Optical Measurement Of Contacts

Peter Waksman

doi:10.1117/12.953116

19 July 1989 Optical Measurement Of Contacts

Peter Waksman

Proceedings Volume 1087, Integrated Circuit Metrology, Inspection, and Process Control III; (1989) https://doi.org/10.1117/12.953116
Event: 1989 Santa Clara Symposium on Microlithography, 1989, San Jose, CA, United States

Abstract

Optical measurement of contacts and vias is possible because when a microscope is focused at a plane near to the bottom of a contact, light is reflected from the bottom and forms a characteristic image: a dark ring surrounding a brighter center. The dark ring image is common to a variety of substrates, including resist on poly, etched metal, nitride, resist on doped glass on grainy metal, etc.. Using image processing and dedicated measurement algorithms, it is possible to separate the dark ring from the brighter center by a "contour" or edge, and to measure the diameters (in x or y) and the area inside the contour. Also, by comparing these measurements against reference measurements it is possible to determine if the contact is open or closed. These measurements can be repeated with precision between .01 and .02 microns (depending on materials) and can be calibrated to a standard such as a SEM or an electrical test.

Citation Download Citation

Peter Waksman "Optical Measurement Of Contacts", Proc. SPIE 1087, Integrated Circuit Metrology, Inspection, and Process Control III, (19 July 1989); https://doi.org/10.1117/12.953116

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