Method and apparatus for design of a metrology target

• US 9,494,874 B2
• Filed: 12/19/2014
• Issued: 11/15/2016
• Est. Priority Date: 12/30/2013
• Status: Active Grant

• Current Assignee: ASML Netherlands BV (ASML Holding NV)
• Original Assignee: ASML Netherlands BV (ASML Holding NV)
• Inventors: Chen, Guangqing, Wang, Jen-Shiang, Bai, Shufeng
• Primary Examiner(s): Nguyen, Hung Henry
• Application Number:
  US14/578,036
• Publication Number:
  US 20150185626A1
• Time in Patent Office: 697 Days
• Field of Search: 355/52, 355/53, 355/55, 355/77, 716/20, 716/53
• 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 7/70625 Dimensions, e.g. line width, critical dimension [CD], profile, sidewall angle or edge roughness
• CPC Class Codes: G03F 7/70633 Overlay, i.e. relative alignment between patterns printed by separate exposures in different layers, or in the same layer in multiple exposures or stitching
• CPC Class Codes: G03F 7/70641 Focus
• CPC Class Codes: G03F 7/70683 Mark designs

Abstract

A system to, and a method to, select a metrology target for use on a substrate including performing a lithographic simulation for a plurality of points on a process window region for each proposed target, identifying a catastrophic error for any of the plurality of points for each proposed target, eliminating each target having a catastrophic error at any of the plurality of points, performing a metrology simulation to determine a parameter over the process window for each target not having a catastrophic error at any of the plurality of points, and using the one or more resulting determined simulated parameters to evaluate target quality.

Claims

1. A method of selecting a metrology target for use on a substrate, the method comprising:

performing a lithographic simulation for a plurality of points on a process window region for a plurality of proposed metrology targets;

determining the presence or absence of a catastrophic error at each of the plurality of points for each of the proposed metrology targets;

performing a metrology simulation to determine a value for a parameter over the process window only for each proposed metrology target that does not have a catastrophic error at any of the plurality of points; and

using the resulting determined simulated parameter value to evaluate target quality of the one or more of the proposed metrology targets.

2. The method of claim 1, wherein determined simulated parameter values are used to rank a plurality of proposed metrology targets.

3. The method of claim 1, wherein performing the metrology simulation comprises determining values for a plurality of parameters over the process window and wherein using the resulting determined simulated parameter value comprises using the values for the plurality of determined simulated parameters to evaluate target quality.

4. The method of claim 3, wherein each simulated parameter is used in sequence to progressively filter a plurality of proposed metrology targets.

5. The method of claim 3, wherein each simulated parameter is used in weighted combination to rank a plurality of proposed metrology targets.

6. The method of claim 1, wherein the lithographic simulation comprises an optical-resist simulation.

7. The method of claim 1, wherein the metrology simulation comprises a diffraction-based overlay simulation.

8. The method of claim 1, wherein the catastrophic error comprises at least one error selected from the group consisting of:

bridging, necking between lines, resist collapse, one or more extra lines, one or more missing lines, excessive top loss, minimum critical dimension, and minimum line space.

9. The method of claim 1, wherein the process window comprises a region in a dose/focus space over which a lithographic image parameter equals or surpasses a selected threshold.

10. A non-transitory computer readable medium encoded with machine executable instructions to perform a method of selecting a metrology target for use on a substrate, the method comprising:

performing a lithographic simulation for a plurality of points on a process window region for a plurality of proposed metrology targets;

determining the presence or absence of a catastrophic error at each of the plurality of points for each of the proposed metrology targets;

performing a metrology simulation to determine a value for a parameter over the process window only for each proposed metrology target that does not have a catastrophic error at any of the plurality of points; and

using the resulting determined simulated parameter value to evaluate target quality of the one or more of the proposed metrology targets.

11. The computer readable medium of claim 10, wherein determined simulated parameter values are used to rank a plurality of proposed metrology targets.

12. The computer readable medium of claim 10, wherein performing the metrology simulation comprises determining values for a plurality of parameters over the process window and wherein using the resulting determined simulated parameter value comprises using the values for the plurality of determined simulated parameters to evaluate target quality.

13. The computer readable medium of claim 12, wherein each simulated parameter is used in sequence to progressively filter a plurality of proposed metrology targets.

14. The computer readable medium of claim 12, wherein each simulated parameter is used in weighted combination to rank a plurality of proposed metrology targets.

15. The computer readable medium of claim 10, wherein the metrology simulation comprises an optical metrology simulation.

16. The computer readable medium of claim 15 wherein the optical metrology simulation comprises a simulation of a diffraction based overlay metrology tool.

17. A system to select a metrology target for use on a substrate, the system comprising:

a processing unit configured and arranged to;

perform a lithographic simulation for a plurality of points on a process window region for a plurality of proposed metrology targets;

determine the presence or absence of a catastrophic error at each of the plurality of points for each of the proposed metrology targets;

perform a metrology simulation to determine a value for a parameter over the process window only for each proposed metrology target that does not have a catastrophic error at any of the plurality of points; and

use the resulting determined simulated parameter value to evaluate target quality of the one or more of the proposed metrology targets.

18. A method, comprising:

evaluating a plurality of metrology target designs at a plurality of points of a lithographic process window for a catastrophic error;

for a plurality of metrology target designs that are evaluated not to suffer a catastrophic error at any of the plurality of points, determining a metrology performance indicator for each of the plurality of metrology target designs evaluated not to suffer a catastrophic error; and

providing an evaluation of the plurality of metrology target designs evaluated not to suffer a catastrophic error based on the metrology performance indicator.