Photomask, manufacturing method thereof, and electronic device manufacturing method

摘要

A photomask includes a transparent substrate and an opaque film formed on the transparent substrate. The opaque film is configured to form a device pattern with which a wafer is to be exposed; and at least one pair of assist patterns is formed by the opaque film, one assist pattern on each side of the device pattern on the transparent substrate. The size of each assist pattern of the pair of assist patterns is such that the assist pattern is not resolved on the wafer. A part of each assist pattern of the pair of assist patterns includes step portions.