Manufacturing method and apparatus of phase shift mask blank

A method of continuously manufacturing a plurality of photo mask blanks each having at least a thin film for forming a pattern on a transparent substrate, said method comprising a step of:

• using a sputtering method to continuously form said thin film on said transparent substrate,
• wherein said step of using the sputtering method to continuously form said thin film on said transparent substrate comprises steps of:
• successively subjecting a plurality of substrates to a series of processes of supplying the transparent substrate into a sputtering chamber, forming the thin film for forming the pattern in said sputtering chamber, and discharging the transparent substrate with the film formed thereon from said sputtering chamber;
• and supplying and discharging the transparent substrate at a constant interval in order to set a film formation time to be constant among the plurality of blanks, and
• at least first to fifth photo mask blanks after start of film formation are excluded from the photo mask blanks obtained in said step.