LPCVD deposition

Materials Properties of LPCVD Deposited MEMS Materials... 

Since advanced lithography tools with resolution down to sub 100 nm may not be readily available, some novel techniques to fabricate ID nanochannels have been developed and reported. One of these techniques uses standard microfabrication process and has the potential to make integrated nanofluidic devices [2]. This technique is similar to the spacer technique developed in solid-state electronic device fabrication. A spacer is the thin side wall achieved by conformal deposition of selected thin film on the side wall of a sacrificial structure. With the fine control of the LPCVD deposition process, a spacer as thin as 10 nm can be made. After removing the sacrificial structure, a spacer as thin as 10 nm is left on the substrate, which can be subsequently used as a mask to pattern nanometer lines or used as a sacrificial line to make a nanochannel. Other novel techniques involve shrinking a larger channel made by standard micromachining to smaller sizes by methods such as filling the channel with other materials [3]. 

Dielectric Film Deposition. Dielectric films are found in all VLSI circuits to provide insulation between conducting layers, as diffusion and ion implantation (qv) masks, for diffusion from doped oxides, to cap doped films to prevent outdiffusion, and for passivating devices as a measure of protection against external contamination, moisture, and scratches. Properties that define the nature and function of dielectric films are the dielectric constant, the process temperature, and specific fabrication characteristics such as step coverage, gap-filling capabihties, density stress, contamination, thickness uniformity, deposition rate, and moisture resistance (2). Several processes are used to deposit dielectric films including atmospheric pressure CVD (APCVD), low pressure CVD (LPCVD), or plasma-enhanced CVD (PECVD) (see Plasma technology). 

A second type of siUcon nitride, called stoichiometric siUcon nitride, is deposited at much higher temperatures using CVD or LPCVD in the form of Si N. Stoichiometric siUcon nitride can be used as a mask for the selective oxidation of siUcon. Here the siUcon nitride is patterned over a siUcon substrate, and the exposed siUcon is oxidized. The siUcon nitride oxidizes very slowly compared to the siUcon. 

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. 

Kaplan, W., and Zhang, S., Determination of Kinetic Parameters of LPCVD Processes from Batch Depositions, Stoichiometric Silicon Nitride Films, Prac. 11th. Int. Conf. on CVD, (K. Spear and G. Cullen, eds.), pp. 381-387, Electrochem. Soc., Pennington, NJ 08534 (1990)... 

In this sub-subsection, the Er doping of amorphous silicon is discussed. The problem of limited solubility of Er in crystalline silicon has been circumvented. However, the electrical properties of pure a-Si are poor compared to c-Si. Therefore, hydrogenated amorphous silicon is much more interesting. Besides, the possibility of depositing a-Si H directly on substrates, i.e., optical materials, would make integration possible. Both low-pressure chemical vapor deposition (LPCVD) [664] and PECVD [665, 666] have been used to make the a-Si H into which Er is implanted. In both methods oxygen is intentionally added to the material, to enhance the luminescence. 

Laser molecular beam epitaxy, fabrication method for inorganic materials, 7 415t Laser photochemical vapor deposition (LPCVD), 19114-116 Laser pointers, 14 678 Laser-promoted dehydrohalogenation,... 

Low polarity plasticizers, 74 479 Low power package, 74 863 Low pressure catalytic processes, 20 151 Low pressure chemical vapor deposition (LPCVD), 5 807, 811-812 Low-pressure gas separation, spiral-wound membrane modules for, 75 823-824 Low pressure hollow-fiber membranes, 76 24-26... 

A schematic view of the cold cathode fabrication process is shown in Fig. 10.18. The cold cathode is fabricated by low pressure chemical vapor deposition (LPCVD) of 1.5 pm of non-doped polysilicon on a silicon wafer or a metallized glass substrate. The topmost micrometer of polysilicon is then anodized (10 mA cnT2, 30 s) in ethanoic HF under illumination. This results in a porous layer with inclusions of larger silicon crystallites, due to faster pore formation along grain boundaries. After anodization the porous layer is oxidized (700 °C, 60 min) and a semi-transparent (10 nm) gold film is deposited as a top electrode. 

A thick (> 1 jum) field oxide layer is formed after the implant activation. The field oxide is generally deposited nsing low-pressnre CVD (LPCVD) or plasma-enhanced CVD (PECVD) process becanse the Si-face of SiC has very low oxidation rate and becanse consumption of the implanted layer must be minimized. The field oxide layer is then patterned by selectively etching to remove all oxide from the... 

Since Si02 substrates appear frequently during IC fabrication, the adhesion test results for this substrate are important. Four types of oxides have been extensively tested. They are (1) thermal oxide grown at 7>1000°C, (2) softer oxide processed by conventional spin-on-glass technology, (3) phosphorus-doped LPCVD oxide, and (4) low-temperature (200°C) plasma deposited oxide. 

Heat transfer is an extremely important factor in CVD reactor operation, particularly for LPCVD reactors. These reactors are operated in a regime in which the deposition is primarily controlled by surface reaction processes. Because of the exponential dependence of reaction rates on temperature, even a few degrees of variation in surface temperature can produce unacceptable variations in deposition rates. On the other hand, with atmospheric CVD processes, which are often limited by mass transfer, small susceptor temperature variations have little effect on the growth rate because of the slow variation of the diffusion with temperature. Heat transfer is also a factor in controlling the gas-phase temperature to avoid homogeneous nucleation through premature reactions. At the high temperatures (700-1400 K) of most... 

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