Journal of Vacuum Science & Technology B, Vol.28, No.1, 211-215, 2010
Indium oxide thin film transistors fabricated by low-energetic ion bombardment technique at room temperature
The authors report on InOx transparent thin-film transistor (TTFT) fabricated by low-energetic ion bombardment technique at room temperature. The InOx TTFTs were prepared using a coplanar bottom gate configuration with indium tin oxide (ITO), SiNx, and InOx thin films as the electrode, gate dielectric, and channel, respectively. The quality of the films could be significantly improved by eliminating bombardment of energetic particles created in the discharge processes using a prolonged target-to-substrate distance. The target-to-substrate distance for depositing SiNx was 15 cm, and 18 cm for depositing ITO and InOx. The leakage current density of the 180 nm thick SiNx films under 1.0 MV/cm field strength was less than 1 nA/cm(2). The C-V measurement of the Al/InOx/p-Si/Al capacitor structure showed that no hysteresis voltage was observed from the high-resistivity InOx films. This indicated that the electrical defects of the 150 nm thick InOx channels could be reduced using the long-throw deposition technique. In addition, the InOx TTFTs were engineered to operate in the enhancement mode with improved carrier mobility by adjusting the oxygen partial pressure during growth. The proposed InOx TTFTs with a 20 mu m channel length presented a saturation mobility of 3.8 cm(2) V-1 s(-1), a threshold voltage of 1.7 V, an on/off ratio of 2.3x10(6), and a subthreshold slope of 1.5 V/decade.
Keywords:carrier mobility;electrical resistivity;indium compounds;ion beam assisted deposition;ion beam effects;leakage currents;semiconductor thin films;silicon compounds;thin film transistors;transparency