Remote plasma-enhanced chemical vapor deposition of Si02 using a radio-frequency (rf) Ar/N20 plasma and downstream-injected SiH4 was investigated. The deposition rate at 20 W rf power was measured as a function of pressure, temperature, and SiH4 flow rate. The Si02 deposition rate at 300°C and 300 mTorr depends linearly on the SiH4 flow rate. The deposition rate is independent of N30 flow rate for N20/SiH4 ratios much greater than 1, consistent with oxygen saturation of the growth surface. The deposition rate increases linearly with pressure up to 400 mTorr. A plateau in the deposition rate is observed above 400 mTorr, and is ascribed to the onset of parasitic gas-phase reactions leading to particle formation. Negative apparent activation energies are observed at pressures 400 mTorr, suggesting that adsorption of Si-bearing species is the rate-limiting step in SiO, deposition. The deposition chemistry was probed using real-time quadrupole mass spectrometry (QMS) and optical emission spectroscopy (OES). The H and H2O QMS signal intensities increase monotonically with SiH4 flow rate; approximately 0.67 moles of H3 and 1.33 moles of H20 are produced per mole of SiH4 consumed. OES evidences the presence of Ar metastables, N2 metastables, excited NO molecules, and atomic 0 in the plasma. Fourier transform infrared spectroscopy of thick Si02 films demonstrated that Si-H and Si-OH groups are present at very low concentrations (<1 atom %).Single-wavelength ellipsometry indicated that films deposited under typical 0-rich conditions have an average refractive index of 1.464.

Selective deposition of μc-Si on hydrogenated amorphous silicon is demonstrated using time-modulated silane reactant flow in a low temperature plasma enhanced process. Alternating cycles of thin silicon layer deposition and atomic hydrogen exposure result in silicon layers on receptive surfaces, with no net deposition on nonreceptive areas of the substrate. Selective deposition could be useful to form self-aligned contacts in hydrogenated amorphous silicon (a-Si:H transistor applications. However, a problem commonly observed in low temperature selective deposition is that the selective process tends to etch amorphous silicon, harming the devices. We describe a technique involving Mo metallization that stabilizes the a-Si:H surface with respect to hydrogen plasma exposure and allows selective μc-Si deposition on a-Si:H in device structures, while avoiding deposition on the top SiNx insulator material. Surfaces and subsequent selective nucleation and growth were characterized using atomic force microscopy, x-ray photoelectron spectroscopy, and Auger electron spectroscopy, which revealed the presence of Mo incorporation in the a-Si:H surface remaining after complete removal of the metal layer. A direct comparison of selective deposition experiments on films prepared with and without Mo treatment demonstrate that the metallization stabilizes nucleation of microcrystalline silicon on amorphous silicon surfaces.

Silver-exchanged zeolites are the most efficient materials for xenon adsorption at pressures in the ppm levels. It is widely accepted that silver moieties constitute the active phase in the adsorption. Among them, ZSM-5 appears to be the most efficient topology owing to its pore size and geometry. In this study, we fully exchanged seven different sodium-form zeolites (four ZSM-5, two BEA, and one MOR) to silver-form, characterized them, and compared their xenon adsorption capacities. Modeling the isotherms with a double-site Sips model allowed a quantitative comparison of their performances. The results confirmed a linear trend between the concentration of strong adsorption sites and the silver amount contained in the ZSM-5 and BEA zeolites. At the same time, it revealed that silver-exchanged MOR deviates from that trend and generates xenon adsorption sites in a higher-pressure range. Moreover, the 27Al NMR measurements displayed a clear linear correlation between the amount of strong, silver-based, adsorption sites and the amount of exchangeable, framework aluminum-based, sites. Overall, this study revealed that an increase in the silver content leads to an increase in strong adsorption sites in a pressure range that depends on the zeolite structure. In addition, the tetra-coordination of aluminum must be checked to guarantee a high silver loading in pentasil-based zeolites.