Method of increasing the shelf life of a photomask substrate

Details Method of increasing the shelf life of a photomask substrate Method of increasing the shelf life of a photomask substrate

2006-11-14

2006-11-14

Young, Christopher G. (Department: 1756)

Radiation imagery chemistry: process, composition, or product th

Radiation modifying product or process of making

Radiation mask

C430S296000, C430S311000, C430S330000, C430S942000, C430S945000

Reexamination Certificate

active

07135256

ABSTRACT:
In photomask making, the environmental sensitivity of a chemically amplified photoresist is eliminated, or at least substantially reduced, by overcoating the photoresist with a thin coating (topcoat) of a protective but transmissive material. To provide improved stability during the long time period required for direct writing of a photomask pattern, typically in the range of about 20 hours, the protective topcoat material is pH adjusted to be as neutral in pH as possible, depending on other process variable requirements. For example, a pH adjusted to be in the range from about 5 to about 8 is particularly helpful. Not only is the stability of the chemically amplified photoresist better during direct writing when the protective topcoat is pH adjusted, but a photoresist-coated substrate with pH adjusted topcoat over its surface can be stored longer prior to imaging without adverse consequences.

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