Low Temperature Atmospheric Pressure Chemical Vapor Deposition Of Group 14 Oxide Films

Depositions of high quality SiO[sub 2] and SnO[sub 2] films from the reaction of homoleptic amido precursors M(NMe[sub 2])4 (M = Si, Sn) and oxygen were carried out in an atmospheric pressure chemical vapor deposition r. The films were deposited on silicon, glass and quartz substrates at temperatures of 250 to 450C. The silicon dioxide films are stoichiometric (O/Si = 2.0) with less than 0.2 atom % C and 0.3 atom % N and have hydrogen contents of 9 [plus-minus] 5 atom %. They are deposited with growth rates from 380 to 900 [angstrom]/min. The refractive indexes of the SiO[sub 2] films are 1.46, and infrared spectra show a possible Si-OH peak at 950 cm[sup [minus]1]. X-Ray diffraction studies reveal that the SiO[sub 2] film deposited at 350C is amorphous. The tin oxide films are stoichiometric (O/Sn = 2.0) and contain less than 0.8 atom % carbon, and 0.3 atom % N. No hydrogen was detected by elastic recoil spectroscopy. The band gap for the SnO[sub 2] films, as estimated from transmission spectra, is 3.9 eV. The resistivities of the tin oxide films are in the range 10[sup [minus]2] to 10[sup [minus]3] [Omega]cm and do not vary significantly with deposition temperature. The tin oxide film deposited at 350C is cassitterite with some (101) orientation.

"Low Temperature Oxide (LTO) thin films were prepared using a Low Pressure Chemical Vapor Deposition process. The process was characterized by applying traditional statistical studies and response surface technique. The uniformities within wafer and from wafer to wafer were examined by determining the mean and the standard deviation of films thicknesses. Response surface methodology was employed to determine the optimum process conditions. Time, temperature and gas flow ratio were used as the experimental factors. Index of refraction and deposition rate were used as the experimental responses. Additionally, etch rate, density, dielectric constant and infrared (IR) spectra were found for the silicon dioxide films prepared at the determined optimum condition. The IR spectra were obtained by employing Fourier Transform Infrared Spectroscopy (FTIR). The average deposition rate was found to be 46 A per minute and the average index of refraction was 1.44. The calculated density, activation energy, etch rate, dielectric constant and dielectric strength agreed with reported values. A double metal test run was performed using LTO oxide. The results indicated that the recommended baseline LTO process is suitable for multilayer metallization processes."--Abstract.

A laboratory-scale reactor and a novel method for the atmospheric pressure chemical vapor deposition (APCVD) of SiO2-x films are developed. The deposited films are investigated to synthesize heterogeneously upon the substrate surface with the elimination of the so-called gas-phase reaction, hence preventing parasitic oxide particles upon the substrate surface and the reactor inner walls. The films are extensively inspected in terms of chemical and optical properties and utilized for crystalline silicon solar cell applications. Simple reactor design with low safety measures, a wide range of deposition rates, high film resilience, and stability for the intended applications are successfully achieved. The newly developed APCVD SiO2-x is proven to protect the Si wafer surface against texturing in alkaline and acidic solutions. Electroplated metallization schemes of heterojunction and passivated emitter rear contact solar cells are examined with the use of the SiO2-x as a masking layer in the grid electrode-free area.

The book addresses the problem of passivation at the surface of crystalline silicon solar cells. More specifically, it reports on a high-throughput, industrially compatible deposition method for Al2O3, enabling its application to commercial solar cells. One of the main focus is on the analysis of the physics of Al2O3 as a passivating dielectric for silicon surfaces. This is accomplished through a comprehensive study, which moves from the particular, the case of aluminium oxide on silicon, to the general, the physics of surface recombination, and is able to connect theory with practice, highlighting relevant commercial applications.