NDLI: Simple and accurate optical height sensor for wafer inspection systems

Content Provider	Springer Nature Link
Author	Shimura, Kei Nakai, Naoya Taniguchi, Koichi Itoh, Masahide
Copyright Year	2015
Abstract	An accurate method for measuring the wafer surface height is required for wafer inspection systems to adjust the focus of inspection optics quickly and precisely. A method for projecting a laser spot onto the wafer surface obliquely and for detecting its image displacement using a one-dimensional position-sensitive detector is known, and a variety of methods have been proposed for improving the accuracy by compensating the measurement error due to the surface patterns. We have developed a simple and accurate method in which an image of a reticle with eight slits is projected on the wafer surface and its reflected image is detected using an image sensor. The surface height is calculated by averaging the coordinates of the images of the slits in both the two directions in the captured image. Pattern-related measurement error was reduced by applying the coordinates averaging to the multiple-slit-projection method. Accuracy of better than 0.35 μm was achieved for a patterned wafer at the reference height and ±0.1 mm from the reference height in a simple configuration.
Starting Page	1
Ending Page	9
Page Count	9
File Format	PDF
ISSN	13406000
Journal	Optical Review
Volume Number	23
Issue Number	1
e-ISSN	13499432
Language	English
Publisher	The Optical Society of Japan
Publisher Date	2015-12-31
Publisher Place	Japan
Access Restriction	One Nation One Subscription (ONOS)
Subject Keyword	Optical displacement measurement Focus adjustment Slit projection Reflection asymmetry Image processing Wafer inspection Physics Optics, Optoelectronics, Plasmonics and Optical Devices Atomic, Molecular, Optical and Plasma Physics Quantum Optics Microwaves, RF and Optical Engineering
Content Type	Text
Resource Type	Article
Subject	Atomic and Molecular Physics, and Optics

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4	Project PI / Joint PI	Principal Investigator and Joint Principal Investigators of the project	Dr. B. Sutradhar bsutra@ndl.gov.in Prof. Saswat Chakrabarti will be added soon
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