Lithography process optimization and system

• US 20070031744A1
• Filed: 06/13/2006
• Published: 02/08/2007
• Est. Priority Date: 08/05/2005
• Status: Active Grant

• Current Assignee: International Business Machines Corporation, Chartered Semiconductor Manufacturing Incorporated (Mamoura Diversified Global Holding PJSC)
• Original Assignee: International Business Machines Corporation, Chartered Semiconductor Manufacturing Incorporated (Mamoura Diversified Global Holding PJSC)
• Inventors: Yudhistira, Yasri, Crouse, Michael
• Granted Patent: US 7,537,870 B2
• Time in Patent Office: Days
• US Class Current: 430/30
• CPC Class Codes: G03F 7/701 Off-axis setting using an aperture
• CPC Class Codes: G03F 7/70191 Optical correction elements, filters or phase plates for controlling intensity, wavelength, polarisation, phase or the like
• CPC Class Codes: G03F 7/70466 Multiple exposures, e.g. combination of fine and coarse exposures, double patterning or multiple exposures for printing a single feature stitching G03F7/70475

Abstract

The first and second example embodiments are Pattern Fidelity Optimization Procedures for a Multiple Exposure Scheme. In the third example embodiment, the aperatures from the multiple exposure system can be combined into a single aperture by adding the apertures and modulating the relative transmission thru the respective apertures to match the prescribed dose split determined in above in the first embodiment.

Claims

1. A method to optimize the optical transfer of a pattern onto photoresist using two or more exposure processes comprising:

providing a photomask design to print a photoresist pattern with at least a first type pattern and a second type pattern;

determining a first exposure process using a first illumination condition that will improve at least a pattern fidelity parameter for the first type pattern;

said first illumination condition comprises a first aperture;

said first illumination condition is determined to improve at least said pattern fidelity parameter for said first type pattern transfer onto said photoresist;

determining a second exposure process using a second illumination condition that will improve at least the pattern fidelity parameter for the second type pattern;

said second illumination condition comprises a second aperture;

said second illumination condition is determined to improve at least said pattern fidelity parameter for said second type pattern transfer onto said photoresist from said photomask design;

then

determining a first exposure dose for the first exposure process and a second exposure dose for the second exposure process that optimize the pattern fidelity parameter for the both the first type pattern and second type pattern type.

2. The method of claim 1 which further comprises:

providing a substrate having a photoresist formed thereover

providing a photomask formed using said photomask design aligned above said substrate;

performing a first exposure through said photomask at the first dose and with said first illuminating condition;

performing a second exposure through said photomask at the second dose and with said second illuminating condition.

3. The method of claim 1 which further includes:

creating a composite aperture design by combining the first aperture and second aperture;

designing a modulating means for modulating the relative transmission through the first aperture and second aperture to allow the first exposure dose through the first aperture of said composite aperture design and to allow the second expose dose through the second aperture of said composite aperture design.

4. The method of claim 1 which further comprises:

creating a composite aperture design by combining the first aperture and second aperture to form a composite aperture design;

designing a modulating means for modulating the relative transmission through the first aperture and second aperture to allow the first exposure dose through the first aperture of said composite aperture design and to allow the second expose dose through the second aperture of said composite aperture design;

forming a exposure tool comprised of (1) the composite aperture formed using said composite aperture design, and (2) a modulation means for modulating the relative transmission through the first aperture and second aperture formed using the design of said modulating means.

5. The method of claim 1 wherein the optimization of the pattern fidelity parameter comprises determining the first and second dose so to maximize the total of the addition of the pattern fidelity parameter for the first type pattern and the pattern fidelity parameter for the second type pattern.

6. The method of claim 1 which further comprises:

making a composite aperture design by combining the first aperture and second apertures to form a composite aperture design;

forming a modulating means design for modulating the relative transmission through the first aperture and second aperture to allow the first exposure dose through the first aperture of said composite aperture design and to allow the second expose dose through the second aperture of said composite aperture design;

forming a composite aperture using said composite aperture design;

forming a modulating means using said modulating means design;

providing a first reticle made using said first reticle design;

providing resist over a substrate; and

exposing said resist using the photomask using the composite aperture and the modulating means.

7. The method of claim 1 wherein:

the first illumination condition comprises;

Numerical Aperture (NA), partial coherence settings, polarization, focus, aperture type; and

aperture area;

the second illumination condition comprises;

Numerical Aperture (NA), partial coherence settings, polarization, focus, aperture type; and

aperture area.

8. The method of claim 1 wherein:

said first type pattern is a nested feature;

said second type pattern comprises an isolated contact; and

said pattern fidelity parameter is resist erosion or bridging.

9. The method of claim 1 wherein:

said first type pattern comprises Line/space features;

said second type pattern comprises contact holes; and

said pattern fidelity parameter is DOF or MEEF.

10. The method of claim 1 wherein:

the pattern fidelity parameters comprise;

depth of focus, critical dimension (CD), mask error enhancement factor (MEEF), amount of line-end pullback, process window, common process window, necking, bridging, resist collapse, dose-to-size E1;

1, dense to isolated feature bias, arbitrary feature size bias, sidelobe printing, film loss, sidewall angle, resolution and combinations thereof;

or weighted combinations thereof or weighted combinations of ranges thereof.

11. The method of claim 1 wherein said first type pattern and said second type pattern are comprised of features;

the features are comprised of lines, line and space arrangements;

contact holes and ellipses of various aspect ratios, long trenches within the resist, L-bar shapes and general 2-D features, and combinations thereof;

the first type pattern and second type pattern are regions of features whose photoresist pattern can be improved by using different illumination conditions.

12. A method to optimize the optical transfer of a pattern onto photoresist using two or more exposure processes comprising:

providing a photomask design to print a photoresist pattern with at least a first type pattern and a second type pattern;

the first type pattern and second type pattern are regions of features whose photoresist patterns can be improved by using different illumination conditions;

determining a first exposure process using a first illumination condition that will improve at least a pattern fidelity parameter for the first type pattern;

said first illumination condition comprises a first aperture;

said first illumination condition is determined to optimize at least a pattern fidelity parameter for said first type pattern transfer onto said photoresist;

determining a second exposure process using a second illumination condition that will improve at least the pattern fidelity parameter for the second type pattern;

said second illumination condition comprises a second aperture;

said first aperture and said second aperture have different configurations;

said second illumination condition is determined to optimize at least said pattern fidelity parameter for said second type pattern transfer onto said photoresist from said photomask design;

then

determining a first exposure dose for the first exposure process and a second exposure dose for the second exposure process that optimize the pattern fidelity parameter for the both the first type pattern and second type pattern type;

said first dose is not is determined to optimize the pattern fidelity parameter for transfer of said type pattern onto said photoresist from the photomask;

said second dose is not determined to optimize the pattern fidelity parameter for transfer of said second type pattern onto said photoresist from the photomask.

13. A photolithography process with two or more exposures, comprising:

providing a wafer having a photoresist formed thereover;

providing a photomask with a first type pattern and a second type pattern formed therein aligned above said wafer;

the first type pattern and the second type pattern are regions whose photoresist patterns can be improved by using different illumination conditions;

performing a first exposure through said photomask at a first dose and with a first illuminating condition;

said first illumination condition is determined to optimize at least a pattern fidelity parameter for said first type pattern transfer onto said photoresist from said photomask;

said first dose is not is determined to optimize at least the pattern fidelity parameter for transfer of said first type pattern onto said photoresist from said photomask;

performing a second exposure through said photomask at a second dose and with a second illuminating condition;

said second illumination condition is determined to optimize said pattern fidelity parameter for said second type pattern transfer onto said photoresist from said photomask;

said second dose is not determined to optimize said pattern fidelity parameter for transfer of said second type pattern onto said photoresist from said photomask; and

the first and second illumination conditions are different;

the first dose and second dose are determined by optimizing at least said pattern fidelity parameter for the combination of the first type pattern and second type pattern transferred onto the photoresist;

developing said photoresist to form a photoresist pattern.

14. The photolithography process of claim 13 wherein:

the first illumination condition comprises Numerical Aperture (NA), partial coherence settings, polarization, focus, aperture type; and

aperture area;

the second illumination condition comprises Numerical Aperture (NA), partial coherence settings, polarization, focus, aperture type; and

aperture area;

said first illumination condition does not include dose;

said second illumination condition does not include dose.

15. The photolithography process of claim 13 wherein said first type pattern has a first a first Rayleigh constant range and said second type pattern has a second Rayleigh constant range;

the first and second Rayleigh constant ranges do not overlap.

16. The photolithography process of claim 13 wherein

a highly nested pattern has a Rayleigh constant (K₁) less than or equal to 0.5;

semi nested pattern type has a Rayleigh constant (K₁) between 0.5 to 0.75;

isolated pattern type has a Rayleigh constant (K₁) greater than or =0.75;

said first type pattern and said second type pattern are one of the highly nested pattern, the semi nested or isolated type pattern;

said first type pattern and said second type pattern type are different pattern types.

17. The photolithography process of claim 13 wherein the first and second illumination conditions use different aperture types.

18. The photolithography process of claim 13 wherein:

the first type pattern and the second type patterns have different;

feature shapes, feature orientations, or Rayleigh constant ranges.

19. The photolithographic process of claim 13 which further includes said pattern fidelity metric is a merit function that is comprised of process fidelity parameters.

20. A method to make a composite aperture design for an optical transfer of a pattern onto photoresist using one exposure process comprising:

providing a photomask design to print a photoresist pattern with at least a first type pattern and a second type pattern;

determining a first exposure process using a first illumination condition that will improve at a pattern fidelity parameter for the first type pattern;

said first illumination condition comprises a first aperture;

said first illumination condition is determined to optimize at least a pattern fidelity parameter for said first type pattern transfer onto said photoresist;

determining a second exposure process using a second illumination condition that will improve at least the pattern fidelity parameter for the second type pattern;

said second illumination condition comprises a second aperture;

said first aperture and said second aperture have different configurations;

said second illumination condition is determined to optimize at least said pattern fidelity parameter for said second type pattern transfer onto said photoresist from said photomask design;

then

determining a first exposure dose for the first exposure process and a second exposure dose for the second exposure process that optimize the pattern fidelity parameter for the both the first type pattern and second type pattern type;

making a composite aperture design by combining the first aperture and second apertures to form a composite aperture design;

designing a modulating means for modulating the relative transmission through the first aperture and second aperture to allow the first exposure dose and second exposure dose through the first and second apertures of the composite aperture design.

21. The method of claim 20 which further comprises:

forming a exposure tool comprised of (1) a composite aperture formed using said composite aperture design, and (2) a modulation means for modulating the relative transmission through the first aperture and second aperture formed using the design of said modulating means.

22. The method of claim 20 which further comprises:

forming a composite aperture using said composite aperture design;

providing a first reticle made using said first reticle design;

providing resist over a substrate; and

exposing said resist using the photomask using the composite aperture and the modulating means.

23. The method of claim 20 wherein:

the first illumination conditions comprise

Numerical Aperture (NA), partial coherence settings, polarization, focus, aperture type; and

aperture area;

the second illumination condition comprises Numerical Aperture (NA), partial coherence settings, polarization, focus, aperture type; and

aperture area.

24. The method of claim 20 wherein:

said first type pattern is a nested feature;

said second type pattern comprises an isolated contact; and

said pattern fidelity parameter is resist erosion or bridging.

25. The method of claim 20 wherein:

said first type pattern comprises Line/space features;

said second type pattern comprises contact holes; and

said pattern fidelity parameter is DOF or MEEF.

26. The method of claim 20 wherein:

the pattern fidelity parameters comprise;

depth of focus, critical dimension (CD), mask error enhancement factor (MEEF), amount of line-end pullback, process window, common process window, necking, bridging, resist collapse, dose-to-size E1;

1, dense to isolated feature bias, arbitrary feature size bias, sidelobe printing, film loss, sidewall angle, resolution and combinations thereof;

or weighted combinations thereof or weighted combinations of ranges thereof.