Method for Film Thickness Mapping with an Astigmatic Optical Profilometer

Liao, Hsien-Shun; Cheng, Shih-Han; Hwu, En‐Te

doi:10.3390/s22082865

Cited by 3 publications

(2 citation statements)

References 29 publications

(32 reference statements)

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“…Profilometer on the other hand is an easy to use and compact optical profiler. The main advantages of the profilometer are its fast scanning speed, which results in a reaction time of the distance sensor that is less than 0.1 ms, high bandwidth, a compact size, and low cost [25,26].…”

Section: Discussionmentioning

confidence: 99%

Profilometry and atomic force microscopy for surface characterization

Li¹,

Guan²

2023

Nano TransMed

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Aim: This study aims to evaluate and compare the profilometry and atomic force microscopy (AFM) for characterization of biomaterial surfaces. Method: The clinically commonly used titanium (Ti) was used as the specimen. Each of the specimen was prepared by different grits of sandpapers, including 2000, 1000, 800, 600, 400, 220, 180, and 100 grits. An unpolished Ti plate served as the control. Surface characterization of the Ti specimens was examined using profilometry and AFM. Results: Both profilometry and AFM were capable of producing two-dimensional (2D) and three-dimensional (3D) topography. The scanning speed of profilometry (12 ± 5 s/image) was faster than that of AFM (250 ± 50 s/image) (p < 0.01). The resolution of AFM was relatively higher than profilometry. AFM produced more precise value, especially at nano-scale. When the Ti surface roughness was less than 0.2 μm, the results of surface roughness measured by profilometry and AFM were similar (mean difference = 0.01 ± 0.03, p = 0.81). When the Ti surface roughness was more than 0.3 μm, the surface roughness measured by profilometry was slightly higher than that by AFM (mean difference = 0.43 ± 0.15, p = 0.04). Conclusion: Profilometry and AFM are both useful techniques for the characterization of biomaterial surfaces. Profilometry scanned faster than the AFM but produced less detailed surface topography. Both technologies provided similar measurement when the roughness was less than 0.2 μm. When the Ti surface roughness was more than 0.3 μm, the surface roughness measured by profilometry was slightly higher than that by AFM.

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Section: Discussionmentioning

confidence: 99%

Profilometry and atomic force microscopy for surface characterization

Li¹,

Guan²

2023

Nano TransMed

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“…Therefore, the astigmatic profilometer is able to provide a high spatial resolution image, which has been utilized for various applications, such as bio-molecular sensing and cell imaging [18][19][20]. Previous studies have demonstrated that the astigmatic profilometer can measure not only the surface morphology but also the film thickness [21]. Moreover, the z-axis modulation mode of the astigmatic profilometer enables measurement of the S curve at each image pixel [22,23].…”

Section: Introductionmentioning

confidence: 99%

Real-Time Reflectance Measurement Using an Astigmatic Optical Profilometer

Liao

Huang

Syu-Gu

et al. 2022

Sensors

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An astigmatic optical profilometer with a commercial optical pickup head provides benefits, such as high resolution, compact size, and low cost. To eliminate artifacts caused by complex materials with different reflectances, a z-axis modulation mode is proposed to obtain quantitative surface morphology by measuring S curves on all image pixels. Moreover, the slope of the linear region in the S curve shows a positive relationship with the surface reflectance. However, the slope was calculated using an offline curve fitting method, which did not allow real-time reflectance imaging. Furthermore, quantitative reflectance data were unavailable because of the lack of calibration. In this study, we propose a novel method for real-time reflectance imaging by measuring the amplitude of a focus error signal (FES). The calibration results displayed a linear relationship between the FES amplitude and reflectance. The reflectance image of a grating sample with chrome patterns on a glass substrate demonstrates accurate reflectance measurements with a micrometer spatial resolution.

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Incoherent partial superposition modeling for single-shot angle-resolved ellipsometry measurement of thin films on transparent substrates

Peng,

Wang,

Gao

et al. 2024

Opt. Express

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Ellipsometric measurement of transparent samples suffers from substrate backside reflection challenges, including incoherent and partial superposition issues. The recently developed angle-resolved ellipsometry (ARE) can naturally eliminate the backside reflections of substrates with a micro-spot equivalent thickness or thicker; however, for thinner substrates, ARE working with general incoherent backside reflection models shows significant inaccuracy or measurement failure. In this paper, an incoherent partial superposition (IPS) model is proposed to characterize the optical superposition effect between the frontside and uncertain backside reflections from an unknown substrate. IPS introduces a cosine-like correction of the backside reflection, corresponding to the overlapping-area change of backside and frontside reflections along with incident angles. Benefiting from ARE’s wide-angle spectral imaging capability, IPS achieves single-shot measurement of thin film thicknesses on transparent substrates of unknown thickness. An ARE system was built and calibrated regarding the linear relationship between the cosine-corrected angular frequencies and substrate thicknesses. Then, commercial ITO films on glasses of different thicknesses ranging from 200 to 1000 µm were measured. Experimental results show that IPS-ARE results in a root-mean-square accuracy error of ∼1 nm in film thickness measurement and provides a ∼77% error reduction from general incoherent backside reflection models.

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Method for Film Thickness Mapping with an Astigmatic Optical Profilometer

Cited by 3 publications

References 29 publications

Profilometry and atomic force microscopy for surface characterization

Profilometry and atomic force microscopy for surface characterization

Real-Time Reflectance Measurement Using an Astigmatic Optical Profilometer

Incoherent partial superposition modeling for single-shot angle-resolved ellipsometry measurement of thin films on transparent substrates

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