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) SiN x 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 SiN x deposition temperature is observed, with the magnitude of stress changing linearly from ∼300 MPa tensile stress to ∼600 MPa compressive stress as the deposition temperature is decreased from 300 to 100 °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 °C, whereas the values obtained via the diagnostic microstructures method deviate from the linear dependence for deposition temperatures below 100 °C. Stress uniformity over the deposition area is also investigated.