The distorted helix: thin film extraction from scanning white light interferometry

Mansfield, Daniel

doi:10.1117/12.664036

Cited by 25 publications

(12 citation statements)

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“…For the measurement of constrained surfaces such as step heights and gauge blocks this is sufficient to provide traceability. However, the popularity of SWLI has led to its use in circumstances that are far removed from traditional gauge block interferometry and SWLI manufacturers have been quick to cater for these demands by including, for example, specialised software to estimate areal surface texture parameters and film thickness [6,7]. In these cases, the accuracy of SWLI is much more difficult to define.…”

Section: Introductionmentioning

confidence: 99%

Surface measurement errors using commercial scanning white light interferometers

Gao

Leach

Petzing

et al. 2007

Meas. Sci. Technol.

178

103

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Abstract:This paper examines the performance of commercial scanning white light interferometers in a range of measurement tasks. A step height artefact is used to investigate the response of the instruments at a discontinuity, while gratings with sinusoidal and rectangular profiles are used to investigate the effects of surface gradient and spatial frequency. Results are compared with measurements made with tapping mode atomic force microscopy and discrepancies are discussed with reference to error mechanisms put forward in the published literature. As expected it is found that most instruments report errors when used in regions close to a discontinuity or those with a surface gradient that is large compared to the acceptance angle of the objective lens. Amongst other findings, however, we report systematic errors that are observed when the surface gradient is considerably smaller. Although these errors are typically less than the mean wavelength they are significant compared to the instrument resolution and indicate that current scanning white light interferometers should be used with some caution if sub-wavelength accuracy is required.

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Section: Introductionmentioning

confidence: 99%

Surface measurement errors using commercial scanning white light interferometers

Gao

Leach

Petzing

et al. 2007

Meas. Sci. Technol.

178

103

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“…It may be shown that through performing SWLI measurements on a thin film coated substrate (single or multi-layer) together with a 'reference' substrate, such as the glass BK7, it is possible to construct the HCF function [1]. This is defined as the product of the conjugate of the net electrical field reflectance from the 'reference' together with the thin-film/'reference' quotient of the Fourier transform positive frequency sidebands corresponding to the series of SWLI intensity values surrounding the zero path…”

Section: Discussionmentioning

confidence: 99%

Thin film extraction from scanning white light interferometry

Mansfield

2007

Optifab 2007: Technical Digest

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“…For the system, some approaches to model-based CSI approximate incident angle as a single value averaged over the NA. 11,15 This simplifies computation to a one-dimensional integration over k and allows a straightforward field calibration using a conventional imaging tubelens in the intended measurement configuration. However, such approaches are limited to lower NA systems.…”

Section: Previous Approachesmentioning

confidence: 99%

“…It has been presented in various forms, [8][9][10][11][12] all using frequency-domain analysis to combine models for the system and of the part being measured. Thus a caveat with model-based CSI is that film properties must be at least partly known to bound the search space and avoid degenerate solutions.…”

Section: Overviewmentioning

confidence: 99%

Applications of model-based transparent surface films analysis using coherence-scanning interferometry

Fay

Dresel

2017

Opt. Eng

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Abstract. Surface metrology must increasingly contend with submicron films, whose prevalence now extends to products well beyond semiconductor devices. For optical technologies such as coherence-scanning interferometry (CSI), transparent submicron films pose a dual challenge: film effects can distort the measured top surface topography map and metrology requirements may now include three-dimensional maps of film thickness. Yet CSI's sensitivity also presents an opportunity: modeling film effects can extract surface and thickness information encoded in the distorted signal. Early model-based approaches entailed practical trade-offs between throughput and field of view and restricted the choice of objective magnification. However, more recent advances allow full-field surface films analysis using any objective, with sample-agnostic calibration and throughput comparable to film-free measurements. Beyond transparent films, model-based CSI provides correct topography for any combination of dissimilar materials with known visible-spectrum refractive indices. Results demonstrate single-nm self-consistency between topography and thickness maps.

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The distorted helix: thin film extraction from scanning white light interferometry

Cited by 25 publications

References 0 publications

Surface measurement errors using commercial scanning white light interferometers

Surface measurement errors using commercial scanning white light interferometers

Thin film extraction from scanning white light interferometry

Applications of model-based transparent surface films analysis using coherence-scanning interferometry

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