Estimation of bending of micromachined gold cantilever due to residual stress

Electroplated gold is widely used as the material for the micromachined beam structures due to its excellent electrical and mechanical properties. This work attempts to analyze the surface micromachined gold cantilever beams under inherently present stress gradient. The structure is analyzed by using finite element method simulation at different intrinsic stress gradients. The gold layers are deposited using cyanide electroplating bath operated at different current densities. Residual stresses in electroplated gold layers deposited on photoresist coated silicon samples are estimated by using X-ray diffraction technique. Cantilever beam structures are fabricated using surface micromachining technique. The tip deflections of the fabricated cantilever beams are found to be ~16 and 8 μm corresponding to the 1.0 and 0.7 mA/cm2 current densities (mean), respectively. The corresponding intrinsic stress gradients are estimated to be −13.9 and −7.2 MPa/μm, respectively. Simulated and measured values of residual stresses are well matched.