Manufacturing method and apparatus of phase shift mask blank

The manufacturing method of a photo mask blank having at least a thin film for forming a pattern on a transparent substrate, said method comprising steps of:

• setting a substrate in a horizontal position where a surface of the substrate on which said thin film is formed faces upward, and said surface of the substrate and a surface of a sputtering target are in opposed position with a center axis of said target deviating from a center axis of said substrate surface, said sputtering target being in a single number,
• sputtering the target while rotating said substrate around its center axis so as to form said thin film,
• wherein the target and the substrate are disposed so that opposite surfaces of said substrate and the target form an angle between 10 to 30 degrees,
• an offset distance, which is defined as a distance between a center axis of the substrate and a straight line passing through a center of the target and extended in parallel to the center axis of the substrate, is determined so that the straight line does not pass through the substrate, and so that a straight line passing through an edge of the target adjacent to the substrate and falling vertically to a plain extended from the surface of the substrate does not pass through the surface of the substrate.

An apparatus for manufacturing a photo mask blank having at least a thin film for forming a pattern on a transparent substrate by sputtering, said apparatus comprising:

• a substrate holder placed in a horizontal position so that a surface of the substrate on which said thin film is formed faces upward, and so that said surface of the substrate and a surface of a sputtering target are in opposed position with a center axis of said target deviating from a center axis of said substrate surface, said sputtering target being in a single number, and
• means for rotating said substrate around its center axis during the formation of the film,
• wherein the target and the substrate are disposed so that opposite surfaces of said substrate and the target form an angle between 10 to 30 degrees,
• an offset distance, which is defined as a distance between a center axis of the substrate and a straight line passing through a center of the target and extended in parallel to the center axis of the substrate, is such that the straight line does not pass the through substrate, and so that a straight line passing through an edge of the target adjacent to the substrate and falling vertically to a plain extended from the surface of the substrate does not pass through the surface of the substrate.