Proceedings of the
9th International Conference of Asian Society for Precision Engineering and Nanotechnology (ASPEN2022)
15 – 18 November 2022, Singapore
doi:10.3850/978-981-18-6021-8_OR-11-0069
Galvo-Scanning Chromatic Confocal Microscopy for High-Speed 3-D Surface Measurement
1Department of Mechanical Engineering, National Taiwan University, No. 1, Section 4, Roosevelt Rd., Taipei City, 10617, Taiwan
2Taiwan Instrument Research Institute, National Applied Research Laboratory, Hsinchu, Taiwan
ABSTRACT
The article presents high-speed chromatic confocal microscopy for 3-D surface profilometry. Extremely high accuracy and efficiency of surface profilometry on microstructures are critically demanded in various manufacturing processes, such as semiconductors fabrication. A Galvo-scanning confocal measuring system is proposed to achieve high efficient area-scan chromatic confocal microscopy. The proposed optical system is designed to be fully telecentric through all the light illumination and imaging sections to satisfy full-field measurement without optical aberration. Optical line-scan illumination and imaging modules are designed to fit with an electrical-driven galvanometer for high-speed line scanning optically. Alarge measuring FOV with high chromatic measuring accuracy can be expected. To verify the developed probe's measuring precision and accuracy, pre-calibrated step-height gauges were tested to show that the measurement bias can be kept below 239 nm with a standard deviation of 126 nm. The measuring speed of the system can reach more than 8000 line/s when the galvanometer reaches its design specification. The measuring efficiency would be credited with a high level of scanning performance in the current state of the art in 3-D confocal microscopy.
Keywords: Automated optical inspection (AOI), chromatic confocal microscopy, galvanometer-scan, surface profilometry, optical aberration
1Department of Mechanical Engineering, National Taiwan University, No. 1, Section 4, Roosevelt Rd., Taipei City, 10617, Taiwan
2Taiwan Instrument Research Institute, National Applied Research Laboratory, Hsinchu, Taiwan
ABSTRACT
The article presents high-speed chromatic confocal microscopy for 3-D surface profilometry. Extremely high accuracy and efficiency of surface profilometry on microstructures are critically demanded in various manufacturing processes, such as semiconductors fabrication. A Galvo-scanning confocal measuring system is proposed to achieve high efficient area-scan chromatic confocal microscopy. The proposed optical system is designed to be fully telecentric through all the light illumination and imaging sections to satisfy full-field measurement without optical aberration. Optical line-scan illumination and imaging modules are designed to fit with an electrical-driven galvanometer for high-speed line scanning optically. Alarge measuring FOV with high chromatic measuring accuracy can be expected. To verify the developed probe's measuring precision and accuracy, pre-calibrated step-height gauges were tested to show that the measurement bias can be kept below 239 nm with a standard deviation of 126 nm. The measuring speed of the system can reach more than 8000 line/s when the galvanometer reaches its design specification. The measuring efficiency would be credited with a high level of scanning performance in the current state of the art in 3-D confocal microscopy.
Keywords: Automated optical inspection (AOI), chromatic confocal microscopy, galvanometer-scan, surface profilometry, optical aberration
