Characterization of Reduced-pressure Chemical Vapor Deposition Polycrystalline Silicon Germanium Deposited at Temperatures ≤550 °C

This paper investigates the possibility of reducing the deposition temperature of polycrystalline silicon germanium to a level compatible with complementary metal-oxide semiconductor (CMOS) post processing. To achieve this goal, the exact wafer temperature during deposition was experimentally determined and it was found to be 30 °C lower than the reactor setting temperature. The deposition temperature was reduced from 625 to 500 °C. The impact of varying the deposition pressure from 10 to 760 torr and the germanium content from 15% to 100% was investigated. X-ray diffraction spectroscopy and transmission electron microscopy showed that the Si_xGe_1−x films deposited at an actual wafer temperature of 520 °C are polycrystalline for germanium contents as low as 15%. Also, it was shown that the deposition conditions can be adjusted to yield a low tensile stress at an actual wafer temperature of 520 °C, which is suitable for integrating surface micromachined micro-electromechanical systems on top of standard CMOS wafers with Al interconnects.