Low-Stress Highly-Conductive In-Situ Boron Doped Ge_0.7Si_0.3 Films by LPCVD

This paper reports on low pressure chemical vapor deposited in-situ boron doped polycrystalline germanium-silicon layers with 70% germanium content. The effect of diborane partial pressure on the properties of the GeSi alloy is investigated. The obtained high boron concentration results in resistivity values less than 1 m_-cm. The layers deposited at low partial pressures of B2H6 exhibit very low stress down to –3MPa.With increasing B2H6 partial pressure first the stress changes from tensile to compressive, followed by a phase transition from polycrystalline to amorphous. The highly doped, low stress poly-Ge0.7Si0.3 layers deposited at 430◦C are further applied in high-Q microelectromechanical resonators envisaged for above-IC integration with CMOS.