Linearity improvement for photomask critical dimension metrology with deep-ultraviolet microscope

摘要

Linearity improvement by the simulation assist (SA) method for photomask critical dimension (CD) measurement with a deep-ultraviolet (UV) microscope is proposed. With the conventional method, if a measurement pattern on a photomask is insufficiently resolved by the microscope, the CD cannot maintain linearity to the actual pattern size. With the SA method, the lack of the resolution is canceled by an actual image and a simulated image, so that the CD can maintain linearity to the actual pattern size. The results of experiments demonstrate that the SA method improves CD linearity of the conventional method with a deep-UV microscope.