五環素有機薄膜電晶體之操作原理與可靠度分析

Abstract

有機薄膜電晶體在面板技術的應用上，由於其具有可彎曲、低溫下製作和低成本的優勢，所以是非常合適用來製作低成本的電子元件。通常製作有機元件時會利用表面處理的方式來增加載子的移動率。但卻沒有人針對處理過後原件的可靠度做分析。因此論文研究利用兩種不同的表面處理過的元件和標準元件在DC及AC Stress下的變化。 首先，我們設計Gate Four-Probe(GFP)結構來萃取通道內部的電性特性，由此萃取出薄膜的本質參數。我們分析由Gate Four-Probe(GFP)所得到的電位可發現有機元件的傳輸機制與載子漂移的機制相當類似。之後我們將Gate Four-Probe(GFP)結構做在不同表面處理過後的基板上。論文中的元件分為標準和兩種不同表面處理的元件。標準元件只利用RCA清洗，其他的元件分別用HMDS或ODMS處理。一開始使用DC Stress，可發現標準元件對於負偏壓的Stress，VTH漂移量小但是對於正偏壓Vth漂移量大。而有表面處理的元件不管是正負偏壓，Vth漂移量都比標準片大。由Gate Four-Probe(GFP)所分析出的參數顯示pentacene薄膜並不隨Stress時間有所改變。因此Vth的改變應該是來自於Oxide或是表面處理layer所貢獻的。利用AC Stress，標準片的Vth漂移量大幅下降顯示出標準片在AC操作下具有較好的可靠度。但是有處理的HMDS和ODMS的Vth卻仍然有著較大的漂移量。經HMDS處理後的元件對於頻率和duty-cycle的相關性較大而利用ODMS處理的元件相關性較小。

Due to fixable, low temperature process and low cost, application of organic thin film transistor on flat plane display is very suitable to fabricate low cost device. Usually, surface treatment is used to increase mobility of carrier transport in organic thin film transistor. Until now, without anyone analyze reliability of device which is treated. Therefore this paper studies variation of device with and without surface treatment under different DC and AC stress condition. Firstly, we design Gated-Four-Probe (GFP) structure to extract characteristic of device in channel. Analysis of voltage distribution from Gated-Four-Probe can find that carrier transport mechanism of OTFT is consistent with carrier drift mechanism. Subsequently we fabricate Gated-Four-Probe (GFP) structure on different surface treatment substrate. The devices in this paper are separate to standard and two kinds of surface treatment. Standard device is cleaned by RCA clean and the other devices are treated by HMDS or ODMS. Initially, under DC stress condition we can find threshold voltage shift at positive gate bias stress is larger than at negative gate bias stress. Whether at positive or negative gate bias stress condition, Vth shift of devices with surface treatment are larger than standard devices. The extracted parameters from Gated-Four-Probe (GFP) indicate that pentacene film is not changed with time. Therefore reliability issues lie in the gate insulator or SAM layer degradation. Under AC stress condition, Vth shift of standard devices are obvious decrease. It appears that standard devices have better reliability at AC operation. But Vth shift of devices with HMDS and ODMS still have lager value.