Patent ID: 7228523

Claim:
A method of automatically correcting mask pattern data, wherein said mask pattern data is for producing a plurality of photo masks used in manufacturing processes of a semiconductor integrated circuit where cells including dummy cells are placed on a semiconductor chip, said method comprising: (a) merging tentatively an assistant mask layer into one of a plurality of main mask layers, wherein each of said plurality of main mask layers corresponds to one of said plurality of photo masks, said assistant mask layer includes a plurality of first regions, each of which corresponds to one of said dummy cells; (b) checking whether or not said one of the plurality of main mask layers and said merged assistant mask layer agree with a design rule; (c) replacing said one of the plurality of main mask layers with another one of said plurality of main mask layers, into which said assistant mask layer is merged, when a violation against said design rule is found in said step (b); and (d) converting said assistant mask layer into said merged one of said plurality of main mask layers, wherein said merged one of the plurality of main mask layers does not have a violation against said design rule.