Fabrication of low-stress dielectric thin-film for microsensor applications

Abstract

A method of fabricating low-stress dielectric thin film as the supporting material of micromachined devices is reported. The film is processed by post thermal oxidation of silicon-rich nitride (SN) deposited on silicon substrate by LPCVD. Due to the compensation on the nitride by its top oxide, an ultra-low residual less than 10 MPa can be obtained with proper oxidation scheme. Characteristics of the oxidized nitride were analyzed by Auger electron spectroscopy (AES) and ellipsometry. Large floating membranes of 4 x 4 cm(2) and 400-nm thick can be made by this method with TMAH etching.