藍寶石基板蝕刻機制及其應用於 發光二極體之探討;Study of wet-etching mechanism on sapphire substrate and application in the light emitting diode

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Title:	藍寶石基板蝕刻機制及其應用於發光二極體之探討;Study of wet-etching mechanism on sapphire substrate and application in the light emitting diode
Authors:	李旭峯;Li,Syu-Fong
Contributors:	化學工程與材料工程學系
Keywords:	藍寶石;蝕刻;圖案化;二極體;白光封裝;pattern sapphire substrare;etching;white LED;package
Date:	2015-07-29
Issue Date:	2015-09-23 10:52:18 (UTC+8)
Publisher:	國立中央大學
Abstract:	本論文主要探討c-plane藍寶石基板的蝕刻機制、形貌生成之影響並應用於發光二極體。過去我們認為，單晶材料的蝕刻形貌由較具抗蝕刻能力的晶格面呈現(a-plane > r-plane > c-plane)；但在此研究中發現，單晶c-plane藍寶石基板經濕蝕刻製程後，並非以特定晶格面(如: r-plane) 呈現蝕刻形貌。在第三章中，利用建立藍寶石基板原子晶格模型與各晶格面之表面能計算來探討蝕刻機制，並解釋濕蝕刻樣貌未依照晶格面抗蝕刻能力順序呈現的原因。根據第三章的討論，我們瞭解當r-plane的原子未受保護而避免被蝕刻時，蝕刻形貌將不以r-plane來呈現蝕刻形貌。除了晶體晶格面等因素之外，濕蝕刻化學反應中，其蝕刻液的種類影響蝕刻形貌甚大。第四章中，使用不同比例的硫酸與磷酸的蝕刻液，並觀察不同比例的蝕刻液對於蝕刻形貌之影響。我們發現蝕刻液比例將影響蝕刻形貌之底座彎曲程度，隨著磷酸在蝕刻液中的比例增加，蝕刻形貌底座之彎曲程度將較不顯著。藉由原子模型之建立、瞭解蝕刻液分子尺寸與考量原子坐落在不同維度，提出硫酸鋁的形成將造成空間的遮蔽效應，減緩蝕刻反應的進行，造成不同維度具有蝕刻速率差，進而影響到整體蝕刻形貌。在瞭解蝕刻機制與蝕刻液種類對於蝕刻形貌之影響後，將藍寶石基板圖案化實際應用於發光二極體。除了有效改善發光二極體之效能，我們發現不同圖案形貌將影響發光二極體的裸晶在不同空間角度之強度分佈。第五章中，將藍光發光二極體投入白光封裝製程，並探討不同基板圖案形貌對於白光發光二極體封裝效率之關西。因能量損耗在白光封裝製程無可避免，藉由改變藍光裸晶在不同空間角度的強度分佈，以減少能量損耗，達到改善白光二極體封裝效率的目的。然而，調變藍光裸晶在不同空間角度的強度分佈則可利用我們對於藍寶石基板蝕刻機制與形貌的瞭解，控制圖案形貌與c-plane之間的夾角。在此論文中，我們藉由探討無光罩c-plane 藍寶石基板的蝕刻機制與蝕刻溶液對於其蝕刻機制之影響，進而設計不同圖案化藍寶石基板形貌應用於白光二極體封裝效率之探討，掌握了圖案化藍寶石基板對於白光發光二極體效率之影響，同時使得白光發光二極體效率提升有更進一步的發展。 ;In this thesis, the etching mechanism of the c-plane sapphire substrate will be investigated. In the past, we think that the wet-etching morphology depends on etching resistance of the sapphire crystallography (a-plane > r-plane > c-plane). In this study, we found that the wet-etching morphology of the c-plane sapphire would not follow the etching resistance of the sapphire crystallography. In Chapter 3, the wet-etching mechanism and the formation of the etching morphology is investigated by establishing the sapphire atomic model and the calculation of the surface energy in each crystal plane. So, we conclude that the etched c-plane sapphire will not take crystal r-plane as the pattern side-facets, when the oxygen atom on the r-plane is not protected by a hard mask during the etching process. The wet-etching process is one of the chemical reactions, so, the mixture of the chemical etching solution would affect the wet-etching morphology. In Chapter 4, different ratio of the sulfuric acid and the phosphoric acid in the etching solution will affect the bottom of the wet-etching pattern. The shape of the wet-etching pattern bottom would be formed by straight lines as increasing the amount of the phosphoric acid in the etching solution. With establishing the atomic model, we realize that the function of the acid etchants, and the location of the etching sites in different dimensions. We propose a so-called spatial screen effect of the etchant, which will reduce the etching rate in the etching process. The spatial screen effect of the etchants will result in the different etching rate in two-dimension etching morphology and then affect the wet-etching morphology. After realizing the etching mechanism and the effect of the etching solution on the etching morphology, the patterned sapphire substrate is applied to fabricate the LED chips. Patterned sapphire substrate can effectively improve LED efficiency, and we also find that the pattern morphology will affect the spatial intensity distribution of the blue GaN-LED. In Chapter 5, the blue GaN-LED grown on different patterned sapphire substrates will be processed with the white-light LED package and the wet-etching pattern morphology effect on the white-light LED package efficiency was investigated. The energy loss in the white-light LED package process is unavoidable. Therefore, in this study, we have proved that by adjusting the spatial intensity distribution of the GaN-LED, the energy loss can be reduced and then white-light LED package efficiency can be improved. However, by controlling the dihedral angle of the pattern side-facets, the spatial intensity distribution of the GaN-LED is adjustable. The above concept is built on the basis of the sapphire wet-etching mechanism and the etching solution effect on the etching morphology. In this thesis, the etching mechanism of the mask-free patterned sapphire substrate and the steric effect of anion on the wet-etching patterned sapphire morphology are presented. Besides, the PSS effect on the white-light LED package efficiency is established to further enhance the white-light LED efficiency.
Appears in Collections:	[National Central University Department of Chemical & Materials Engineering] Electronic Thesis & Dissertation

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