Effects of N-Face Finishing on Geometry of Double-Side Polished GaN Substrate
Koji Koyama*, Hideo Aida*,**, Michio Uneda***, Hidetoshi Takeda*, Seong-Woo Kim*, Hiroki Takei*, Tsutomu Yamazaki**, and Toshiro Doi**
*Namiki Precision Jewel Co., Ltd., 3-8-22 Shinden, Adachi, Tokyo 123-8511, Japan
**Kyushu University, 6-1 Kasuga Kouen, Kasuga, Fukuoka 816-8580, Japan
***Kanazawa Institute of Technology, 7-1 Ogigaoka, Nonoichi, Ishikawa 921-8501, Japan
Difficulties involved in producing Double-Side Polished (DSP) GaN substrate are extracted and approaches to overcoming them are reported in this paper. Mechanical polishing with a neutral diamond slurry of pH 7.0 for the N-face and CMP for the Ga-face are widely applied to obtain DSP GaN substrates. Accordingly, the substrate exhibits transparency. However, this is accompanied by approximately 100 µm of bowing due to the Twyman effect. In this paper, the reduction of the substrate bowing to 10 µm is successfully achieved through the use of an acidic diamond slurry with a pH of 1.8 instead of a neutral slurry. Cathode luminescence reveals that an acidic diamond slurry also induces less subsurface damage in the N-face than does the neutral one. We conclude that the stress on the N-face induced by the subsurface damage in the case of polishing with an acidic diamond slurry comes closer to that of the Gaface finished via CMP.
-  S. Nakamura, M. Senoh, N. Iwasa, and S. Nagahama, “High-Brightness InGaN Blue, Green and Yellow Light-Emitting Diodes with Quantum Well Structures,” Jpn. J. Appl. Phys., Vol.34, pp. L797, 1995.
-  M. A. Khan, M. S. Shur, J. N. Kuznia, Q. Chin, J. W. Burm, and W. J. Schaff, “Temperature activated conductance in GaN/AlGaN heterostructure field effect transistors operating at temperatures up to 300°C,” Appl. Phys. Lett., Vol.66, pp. 1083, 1995.
-  Y. Zhou, D. Wang, C. Ahyi, C.-C. Tin, J. Williams, M. Park, N. M.Williams, and A. Hanser, “High breakdown voltage Schottky rectifier fabricated on bulk n-GaN substrate,” Solid-State Electronics, Vol.50, pp. 1744, 2006.
-  Y. Oshima, T. Yoshida, T. Eri, K. Watanabe, M. Shibata, and T. Mishima, “Freestanding GaN Substrates by Hydride Vapor Phase Epitaxy Using Void-Assisted Separation Technology,” Technology of Gallium Nitride Crystal Growth, Vol.133, pp. 79, 2010.
-  K.Motoki, T. Okahisa, N.Matsumoto, M. Matsushima, H. Kimura, H. Kasai, K.Takemoto, K. Uematsu, T. Hirano, M. Nakayama, S. Nakahata, M. Ueno, D. Hara, Y. Kumagai, A. Koukitu, and H. Seki, “Preparation of Large Freestanding GaN Substrates by Hydride Vapor Phase Epitaxy Using GaAs as a Starting Substrate,” Jpn. J. Appl. Phys., Vol.40, pp. L140, 2001.
-  T. Hashimoto, F.Wu, J. S. Speck, and S. Nakamura, “Ammonothermal growth of bulk GaN,” J. Cryst. Growth, Vol.310, pp. 3907, 2008.
-  R. Dwilinski, R. Doradzinski, J. Garczynski, L. P. Sierzputowski, A. Puchalski, Y. Kanbara, K. Yagi, H. Minakuchi, and H. Hayashi, “Excellent crystallinity of truly bulk ammonothermal GaN,” J. Cryst. Growth, Vol.310, pp. 3911, 2008.
-  F. Kawamura, T. Iwahashi, K. Omae, M. Morishita, M. Yoshimura, Y. Mori, and T. Sasaki, “Growth of a Large GaN Single Crystal Using the Liquid Phase Epitaxy (LPE) Technique,” Jpn. J. Appl. Phys., Vol.42, pp. 4, 2003.
-  I. Grzegory, “High pressure growth of bulk GaN from solutions in gallium,” J. Phys.: Condens. Matter, Vol.13, pp. 6875, 2001.
-  G. Nowak, B. E. Ishaug, S. M. Seutter, A. Parkhomovsky, A. M. Dabiran, P. I. Cohen, I. Grzegory, and S. Porowski, “Structure and Composition of GaN (0001) A and B surface,” J. Appl. Phys., Vol.85, pp. 7697, 1999.
-  J. L. Weyher, S. Muller, I. Grzegory, and S. Porowski, “Chemical polishing of bulk and epitaxial GaN,” J. Cryst. Growth, Vol.182, pp. 17, 1997.
-  S. Hayashi, T. Koga, and S. Goorsky, “Chemical Mechanical Polishing of GaN,” J. Electrochem. Soc., Vol.155, pp. H113, 2008.
-  P. R. Taverier, T. Margalith, L. A. Coldren, S. P. Denbaars, and D. R. Clarke, “Chemical Mechanical Polishing of Gallium Nitride,” Electrochem. Solid-State Lett., Vol.5, pp. G61, 2002.
-  H. Aida, H. Takeda, K. Koyama, H. Katakura, K. Sunakawa, and T. Doi, “Chemical Mecanical Polishing of GaN with Colloidal Silica,” J. Electrochem. Soc., Vol.158, pp. H1206, 2011.
-  Y. Gao, T. Fujii, R. Sharma, K. Fujito, S. P. Denbaars, S. Nakamura, and E. L. Hu, “Roughning Hexagonal Surface Morphology on Laser Lift-Off (LLO) N-face GaN with Simple Poto-Enhanced Chemical Wet Etching,” Jpn. J. Appl. Phys., Vol.43, pp. L637, 2004.
-  H. M. Ng, N. G. Weimann, and A. Chowdhury, “GaN nanotip pyramids formed by anisotropic etching,” J. Appl. Phys., Vol.94, pp. 650, 2003.
-  F. Twyman, “Polishing of glass surface,” Proc. of the Optical Convention, pp. 78, 1905.
-  D. Hanser, M. Tutor, E. Preble, M. Williams, X. Xu, D. Tsvetkov, and L. Lin, “Surface preparation of substrates from bulk GaN crystals,” J. Cryst. Growth, Vol.305, pp. 372, 2007.
-  H. Aida, T. Doi, H. Takeda, H. Katakura, S. Kim, K. Koyama, T. Yamazaki, and M. Uneda, “Ultraprecision CMP for sapphire, GaN, and SiC for advanced optoelectronics materials,” Current Applied Physics, Vol.12, pp. S41, 2012.
-  W. Omori, M. Sato, and M. Takahashi, “Research of oxidizing agent-assisted polishing of single-crystal silicon carbide (2),” Proc. of The Japan Society for Precision Engineering annual conf., pp. 939, 2013.
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