A Study On The Process Optimization And Performance Improvement Of Pattern Sapphire Substrate

The patterned sapphire substrate（PSS）is currently the most widely used lightemitting diode（LED）substrate.Compared with the flat sapphire substrate,PSS can further improve the LED light efficiency index by about 30%,but it is close to the theoretical limit level.Under the current commercial production conditions of PSS,further improving the light efficiency level of LEDs is the focus of the business community..In this paper,a new type of SiO2 patterned sapphire substrate（SPSS）was prepared on the basis of PSS.The effects of SPSS on gallium nitride（GaN）growth and LED performance were systematically studied,and the potential of SPSS in industrial production was further verified.The main findings of this paper are as follows:（1）The influence of the main factors on the etching rate and selection ratio in the etching process after adding CHF₃ in the preparation process of PSS was studied.The research results show that the primary and secondary factors affecting the etching selection ratio are CHF₃ flow rate,Advanced Process Control（APC）,and bias power,while the primary and secondary factors affecting sapphire etching rate are APC,bias power,and CHF₃ flow rate.Finally,the best process plan for preparing high duty cycle PSS is:bias power of 380 W,CHF₃ flow rate of 15 scrn,APC of 55%,the height of the cone pattern prepared with the optimized parameters is 1.9 μm,the bottom width is 2.85 μm,the radian of the side-wall is 180 nm,and the duty cycle reaches 81.85%.（2）A SiO2 film was prepared on sapphire substrates by Plasma Enhanced Chemical Vapor Deposition（PECVD）in this study.After depositing the SiO2 film,a SiO2 patterned sapphire substrate（SPSS）was prepared through photolithography and dry etching,and a GaN-based LED device with SPSS was obtained by using epitaxial growth and micro-nano processing technology of the LED device.The effect of SPSS on the crystal quality of the GaN epitaxial layer,the light extraction efficiency,and the performance of the LED device was investigated.The experimental and simulation results show that,compared to the conventional patterned sapphire substrates（CPSS）,the GaN epitaxial layer grown on SPSS had lower dislocation density and higher crystal quality.And the light extraction efficiency of SPSS-LED was increased by about 26%,the light output power and brightness of SPSS-LED were both increased by about 5%.