氮化鎵基板表面化學拋光製成之研究

Abstract

本論文為研究氮化鎵表面超拋光之製成與其表面粗糙度之變化，其目標在於製作一個可供再成長用之氮化鎵基板。再使用雷射剝離系統製作獨立式氮化鎵基板後，利用機械研磨使其表面平坦化，讓表面粗糙度將至2nm並測其移除率，接著我們利用化學機械研磨，使用二氧化矽的奈米顆粒之懸浮液作為拋光液搭配檸檬酸跟次氯酸鈉或者氫氧化鈉跟次氯酸鈉，藉由改變製程參數，以歸納出最佳化的製程條件，最後利用細微化學機械研磨，使表面粗糙度能夠降至1nm以下，在3x3 um2 更可達0.5nm，透過AFM、PL、XRD的量測，我們對於獨立式氮化鎵基板的晶格品質更有信心。

In this work , the relation between the process of polish and the micro-roughness on the surface of GaN substrate was the purpose we studied. The major purpose of this study is to develop the process of fabricating the GaN substrate suitable for epitaxial purpose for industrial applications. After we fabricated free-standing GaN thick film using laser lift-off technique, we planarized GaN with mechanical polish. The polished surface produced a root-mean-square surface roughness of 2 nm and we got removal rate. We made use of the technology of the chemical mechanical polish, which taking the colloidal silica solution with Slurries of C6H8O7 and NaOCl(or KOH and NaOCl) as the polishing solution,and then summed up the optimum process condition by changing the process parameters. Finally, with fine chemical mechanical polish step, the RMS roughness less than 1nm, and roughness of 0.5 nm on a 3X3 um2 scan area. Therefore, we are more confident with the quality of free-standing GaN substrate which is verified by AFM、PL and XRD.