Verification of the Effectiveness of UV-Polishing for 4H-SiC Wafer Using Photocatalyst and Cathilon
Takeshi Tanaka†, Masaru Takizawa, and Akihiro Hata
1-1-1 Nojihigashi, Kusatsu, Shiga 525-8577, Japan
The polishing of 4H-SiC wafer processed under ultraviolet (UV) irradiation was investigated to verify the phenomena and effectiveness of ultraviolet-ray aided machining (U-RAM). Inductively coupled plasma spectrometry (ICPS) analysis was conducted to quantitatively determine the oxidation/dissolution volume of SiC. X-ray absorption spectroscopy (XAS) and X-ray photoelectron spectroscopy (XPS) were used to qualitatively analyze the 4H-SiC surfaces. These analyses were used to clarify the compounds that are formed/removed by the decomposition of cathilon dye and water during the polishing of 4H-SiC using TiO2-, cathilon- and TiO2-cathilon (mixed) slurries, all of which contained diamond particles. ICPS measurements indicate that a small amount of Si dissolves in aqueous solutions of cathilon- and TiO2-cathilon. XAS and XPS measurements indicate that SiC composes the bulk of the as-received 4H-SiC, and the surface and thin surface form an interface oxide inside SiC. The chemical-mechanical polishing of 4H-SiC using the TiO2-cathilon slurry forms an oxide, interface oxide, oxynitride and nitride. Diamond particles easily remove these compounds by mechanical scratching. It is possible to attain smaller surface roughness and higher polishing efficiency by combination with chemical reaction of TiO2-cathilon slurry and mechanical action of diamond particles under UV irradiation.
-  T. Ohyoshi, H. Unpou, Y. Isono, and T. Tanaka, “Study of Ultraviolet-Ray Aided Machining (1st Report) – Verification of Basic Principal and Phenomena,” Kansai District Meeting of the Japan Society for Precision Engineering, pp. 31-32, 1999 (in Japanese).
-  Y. Chiwaya and T. Tanaka, “Fundamental Verification of Ultraviolet-Excited Abrasion and Polishing Characteristics of Copper – Study of Luminescence Machining,” Key Engineering Materials, Vol.291-292, pp. 343-348, 2005.
-  Y. Chiwaya and T. Tanaka, “Chemical Etching of Copper Surface by Fluorescent Substance Excited with Ultraviolet Ray-Study of Ultraviolet Ray-Assisted Machining,” J. of the Japan Society for Precision Engineering, Vol.73, No.4, pp. 444-449, 2007 (in Japanese).
-  Y. Chiwaya and T. Tanaka, “Polishing of Copper Using Fluorescent Substance and Photocatalyst Excited by Ultraviolet Irradiation-Study of Ultraviolet Ray-Assisted Machining,” J. of the Japan Society for Abrasive Technology, Vol.51, No.4, pp. 232-237, 2007 (in Japanese).
-  T. Tanaka, “Polishing of Nickel Cylinder Using A Photocatalyst and A Fluorescent Substance Excited by An Ultraviolet Ray,” Advanced Materials Research, Vol.76-78, pp. 337-342, 2009.
-  T. Tanaka, “Polishing Aspect of A5052 Using Photocatalyst and Cathilon,” J. of the Japan Society for Abrasive Technology, Vol.59, No.7, pp. 402-407, 2015 (in Japanese).
-  T. Tanaka, “Polishing of Co-Cr-Mo Alloy Using Photocatalyst and Cathilon Excited by Ultraviolet Irradiation,” J. of the Japan Society for Precision Engineering, Vol.82, No.7, pp. 690-696, 2016 (in Japanese).
-  H. Nitta, “Development of high Removal Rate and High Planarization CMP Technologies for Next-Generation Device Wafers and Wires,” Ph.D. thesis, Kouthi University of Technology, 2009 (in Japanese).
-  S. Hirano, K. Kawata, H. Asamizu, and T. Kato, “Development of High-Efficiency CMP Process of SiC Wafers for Power Electronics,” J. of the Japan Society for Abrasive Technology, Vol.60, No.8, pp. 454-459, 2016 (in Japanese).
-  K. Yamamura, T. Takiguchi, M. Ueda, H. Deng, A. Hattori, and N. Zettsu, “High-Integrity Finishing of 4H-SiC (0001) by Plasma-Assisted Polishing,” J. of the Japan Society for Abrasive Technology, Vol.55, No.9, pp. 534-539, 2011 (in Japanese).
-  T. Kasumi, Y. Sato, H. Ikeda, Y. Akagami, and N. Umehara, “The Development of AC Electric Field Assisted Polishing for Silicon Carbide Substrates with Control of Abrasive Behavior – Clarification of Improvement Mechanism for Polishing Rate with Electric Field,” J. of the Japan Society for Precision Engineering, Vol,79, No.1, pp. 87-92, 2013 (in Japanese).
-  T. Kurita, K. Miyake, K. Kawata, K. Ashida, and T. Kato, “Development of New Combined Polishing Process for Single Crystal Silicon Carbide,” J. of the Japan Society for Abrasive Technology, Vol.58, No.1, pp. 30-35, 2014 (in Japanese).
-  K. Yamaguchi, M. Touge, S. Kubota, T. Nakano, and J. Watanabe, “Study on High Efficiency Mirror Finished Technique of Single-Crystal SiC Substrate – The Planarization Process by Constant-Pressure Grinding and an Ultraviolet Irradiation Assisted Polishing,” J. of the Japan Society for Precision Engineering, Vol.77, No.1, pp. 116-120, 2011 (in Japanese).
-  T. Sakamoto, T. Inaki, K. Oda, M. Touge, and T. Fujita, “Ultraviolet-Assisted Polishing of 4 inch SiC Substrate,” J. of the Japan Society for Abrasive Technology, Vol.58, No.4, pp. 235-240, 2014 (in Japanese).
-  T. Sakamoto, “Study of Practical Realization of Advanced Polishing Using Ultraviolet Light,” Ph.D. thesis, Kumamoto Univ., 2014 (in Japanese).
-  K. Yamauchi, Y. Sano, and K. Arima, “Smoothing of Single Crystalline SiC and GaN by Catalyst Referred Etching,” J. of the Japan Society for Precision Engineering, Vol.78, No.11, pp. 947-950, 2012 (in Japanese).
-  S. Yamamoto, “Ability of Mechanical Polishing Using Fine Diamond,” J. of the Japan Society for Abrasive Technology, Vol.59, No.6, pp. 316-319, 2015 (in Japanese).
-  B. Hornetz, H. J. Michel, and J. Habritter, “ARXPS Studies of SiO2-SiC Interfaces and Oxidation of 6H SiC Single Crystal Si-(001) and C-(001) Surfaces,” J. of Materials Research, Vol.9, No.12, pp. 3088-3094, 1994.
-  M. Tallarida, D. Schmeisser, F. Zheng, and F. J. Himpsel, “X-Ray Absorption and Photoemission Spectroscopy of 3C- and 4H-SiC,” Surface Science, Vol.600, pp. 3879-3883, 2006.
-  Y. F. Hu, H. Piao, J. Fronheiser, and K. Matocha, “Chemical Characterization of SiO2/SiC Interface After Nitridation Treatment,” J. of Electron Spectroscopy and Related Phenomena, Vol.184, pp. 245-248, 2011.
-  K. Takeuchi, S. Murasawa, and T. Sijyuku, “World of Photocatalyst,” Kougyouchousakai Publisher, pp. 17-42, 1998 (in Japanese).
-  A. Fujishima, K. Hashimoto, and T. Watanabe, “Photocatalyst Mechanism,” Nihonjitsugyou Publisher, p. 122, 2004 (in Japanese).
-  K. Ueno, “Chelate Chemistry-An Introduction,” Nankoudou, pp. 16-139, 1992 (in Japanese).