Modelling of aluminum enhanced crystallization in hydrogenated amorphous silicon (a-Si:H)

Deposition of polysilicon at low temperatures is important for the low cost production of electronic devices, especially large area devices like solar cells and active matrix liquid crystal displays (AMLCD). In this paper, a model for crystallization of hydrogenated amorphous silicon (a-Si:H), based on in-situ x-ray diffraction studies, is reported. The a-Si:H films, intrinsic, as well as phosphorus-doped were deposited on oxidized silicon substrates. Aluminum was deposited onto the a-Si:H using evaporation. X-ray diffraction analysis was done in an evacuated temperature controlled camera la glancing angle using thin film optics. The growth in the < 111 > silicon peak was monitored while annealing the samples at 250 and 275 degrees C. Area of the < 111 > silicon peak was used as an indicator of the volume crystallized. A crystallization model was developed for the change in the crystallized volume fraction. A good fit was obtained between the model and the experimental data. Phosphorus doping in a-Si:H was shown to retard crystallization rate.