The fabrication of phase shifting masks requires precise alignment between the primary and shifter layers. The MEBES^R IV electron-beam lithography system uses its SEM mode to acquire a video image of the phase shift mask (PSM) alignment mark. Digital signal- processing algorithms have been developed to accurately determine the locations of the marks. Alignment marks are acquired through various resist systems and film thicknesses. Machine control software translates and rotates the MEBES coordinate system to align it with the mask coordinate system, as determined by the location of the alignment marks. Results showing overlay accuracy between layers are presented.

Date Published: 26 March 1993
PDF: 7 pages
Proc. SPIE 1809, 12th Annual BACUS Symposium on Photomask Technology and Management, (26 March 1993); doi: 10.1117/12.142148

Published in SPIE Proceedings Vol. 1809:
12th Annual BACUS Symposium on Photomask Technology and Management
Scott Landstrom; Richard LaFrance, Editor(s)