Thick PECVD silicon dioxide films for MEMS devices

Abstract

This paper discusses the relationships between the deposition parameters and properties of thick (e.g., 5μm) tetraethylorthosilicate (TEOS) silicon dioxide films deposited on silicon wafers using a dual-frequency plasma-enhanced chemical vapor deposition (PECVD) system. The deposition parameters, including the ratio of low frequency (LF) power to high frequency (HF) power and the TEOS flow rate, were varied to investigate their effect on the residual stress, the deposition rate, and the etch rate of TEOS silicon dioxide film. Analysis of variance (ANOVA) statistical technique was used to verify that the experimental data are valid rather than coincidences of random sampling. The calculated P-values of the deposition parameters verify that the ratio of LF/HF power and the TEOS flow rate significantly affect the residual stress and the etch rate of the films. For the deposition rate, only the TEOS flow rate has a significant effect. The difference in the intrinsic and thermal stresses of TEOS silicon dioxide films co-deposited on the silicon and stainless steel wafers are presented and discussed. TEOS silicon dioxide films are electrically characterized at elevated temperatures (up to 300°C) using metal-insulator-metal (MIM) capacitors. The characterizations show that capacitance decreases with increasing temperature, as well as with the process thermal budget (temperature×time).