Methods and systems for lithography process window simulation

• US 9,390,206 B2
• Filed: 08/29/2013
• Issued: 07/12/2016
• Est. Priority Date: 12/05/2007
• Status: Active Grant

• Current Assignee: ASML Netherlands BV (ASML Holding NV)
• Original Assignee: ASML Netherlands BV (ASML Holding NV)
• Inventors: Ye, Jun, Cao, Yu, Feng, Hanying
• Primary Examiner(s): Thangavelu, Kandasamy
• Application Number:
  US14/013,593
• Publication Number:
  US 20140005998A1
• Time in Patent Office: 1,048 Days
• US Class Current: 1/1
• 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 7/70991 Connection with other apparatus, e.g. multiple exposure stations, particular arrangement of exposure apparatus and pre-exposure and/or post-exposure apparatus; Shared apparatus, e.g. having shared radiation source, shared mask or workpiece stage, shared base-plate; Utilities, e.g. cable, pipe or wireless arrangements for data, power, fluids or vacuum
• CPC Class Codes: G06F 30/20 Design optimisation, verification or simulation optimisation, verification or simulation of circuit designs G06F30/30

Abstract

A method of efficient simulating imaging performance of a lithographic process utilized to image a target design having a plurality of features. The method includes the steps of determining a function for generating a simulated image, where the function accounts for process variations associated with the lithographic process; and generating the simulated image utilizing the function, where the simulated image represents the imaging result of the target design for the lithographic process.

Claims

1. A method comprising:

identifying a model of a lithographic process;

identifying a nominal condition of the lithographic process;

identifying a process parameter to vary from the nominal condition;

generating, using a computer and the model, two or more terms for a polynomial series expansion about the nominal condition as a function of the process parameter; and

generating, using the computer, a simulated image at a specific value of the process parameter utilizing the generated terms.

2. The method according to claim 1, wherein the polynomial series expansion comprises an aerial image at the nominal condition and two or more higher-order approximations of the aerial image at variations of the process parameter, the approximations respectively corresponding to the two or more terms.

3. The method according to claim 1, wherein the polynomial series expansion comprises a nominal set of model values at the nominal condition and two or more higher-order approximations of the set of model values at variations of the process parameter, the approximations respectively corresponding to the two or more terms.

4. The method according to claim 3, wherein the set of model values comprise transmission cross-coefficients (TCCs).

5. The method according to claim 1, wherein the process parameter comprises at least one of focus and exposure dose.

6. The method according to claim 1, wherein the process parameter comprises at least one of numerical aperture and sigma.

7. The method according to claim 1, wherein the step of using the model to generate the terms includes performing a best fit of a series of aerial images that are produced at different process window variations using the model.

8. The method according to claim 1, further comprising extracting critical dimensions from the simulated image to determine if there is sufficient process window coverage at the specific value of the process parameter.

9. The method according to claim 1, further comprising:

identifying a target pattern, the target pattern having a plurality of features to be imaged in a layer of a semiconductor device using the lithographic process,

wherein using the model to generate the terms includes using the model and the target pattern to generate a series of simulated aerial images associated with different values of the process parameter.

10. The method according to claim 1, wherein the simulated image is one of an aerial image and a resist image.

11. A non-transitory computer readable storage medium having instructions stored thereon which, when executed by a computer, cause the computer to perform a method comprising:

identifying a model of a lithographic process;

identifying a nominal condition of the lithographic process;

identifying a process parameter to vary from the nominal condition;

generating, using the computer and the model, two or more terms for a polynomial series expansion about the nominal condition as a function of the process parameter; and

generating, using the computer, a simulated image at a specific value of the process parameter utilizing the generated terms.

12. The method according to claim 11, wherein the polynomial series expansion comprises an aerial image at the nominal condition and two or more higher-order approximations of the aerial image at variations of the process parameter, the approximations respectively corresponding to the two or more terms.

13. The method according to claim 11, wherein the polynomial series expansion comprises a nominal set of model values at the nominal condition and two or more higher-order approximations of the set of model values at variations of the process parameter, the approximations respectively corresponding to the two or more terms.

14. The method according to claim 13, wherein the set of model values comprise transmission cross-coefficients (TCCs).

15. The method according to claim 11, wherein the process parameter comprises at least one of focus and exposure dose.

16. The method according to claim 11, wherein the process parameter comprises at least one of numerical aperture and sigma.

17. The method according to claim 11, wherein the step of using the model to generate the terms includes performing a best fit of a series of aerial images that are produced at different process window variations using the model.

18. The method according to claim 11, further comprising extracting critical dimensions from the simulated image to determine if there is sufficient process window coverage at the specific value of the process parameter.

19. The method according to claim 11, further comprising:

identifying a target pattern, the target pattern having a plurality of features to be imaged in a layer of a semiconductor device using the lithographic process,

wherein using the model to generate the terms includes using the model and the target pattern to generate a series of simulated aerial images associated with different values of the process parameter.

20. The method according to claim 11, wherein the simulated image is one of an aerial image and a resist image.