利用雷射剝離技術製作獨立式氮化鎵基板之研究

Abstract

本論文利用雷射剝離系統製作獨立式氮化鎵基板，由這個實驗中我們得到幾個關鍵的結論，在1.5吋的氮化鎵厚膜上成功的完成剝 離，表面完整沒有明顯裂痕，並且在特定的厚度限制下，有相當高的的成功率 ，而在雷射光斑面積與掃描軌跡上也透過不同的條件測試而發現最適合的参數，並在1.8吋的獨立式氮化鎵板也有成功剝離的例子，其實在更大面積的氮化鎵厚膜剝離上仍然有很大的潛力，但是也需要HVPE磊晶能力的同步配合，同時透過不同降溫速率條件下完成的厚膜剝離，由量測發現，在粗糙度，應力釋放上有明顯的差異，但不影響晶格品質，這讓我們對於雷射剝離對厚膜材料的影響有更進一步的了解，由儀器驗證氮化鎵厚膜從基板上剝離後，晶格品質獲得明顯的改善，應力也獲得釋放，整個厚膜也處於近乎無應力累積的狀態 ，透過PL、XRD的量測我們對於獨立式氮化鎵厚膜的晶格品質更有信心，也從PL與Raman的量測中觀察到應力在氮化鎵厚膜上的作用，對於應力的了解可以讓我們在往後的剝離實驗中降低因為應力而造成崩裂的風險。

In this work we fabricated free-standing GaN thick film using laser lift-off technique，and we obtained some important results from this work ; first，we successfully fabricated 1.5 inch free-standing GaN thick film，which are complete and without obvious crack，the probability of successful fabrication is very stable as long as it was followed by certain thickness limit ; the most proper recipe of laser beam size and scan trace was obtained through different experiment conditions，a few amounts of 1.8 inch free-standing GaN thick film was also successfully lift-off from sapphire，it shows that there has chance on larger size GaN thick film ; with different cool down conditions，we observed the difference in roughness and residual stress on GaN，but without effect in crystal quality，it helps us more realize the effect on GaN by LLO ; the crystal quality was improved after LLO which was verified by certain instrument，and the stress also get released after LLO，whole GaN thick film was nearly strain free ; we have confidence with the quality of free-standing GaN thick film which is verified by PL and XRD，we also observed the stress distribution in whole GaN thick film by PL and Raman，it helps us to prevent GaN thick film crack during LLO process which caused by stress。