Dielectric layers for MEMS deposited at room temperature by HMDSO-PECVD

Several SiO2 films were deposited on stainless steel substrate by means of a low-temperature HMDSO-PECVD process under different conditions. Adhesion to substrate was determined by scratch testing and the influence of metallic interlayers deposited by magnetron sputtering was investigated. Electrical properties of the films were assessed by DC and AC tests before and after thermal ageing and bending tests. None of the measured films resulted to be altered by thermal ageing, while in many case bending test caused a reduction of the adhesion and the formation of microscopic cracks which induce a loss in dielectric properties. Under certain particular conditions, however, the film is stable after both ageing and bending tests and the insulating properties of the films are comparable to the properties of silane-PECVD SiO2 films.