高崩潰電壓氮化鋁鎵/氮化鎵金屬-絕緣層-半導體場效電晶體之研製

Growth and Fabrication of High Breakdown Voltage AlGaN/GaN Metal-Insulator-Semiconductor Field Effect Transistors

鮑建佑(Chien-Yu Pao)

指導教授 ： 綦振瀛

國立中央大學/資訊電機學院/電機工程學系/碩士(2014年)

摘要

本論文主要為探討利用MOCVD磊晶的方式來提升其金屬-絕緣層-半導體場效電晶體之截止區崩潰特性。首先藉由增加緩衝層厚度的方式提升其元件截止區特性，在氮化鎵緩衝層厚度為4.6 μm，閘極至汲極間距為20 μm的規格下獲得元件截止區崩潰電壓960 V，因試片邊緣裂縫區域過大使磊晶試片有效面積降為65%，因此將研究重心轉變為如何降低磊晶層厚度並維持相同元件特性；根據文獻搜尋結果和MOCVD機台限制選擇使用鋁含量為5%之氮化鋁鎵作為緩衝層材料，並與氮化鎵緩衝層進行比較，在相同緩衝層厚度的情況下，氮化鎵之元件截止區崩潰電壓為795 V，氮化鋁鎵則為705 V，而從截止區電壓電流特性來看，氮化鋁鎵緩衝層之漏電流明顯大於氮化鎵，其原因為氮化鋁鎵磊晶層缺陷密度過高所致，其MOCVD之磊晶參數尚待調整。
根據前段結論，元件截止區特性皆會受到磊晶層缺陷密度影響，因此設計新結構:利用低溫成長之氮化鋁薄鏌提升其上之氮化鎵緩衝層品質，在相同的元件規格之下，未使用低溫成長氮化鋁薄鏌之元件截止區崩潰電壓為795 V，而在氮化鎵間插入低溫成長氮化鋁薄鏌之元件截止區崩潰電壓達926 V，提升幅度約16%。除了元件特性提升之外，截止區特性滿足空間電荷限制電流理論進一步釐清截止區電流曲線之成因。

關鍵字

氮化鎵 ； 功率元件

並列摘要

This thesis focus on the enhancement of off-state breakdown voltage of AlGaN/GaN Metal-Insulator-Semiconductor Field Effect Transistors (MIS-FETs) by using MOCVD grown different epitaxy structures on Si.
With increasing GaN buffer layer up to 4.6 μm thick, the fabricated AlGaN/GaN MIS-FETs off-state breakdown voltage is up to 960 V at LGD = 20 μm, while the 2.5 μm GaN thick buffer layer has 795 V device breakdown voltage. However, with increasing buffer layer thickness, the edge crack extends to 1.5 cm, which means only 65% area of 6-inch silicon substrate is available. For the purpose of enhance wafer area efficiency, several ways were surveyed to improve devices characteristics without extend buffer layers thickness. The first selection is 5% Al-content AlGaN as buffer layer. 5% AlGaN has off-state breakdown 705 V while GaN buffer layer equips 795 V, which was because dislocation densities serious affect off-state leakage path and breakdown voltage, growth condition of 5% AlGaN need to be optimized.
From previous results, that is the dislocation densities seriously affect device off-state characteristics, the growth of AlN interlayer experiment was designed for enhancing epitaxial quality. Which improved the devices breakdown voltage from 795 V to 926 V, about 16% breakdown voltage enhancement. Furthermore, off-state I-V curve of the devices fitted the theory of Space Charge Limited Current, which advanced understanding of the cause of the devices off-state leakage current formation.

並列關鍵字

MOCVD ； HEMTs

參考文獻

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