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Proceedings Paper

Optical properties of alternating phase-shifting masks
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Paper Abstract

The 2005 edition of the International Technology Roadmap for Semiconductors specifies that phase errors of alternating phase-shifting masks (APSM) should approach ± 1 degree by 2008. This specification is reasonably motivated by the desire to keep imaging effects of mask errors below those of aberrations of projection optics, but it implies a questionable assumption that the phase of a feature is a well-defined quantity. Variations of both phase and amplitude across apertures are significant. In addition to the variables that we expect mask manufacturers to control, such as trench depth, wall slope, and bottom-surface flatness, phase also depends on polarization, illumination angle, widths of apertures, and proximity of other features. Dependence of phase on variables in addition to trench depth will increase as we shrink to pitches available with immersion lithography, perhaps restricting layouts that can be printed with APSM technology. Mask manufacturers must develop methods to set and measure phase to necessary tolerance.

Paper Details

Date Published: 20 October 2006
PDF: 10 pages
Proc. SPIE 6349, Photomask Technology 2006, 63491B (20 October 2006); doi: 10.1117/12.686147
Show Author Affiliations
Bob Gleason, Intel Corp. (United States)
Wen-Hao Cheng, Intel Corp. (United States)

Published in SPIE Proceedings Vol. 6349:
Photomask Technology 2006
Patrick M. Martin; Robert J. Naber, Editor(s)

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