Measurement method for linewidth metrology

A method of determining the edge of an object by microscopy comprising the steps of:

• a) providing an object whose edge is to be detected on a background which contrasts with the object;
• b) providing a microscopy system having image signal profile capabilities selected from the group consisting of optical microscopy systems and scanning electron microscopy systems;
• c) viewing the edge of said object with said microscopy system at a first focus value;
• d) measuring the image signal profile of the object edge at said first focus value;
• e) viewing said object edge with said microscopy system at a second focus value different from said first focus value;
• f) measuring the image signal profile of said object edge at said second focus value;
• and
• g) determining the location of said object edge by comparing said image signal profiles of said object edge at said first and second focus values and determining an isofocal point of said profiles.

A method of determining the edge of an object by microscopy comprising the steps of:

• a) providing an object whose edge is to be detected on a background which contrasts with the object;
• b) providing a microscopy system having image signal profile capabilities;
• c) viewing the edge of said object with said microscopy system at a first focus value;
• d) measuring the image signal profile of the object edge at said first focus value;
• e) viewing said object edge with said microscopy system at a second focus value different from said first focus value;
• f) measuring the image signal profile of said object edge at said second focus value;
• g) viewing said object edge with said microscopy system at a third focus value different from said first and second focus values;
• h) measuring the image signal profile of said object edge at said third focus value;
• and
• i) determining the location of said object edge by comparing said image signal profiles of said object edge at said first, second and third focus values.