1. Profile Extraction with Specular Spectroscopic Scatterometry
First SFR Annual Review
November 8, 1999
Xinhui Niu, Nickhil Jakatdar, Junwei Bao Costas Spanos
Berkeley, CA
This work aims to deliver fast, economic, in-situ analysis
of patterned wafers, that today relies heavily on off-line CD-SEM
and CD-AFM Metrology.
2/17/2019

2. Specular Spectroscopic Scatterometry
0th order, broadband detection
1D gratings and 2D symmetric gratings
Use spectroscopic ellipsometers
sinqm = sinqi+ml/D
|sinqm|<1 i +1 -1 D l
Cut-Off Pitch
(in nm)
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3. Rigorous Coupled Wave Analysis
Fourier expansion of the grating profile.
Eigen system formulation.
Linear system solution of E&M field.
In theory, this approach is “rigorous”.
Enough orders need to be retained for simulation accuracy.
The Grading Tool Kit (GTK) Software has been released.
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4. Specular Spectroscopic Scatterometry Flow
GTK
Electromagnetic
Simulation
Software
Generate Signal
Library
Generate Profile
Library
Library
Generation
Typical turnaround time = 6-12 hours
Load Library
on Ellipsometer
Ellipsometer /
Reflectometer
Compiled
Library
Compiled
Library
Test Grating (Scribe Lane)
Collect
Reflected Signal
Ellipsometry
Measurement
Ellipsometry
Measurement
Reconstructed Profile
Analysis
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5. Specular Spectroscopic Scatterometry Setup
Periodic grating on mask (~ 50 mm * 50 mm area - typical spot size of production spectroscopic ellipsometers)
line/space specified
Provide optical constants for each film in the stack
Broadband ( nm)
Specify variability expected in process (in CD & thickness)
range around nominal in nm
Specify spectroscopic ellipsometer/reflectometer angle of incidence
Save broadband tan y and cos D values
Specify accuracy requirements
down to sub-nm (this automatically decides library size)
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6. Measured and Simulated tan(Y) and cos(D)
measured by KLA-Tencor 1280
Tan(Y)
Cos(D)
Simulated
by GTK
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7. Monte Carlo Profile Library Generation
top
Use “primitives” to classify profiles.
profiles
53 wavelengths
22 layers
1.5 sec/profile on a 500 MHz, P-III
middle
bottom
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8. GTK Interface is available at http://sfr.berkeley.edu
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9. Profile Extraction over the entire Metal FEM
TiN Ti
TEOS Si
CD-SEM (Top CD)
Correlation = 0.92
CD (in nm)
Profile Extraction
Site Number
SSS (Top CD)
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