以深紫外光微影製作具傾斜型電場板之氮化鋁鎵/氮化鎵高電子遷移率電晶體

Abstract

氮化鋁鎵/氮化鎵高電子遷移率電晶體已經被廣泛研究並證明其高頻功率應用之能力。為了增加元件的崩潰電壓，電場板結構普遍被使用於氮化鎵功率元件。在適當的結構設計下，T型閘極亦可視為一整合型電場板，並兼具元件高速操作的優點。然而電子束微影的使用提高了製造成本，不利大量生產。本研究成功利用深紫外光微影製作傾斜型電場板於氮化鋁鎵/氮化鎵高電子遷移率電晶體。論文中提出一個簡單並兼具成本效益之傾斜式電場板製作方法，以斜向曝光微影技術形成具傾斜側壁之次微米T型閘極。為了進一步降低製造成本，亦使用成長於矽基板之氮化鎵結構。製作於矽基板上的0.6 × 100μm2 傾斜式電場板氮化鋁鎵/氮化鎵高電子遷移率電晶體具有214 mS/mm 最大導轉及122 V崩潰電壓；於高頻量測結果中展現24 GHz電流增益截止頻率及49 GHz最大振盪頻率，並且在8 GHz下具有高達5.0 W/mm之輸出功率。

AlGaN/GaN HEMTs have been widely investigated and demonstrated for their capabilities on high-frequency power applications. In order to improve the breakdown voltage of the device, field plate structure is generally used in GaN power HEMTs. Through a well designed device configuration, the T-shaped gate can be equivalent to an integrated field plate. However, the adoption of e-beam lithography increases the production cost. It’s unfavorable for mass production. In this work, AlGaN/GaN HEMTs with slant field plate have been successfully fabricated using deep-UV lithography. A simple and cost-effective way for slant field plate fabrication has been proposed. By using an angle exposure technique, submicron T-shaped gates with slant sidewalls were achieved. To further reduce the production cost, the GaN-on-Si substrate was also used. The 0.6 × 100μm2 slant-field-plated AlGaN/GaN HEMT on silicon substrate exhibited a peak value of transconductance of 214 mS/mm and a breakdown voltage of 122 V. Through high-frequency measurements, the device revealed a current gain cut-off frequency ( fT ) of 24 GHz, a maximum oscillation frequency ( fmax ) of 49 GHz and an output power of 5.0 W/mm at 8 GHz.