Optical metrology of lithographic processes using asymmetric sub-resolution features to enhance measurement

Patent metadata

Field	Value
Publication number	US-10417359-B2
Application number	US-201615379473-A
Country	US
Kind code	B2
Filing date	Dec 14, 2016
Priority date	Dec 17, 2015
Publication date	Sep 17, 2019
Grant date	Sep 17, 2019

Abstract

A process of calibrating a model, the process including: obtaining training data including: scattered radiation information from a plurality of structures, individual portions of the scattered radiation information being associated with respective process conditions being characteristics of a patterning process of the individual structures; and calibrating a model with the training data by determining a ratio relating a change in one of the process characteristics to a corresponding change in scattered radiation information.

First claim

What is claimed is:

1. A method of calibrating a model, the method comprising:
obtaining training data comprising scattered radiation information from a plurality of structures, individual portions of the scattered radiation information being associated with respective process conditions being characteristics of a patterning process of the individual structures; and
calibrating, by a hardware processor system, a model with the training data by determining a ratio relating a change in one of the process characteristics to a corresponding change in scattered radiation information.

2. The method of claim 1 , wherein calibrating comprises determining a further ratio relating a change in another one of the process characteristics to a change in scattered radiation information.

3. The method of claim 2 , wherein the ratio is a partial derivative of focus with respect to scattered radiation information or a reciprocal, and wherein the further ratio is a partial derivative of dose with respect to scattered radiation information or a reciprocal.

4. The method of claim 1 , wherein the model is based on at least three terms of a Taylor series expansion.

5. The method of claim 1 , wherein the model includes a second order derivative of one of the process characteristics with respect to scattered radiation information or an inverse of the second order derivative.

6. The method of claim 1 , wherein calibrating the model comprises determining model parameters with a Markov chain Monte Carlo algorithm.

7. The method of claim 1 , wherein calibrating the model comprises determining model parameters with a Metropolis-Hastings algorithm.

8. The method of claim 1 , wherein calibrating the model comprises determining model parameters by iteratively adjusting the model parameters based on an aggregate measure of agreement between the respective iteration of the model and at least some of the training data.

9. The method of claim 1 , wherein the scattered radiation information comprises:
a plurality of test conditions indicative of process characteristics of a patterning process used to pattern the plurality of test structures on the one or more substrates according to a focus-exposure matrix, with different patterned test structures being patterned under different test conditions,
pupil-intensity measurements of the plurality of patterned test structures, and
data indicating which measurements correspond to which test conditions,
wherein the model infers a characteristic of a patterning process from optical measurement of a test structure patterned with the patterning process.

10. The method of claim 1 , wherein the training data comprises simulated training data obtained based on a model of the patterning process and a model of the scattered radiation information.

11. The method of claim 1 , comprising using a patterning device configured to define, at least in part, a test structure having a main feature and one or more sub-resolution features that are proximate to, and substantially parallel to, the main feature, to pattern a substrate with the test structure.

12. The method of claim 11 , wherein the one or more sub-resolution features include a first sub-resolution feature spaced away from the main feature on a first side of the main feature by a first distance sized to affect the corresponding patterned test structure.

13. The method of claim 12 , wherein the one or more sub-resolution features include a second sub-resolution feature spaced away from the main feature on a second side of the main feature, different from the first side, by a second distance that is different from the first distance and is sized to affect the corresponding patterned test structure differently from the first sub-resolution feature.

14. The method of claim 11 , wherein the one or more sub-resolution features include a plurality of sub-resolution features spaced away from the main feature on the same side of the main feature by a plurality of different respective distances each sized to affect the corresponding patterned test structure.

15. The method of claim 11 , wherein the one or more sub-resolution features include a sub-resolution inverse feature disposed within the main feature a first distance away from a side of the main feature and a second distance away from an opposing side of the main feature, the second distance being different from the first distance.

16. The method of claim 11 , wherein:
the main feature includes a generally straight bar-shaped structure;
the one or more sub-resolution features comprise a pair of smaller bar-shaped structures extending along the main feature on opposing sides of the main feature at different distances from the main feature, wherein a width of the smaller bars is smaller than a resolution limit of the patterning process, and wherein a width of the main feature is greater than or equal to the resolution limit; and
the patterned test structure has sidewalls of different slopes on opposing sides of the generally straight bar-shaped structure, and an amount of difference between the slopes varies according to variations of the focus or exposure.

17. The method of claim 11 , comprising:
patterning a production run of substrates to produce patterned test structures on the production run of substrates along with at a pattern of at least part of a production device;
optically measuring at least some of the patterned test structures within the production run before completing the patterning of the production run;
inferring a process characteristic of the patterning process of the production run based on the corresponding optical measurements and a correlated model; and
determining that a targeted process characteristic is different from the inferred process characteristic.

18. A method of inferring a parameter of a patterning process, the method comprising:
obtaining a scattered radiation measurement of a patterned structure on a substrate; and
inferring, by a hardware processor system and using a calibrated model, a process characteristic of the patterning of the patterned structure based on the measurement, wherein the calibrated model comprises a ratio relating a change in a process characteristic to a change in scattered radiation measurement.

19. The method of claim 18 , wherein the ratio is a partial derivative of focus with respect to scattered radiation measurement or a reciprocal, and wherein the model comprises a further ratio that is a partial derivative of dose with respect to scattered radiation measurement or a reciprocal.

20. The method of claim 18 , comprising calibrating the model, the calibrating comprising:
obtaining training data comprising:
a plurality of test conditions indicative of process characteristics of a patterning process used to pattern a plurality of test structures on one or more substrates, with different patterned test structures being patterned under different test conditions,
pupil-intensity measurements of the plurality of patterned test structures, and
data indicating which measurements correspond to which test conditions; and

calibrating the model with the training data by determining the ratio.

21. The method of claim 18 , wherein the structure is a test structure and the method comprises using a patterning device configured to define, at least in part, a test structure having a main feature and one or more sub-resolution features that are proximate to, and substantially parallel to, the main feature, to pattern a substrate with the test

Assignees

• Asml Netherlands Bv

Inventors

• Socha Robert John
• Wallow Thomas I

Classifications

• G06N7/01

  Probabilistic graphical models, e.g. probabilistic networks · CPC title

• G03F7/70625

  Dimensions, e.g. line width, critical dimension [CD], profile, sidewall angle or edge roughness · CPC title

• G06F2111/10

  Numerical modelling · CPC title

• G06F30/20 Primary

  Design optimisation, verification or simulation (optimisation, verification or simulation of circuit designs G06F30/30) · CPC title

• G03F7/70633

  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 title