Photomask pattern

A photomask pattern formed on a substrate, comprising:

• a plurality of main patterns;
• at least a first sub-resolution assistant feature located between main patterns with each first sub-resolution assistant feature having an odd number of assistant features, wherein the phase difference between the odd-numbered assistant features and the main pattern is 180°, and the phase difference between the even-numbered assistant features and the main pattern is 0°;
• and
• a plurality of second sub-resolution assistant feature located on the outer edges of the main patterns, wherein each second resolution assistant feature furthermore comprises:
• a first assistant feature close to the main pattern, wherein the phase difference between the first assistant feature and the main pattern is 180°;
• and
• a second assistant feature further away from the main pattern but adjacent to the first assistant feature, wherein the phase difference between the second assistant feature and the first assistant feature is 180°.

A photomask pattern formed on a substrate, comprising:

• a plurality of main patterns;
• a first sub-resolution assistant feature located between main patterns, wherein the first sub-resolution assistant feature has an odd number of assistant features comprising at least two first assistant features and at least one second assistant feature, the second assistant feature and the first assistant features are alternately arranged with that each of the main patterns is directly adjacent to one of the first assistant feature, and the phase difference between the first assistant features and the main patterns is 180°, and the phase difference between the second assistant features and the main pattern is 0°;
• and
• a plurality of second sub-resolution assistant feature located on the outer edges of the whole of the main patterns, wherein each second resolution assistant feature furthermore comprises:
• a third assistant feature located directly close to the main pattern, wherein the phase difference between the third assistant feature and the main pattern is 180°;
• and
• a fourth assistant feature further away from the main pattern but directly adjacent to the third assistant feature, wherein the phase difference between the fourth assistant feature and the third assistant feature is 180°.