利用多層堆疊氧化鉿/氧化鑭為閘極絕緣層以提升增強型氮化鎵金屬-絕緣體-半導體高電子遷移率電晶體起始電壓之穩定性

Abstract

由於能提供系統安全以及簡化電路之設計，因此氮化鎵增強型高電子遷移率電晶體在近幾年廣受注目；為了因應系統對於元件特性的嚴苛需求，如較高的閘極電壓擺幅、較低的閘極漏電流、較正偏的起始電壓，使得在閘極金屬與半導體間增加絕緣層為現今高功率元件開發研究之主流，以期始元件能達到這些目標。然而，當增強型氮化鎵金屬-絕緣體-半導體高電子遷移率電晶體在操作時，以及閘極在高正偏壓下，二維電子氣通道的電子會被閘極吸引而進入在絕緣體與半導體之間的深層能階，進一步造成起始電壓的不穩定性和遲滯效應，並影響到增強型氮化鎵金屬-絕緣體-半導體高電子遷移率電晶體元件的輸出電性表現。 由於氧化鉿鑭可以有效地減少氧缺陷密度，因此在此研究中，我們將利用多層堆疊的氧化鉿/氧化鑭來當作閘極絕緣層，藉此改善起始電壓的不穩定性，並應用在閘極嵌入式增強型氮化鎵金屬-絕緣體-半導體高電子遷移率電晶體之製作，以探討將此氧化鉿鑭作為閘極絕緣層對於閘極嵌入式增強型金屬-絕緣體-半導體高電子遷移率電晶體在閘極漏電對於元件的輸出電性表現的影響、崩潰電壓的提升以及高汲極偏壓元件之動態電阻的穩定度改善，研究結果最後驗證多層堆疊氧化鉿/氧化鑭閘極嵌入式增強型氮化鎵金屬-絕緣體-半導體高電子遷移率電晶體之元件非常適用於高功率元件。

It is necessary to have enhancement-mode (E-mode) AlGaN/GaN high electron mobility transistors (HEMTs) in views of safety issue and simple design on the circuit. AlGaN/GaN E-mode HEMTs has been extensively studied in recent years. In order to improve performance of E-mode device, gate insulator was added between metal and semiconductor to get some goals, such as higher gate voltage swing, lower gate leakage current or more positive threshold voltage and it had become the mainstream of high power device development. However, when the E-mode AlGaN/GaN MIS-HEMTs are used for high power device, the high positive gate voltage may induce the electrons in the 2DEG channel into the deep states at the interface between insulator and AlGaN layer, and results in the threshold voltage instability and hysteresis effect. It would influence the output performance of E-mode MIS-HEMT device. Due to the oxygen vacancy density reduction in HfLaO, it is proven by some references. In this study, we applied multilayer HfO2/La2O3 to be gate insulator in the fabrication of a gate recessed AlGaN/GaN MIS-HEMT and hoped to improve Vth instability effectively. To investigate the gate leakage current influence on the output performance, the breakdown voltage improvement and the dynamic on-resistance stability under high drain voltage of the gate recessed HfO2/La2O3 E-mode AlGaN/GaN MISHEMT. From these measurements, we found the gate recessed HfO2/La2O3 E-mode AlGaN/GaN MIS-HEMT was very suitable for high power device.