Method of selecting photomask blank substrates

Radiation imagery chemistry: process – composition – or product th – Radiation modifying product or process of making – Radiation mask

Reexamination Certificate

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C430S030000

Reexamination Certificate

active

07070888

ABSTRACT:
A photomask blank substrate is selected for use in a process where at least a masking film or a phase shift film is deposited on a top surface of a photomask blank substrate to form a photomask blank, the deposited film is patterned to form a photomask, and the photomask is mounted in an exposure tool. The substrate is selected by simulating a change in shape in the top surface of the substrate, from prior to film deposition thereon to when the photomask is mounted in the exposure tool; determining the shape of the substrate top surface prior to the change that will impart to the top surface a flat shape when the photomask is mounted in the exposure tool; and selecting, as an acceptable substrate, a substrate having this top surface shape. The selected substrate has an optimized top surface shape that improves productivity in photomask fabrication.

REFERENCES:
patent: 6537844 (2003-03-01), Itoh
patent: 2004/0100624 (2004-05-01), Hagiwara et al.
patent: 2005/0019676 (2005-01-01), Nakatsu et al.
patent: 2005/0019677 (2005-01-01), Nakatsu et al.
patent: 2005/0020083 (2005-01-01), Numanami et al.
patent: 2003-50458 (2003-02-01), None

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