Abstract
Demand for higher efficiency in the semiconductor manufacturing industry is continually increasing. In particular, nano defects measurement on patterned or bare Si semiconductor wafer surfaces is an important quality control factor for realizing high productivity and reliability of semiconductor device fabrication. Optical methods and electron beam methods are conventionally used for the inspection of semiconductor wafers. Because they are nondestructive and suitable for high-throughput inspection, optical methods are preferable to electron beam methods such as scanning electron microscopy, transmission electron microscopy, and so on. However, optical methods generally have an essential disadvantage about lateral spatial resolution than electron beam methods, because of the diffraction limit depending on the optical wavelength. In this research, we aim to develop a novel laser-scanning imaging method that can be applied to nano-/micro manufacturing processes such as semiconductor wafer surface inspection to allow lateral spatial super-resolution imaging with resolution beyond the diffraction limit. In our proposed method, instead of detecting the light intensity value from the beam spot on the inspection surface, the light intensity distribution, which is formed with infinity corrected optical system, coming from the beam spot on the inspection surface is detected. In addition, nano scale shifts in the beam spot are applied for laser spot scanning using a conventional laser-scanning method in which the spots are shifted at about a 100 nm pitch. By detecting multiple light intensity distributions due to the nano scale shifts, a super-resolution image reconstruction with resolution beyond the diffraction limit can be expected. In order to verify the feasibility of the proposed method, several numerical simulations were carried out.
About the authors
Hiroki Yokozeki received his Bachelor’s Degrees in Department of Precision Engineering from the University of Tokyo, Japan, in 2013. Currently, he attends to the master’s course at the Department of Precision Engineering of the University of Tokyo, Japan. His current research interests include optical super resolution for semiconductor industry. He is a member of JSPE, Japan Society for Precision Engineering.
Ryota Kudo received his Bachelor’s, Master’s and Doctor’s Degrees in the Department of Precision Engineering from the University of Tokyo, Japan, in 2007, 2009 and 2013, respectively. After completing his doctor course, he worked as a Project Researcher in the Department of Precision Science and Technology, Graduate School of Engineering, Osaka University, Japan. His current research interests include resolution improvement of optical microscopy with super-resolution image reconstruction using structured light.
Satoru Takahashi is a Professor of the Research Center for Advanced Science and Technology (RCAST), The University of Tokyo, Japan. He received his Bachelor’s, Master’s, and Doctor’s Degrees in Osaka University, Japan in 1993, 1995, and 2002. He currently leads the Photon based Advanced Manufacturing Science Division of the RCAST. His research interests include the nano-in-process measurement and nano-3D-processing based on the advanced optics using localized photon energy such as evanescent light, near-field light, and so on. He is a member of the CIRP, ASPE, euspen, JSPE and JSME.
Kiyoshi Takamasu is a Professor of the Department of Precision Engineering in the University of Tokyo, Japan since 2001. He received his Bachelor’s, Master’s and Doctor Degree in Precision Engineering from the University of Tokyo, in 1977, 1979 and 1982, respectively. His research interests include precision measurement, coordinate measurement, nanometre measurement, and calibration of precision instruments. He acted as a Visiting Researcher at Department of Engineering, University of Warwick, UK in 1990. He is a member of the euspen, ASPEN, JSPE, RSJ, IEEJ and SICE. He is a board member of ASPEN.
Acknowledgments
This work was partially supported by a Grant-in-Aid for Scientific Research by the Japanese Ministry of Education, Culture, Sports, Science and Technology.
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