Measurements of residual stresses in low-stress silicon nitride thin films using micro-rotating structures

A variety of rotating micro structures were designed, fabricated and characterized for residual-stress (or strain) measurements in low-stress silicon nitride thin films, deposited by LPCVD on silicon wafers. The sensitivities of the micro structures were calculated by finite element method (FEM) and verified experimentally. The results were further confirmed by utilizing the wafer-curvature method for stress measurements. The size of the structures enables local residual-stress (or strain) measurement. The stress level depends on both the film thickness and the gas ratio and also varies with the location on the wafer