Coma measurement by use of an alternating phase-shifting mask mark with a specific phase width
The correlation between the coma sensitivity of the alternating phase-shifting mask (Alt-PSM) mark and the mark's structure is studied based on the Hopkins theory of partially coherent imaging and positive resist optical lithography (PROLITH) simulation. It is found that an optimized Alt-PSM mark with its phase width being two-thirds its pitch has a higher sensitivity to coma than Alt-PSM marks with the same pitch and the different phase widths. The pitch of the Alt-PSM mark is also optimized by PROLITH simulation, and the structure of p=1.92{lambda}/NA and pw=2p/3 proves to be with the highest sensitivity. The optimized Alt-PSM mark is used as a measurement mark to retrieve coma aberration from the projection optics in lithographic tools. In comparison with an ordinary Alt-PSM mark with its phase width being a half its pitch, the measurement accuracies of Z7 and Z14 apparently increase.
- OSTI ID:
- 21175909
- Journal Information:
- Applied Optics, Vol. 48, Issue 2; Other Information: DOI: 10.1364/AO.48.000261; (c) 2009 Optical Society of America; Country of input: International Atomic Energy Agency (IAEA); ISSN 0003-6935
- Country of Publication:
- United States
- Language:
- English
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