Enabling Full Profile CMP Metrology and Modeling SFR Workshop May 24, 2001 Runzi Chang, Costas Spanos Berkeley, CA 2001 GOAL: Develop periodic grating metrology to support integrated CMP model by 9/30/2001. 5/24/2001

Motivation First-principle based modeling can help optimize the operation of CMP and drive the technology further. The ability to measure profile evolution at various polish stages is a key ingredient in establishing and confirming models. Formal CMP modeling can the be used to address issues relasted to non-uniformity, pattern loading effects, etc. 5/24/2001

Key idea: measure the evolution of a 1-D periodic pattern at various polish stages Oxide Substrate Use scatterometry to monitor the profile evolution The results can be used for better CMP modeling 5/24/2001

Mask Designed to explore Profile as a function of pattern density The size of the metrology cell is 250m by 250m Periodic pattern has 2m pitch with 50% pattern density 5/24/2001

Sensitivity of Scatterometry (GTK simulation) We simulated 1 mm feature size, 2 mm pitch and 500nm initial step height, as it polishes. The simulation shows that the response difference was fairly strong and detectable. 5/24/2001

Characterization Experiments Wafer # Down Force (psi) Table Speed (rpm) Slurry Flow (ml/min) 1 4 40 50 2 8 3 150 5 80 6 7 9 60 100 10 11 Three one-minute polishing steps were done using the DOE parameters Initial profiles Sopra/AFM Wafer cleaning Nanospec Thickness measurement CMP Sopra Spectroscopic ellipsometer AFM (AMD/SDC) 5/24/2001

Library-based Full-profile CMP Metrology Five variables were used in describing the oxide profile to generate the response library: bottom oxide height (A), bottom width (B), slope 1 (C), slope 2 (D) and top oxide height (E). Substrate A B C D E oxide Reference: X. Niu, N. Jakatdar, J. Bao, C. Spanos, S. Yedur, “Specular spectroscopic scatterometry in DUV lithography”, Proceedings of the SPIE, vol.3677, pt.1-2, March 1999. 5/24/2001

Results SEM AFM Scatterometry Extracted profiles match SEM pictures with 10nm precision Scatterometry is non-destructive, faster and produces more descriptive than competing methods. 5/24/2001

Conclusions and 2002 / 2003 Goals We have demonstrated that scatterometry, in conjunction with specialized profile libraries, can be used for complete profile evaluation during polish. This method has been demonstrated on clean, dry samples. It will be interesting to examine the feasibility of using wet samples, for in-situ/in-line deployment of full-profile CMP metrology. Our next goals are: Integrate initial chemical models into basic CMP model; Validate predicted pattern development (with Dornfeld and Talbot), by 9/30/2002. Develop comprehensive chemical and mechanical model (with Dornfeld and Talbot); Perform experimental and metrological validation, by 9/30/2003. 5/24/2001