Japanese Inventors Develop Quadrangular Photomask Blank Substrate

ALEXANDRIA, Va., April 28 -- Masayuki Nakatsu, Tsuneo Numanami and Masayuki Mogi, all from Niigata-ken, Japan, Tsuneyuki Hagiwara and Naoto Kondo, both of Tokyo, and Masamitsu Itoh of Yokohama, Japan, have developed a photomask blank substrate.

According to the U.S. Patent & Trademark Office: "In a quadrangular photomask blank substrate with a length on each side of at least 6 inches, which has a pair of strip-like regions that extend from 2 to 10 millimetre(mm) inside each of a pair of opposing sides along an outer periphery of a substrate top surface, with a 2 mm edge portion excluded at each end, each strip-like region is inclined downward toward the outer periphery of the substrate, and a difference between maximum and minimum values for height from a least squares plane for the strip-like region to the strip-like region is at most 0.5 micrometre The substrate exhibits a good surface flatness at the time of wafer exposure."

The inventors were issued U.S. Patent No. 7,351,504 on April 1.

The patent has been assigned to Shin-Etsu Chemical Co. Ltd., Kabushiki Kaisha Toshiba and Nikon Corp., Tokyo.

The original application was filed on July 23, 2004, and is available at: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=7,351,504.PN.&OS=PN/7,351,504&RS=PN/7,351,504.

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