具體溝槽結構之半垂直式氮化鎵溝槽閘極金氧半場效電晶體之電性分析

Abstract

本論文著重於具體溝槽結構之半垂直式氮化鎵溝槽閘極金氧半場效電晶體進行製程開發與電性分析。藉由採用體溝槽結構，可強化閘極對通道區的控制能力，並有效降低元件於反向導通狀態下之導通電壓與阻抗，以提升元件性能與穩定性。 本研究製作具體溝槽與無體溝槽之元件，並進行電流–電壓與電容–電壓特性量測。實驗結果指出，體溝槽可有效降低臨界電壓、改善次臨界擺幅，並減緩閘極電壓正反掃描後所產生之遲滯現象；電容–電壓特性分析亦說明界面陷阱密度有所降低。進一步比較不同體溝槽尺寸對元件電性之影響，實驗結果顯示，雖導通電流略有下降，但在臨界電壓、次臨界擺幅與遲滯效應方面，隨尺寸增加而顯著改善。透過元件模擬分析亦證實，體溝槽有助於閘極所誘發電場的橫向擴散，電場分佈得以延展至更深層區域，緩解集中於閘極氧化層邊緣的電場強度，提升場控均勻性，進而降低界面陷阱與遲滯現象。 此外，本研究亦探討第三象限操作下之反向導通量測，結果顯示體溝槽結構有助於改善反向導通機制，使導通電流提升三個數量級，展現優異反向導通表現。綜合實驗與模擬結果，體溝槽結構於提升元件性能與穩定操作方面展現高度潛力，具後續應用與設計參考價值。

This work investigates the fabrication and electrical performance of quasi-vertical GaN trench-gate metal-oxide-semiconductor field-effect transistors (MOSFETs) with a body trench structure. By adopting the body trench design, gate control over the channel region is enhanced, and both the conduction voltage and resistance during reverse conduction are reduced, thereby improving device performance and stability. Devices with and without the body trench were fabricated, and their electrical characteristics were evaluated through current–voltage (I–V) and capacitance–voltage (C–V) measurements. The experimental findings demonstrate that introducing a body trench leads to a lower threshold voltage (VTH), improved subthreshold swing (SS), and reduced hysteresis (ΔVTH) between forward and reverse gate sweeps. Capacitance–voltage analysis also shows a significant reduction in interface trap density (Dit). The impact of varying body trench dimensions on device characteristics was also analyzed. Results show that although increased trench size slightly decreases the on-state current, it provides better performance in threshold voltage, subthreshold swing, and hysteresis suppression. Simulation analysis further confirms that the body trench facilitates lateral spreading of the gate-induced electric field, allowing the field to extend into deeper into the p-GaN layer. This redistribution mitigates electric field crowding at the gate oxide edge, leading to enhanced field uniformity, suppressed interface traps, and reduced hysteresis effects. Moreover, third-quadrant reverse conduction measurements also demonstrate that the body trench significantly improves the reverse conduction mechanism, increasing the conduction current by approximately three orders of magnitude and exhibiting excellent reverse conduction characteristics. Based on experimental and simulation results, the body trench structure shows strong potential for improving device performance and operational stability, offering valuable reference for future applications and design.