具有T型閘極的自我對準氧化鋅薄膜電晶體之製作與特性分析

Abstract

在本篇論文中，我們構想出一種自我對準的T型閘極結構，並成功地將之製作於氧化鋅薄膜電晶體。此種T型閘極可自我對準地形成源/汲極金屬與氣體邊襯，對降低寄生電阻/電容有其助益。完成的元件展現良好的開關特性，但源/汲極電阻異常地大，其可能原因在本論文中有所探討。 為了更進一步了解此新的結構，我們探討了退火、電漿處理、閘極形狀和不同閘極氧化層對元件的影響。臨界電壓在退火之後會產生正向偏移，同時場效遷移率和開關電流比皆會上升。而電漿處理可以大幅改變通道的特性，依據電漿的種類可提高或降低通道的導電性。

In this thesis, we propose a self-aligned T-gate scheme and have successfully demonstrated it in the fabrication of ZnO TFTs. The T-shaped gate assists the formation of source/drain metal and sidewall air spacers in a self-aligned manner, which is beneficial for reducing the parasitic capacitance/resistance components. The completed devices exhibits good switching behavior, but anomalously high series source/drain resistances are identified which significantly degrade the device characteristics. Possible root causes for this phenomenon are discussed in this thesis. We also study the effects of annealing, plasma treatment, the shape of gate, and gate dielectric material on the performance of T-gate devices. The Vth shows a positive shift after the annealing in oxygen ambience accompanied with increases in field-effect mobility and on/off ratio. The plasma treatments are found to be able to dramatically change the channel properties such as increasing or decreasing the conductivity of the channel, depending on the kind of plasmas being used.