Direct-current substrate bias effects on amorphous silicon sputter-deposited films for thin film transistor fabrication

Seung-Ik Jun and Philip D. Rack

Department of Materials Science and Engineering, The University of Tennessee, Knoxville, Tennessee 37996-2200

Timothy E. McKnight, Anatoli V. Melechko, and Michael L. Simpson

Molecular Scale Engineering and Nanoscale Technologies Research Group, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831

(Received 18 June 2005; accepted 6 August 2005; published online 22 September 2005)

The effect that direct current (dc) substrate bias has on radio frequency-sputter-deposited amorphous silicon (a-Si) films has been investigated. The substrate bias produces a denser a-Si film with fewer defects compared to unbiased films. The reduced number of defects results in a higher resistivity because defect-mediated conduction paths are reduced. Thin film transistors (TFTs) that were completely sputter deposited were fabricated and characterized. The TFT with the biased a-Si film showed lower leakage (off-state) current, higher on/off current ratio, and higher transconductance (field effect mobility) than the TFT with the unbiased a-Si film. ©2005 American Institute of Physics