Mask that provides improved focus control using orthogonal edges

摘要

A method includes selecting a mask blank for lithographically forming a desired pattern of main features to be printed onto a wafer by projection lithography. First locations are identified in the desired pattern, the first locations being those which would produce on the wafer images impacted by phase distortions of actinic light through openings in the desired pattern. Second locations in the desired pattern are identified for the insertion of orthoedges. The orthoedges are provided to contribute an additional amplitude of actinic light to the images impacted by phase distortions when the actinic light is projected onto the wafer. The orthoedges are then inserted into the desired pattern at the second locations at orientations such that the orthoedges provide a quadrature component to the additional amplitude of actinic light having an opposite sign to the quadrature component of the actinic light producing the phase distortions. Finally, the mask blank is formed lithographically with the desired pattern modified through the insertion of the orthoedges.

主权项

1. A method comprising:
selecting a mask blank for lithographically forming a desired pattern of main features to be printed onto a wafer by projection lithography; identifying first locations in said desired pattern, said first locations being those which would produce on said wafer images impacted by phase distortions of actinic light through openings in said desired pattern; identifying second locations in said desired pattern for the insertion of orthoedges, said orthoedges being provided to contribute an additional amplitude of actinic light to said images impacted by phase distortions when said actinic light is projected onto said wafer; inserting said orthoedges into said desired pattern at said second locations at orientations such that said orthoedges provide a quadrature component to said additional amplitude of actinic light having an opposite sign to the quadrature component of the actinic light producing said phase distortions; and forming said mask blank lithographically with said desired pattern modified through the insertion of said orthoedges.