1. 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.
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2. 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.
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3. 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
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4. 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
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5. 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.
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6. 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)
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7. 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.
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8. Results SEM AFM Scatterometry
Extracted profiles match SEM pictures with 10nm precision
Scatterometry is non-destructive, faster and produces more descriptive than competing methods.
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9. 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.
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