Fabrication of patterned sapphire substrate and high-efficiency GaN Light-emitting diodes by ICP dry etching

• Main Authors: Chi-fu Yu, 余祈富
• Other Authors: Shi-Chang Shei
• Format: Others
• Language: en_US
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/36072354821097539342

碩士 === 國立臺南大學 === 光電工程研究所 === 99 === In the first study, varied baking and oven temperature would make PR for hardness improved between ICP etching process, the selectivity of PSS over PR was improved from 1.02 to 1.1. The reason is that high temperature would make bonding strength be stronger than before. Hence, we could use fabricating high height patterns of PSS in future. Uniformity of within wafer is too high to affect study accuracy. So, we changed the coil energy located between wafer and ICP coil in the reactor. Magnetic current was conducted to magnetic coil from 1.5 to 2.1A, exhibiting that plasma distribution moved from inner to outer by magnetic force with current, and uniformity of wafer to wafer have lowest at 2.1A. By within/wafer to wafer results, the best position of plasma are 2.1A with the lowest uniformity of inner and outer. Next, additive gas CH4 was mixed in BCl3 etching gas, surface of PR would form protected thin film (amorphous hydrogenated carbon layer (α-C:H layer ) or CHx polymer-like layers to against the plasma etching. It could increase the selectivity of PSS from 0.7 to 0.9. 　　Next section is about temperature effect for ICP etching, plasma etching of cone-shaped sapphire by ICP with temperature varied from -20℃ to 20℃. Patterned sapphire width was decreased with temperature dependence from 2.526um to 2.199um for better selectivity and bonding strength in higher chiller temperature. In former section, PR etching rate was decreased by oven and baking temperature increasing in ICP etching process and selectivity was changed from 1.02 to 1.1, So, PR is easy to keep ball-shaped in ICP etching process. Exposed area is greater gradually in etching would affect sapphire etching rate in increasing the temperature. After all, temperature would affect the PR etching rate improved is more than sapphire etched rate decreased with selectivity improved from 0.79 to 0.97. 　　In the third section, GaN-based LEDs grown on the cone-shaped patterned sapphire substrates with different height. Output power were 4.04 mW, 5.94 mW, 6.12 mW, and 6.25 mW in 20-mA current injection for LED I (flat sapphire), LED II (1.2μm height), LED III (1.4μm height), and LED IV (1.7μm height). It demonstrates that output power is increased with higher height PSS. The reason is that more light could be lead to the surface of device by increased height of cone-shape PSS. After all, using TransPro for various height PSS by simulate, the results were same as the experiment.