In situ analysis of aluminum enhanced crystallization of hydrogenated amorphous silicon (a-Si : H) using X-ray diffraction

Deposition of polysilicon at low temperatures is important for the low cost production of electronic devices, especially solar cells and active matrix liquid crystal displays (AMLCD). In this paper in situ X-ray diffraction s tudies of aluminum enhanced crystallization of hydrogenated amorphous silic on (a-Si:H) at low temperatures is reported. Hydrogenated amorphous silicon films were deposited on oxidized silicon substrates. Aluminum was deposite d on the a-Si:H using evaporation. X-ray diffraction analysis was done in a n evacuated temperature controlled camera at a glancing angle of 5 degrees using thin film optics. Growth in the [111] silicon peak was monitored whil e annealing the samples at 200, 225, 250 and 275 degrees C, Results show th at the area under the [111] silicon peak grows linearly with time. The rate of crystallization was found to be higher at higher temperatures. Al-induc ed crystallization was found to follow an Arrhenius type dependence. The ac tivation energy for the thermally activated phenomenon controlling crystall ization was calculated to be 1.1 eV. This is close to the reported activati on energy of 1.2 eV for the diffusion of Al in a-Si:H. (C) 1999 Elsevier Sc ience S.A. All rights reserved.