Effects of Edge Roughness on Optical Scattering from Periodic Microstructures

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Bergner, B. (2009). Effects of Edge Roughness on Optical Scattering from Periodic Microstructures. Unc Charlotte Electronic Theses And Dissertations.
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Abstract

Planar photonic crystals and other microstructured surfaces have important applications in a number of emerging technologies. However, these structures can be difficult to fabricate in a consistent manner. Rapid, precise measurements of critical parameters are needed to control the fabrication process, but current measurement techniques tend to be slow and often require that the sample be modified in order to make the measurement. Optical scattering can provide a rapid, non-destructive, and precise method for measuring these structures, and optical scatterometry is a good candidate technique for measuring micro-structured surfaces for process control. However, variations in the profile, such as those caused by edge roughness, can make significant contributions to the uncertainty in scatterometry measurements. Because of the multi-dimensional nature of the problem, modeling these variations can be computationally expensive. This dissertation examines the effects of edge roughness on optical scatterometry signals. Rigorous numerical simulations show that the effects of edge roughness are sensitive to the correlation length and the frequency content of the roughness as well as its amplitude. However, these rigorous calculations are computationally expensive. A less computationally expensive model based on a generalized Bruggeman effective medium approximation is developed and shown to be effective for modeling the effects of short correlation length edge roughness on optical scatterometry signals.

Details
Author

Bergner, Brent

Title

Effects of Edge Roughness on Optical Scattering from Periodic Microstructures

Physical Description

1 online resource (138 pages) : PDF

Date

2009

Degree Granting Institution

University of North Carolina at Charlotte

Abstract

Planar photonic crystals and other microstructured surfaces have important applications in a number of emerging technologies. However, these structures can be difficult to fabricate in a consistent manner. Rapid, precise measurements of critical parameters are needed to control the fabrication process, but current measurement techniques tend to be slow and often require that the sample be modified in order to make the measurement. Optical scattering can provide a rapid, non-destructive, and precise method for measuring these structures, and optical scatterometry is a good candidate technique for measuring micro-structured surfaces for process control. However, variations in the profile, such as those caused by edge roughness, can make significant contributions to the uncertainty in scatterometry measurements. Because of the multi-dimensional nature of the problem, modeling these variations can be computationally expensive. This dissertation examines the effects of edge roughness on optical scatterometry signals. Rigorous numerical simulations show that the effects of edge roughness are sensitive to the correlation length and the frequency content of the roughness as well as its amplitude. However, these rigorous calculations are computationally expensive. A less computationally expensive model based on a generalized Bruggeman effective medium approximation is developed and shown to be effective for modeling the effects of short correlation length edge roughness on optical scatterometry signals.

Genre

doctoral dissertations

Subjects--Topics

Optics
Nanotechnology

Degree

Ph.D.

Keywords

Effective Medium Approximation
Gratings
Line Edge Roughness
Reflectance
Scatterometry

Subject Area

Optical Science and Engineering

Advisor(s)

Suleski, Thomas

Committee Members

Davies, Angela
Gbur, Greg
Astratov, Vasily
Fiddy, Michael
Hocken, Robert

Degree Note

Thesis (Ph.D.)--University of North Carolina at Charlotte, 2009.

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Rights Holder Information

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Identifier

Bergner_uncc_0694D_10078

Permalink

http://hdl.handle.net/20.500.13093/etd:1368