氮化鋁鎵/氮化鎵高電子遷移率場效電晶體元件結構與鈍化方式對高頻率及高功率之特性分析; Effect of Layer Structure and Passivation on High Frequency and High Power Characteristics in AlGaN/GaN HEMTs

NCU Institutional Repository > 資訊電機學院 > 電機工程研究所 > 博碩士論文 > Item 987654321/10419

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题名:	氮化鋁鎵/氮化鎵高電子遷移率場效電晶體元件結構與鈍化方式對高頻率及高功率之特性分析;Effect of Layer Structure and Passivation on High Frequency and High Power Characteristics in AlGaN/GaN HEMTs
作者:	余湘璘;Hsiang-Lin Yu
贡献者:	電機工程研究所
关键词:	氮化鎵;高電子遷移率場效電晶體;鈍化層;堀入式閘極;High power;Passivation;Recessed Gate;HEMT;AlGaN/GaN
日期:	2009-07-03
上传时间:	2009-09-22 12:16:16 (UTC+8)
出版者:	國立中央大學圖書館
摘要:	氮化鋁鎵/氮化鎵高速電子遷移率場效電晶體(AlGaN/GaN HEMT)，由於擁有卓越的載子傳輸特性，因此常被應用在高功率、高溫度以及高頻率的電路操作中。如何最佳化元件結構以及鈍化製程發展即為此篇論文的重點敘述。在最佳化元件結構部份，我們探討不同元件結構對於元件特性的影響，包括堀入式閘極、高掺雜表面層於歐姆接點及低串聯寄生電阻結構－搭配發展出電子束微影製程，驗證了AlGaN/GaN HEMT次微米元件優異之微波功率性能，在高頻特性部分，電流增益截止頻率(fT)與閘極長度(LG)的乘積可以高達20 GHz-um。在元件鈍化層製程的最佳化部份，我們提出一種可同時成功提昇元件高頻及功率特性的鈍化層覆蓋方式，在移除高摻雜層後馬上覆蓋鈍化層Si3N4或是SiO2，相較於傳統方式鈍化之元件，明顯改善了元件表面與鈍化層介面特性，成功抑制缺陷效應所造成的電流侷限。就功率元件因為基板散熱不佳而造成自我發熱的問題，我們利用不同閘極寬度並聯大功率元件，從電性上退化的探討證明散熱對於高功率元件的重要性，並利用紅外線熱影像分析了元件操作時表面溫度的分布。 AlGaN/GaN HEMTs have attracted great interest for high-power, high-temperature, and high-frequency applications because of their superior carrier transport properties. This thesis focuses on optimization of device structure and passivation process, and their correlation with device performance. Based on the same epitaxy materials, we investigated the effect of different Al0.26Ga0.74N/GaN HEMT device structure on DC and RF performance. Results show that n+-GaN cap kept under ohmic metals for lowering contact resistance, an appropriate gate recess depth for improving charge modulation capability, and cap removal in device access region for miminizing source resistance are determined as best structure for achiving highest frequency performance. Improved speed performance in both micron and submicron devices were demonstrated. A 0.5 um T-gate device yielded a high fT×LG product of 20 GHz-um. Plus, we reported the fabrication of AlGaN/GaN HEMT with improved DC, high frequency and microwave power performances by employing an alternative passivation approach. A pretreated AlGaN surface is provided by dry etching n+-GaN cap layer and RTA annealing ohmic contacts right before Si3N4 or SiO2 passivant was deposited. Pulsed I-V characteristics show that the pseudo in-situ passivation process successfully eliminates trapping effect at Si3N4 or SiO2 and AlGaN interface which is considered to be the important factor for the performance enhancement. The issues of the drain current collapse and the power degradation induced by the surface traps are also successfully improved. As for the issue of self heating, power devices with different layouts are addressed. Thermal IR microscopy was used to detect the device surface temperatures under various dc power consumptions.
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