Source optimization for image fidelity and throughput

• US 20080174756A1
• Filed: 06/28/2007
• Published: 07/24/2008
• Est. Priority Date: 02/03/2004
• Status: Active Grant

• Current Assignee: Siemens Industry Software Inc. (Siemens AG)
• Original Assignee: Mentor Graphics Corporation (Siemens AG)
• Inventors: Granik, Yuri
• Granted Patent: US 7,623,220 B2
• Time in Patent Office: Days
• US Class Current: 355/67
• CPC Class Codes: G03F 7/70108 Off-axis setting using a light-guiding element, e.g. diffractive optical elements [DOEs] or light guides
• CPC Class Codes: G03F 7/70441 Optical proximity correction [OPC]
• CPC Class Codes: G03F 7/70491 Information management, e.g. software; Active and passive control, e.g. details of controlling exposure processes or exposure tool monitoring processes
• CPC Class Codes: G03F 7/705 Modelling or simulating from physical phenomena up to complete wafer processes or whole workflow in wafer productions

Abstract

A system and method for optimizing an illumination source to print a desired pattern of features dividing a light source into pixels and determining an optimum intensity for each pixel such that when the pixels are simultaneously illuminated, the error in a printed pattern of features is minimized. In one embodiment, pixel solutions are constrained from solutions that are bright, continuous, and smooth. In another embodiment, the light source optimization and resolution enhancement technique(s) are iteratively performed to minimize errors in a printed pattern of features.

Claims

1. A method of optimizing a light source to create a desired pattern of features on a wafer with a photolithographic process, comprising:

receiving at least a portion of a layout database and selecting a desired pattern of features to be created on a wafer;

relating a number of pixel intensities in a light source and the contribution of the pixels in the light source to a point on the wafer to the desired pattern of features using a mathematical relationship; and

determining the pixel intensities of the light source using the mathematical relationship such that upon simultaneous illumination of the pixels at their determined pixel intensities, the errors between a pattern of features that will be created on the wafer and the desired pattern of features are minimized.

2. The method of claim 1, wherein one or more constraints are placed on the mathematical relationship.

3. The method of claim 2, wherein the one or more constraints include limiting the optical power of the combined pixel intensities.

4. The method of claim 2, wherein the one or more constraints include limiting the pixel intensities such that each pixel having a non-zero intensity is adjacent another pixel having a non-zero intensity.

5. The method of claim 2, wherein the one or more constraints include limiting the pixel intensities such that the intensities of adjacent pixels do not vary by more than a predefined amount.

6. The method of claim 1, wherein the desired pattern of features is selected by determining a pattern of features that occurs at two or more locations on the wafer and the intensities of the pixels in the light source is determined by optimizing the light source pixel intensities to produce a minimum error in the selected pattern of features and the features that will be created on a wafer.

7. The method of claim 1, wherein the desired pattern of features is selected by determining a pattern of features that is repeated.

8. The method of claim 1, wherein the desired pattern of features is selected by determining a pattern of features that occurs in an array.

9. The method of claim 1, further comprising selecting areas of the desired pattern of features and weighting the selected areas in the mathematical relationship such that the errors at the selected areas are minimized.

10. The method of claim 1, in which the mathematical relationship is a matrix equation.

11. The method of claim 1, further comprising creating an optical element that simultaneously produces the pixels having the determined light source intensities when illuminated by a light source of a photolithographic system.

12. The method of claim 11, wherein the optical element is a diffractive optical element.

13. A computer readable medium containing a number of instructions that are executable by a computer to perform the method of claim 1.

14. A diffractive optical element that produces a distribution of illumination light for a photolithographic process that is produced in accordance with the method of claim 1.

15. A method of preparing a file that defines a desired pattern of features to be created by a photolithographic process, comprising:

receiving all or a portion of a layout database from which a target pattern of features to be created via a photolithographic process is created;

correcting the features of the layout database with a resolution enhancement technique such that an error between a pattern of features that will be printed on a wafer and the target pattern of features is minimized;

using the corrected features to optimize a distribution of light from an illumination light source such that when the corrected features are illuminated by the light source, the error between the pattern of features that will be created on a wafer and the target pattern of features is minimized.

16. The method of claim 15, further comprising:

further correcting the features with a resolution enhancement technique assuming illumination with an optimized distribution of light; and

further optimizing the distribution of light using the further corrected features so that the error between the pattern of features that will be created on a wafer and the target pattern of features is minimized.

17. A computer readable medium containing a number of instructions that are executable by a computer to perform the method of claim 15.

18. A diffractive optical element that produces a distribution of illumination light for a photolithographic process that is produced in accordance with the method of claim 15.

19. A method of preparing a file that defines a desired pattern of features to be created by a photolithographic process, comprising:

receiving all or a portion of a layout database from which a target pattern of features to be created via a photolithographic process is created;

optimizing a distribution of light from an illumination light source such that when features are illuminated by the illumination light source, the error between a pattern of features that will be created on a wafer and the target pattern of features is minimized; and

correcting the features of the layout database with a resolution enhancement technique assuming illumination with the optimized distribution of light from the illumination light source such that an error between a pattern of features that will be printed on a wafer and the target pattern of features is minimized.

20. The method of claim 19, further comprising:

further optimizing the distribution of light using the corrected features so that the error between the pattern of features that will be created on a wafer and the target pattern of features is minimized; and

further correcting the corrected features with a resolution enhancement technique assuming illumination with the further optimized distribution of light.

21. A computer readable medium containing a number of instructions that are executable by a computer to perform the method of claim 19.

22. A diffractive optical element that produces a distribution of illumination light for a photolithographic process that is produced in accordance with the method of claim 19.