Measurement of small box size targets

Patent metadata

Field	Value
Publication number	US-10139352-B2
Application number	US-201514882370-A
Country	US
Kind code	B2
Filing date	Oct 13, 2015
Priority date	Oct 18, 2014
Publication date	Nov 27, 2018
Grant date	Nov 27, 2018

Abstract

Methods and systems for measuring metrology targets smaller than the illumination spot size employed to perform the measurement are described herein. Collected measurement signals contaminated with information from structures surrounding the target area are reconstructed to eliminate the contamination. In some examples, measurement signals associated one or more small targets and one or more large targets located in close proximity to one another are used to train a signal reconstruction model. The model is subsequently used to reconstruct measurement signals from other small targets. In some other examples, multiple measurements of a small target at different locations within the target are de-convolved to estimate target area intensity. Reconstructed measurement signals are determined by a convolution of the illumination spot profile and the target area intensity. In a further aspect, the reconstructed signals are used to estimate values of parameters of interest associated with the measured structures.

First claim

What is claimed is:

1. A method comprising:
providing illumination radiation to a first plurality of small metrology targets and a plurality of large metrology targets disposed on a specimen, the illumination radiation provided by an illumination source of a metrology tool, the illumination radiation projected onto the first plurality of small metrology targets and the plurality of large metrology targets with an illumination spot size, wherein one or more of the first plurality of small metrology targets and one or more of the large metrology targets are located in close proximity to one another, and wherein each of the first plurality of small metrology targets occupies a smaller area than each of the plurality of large metrology targets;
detecting an amount of radiation from the first plurality of small metrology targets and the plurality of large metrology targets specimen in response to the illumination radiation, the amount of radiation detected by a detector of the metrology tool;
generating a measured response associated with the first plurality of small metrology targets and the plurality of large metrology targets based on the detected amounts of radiation, the measured response comprising a first set of measurement signals;
training a signal reconstruction model that maps the measurement signals generated from the measurements of the first plurality of small metrology targets to the measurement signals generated from the measurements of the plurality of large metrology targets;
providing illumination radiation to a second plurality of small metrology targets disposed on the specimen, the illumination radiation provided by the illumination source of the metrology tool, the illumination radiation projected onto the second plurality of small metrology targets with the illumination spot size, wherein each of the second plurality of small metrology targets occupies a smaller area than each of the plurality of large metrology targets;
detecting an amount of radiation from the second plurality of small metrology targets in response to the illumination radiation, the amount of radiation detected by the detector of the metrology tool;
generating a measured response associated with the second plurality of small metrology targets based on the detected amounts of radiation, the measured response comprising a second set of measurement signals; and
determining reconstructed measurement signals for each small metrology target of the second plurality of small metrology targets based on the second set of measurement signals and the trained signal reconstruction model.

2. The method of claim 1 , further comprising:
determining one or more parameter values associated with one or more parameters of interest for each of the second plurality of small metrology targets based on the reconstructed measurement signals.

3. The method of claim 2 , wherein the determining the one or more parameter values involves a signal response metrology model or a physically based measurement model.

4. The method of claim 3 , wherein the one or more parameters of interest include any of a critical dimension, a sidewall angle, a height, an overlay parameter, a focus parameter, and a dosage parameter.

5. The method of claim 1 , wherein the measurement signals associated with any of the large metrology targets and the first and second plurality of small metrology targets includes measurement signals associated with multiple measurement instances each involving a different measurement technique.

6. The method of claim 1 , wherein the measurement signals associated with any of the large metrology targets and the first and second plurality of small metrology targets includes measurement signals associated with multiple measurement instances each involving different values of one or more measurement system parameters.

7. The method of claim 6 , wherein the measurement system parameters include illumination wavelength, azimuth angle, angle of incidence, polarization state, depth of focus, and measurement location within each metrology target.

8. The method of claim 1 , wherein at least a portion of the measurement signals associated with the first and second plurality of small metrology targets are associated with a different measurement technique than at least a portion of the measurement signals associated with the plurality of large metrology targets.

9. The method of claim 1 , wherein at least a portion of the measurement signals associated with the first and second plurality of small metrology targets are associated with measurements involving different values of one or more measurement system parameters than at least a portion of the measurement signals associated with the plurality of large metrology targets.

10. The method of claim 1 , wherein an area of each of the first plurality of small metrology targets and each of the second plurality of small metrology targets is smaller than the illumination spot size, and wherein an area of each of the plurality of large metrology targets is larger than the illumination spot size.

11. The method of claim 1 , wherein at least one of the plurality of large metrology targets includes the same structures as at least one of the first plurality of small metrology targets.

12. A measurement system comprising:
an illumination source configured to supply illumination light having an illumination spot size projected onto a surface of a specimen;
a detector configured to collect an amount light from a first plurality of small metrology targets, a second plurality of small metrology targets, and a plurality of large metrology targets illuminated by the illumination light, wherein one or more of the first plurality of small metrology targets and one or more large metrology targets are located in close proximity to one another, and wherein an area of each of the small metrology targets is smaller than the illumination spot size and an area of each of the large metrology targets is larger than the illumination spot size; and
a computing system configured to:
train a signal reconstruction model that maps the measurement signals collected from the first plurality of small metrology targets to the measurement signals collected from the plurality of large metrology targets; and
determine reconstructed measurement signals for each small metrology target of the second plurality of small metrology targets based on the measurement signals collected from the first plurality of small metrology targets and the trained signal reconstruction model.

13. The measurement system of claim 12 , wherein the computing system is further configured to determine one or more values associated with one or more parameters of interest for each of the second plurality of small metrology targets based on the reconstructed measurement signals.

14. The measurement system of claim 12 , wherein the measurement signals associated with any of the large metrology targets and the first and second plurality of small metrology targets includes measurement signals associated with multiple measurement instances each involving a different measurement technique.

15. The measurement system of claim 12 , wherein the measurement signals associated with any of the large metrology targets and the first and second plurality of small metrology targets includes measurement signals associated with multiple measurement instances each involving different values of one or more measurement system parameters.

16. The measurement system of claim 15 , wherein the measurement system parameters include illumination wavelength, azimuth angle, angle of incidenc

Assignees

• Kla Tencor Corp
• Kla Tenor Corp

Inventors

• Pandev Stilian Ivanov
• Lu Wei
• Shchegrov Andrei V
• Rovira Pablo
• Madsen Jonathan M

Classifications

• G01N21/93

  Detection standards; Calibrating {baseline adjustment, drift correction} · CPC title

• G01N21/956 Primary

  Inspecting patterns on the surface of objects {(contactless testing of electronic circuits G01R31/308; testing currency G07D; manufacturing processes per se of semiconductor devices implementing a measuring step H10P74/20)} · CPC title