Sputtered high mobility indium silicon oxide thin film transistors

Abstract

Development of Ultra-High Definition (UHD) flat panel displays requires newlinethe fabrication of Thin-Film Transistors (TFT) with small feature size, very high newlinemobility and wide optical band gap. Metal oxide semiconductors based TFTs are newlineknown to have high mobility and wide optical band gap. Among the various metal newlineoxide based semiconductors, indium oxide based system has the best performance. newlineThe high negative carrier concentration of the indium oxide system can be newlineeffectively suppressed by the addition of Silicon (Si) to enhance the semiconductor newlinebehaviour. The effect of oxygen partial pressure during deposition process, effect of post newlineannealing temperature and the effect of channel dimensions on the properties of newlineIndium Silicon Oxide (ISO) TFT were studied. The variation in oxygen partial newlinepressure had minimal effect on the structural, optical and topographical properties of newlinethe ISO thin-film. However, the increase in the oxygen partial pressure had a major newlineimpact on the electrical properties leading to a shift from conducting to newlinesemiconducting nature. The ISO TFTs deposited with 5% oxygen partial pressure newlineand post annealed at 100 °C exhibits a saturation mobility of 31.7 cm2/V.s, on-off newlinecurrent ratio of 2.3×1010, turn-on voltage of -5 V and sub-threshold swing of 0.25 newlineV/dec. The effect of annealing temperature on ISO thin-films revealed the phase newlinetransition from amorphous phase to polycrystalline phase at a temperature of 175 °C newlineand a slight increase in the surface roughness with the increase in the annealing newlinetemperature was observed. The ISO TFTs fabricated using the ISO thin-film post newlineannealed at various temperatures exhibited excellent electrical properties in the newlinetemperature range of 100 °C to 250 °C and the highest saturation mobility of 39.1 newlinecm2/V.s was achieved for polycrystalline ISO TFTs post-annealed at 200 °C. The newlineimpact of the channel dimensions on the electrical properties of the ISO TFTs newlineindicates that the major factor influencing the properties was the channel length newlineiv which determines the turn-on vo