Silicon dioxide films by RF sputtering for microelectronic and MEMS applications

Abstract

In the present work, we report low temperature (<285 °C) RF sputter deposition of silicon dioxide films for microelectronic and MEMS applications. The films were prepared by RF diode sputtering using a 3 inch diameter SiO2 target in argon atmosphere in the pressure range 5–20 mTorr and RF power from 100 to 300 W. The effect of deposition parameters (RF power and sputtering pressure) on various properties such as deposition rate, surface morphology, surface roughness, stress and etch rate of silicon dioxide films are investigated. The deposition parameters are optimized to obtain the films having low surface roughness and minimum stress. Due to the advantage of much lower thermal budget of the sputtering process compared to thermal oxidation, the application of RF-sputtered SiO2 films in IC fabrication is explored. Boron diffusion experiments are conducted using a sputtered SiO2 film as a masking layer. In order to investigate the application of RF-sputtered silicon dioxide films for MEMS, SiO2 microstructures such as bridges and cantilever beams were fabricated using bulk and surface micromachining processes. We also explore silicon wafer bonding using RF-sputtered silicon dioxide films as an intermediate layer.