在本篇論文中，我們在藍寶石基板上的氮化鎵試片製作金屬氧化物半導體場效電晶體，在P型氮化鎵上直接磊晶一層高濃度N型氮化鎵，以利源極和汲極在磊晶試片上形成歐姆接觸，實驗的目標為製做高性能掘入式閘極電晶體和改善反轉通道。
因ICP蝕刻造成掘入式閘極電晶體損傷，沒有經過適當表面處理修復表面將會無法形成反轉通道，低瓦數ICP完成之後使用TMAH為修復表面特性方式，從ICP蝕刻表面的粗糙度8.649 nm高於TMAH表面處理1小時的粗糙度1.812 nm，可知兩者的差別。而ICP低瓦數以及TMAH同時做表面處理優先製程的掘入式閘極金氧半電晶體，臨界電壓為8.25 V，最大電流密度為1.4 mA/mm，導通電阻23.55 mΩ-cm2，場效電子遷移率可達到70.70 cm2/V-s(在閘極長度為100μm)。
使用MOCVD及PAMBE兩種磊晶方式，分別製作掘入式閘極與水平式閘極，利用兩種不同元件結構，發現MOCVD元件汲極到源極漏電流小於PAMBE，推測是PAMBE磊晶因為藍寶石基板與氮化鎵晶格常數差異太大造成缺陷產生漏電流路徑。

In this study, GaN-based MOSFETs on sapphire substrates were fabricated. An epitaxial layer of high concentration n-type GaN was grown on top of p-type GaN in order to form source and drain with good ohmic contacts. The goal of this work is to demonstrate high performance recessed-gate MOSFETs and improve the inversion channel properties.
Due to the damage resulted from ICP dry etching, the channel of the recessed-gate MOSFET would be degraded without proper surface treatment to recovery. A low power ICP followed by wet etching using TMAH was adopted to recover the surface properties. The rms surface roughness was 8.649 nm after ICP process, while 1.812 nm was realized after treated with TMAH solution for an hour. The recessed-gate MOSFET with such a treatment prior to depositing aluminum oxide by ALD as a gate dielectric showed a threshold voltage of 8.25 V, a maximum drain current density higher than 1.4 mA/mm, an on-resistance of 23.55 mΩ-cm2, and a field effect mobility of 70.70 cm2/V-s(the gate length was 100μm).
Samples grown by MOCVD and PAMBE were used to fabricate recessed-gate MOSFETs and planar gate MOSFETs. It was shown that source-to-drain leakage current of sample grown by MOCVD is low than the sample grown by PAMBE, which can be attributed to phenomenon could be owing to leakage paths via conductive dislocations in PAMBE samples.

第1章序論........................................1
1.1前言.........................................1
1.2文獻回顧 .....................................3
1.3研究方向簡介與論文架構..........................10
1.3.1 研究方向簡介...............................10
1.3.2論文架構...................................10
第2章材料介紹及實驗設計............................11
2.1磊晶方式......................................11
2.1.1有機化學氣相沉積(MOCVD)......................11
2.1.2電漿輔助分子束磊晶(PAMBE).....................11
2.2 基板的選擇....................................12
2.3氮化鎵結構種類..................................12
2.4源極與汲極結構設計...............................13
2.4.1源極與汲極離子佈植.............................13
2.4.2閘極掘入方式..................................14
2.6 元件設計......................................15
第3章光罩設計及元件製程..............................18
3.1掘入式閘極與水平式閘極金氧半場效電晶體設計流程.........18
3.2蝕刻對準記號.....................................21
3.3蝕刻閘極區域與蝕刻表面N+ GaN.......................22
3.3源極與汲極離子佈植................................24
3.4源極與汲極離子佈植之活化...........................25
3.5閘極氧化層製作...................................25
3.5歐姆接觸製作.....................................26
3.6 元件隔離區域製作.................................28
3.7閘極金屬沉積.....................................29
第4章元件量測結果分析.................................30
4.1 測試元件分析.....................................30
4.1.1 TLM(Transfer Length Method)量測分析...........30
4.1.2 四點探針(Four Point Probe)量測分析..............32
4.2掘入式閘極(Recessed-Gate) MOSFET電壓-電流量測分析....34
4.2.1源極到汲極之間改善漏電分析.........................34
4.2.2 P-GaN通道基本電性..............................35
4.2.3改善基本電性方式.................................37
4.2.4閘極長度(Gate Length)電流-電壓特性比較.............40
4.3 PAMBE磊晶掘入式與水平式閘極電流-電壓特性比較...........41
4.4 不同PAMBE磊晶結構電流-電壓特性比較...................45
4.5 紫外光(UV Light)量測..............................49
4.6電子缺陷與閘極控制...................................52
第5章結論與未來工作.....................................55
參考文獻..............................................56

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