Patent ID: 8021801

Claim:
A method for fabricating a photomask, the method comprising: forming a phase shift layer, a first chrome layer, an intermediate layer, and a second chrome layer sequentially over a transparent substrate, wherein a thickness of the second chrome layer is thinner than the first chrome layer; forming a photoresist pattern directly on the second chrome layer; etching the second chrome layer to form a second chrome pattern exposing a portion of the intermediate layer by using the photoresist pattern as an etching mask, the second chrome pattern defining a first dimension; measuring a critical dimension (CD) of the second chrome pattern; overetching the second chrome pattern when the measured CD is larger than a desired condition; forming an intermediate pattern having a second dimension by using the overetched second chrome pattern as an etch mask, wherein the second dimension is defined the desired condition; etching the first chrome layer and the phase shift layer using the overetched second chrome pattern and the intermediate pattern to form a first chrome pattern and a phase shift pattern, the phase shift pattern having the second dimension; and removing the second chrome pattern and the intermediate pattern to form a photomask having a light blocking region, a transmitting region, and a phase shift region.