低溫複晶矽薄膜電晶體製作於可撓式基板之研究

Abstract

可繞式薄膜電晶體研究是現今最受矚目之一的一項技術，擁有輕薄、可撓曲、容易隨身攜帶等特性。目前大多數可撓式元件都由多晶矽薄膜電晶體為主基礎應用；然而複晶矽薄膜電晶體技術相對於多晶矽薄膜電晶體有更佳的傳輸電流和更快的開關速度。對於可繞式顯示器的應用上，顯示器面板被要求能承受某種程度的撓曲。因此希望在不同撓曲情況下，能夠研究平行通道方向的撓曲對於不同通道長度之複晶矽薄膜電晶體電性在不□鋼基板上所產生的效應。 首先研究複晶矽薄膜電晶體在不□鋼基板上撓曲多次前後電性是否有劣化或穩定趨勢。接下來研究不同撓曲程度對元件電性上的影響，並且配合變溫量測和不同通道長度量測萃取源/汲極寄生電阻和缺陷密度來分析去除寄生電阻後載子遷移率的特性變化並且探討原因。最後研究在不同撓曲情況下，P型複晶矽薄膜電晶體在直流電壓操作下可靠度問題。實驗結果發現在撓曲的情況下，不論是張應力或壓應力起始電壓偏移均較平面情況下為嚴重，然而壓應力下經由長時間直流電壓操作後，載子遷移率較張應力下長時間直流電壓操作為佳，也顯示壓應力下對於元件的可靠度較張應力下更優。

In recent years, flexible display technology has been investigated significantly. They have characteristic of light、thin、bendy and portable! Much of recent flexible research on thin-film electronics has been focused on amorphous silicon TFT. But poly silicon thin film transistor technology provides a better alternative since it offers higher current and faster switching speed. And TFT based on metal foil has the advantage of cheap and softly. For application of flexible display, display panels are required to sustain a certain degree of bending. Bending would induce strain in the electronic circuits and may affect TFT device characteristics. So we investigate the effects of different radius of bending parallel the channel length on p-type poly silicon TFT on metal foil base. First, we investigate the trends after hundreds of bending parallel the channel length on p-type poly silicon TFT on metal foil base to make sure the electronic characteristics stable or not. Then extraction the parasitic resistance 、 flat band voltage and trap density 、threshold voltage、subthreshold slope and mobility. That’s help discuss the reasons of mobility and current changing under bending condition. Another consideration we also study the reliability of p-type polycrystalline silicon thin film transistors on metal foil fabricated by the ELC method under bending condition. We utilize DC stress to simulate the operation of P-type poly-Si TFTs and observe the degradation degree under bending condition. The result indicates that threshold voltage shift more worse in bending situation no matter under compressive or tensile condition than in plan situation. It also indicates that mobility under compressive bending drain bias DC stress better than tensile bending drain bias DC stress.