Etch variation tolerant optimization

• US 10,712,653 B2
• Filed: 01/28/2019
• Issued: 07/14/2020
• Est. Priority Date: 06/25/2014
• Status: Active Grant

• Current Assignee: ASML Netherlands BV (ASML Holding NV)
• Original Assignee: ASML Netherlands BV (ASML Holding NV)
• Inventors: Liu, Xiaofeng
• Primary Examiner(s): Young, Christopher G
• Application Number:
  US16/258,884
• Publication Number:
  US 20190155145A1
• Time in Patent Office: 533 Days
• Field of Search: 430 5, 430 30, 716 51, 716 53, 716 54, 716 55
• CPC Class Codes: G03F 1/36 Masks having proximity correction features; Preparation thereof, e.g. optical proximity correction [OPC] design processes
• CPC Class Codes: G03F 1/42 Alignment or registration features, e.g. alignment marks on the mask substrates
• 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 7/70125 Use of illumination settings tailored to particular mask patterns details of setting means G03F7/70091
• 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 2119/18 Manufacturability analysis or optimisation for manufacturability
• CPC Class Codes: G06F 30/00 Computer-aided design [CAD]

Abstract

A method to improve a lithographic process for imaging a portion of a design layout onto a substrate using a lithographic projection apparatus and for transferring the imaged portion of the design layout to the substrate by an etching process, which method includes: determining a value of at least one evaluation point of the lithographic process for each of a plurality of variations of the etching process; computing a multi-variable cost function of a plurality of design variables that are characteristics of the lithographic process, wherein the multi-variable cost function is a function of deviation from the determined values of the at least one evaluation point; and reconfiguring the characteristics of the lithographic process by adjusting the design variables until a termination condition is satisfied. This method may reduce the need of repeated adjustment to the lithographic process when the etching process varies.

Claims

1. A method to improve a lithographic process for imaging a portion of a design layout onto a substrate using a lithographic projection apparatus and for transferring the imaged portion of the design layout to the substrate by an etching process, the method comprising:

evaluating, by a hardware computer system, one or more design variables that are characteristics of the lithographic process with respect to variation of the etching process to identify one or more values of the one or more design variables tolerant to etching process variation;

computing, by the hardware computer system, a multi-variable cost function of a plurality of design variables that are characteristics of the lithographic process, wherein the plurality of design variables of the cost function are other than the one or more design variables tolerant to etching process variation; and

reconfiguring one or more of the characteristics of the lithographic process by adjusting one or more of the design variables of the cost function and re-evaluating the cost function, until a termination condition for the cost function is satisfied.

2. The method of claim 1, wherein the evaluating comprises determining a value of an evaluation point of the lithographic process for each of a plurality of variations of the etching process and wherein the evaluation point is selected from:

a point of a resist image or of an aerial image or of the design layout, dose, focus, throughput, process window, critical dimension, resist contour distance, worst defect size, or best focus shift.

3. The method of claim 2, wherein the evaluating further comprises evaluating a function of a deviation from the determined values of the evaluation point.

4. The method of claim 1, wherein at least one of the design variables is a characteristic of an illumination of a patterning device, the design layout, projection optics, or a combination thereof.

5. The method of claim 1, wherein iterative reconfiguration is performed with a constraint dictating a range of at least one of the design variables.

6. The method of claim 5, wherein the constraint includes one or more selected from:

a tuning range, a rule governing patterning device manufacturability, or interdependence between the design variables.

7. The method of claim 1, wherein the design layout comprises an assist feature, and wherein the assist feature comprises a sub-resolution assist feature.

8. A computer program product comprising a non-transitory computer-readable medium having instructions therein, the instructions, upon execution by a computer system, configured to cause the computer system to at least:

for a lithographic process for imaging a portion of a design layout onto a substrate using a lithographic projection apparatus and for transferring the imaged portion of the design layout to the substrate by an etching process, evaluate, by a hardware computer system, one or more design variables that are characteristics of the lithographic process with respect to variation of the etching process to identify one or more values of the one or more design variables tolerant to etching process variation;

compute, by the hardware computer system, a multi-variable cost function of a plurality of design variables that are characteristics of the lithographic process, wherein the plurality of design variables of the cost function is other than the one or more design variables tolerant to etching process variation; and

reconfigure one or more of the characteristics of the lithographic process by adjusting one or more of the design variables of the cost function and re-evaluating the cost function, until a termination condition for the cost function is satisfied.

9. The computer program product of claim 8, wherein the instructions configured to cause the computer system to evaluate one or more design variables are further configured to cause the computer system to determine a value of an evaluation point of the lithographic process for each of a plurality of variations of the etching process.

10. The computer program product of claim 9, wherein the evaluation point is selected from:

a point of a resist image or of an aerial image or of the design layout, dose, focus, throughput, process window, critical dimension, resist contour distance, worst defect size, or best focus shift.

11. The computer program product of claim 9, wherein the instructions configured to cause the computer system to evaluate one or more design variables are further configured to cause the computer system to evaluate a function of a deviation from the determined values of the evaluation point.

12. The computer program product of claim 8, wherein at least one of the design variables is a characteristic of an illumination of a patterning device, the design layout, projection optics, or a combination thereof.

13. The computer program product of claim 8, wherein iterative reconfiguration is performed with a constraint dictating a range of at least one of the design variables, the constraint including one or more selected from:

a tuning range, a rule governing patterning device manufacturability, or interdependence between the design variables.

14. The computer program product of claim 8, wherein the design layout comprises an assist feature, and wherein the assist feature comprises a sub-resolution assist feature.

15. A computer program product comprising a non-transitory computer-readable medium having instructions therein, the instructions, upon execution by a computer system, configured to cause the computer system to at least:

for a lithographic process involving an imaging process for imaging a portion of a design layout onto a substrate using a lithographic projection apparatus and an etching process for transferring the imaged portion of the design layout to the substrate, compute a multi-variable cost function of a plurality of design variables that are characteristics of the imaging process, wherein the multi-variable cost function is a function of a value for an evaluation point for the imaging process for each of a plurality of variations of the etching process; and

reconfigure one or more of the characteristics of the lithographic process by adjusting one or more of the design variables and re-evaluating the cost function, until a termination condition for the cost function is satisfied.

16. The computer program product of claim 15, wherein the evaluation point is selected from:

a point of a resist image, of an aerial image or of the design layout, dose, focus, throughput, process window, critical dimension, resist contour distance, worst defect size, or best focus shift.

17. The computer program product of claim 15, wherein the multi-variable cost function is a function of a deviation of the value for the evaluation point for each of the plurality of variations of the etching process.

18. The computer program product of claim 17, wherein the deviation is a function of a difference between an actual or simulated value of the evaluation point and a determined value of the evaluation point for a variation of the etching process.

19. The computer program product of claim 17, wherein the deviation comprises an edge placement error.

20. The computer program product of claim 15, wherein the variations of the etching process comprise spatial biases of one or more features of the design layout.

21. A computer program product comprising a non-transitory computer-readable medium having instructions therein, the instructions, upon execution by a computer system, configured to cause the computer system to at least:

for a lithographic process involving an imaging process for imaging a portion of a design layout onto a substrate using a lithographic projection apparatus and an etching process for transferring the imaged portion of the design layout to the substrate, compute a multi-variable cost function of a plurality of design variables that are characteristics of the imaging process, wherein the multi-variable cost function is function of an illumination variable, a design layout variable and an etching process variable and the multi-variable cost function co-optimizes at least the illumination, design layout and etching process variables subject to at least etching process variation; and

reconfigure one or more of the characteristics of the lithographic process by adjusting one or more of the design variables and re-evaluating the cost function, until a termination condition for the cost function is satisfied.

22. The computer program product of claim 21, wherein the multi-variable cost function is a function of a value for an evaluation point for the imaging process for each of a plurality of variations of the etching process.

23. The computer program product of claim 22, wherein the evaluation point is selected from:

a point of a resist image, of an aerial image or of the design layout, dose, focus, throughput, process window, critical dimension, resist contour distance, worst defect size, or best focus shift.

24. The computer program product of claim 22, wherein the multi-variable cost function is a function of a deviation of the value for the evaluation point for each of the plurality of variations of the etching process.

25. The computer program product of claim 21, wherein the etching process variation comprise spatial biases of one or more features of the design layout.