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Proceedings Paper

Exposure monitor structure
Author(s): Alexander Starikov
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Paper Abstract

A novel exposure monitor structure (EMS) is proposed as a sensitive means to monitor or measure effective exposure dose in the optical lithographic printing. Like windows of graduated transmittance, it is very sensitive to dose, but not to focus. On the other hand, EMS is compact to allow placement in the kerf or device layouts and it is measurable by automated rctetrology tools. EMS is built in the conventional reticles by arranging a set of stripes of chrome and glass on the period near MTF cut-off in a manner simulating transmission wedges on both sides of a conventional line. Since the fine structure of EMS is not resolved by the optical lithography tool used for printing, it performs like a transmission wedge. Conventional linewidth measurements of a printed EMS image are used to monitor exposure dose. Coupled with a calibration curve, sensitive dose measurements can also be made. Modelling of printing of EMS and of a conventional line on an optical stepper indicates that printed linewidth of EMS changes much faster as the function of dose. EMS also displays relatively little sensitivity to defocus. Conventional 5X reticles with EMS were built. Exposure sequences were carried out on a G-line stepper. Linewidth measurements of printed EMS and of conventional lines were done on a typical linewidth measurement tool. Experiment confirms that linewidth of printed EMS is much more sensitive to dose than that of a conventional line. Once linewidth of EMS is established at the desirable dose, EMS may be used to set that dose in the subsequent runs. With more accurate dose set-up and job disposition decisions, higher product tolerance can be achieved with existing equipment and process.

Paper Details

Date Published: 1 June 1990
PDF: 10 pages
Proc. SPIE 1261, Integrated Circuit Metrology, Inspection, and Process Control IV, (1 June 1990); doi: 10.1117/12.20057
Show Author Affiliations
Alexander Starikov, IBM/East Fishkill Facility (United States)

Published in SPIE Proceedings Vol. 1261:
Integrated Circuit Metrology, Inspection, and Process Control IV
William H. Arnold, Editor(s)

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