An optical proximity correction (OPC) photomask is provided. The photomask includes two opening patterns and a pair of scattering bar patterns. The two patterns are arranged on a substrate along a first direction and separated from each other by a predetermined distance. The pair of scattering bar patterns is arranged on the substrate along a second direction perpendicular to the first direction and adjacent to two opposing sides of each opening pattern. Each scattering bar pattern does not overlap with the opening patterns on the first and second directions as viewed from a cross sectional perspective. A phase shift of 180° exists between each opening pattern and each scattering bar pattern.