Stress in low-temperature plasma enhanced chemical vapour deposited silicon nitride thin films

Two experimental techniques have been investigated to examine residual stress in low-temperature plasma enhanced chemical vapour deposited (PECVD) SiNx thin films: one that measures the stress-induced Substrate Curvature, and the other that takes advantage of the stress-induced deformation of freestanding, diagnostic microstructures. A general linear dependence of residual stress on SiNx deposition temperature is observed, with the magnitude of stress changing linearly from similar to 300 MPa tensile stress to similar to 600 MPa compressive stress as the deposition temperature is decreased from 300 to 100 degrees C. However, the results deviate from the linear dependence by a different degree for both measurement techniques at low deposition temperatures. The stress values obtained via the Substrate Curvature method deviate from the linear dependence for deposition temperatures below 200 degrees C, whereas the values obtained via the diagnostic microstructures method deviate from the linear dependence for deposition temperatures below 100 degrees C. Stress uniformity over the deposition area is also investigated.