應用無光罩式雷射蝕刻技術於網狀結構氮化鎵發光二極體元件之特性研究

Abstract

在本論文中，我們將利用雷射蝕刻技術應用於圖案化藍寶石基板與具網狀結構氮化鎵發光二極體元件上。首先本論文節將利用UV(355nm)雷射源對藍寶石基板進行圖案化蝕刻，並藉由UV(355nm)雷射源經光束擴束鏡(Expander)整形後，進入高NA值(>0.2)的非球面鏡組(Objetive Lens，OL)，可達到一般球面鏡無法達到之微小尺寸，進行規則陣列盲孔(via hole)的雷射蝕刻，同時整合雷射觸發與精密線性平台移動，達到所需間距之圖案化製作，搭配氫氧化鈉溶液清洗可以移除雷射蝕刻過程所產生的噴濺物。 第二部份利用雷射蝕刻技術應用於氮化鎵發光二極體元件上，製作不同蝕刻孔徑深度的網狀氮化鎵發光二極體元件，並使用氫氧化鈉溶液移除雷射蝕刻過程中所產生的噴濺物，其LED-0為未經雷射蝕刻氮化鎵發光二極體元件，LED-1為雷射蝕刻製程氮化鎵發光二極體元件其蝕刻直徑4μm且蝕刻深度380nm達到P型氮化鎵層，LED-2為雷射蝕刻製程氮化鎵發光二極體元件其蝕刻直徑4μm且蝕刻深度270nm達到透明導電膜。由實驗結果顯示，在20mA工作電流下，LED-0、LED-1與LED-2的光輸出功率分別為3.83mW、4.58mW與4.22mW。LED-1與LED-2分別比LED-0提升了20%與10%的光輸出功率 延續前面的實驗結果，本論文將改變蝕刻孔徑大小之不同孔徑深度的網狀氮化鎵發光二極體元件，LED-3為雷射蝕刻製程氮化鎵發光二極體元件其蝕刻直徑3μm且蝕刻深度330nm達到P型氮化鎵層，LED-4為雷射蝕刻製程氮化鎵發光二極體元件其蝕刻直徑3μm且蝕刻深度285nm達到透明導電膜。在實驗結果顯示，在20mA工作電流下，LED-0、LED-3與LED-4的光輸出功率分別為3.83mW、5.57mW與4.86mW。LED-3與LED-4分別比LED-0提升了45%與26%的光輸出功率，改變蝕刻孔徑大小能有效提升元件之光輸出功率。 利用雷射蝕刻技術應用於圖案化藍寶石基板與具網狀結構氮化鎵發光二極體元件上有可簡化製程之優點。

In this study, a UV (355 nm) laser source is used to etch patterned sapphire substrates and mesh-type GaN light-emitting diodes (LEDs). The UV laser beam is passed through an expander after shaping into a high NA value (> 0.2). The objective lens (OL) reaches the general spherical mirror but does not reach the small-sized array via a hole obtained by laser etching. Integration of the laser triggering and precision linear integrated mobile platforms was performed to achieve the required spacing. The laser etching process produces splashes that can be removed with NaOH solution. The use of laser etching technology for GaN-based LEDs enables etching of GaN at different depths on mesh apertures. NaOH solution may be used to remove splashes produced during etching. Different LEDs are used in the present study: LED-0, which is not laser etched, LED-1, which is a laser-etched GaN LED with an etching diameter of 4 μm and etch depth of 380 nm reaching the p-type GaN layer, and LED-2, which is a laser-etched GaN LED with an etching diameter of 4 μm and etch depth of 270 nm reaching the ITO film. Under a 20 mA injection current, the output powers obtained for LED-0, LED-1, and LED-2 were 3.83, 4.58, and 4.22 mW, respectively. The respective 20 mA LED output powers of LED-1 and LED-2 are 20% and 10% greater than that of LED-0. This study also investigates the effect of hole size on the different pore etching depths of the mesh-type GaN-based LEDs. Two types of LEDs are investigated: LED-3, which is a laser-etched GaN LED with an etching diameter of 3 μm and etch depth of 330 nm reaching the p-type GaN layer, and LED-4, which is yet another laser-etched GaN LED with an etching diameter of 3 μm and etch depth of 285 nm reaching the ITO film. Under a 20 mA injection current, the output powers of LED-3, LED-4 for LED-0,LED-3,and LED-4 were 3.83, 5.57, and 4.86 mW, respectively. The respective 20 mA LED output powers of LED-3 and LED-4 are 45% and 26% greater than that of LED-0. These results prove that changing the etching hole-size can enhance the optical output power. Laser etching technology was utilized to etch a patterned sapphire substrate. This technology simplifies the etching process of mesh-type GaN LEDs.