drying air to the print heads.

Two-cycle engine

Abstract: PURPOSE:To allow the fuel injection function of a two-cycle engine to operate at optimum efficiency by furnishing a control means to control the injection timing and amount of fuel injection valves arranged on a main and an aux. suction passage. CONSTITUTION:Besides a main suction passage 22 to introduce new air into a crank chamber 21, the two-cycle engine 10 is equipped with an aux. suction passage 30 to introduce new air directly into the crank chamber 21. In this engine 10, No.1 injector 34 and No.2 injector 36 are arranged on these suction passages 22 and 30, respectively. A crank chamber pressure signal from a pressure sensor 50 and signals from a crank sensor 52 and pulser coil 56 are fed into a central processing unit 54, which judges cylinder on the basis of these signals and determines optimum fuel injection timing and injection amount about the injectors 34, 36, and applicable signal is sent. Because the injectors 34, 36 can thus work with optimum injection timing and injection amount through electronical control, effective output can be drawn out of the engine 10.

Boundary layer development as a function of chamber pressure in the NASA Lewis 1030:1 area ratio rocket nozzle

Abstract: Through the use of theoretical predictions of fluid properties and experimental heat transfer and thrust measurements, the zones of laminar, transitional, and turbulent boundary layer flow were defined for the NASA Lewis 1030:1 area ratio rocket nozzle. Tests were performed on the nozzle at chamber pressures from 350 to 100 psia. For these conditions, the throat diameter Reynolds numbers varied from 300,000 to 1 million. The propellants used were gaseous hydrogen and gaseous oxygen. Thrust measurements and nozzle outer wall temperature measurements were taken during the 3-sec test runs. Comparison of experimental heat transfer and thrust data with the corresponding predictions from the Two-Dimensional Kinetics (TDK) nozzle analysis program indicated laminar flow in the nozzle at a throat diameter Reynolds number of 320,000 or chamber pressure of 360 psia. Comparison of experimental and predicted heat transfer data indicated transitional flow up to and including a chamber pressure of 1000 psia. Predicted values of the axisymmetric acceleration parameter within the convergent and divergent nozzle were consistent with the above results. Based upon an extrapolation of the heat transfer data and predicted distributions of the axisymmetric acceleration parameter, transitional flow was predicted up to a throat diameter Reynolds number of 220,000 or 2600-psia chamber pressure. Above 2600-psia chamber pressure, fully developed turbulent flow was predicted.

Discussion of Primary Drying during Lyophilization

Abstract: This paper examines, by means of an ideal model, the controlling mechanisms invoiced in the primary drying of the lyophilization process. With the aid of the model, the effect of temperature and desorption energy on the fraction of water molecules on the surface of the “disorder” layer, at any one instant, that have sufficient energy to leave the surface is examined. It is shown that the effect of an increase in chamber pressure, while maintaining the shelf-surface temperature, is to cause an increase in the product temperature which results in a decrease in the unit sublimation rate. Experimental data is presented to show that a significant sublimation rate can only occur when chamber pressure falls below the initial vapor pressure of the ice. The sublimation rate is shown to be best estimated from a knowledge of the heat flux (q) and the heal of sublimation.

Steering force control device for power steering device

Abstract: PURPOSE:To maintain a steering force constant by controlling a reaction force chamber pressure approximately constant by suppressing a rise in a differential pressure by increasing the throtting area of an orifice when the differential pressure rises beyond a specified pressure due to increase in a pump rpm CONSTITUTION:When a delivery flow rate Q increases due to a rise in a pump rpm, a differential pressure DELTAP(P-P1) between front and back of a fixed orifice 65 of an orifice 61 for detecting rpm increases Accordingly, under a condition of a low vehicle speed, the pump rpm is low and the differential pressure is small and therefore a low differential pressure DELTAP produced between the fixed orifice 65 and a metering orifice 70 of a flow rate control valve 69 acts on a plunger 54 And when an input shaft is rotated by operating a steering wheel, the plunger 54 is readily pushed This causes a sleeve valve member 32 and a rotary valve member 31 to produce relative rotation When the vehicle speeds increase, DELTAP increases, a differential pressure introduced into reaction force chambers 55a and 55b increases, and the pressing force of the plunger 54 against a projection 50 increases

Ground Testing for Base-Burn Projectile Systems

Abstract: : A ground test spin fixture was used to obtain measurements in the base region of a 155mm M864 projectile. The M864 uses the base burn concept of reducing base drag by injecting gas, generated b burning propellant, into the base area. Pressure and temperature measurements were obtained in the base area of the projectile, with the base burn active, at spin rates up to 250 rps. Data illustrate that increased spin rate increases the pressure in the propellant chamber and increases substantially the burning rate of the propellant . The ground tests provided information on measurement techniques which will be used in free-flight experiments. Base burn, Ignition, Spin fixture, Projectiles, Chamber pressure.

Measurement of tip penetration of confined high-density transient jets by laser beam deflection

Abstract: The penetration of high density transient jets injected into a quiescent chamber containing air at atmospheric temperature and various pressures has been measured in terms of laser beam deflection. The sensitivity of the technique is quantified and the rate of jet penetration shown to increase with jet to chamber density ratio, decrease with chamber pressure and vary with downstream distance from the nozzle.

Apparatus for chemically generating and dispersing gas

Abstract: A gas generator chemically generates a gas from a chemical reaction between two reagents (Ra,RB) contained within a common container. The reagents are normally separated by a gas generation chamber (Gb) into different regions of the container in the absence of gas generation therein. A reference pressure source (GA) of a predetermined pressure forces the two reagents into contact with each other when the pressure of gas in the gas generation chamber is less than the predetermined pressure. A valve (V) in fluid communication with the gas generation chamber (GB) is provided to withdraw the generated gas from the chamber when OPEN. As the gas flows through the valve from the chamber the gas pressure in the chamber drops permitting more mixing of the reagents. When the chamber pressure becomes equal to or higher than the predetermined pressure applied by the reference pressure source, the reagents become separated again and gas generation ceases.

Computational design of an experimental laser-powered thruster

Abstract: An extensive numerical experiment, using the developed computer code, was conducted to design an optimized laser-sustained hydrogen plasma thruster. The plasma was sustained using a 30 kW CO2 laser beam operated at 10.6 micrometers focused inside the thruster. The adopted physical model considers two-dimensional compressible Navier-Stokes equations coupled with the laser power absorption process, geometric ray tracing for the laser beam, and the thermodynamically equilibrium (LTE) assumption for the plasma thermophysical and optical properties. A pressure based Navier-Stokes solver using body-fitted coordinate was used to calculate the laser-supported rocket flow which consists of both recirculating and transonic flow regions. The computer code was used to study the behavior of laser-sustained plasmas within a pipe over a wide range of forced convection and optical arrangements before it was applied to the thruster design, and these theoretical calculations agree well with existing experimental results. Several different throat size thrusters operated at 150 and 300 kPa chamber pressure were evaluated in the numerical experiment. It is found that the thruster performance (vacuum specific impulse) is highly dependent on the operating conditions, and that an adequately designed laser-supported thruster can have a specific impulse around 1500 sec. The heat loading on the wall of the calculated thrusters were also estimated, and it is comparable to heat loading on the conventional chemical rocket. It was also found that the specific impulse of the calculated thrusters can be reduced by 200 secs due to the finite chemical reaction rate.

Three dimensional thermal analysis of rocket thrust chambers

Abstract: A numerical model for the three dimensional thermal analysis of rocket thrust chambers and nozzles has been developed. The input to the model consists of the composition of the fuel/oxidant mixture and flow rates, chamber pressure, coolant entrance temperature and pressure, dimensions of the engine, materials and the number of nodes in different parts of the engine. The model allows for temperature variation in three dimensions: axial, radial and circumferential directions and by implementing an iterative scheme, it provides nodal temperature distribution, rates of heat transfer, hot gas and coolant thermal and transport properties.

Hydraulic power steering valve with three-orifice reactive chamber pressure control

Abstract: A power steering system for use in a motor has a pair of reactive pressure chambers in which the opposite ends of a valve spool are exposed, one of the reactive pressure chambers communicating with one fluid-pressure chamber in a reciprocable fluid-pressure cylinder assembly through a first orifice, the other reactive pressure chamber communicating with both fluid-pressure chambers in the cylinder assembly through second and third orifices, respectively. The first, second and third orifices are the first and second orifices are defined in the valve spool. A third passage define by a space between the spool and the valve cylinder communicates the first and third orifices.

Orbital transfer vehicle 3000 LBF thrust chamber assembly hot fire test program

Abstract: The Aerojet Orbital Transfer Vehicle (OTV) Thrust Chamber Assembly (TCA) concept consists of a hydrogen cooled chamber, and annular injector, and an oxygen cooled centerbody. The hot fire testing of a heat sink version of the chamber with only the throat section using hydrogen cooling is documented. Hydraulic performance of the injector and cooled throat were verified by water flow testing prior to TCA assembly. The cooled throat was proof tested to 3000 psia to verify the integrity of the codeposited EF nickel-cobalt closeout. The first set of hot fire tests were conducted with a heat sink throat to obtain heat flux information. After demonstration of acceptable heat fluxes, the heat sink throat was replaced with the LH2 cooled throat section. Fourteen tests were conducted with a heat sink chamber and throat at chamber pressures of 85 to 359 psia. The injector face was modified at this time to add more face coolant flow. Ten tests were then conducted at chamber pressures of 197 to 620 psia. Actual heat fluxes at the higher chamber pressure range were 23 percent higher than the average of 10 Btu/in 2 predicted.

Effects of Interface Configurations on Pressure Waves in Guns

Abstract: : Improper ignition of a gun or howitzer propelling charge can lead to potentially damaging pressure waves, threatening both integrity of the weapon system and safety of the operating crew. High levels of pressure waves are often accompanied by ballistic variability, increases in chamber pressure and, on occasion, can lead to breechblows, fuze malfunctions, projectile prematures, and fin damage. While weapons firing low performance charges can usually sustain a fairly high level of pressure waves with no adverse effects, the higher pressure environment associated with most high performance charges appears to aggravate the situation, with moderate levels of pressure waves sometimes escalating into major problems. In this study, test projectiles were fabricated with both conical and cylindrical bases. Firings were conducted in a highly instrumented 105-mm, M68 tank gun, and detailed analysis of pressure-time and pressure difference-time data was conducted to assess the influence of base configuration on the formation of pressure waves and their measurement. Representative data are presented and discussed in detail. Keywords: Interior ballistics; Projectile geometry.

Evaluation and Improvement of Liquid Propellant Rocket Chugging Analysis Techniques. Part 2: a Study of Low Frequency Combustion Instability in Rocket Engine Preburners Using a Heterogeneous Stirred Tank Reactor Model

Abstract: During the shutdown of the space shuttle main engine, oxygen flow is shut off from the fuel preburner and helium is used to push the residual oxygen into the combustion chamber. During this process a low frequency combustion instability, or chug, occurs. This chug has resulted in damage to the engine's augmented spark igniter due to backflow of the contents of the preburner combustion chamber into the oxidizer feed system. To determine possible causes and fixes for the chug, the fuel preburner was modeled as a heterogeneous stirred tank combustion chamber, a variable mass flow rate oxidizer feed system, a constant mass flow rate fuel feed system and an exit turbine. Within the combustion chamber gases were assumed perfectly mixed. To account for liquid in the combustion chamber, a uniform droplet distribution was assumed to exist in the chamber, with mean droplet diameter determined from an empirical relation. A computer program was written to integrate the resulting differential equations. Because chamber contents were assumed perfectly mixed, the fuel preburner model erroneously predicted that combustion would not take place during shutdown. The combustion rate model was modified to assume that all liquid oxygen that vaporized instantaneously combusted with fuel. Using this combustion model, the effect of engine parameters on chamber pressure oscillations during the SSME shutdown was calculated.