Method of manufacturing photomask blank and photomask blank

摘要

In a chamber (50), a quartz substrate (10) having a main surface on which an optical film (20) is formed is put on a susceptor (30). A flash lamp (60) is housed in a lamp house (90), and the optical film (20) is irradiated with flash light through two quartz plates (70a and 70b). A transmittance adjustment region (80) is formed on a surface of the quartz plate (70b) of the two quartz plates (70a and 70b), and the amount of light with which the optical film (20) is irradiated has in-plane distribution. If the optical film (20) is irradiated with the flash light, optical characteristics of the optical film (20) change on the received irradiation energy. Hence, for example, the characteristics of the optical film are not uniform, the optical film is irradiated with flash light having such irradiation energy distribution that cancels the in-plane distribution.