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Proceedings Paper

Image-height offset in TTL on-axis alignment method
Author(s): Noriaki Ishio; Keiji Fujiwara; Hitoshi Nagata
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Paper Abstract

The problems of the offset errors in the TTL alignment are studied. The further the position of alignment optics is from the center of the projection lens the bigger the offset error becomes. The lmageheight offset is the offset error caused by the position of alignment optics on the imaged field of projection lens. The maximum values of lmage. height offset for the dark and bright field alignment modes are O. 3p. m and O. O8tm respectively. The lmageheight offset is large with the dark field alignment because the stopper (spatial filter) in the optics is not fixed at the best place. 1 Recently the resolution of reduction projection photolithography has been improved to linewidth accuracy of 0. 5 pm. The required overlay accuracy is generally one fourth or one fifth of the pattern width thus a registration of the order of tens of nanometers is required for submicron devices fabrication. The overlay errors are divided into the intra4ield matching error and the registration error. The intra-field matching error consists of the difference in lens distortions between several steppers. If only one stepper is used to fabricate the device the overlay accuracy is almost equal to the registration accuracy. Many alignment methods have been developed in order to achieve a fine registration accuracy. Recently the g-line stepper has used two typical alignment methods. One is the TTL on axis alignment method

Paper Details

Date Published: 1 June 1990
PDF: 7 pages
Proc. SPIE 1264, Optical/Laser Microlithography III, (1 June 1990); doi: 10.1117/12.20219
Show Author Affiliations
Noriaki Ishio, Mitsubishi Electric Corp. (Japan)
Keiji Fujiwara, Mitsubishi Electric Corp. (Japan)
Hitoshi Nagata, Mitsubishi Electric Corp. (Japan)

Published in SPIE Proceedings Vol. 1264:
Optical/Laser Microlithography III
Victor Pol, Editor(s)

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