新型低光致漏電非晶矽薄膜電晶體之製作與機制研究

The Study on Fabrication and Mechanism of New Style a-Si:H Thin Film Transistor with Low Photo-Induced Leakage Current

傅棕晟(Zong-Sheng Fu)

指導教授 ： 葉鳳生 ； 張鼎張

國立清華大學/電機資訊學院/電子工程研究所/碩士(2006年)

https://doi.org/10.6843/NTHU.2006.00174

摘要

提升薄膜電晶體開關特性的技術是主動式矩陣顯示器技術發展的一重要趨勢，尤其在光致漏電方面，更是需要迫切解決的課題。在本研究中我們利用兩種方式來達成低光致漏電的非晶矽薄膜電晶體製作。我們首先提出一個方法來降低薄膜電晶體在關閉狀態(off-state)的光致漏電。我們選擇一種可以在矽半導體材料中產生深層缺陷能態(deep traps)的方法，來當作傳導載子的復合中心(recombination center)。將作為比較組的電晶體利用紫外光處理的方式，使深層缺陷能態產生在主動層之中。雖然此方法造成電子有效遷移率些微的下降，但是降低的程度是在可以容忍的範圍之內。光漏電的機制可以解釋這個結果，因為在照光之下，由於深層缺陷能態為強力複合中心因此可以快速的消除由照光產生的電子電洞對。
其次，我們另外提出一個新穎結構的非晶矽(a-Si:H)薄膜電晶體，可以抑制背光模組照射薄膜晶體所導致的漏電。我們利用氧化銦錫(ITO)來取代傳統薄膜電晶體結構中的源極於汲極。利用氧化銦錫與矽所產生的異質接面來阻擋形成光漏電的電洞電流。並且可利用在傳統光屏蔽結構(island in structure)中，達到抑制蕭特基漏電的效果。本研究所提出的ITO新穎結構當處於背光時可以使光致漏電(photo leakage current)低於傳統結構達一個級數。我們提出的結構所擁有的穩定特性，可以使顯示品質更好。這樣的高性能表現，有極大的潛力應用於主動式矩陣液晶顯示器(AMLCD)及主動式矩陣有機發光二極體顯示器(AMOLED)技術中。

關鍵字

主動式矩陣顯示器 ； 光致漏電 ； 復合中心 ； 氧化銦錫

並列摘要

There has been a tendency to improve the characteristics of switches in AMLCD (active matrix liquid-crystal display) technology. Particularly, the large photo-induce leakage current is an issue that need to be imminently solved. In this thesis, the amorphous silicon thin film transistors (a-Si:H TFTs) with low photo-induced leakage current will be proposed and studied.
The first, an alternative method has been proposed to suppress photo leakage current of a-Si TFT operated at off-state. We introduce a deep level trap center, made by UV light treatment, into Si film to act as recombination centers. After treating conventional BCE TFTs by UV light, deep traps will be made in active layer by UV light. Experimental results have shown the photo leakage current of devices is lower than that of a-Si TFT without be treated by UV light. Although the mobility is decreased slightly, the degradation of mobility is still tolerable. The mechanism is mainly based on the photo leakage mechanics that deep traps have good ability to recombine electron hole pairs made by back light illuminate.
In addition, a novel a-Si:H TFT structure has been demonstrated to suppress the leakage current under back-light illumination. We will change source and drain metal pads in conventional structure to ITO. Using the heterojunction between ITO and a-Si to reduce photo leakage current. And ITO can be used in conventional island in structure to eliminate schottky leakage current. When under the gate-side illumination, the ITO new structure TFT shows a photo-induced leakage current as low as one order of magnitudes, compared to the conventional a-Si:H TFT device. The superior characteristics of the proposed structure can potentially provide better visual quality for AMLCD products. For that reason, the high performance provides the potential of the proposed a-Si:H TFT to apply for AMLCD and AMOLED technology.

並列關鍵字

active matrix liquid-crystal display ； photo-induce leakage current ； recombination center ； ITO

參考文獻

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