以射頻磁控式共濺鍍系統製作氧化鋅基薄膜電晶體之特性研究

Investigation of ZnO-based Thin Film Transistors Deposited by Radio Frequency Magnetron Co-sputtering System

李欣縈(Hsin-Ying Lee) ； 林詠濠(Yong-Hao Lin) ； 謝文明(Wen-Ming Shien) ； 李清庭(Ching-Ting Lee)

《真空科技》 25卷1期 (2012/03) Pp. 40-46

https://doi.org/10.29808/JVSROC.201203.0005

摘要

本文章主要探討利用磁控式射頻共濺鍍系統製備氧化鋅基薄膜，並用以製作增強型下閘極式氧化鋅基薄膜電晶體，其中改變氧化鋅通道層厚度，並對不同閘源極電壓下之汲源極電流-汲源極電壓關係、固定汲源極電壓之汲源極電流-閘源極電壓關係與元件照光及變溫穩定性進行分析。在下閘極式薄膜電晶體中，由於電子通道是產生在通道層底部，故於源極與汲極間之載子的流動必須再經過非感應之低導電性的半導體區域，因而於此低導電性的區域導致許多壓降，所以為了提升元件整體的電性，必須設計最佳之通道層厚度。故於本篇文章中探討不同的通道層厚度對元件特性的影響，分別改變通道層厚度分別為10nm、30nm、50nm及75nm從事討論，其中以通到層厚度30nm為最佳，場效載子移動率達32.5cm^2/V-s，電流開關比（Ion/Ioff）為10^7。在照光波段為420nm~700nm探討之元件光穩定方面，在汲源極電流-閘源極電壓關係中，發現隨著照光的波長越短，光電效應越顯著，且汲源極電流隨著變大。在元件的熱穩定性方面，分別對元件進行25°C、50°C及75°C量測，發現線性區的阻值隨溫度變大而變大，所以在汲源極電流-閘源極電壓關係中，在閘源極電壓為正偏時，電流隨溫度變大而有變小之趨勢；在閘源極電壓為負偏時，關閉電流隨溫度變大而變大。

關鍵字

磁控式射頻共濺鍍系統 ； 薄膜電晶體 ； 氧化鋅

並列摘要

The purpose of this research is to investigate the performance of the bottom-gate type and enhancement-mode thin film transistors (TFTs). The ZnO-based thin films were deposited using radio frequency magnetron co-sputtering system. The drain-source current-drain-source voltage (IDS-VDS) and drain-source current-gate-source voltage (IDS-VGS) characteristics of the ZnO-based TFTs with various channel layer thicknesses were investigated. The thermal stability and the optical stability of the ZnO-based TFTs were also studied.In the bottom-gate type TFTs structure, the carriers were induced at the bottom of the channel layer. The carriers passed through a low conductivity region in the channel layer between the source and drain electrodes. Therefore, a larger voltage would be resulted on the low conductivity region. To improve the electrical performance of the ZnO-based TFTs, the optimize thickness of the channel layer was needed to be designed. In the paper, we investigate the performance of the Al slightly ZnO TFTs with various channel layer thicknesses of 10 nm, 30nm, 50nm, and 75nm. From the experimental results, 30-nm-thick channel layer was the best one. The field-effect mobility and on-off current ratio of the TFTs with 30-nm-thick channel layer were 32.5 cm^2/V-s and ~10^7, respectively. The Al slightly ZnO TFTs with 30-nm-thick channel layer were illuminated with optical light of 420~700 nm wavelengths for investigating the optical stability. In the IDS-VGS characteristics, the IDS increased with the illuminated short wavelength light and the optoelectronic effect was also in evidence. To investigate the thermal stability of the Al slightly ZnO TFTs with 30-nm-thick channel layer, the performances of the devices were measured at 25°C, 50°C, and 75°C, respectively. In the linear region of the IDS-VGS characteristics operated at the VGS＞0 the resistance increased with the measured temperature. This performance indicated that the drain-source current decreased with the increase of the measurement temperature. At the VGS＜0, the drain-source current increased with the increase of measurement temperature.

並列關鍵字

Magnetron RF Co-sputter ； Thin Film Transistors ； ZnO