In situ hydrogen plasma treatment for improved transport of (4 0 0) oriented polycrystalline silicon films

Polycrystalline silicon (poly-Si) films were deposited on glass by very high-frequency (100 MHz) plasma enhanced chemical vapor deposition from a gaseous mixture of SiF4 and H2 with small amounts of SiH4. (2 2 0) oriented films prepared at small SiF4/H2 ratios (<30/40 sccm) showed intrinsic transport properties of poly-Si. However, the room temperature dark conductivity (σd) of the (4 0 0) oriented film was very high for intrinsic poly-Si, 7.2×10−4 S/cm. This conductivity exhibited a T−1/4 behavior, suggesting a high defect density at the grain boundaries. It was found that in situ hydrogen plasma treatment successfully produced (4 0 0) oriented poly-Si with a reasonably low σd of 4.5×10−7 S/cm and a good photoconductivity of 1.3×10−4 S/cm.