Method for improving design window

A method of forming a photo mask used in integrated circuit fabrication processes, the method comprising:

• determining a minimum spacing;
• identifying patterns having a spacing less than the minimum spacing, wherein the patterns are for forming vertical conductive features;
• for each identified pattern, determining a first direction to expand and a second direction to shrink to define a revised pattern;
• checking against design rules to see if the design rules are violated if the respective identified pattern is expanded in the first direction and shrunk in the second direction;
• replacing each identified pattern with the respective revised pattern when the design rules are not violated, wherein the revised pattern is expanded in the first direction and shrunk in the second direction;
• and
• forming a photo mask using the revised pattern.

A semiconductor integrated circuit structure comprising:

• a semiconductor substrate;
• a plurality of interconnection lines and dielectric layers over the substrate;
• and
• a first via and a second via having a spacing in the dielectric layers, wherein at least one of the first and the second vias has a length and a width substantially smaller than the length.