• Acta Photonica Sinica
  • Vol. 53, Issue 1, 0112003 (2024)
Tao LIU1, Zhibin WANG1, Jiaqi HU1, Yaonan HE1, Weichang JING1, Enjing CHEN2, Wenlong ZHOU3, Guoming YU1, Ning YANG4, Di ZHAO4, Guofeng ZHANG1, and Shuming YANG1、*
Author Affiliations
  • 1School of Mechanical Engineering,Xi'an Jiaotong University,Xi'an 710049,China
  • 2Ostar-optical Micro-nano Optoelectronics Co.,Ltd.,Xi'an 710077,China
  • 3Motic China Group Co.,Ltd.,Xiamen 361006,China
  • 4National Market Supervision Key Laboratory of Measurement Optics and Applications,Shaanxi Institute of Metrology Science,Xi'an 710100,China
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    DOI: 10.3788/gzxb20245301.0112003 Cite this Article
    Tao LIU, Zhibin WANG, Jiaqi HU, Yaonan HE, Weichang JING, Enjing CHEN, Wenlong ZHOU, Guoming YU, Ning YANG, Di ZHAO, Guofeng ZHANG, Shuming YANG. Research on Large Field-of-view White Light Interferometry Measurement System and Performance[J]. Acta Photonica Sinica, 2024, 53(1): 0112003 Copy Citation Text show less

    Abstract

    White Light Interferometry (WLI) is a classic low-coherence interferometry. The surface height information can be obtained with ultra-high precision through the positioning of zero optical path difference position of white light interference. At the same time, compared with point-sectioning laser confocal microscope, WLI is a surface-sectioning tomography technology. In particular, its vertical resolution is comparable to that of an atomic force microscope. White light interferometry measurement technology has been widely used in the inspection of semiconductor wafer defects, Micro-electromechanical System (MEMS) sensing structures, ultra-precision optical components, and film thicknesses. Generally, this technology originated in the late 1980 s in the United States, and domestic researches in this field started late, with the overall technology lagging behind. In terms of the instrumentation, although there have been breakthroughs, core components still rely on imports, such as interference objectives, nano-positioning scanners. A large field-of-view white light interferometric measurement system was built and tested. In this system, a domestic white light interference objective with a lateral magnification of 2 was used and a 0.5× adapter lens was preferably configured in the imaging system in front of the image detector. For the white LED illumination source, a suitable bandpass filter was theoretically evaluated and experimentally confirmed. The center wavelength was determined through the experimental curve of white light interference along the axial direction. The actual magnification of WLI system and the distortion of the field of view were achieved through imaging of a two-dimensional microscopic grid sample. The actual maximum field-of-view at the object side has reached 14 mm. By selectively filtering the spectrum of the white light source, the white light interference signal can be effectively modulated. According to this, the axial resolution and horizontal resolution can be changed within a certain range. For example, by changing the center wavelength of the incident light, the horizontal resolution can be changed according to the Rayleigh criterion. Experimental results show that: a more ideal white light interference axial response curve is obtained through suitable spectral filtering; the maximum field-of-view at the object side is as large as 14 mm; the measurement results of standard step samples with heights of 2.04 μm and 20.43 μm are 2.05 μm and 20.47 μm, and the repeatability (standard deviation) of 10 measurements is 12 nm and 16 nm, respectively. The measurement result of the 2.04 μm height step was also compared with the result obtained by the atomic force microscope. Actual measurements were conducted on the roughness sample, MEMS sensing structure and semiconductor wafer film, demonstrating the feasibility of the developed system in the field of three-dimensional optical non-destructive precision inspection. For large field-of-view WLI systems, the horizontal or lateral resolution is on the order of a few micrometers, so it is difficult to apply WLI to the three-dimensional reconstruction of fine microstructures. This is an important shortcoming of large field-of-view WLI systems. Besides, through research, it was found that for ultra-smooth surfaces, such as polished wafers, it is difficult to measure using traditional vertical scanning interferometry technology, and the phase shifting method should be used. Measurement of film thickness may be used to monitor morphological changes in biological transparent film layers. Further research can focus on high-performance white-light interference objectives, automation of the white-light interferometry measurement process, and implementation of large field-of-view high-resolution white-light interferometry methods.
    Tao LIU, Zhibin WANG, Jiaqi HU, Yaonan HE, Weichang JING, Enjing CHEN, Wenlong ZHOU, Guoming YU, Ning YANG, Di ZHAO, Guofeng ZHANG, Shuming YANG. Research on Large Field-of-view White Light Interferometry Measurement System and Performance[J]. Acta Photonica Sinica, 2024, 53(1): 0112003
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