下世代平面顯示器高性能銦鎵鋅氧化物薄膜電晶體之設計、成長、製作與特性分析(I)

Abstract

薄膜電晶體為平面顯示器重要的開關以及驅動元件，主動式液晶平面顯示器(AMLCD)為目前主流技術，而主動式有機發光二極體顯示器(AMOLED)為次世代顯示技術的主流，AMOLED具有自發光性、廣視角、高對比、反應速度快等優勢，目前智慧型手機市場已開始採用AMOLED面板，而銦鎵鋅氧化物為極具潛力發展薄膜電晶體之材料，本計畫利用首創大氣電漿鍍膜技術開發高性能銦鎵鋅氧化物薄膜電晶體，具新技術價值以及低成本優勢，計畫分做三年執行，第一年將專注開發大氣電漿銦鎵鋅氧化物薄膜最佳化製程條件，並探討不同基板溫度、電漿源功率、銦鎵鋅比例、氧分壓、主動層厚度以及前驅物對薄膜電晶體特性做探討，第二年則引入高介電常數絕緣層並透過電漿處理絕緣層以及主動層搭配後處理來達到高性能的薄膜電晶體，第三年則研究接觸阻抗的議題，透過選擇不同的金屬，以及嵌入一層高摻雜的半導體層來降低接觸阻抗，並探討經過後續退火對於源/汲極與銦鎵鋅氧化物介面特性研究，最後則研究就不同的鈍化層對於薄膜電晶體的穩定性做探討，透過這些有組織且詳細的分析研究，來開發下世代平面顯示器之高性能銦鎵鋅氧化物薄膜電晶體。

Active-matrix liquid-crystal display (AMLCD) is the mainstream of display technology, while active-matrix organic light emitting diode (AMOLED) is a next generation display technology for use in mobile phone, television, and digital cameras. AMOLED displays provide high perceived luminance, high contrast ratio, wide viewing angle, and fast response than passive-matrix OLED. These advantages make active-matrix OLEDs well suited for portable electronics, where power consumption is critical to battery life. An AMOLED display consists of an active matrix of OLED pixels that generate light upon electrical activation that have been deposited or integrated onto a thin film transistor (TFT) array, which functions as a series of switches to control the current flowing to each individual pixel. Pixel switching elements need TFTs to operate at high voltages as well as low gate leakage current to drive the liquid crystal. Moreover, high performance TFTs which have low operation voltage, small sub-threshold swing, large driving current, and low gate leakage are necessary to achieve high speed display circuits. Indium-gallium-zinc-oxide (IGZO) is the most potential material on developing TFTs because of high carrier mobility, high stability, and less photosensitivity. These characteristics are better than amorphous TFTs, which make IGZO TFTs can be fabricated on large area electrics application. The object of this project is use APPECVD technology to fabricate high performance IGZO TFTs, which is highly valuable in novel technology and low cost. This project will be divided into three parts. First, we will establish a stable IGZO deposition process using APPECVD system. In order to grow best performance IGZO thin film, the optimal condition will be used to achieve high carrier mobility, high stability, and less photo sensitivity IGZO thin film. The conditions contain different substrate temperature, the power of plasma source, the composition ratio of IGZO, the partial pressure of oxygen, thickness, and precursors. Second, in order to exchange traditional silicon dioxide, we will introduce high dielectric constant (high-k) material to forming gate dielectric. Different plasma treatment and different annealing on dielectric and IGZO thin film will be utilized to fabricate high performance and high reliability IGZO TFTs. Third, we will improve the contact resistance on S/D and the stability of IGZO TFTs with different passivation layers. Choosing different metals and inserting a highly doped semiconductor layer between metal and IGZO film could decrease the contact resistance. We will investigate the interface characteristics between S/D and IGZO after thermal annealing. Moreover, different passivation layers will be used to examine the stability of IGZO TFTs. In this project, the high performance IGZO TFTs will be fabricated by using organized system and detail analyzed method. In conclusion, we believe it will be a breakthrough technology to develop next generation flat panel display.