具深槽源極孔洞之氮化鋁鎵/氮化鎵高電子遷移率電晶體電流崩塌特性分析

Current Collapse Characterizations of GaN-on-Si HEMTs With Deep Trench Source Via

楊季璇(Ji-Xuan Yang)

指導教授 ： 黃建璋

國立臺灣大學/電機資訊學院/光電工程學研究所/碩士(2020年)

https://doi.org/10.6342/NTU202002360

摘要

氮化鋁鎵/氮化鎵高電子遷移率電晶體擁有高能帶及高電子遷移率的材料特性，使其大量應用於高電壓電子元件以及高效率電源轉換系統；異質接合結構所產生的大量二維電子氣，更能提供元件大電流、低阻抗之特性。然而，由於傳統氮化鋁鎵/氮化鎵高電子遷移率電晶體為在高速切換下，材料缺陷所造成的漏電流以及電流崩塌效應使得電晶體無法達到所預期之高效率電能轉換，降低了元件的效能。本研究致力於探討局部移除矽基板及深槽源極孔洞結構在不同操作電壓下的電流坍塌現象的表現。
在此研究中，我們探討氮化鋁鎵/氮化鎵高電子遷移率電晶體在局部移除矽基板之後的特性。藉由霍爾量測和拉曼量測，研究發現材料在移除矽基板之後並不會有負面影響; 然而，因為移除良好導熱性的矽基板，電晶體遇到更嚴重的熱效應導致電流下降。接著我們探討電子陷阱的捕獲效應，結果指出挖除基板後能夠大幅抑制電流崩塌效應。
下一步我們研究出有效利用深槽源極孔洞的氮化鋁鎵/氮化鎵高電子遷移率電晶體轉換效率提升之方法，同時探討電流坍塌現象之影響，藉由直流特性發現，在具孔洞的結構下，直流汲極電流有些微增加，然而接著我們探討電子陷阱的捕獲效應，透過動態導通電阻分析缺陷捕捉機制，量測結果指出具源極深槽孔洞的結構，能抑制電流崩塌效應。

關鍵字

高電子遷移率電晶體 ； 電流坍塌現象 ； 矽基板移除技術 ； 深槽源極孔洞

並列摘要

The applications of GaN HEMTs have become more and more important in recent years. The AlGaN/GaN HEMTs have the material characteristics of wide-band-gap and high electron mobility, making it widely used in high voltage electronics and high efficiency power conversion systems. The heterojunction structure produces a large number of two dimensional electron gas can provide the electronics with high current and low on-resistance. However, because the traditional AlGaN/GaN HEMTs are under high-speed switching, the leakage current and current collapse caused by material defects make the transistor unable to achieve the expected high-efficiency power conversion, which reduces the performance of the electronics. This research is devoted to exploring the performance of the current collapse phenomenon of local silicon substrate removal and deep trench source via structure under different operating voltages.
In this thesis, we aim to study the electrical properties of conventional AlGaN/GaN/Si HEMTs after local removal of Si substrate. Through Hall measurement and Raman spectroscopy analysis, it can be determined that the material properties of the epi structure remain unchanged after the silicon substrate removal. However, device with Si removal incur severe self-heating effect since air possesses lower thermal conductivity compared to Si. We also investigate the trapping effect and concluded that due to the reduction of buffer taps, the current collapse can be effectively suppressed after Si removal due to decrease of buffer tapping.
Next, we construct AlGaN/GaN HEMTs with deep trench source via. We aim to investigate electrical properties of AlGaN/GaN HEMTs. The drain current of HEMTs with deep trench source via slightly increase because of direct source metal contact with the 2DEG, better current spreading path and heat dissipation from the source trench. Furthermore, we characterized current collapse phenomenon of deep trench source via HEMTs. This research presents the analysis of current collapse, dynamic on-resistance and transient response of drain current to understand the role of deep trench source via HEMTs in the charge trapping and detrapping process.

並列關鍵字

GaN-on-Si HEMTs, ； current collapse ； substrate removal ； deep trench source via

參考文獻

[1] U. K. Mishra, P. Parikh, and W. Yi-Feng, "AlGaN/GaN HEMTs-an overview of device operation and applications," Proceedings of the IEEE, vol. 90, no. 6, pp. 1022-1031, 2002, doi: 10.1109/JPROC.2002.1021567.

[2] J. Millц║n, P. Godignon, X. Perpiц╠ц═, A. Pц╘rez-Tomц║s, and J. Rebollo, "A Survey of Wide Bandgap Power Semiconductor Devices," IEEE Transactions on Power Electronics, vol. 29, no. 5, pp. 2155-2163, 2014, doi: 10.1109/TPEL.2013.2268900.

[3] M. Trivedi and K. Shenai, "Performance evaluation of high-power wide band-gap semiconductor rectifiers," Journal of Applied Physics, vol. 85, no. 9, pp. 6889-6897, 1999/05/01 1999, doi: 10.1063/1.370208.

[4] Y. Zhang, S. Feng, H. Zhu, J. Zhang, and B. Deng, "Two-dimensional transient simulations of the self-heating effects in GaN-based HEMTs," Microelectronics Reliability, vol. 53, no. 5, pp. 694-700, 2013/05/01/ 2013, doi: https://doi.org/10.1016/j.microrel.2013.02.004.

[5] O. Ambacher et al., "Two-dimensional electron gases induced by spontaneous and piezoelectric polarization charges in N- and Ga-face AlGaN/GaN heterostructures," Journal of Applied Physics, vol. 85, no. 6, pp. 3222-3233, 1999/03/15 1999, doi: 10.1063/1.369664.