Optical properties of alternating phase-shifting masks

Bob Gleason; Wen-Hao Cheng

doi:10.1117/12.686147

20 October 2006 Optical properties of alternating phase-shifting masks

Bob Gleason, Wen-Hao Cheng

Proceedings Volume 6349, Photomask Technology 2006; 63491B (2006) https://doi.org/10.1117/12.686147
Event: SPIE Photomask Technology, 2006, Monterey, California, United States

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.

Citation Download Citation

Bob Gleason and Wen-Hao Cheng "Optical properties of alternating phase-shifting masks", Proc. SPIE 6349, Photomask Technology 2006, 63491B (20 October 2006); https://doi.org/10.1117/12.686147

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