Impact of the deposition and annealing temperature on the silicon surface passivation of ALD Al2O3 films

The effect of the deposition and annealing temperature on the surface passivation of atomic layer deposited Al2O3 films was investigated on n-type Cz silicon wafers. The deposition temperature was varied between 200 and 500°C and the annealing temperature between 300 and 450°C, respectively. Films prepared at 200 and 300°C showed an improvement of surface passivation with increasing anneal temperature. The Al2O3 films grown at 400 and 500°C did not improve by annealing. By corona charging experiments it was revealed that the improvement in surface passivation with increasing anneal temperature of films grown at 300°C can be attributed to a significant increase in chemical passivation with a minor increase in field-effect passivation. For Cz and FZ wafers an identical surface passivation was achieved with the chemical passivation being lower for Cz wafers due to the surface morphology and the field-effect passivation being quite similar. Consequently the field-effect passivation was found to be the more important passivation mechanism