Profile Extraction with Specular Spectroscopic Scatterometry

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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.
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Specular Spectroscopic Scatterometry

• 0th order, broadband detection
• 1D gratings and 2D symmetric gratings
• Use spectroscopic ellipsometers

sinqm sinqiml/D sinqmlt1
l
Cut-Off Pitch
600 300 400 200 250 125 (in nm)
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Rigorous Coupled Wave Analysis

• Fourier expansion of the grating profile.
• Eigen system formulation.
• Linear system solution of EM 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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Specular Spectroscopic Scatterometry Flow
Library Generation
Ellipsometry Measurement
Reconstructed Profile
Analysis
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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 (240-800 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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Measured and Simulated tan(Y) and cos(D)
measured by KLA-Tencor 1280
Tan(Y)
Cos(D)
Simulated by GTK
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Monte Carlo Profile Library Generation
top
Use primitives to classify profiles. 180000
profiles 53 wavelengths 22 layers 1.5 sec/profile
on a 500 MHz, P-III
middle
bottom
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GTK Interface is available at http//sfr.berkeley.
edu
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Profile Extraction over the entire Metal FEM
CD-SEM (Top CD)
Correlation 0.92
CD (in nm)
Profile Extraction
Site Number
SSS (Top CD)