Methods and systems for parameter-sensitive and orthogonal gauge design for lithography calibration

• US 10,025,885 B2
• Filed: 01/05/2015
• Issued: 07/17/2018
• Est. Priority Date: 11/10/2008
• 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, Shao, Wenjin
• Primary Examiner(s): Craig, Dwin M
• Application Number:
  US14/589,738
• Publication Number:
  US 20150186557A1
• Time in Patent Office: 1,289 Days
• Field of Search: 703 6
• CPC Class Codes: G03F 1/44 Testing or measuring features, e.g. grid patterns, focus monitors, sawtooth scales or notched scales
• CPC Class Codes: G03F 1/62 Pellicles, e.g. pellicle assemblies, e.g. having membrane on support frame; Preparation thereof
• CPC Class Codes: G03F 1/68 Preparation processes not covered by groups G03F1/20 - G03F1/50
• CPC Class Codes: G03F 7/70433 Layout for increasing efficiency or for compensating imaging errors, e.g. layout of exposure fields for reducing focus errors; Use of mask features for increasing efficiency or for compensating imaging errors
• 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: G06F 17/10 Complex mathematical operations function generation by table look-up G06F1/03; evaluation of elementary functions by calculation G06F7/544
• CPC Class Codes: G06F 30/00 Computer-aided design [CAD]
• CPC Class Codes: G06F 30/20 Design optimisation, verification or simulation optimisation, verification or simulation of circuit designs G06F30/30

Abstract

Methods according to the present invention provide computationally efficient techniques for designing gauge patterns for calibrating a model for use in a simulation process. More specifically, the present invention relates to methods of designing gauge patterns that achieve complete coverage of parameter variations with minimum number of gauges and corresponding measurements in the calibration of a lithographic process utilized to image a target design having a plurality of features. According to some aspects, a method according to the invention includes transforming the space of model parametric space (based on CD sensitivity or Delta TCCs), then iteratively identifying the direction that is most orthogonal to existing gauges'"'"' CD sensitivities in this new space, and determining most sensitive line width/pitch combination with optimal assist feature placement which leads to most sensitive CD changes along that direction in model parametric space.

Claims

1. A method comprising:

identifying a parameter of a simulation model of a lithographic process;

designing, by a hardware computer system, a test gauge to calibrate the parameter of the simulation model, the test gauge including two main features having a difference in a metric between them that maximizes sensitivity to changes with respect to the parameter; and

producing, by the hardware computer system, electronic data to enable production of the test gauge by the lithographic process, where a physical instance of the test gauge is produced by the lithographic process.

2. A method according to claim 1, wherein the two main features are lines and wherein designing the test gauge includes computing optimal first and second respective line widths for the two main features.

3. A method according to claim 1, wherein the two main features are lines and wherein designing the test gauge includes computing an optimal center-to-center distance between the two main features.

4. A method according to claim 1, wherein the metric is critical dimension.

5. A method according to claim 1, further comprising computing one or more assisting features for arrangement in the test gauge that further maximizes the sensitivity.

6. A method according to claim 1, wherein the designing includes:

determining a perturbed value of the identified parameter;

using the perturbed value to compute a delta operator; and

using the delta operator to compute an aerial image.

7. A method according to claim 6, wherein the delta operator comprises transmission cross coefficients.

8. A method according to claim 5, wherein computing the one or more assisting features includes applying manufacturability constraints to a size and spacing of the assisting features.

9. A method according to claim 1, wherein sensitivity is characterized in connection with predicted and actual critical dimensions of the two main features printed using the lithographic process.

10. A non-transitory computer program product having recorded thereon instructions which, when executed by a computer system, cause the computer system to at least:

identify a parameter of a simulation model of a lithographic process;

design a test gauge to calibrate the parameter of the simulation model, the test gauge including two main features having a difference in a metric between them that maximizes sensitivity to changes with respect to the parameter; and

produce electronic data to enable production of the test gauge by the lithographic process, where a physical instance of the test gauge is produced by the lithographic process.

11. A computer program product according to claim 10, wherein the two main features are lines and wherein design of the test gauge includes computation of optimal first and second respective line widths for the two main features.

12. A computer program product according to claim 10, wherein the two main features are lines and wherein design of the test gauge includes computation of an optimal center-to-center distance between the two main features.

13. A computer program product according to claim 10, wherein the metric is critical dimension.

14. A computer program product according to claim 10, wherein the instructions are further configured to cause the computer to compute one or more assisting features for arrangement in the test gauge that further maximizes the sensitivity.

15. A computer program product according to claim 10, wherein the instructions configured to cause the computer to design the test gauge are further configured to cause the computer to:

determine a perturbed value of the identified parameter;

use the perturbed value to compute a delta operator; and

use the delta operator to compute an aerial image.

16. A computer program product according to claim 15, wherein the delta operator comprises transmission cross coefficients.

17. A computer program product according to claim 14, wherein computation of the one or more assisting features includes application of manufacturability constraints to a size and spacing of the assisting features.

18. A computer program product according to claim 10, wherein sensitivity is characterized in connection with predicted and actual critical dimensions of the two main features printed using the lithographic process.

19. A method comprising:

forming a physical test gauge using a lithographic process, wherein the test gauge includes two main features having a difference in a metric between them that maximizes sensitivity to changes with respect to a parameter of a simulation model of the lithographic process; and

measuring the formed test gauge to produce results for calibration of the parameter of the simulation model.

20. A method according to claim 19, wherein the two main features are lines and wherein the difference comprises a difference in respective line widths for the two main features and/or comprises center-to-center distance between the two main features.