製備不同鎵含量之銦鎵鋅氧化物濺鍍靶材及其應用於 上部閘極薄膜電晶體之研究

Abstract

本研究製備不同鎵（Gallium，Ga）含量的銦鎵鋅氧化物（Indium Gallium Zinc Oxide，IGZO）濺鍍靶材，並用以製備上部閘極（Top-gate）薄膜電晶體（Thin-film Transistor，TFT）。研究第一部分以商用氧化銦（In2O3）、氧化鎵（Ga2O3）及氧化鋅（ZnO）粉體為起始原料，利用化學分散搭配機械研磨技術製成良好分散的奈米粉體，再以無壓力式燒結製備化學劑量比為InGaZn2O5、InGaZnO4及InGa2ZnO5.5的三種IGZO靶材，X光繞射（X-ray Diffraction，XRD）分析顯示1300C、6至8小時的燒結可完成單相結構的InGaZn2O5與InGaZnO4靶材，InGa2ZnO5.5靶材則為Ga2ZnO4和In2O3的兩相混合結構，靶材相對密度均約為90%。第二部分研究使用上述三種靶材以濺鍍法製備TFT的載子通道層，XRD分析顯示所有初鍍態及經300C、1小時大氣退火之IGZO薄膜皆為非晶態，霍爾效應量測顯示InGaZn2O5與InGaZnO4薄膜的載子濃度（Carrier Concentration，N）約為1019 cm3，電阻率（Resistivity，）約為102 Ω-cm，InGa2ZnO5.5薄膜的N值則僅1017 cm3，值約為1-3 Ω-cm；InGaZn2O5薄膜有最高的霍爾效應載子遷移率（Hall-effect Mobility，Hall）為21.17 cm2V1sec1，而InGa2ZnO5.5薄膜的Hall值僅有7.43 cm2V1sec1。電性量測顯示300°C、1小時大氣退火處理可顯著提升TFT元件電性質，臨界電壓往負偏壓偏移，次臨界擺幅下降，含InGaZn2O5通道層的TFT有最佳的場效載子遷移率（Field-effect Mobility，FE）達9.95 cm2V1sec1，含InGa2ZnO5.5通道層的TFT之FE值則為1.97 cm2V1sec1，薄膜與元件性質隨Ga含量上升而劣化的結果可歸因於Ga3+抑制IGZO中氧空缺的產生，進而抑制了載子數量與遷移能力所致。

This study fabricates the indium gallium zinc oxide (IGZO) sputtering targets containing various Ga contents for preparing the active channel layers of top-gate thin-film transistors (TFTs). In first part of study, commercially available In2O3, Ga2O3 and ZnO powders served as the starting materials and a hybrid process of chemical dispersion and mechanical milling was adopted to form the aqueous suspensions containing finely dispersed, nano-scale oxide particles. A pressure-less sintering was then performed to yield the IGZO sputtering targets with relatively densities about 90% and stoichiometries of InGaZn2O5, InGaZnO4 and InGa2ZnO5.5. X-ray diffraction (XRD) indicated that sintering at 1300C for 6 to 8 hrs is able to form the single-phase InGaZn2O5 and InGaZnO4 targets whereas the InGa2ZnO5.5 target is comprised of mixed Ga2ZnO4 and In2O3 phases. The second part of study deposited the IGZO layers utilizing the self-parepared targets and XRD found that all as-deposited and 300C/1-hr annealed IGZO layers are amorphous. Hall effect measurement revealed the carrier concentrations (N) of InGaZn2O5 and InGaZnO4 layers are about 1019 cm3 and the resistivities () are 102 Ω-cm whereas the N and  for InGa2ZnO5.5 layer are about 1017 cm3 and 1-3 Ω-cm, respectively. Moreover, InGaZn2O5 layer exhibited the highest Hall-effect mobility (Hall) of 21.17 cm2V1sec1 and the Hall value of InGa2ZnO5 layer was about 7.43 cm2V1sec1. Electrical measurement of TFTs found that the 300°C/1-hr annealing substantially improves the device performance that the shift of threshold voltages toward the negative bias side and the reduction of subthreshold swings are observed. The TFT containing InGaZn2O5 channel layer possessed the highest field-effect mobility (FE) of 9.95 cm2V1sec1 whereas the FE of TFT containing InGa2ZnO5.5 channel layer was 1.97 cm2V1sec1. The property degradation of IGZO layers and TFTs with high Ga contents can be ascribed to the suppression of oxygen vacancies due to the presence of Ga3+ which, in turn, limits the number and transport capability of charge carriers in such a IGZO layer.