a-Si剩余膜厚对TFT特性的影响

Effect of thickness of a-Si remain on TFT characteristics

本文通过电学特性测试设备在黑暗(Dark)和光照(Photo)两种测试环境下,研究了沟道不同a-Si剩余厚度对TFT电学特性的影响.通过调整刻蚀时间改变沟道内a-Si剩余厚度,找出电学特性稳定区域以及突变的临界点.实验结果表明:在黑暗(Dark)环境下a-Si剩余厚度在30%~48%之间时,TFT器件的电学特性比较稳定,波动较小;而剩余厚度少于30%时,TFT特性变差,工作电流变小,开启电压变大,电子迁移率变小;在光照环境下主要考虑漏电流的影响,在a-Si剩余厚度43%以内时,光照Ioff相对较低(小于Spec20pA),同时变化趋势较缓;而剩余厚度大于43%时,光照Ioff增加25%,同时变化趋势陡峭.综合黑暗和光照测试环境,在其他条件不变的情况下,a-Si剩余厚度在30%~43%之间时TFT的电学特性较好,同时相对稳定.

The effects of different a-Si remain thickness of channel on the electrical properties of TFT were studied under dark and photo test environments. The thickness of a-Si remain in channel was changed by adjusting the etching time. Futhermore, the stable region and the critical point of radical change of electrical were found through this experiment. The experimental results show that the electrical characteristics of TFT devices are relatively stable and fluctuate slightly when the thickness of a-Si remain is between 30% and 48% in dark environment. When the remaining thickness is less than 30%, the TFT characteristics become worse, I on becomes smaller, V th becomes larger, and the mobility decreases consequently. Unlike dark condition, I off is the chief consideration under photo circumstance. When the thickness of a-Si remain is less than 43%, photo I off is relatively low (less than spec 20 pA), and the trend of change is relatively slow. But when the residual thickness is more than 43%, photo I off increases by 25%, and the trend of change is steep. In conclusion, when the thickness of a-Si remain is between 30% and 43%, the electrical characteristics of TFT are better and relatively stable regardless of test conditions.