Chinese Optics Letters, Volume. 20, Issue 9, 091201(2022)

White light interferometry with spectral-temporal demodulation for large-range thickness measurement

Yunlong Zhu1,2, Zhuoran Li1,2, Xu Lu1,2, Yonggui Yuan1,2,*, and Jun Yang2,3,4,**
Author Affiliations
  • 1Key Laboratory of In-fiber Integrated Optics, Ministry of Education of China, Harbin Engineering University, Harbin 150001, China
  • 2College of Physics and Optoelectronic Engineering, Harbin Engineering University, Harbin 150001, China
  • 3Guangdong Provincial Key Laboratory of Information Photonics Technology (Guangdong University of Technology), Guangzhou 510006, China
  • 4School of Information Engineering, Guangdong University of Technology, Guangzhou 510008, China
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    Film thickness measurement can be realized using white light interferometry, but it is challenging to guarantee high precision in a large range of thicknesses. Based on scanning white light interferometry, we propose a spectral-temporal demodulation scheme for large-range thickness measurement. The demodulation process remains unchanged for either coatings or substrate-free films, while some adjustments are made according to the estimated optical thickness. Experiments show that the single-point repeatabilities for 500 nm SiO2 coating and 68 µm substrate-free Si film are no more than 0.70 nm and 1.22 nm, respectively. This method can be further developed for simultaneous measurement of surface profile and film thickness.

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    1. Introduction

    Thin films play important roles in the fields of semiconductors, optoelectronics, integrated optics, etc. Following the increasing demand on thin film quality[1], precise measurement of film thickness is crucial to provide valuable feedback for the fabrication process. While dealing with transparent thin films, commercial ellipsometry systems[2] can give good results of film thickness, yet they can hardly measure surface profile and film thickness at the same time. On the contrary, white light interferometry (WLI) is well-known for surface profile measurement with high precision, and it shows great potential for simultaneous measurement of film thickness and surface profile[3], yet it is hard to measure a large range of thickness with high accuracy.

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    Yunlong Zhu, Zhuoran Li, Xu Lu, Yonggui Yuan, Jun Yang. White light interferometry with spectral-temporal demodulation for large-range thickness measurement[J]. Chinese Optics Letters, 2022, 20(9): 091201

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    Paper Information

    Category: Instrumentation, Measurement, and Optical Sensing

    Received: Feb. 2, 2022

    Accepted: May. 17, 2022

    Posted: May. 18, 2022

    Published Online: Jun. 16, 2022

    The Author Email: Yonggui Yuan (yuanyonggui@aliyun.com), Jun Yang (yangj@gdut.edu.cn)

    DOI:10.3788/COL202220.091201

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