Low-temperature diffusion of Al into polycrystalline Si

Diffusion of Al into a polycrystalline Si layer chemically deposited at 640 °C was studied by capacitance-voltage characteristics, sheet resistance, and electron microprobe measurements in the 180–550 °C temperature range. It has been found that diffusion of Al into polycrystalline Si takes place at temperatures as low as 300 °C, and that the polycrystalline Si becomes electrically conductive. The sheet resistance of polycrystalline Si decreases with increasing annealing temperature. Annealing at a higher temperature, however, induces migration and recrystallization of Si in Al, and the original polycrystalline-Si layer loses its integrity.