Diffraction gratings for submicron linewidth measurement

Optics: measuring and testing – By dispersed light spectroscopy – Utilizing a spectrometer

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356357, 356384, G01B 902

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active

054227232

ABSTRACT:
A test structure and a method of using it for measuring submicron linewidths. Diffraction gratings are made with lines having an unknown linewidth. The grating has a pitch comprises of multiple lines and multiple spaces. This permits a wider "effective pitch" resulting in an increased number of observable diffraction orders. Each order provides an intensity measurement, which can be substituted into a diffraction intensity equation in which intensity is a function of linewidth and other unknown variables. At least as many intensity measurements are obtained as are unknown variables so that a system of equations can be solved for the linewidth. In practice, if the grating lines are made in the same manner as other lines of a product, the width of the latter can be inferred.

REFERENCES:
patent: 4330213 (1982-05-01), Kleinknecht et al.
"Continuous Optical Measurement of the Dry Etching of Silicon Using the Diffraction of a Lamellar Grating", Geraldo F. Mendes, Lucila Cescato, Jaime Frejlich, Edmondo S. Braga, and Alaide P. Mammana, J. Electrochem. Soc.: Solid-State Science and Technology, Jan. 1985, pp. 190-193.
"In Situ Wafter Monitoring for Plasma Etching", Dennis S. Grimard, Fred L. Jerry, Jr., and Michael E. Elta, University of Michigan, Department of Electronic Engineering and Computer Science, 1301 Beal Ave., Ann Arbor, Mich. 48109-2122.
"Optical Monitoring of the Etching of SiO.sub.2 and Si.sub.8 N.sub.4 on Si by the Use of Grating Test Patterns", H. P. Kleinknecht and H. Meier, J. Electrochem. Soc.: Solid-State Science and Technology, May 1978, pp. 798-803.
"A Simple Technique for Linewidth Measurement of Gratings on Photomasks", S. Sohail H. Naqvi, Susan Gasper, Kirt Hickman, and John R. McNeil, Center for High Technology Materials, University of New Mexico, Albuquerque, N. Mex. 87131.
"In Situ Monitoring of Sub-micron Linewidths using a Diffraction Grating Test Pattern", Phillip Chapados, Ajit Paranjpe, Jimmy Hosch, and Cecil Davis, Texas Instruments Inc.

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