以傾斜型閘極改善氮化鋁鎵/氮化鎵高電子遷移率電晶體之崩潰電壓及可靠性

Abstract

氮化鋁鎵/氮化鎵高電子遷移率電晶體已經被廣泛研究,並證實其在高頻功率應用有極佳之性能。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，傾斜型閘極亦可視為一個整合型電場板，其在提升功率元件特性上極為有效。本研究以電腦模擬與元件實作雙方面比較標準閘極與傾斜型閘極之特性差異，其中利用元件模擬針對閘極作幾何結構調變,得出最佳邊壁傾斜角度之閘極結構，並以深紫外光微影製作傾斜型閘極於氮化鋁鎵/氮化鎵高電子遷移率電晶體，以與模擬結果作映證。本實驗於矽基板上製作傾斜式閘極氮化鋁鎵/氮化鎵高電子遷移率電晶體,製作出元件具有120 mS/mm 最大轉導，其中崩潰電壓由130 V提升至200 V。在經由對閘極偏壓應力之測試項目,探討功率元件可靠性中，證實傾斜型閘極結構比之標準閘極結構具有較平緩之電流衰減速率以及較高效率之回復特性，在長時間操作下具有優良之功率輸出可靠性。

AlGaN/GaN HEMTs have been widely investigated and demonstrated for its capability for high-frequency with power applications. For breakdown voltage improvement, field plate structures are generally used in GaN power HEMTs. Through a well design of device configuration, the slant-gate is equivalent to an integrated field plate that can be used to improve the performance of the power device. In this study, both computer simulation results and device test results were compared for normal gate and slant-gate devices. The gate geometry was modified according to the simulation to get a vintage slanted sidewall gate structure, and AlGaN/GaN HEMTs with slant-gate have been fabricated by deep-UV lithography to verify the simulation results. The fabricated slant-gate AlGaN/GaN HEMT on Si substrate exhibited a maximum transconductance of 120 mS/mm, and the breakdown voltage was increased from 130 V to 200 V. Bias stress test was performed to investigate the reliability of the power device, it‘s verified that slant-gate structure has only slightly current degradation rate and is more effective for the current recovery as compared with the normal gate device, and it means that the slant-gate device has better reliability for long time operating as compared to the normal gate device.