Share Email Print

Proceedings Paper

The vortex mask: making 80-nm contacts with a twist!
Author(s): Marc David Levenson; Grace Dai; Takeaki Ebihara
Format Member Price Non-Member Price
PDF $17.00 $21.00

Paper Abstract

An optical vortex has a phase that spirals like a corkscrew. Since any nonzero optical amplitude must have a well-defined phase, the axis of a vortex (where the phase is undefined) is always dark. Printed in negative resist, lowest order vortices would produce contact holes with 0.21<0.5, roughly 80-200nm diameter, with 248nm exposure and NA=0.63. Arrays of vortices with kpitch>0.6 can be produced using a chromeless phase-edge mask composed of rectangles with phases of 0°, 90°, 180° and 270°. EMF and Kirchhoff-approximation simulations reveal that the image quality of the dark spots is excellent, and predict a process window with 15% exposure latitude and 400nm DOF for 80nm diameter spots on pitches ≥250nm at σ=0.15. EMF simulations predict that the 0-270° phase step will not be excessively dark if the quartz wall is vertical. Chrome spots at the centers can control the diameters which otherwise are set by the parameters of the imaging system and exposure dose. Unwanted vortices can be erased from the image by exposing with a second, more conventional, trim mask. This method would be superior to the other ways of producing sub-wavelength vias, but successful implementation requires the development of appropriate negative-tone resist processes.

Paper Details

Date Published: 27 December 2002
PDF: 11 pages
Proc. SPIE 4889, 22nd Annual BACUS Symposium on Photomask Technology, (27 December 2002); doi: 10.1117/12.467406
Show Author Affiliations
Marc David Levenson, M.D. Levenson Consulting (United States)
Grace Dai, Sigma-CAD Inc. (United States)
Takeaki Ebihara, Canon USA, Inc. (United States)

Published in SPIE Proceedings Vol. 4889:
22nd Annual BACUS Symposium on Photomask Technology
Brian J. Grenon; Kurt R. Kimmel, Editor(s)

© SPIE. Terms of Use
Back to Top
Sign in to read the full article
Create a free SPIE account to get access to
premium articles and original research
Forgot your username?