Study on Warping Effect of GaN Thick Films : Origin and Reduction
|摘要:||本論文藉由氫化物氣相磊晶技術(HVPE)與雷射剝離(LLO)系統來探討氮化鎵厚膜其曲翹之特性。在LLO前，經由不同條件異質磊晶成長氮化鎵厚膜，我們觀察到其曲率會隨成長厚度、基板厚度或高溫層所佔比例等條件的不同而改變。在LLO後，曲率會因應力的釋放而大為改善。此外，發現其曲率會隨著基板厚度與高溫層所佔比例的不同而改變。並藉由不同高溫層比例的調變，會有著不同曲翹方向的出現。經計算可得，理論上當高溫層比例達31.37 % 時，其曲率會趨近於零，小於此比例其彎曲方向會呈convex-bowing，大於此比例則會呈現concave-bowing的狀態。我們利用ICP蝕刻背面的方式，成功且有效率的將樣品之曲率從0.675降至0.038 m-1，其XRD半高寬也從192降至97 arcsec，幾乎完全的消除因彎曲造成之效應。|
In this work, we investigated the warping properties of GaN Thick film by HVPE and laser lift-off system. Before LLO, the curvature of hetero-epitaxial GaN varied by different growth conditions, such as the thickness of GaN and substrates, and the percentage of high temperature layer. After LLO, the curvature of free-standing GaN would greatly reduce by the relaxation of stress. Furthermore, the curvature of free-standing GaN varied by different conditions,such as the thickness of substrates and the percentage of high temperature layer. Different directions of warping would emerge by using modulations of the percentage of high temperature layer. Theoretically, the curvature of free-standing GaN would approach zero when the percentage of high temperature layer is 31.37 %. If the percentage is smaller than 31.37 %, the direction of warpage would present convex-bowing. Conversely, the direction of warpage would present concave-bowing if the percentage is greater than 31.37%. We reduce the curvature of GaN from 0.675 to 0.038 m-1 effectively by using ICP etching GaN N-face. Its XRD FWHM also reduced from 192 to 97 arcsec. The warping effect was eliminated through the way completely.
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