Patent ID: 9664997
Date: 2017-05-30
CPC Classifications: C03C,C23C,G03F

Claim:
1. A method of manufacturing a mask blank provided with a thin film on a transparent substrate, comprising: a step of preparing a transparent substrate having a pair of opposing main surfaces that is composed of a glass material having a hydrogen content of not more than −2.0×10 a step of forming a thin film composed of a material containing at least one of silicon and metal on one of the main surfaces of the transparent substrate, and a step of carrying out heating treatment or photo irradiation treatment on the transparent substrate on which the thin film has been formed; wherein, the absolute value of a variation of flatness in a predetermined region, as calculated based on a difference in shape obtained from the shape of one of the main surfaces of the transparent substrate prior to forming the thin film and the shape of one of the main surfaces of the transparent substrate exposed after removing the thin film, is not more than 100 nm.