Method of forming dummy pattern

1. A method of forming a dummy pattern on a mask for fabricating a semiconductor device, the method comprising:

calculating a separation distance in a device isolation area between first and second chip areas having different pattern densities;

comparing the separation distance and a first reference distance to determine whether or not the separation distance is larger than the first reference distance;

forming the dummy pattern in the device isolation area based on the comparison result, wherein:

the dummy pattern has a plurality of partitions;

the partitions have pattern densities according to a position of the respective partition;

a quantity of the partitions is based on the comparison result; and

at least one partition has a pattern density which is substantially equal to an average of the pattern densities of the first and the second chip areas.

2. The method according to claim 1 , wherein the quantity of the partitions is in the range of three to nine.

3. The method according to claim 2 , when the separation distance is larger than the first reference distance, forming the dummy pattern into first, second, third, fourth, and fifth partitions, wherein:

the third partition has a pattern density which is substantially equal to an average of the pattern densities of the first and second chip areas;

the first partition and the second partition have relatively lower pattern densities than the pattern density of the third partition; and

the fourth partition and the fifth partition have relatively higher pattern densities than the pattern density of the third partition.

4. The method according to claim 3 , wherein:

the first chip area has a lower pattern density than the second chip area;

a first group of partitions, including the first and the second partitions, is adjacent to the first chip area;

a second group of partitions, including the fourth and the fifth partitions, is adjacent to the second chip area; and

the third partition is positioned between the first group and the second group.

5. The method according to claim 2 , wherein:

when the separation distance is not larger than the first reference distance, judging whether or not the separation distance is larger than a second reference distance, the second reference distance being smaller than the first reference distance,

when the separation distance is larger than the second reference distance, forming the dummy pattern into first, second, and third partitions, wherein:

the second partition has a pattern density which is substantially equal to an average of the pattern densities of the first chip area and the second chip area;

the first partition has a relatively lower pattern density than the pattern density of the second partition; and

the third partition has a relatively higher pattern density than the pattern density of the second partition.

6. The method according to claim 5 , wherein if the separation distance is not larger than the second reference distance, forming the dummy pattern with a uniform pattern density.

7. The method according to claim 5 , wherein:

the first chip area has a lower pattern density than the second chip area;

the first partition is adjacent to the first chip area;

the third partition is adjacent to the second chip area; and

the second partition is positioned between the first partition and the third partition.