Optimization Of Poly-Sige Deposition Processes For Modular Mems Integration

This paper describes a bi-layer deposition technique to reduce the strain gradient of polycrystalline silicon-germanium (poly-SiGe) thin films without the use of any post-deposition annealing. By adjusting deposition conditions such as temperature, pressure, and/or flow rates of reactants, poly-SiGe films with required low average stresses can be obtained. Using the bi-layer technique, a strain gradient of 1.1 x 10(-5) mum(-1) (equivalent to 88 min radius-of-curvature) has been achieved in 3.9 mum-thick poly-SiGe. This strain gradient would cause only 0.055 mum tip deflection for a 100 mum-long cantilever. The thermal budget was similar to10 hours at 425degreesC, and no post-deposition annealing was required. The bi-layer film also exhibits low compressive average stress (-36 MPa) and low resistivity (0.55 mOmega-cm).