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Determination of mechanical properties of PECVD silicon nitride thin films for tunable MEMS Fabry–Pérot optical filters

2005; IOP Publishing; Volume: 15; Issue: 3 Linguagem: Inglês

10.1088/0960-1317/15/3/024

1361-6439

Han Huang, K.J. Winchester, Yinong Liu, Xiaozhi Hu, C.A. Musca, J.M. Dell, L. Faraone,

Diamond and Carbon-based Materials Research

This paper reports an investigation on techniques for determining elastic modulus and intrinsic stress gradient in plasma-enhanced chemical vapor deposition (PECVD) silicon nitride thin films. The elastic property of the silicon nitride thin films was determined using the nanoindentation method on silicon nitride/silicon bilayer systems. A simple empirical formula was developed to deconvolute the film elastic modulus. The intrinsic stress gradient in the films was determined by using micrometric cantilever beams, cross-membrane structures and mechanical simulation. The deflections of the silicon nitride thin film cantilever beams and cross-membranes caused by in-thickness stress gradients were measured using optical interference microscopy. Finite-element beam models were built to compute the deflection induced by the stress gradient. Matching the deflection computed under a given gradient with that measured experimentally on fabricated samples allows the stress gradient of the PECVD silicon nitride thin films introduced from the fabrication process to be evaluated.