A method for manufacturing a semiconductor includes: receiving a photomask substrate including a shielding layer; defining a chip region and a peripheral region adjacent to the chip region; forming a design pattern in the chip region; forming a reference pattern by emitting one first radiation shot and a beta pattern by emitting a plurality of second radiation shots in the peripheral region, wherein a pixel size of the first radiation shot is greater than a pixel size of the second radiation shot; comparing a reference roughness of a boundary of the reference pattern and a beta roughness of a boundary of the beta pattern; transferring the design pattern to the shielding layer if a difference between the reference roughness and the beta roughness is within a tolerance; and transferring the design pattern of the photomask to a semiconductor substrate.