Method and System for Design of Enhanced Edge Slope Patterns for Charged Particle Beam Lithography

Abstract

A method and system for fracturing or mask data preparation are presented in which overlapping shots are generated to increase dosage in selected portions of a pattern, thus improving the fidelity and/or the critical dimension variation of the transferred pattern. In various embodiments, the improvements may affect the ends of paths or lines, or square or nearly-square patterns. Simulation is used to determine the pattern that will be produced on the surface.

1 . A method for fracturing or mask data preparation or proximity effect correction comprising:
 calculating a line end pattern that will be produced on a surface and calculating the edge slope of the pattern from a set of shots comprising one or more shots; and   modifying the set of shots to improve the edge slope of the calculated line end pattern, wherein the modification comprises at least one of the group consisting of 1) determining an additional shot which overlaps a shot in the set of shots; 2) varying the overlap of two or more shots in the set of shots; 3) varying the size of a shot which overlaps another shot; and 4) varying the dosage of a shot in the set of shots with respect to the dosage of another overlapping shot in the set of shots.   
     
     
         2 . The method of  claim 1  wherein the step of calculating comprises charged particle beam simulation. 
     
     
         3 . The method of  claim 2  wherein the charged particle beam simulation includes at least one of a group consisting of forward scattering, backward scattering, resist diffusion, Coulomb effect, etching, fogging, loading and resist charging. 
     
     
         4 . The method of  claim 1  wherein the modified set of shots includes a character projection shot of a complex character. 
     
     
         5 . The method of  claim 1  wherein the modified set of shots increases the peak dosage near the line end. 
     
     
         6 . A method for fracturing or mask data preparation or proximity effect correction comprising:
 determining a plurality of shots which form a line end pattern on a surface, wherein the step of determining comprises calculating the pattern on the surface and calculating the edge slope of the pattern from the plurality of shots, and wherein the edge slope of the line end pattern on the surface is improved using a shot varying technique comprising at least one of the group consisting of 1) varying the dosage of a shot overlapping another shot; 2) varying the overlap of two or more shots; and 3) varying the size of a shot which overlaps another shot.   
     
     
         7 . The method of  claim 6  wherein the step of determining comprises determining shots for multiple exposure passes, and wherein overlapping shots are placed in different exposure passes. 
     
     
         8 . The method of  claim 6  wherein a complex character shot is determined. 
     
     
         9 . The method of  claim 6  wherein an optimization technique is used to determine the plurality of shots. 
     
     
         10 . The method of  claim 6  wherein the calculating comprises charged particle beam simulation. 
     
     
         11 . The method of  claim 6 , further comprising inputting a library of precalculated glyphs, wherein the step of determining determines shots from one or more glyphs, and wherein the glyph precalculation constitutes at least a part of the pattern calculation. 
     
     
         12 . A method for fracturing or mask data preparation or proximity effect correction comprising:
 determining a plurality of shots which form a square or nearly-square pattern on a surface, wherein the step of determining comprises calculating the pattern on the surface and calculating the edge slope of the pattern from the plurality of shots, and wherein the edge slope of the square pattern on the surface is improved using a shot varying technique comprising at least one of the group consisting of 1) varying the dosage of a shot overlapping another shot; 2) varying the overlap of two or more shots; and 3) varying the size of a shot which overlaps another shot.   
     
     
         13 . The method of  claim 12  wherein the step of calculating comprises charged particle beam simulation. 
     
     
         14 . The method of  claim 12  wherein the plurality of shots produces a higher peak dosage near the corners of the pattern than in the center of the pattern. 
     
     
         15 .- 25 . (canceled)