Effect Of Chamber Pressure Research Articles

Microcrystalline silicon carbon alloy film prepared by photo-chemical vapour deposition

Silicon carbon alloy thin films were prepared by photo-chemical vapour deposition using SiH4 and C2H2 gases, diluted with 97% H2. The effect of chamber pressure on the properties of the film were investigated and are explained from the standpoint of growth mechanism. The 0.4 μm thin film prepared at a pressure of 67 Pa exhibited a dark conductivity of 8.2 × 10−9 S cm−1 along with low optical absorption. The bonded hydrogen content in the film is 6 at.% as estimated from IR spectra. X-ray and electron diffraction study revealed the film to be microcrystalline. The observed crystalline planes are ascribed to crystalline silicon (c-Si), embedded in amorphous silicon carbon (a-SiC:H) tissue. This is also confirmed by the appearance of the TO mode of c-Si at 518 cm−1 in the Raman spectrum. Thus in microcrystalline silicon carbon (μc-SiC) film, the crystallinity is due to silicon alone while carbon is present at grain boundaries and in amorphous regions separating the crystallites. However, the optical absorption of the film is lower than that of μc-Si:H as the absorption is governed by the amorphous part.

REAL-TIME X-RAY RADIOGRAPHY STUDY OF LIQUID JET BREAKUP FROM ROCKET ENGINE COAXIAL INJECTORS

The investigation of liquid jet breakup and spray development is critical to the understanding of combustion phenomena in liquid-propellant rocket engines. A great deal of work has been done to characterize low-speed liquid jet breakup and dilute sprays, but atomizing jets and dense sprays have yielded few quantitative measurements due to their optical opacity. The present work focuses on a characteristic of the primary breakup process of round liquid jets, namely the length of the intact liquid core. The specific application considered is that of shear-coaxial-type rocket engine injectors. Real-time x-ray radiography, capable of imaging through the dense two-phase region surrounding the liquid core, is used to make the measurements. The intact liquid-core length data have been obtained and interpreted to illustrate the effects of chamber pressure (gas density), injected-gas and liquid velocities, and cavitation. The results show clearly that the effect of cavitation must be considered at low chamber pressures since it can be the dominant breakup mechanism. A correlation of intact core length in terms of gas-to-liquid density ratio, liquid jet Reynolds number, and Weber number is suggested. The gas-to-liquid density ratio appears to be the key parameter for aerodynamic shear breakup in this study.

メニエール病聴力に及ぼすチャンバー圧変化の影響

メニエール病聴力に及ぼすチャンバー圧変化の影響

Effects of chamber pressure and accelerating voltage on X-RAY resolution in the ESEM

Chamber pressure, accelerating voltage and working distance have been shown to control the relative diameter of the scattered skirt of the primary electron beam at the specimen surface in the ESEM. Inital x-ray studies indicate that at 3 torr, 30 kV and a WD=15mm, 45% of the beam comes from beyond 25 μm of the incidence point and 4% from beyond 1.5mm. At 5 torr 66% of the beam is scattered beyond 25 μm2. No specific data was available on the spatial resolution of x rays and this study aimed to improve that situation. The results also form the basis for establishing a mechanism for and defining the potential limits of quantitative EDS microanalysis in the ESEM.The negative viewing angle of the EDS x-ray detector in the current ESEM (model E-3) requires at least a 15 degree tilt on a flat sample for microanalysis. This geometry places a narrow limit on the working distance range that can be used, due to the collimation of the detector, thereby effectively eliminating working distance as a variable in x-ray microanalysis.

Chemical vapor deposition of tungsten step coverage and thickness uniformity experiments

A factorial experimental matrix was devised to study the effects of chamber pressure, hydrogen flow, silane flow, and tungsten hexafluoride flow on chemical vapor deposition (CVD) of tungsten step coverage and thickness uniformity. Experiments were conducted on 125 mm wafers with contact holes approximately 6000 Å deep and an aspect ratio of 1:1. A blanket layer of 1000 Å of titanium and 400 Å of titanium nitride was sputtered onto the wafer prior to CVD tungsten deposition. Cross-sectional scanning electron microscopy, tungsten thickness, and 49-point sheet resistivity measurements were made to characterize the tungsten films. The influence of process gas flows and flow ratios in CVD tungsten on step coverage and uniformity has been determined and found to generally agree with existing kinetic data and modelling results.

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

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 Al 2O 3 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).

Vacuum chamber pressure effects on thrust measurements of low Reynolds number nozzles

Tests were conducted to investigate the effect of vacuum facility pressure on the performance of small thruster nozzles. Thrust measurements of two converging-diverging nozzles with an area ratio of 140 and an orifice plate flowing unheated nitrogen and hydrogen were taken over a wide range of vacuum facility pressures and nozzle throat Reynolds numbers. In the Reynolds number range of 2200 to 12,000 there was no discernable viscous effect on thrust below an ambient to total pressure ratio of 1000. In nearly all cases, flow separation occurred at a pressure ratio of about 1000. This was the upper limit for obtaining an accurate thrust measurement for a conical nozzle with an area ratio of 140.

Process Characterization of a Load-Locked, Reactive Ion Etching System

AbstractWe report on process characterization of contact hole etching in a load-locked, hexa-gonal reactive ion etching system. Contact holes were etched in silicon dioxide and phos-phosilicate glass (PSG) with emphasis on wall profile control and selectivity to the underlayer of either single crystal silicon, polysilicon, or aluminum.To achieve these requirements, a two stage etch process was developed. In the first stage, controlled wall taper is obtained with a mixture of CHF3 and O2. The second stage utilizes a mixture of CHF3 and a small amount of CO2 to obtain high selectivity to the underlying material. Evaluation of the effects of chamber pressure, RF power, and gas mixture on taper angle, selectivity, resist erosion, and etch rates is presented.In addition, evidence which suggests that the reproducibility of optimum etch condi-tions can be enhanced by the use of a continuously pumped process chamber will be dis-cussed.

In-situ synthesis and growth of indium phosphide

The high partial pressure of phosphorus at the stoichiometric melting point of InP precludes the in-situ synthesis in the puller by simple admixture of indium and phosphorus. This paper describes a system that was considered for the in-situ synthesis and growth of InP single crystal, utilizing the phosphorus vapor injection method. The advantages of this two-heater side-by-side injection synthesis system is dis-cussed and the effect of chamber pressure and phosphorus temperature on the InP synthesis yield is described. The procedures used for in-situ synthesis and growth are also described. Electrical and optical properties of LEC cry-stals grown by in-situ synthesis compare favorably with those of crystals grown from polycrystalline charges synthe-sized with the high-pressure autoclave or the gradient freeze method.

Physics of Ion Plating and Ion Beam Deposition

A review of some dominant mechanisms in ion plating is made. Factors influencing throwing power and film quality are discussed and the damaging effects of a high ambient gas background are considered with a view toward minimizing the harmful effects of contaminant gas background. The physical mechanisms involved in an ion beam deposition process [S. Aisenberg and R. Chabot, J. Appl. Phys. 42, 2953 (1972)] are examined. The effects of chamber pressure, electrical bias arrangements, and the introduction of a coevaporant source are discussed with regard to deposition rate, ultimate film quality, and throwing power of the system.