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Lawrence Livermore National Laboratory
Michael J. Wilson
LLNL-PRES-501872
Lawrence Livermore National Laboratory, P. O. Box 808, Livermore, CA 94551 This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344
Double-Sided Interferometer for Profiling Measurements Simultaneously Determining
Thickness and Form
May 23, 2012
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Overview
Background Requirements Design Progression
• Describe the design logic and the reason to change the design
Results Summary
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To be able to accurately analyze the experiment the absolute thickness must be known
Courtesy of Ray Smith
140/150/160/170µm diamond steps
10µm Au 50µm diamond
VISAR Data
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Requirements
Absolute thickness measurements and form Thickness uncertainty of 250 nm Uses commercially supported metrology tools Uses standard metrology tool interface to collect data Ability to use both a laser profilometer and white light
interferometer Measure both transparent and opaque samples Completes a measurement in an hour or less
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ATMM
• Confocal laser probe • Able to measure
thickness with an uncertainty of 510 nm
Design Progression
Double-Sided Prism Design Double-Sided Corner Cube
• White light interferometer or laser probe
• Able to measure thickness with an uncertainty of 1.2 µm
• White light interferometer or laser probe
• Able to measure thickness with an uncertainty of 100 nm
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Measureing Thickness Using ATMM
Design Logic For Absolute Thickness Measuring Machine (ATMM)
Measure both sides of a sample simultaneous with laser probes
Be able to take in situ calibration measures for different step heights or thickness samples
Scan to be able to get profile data
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What did we learn from ATMM
Confocal laser probes preferred to triangulation laser probes
Confocal laser probes have trouble measuring transparent samples
Confocal laser probes sensitive to ~3° Controls need to be commercially supported Compact foot print desired
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Measuring Thickness Using DSI Prism
Design Logic For Double Sided Interferometer Prism (DSI Prism)
Measure both sides of a sample in one setup
Use both white light interferometry (WLI) and laser probe
Use commercially support equipment
Be able to get thickness data and form data in one measurement with WLI
Compact design
ΔF
zo zF
ΔR
zR
zo
Sample
Prism
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What did we learn from DSI Prism design
Prism very difficult to manufacture Complex error map needed to compensate for Prism
miss alignment
100 200 300 400 500 600 700 800-0.1
-0.05
0
0.05
0.1
mm
Number of Rows no units
Horizontal Cross Section
300 350 400 450 500 550 600 650 700 750 800-0.1
-0.05
0
0.05
0.1
mm
Number of Rows no units
Longitudinal Cross Section
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What did we learn from DSI Prism design (cont.)
White light interferometer z stage does not repeat to starting position to better than 1µm
Four mirrors depreciate the intensity of the light by 45%, making transparent surfaces not measureable
Post processing of data is needed to get thickness measurements
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Measuring Thickness Using DSI Corner Cube
Design Logic For Double Sided Interferometer Corner Cube (DSI Corner Cube)
Measure both sides of a sample in one setup
Use both white light interferometry (WLI) and laser probe
Use commercially support equipment
Be able to get thickness data and form data in one measurement with WLI
Compact design
Objective Sample
Corner Cube
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Fidicials
Through Hole
What did we learn from DSI Corner Cube
Simpler is better Post process of data is necessary The reference is very important
Top Surface Scan
Bottom Surface Scan
100µm Gauge Block
Know Distance
Sample Holder/Reference Corner Cube
Sample Holder Reference
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Data For MatDS Ta EOSDrv NIF Experiment
Histogram of The Subtracted Data
Know Distance
Top Surface Scan
Bottom Surface Scan
3D Plot of Data Set
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Future Work
Develop kinematic hardware for holding references and work pieces
Develop algorithms to automate the process and analyze the data
Design, develop, and test a system in a glove box
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Acknowledgements
Richard Seugling Pete Davis Walter Nederbragt Matthew Swisher Chuck Kumar Trevor Ness Ken Hienz Sean Felker David Swift Jon Eggert Raymond Smith
HED Manufacturing team – Alex Hamza, Don Bennett, Pete DuPuy, Craig Akaba, Mike McClure, Steve Strodecht, Rick Vargas, Gino Mercado, Kerry Bettencourt, Paul Mirkarimi, and Kerri Blobaum
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References
Nederbragt, W., et al 2005. Design And Use Of A High-Accuracy Non-Contact Absolute Thickness Measurement Machine ASPE 20th Annual Meeting (2005)
Drabarek, P, et al 2009 Interferometrical System For High Precision Measurements of Flatness, Thickness and Parallelism of Mechanical Parts ASPE 24th Annual Meeting (2009)
Kelly, D. 2004 Design and Qualification of an Absolute Thickness Measuring Machine. Master’s thesis. Massachusetts Institute of Technology in Mechanical Engineering
Ai, C and K. Smith. 1992. Accurate measurements of the dihedral angle of a corner cube. Applied Optics. 31:4:519-527
Doiron, T. and J. Beers. The Gauge Block Handbook. Dimensional Metrology Group Precision Engineering Division National Institute of Standards and Technology
Doiron, T. 2008. Gauge Blocks – A Zombie Technology. Journal of Research of the National Institute of Standards and Technology. 113: 3:175-184
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Thank You
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