Monocrystalline Si Films from Transfer Processes for Thin Film Devices

The transfer of thin monocrystalline silicon films to foreign substrates is of great interest for a number of applications such as silicon on insulator devices, active matrix displays and thin film solar cells. We present a transfer approach for the fabrication of monocrystalline Si films on foreign substrates based on the formation ofquasi-monocrystallineSi-films. Our transfer approach is compatible with high temperature processing such as epitaxial growth at 1100°C, thermal oxidation and phosphorous diffusion. Reuse of Si host wafers is demonstrated by the subsequent epitaxial growth of three monocrystalline Si films on a single host wafer. Monocrystalline Si films with a thickness of 15 µm and a diameter of 3” are transferred to glass and flexible plastic substrates. The typical light point defect density in films transferred from virgin wafers ranges between 10 to 100 cm−2, while stacking fault and dislocation densities are ≤ 100 cm−2. The minority carrier diffusion length in the epitaxial Si films is around 50 µm.