Optics: measuring and testing – By dispersed light spectroscopy – Utilizing a spectrometer
Patent
1991-02-27
1992-11-17
Turner, Samuel A.
Optics: measuring and testing
By dispersed light spectroscopy
Utilizing a spectrometer
356384, G01B 902
Patent
active
051647907
ABSTRACT:
For critical dimension (CD) metrology of photomasks, a laser scatterometer linewidth measurement tool provides noncontact rapid, and nondestructive measurement of linewidth. Calculation of the linewidth is based on a rigorous theoretical model, thus eliminating the need for calibrations. A chrome-on-glass diffraction grating is illuminated with a laser. A photodetector mounted behind the photomask measures the scattered power in each diffracted order. This provides data for the rigorous theoretical model which provides a relationship between the linewidth of the photomask grating and the fraction of total power diffracted into the transmitted zero-order. This scatterometer linewidth measurement technique provides a simple, rapid, nondestructive, and noncontact method of linewidth determination which takes into account the effect of the glass substrate on which the grating is placed. This technique is insensitive to variations in angle of incidence, spot size, position of the spot on the grating, polarization and wavelength.
REFERENCES:
patent: 4330213 (1982-05-01), Kleinknecht et al.
C-M Yuan, J. Shaw, W. Hopwell, "Modeling of optical alignment images for semiconductor structures," Proc. SPIE, vol. 1088, pp. 392-402, 1989.
D. Nyyssonen, B. Monteverde, "Linewidth Edge Detection Algorithm for Coherent Image Profiles," Proc. SPIE, vol. 1087, pp. 146-152, Feb. 1989.
D. Nyyssonen, "Practical method for edge detection and focusing for linewidth measurements on wafers," Opt. Eng., pp. 81-85, Jan. 1987.
H. P. Kleinknecht, H. Meier, "Linewidth Measurement on IC Masks and Wafers by Grating Test Patterns," Appl Optics, vol. 19, No. 4, pp. 525-533, Feb. 15, 1980.
M. G. Moharam, T. K. Gaylord, "Diffraction analysis of dielectric surface-relief gratings," Journal Opt Soc Am, vol. 72, pp. 1385-1392, Oct. 1982.
Gaspar Susan M.
Hickman Kirt C.
McNeil John R.
Naqvi S. Sohail H.
Kurtz, II Richard E.
Turner Samuel A.
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