氮化鋁鎵/氮化鎵金屬氧化物半導體高電子遷移率場效電晶體之研究

The Study of AlGaN/GaN Metal-Oxide-Semiconductor High Electron Mobility Field Effect Transistors

張仁誠(Jen-Cheng Chang)

指導教授 ： 彭隆瀚

國立臺灣大學/電機資訊學院/光電工程學研究所/碩士(2011年)

https://doi.org/10.6342/NTU.2011.10921

摘要

本論文主要討論兩大部分，第一為使用晶格面蝕刻法與光致電化學氧化法在氮化鋁鎵/氮化鎵結構上成長氧化鎵氧化膜，第二為氮化鋁鎵/氮化鎵金氧半高電子遷移率場效電晶體元件之製作與研究。
使用晶格面蝕刻法在氮化鋁鎵/氮化鎵上製作平滑側壁並使用光致電化學氧化法成長氧化鎵氧化膜，利用SEM與AFM量測結果，觀察與討論氧化鎵氧化膜之品質。
另外，本研究參考傳統歐姆接觸製程，設計元件的歐姆接觸，並利用傳輸線模型(Transmission line model，TLM)，濺鍍金屬鈦/鋁/鈦/金(15 nm/100 nm/60 nm/200 nm)，在825度60秒的熱退火條件下，製作出2.1627*10-6Ω-cm2的歐姆接觸特徵電阻值，並改良電晶體元件結構為奈米線之高台；再應用光致電化學氧化法，即在氮化鋁鎵/氮化鎵表面生成氧化物，藉此得到自我鈍化的作用。當閘極偏壓為2V，閘極長度為2μm時，我們調變汲極與源極間距為8μm、6μm及4μm，進行直流飽和電流、轉導增益以及高頻特性分析。實驗結果發現，縮短間距不但可提升直流特性，並可增加截止頻率由原來的27.8GHz提升至28.6GHz。此外，本研究濺鍍二氧化矽保護層使漏電流從10-4A減少到10-10A，並將汲極與源極間距縮為2μm，使截止頻率提高至30GHz，最後，本研究對其電流崩塌效應做討論。

關鍵字

氮化鋁鎵/氮化鎵 ； 氮化鋁鎵/氮化鎵金氧半高電子遷移率電晶體 ； 光致電化學氧化裝置

並列摘要

There are two issues in this thesis. The first issue is on wet chemical crystallographically etching and the growth of native gallium oxide by photoelectric chemical method(PEC method) on AlGaN/GaN substrate. The second issue is on the fabrication and characterization of AlGaN/GaN metal-oxide-semiconductor high electron mobility field effect transistors(MOS-HEMTs).
The sidewalls of stripes became smooth and straight on AlGaN/GaN by wet chemical crystallographic etching and we found the growth of native gallium oxide on AlGaN/GaN by the PEC method. The characteristics and quality of the native oxide layer is studied by using in SEM and AFM analysis.
Furthermore, we investigate the methods to improve the electric properties of AlGaN/GaN MOS-HEMTs. Using a transmission line model (TLM) analysis, we obtained an ohmic contact with specific resistance of 2.1627*10-6Ω-cm2 on the AlGaN/GaN samples patterned with a stack electrode of Ti/Al/Ti/Au (15nm/100nm/60nm/200nm) and annealed at 825℃ for 60s.We applied a new transistor structure with a nanostructure mesa and use the PEC method to form native oxide passivation oxide layers on the surfaces of AlGaN/GaN. By varying the drain-source LDS distance from 8 to 4μm with a fixed gate length LG=2μm, it not only can improve the DC properties but also increase the cut off frequency (fT) of unity current gain from 27.8GHz to 28.6GHz. Furthermore, the leakage current is decreased from 10-4A to10-10A by sputtering silicon oxide, and the fT is increased to 30GHz with LDS=2μm. Finally, we discussed the current collapse effect of the transistors.

並列關鍵字

AlGaN/GaN ； AlGaN/GaN MOS-HEMTs ； PEC method

參考文獻

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