Effect of Contact Angle between Retaining Ring and Polishing Pad on Material Removal Uniformity in CMP Process

다국어 초록 (Multilingual Abstract)

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.

참고문헌 (Reference)

1 Yavas, O., "Wafer-edge yield engineering in leading-edge DRAM manufacturing" 39 : 1-5, 2009

2 Baker, A. R., "The origin of the edge effect in chemical mechanical planarization" 96-22 : 228-238, 1996

3 Park, J., "Pad surface treatment to control performance of chemical mechanical planarization" 47 (47): 1028-1033, 2008

4 Touzov, M. M., "Novel retaining ring to reduce CMP edge exclusion" 337-340, 2001

5 Moussa, R., "Next-Generation Materials for CMP Retaining Rings" 501-505, 2003

6 International Technology Roadmap for Semiconductors, "ITRS Reports 2011 edition"

7 Kwon, D., "Heat and its effects to chemical mechanical polishing" 178 (178): 82-87, 2006

8 Nishi, Y., "Handbook of semiconductor manufacturing technology" Taylor & Francis 17-1, 2007

9 Kim, H. J., "Friction and thermal phenomena in chemical mechanical polishing" 130 (130): 334-338, 2002

10 Thy, 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" 453-460, 2004

11 Park, B., "Experimental investigation of material removal characteristics in silicon chemical mechanical polishing" Institute of Pure and Applied Physics 48 (48): 116505-, 2009

12 Park, B., "Effect of Process Parameters on Friction Force and Material Removal in Oxide Chemical Mechanical Polishing" INST PURE APPLIED PHYSICS 47 (47): 8771-8778, 2008

13 이현섭, "CMP시 SiO2 슬러리의 마찰 특성과 연마결과에 관한 연구" 대한기계학회 29 (29): 983-989, 2005

14 Lee, H., "A wafer-scale material removal rate profile model for copper chemical mechanical planarization" ELSEVIER SCI LTD 51 (51): 395-403, 2011

15 Lin, Y. Y., "A Study on the stress and nonuniformity of the wafer surface for the chemical-mechanical polishing process" 22 (22): 401-409, 2003