臺灣博碩士論文加值系統

本論文的研究係利用電子束微影與回流法製備具有次微米T型閘極的變異結構高電子遷移率電晶體(MHEMT)，這種電晶體可以使用於提高頻率(>100GHz)。此研究之In0.53Ga0.47As/InAlAs高電子遷移率電晶體利用InxAl1-xAs作為砷化鎵基板與磷化銦HEMT結構的緩衝層；並藉回流法與電子束微影獲得0.15μm的閘極長度。製備完成的電晶體具有200mA/mm的汲極飽和電流在1.2V源極汲極偏壓下互導係數高達有750mS/mm。雜訊方面，160μm的元件在18GHz的狀態下具有小於1dB的雜訊值及高達13.5dB增益值。元件的電流增益截止頻率以及最大震盪頻率分別到達154GHz與350GHz。此研究所研發出之變異結構高電子遷移率電晶體極適於高頻低雜訊的元件應用。

A metamorphic high electron-mobility transistor (MHEMT) fabricated with reflowed submicron T-gate using E-beam lithography for high frequency electronics application is developed in this study. The In0.53Ga0.47As/InAlAs MHEMT uses InxAl1-xAs as the buffer layer between GaAs substrate and the InP lattice-matched HEMT structure. The reflowed T-gate has a gate length of 0.15μm. The fabricated metamorphic HEMT has a saturation drain current of 200mA/mm and a transconductance of 750mS/mm at VDS=1.2V. The noise figure of a 160μm gate-width device is less than 1dB and the associated gain is up to 13.5dB at 18GHz. This device demonstrates a cut-off frequency fT of 154 GHz and a maximum frequency of oscillation fmax up to 350GHz. The metamorphic HEMT developed in this study has the potential for high frequency low noise applications.

Content
Abstract(Chinese)
Abstract(English)
Acknowledgement
Content
Table Captions
Figure Captions
Chapter 1 Introduction 01
1.1 Motivation for this 01
1.2 Dissertation content 02
Chapter 2 Literature Review 04
2.1 Comparisons of MHEMT, PHEMT and InP HEMT 04
2.2 Selective Etch in Gate Recess 06
2.3 Technologies for Gate Shrinkage 07
2.4 Summary 09
Chapter 3 Experiment and procedures 10
3.1 Device structure 10
3.2 Experiments of Reflow Gate 11
3.2.1 Test sample preparation 11
3.2.2 Reflow procedures and measurements 11
3.3 Device fabrication 12
3.3.1 Wafer cleaning 12
3.3.2 Device isolation 12
3.3.4 Ohmic contact formation 13
3.3.4 Selective etching for gate recess & T-gate formation 14
3.3.5 Device passivation & Contact via 15
3.3.6 Airbridge formation 16
3.4 Characteristic & Measurements 16
3.4.1 Ohmic Contact 17
3.4.2 Current-voltage curve & pinch off voltage 18
3.4.3 Breakdown voltage (VB) 18
3.4.4 Transconductance (Gm) 19
3.4.5 S-parameter 19
3.4.6 Noise figure 20
Chapter 4 Results and Discussions 21
4.1 Reflowed T-gate Test 21
4.2 Mesa Isolation & Ohmic Contact 22
4.3 Gate Recess & Gate Metallization 23
4.4 Au Plating Airbridge Formation 23
4.5 DC characteristics of the MHEMT 23
4.5.1 I-V characteristic for MHEMT 23
4.5.2 Breakdown Voltage (VB) 24
4.5.3 Transconductance (Gm) 24
4.6 RF characteristics of the MHEMT 25
4.6.1 Unit Current Gain Cutoff Frequency (fT) & Maximum Frequency of Oscillation (fmax) 25
4.6.2 Noise figure (NF) 26
4.7 Discussion 27
Chapter 5 Conclusions 28
Reference 30
Table
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