METHOD OF DESIGNING MASK LAYOUT FOR IMAGE SENSOR

A mask layout design method includes designing a preliminary mask layout, designing a plurality of target mask layouts by inserting a plurality of preliminary assist patterns into the preliminary mask layout, generating an optical proximity correction (OPC) model based on the plurality of target mask layouts, obtaining a plurality of mask design images by using the OPC model, extracting a plurality of mask contour images, selecting a plurality of target patterns, producing a mask based on the plurality of target mask layouts, forming a real pattern on a substrate based on the mask, and selecting a final pattern from among the plurality of target patterns based on the formed real pattern. The preliminary mask layout includes a mask layout defining a pixel isolation structure that isolates a plurality of pixels, and the preliminary assist pattern has at least one of a cross or rectangular shape.