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Proceedings Paper

Sub-halfmicron lithography mask metrology: matching of the optical and mask system
Author(s): Mircea V. Dusa; Erik H. Rauch
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Paper Abstract

Subhalfmicron lithography process demands a reevaluation of the traditional mask metrology process. The matching of the optical and the mask system is the key factor of new mask metrology process developed to characterize typical 64 MB lithography masks. The matching of these subsystems represents the CD mask metrology system ability to detect mask process influences upon linewidth measurement results. To simplify the analysis, the effects of the optical system are separated from the effects of the mask system. Optical system effects are: lens NA, illumination technique, focus control. Mask effects are: feature size, feature polarity, proximity location and mask process step. The metric used to characterize the matching of the subsystems is the Depth Response Function (DRF). DRF is the edge contrast of the aerial image versus defocus step. Similar approach was used for optical lithography focus characterization. Characterization of the matching concept in terms of CD results shows that an optical system with transmitted-confocal reflected illumination techniques will produce better than 10 nm 3S repeatability when measures features throughput all mask process steps. An enhanced metrology algorithm was used to control the matching of optical and mask systems for 0.5 micrometers final and 0.8 micrometers rim shifter mask features. System influence upon CD results was reduced to maximum +/- 7 nm with large defocus and illumination variations.

Paper Details

Date Published: 3 November 1994
PDF: 11 pages
Proc. SPIE 2254, Photomask and X-Ray Mask Technology, (3 November 1994); doi: 10.1117/12.191947
Show Author Affiliations
Mircea V. Dusa, Technical Instrument Co. (United States)
Erik H. Rauch, Technical Instrument Co. (United States)

Published in SPIE Proceedings Vol. 2254:
Photomask and X-Ray Mask Technology
Hideo Yoshihara, Editor(s)

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