The chemical vapor deposition of polycrystalline silicon nitride films at low temperatures.

摘要

Polycrystalline films of {dollar}rm Sisb3Nsb4{dollar} (silicon nitride) were deposited by CVD (chemical vapor deposition) at relatively low temperatures, as low as 1150{dollar}spcirc{dollar}C, and high growth rates, e.g, 450 {dollar}mu{dollar}m/hr at 1190{dollar}spcirc{dollar}C. Previously, crystalline growth at these rates has been reported only at temperatures above 1350{dollar}spcirc{dollar}C. The high growth rates, which were attained at technologically reasonable temperatures, makes CVD {dollar}rm Sisb3Nsb4{dollar} a more promising candidate for protective coatings for high temperature applications. Crystalline film growth was attained at low temperatures by manipulating the crystalline nucleation process. Mechanisms leading to low temperature crystalline nucleation were studied.; Crystalline film deposition occurred over a very narrow range of CVD process parameters, {dollar}rm SiHsb4{dollar} or NH{dollar}sb3{dollar} inlet concentrations or temperature. At these lower temperatures, crystalline film growth was nucleation limited. Invariably, nucleation occurred on a growing amorphous interlayer the composition of which gradually changed from Si-rich near the substrate to stoichiometric amorphous silicon nitride at its surface where the crystalline film nucleated abruptly. Detailed characterization of the nucleation process was performed with a combination of FT-IR, XPS, X-ray diffraction and TEM. Film nucleation on a growing interlayer complicates both classical and atomistic treatments of nucleation theory. It was proposed that the chemical and localized atomic structure of the interlayer controls the nucleation event.; In order to more easily control poly-crystalline film growth, a two step CVD process was developed which enabled low temperature, crystalline film growth on a variety of substrates, metal and ceramic. Additionally, the effect of CVD process conditions on film surface morphology and chemical composition were analyzed, and explanations, some of which were different than traditional CVD arguments, were proposed.; CVD was performed in an impinging jet configuration, a configuration in which mass transport is well defined and which allowed simple kinetic modeling of the growth process. Crystalline growth was first order dependent on SiH{dollar}sb4{dollar} concentration and not dependent on NH{dollar}sb3{dollar} concentrations greater than 0.2. An activation energy of 9600/R was measured which is remarkably similar to poly-crystalline Si growth. This could imply that SiH{dollar}sb{lcub}rm x{rcub}{dollar} species are rate limiting.; By coating the films with a silicon oxynitride layer, enhanced oxidation resistance was achieved. High diamond nucleation densities were obtained in a preliminary study.