Effect of photocatalytic oxidation technology on GaN CMP

• Published in: Applied surface science Vol. 361; pp. 18 - 24
• Main Authors: Wang, Jie, Wang, Tongqing, Pan, Guoshun, Lu, Xinchun
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.01.2016
• Subjects: Catalysis; Catalysts; Chemical mechanical polishing; Gallium nitrides; GaN; H2O2–SiO2-based slurry; Mathematical models; Mechanism; Oxidation; Photocatalysis; Photocatalytic oxidation; Titanium dioxide; H2O2–SiO2-based slurry; GaN; Chemical mechanical polishing; Photocatalytic oxidation; Mechanism
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2015.11.062

•Photocatalytic oxidation technology was introduced to GaN CMP for the first time and proves to be more efficient than before.•XPS analysis reveals the planarization process by different N-type semiconductor particles.•Analyzing the effect of pH on photocatalytic oxidation in GaN CMP.•Proposing the photocatalytic oxidation model to reveal the removal mechanism. GaN is so hard and so chemically inert that it is difficult to obtain a high material removal rate (MRR) in the chemical mechanical polishing (CMP) process. This paper discusses the application of photocatalytic oxidation technology in GaN planarization. Three N-type semiconductor particles (TiO2, SnO2, and Fe2O3) are used as catalysts and added to the H2O2–SiO2-based slurry. By optical excitation, highly reactive photoinduced holes are produced on the surface of the particles, which can oxidize OH− and H2O absorbed on the surface of the catalysts; therefore, more OH* will be generated. As a result, GaN MRRs in an H2O2–SiO2-based polishing system combined with catalysts are improved significantly, especially when using TiO2, the MRR of which is 122nm/h. The X-ray photoelectron spectroscopy (XPS) analysis shows the variation trend of chemical composition on the GaN surface after polishing, revealing the planarization process. Besides, the effect of pH on photocatalytic oxidation combined with TiO2 is analyzed deeply. Furthermore, the physical model of GaN CMP combined with photocatalytic oxidation technology is proposed to describe the removal mechanism of GaN.