本篇論文主要在研製準垂直型溝槽式氮化鎵金氧半場效電晶體於藍寶石基板。藉由高解析度X光電子能譜分析，可以發現經由感應式耦合電漿蝕刻後會使得Ga 2p3/2元素訊號的峰值位移，指出其材料表面遭受破壞，為了解決表面破壞的情形，本論文採取Digital Etch(D.E)的蝕刻方式進行表面處理，且探討晶面及D.E表面處理對元件特性的影響。
本論文採用不同表面處理方式，分別為：(a)浸泡鹽酸、BOE與硫酸，(b)在200oC環境下進行10次的D.E，(c)在200oC環境下進行20次的D.E，(d)在200oC環境下進行20次的D.E搭配浸泡酸液，及(e)在450oC環境下進行20 次的D.E搭配浸泡酸液。
由量測結果得知，即使經過不同條件的表面處理，蝕刻過後的溝槽表面仍存在許多的陷阱，必須使用脈衝模式及搭配UV光照射的量測方式，才可以得到合理的輸出特性，整體而言，元件在200oC環境下進行20次的D.E表面處理過後可得到最佳的元件特性，該臨界電壓為5.5 V、最大汲極電流密度達0.83 A/mm2，經計算後的場效遷移率僅有4.8 (cm2/V-s)。

In this study, quasi-vertical trench gate of the gallium nitride (GaN) MOSFETs were fabricated on sapphire substrate. From high-resolution X-ray photoelectron spectroscopy (HR-XPS) analysis, it was found that the Ga 2p3/2 peak was shifted by the etching of inductive coupling plasma, which indicates that the surface was damaged. In order to recover the surface properties, the treatment of digital etch (D.E) on the surface was carried out.
Five samples with quasi-vertical MOSFETs going through different surface treatments listed as the following were completed and compared: (a) soaking in hydrochloric acid, BOE and sulfuric acid. (b) 10 cycles of D.E at 200 °C (c) D.E for 20 cycles in a 200 °C environment. (d) 20 cycles of D.E at 200 °C with soaking in acids. (e) 20 cycles of D.E at 450 °C with soaking in acids.
From the measurements, it was discovered that even though the surface had been through different treatments, there might still exist a lot of traps on the etched trench surface. Pulse mode must be used in measurements together with UV light on in order to obtain reasonable output characteristics. Overall, the device treated with 20 cycles of digital etch at 200 ° C has the best device characteristics. With a threshold voltage (Vth) of 5.5 V and a maximum drain current density of 0.83 A/mm2, the calculated mobility is only 4.8 (cm2/V-s).

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