Stress Changes in Silicon Nitride Thin Films on Thermal Cycling and Deconvolution of Separate Contributions

Abstract

A correlation between stress in amorphous silicon nitride films and their composition has been established. This has led to the deposition of low-stressed films at low temperatures. The density of the films calculated from the results of Rutherford Backscattering Spectroscopy and Nuclear Reaction Analysis techniques is high, around 2.4 g/cm3, indicating a dense network. The films exhibit relatively high coefficient of thermal expansion, around 3.2 ppm/{degree sign}C, indicating a fairly short-range order in the film. Furthermore, a reversible thermally induced stress, i. e., a negligible stress hysteresis upon thermal cycling between room temperature and 400{degree sign}C has been observed in the film. From the stress response of the films to the thermal cycling separate contributions from the thermal and athermal components to the net room temperature stress have been deconvoluted.