以射頻磁控濺鍍法製作氧化鎂鋅/氧化鋅異質接面場效電晶體

Abstract

由於單晶異質結構不適合於低成本、大面積的電子元件應用，所以我們探討多晶系統異質結構並期望能進一步應用於工業化中。 在本論文中使用射頻磁控濺鍍法在室溫下成長氧化鋅薄膜。首先我們藉由GIXRD、SEM、AFM、XPS分析來討論未經處理與後退火處理對氧化鋅薄膜(15nm)的影響。之後我們探討氧化鎂鋅/氧化鋅異質結構的極化效應。由於氧化鋅結晶程度的改善，我們可以觀察到極化效應在氧化鎂鋅/氧化鋅異質結構中，且片載子濃度隨著氧化鎂鋅中鎂成分的增加而提升。 接著我們在玻璃基板上製作氧化鎂鋅/氧化鋅異質接面薄膜電晶體。我們發現氧化鋅的厚度與鎂的成分會強烈影響電晶體的I-V曲線。由於極化效應與屏蔽效應的關係，氧化鎂鋅/氧化鋅異質結構的電晶體開電流部分較對照的氧化鋅電晶體高一至兩個數量級，臨界電壓隨鎂成分增加而減小。我們發現氧化鋅厚度對氧化鎂鋅/氧化鋅電晶體的影響，較厚氧化鋅厚度觀察到有較強的極化效應。另一方面對孤立氧化鎂鋅/氧化鋅通道層可有效降低關電流。 最後我們選用Mg0.2Zn0.8O/ZnO(15nm) 薄膜電晶體做成N-MOS反向器，其在β=15、操作電壓18V下增益為19.6。 關鍵字：射頻磁控濺鍍法、氧化鋅、薄膜電晶體、極化效應

Due to the single-crystalline heterostructures are not suitable for low-cost large-area electronic applications, so we study the polycrystalline heterostructure material system and hope that it can be further applied in industry. In this thesis, ZnO thin films are grown by RF-sputtering at room temperature. First, we investigate the properties of the as-deposited and 600°C post-annealed ZnO(15nm) thin films by GIXRD, SEM, AFM, and XPS. Then we studied the electrical properties of the MgZnO/ZnO heterostructures. Polarization effect is observed only in the heterostructures with post-annealed ZnO due to the reinforcement of the grain formation in ZnO. Sheet carrier concentration of the MgZnO/ZnO heterostructures increases as the Mg content in the MgZnO layer is raised. Then, we demonstrate the rf-sputtered MgZnO/ZnO heterostructure thin film transistors on the glass substrates. We found that the I-V characteristics of the TFTs is strongly dependent on the thickness of ZnO and Mg content. Due to the polarization effect and screening effect, the on current of the MgZnO/ZnO TFT is about one to two orders of magnitude larger than that of the counterpart ZnO TFT and the threshold voltage decreases as the Mg content increases. In addition, the off current can be effectively reduced due to isolated active layer of MgZnO/ZnO. Finally, we fabricate the N-MOS inverter composed of Mg0.2Zn0.8O/ZnO(15nm) TFTs with a beta ratio of 15. An inverter gain of 19.6 is obtained biased at a voltage of 18V. Keywords: RF-sputtering, ZnO, thin film transistors, polarization effect