Performance of a-Si:H Thin Film Transistors Fabricated by Very High Frequency Discharge Silane Plasma Chemical Vapor Deposition

This paper discusses the dependence of a-Si:H thin film transistor (TFT) performance on the plasma excitation frequency for a-Si:H film deposition. We studied the effects of the plasma excitation frequency over the range of 13.56–50 MHz, altering the deposition rate under various conditions. At the conventional 13.56 MHz frequency, the field effect mobility value decreases to 0.19 cm 2 V -1 s -1 at a deposition rate of 76nm/min. As the excitation frequency increases, the rate of mobility drop to the deposition rate decreases in the high rate deposition region. A mobility value as high as 0.40 cm 2 V -1 s -1 can be obtained at a high deposition rate of 130 nm/min using a 50 MHz frequency.