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 materialfor post-processing Micro Electro-Mechanical Systems (MEMS)above CMOS due to its excellent mechanical and electrical propertieswhen deposited at CMOS compatible temperatures. In this work anoptimized process to deposit high quality crystalline poly-SiGe layerswith low stress, low strain gradient and good within-wafer uniformityat a manufacturable throughput is developed. The process used todeposit the layers is based on a combination of CVD and PECVDSiGe depositions. Firstly, the CVD SiGe process has been extensivelycharacterized to the extent that the influence of thickness, Geconcentration and B concentration on film stress and strain gradient isnow well understood. Then the interaction between the PECVD SiGeand the underlying CVD layer has been investigated. This combinedknowledge enables specific tailoring of the CVD-PECVD SiGe stackto give the desired strain gradient for a certain layer thickness.