Fractal Aggregation Behavior in Amorphous Silicon Nitride Films

A fractal aggregation behavior in amorphous silicon nitride (Si_x N_y) films deposited by microwave electron cyclotron resonance plasma chemical vapor deposition is reported. The fractal structure and dimension of 1.45 obtained by experiment and computer simulation are all in excellent agreement with the result predicted by the cluster-cluster-aggregation model. The forming of fractal structure is related to the change of discharge mode between ring plasma and bulk plasma.