Low Stressed In-situ Boron doped Poly SiGe Layers for High-Q Resonators

Polycrystalline silicon-germanium (Poly SixGe1-x) can be used as one of the microstructural materials for MEMS due to its superior mechanical properties [1,2], high quality factor [3] and low thermal budget requirements based on the Ge contents [4] (<450 oC) for post processing on top of CMOS chip. This work deals with the characterization of in-situ boron doped poly SiGe layers LPCVD deposited at 430 oC with a mixture of 0.2% diborane (B2H6) in Argon on 110 nm SiO2. The concerned properties like sheet resistance and residual stress in the deposited layers are investigated at diborane mixture flow of 50 sccm and 100 sccm. It is observed that the deposition rate is decreased with the increase of B2H6 mixture flow. Whereas, the resistivity of these deposited layers decrease linearly with the increase of B2H6 mixture flow. The stress in the deposited layers shows a trend from low tensile to low compressive with the increase of diborane mixture flow. The properties of the layers deposited at 50 sccm of diborane mixture flow shows good results in terms of resistivity, deposition rate, cross load thickness uniformity and residual stress and therefore qualify them to use as structural layers for the realization of disk resonator.