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8 August 1993 Use of amorphous silicon for deep-UV masks
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We explore the use of amorphous silicon as an alternative to chrome for deep UV masks. The primary advantage is that patterns may be dry etched. As masks' feature sizes continue to shrink, this dry etch capability of amorphous silicon can be a significant factor. Amorphous silicon has a further advantage of high absorbtivity over the 190 - 350 nm region. We have characterized the reflectivity and absorption of amorphous silicon, polysilicon, and chrome in the deep UV range from 190 nm to 365 nm. The optical properties of amorphous and polysilicon are very similar, but the superior homogeneity of amorphous silicon for etching suggests it as the preferred form. The absorbtivity of silicon exceeds that of chrome in this region (by about 20%); consequently a 700 A film is adequate to insure transmission of less than .01%. We have examined both optical and e-beam mask making processes. The amorphous silicon is deposited on quartz blanks by means of LPCVD. After removing the backside film, the pattern is transferred to the silicon using e-beam or optical exposure. The pattern is then developed by a dry plasma etch.
© (1993) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Charles H. Fields, William G. Oldham, and Richard J. Bojko "Use of amorphous silicon for deep-UV masks", Proc. SPIE 1927, Optical/Laser Microlithography, (8 August 1993);


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