ITO像素电极工序对于HADS产品TFT特性的影响

通过不同TFT几何结构验证ITO像素电极工序对于HADS产品TFT特性的影响。实验结果显示TN5mask与倒反HADS结构(源漏极→ITO像素电极)二者有比现行HADS结构(ITO像素电极→源漏极)更高的Ion,提升比率达到40%。推测主要原因为现行HADS结构(ITO像素电极→源漏极)在Si岛完成后进行ITO像素电极工序增加了N+与源漏极之间接触阻抗导致Ion降低。对于HADS产品,倒反HADS结构(源漏极→ITO像素电极)可以具有更好的TFT特性表现。对现行HADS结构,在沟道形成工序前的N+表面ITO残沙程度越少则Ioff越低;对于倒反HADS结构,沟道形成之后沟道表面ITO残沙程度对则对TFT特性没有明显影响。对于Poole-Frenkel区域,现行HADS结构(ITO像素电极→源漏极)比TN5mask与倒反HADS结构(源漏极→ITO像素电极)二者较低Ioff[Vg=-20V],下降达50%,主要为N+与源漏极之间接触阻抗增加的影响。

Effects of pixel ITO process on TFT characteristics of HADS product

Effects of TFT structure on HADS product TFT properties was investigated. TN 5 mask and reversed HADS structure (SD pixel ITO) shows higher I_on about 40% than current HADS structure (pixel ITO SD). The lower I_on of current HADS structure (pixel ITO SD) may result from higher N+/SD contact resistance due to damaged N⁺ surface result from pixel ITO process on N⁺ surface. For current HADS structure, less ITO remain before channel formation leads to a lower I_off, while it shows no effect on TFT characteristic as ITO remain stays on formed channel for reversed HADS structure (SD pixel ITO). The current HADS structure shows a 50% lower Poole-Frenkel leakage current and lower Poole-Frenkel I-V slope than TN 5mask and reversed HADS structure (SD pixel ITO) also due to a higher N+/SD contact resistance.