Deflectometry vs. interferometry

Häusler, Gerd; Faber, Christian; Olesch, Evelyn; Ettl, Svenja

doi:10.1117/12.2020578

Cited by 56 publications

(20 citation statements)

References 8 publications

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“…The scanning techniques are time-consuming. The interferometry requires extremely strict measurement environment and quite inflexible and costly compensation optics [5,6]. Those instruments usually are a compromise between accuracy, spatial resolution and throughput.…”

Section: Introductionmentioning

confidence: 99%

High-accuracy inspection of defects and profile of wafers by phase measuring deflectometry

Yue

Zhao

et al. 2014

SPIE Proceedings

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The demands of the less-defective and high-flatness wafers are urgent in many wafer based technologies ranging from micro-electronics to the current photovoltaic industry. As the wafer becomes thinner and larger to cope with the advances in those industries, there is an increasing possibility of the emerging of crack and warp on the wafer surface. High-accuracy inspection of defects and profile are thus necessary to ensure the reliability of device. Phase measuring deflectometry(PMD) is a fast, cost-effective and high accuracy measurement technology which has been developed in recent years. As a slope measurement technology, PMD possesses a high sensitivity. Very small slope variation will lead to a large variation of the phase. PMD is very possible to have a good performance in the wafer inspection. In this paper, the requirements of the wafer inspection in the industries are discussed, and compatibility of PMD and those requirements is analyzed. In the experimental work, PMD gets the slope information of the wafer surface directly. The curvature or height information can be acquired simply by the derivation or integral of the slope. PMD is proved to make a superior result in high-precision defect detecting and shape measurement of wafer by the analysis of experiment results.

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Section: Introductionmentioning

confidence: 99%

High-accuracy inspection of defects and profile of wafers by phase measuring deflectometry

Yue

Zhao

et al. 2014

SPIE Proceedings

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“…For a comparison of both techniques see e.g. [1][2][3][4]. Deflectometry measures the shape of specular surfaces by tracing the reflection of a structured, incoherent light source.…”

Section: Introductionmentioning

confidence: 99%

Improving the calibration of phase measuring deflectometry by a polynomial representation of the display shape

Bartsch

Kalms

Bergmann

2019

J. Eur. Opt. Soc.-Rapid Publ.

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Background: Phase measuring deflectometry is a highly precise and full field metrology technique for specular surfaces based on the distortion of known reference patterns observed as a reflection at the surface under test. Typically, liquid crystal displays are employed to provide the required patterns. Due to a lack of research, these displays are used without sufficient calibration. Methods: In this work, we present an enhanced calibration for phase measuring deflectometry, taking flatness deviations of the display surface into account. The display shape is modelled as a polynomial surface whose coefficients are determined by minimizing the retrace error in a global optimization procedure during calibration. This approach does not require any additional measurements or hardware. Improvements due to the enhanced calibration model are qualified experimentally using a flat and a spherical concave mirror. Results and conclusion: The model-based parameterization of the display surface yields significant improvement on both samples. The peak to valley (PV) of measured deviations on the plane mirror are reduced by 67% to 0.55 μm. Measuring the spherical sample without the display parameterization leads to a rather large shape deviation of 33.40 μm PV which is reduced by 94% to 1.98 μm. The viability of our approach confirms the dominant role of flatness deviations of the display surface as an error source in absolute shape measurement using phase measuring deflectometry.

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“…However, the dynamic range of the interferometric testing is quite small, and it can only measure the surface departure within a few wavelengths from reference shape [8,9]. Specifically designed null optics and compensation optics are generally required in the testing of complex surfaces with large aberration, making the testing system very costly and inflexible [10][11][12]. Besides, the interferometry has high requirement on the calibration of testing system [13], which determines its achievable accuracy.…”

Section: Introductionmentioning

confidence: 99%

General testing method for refractive surfaces based on reverse Hartmann test

Wang

Gong

et al. 2017

Applied Optical Metrology II

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The testing technique with high dynamic range is required to meet the measurement of refractive wavefront with large distortion from test refractive surface. A general deflectometric method based on reverse Hartmann test is proposed to test refractive surfaces. Ray tracing of the modeled testing system is performed to reconstruct the refractive wavefront from test surface, in which computer-aided optimization of system geometry is performed to calibrate the geometrical error. For the refractive wavefront error with RMS 255 μm, the testing precision better than 0.5 μm is achieved.

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Deflectometry vs. interferometry

Cited by 56 publications

References 8 publications

High-accuracy inspection of defects and profile of wafers by phase measuring deflectometry

High-accuracy inspection of defects and profile of wafers by phase measuring deflectometry

Improving the calibration of phase measuring deflectometry by a polynomial representation of the display shape

General testing method for refractive surfaces based on reverse Hartmann test

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