5/24/2001 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 .
Jan 31, 2016
5/24/2001
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Enabling Full Profile CMP Metrology and Modeling
SFR WorkshopMay 24, 2001
Runzi Chang, Costas SpanosBerkeley, CA
2001 GOAL: Develop periodic grating metrology to support integrated CMP model by 9/30/2001.
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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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Key idea: measure the evolution of a 1-D periodic pattern at various polish stages
SubstrateOxide
• Use scatterometry to monitor the profile evolution• The results can be used for better CMP modeling
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Mask Designed to explore Profile as a function of pattern density
• The size of the metrology cell is 250m by 250m
• Periodic pattern has 2m pitch with 50% pattern density
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Sensitivity of Scatterometry (GTK simulation)
0 500 1000 1500 20000
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5Profile Evolution during CMP
Oxide (nm)
pro
file
(m
icro
n)
• We simulated 1 m feature size, 2 m pitch and 500nm initial step height, as it polishes.
• The simulation shows that the response difference was fairly strong and detectable.
Tan PSI Response to Profile Evolution
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
240
280
320
360
400
440
480
520
560
600
640
680
720
760
Wavelength(nm)
tan
PS
I
tan PSI 500nm
tan PSI 400nm
tan PSI 300nm
tan PSI 200nm
tan PSI 100nm
tan PSI Flat Surface
Cos DEL Response to Profile Evolution
-1.5
-1
-0.5
0
0.5
1
1.5
240
280
320
360
400
440
480
520
560
600
640
680
720
760
Wavelength(nm)
cos
DE
L
cos DEL 500nm
cos DEL 400nm
cos DEL 300nm
cos DEL 200nm
cos DEL 100nm
cos DEL Flat Surface
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Characterization Experiments
• Three one-minute polishing steps were done using the DOE parameters
Initial profilesSopra/AFM
CMP NanospecThickness
measurement
SopraSpectroscopicellipsometer
AFM(AMD/SDC)
Wafer cleaning
Wafer #
Down Force
(psi)
Table Speed (rpm)
Slurry Flow
(ml/min)
1 4 40 50
2 8 40 50
3 4 40 150
4 8 40 150
5 8 80 50
6 4 80 50
7 8 80 150
8 4 80 150
9 6 60 100
10 6 60 100
11 6 60 100
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Library-based Full-profile CMP Metrology
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.
• 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
AB
CD
E
oxide
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-3 -2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2
x 104
0
2000
4000
6000
-2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.5 3
x 104
-5000
0
5000
-3 -2 -1 0 1 2 3
x 104
0.9
1
1.1x 10
4
AFM
Results
• Extracted profiles match SEM pictures with 10nm precision
• Scatterometry is non-destructive, faster and produces more descriptive than competing methods.
SEM Scatterometry
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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.