Polycrystalline silicon thin films prepared by plasma enhanced chemical vapour deposition at 200°C using fluorinated source gas

Polycrystalline silicon thin films have been developed using plasma enhanced chemical vapour deposition at a low substrate temperature 200 degrees C on glass substrates. An innovative approach has been introduced to deposit polycrystalline silicon film at such a low temperature. Usually a high deposition temperature is used to develop crystalline thin films. For the formation of crystallites a considerable amount of energy transfer is required at the surface of the growing film, which can be done by high-temperature processing. In the present work a high energy supply to the growing surface has been achieved by the increasing plasma power. Plasma power has been enhanced by the proper choice of deposition parameters, namely the nature of the source gas, the flow rate of diluent gas, the chamber pressure and the radiofrequency power density. Dark and photoconductivities achieved for the polycrystalline silicon thin films are 1.55 x 10(-6) S cm(-1) and 3.12 x 10(-5) S cm(-1) respectively. The average grain size of such film is similar to 4 mu m as seen by scanning electron microscopy, while the estimated size of crystallites from the x-ray diffraction spectra is 323 Angstrom.