電子迴旋共振乾式蝕刻技術對金屬P型氮化鎵介面特性的影響

Abstract

本篇論文旨在探討電子迴旋共振蝕刻技術對金屬P型氮化鎵半導體介面特性的影響，利用含氯的電漿蝕刻P型氮化鎵表面，接著以快速退火及氮氣電漿後續處理蝕刻後的半導體，探討鎳金金屬與P型氮化鎵介面的電性上的變異，結果顯示出被蝕刻後的氮化鎵，由於氮的流失和表面的傷害，造成歐姆電性的劣化。但是經過攝氏七百度快速退火處理三分鐘後，雖然仍稍具整流特性，但已大為改善，同時對此條件處理之晶片，亦做X光光電子頻譜、原子作用力顯微鏡、低略角X光繞射及螢光頻譜分析，探討半導體表面化學成份、形態、晶相上的改變，結果顯示出在攝氏七百度快速退火處理後，晶片表面上會有重整現象，一改蝕刻後半導體表面的不規則狀態。然而在五百度及九百度快速退火處理後在電性上卻並沒有改善，反而更加劣化，這可由表面氮對氧的比例得到解釋。至於電子迴旋共振氮氣電漿處理，也並沒有顯現對電性上的提昇，從X光光電子頻譜和螢光頻譜分析來看，雖然氮含量有顯著的提高，但是並未緊密地鍵結在晶面上，因此一旦受熱便容易從表面上脫離。

In this study, electron cyclotron resonance reactive ion etch (ECR-RIE) was used to etch p-type GaN under chlorine-based plasma. We used rapid thermal annealing (RTA) and nitrogen plasma treatments as post-RIE process to investigate the electrical characteristics of Ni/Au contacts on p-type GaN. The results showed that RIE could deteriorate the contact property very much due to the induced nitrogen vacancies and damages on the p-type GaN surface. By using the RTA treatment at 700°C for 3 minutes, the poor contact characteristic would be improved though it still showed non-linear I-V characteristics. The results from XPS, AFM, GIXD and PL measurements indicated that RTA at 700°C treatment had the effect of reconstructing the ordered structure from the damaged p-GaN surface. However, annealing at 500°C and 900°C did not improve the contact property because of the high ratio of oxygen-to-nitrogen on the surface. On the other hand, ECR-N2 plasma treatment did not show any enhancement of the ohmic contact property. From XPS and PL analysis, the nitrogen plasma treatment could increase nitrogen vacancies as well as nitrogen content of the p-GaN surface. The increased nitrogen atoms did not form tight bonds with GaN, and easily escaped from the surface by annealing.