利用三閘極結構改善高功率鋁氮化鎵/氮化鎵高電子遷移率電晶體元件特性研究

Abstract

對於高功率開關的應用來說，降低導通電阻以降低功率損耗和輸入電容是至關重要的。而氮化鎵高電子遷移率電晶體由於二維電子氣提供了高崩潰電壓、高電子遷移率、低導通電阻與低輸入電容，正好十分適合應用在高功率元件上。此外，透過電子束微影技術的幫助下，三維三閘極結構得以成功的完成製程。三維三閘極結構不僅比傳統的平面結構有著更良好的電性控制能力，使得元件可以有更快的切換速率和更低的導通電阻。另一方面，也能針對短通道效應像是次臨界擺幅、汲極感應勢壘降低等現象更是有顯著的改善。 本篇論文主要是針對氮化鎵高電子遷移率電晶體的三維三閘極結構製成的改良與討論。三維三閘極成型最關鍵的兩個變數便是三維鰭狀結構的深度與高度。我們的目標就是找到最佳化的製程條件，尤其是針對鰭狀結構的深度與高度作一系列的探討。最終成功做出有著低導通電阻，並且最適合高功率開關應用的元件。

For power switching applications, it is necessary to reduce the on-resistance to minimize the power losses and input capacitance. Therefore, AlGaN/GaN HEMTs is suitable for high power application due to high breakdown voltage and high mobility provided by the 2-DEG further reduces the on-resistance, together with the high channel density brought by the large band discontinuity and the polarization field. A HEMT structure also leads to low input capacitance, because the 2-DEG can be generated without doping the AlGaN layer. Furthermore, by double Electron beam lithography and etching, 3-D structure HEMTs that increase the area between gate and channel has been successfully fabricated. The 3-D tri-gate structure, which has better electrostatic control compared to planar-type transistors, especially for the short-channel case, not only is used for the suppression of short channel effects such as subthreshold swing (SS) and drain-induced barrier lowering (DIBL), but also offering the potential of very low on-resistance and higher switching speed This study would focus on the device fabrication of trigate AlGaN/GaN HEMTs with low ON resistance, low subthreshold swing and high ON-OFF ratio for power switch applications. In order to do so, our goal is to find optimized condition of trigate AlGaN/GaN HEMTs with variable etching depth, fin width and drain-source spacing.