The Use of Functionally Graded Poly-SiGe Layers for MEMS Applications
It is difficult to meet all the different material and economical requirements posed to a MEMS structural layer that can be integrated with the electronics on the same substrate using a single layer process. Therefore a multilayer process, which uses a combination of a CVD crystallization layer and a high-growth rate PECVD bulk layer was developed. High-quality films with excellent electrical and mechanical properties can be obtained at low temperature (#450°C) and high deposition rates (~100 nm/min). Fine-tuning of the stress gradient is accomplished by the use of a top stress compensation layer, whose optimal thickness was estimated from an evaluation of the stress gradient profile over thickness. These layers have been used for processing a 10 µm thick poly-SiGe gyroscope on top of a standard 0.35 µm CMOS process.
Omer Van der Biest, Michael Gasik, Jozef Vleugels
A. Witvrouw and A. Mehta, "The Use of Functionally Graded Poly-SiGe Layers for MEMS Applications", Materials Science Forum, Vols. 492-493, pp. 255-260, 2005