以鎳薄膜除潤現象製作多孔遮罩成長氮化鎵厚膜之研究

Abstract

本論文提出一個新的製程方法製作多孔二氧化矽，來做為磊晶側向成長的遮罩(ELOG mask)。經過快速熱退火處理，我們觀察到鍍在二氧化矽上的鎳金屬薄膜由於除潤現象，形成孔洞大小為奈米或微米等級的多孔鎳薄膜。孔洞的大小會隨著退火條件及薄膜厚度的不同而改變。利用多孔鎳薄膜做為蝕刻遮罩，可以製作出多孔之二氧化矽。接著利用氫化物氣相磊晶法成長150~200μm的氮化鎵厚膜。由側面微拉曼光譜量測結果證明，利用多孔二氧化矽模板成長之氮化鎵厚膜，其與藍寶石基板之界面有應力的釋放，且界面的殘餘應力較利用條狀二氧化矽模板成長之氮化鎵厚膜小。藉由蝕刻孔洞密度估計缺陷密度約4.4x107/cm2

In this work, we propose a new process to fabricate porous SiO2 as epitaxial lateral overgrowth (ELOG) mask. Nanometer or micrometer scale porous Ni film formed by the dewetting of two-dimensional Ni film on SiO2 during rapid thermal annealing was investigated. The hole size varied by different annealing conditions and the thickness of the Ni film. Then porous SiO2 was fabricated by using dewetted Ni film as an etching mask. GaN with a thickness of 150~200μm was grown by hydride vapor phase epitaxy (HVPE). The strain released near the interface of the GaN thick film and the sapphire substrate by this structure was investigated by cross-sectional micro-Raman analysis. The residue strain near the interface of the sample grown on the porous SiO2 template was less than that of which grown on the stripe patterned one. The dislocation density of 4.4x107/cm2 was estimated by the etching pit density.