Polysilicon in situ phosphorus doping control over large concentration range using low temperature,low pressure chemical vapour deposition growth process

Abstract

Silicon thin films, phosphorus doped in situ, have been deposited on to glass substrates using low pressure chemical vapour deposition at 550°C. The doping level is determined by adjusting the phosphine/silane molar ratio. Using this method a wide range of concentration is controllable. For a gas molar ratio varying between 4×10⁻⁸ and 4 × 10⁻⁴, phosphorus atomic incorporation is in the range 3 × 10¹⁶−3 × 10²⁰ cm⁻³. The resistivity of the layers varies from 8·3 × 10⁵ to 1·5 × 10⁻³ Ω cm. Lightly doped samples were passivated by hydrogenation, and Hall measurements were carried out, showing a marked improvement of the electrical properties. A lightly in situ doped drain thin film transistor suitable for active matrix applications was fabricated which exhibited good electrical properties.

MST/3335