Deposition fixturing

The ability to scale-up (up-scale) a deposition process and associated equipment to provide a quality product at an attractive price is essential in the commercialization of any process. It is important that the development work be done on representative substrate material and with processes and equipment that can be scaled to production requirements. An important factor in manufacturability is the deposition fixturing, which holds the substrates in the deposition chamber. The fixturing determines how the parts are held and moved and the number of parts that can be processed in each cycle. The vacuum pumping system and deposition chamber size are also important in determining the process cycle time. 

CVD reactions are most often produced at ambient pressure in a freely flowing system. The gas flow, mixing, and stratification in the reactor chamber can be important to the deposition process. CVD can also be performed at low pressures (LPCVD) and in ultrahigh vacuum (UHVCVD) where the gas flow is molecular. The gas flow in a CVD reactor is very sensitive to reactor design, fixturing, substrate geometry, and the number of substrates in the reactor, ie, reactor loading. Flow uniformity is a particulady important deposition parameter in VPE and MOCVD. 

Decorative chromium plating, 0.2—0.5 ]lni deposit thickness, is widely used for automobile body parts, appHances, plumbing fixtures, and many other products. It is customarily appHed over a nonferrous base in the plating of steel plates. To obtain the necessary corrosion resistance, the nature of the undercoat and the porosity and stresses of the chromium are all carefliUy controlled. Thus microcracked, microporous, crack-free, or conventional chromium may be plated over duplex and triplex nickel undercoats. 

The plasma jet can be cooled rapidly just prior to coming in contact with the substrate by using a blast of cold inert gas fed into an annular fixture. Gaseous boron or phosphorus compounds can be introduced into the gas feed for the deposition of doped-semiconduc-tor diamond. 

In fact, when testing corrosion inhibitors, the major amount of corrosion may occur under the mounting washers as fresh inhibitor cannot reach such a confined space and, in addition, the low oxygen concentration leads to corrosion. As in the section above, ferric ions may seep from within the crevice and deposit around the fixture, thus giving rise to under-deposit corrosion. 

Because TSM oscillators have been around for over 50 years, quite a number of circuits to measure their response have been proposed, fabricated, and tested. The frequency of operation of TSM resonators (typically < 20 MHz) allows circuits to be constructed using ordinary components and printed circuit boards. Instruments and fixtures are commerciaUy available from a number of vendors (see Appendix D) that utilize fairly simple oscillator circuits incorporating the TSM resonator as the principal fiequency-control element. These systems are sold primarily for monitoring the deposition of metal films via evaporation or sputtering in a vacuum environment. The operator must typically input the density and acoustic impedance of the metal to be deposited, and the instrument then displays film thickness as deposition proceeds. These systems can also be utilized for gas-phase sensing applications, provided the TSM device is not coated with any particularly lossy materials these can cause so much damping that oscillation ceases. The systems provide information derived only from the resonant frequency there is no indication of damping except in the instance that oscillation ceases entirely. 

Since supercritical fluids were chosen for their ability to penetrate small cracks and crevices, additional tests were performed to evaluate this characteristic. A test cube modeled after a similar fixture fiibricated by Ferranti Aerospace, was developed and manufactured to md in this study. The cube had a number of blind holes, tapped holes, dtannels and crevices to simulate actual hardware. Beryllium, 300 Series stainless steel and aluminum cubes were constructed to simulate the conunon metals found in the instrument. In addition, the sides of the cube were removable to facilitate deposition of the contaminants into these blind holes and crevices and later analysis of cleaning effectiveness. The base of the cube was equipped vrith a scanning electron microscope (SEM) mount so that the cube could be examined directly in the SEM. Figure 3 is a photograph of a test cube. Extensive evaluations with these test cubes indicated that supercritical fluids were indeed effective at removing contaminants from cracks and crewces. 

When the total concentration of iron in water is 0.3 mg/L or greater, the iron will cause the water to have an unpleasant taste and redden in color—this may result in the staining of plumbing fixtures and clothes, and accumulations of iron deposits in the... 

The chemicals leached from these surfaces depend on the corrosive properties of the particular water as well as the chemical nature of the surface. Hard water tends to deposit a mineral layer on the inside of pipes and on other surfaces that essentially limits the access of water to the surfaces. On the other hand, soft water, particularly at lower pHs, can actively dissolve toxic metals such as lead or cadmium from pipes or solder. Copper in pipes is also frequently leached from pipes at high concentrations when the water has corrosive properties. Asbestos-cement has been used widely in water mains. The extraction of the asbestos fibers from these surfaces is also very much increased at lower pH and with soft water. The use of lead pipe and solder in household pipes has pretty much been abandoned in the United States. However, alloys of lead are still utilized in many faucets and brass fixtures (e.g., submersible pumps). Rather high concentrations of lead can result if water stands in these fixtures overnight. As a result it is always wise to avoid using the water first drawn from the tap in the morning for human consumption. Low levels of lead exposure in utero or in the first few years of life have been associated with delayed CNS development in humans and experimental animals. 

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