POLYSILICON IN-SITU PHOSPHORUS DOPING CONTROL OVER LARGE CONCENTRATION RANGE USING LOW-TEMPERATURE, LOW-PRESSURE CHEMICAL-VAPOR-DEPOSITION GROWTH-PROCESS

Silicon thin films, phosphorus doped in situ, have been deposited on t o glass substrates using low pressure chemical vapour deposition at 55 0 degrees C. The doping level is determined by adjusting the phosphine /silane molar ratio. Using this method a wide range of concentration c oncentration is controllable. For a gas molar ratio varying between 4 x 10(-8) and 4 x 10(-4), phosphorus atomic incorporation is in the ran ge 3 x 10(16)-3 x 10(20) cm(-3). The resistivity of the layers varies from 8.3 x 10(5) to 1.5 x 10(-3) Omega cm. Lightly doped samples were passivated by hydrogenation, and Hall measurements were carried out, s howing a marked improvement of the electrical properties. A lightly in situ doped drain thin film transistor suitable for active matrix appl ications was fabricated which exhibited good electrical properties. (C ) 1995 The Institute of Materials.