ALEXANDRIA, Va., June 18 -- United States Patent no. 12,326,656, issued on June 10, was assigned to HOYA Corp. (Tokyo) and TEKSCEND PHOTOMASK CORP. (Tokyo).
"Mask blank and method of manufacturing photomask" was invented by Hitoshi Maeda (Tokyo), Kazutake Taniguchi (Tokyo), Kazuaki Matsui (Tokyo) and Naoto Yonemaru (Tokyo).
According to the abstract* released by the U.S. Patent & Trademark Office: "A mask blank has a structure where a thin film for pattern formation and a hard mask film are stacked in this order on a transparent substrate, featured in that the thin film is formed of a material containing chromium, the hard mask film includes a stacked structure of a lower layer and an upper layer, the lower layer is formed of a material c...