METHOD OF CALCULATING DEFLECTION ABERRATION CORRECTING VOLTAGE AND CHARGED PARTICLE BEAM WRITING METHOD

Abstract

A method of calculating a deflection aberration correcting voltage includes writing predetermined patterns at a plurality of focus height positions measuring dimensional variations of width sizes of the predetermined patterns written at the plurality of focus height positions, calculating effective resolutions of the written predetermined patterns by using the dimensional variations, and on the basis of a focus height position at which a minimum effective resolution of the predetermined patterns is obtained, calculating a correcting voltage to correct deflection aberration and output the correcting voltage, wherein the correcting voltage is used when a charged particle beam is deflected.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow chart showing main steps of an electron beam writing method according to a first embodiment;

FIG. 2 is a conceptual diagram showing a configuration of a writing apparatus according to the first embodiment;

FIG. 3 is a diagram showing an example of an evaluating pattern according to the first embodiment;

FIG. 4 is a graph showing a relationship between a dimensional variation and a dose;

FIG. 5 is a diagram showing an example of a pattern profile in a Threshold model;

FIG. 6 is a diagram showing an example of a table showing some parameters and an effective resolution in the first embodiment;

FIG. 7 is a diagram for explaining a way of applying a voltage to a deflector when a uniform electric field is obtained;

FIG. 8 is a diagram for explaining a way of applying a voltage to a deflector when a quadrapole lens field is obtained;

FIGS. 9A and 9B are diagrams showing focal positions at deflection centers;

FIGS. 10A and 10B are diagram showing focal positions in deflection states;

FIG. 11 is a diagram showing a focal position at a deflection center;

FIG. 12 is a diagram showing a focal position in a deflection state;

FIG. 13 is a map of a focus height position z (σ_xmin) of a minimum effective resolution σ_xmin in an x direction and a focus height position z (σ_ymin) of an effective resolution σ_ymin in a y direction at each coordinate position in the first embodiment;

FIG. 14 is a diagram showing a map of a sum of the focus height position z (σ_xmin) and the focus height position z (σ_ymin) at each coordinate position in the first embodiment;

FIG. 15 is a diagram showing a map of a difference between the focus height position z (σ_xmin) and the focus height position z (σ_ymin) at each coordinate position in the first embodiment;

FIG. 16 is an expression for explaining a method of calculating a correction voltage for correcting field curvature in the first embodiment;

FIG. 17 is an expression for explaining a method of calculating a correction voltage for correcting astigmatism in the first embodiment;

FIG. 18 is a diagram showing an example of a pattern profile in a Threshold model written at an optimum correction voltage in the first embodiment;

FIG. 19 is a graph showing a relationship between a dimensional variation and a focus height position;

FIG. 20 is a conceptual diagram showing a configuration of a deflector according to a second embodiment;

FIG. 21 is a diagram showing an example of an evaluating pattern in the second embodiment;

FIG. 22 is a diagram showing an example of a shaping aperture; and

FIG. 23 is a conceptual diagram for explaining an operation of a conventional variable-shaped electron beam photolithography apparatus.

Claims

1. A method of calculating a deflection aberration correcting voltage, comprising: writing predetermined patterns at a plurality of focus height positions;measuring dimensional variations of width sizes of the predetermined patterns written at the plurality of focus height positions;calculating effective resolutions of the written predetermined patterns by using the dimensional variations; andon the basis of a focus height position at which a minimum effective resolution of the predetermined patterns is obtained, calculating a correcting voltage to correct deflection aberration and output the correcting voltage, wherein the correcting voltage is used when a charged particle beam is deflected.

2. The method of calculating a deflection aberration correcting voltage according to claim 1, wherein patterns having widths in an x direction and a y direction are used as the predetermined patterns.

3. The method of calculating a deflection aberration correcting voltage according to claim 2, wherein directions at 0° and 90° are used as the x direction and the y direction.

4. The method of calculating a deflection aberration correcting voltage according to claim 2, wherein directions at 45° and 135° are used as the x direction and the y direction.

5. The method of calculating a deflection aberration correcting voltage according to claim 2, wherein in calculation of the effective resolutions, the effective resolutions in the x direction and the y direction are calculated.

6. The method of calculating deflection aberration correcting voltage according to claim 5, wherein effective resolutions in directions at 0° and 90° are calculated.

7. The method of calculating a deflection aberration correcting voltage according to claim 5, wherein effective resolutions in directions at 45° and 135° are calculated.

8. The method of calculating a deflection aberration correcting voltage according to claim 5, wherein in calculation of the correcting voltage, correcting voltages to correct field curvature and astigmatism aberration as the deflection aberration are calculated.

9. The method of calculating a deflection aberration correcting voltage according to claim 1, wherein as the predetermined patterns, a first pattern having widths in the directions at 0° and 90° and a second pattern having widths in directions at 45° and 135° are used.

10. The method of calculating a deflection aberration correcting voltage according to claim 9, wherein in calculation of the effective resolution, effective resolutions in the directions at 0° and 90° and effective resolutions in the directions at 45° and 135° are calculated.

11. The method of calculating a deflection aberration correcting voltage according to claim 10, wherein in calculation of the correcting voltage, correcting voltages to correct field curvature and astigmatism aberration in the directions at 0° and 90° as the deflection aberration and correcting voltages to correct field curvature and astigmatism aberration in the directions at 45° and 135° as the deflection aberration are calculated.

12. A charged particle beam writing method comprising: writing predetermined patterns at a plurality of focus height positions;on the basis of a focus height position at which a minimum effective resolution of the written predetermined patterns is obtained, calculating a correcting voltage to correct deflection aberration when a charged particle beam is deflected; andby using the correcting voltage, deflecting the charged particle beam to write a desired pattern on a target object.

13. The charged particle beam writing method according to claim 12, wherein when calculation of the correcting voltage, correcting voltages to correct deflection aberration in directions at 45° and 135° are calculated, and the charged particle beam variably shaped in a beam shape having an angle of 45° by an aperture is deflected.

14. The method of calculating a deflection aberration correcting voltage according to claim 1, further comprising: acquiring an iso focal dose by using a plurality of focus height positions and a plurality of doses;wherein the predetermined patterns write at a exposure dose of the charged particle beam instead of the iso focal dose.