METHOD FOR COMPENSATING COMA ABERRATION OF EXPOSURE APPARATUS

PURPOSE: A method for compensating coma aberration is to reduce asymmetry of a pattern and variations of the pattern such as shift using a selected phase shift mask. CONSTITUTION: It determines a pattern variation happened when a non-phase shift mask including a transmitting region(R1l,R1c,R1r) and a shielding region is used at a photolithography process. As any selected region of the transmitting region is covered by a phase shift layer, a selected phase shift mask indicate of a pattern variation opposed to the pattern variation is formed on the selected region. The photolithographic process uses the selected phase shift mask, in the stead of the non-phase shift mask. The step of forming the selected phase shift mask comprises the steps of: covering the selected region with a phase shift layer to form the phase shift mask; determining the pattern variation happened when the phase shift mask is used; and repeating the steps until the determined pattern variation becomes to be opposed to a pattern variation happened by the coma aberration.