Effect of contact angle between retaining ring and polishing pad on material removal uniformity in CMP process
Tóm tắt
This paper presents the effect of the contact angle between the retaining ring and the polishing pad in chemical mechanical polishing (CMP) on the profile of the material removal rate (MRR) around the wafer edge and on the within-wafer nonuniformity (WIWNU). This study demonstrates that the mechanical interaction among the polishing pad, wafer, and retaining ring influences the ability to achieve planarization from the CMP process. In particular, the purpose of this study is to understand the effect of the contact conditions between the retaining ring and the pad on the CMP process. In order to verify the mechanical aspects of the MRR near the wafer edge, retaining rings with different contact angles were prepared. Finite element analysis (FEA) verified the effect of the contact angle between the retaining ring and the polishing pad on the stress distribution around the edge of the wafer. The results of the analysis were corroborated by conducting CMP experiments with 200-mm blanket oxide wafers. As expected, the FEA results were in good agreement with the MRR profile around the edge area. Through simulations and experiments, we concluded that the contact angle is an important factor to achieve a flatter edge profile and the material removal profile around the edge of the wafer was optimum at a 0o contact angle. In particular the WIWNU was below 4% when a flat retaining ring was used. The results of this study make it possible to improve the yield of chip production by ensuring the retaining ring maintains perfect flatness without making any special design changes to the CMP equipment.
Tài liệu tham khảo
Thy, T., William, R., Jason, T., Igor, J., Nicholas, C., Paul, J., Reuben, F., Dan, M., Cort, D., Mark, R., Christian, W., Michael, B., Aaron, B., and Thomas, T., “Extreme Edge Engineering — 2 mm Edge Exclusion Challenges and Cost-Effective Solutions for Yield Enhancement in High Volume Manufacturing for 200 mm and 300 mm Wafer Fabs,” IEEE/SEMI Advanced Semiconductor Manufacturing Conference, pp. 453–460, 2004.
Yavas, O., Richter, E., Kluthe, C., and Sickmoeller, M., “Wafer-edge yield engineering in leading-edge DRAM manufacturing,” Semiconductor Fabtech., Vol. 39, pp. 1–5, 2009.
International Technology Roadmap for Semiconductors, “ITRS Reports 2011 edition,” http://www.public.itrs.net/reports.html
Baker, A. R., “The origin of the edge effect in chemical mechanical planarization,” Proc. of Electrochem. Soc. Fall Meeting, USA, Vol. 96–22, pp. 228–238, 1996.
Nishi, Y. and Doering, R., “Handbook of semiconductor manufacturing technology,” Taylor & Francis, pp. 17–1, 2007.
Park, B., Lee, H., Kim, Y., Kim, H., and Jeong, H., “Effect of process parameters on friction force and material removal in oxide chemical mechanical polishing,” Japanese Journal of Applied Physics, Vol. 47, No. 12, pp. 8771–8778, 2008.
Moussa, R. and Quartapella, C., “Next-Generation Materials for CMP Retaining Rings,” VMIC Conference, pp. 501–505, 2003.
Touzov, M. M., Fujita, T., and Doy, T. K., “Novel retaining ring to reduce CMP edge exclusion,” IEEE international Semiconductor Manufacturing Symposium, pp. 337–340, 2001.
Lee, H., Park, B., Seo, H., Jung, J., Jeong, S., and Jeong, H., “A Study on Frictional Characteristics and Polishing Results of SiO2 Slurry in CMP,” Transactions of the Korean Society of Mechanical Engineers — A, Vol. 29, No. 7, pp. 983–989, 2005.
Lee, H. and Jeong, H., “A Wafer-scale material removal rate profile model for copper chemical mechanical planarization,” International Journal of Machine Tools and Manufacture, Vol. 51, No. 5, pp. 395–403, 2001.
Lin, Y. Y. and Lo, S. P., “A Study on the stress and nonuniformity of the wafer surface for the chemical-mechanical polishing process,” International Journal of Advanced Manufacturing Technology, Vol. 22, No. 5–6, pp. 401–409, 2003.
Kim, H. J., Kim. H. Y., Jeong, H. D., Lee, E. S., and Shin, Y. J., “Friction and thermal phenomena in chemical mechanical polishing,” Journal of Materials Processing Technology, Vol. 130–131, No. 0, pp. 334–338, 2002.
Kwon, D., Kim, H., and Jeong, H., “Heat and its effects to chemical mechanical polishing,” Journal of Materials Processing Technology, Vol. 178, No. 1–3, pp. 82–87, 2006.
Park, B., Jeong, S., Lee, H., Kim, H., Jeong, H., and Dornfelt, D. A., “Experimental investigation of material removal characteristics in silicon chemical mechanical polishing,” Japanese Journal of Applied Physics, Vol. 48, No. 11, pp. 116505, 2009.
Park, J., Jeong, H., Yoshida, K., and Kinoshita, M., “Pad surface treatment to control performance of chemical mechanical planarization,” Japanese Journal of Applied Physics, Vol. 47, No. 2, pp. 1028–1033, 2008.