Measurement tool and method for lithography masks

A method for mask measurements comprising:

• providing a EUV light source with a focal field;
• providing a detector assembly;
• providing a patterned mask on a stage;
• moving the stage to align the focal field with specific coordinates for a test site selected from a plurality of predetermined test sites;
• determining a best focus plane for the test site from a scan taken as the stage moves, wherein the scan provides a continuous image output from the test site;
• moving the stage to a stationary position at the best focus plane;
• and
• obtaining an actinic critical dimension measurement at the test site by capturing a static image.

An inspection method comprising:

• providing a patterned mask on a movable stage, the patterned mask comprising a plurality of predetermined test sites and pre-selected calibration sites;
• generating best focus planes for the pre-selected calibration sites using a step and repeat scanning process;
• generating a site specific best focus plane for each of the plurality of predetermined test sites using a continuous scanning process that provides a continuous image output from the predetermined test site;
• and
• obtaining actinic critical dimension measurements at each of the plurality of predetermined test sites by capturing a static image using the site specific best focus plane for each of the plurality of predetermined test sites.