Methods and systems for lithography process window simulation

• US 8,527,255 B2
• Filed: 06/12/2012
• Issued: 09/03/2013
• 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:
  US13/494,773
• Publication Number:
  US 20120253774A1
• Time in Patent Office: 448 Days
• Field of Search: 703/13, 716/4, 716/5, 716/19, 716/20, 716/54, 716/52, 355/67, 430/22, 382/144
• US Class Current: 703/13
• 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 implemented by a computer comprising:

identifying a model of a lithographic process;

using, by the computer, the model to generate a function that simulates an image produced by the lithographic process, the function having one or more variables representing process window variations from a nominal process condition associated with the lithographic process;

generating, using the computer, a plurality of simulated images utilizing the generated function, the plurality of simulated images respectively corresponding to a plurality of different lithographic process conditions that are variations from the nominal process condition; and

analyzing the plurality of simulated images to determine a process window associated with the lithographic process.

2. The method according to claim 1, wherein the process window variations include variations in at least one of focus and exposure dose.

3. The method according to claim 2, wherein the process window variations further include variations in optical settings including at least one of numerical aperture and sigma.

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

5. The method according to claim 1, wherein analyzing includes extracting critical dimensions from the plurality of simulated images.

6. The method according to claim 1, wherein analyzing includes extracting feature edge placement errors from the plurality of simulated images.

7. 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 function includes using the model and the target pattern to generate a series of simulated aerial images associated with different process window variations.

8. The method according to claim 7, wherein the step of using the model to generate the function further includes performing a best fit on the series of aerial images.

9. The method according to claim 1, wherein the simulated images comprise resist images.

10. A method implemented by a computer comprising:

identifying a model of a lithographic process;

identifying a set of optical conditions associated with the lithographic process;

pre-computing, by the computer, a set of transmission coefficients associated with the model and the identified set of optical conditions;

using, by the computer, the set of transmission coefficients to generate a function that simulates an image produced by the lithographic process, the function having one or more variables representing process window variations from a nominal process condition associated with the lithographic process;

generating, using the computer, a plurality of simulated images utilizing the generated function, the plurality of simulated images respectively corresponding to a plurality of different lithographic process conditions that are variations from the nominal process condition; and

analyzing the plurality of simulated images to determine a process window associated with the lithographic process.

11. The method according to claim 10, wherein the process window variations include variations in at least one of focus and exposure dose.

12. The method according to claim 11, wherein the process window variations further include variations in optical settings including at least one of numerical aperture and sigma.

13. The method according to claim 10, wherein the step of using the set of transmission coefficients to generate the function includes performing a best fit of a series of aerial images that are produced at different process window variations using the set of transmission coefficients.

14. The method according to claim 10, wherein analyzing includes extracting critical dimensions from the plurality of simulated images.

15. The method according to claim 10, wherein analyzing includes extracting feature edge placement errors from the plurality of simulated images.

16. The method according to claim 10, 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 set of transmission coefficients to generate the function includes convolving the set of transmission coefficients with the target pattern to generate a series of simulated aerial images associated with different process window variations.

17. The method according to claim 16, wherein the step of using the model to generate the function further includes performing a best fit on the series of aerial images.

18. The method according to claim 10, wherein the simulated images comprise resist images.