Simultaneous Optimization Of The Material Properties, Uniformity And DepositionRate Of Polycrystalline CVD And PECVD Silicon-Germanium Layers For MEMSApplications

摘要

Poly-crystalline Silicon-Germanium is a promising structural materialrnfor post-processing Micro Electro-Mechanical Systems (MEMS)rnabove CMOS due to its excellent mechanical and electrical propertiesrnwhen deposited at CMOS compatible temperatures. In this work anrnoptimized process to deposit high quality crystalline poly-SiGe layersrnwith low stress, low strain gradient and good within-wafer uniformityrnat a manufacturable throughput is developed. The process used torndeposit the layers is based on a combination of CVD and PECVDrnSiGe depositions. Firstly, the CVD SiGe process has been extensivelyrncharacterized to the extent that the influence of thickness, Gernconcentration and B concentration on film stress and strain gradient isrnnow well understood. Then the interaction between the PECVD SiGernand the underlying CVD layer has been investigated. This combinedrnknowledge enables specific tailoring of the CVD-PECVD SiGe stackrnto give the desired strain gradient for a certain layer thickness.