Effect of stress on the aluminum-induced crystallization of hydrogenated amorphous silicon films

The effect of stress, resulting from the presence of hydrogen, on the aluminum-induced crystallization of hydrogenated amorphous silicon films was studied. Layered thin films of hydrogenated and unhydrogenated amorphous silicon and aluminum, deposited by sputtering, were used to study this effect. The stress of the deposited films was determined by measuring the radius of curvature of c-Si substrates before and after deposition of the films. It was observed that unhydrogenated amorphous silicon films exhibit a high compressive stress compared with hydrogenated ones. The amount of stress is shown to decrease with increasing hydrogen content. It was also observed that aluminum always provides tensile stress. After the initial stress measurements, all the samples were annealed for 30 min at temperatures between 200 °C and 400 °C. X-ray diffraction was used to determine the crystallinity of the silicon films. The results of the study show that the temperature at which crystallization of amorphous silicon is initiated is lower for films with a lower initial stress.