Published online by Cambridge University Press: 15 February 2011
Inverted-staggered hydrogenated amorphous-silicon thin-film transistors (a-Si:H TFTs) were deposited in a glow discharge with an excitation frequency of 60 MHz. At 13.56 MHz it has been reported that the field-effect mobility of this type of TFT decreases with increasing deposition rate of the a-Si:H layer, due to an increase in the defect density in the channel. A successful way of increasing the deposition rate without deteriorating the material properties has turned out to be utilizing a higher excitation frequency than the conventional 13.56 MHz.
The deposition rate of the 60-MHz-deposited transistor channel was changed from 350 to 1300 Å/min by diluting the process gas silane with hydrogen and by changing the rf power. The dependence of the a-Si:H material properties on deposition parameters is described. The deposition rate dependence of the mobility in the 60-MHz deposited thin films and devices is presented and discussed in terms of hydrogen dilution in the plasma and the hydrogen content of the a-Si:H films.