Method for Film Thickness Mapping with an Astigmatic Optical Profilometer

Hsien Shun Liao*, Shih Han Cheng, En-Te Hwu

*Corresponding author for this work

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An astigmatic optical profilometer is a precision instrument with advantages such as high resolution, high bandwidth, a compact size, and low cost. However, current astigmatic optical profilometers measure only surface morphology, and their potential for capturing subsurface information remains underutilized. In this study, we developed a method for measuring the thickness of transparent thin films with an astigmatic optical profilometer. Experimental results demonstrate that the thickness of transparent films tens of micrometers thick can be accurately measured. The maximum thickness measurable through our system is approximately 100 µm, which may be increased to 1.2 mm through the use of a scanner with a greater travel range. A coupling problem occurs for films <25 µm in thickness. However, to solve this problem, we devised a decoupling method, which was
experimentally implemented to successfully measure a 18-µm-thick film. Moreover, the ability to obtain 3D images, including of both the upper and lower surfaces, was demonstrated.
Original languageEnglish
Article number2865
Issue number8
Number of pages9
Publication statusPublished - 2022


  • Astigmatism
  • Optical profilometer
  • Thickness measurement


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