- 學位論文
ICP乾蝕刻表面粗化對垂直型氮化鎵發光二極體之研究
The study of inductively coupled plasma dry etching surface roughness on vertical gallium nitride light emitting diodes
摘要
垂直LED製程中為了有效提高表面出光率，一般是以KOH濕式蝕刻對n-GaN進行表面粗化製程，形成六角錐結構破壞全反射面，使光線路徑改變進而增加光的逃逸機率，而提高光的萃取效率。本論文研究是以pattern sapphire substrate (PSS)經laser lift-off (LLO)轉移至Si基板留下來的微米級特定規則的微結構圖案，利用inductively coupled plasma (ICP)乾式蝕刻方式移除undoped-GaN後，持續蝕刻n-GaN表面作出相似於不規則六角錐圖案取代KOH濕式蝕刻圖案。 ICP機台參數是可分段設定進行蝕刻，利用各段氣體不同比例組合交叉蝕刻，以不同蝕刻機制獲得不同圖案輪廓，以期使元件達到與KOH濕式蝕刻方式相同的光輸出效率。優化ICP乾式蝕刻參數分為兩段主蝕刻參數，第一段：BIAS power：120 W、ICP power：120 W、APC pressure：2 Pa、CHF3：30 Sccm、O2：5 Sccm，第二段：BIAS power：350 W、ICP power：280 W、APC pressure：7 Pa、Cl2：50 Sccm、BCl3：22.5 Sccm。元件封裝後特性在700 mA時，波長為453 nm；發光強度為846 mW；順向電壓為3.33 V；同時濕式蝕刻之元件特性在相同電流下，波長為454 nm；發光強度為877 mW；順向電壓為3.29 V。研究結果顯示乾式蝕刻之成效已趨近濕式蝕刻，證明對基板轉換後之n-GaN表面粗化，ICP乾式蝕刻為一有效方法。
關鍵字
none並列摘要
One of the effective techniques for improving light output efficiency of vertical LED is n-GaN surface roughening using KOH wet etching, forming the hexagonal pyramid structure to destroy the complete reflection surface so that the light path changes thereby increasing the chances of escape of light, and improving the light extraction efficiency. In this study, the pattern sapphire substrate (PSS) by laser lift-off (LLO) transferred to the Si substrate to stay behind the micron-specific rules of microstructure pattern. After removal of undoped-GaN layer by ICP dry etching, continue etching on the n-GaN surface making a similar to the irregular hexagonal pyramid pattern to replace the KOH wet etching pattern. As the ICP machine parameters can be segmented etching, cross-etching is performed using different groups of chemical gas groups to control the etching rate to make different pattern profiles, achieve the light output efficiency with KOH wet etching. Optimizd experimental parameters are divided into two main etching parameters. First step: BIAS power: 120 W, ICP power: 120 W, APC pressure: 2 Pa, CHF3: 30 Sccm, O2: 5 Sccm. Second step: BIAS power: 350 W, ICP power: 280 W, APC pressure: 7 Pa, Cl2: 50 Sccm, BCl3:22.5 Sccm. The LED package show forward voltage is 3.33 V and light intensity is 846 mW at wavelength of 453 nm driven at 700 mA. At the same time wet etching package components at the same current, forward voltage is 3.29 V and light intensity is 877 mW at wavelength of 454 nm. Experimental results demonstrate dry and wet etching data is not significant, proving to be one of the effective techniques for roughing the n-GaN surface.