Optimized polarization illumination

• US 20050134822A1
• Filed: 08/20/2004
• Published: 06/23/2005
• Est. Priority Date: 12/19/2003
• Status: Active Grant

• Current Assignee: ASML Netherlands BV (ASML Holding NV)
• Original Assignee: ASML Masktools B.V. (ASML Holding NV)
• Inventors: Hansen, Steve, Socha, Robert, Flagello, Donis
• Granted Patent: US 7,292,315 B2
• Time in Patent Office: Days
• US Class Current: 355/69
• CPC Class Codes: G03F 7/70125 Use of illumination settings tailored to particular mask patterns details of setting means G03F7/70091
• CPC Class Codes: G03F 7/70341 Details of immersion lithography aspects, e.g. exposure media or control of immersion liquid supply chemical composition of immersion liquids G03F7/2041
• CPC Class Codes: G03F 7/705 Modelling or simulating from physical phenomena up to complete wafer processes or whole workflow in wafer productions
• CPC Class Codes: G03F 7/70566 Polarisation control
• CPC Class Codes: G03F 7/70616 Monitoring the printed patterns

Abstract

Disclosed concepts include a method of optimizing polarization of an illumination of a pattern to be formed in a surface of a substrate. Polarized illumination is optimized by determining an illumination intensity for at least one point on an illuminator for at least two polarization states, determining image log slope for the at least one point on the illuminator for the at least two polarization states, determining a maximum image log slope (ILS) where the ILS is near zero for the at least one point on the illuminator, and selecting an optimal polarization state corresponding to the at least two polarization states that minimizes an ILS for the at least one point on the illuminator. This may be repeated for a plurality of points on the illuminator.

Claims

1. A method of optimizing polarization of an illumination of a pattern to be formed in a surface of a substrate, comprising the steps of:

(a) determining an illumination intensity for at least one point on an illuminator for at least two polarization states;

(b) determining image log slope for the at least one point on the illuminator for the at least two polarization states;

(c) determining a maximum image log slope (ILS) where the ILS is at least near zero for the at least one point on the illuminator; and

(d) selecting an optimal polarization state corresponding for the maximum ILS for the at least one point on the illuminator.

2. The method of optimizing polarization of the illumination according to claim 1, further comprising repeating steps (a)-(d) for each of a plurality of points on the illuminator.

3. The method of optimizing polarization of the illumination according to claim 1, further comprising repeating steps (a)-(d) for each of a plurality of points on part of the illuminator relative to symmetry of a feature.

4. The method of optimizing polarization of the illuminator according to claim 1, further comprising repeating steps (a)-(d) for each of a plurality of points on half of the illuminator.

5. The method of optimizing polarization of an illuminator according to claim 2, further comprising the step of combining the optimal polarization state for each of the plurality of points on the illuminator for creating an optimal illumination of the pattern.

6. The method of optimizing polarization of an illuminator according to claim 1, wherein the optimal polarization state is a variant of the at least two polarization states.

7. The method of optimizing polarization of an illuminator according to claim 1, wherein the optimal polarization state corresponds to one of the at least two polarization states.

8. The method of optimizing polarization of an illuminator according to claim 1, wherein the at least two polarization states includes at least X and Y polarization states.

9. A computer program product, comprising executable code transportable by at least one machine readable medium, wherein execution of the code by at least one programmable computer causes the at least one programmable computer to perform a sequence of steps for optimizing polarized illumination for a pattern to be formed in a surface of a substrate, comprising:

(a) calculating an illumination intensity for at least one point on an illuminator for at least two polarization states;

(b) calculating an image log slope for the at least one point on the illuminator for the at least two polarization states;

(c) determining a maximum image log slope (ILS) where the slope of the ILS is at least near zero for the at least one point on the illuminator; and

(d) selecting an optimal polarization state for the maximum ILS for the at least one point on the illuminator.

10. The computer program product according to claim 9, further comprising the steps of repeating steps (a)-(d) for each of a plurality of points on the illuminator.

11. The computer program product according to claim 9 further comprising repeating steps (a)-(d) for each of a plurality of points on part of an illuminator relative to symmetry of a feature.

12. The computer program product according to claim 9 further comprising repeating steps (a)-(d) for each of a plurality of points on half of the illuminator.

13. The computer program product according to claim 10, further comprising the step of combining the optimal polarization state for each of the plurality of points on the illuminator for creating an optimal illumination of the pattern.

14. The computer program product according to claim 9, wherein the optimal polarization state is a variant of the at least two polarization states.

15. The computer program product according to claim 9, wherein the optimal polarization state corresponds to one of the at least two polarization states.

16. The method of optimizing polarization of an illuminator according to claim 9, wherein the at least two polarization states includes at least X and Y polarization states.

17. An apparatus for generating a mask design using optimized polarized illumination for increasing process window, said apparatus comprising:

a radiation system for supplying a projection beam of polarized radiation;

an illuminator for receiving the projection beam of radiation and projecting an adjusted beam of radiation a portion of a mask, and

a projection system for imaging a corresponding irradiated portion of a mask, onto a target portion of a substrate,

wherein

the illuminator is adjusted at a plurality of points to optimize polarization and intensity at each of the plurality of points.

18. The apparatus according to claim 17, further comprising:

a computer system configured to optimize polarization and intensity at each of the plurality of points by performing the steps of;

(a) determining an illumination intensity for at least one point on an illuminator for at least two polarization states;

(b) determining image log slope for the at least one point on the illuminator for the at least two polarization states;

(c) determining a maximum image log slope (ILS) where the ILS is at least near zero for the at least one point on the illuminator;

(d) selecting an optimal polarization state corresponding to the maximum ILS for the at least one point on the illuminator; and

(e) repeating steps (a)-(d) for each of the plurality of points on the illuminator.