a Study of Local Atomic Structure and Thermal History in Thermally Grown and Remote Pecvd Deposited Silicon Dioxide Films.

Thin film SiO_2 is widely used as a high quality dielectric material for integrated circuit fabrication. Two important processes for forming SiO_2 are: (1) thermal oxidation of silicon at 700-1200^circC, and (2) remote plasma enhanced chemical vapor deposition (PECVD) at temperatures of 100-400^circ C. Values of the Si-O-Si bridging bond angle between corner connected SiO_4 tetrahedra and the bond angle distribution were determined by infrared spectroscopy (IR) from the Si-O bond stretching band via a central force model. The angular half-width of this distribution was found to be ~37 ^circ and compares favorably with direct x-ray determinations. I demonstrate, using the Clausius-Mossotti relationship, that molar volume changes in thermally grown SiO _2 derive from changes in the silicon-silicon distance (which is a function of the Si-O-Si bond angle) and that changes in molar volume are accommodated by changes in film thickness. I further demonstrate that the silicon-silicon distance can be used as a microscopic strain coordinate. The slope of the experimental intrinsic stress vs. strain curve was shown to yield a value for the plane strain Young's modulus, E/(1-gamma), with a value of 3.1 times 10^{11 } dyn/cm^2. This value is in good agreement with the literature, and since Young's modulus is a well characterized quantity, the self-consistency of our analysis is demonstrated. I have established that the most important factor in determining the local atomic structure of SiO _2 is thermally activated viscous flow allows rearrangement of SiO_4 tetrahedra in a lower energy configuration. This relaxation process is analyzed by a Maxwell model. An integrated processing system for low temperature remote PECVD deposition of dielectric films has been constructed. Semiconductor surface cleaning, remote PECVD deposition, and analysis capabilities are integrated in a common vacuum environment. I have devised a post-deposition furnace annealing process for remote PECVD SiO_2 films which: (1) preserves the electrical properties of the Si-SiO _2 interface, (2) relaxes the film structure so that it resembles a thermally grown film.