Effectiveness of SiO2 for preventing silicon -metal reactions at high temperatures

Abstract

Silicon dioxide layers, deposited by rf sputtering and measuring less than 1000 Å thick, were found to prevent silicide formation between evaporated silicon films and molybdenum substrates after annealing for 1 h at 1250 °C. Silicon grain size ranged from 0.2 to 2.5 μ in cross section. In situ Auger electron spectroscopy (AES) was used in the silicon deposition chamber to monitor the heat treated Si/SiO2/Mo samples for silicide formation. Composition depth profiling by ion beam sputtering and AES analysis was used to measure oxygen diffusion into the silicon and metal phases. This technique established that the breakdown of SiO2 as a reaction barrier between the molybdenum and silicon occurred because of oxygen diffusion from the SiO2 layer into the silicon. A similar behavior is expected between SiO2 and tungsten. However, when SiO2, deposited on tantalum, was heated to 1100 °C, the oxygen was found to have migrated into the metal resulting in the breakdown of the oxide layer.