使用氧氣中性粒子束電漿處理之大氣常壓電漿輔助化學氣相沉積製備非晶銦鎵鋅氧薄膜電晶體研究

Abstract

傳統型的薄膜電晶體存在著幾項缺點：較高的操作電壓和次臨界擺幅、較大的臨界電壓、較高的製程溫度還有電子遷移率較低等等，突顯了傳統薄膜電晶體已不滿足現今追求的高解析度、高電性、高電子遷移率和低溫製程等需求。 在近幾年來新興的薄膜電晶體技術中最受矚目的是非晶銦鎵鋅氧薄膜電晶體(a-IGZO TFTs)，和傳統非晶矽薄膜電晶體（a-Si:H TFTs）比起來有較大的電子遷移率(>10 cm2/V·S)、高穿透率和低製程溫度，然而跟低溫多晶矽薄膜電晶體(LTPS)比起來製程簡單許多。 本篇論文中，我們使用了大氣壓電漿輔助化學氣相沉積(AP-PECVD)來沉積我們的銦鎵鋅氧主動層。藉由此系統我們可以不用在真空系統下便可沉積我們的銦鎵鋅氧通道層，因此降低我們的成本且可以大面積製作。 為了提升非晶銦鎵鋅氧薄膜電晶體的特性，本篇論文中，我們利用中性束氧電漿處理非晶銦鎵鋅氧薄膜，明顯地改善元件的漏電流、開關電流比和次臨界擺幅。中性束電漿有別於傳統的電漿，它可以去除紫外光和中和帶電粒子，降低離子轟擊所造成的損害。 我們成功製作出藉由大氣壓電漿輔助化學氣相沉積沉積主動層且經中性束氧電漿處理主動層之非晶銦鎵鋅氧薄膜電晶體。經能量400W中性束氧電漿處理過的銦鎵鋅氧當主動層的薄膜電晶體效能明顯地提升，它擁有相當的電子遷移率10.78cm2/V·S，更小的次臨界擺幅 100 mV/decade，更高的開關電流比 2.76×106 且較小的關閉電流3.7×10-12 安培明顯地優於未經中性束氧電漿處理過的。

The disadvantages of conventional thin film transistor are high operation voltage, high threshold voltage, poor subthreshold swing, and lower field-effect mobility. These indicate that the traditional thin film transistor does not satisfy with the high performance, high stability, high resolution, lower temperature process and high field effect mobility nowadays. Amorphous In-Ga-Zn-O (IGZO) thin film transistors have now become the focal point of our fields in recent years. It showed higher mobility(>10 cm2/V．S), high transmittance, and low process temperature compared to the conventional a-Si:H TFTs. Furthermore, the a-IGZO TFTs did not need complicated process compared with low temperature ploy-Si (LTPS) TFTs. In this investigation, we used atmospheric-pressure PECVD (AP-PECVD) to deposit our IGZO channel layer. By AP-PECVD, we could deposit IGZO channel layer without vacuum system. Therefore, it could keep the cost down and applie evidently d to large area manufacturing. To further improve the electrical characteristics of a-IGZO TFT, in this study, we used neutral beam oxygen plasma treatment on top of IGZO thin film. We found that plasma treatment of oxygen neutral beam could improve leakage current, Ion/off, and subthreshold swing evidently. Unlike conventional plasma, neutral beam plasma could eliminate irradiated charged particles, electrons, and UV photons to avoid damage from ion bombardment. Successfully, we fabricated a-IGZO TFT by AP-PECVD to deposit IGZO channel and oxidation treatment by neural beam. It reveals that lower off current improvement and better subthreshold swing are obtained from the case with 400W of NB power. It exhibited high mobility of 10.78 cm2/V·S, low off current of 3.7×10-12 A, small subthreshold swing of 93 mV/decade, and better Ion/Ioff of 2.76×106.