| YANG Youming,ZHOU Hai,HU Shixiang,XIA Liqin,REN Xiangpu.Ultraviolet Photocatalysis Assisted Chemical Mechanical Polishing of GaN Surface[J],53(6):157-167 |
| Ultraviolet Photocatalysis Assisted Chemical Mechanical Polishing of GaN Surface |
| Received:May 04, 2023 Revised:September 20, 2023 |
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| DOI：10.16490/j.cnki.issn.1001-3660.2024.06.014 |
| KeyWord:GaN UV photocatalysis polishing MRR Ra single-factor test orthogonal test |
| Author | Institution |
| YANG Youming |
School of Mechanical Engineering, Yancheng Institute of Technology, Jiangsu Yancheng , China |
| ZHOU Hai |
School of Mechanical Engineering, Yancheng Institute of Technology, Jiangsu Yancheng , China |
| HU Shixiang |
School of Mechanical Engineering, Yancheng Institute of Technology, Jiangsu Yancheng , China |
| XIA Liqin |
School of Mechanical Engineering, Yancheng Institute of Technology, Jiangsu Yancheng , China |
| REN Xiangpu |
School of Mechanical Engineering, Yancheng Institute of Technology, Jiangsu Yancheng , China |
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| Abstract: |
| This study aims to investigate the effects of various polishing parameters (TiO2 concentration, pH value, H2O2 concentration, polishing pressure, polishing pad rotational speed, and polishing slurry flow rate) on the material removal rate (MRR) and surface roughness (Ra) of Ga-face GaN substrates during the ultraviolet light-catalyzed chemical mechanical polishing (CMP) process. Based on the optimization of polishing process parameters, an efficient and low-damage polishing process was developed. Single-factor and orthogonal experiments were designed to investigate the effects of the aforementioned polishing parameters on the polishing effects of GaN substrates while satisfying the requirements for material removal rate and surface roughness. During the polishing process, three different polishing methods (non-illuminated polishing, illuminated polishing pad polishing, and illuminated polishing slurry polishing) and the effects of different factors such as TiO2 concentration, pH value, H2O2 concentration, polishing pressure, polishing pad rotational speed, and polishing slurry flow rate on the polishing efficiency of GaN substrates were compared In the orthogonal experiment, the polishing process parameters were optimized and the MRR and Ra values under different process parameter conditions were measured to explore the polishing effects on the Ga-face of GaN substrates. The experimental results showed that using a self-made polishing slurry with the addition of nano-TiO2 photocatalytic abrasive and adopting the illuminated polishing slurry method could achieve good polishing effects and a low-damage, high-quality ultra-smooth surface. Furthermore, under the ultraviolet light-catalyzed polishing condition, according to the results of the orthogonal experiment, a pH value of 11, an H2O2 concentration of 4wt.%, a TiO2 concentration of 3wt.%, a polishing pressure of 16 000 Pa, a polishing pad rotational speed of 30 r/min, a polishing slurry flow rate of 2.5 mL/min, and an illuminated polishing slurry polishing method were selected for the polishing optimization experiment. The removal rate of GaN substrate could reach 698.864 nm/h, which significantly improved the polishing efficiency compared with the unilluminated polishing method. In addition, the surface roughness Ra value of the ultra-smooth GaN crystal surface could be obtained by observing with a white light interferometer, which was 0.430 nm in the sub-nanometer range. Based on the comprehensive experimental results, it is believed that ultraviolet light-catalyzed chemical mechanical polishing is an efficient and low-damage surface quality polishing method for single crystal GaN substrates. It can promote the rapid removal of Ga2O3 generated on the GaN surface and improve the polishing efficiency. By using the illuminated polishing slurry method, the polishing efficiency of the Ga-face of the GaN substrate can be greatly improved. Considering all of these factors, it is concluded that based on the ultraviolet light-catalyzed GaN substrate Ga-face chemical mechanical polishing experiment, the composite polishing method of ultraviolet light-assisted combined with chemical mechanical polishing can achieve efficient and low-damage polishing for single crystal GaN substrates. TiO2 concentration, pH value, H2O2 concentration, polishing pressure, polishing pad rotational speed, polishing slurry flow rate, and illuminated polishing method can all affect the polishing effects of GaN substrates. The experiment shows that TiO2 concentration, pH value, and illuminated polishing method have a relatively significant impact on the polishing effects of GaN substrates. |
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