Model building and analysis engine for combined X-ray and optical metrology

Patent metadata

Field	Value
Publication number	US-10013518-B2
Application number	US-201313935275-A
Country	US
Kind code	B2
Filing date	Jul 3, 2013
Priority date	Jul 10, 2012
Publication date	Jul 3, 2018
Grant date	Jul 3, 2018

Abstract

Structural parameters of a specimen are determined by fitting models of the response of the specimen to measurements collected by different measurement techniques in a combined analysis. Models of the response of the specimen to at least two different measurement technologies share at least one common geometric parameter. In some embodiments, a model building and analysis engine performs x-ray and optical analyses wherein at least one common parameter is coupled during the analysis. The fitting of the response models to measured data can be done sequentially, in parallel, or by a combination of sequential and parallel analyses. In a further aspect, the structure of the response models is altered based on the quality of the fit between the models and the corresponding measurement data. For example, a geometric model of the specimen is restructured based on the fit between the response models and corresponding measurement data.

First claim

What is claimed is:

1. A combined x-ray/optical metrology tool comprising:
an x-ray illumination system including an x-ray illumination source and x-ray illumination optics configured to shape and direct an incident x-ray beam to an inspection area of a specimen;
an x-ray detector configured to detect an amount of x-ray radiation from the specimen in response to the incident x-ray beam;
an optical illumination system including an optical illumination source and optical illumination optics configured to shape and direct an incident optical illumination beam to the inspection area of the specimen; and
an optical detector configured to detect an amount of optical radiation from the specimen in response to the incident optical illumination beam; and
a geometric model building module configured to generate a geometric model of a structure of the specimen;
an optical response function building module configured to generate an optical response model of a response of the structure of the specimen to incident optical radiation based at least in part on the geometric model;
an x-ray response function building module configured to generate an x-ray response model of a response of the structure of the specimen to incident x-ray radiation based at least in part on the geometric model, wherein both the optical response model and the x-ray response model include at least one common geometric parameter from the geometric model; and
a fitting analysis module configured to:
receive a first amount of measurement data indicative of the amount of optical radiation detected from the specimen in response to the optical illumination beam incident on the specimen;
receive a second amount of measurement data indicative of the amount of x-ray radiation detected from the specimen in response to the x-ray illumination beam incident on the specimen;
determine a value of the at least one common geometric parameter based on a fitting of the optical response model with the first amount of measurement data and a fitting of the x-ray response model to the second amount of measurement data in a combined analysis, wherein the value of the at least one geometric parameter in the fitting of the optical response model is linked to the value of the at least one geometric parameter in the fitting of the x-ray response model by a predetermined function; and
output the at least one specimen parameter value for storage in a memory.

2. The combined x-ray/optical metrology tool of claim 1 , wherein the value of the at least one common geometric-parameter is determined based on the fitting of the x-ray response model to the second amount of-measurement data and the determined value is treated as a constant in the fitting of the optical-response model with the first amount of measurement data to determine at least one specimen-parameter value.

3. The combined x-ray/optical metrology tool of claim 1 , wherein the at least one common geometric parameter is treated as a global parameter in a parallel fitting analysis including both the fitting of the optical response model with the first amount of measurement data and the fitting of the x-ray response model to the second amount of measurement data.

4. The combined x-ray/optical metrology tool of claim 2 , wherein the fitting of the optical response model with the first amount of measurement data involves minimizing a cost function.

5. The combined x-ray/optical metrology tool of claim 3 , wherein the parallel fitting analysis involves minimizing a combined cost function.

6. The combined x-ray/optical metrology tool of claim 1 , wherein the fitting analysis module is further configured to:
determine a residual value of a cost function associated with the fitting of the first amount of measurement data with the optical response model and the fitting of the second amount of measurement data with the x-ray response model;
determine if the residual value exceeds a predetermined threshold value;
restructure the geometric model of the structure of the specimen if the residual value exceeds the predetermined threshold value; and
store the geometric model of the structure of the specimen if the residual value does not exceed the predetermined threshold value.

7. The combined x-ray/optical metrology tool of claim 1 , wherein the optical response model and the x-ray response model share all of the geometric parameters of the geometric model.

8. The combined x-ray/optical metrology tool of claim 1 , wherein the at least one common geometric parameter is any of a line edge roughness, line width roughness, pore size, pore density, side wall angle, profile, film thickness, critical dimension, and pitch.

9. The combined x-ray/optical metrology tool of claim 1 , wherein the x-ray illumination beam and the optical illumination beam are incident to the inspection area of the specimen simultaneously, and wherein the incident optical illumination beam and the incident x-ray beam spatially overlap at the inspection area of the specimen.

10. The combined x-ray/optical metrology tool of claim 1 , wherein the x-ray illumination source is a liquid metal based xray illumination source.

11. A method comprising:
illuminating an inspection area of a specimen with an incident x-ray beam from an x-ray illumination source;
detecting an amount of x-ray radiation from the specimen in response to the incident xray beam by an x-ray detector;
illuminating the inspection area of the specimen with an incident optical illumination beam from an optical illumination source;
detecting an amount of optical radiation from the specimen in response to the incident optical illumination beam by an optical detector;
generating a geometric model of a structure of a specimen;
generating an optical response model and an x-ray response model based at least in part on the geometric model, wherein both the optical response model and the x-ray response model include at least one common geometric parameter from the geometric model;
receiving a first amount of measurement data based on an amount of optical radiation detected from the specimen in response to an optical illumination beam incident on the specimen;
receiving a second amount of measurement data based on an amount of x-ray radiation detected from the specimen in response to an x-ray illumination beam incident on the specimen;
determining a value of the at least one common geometric parameter based on a fitting analysis of the first amount of measurement data with the optical response model and a fitting analysis of the second amount of measurement data with the x-ray response model in a combined analysis, wherein the value of the at least one geometric parameter in the fitting of the optical response model is linked to the value of the at least one geometric parameter in the fitting of the x-ray response model by a predetermined function; and
storing the at least one specimen parameter value.

12. The method of claim 11 , further comprising:
determining the value of the at least one common geometric parameter based on the fitting analysis of the second amount of measurement data, and wherein the determined value of the at least one common geometric parameter is treated as a constant in the fitting analysis of the first amount of measurement data.

13. The method of claim 11 , further comprising:
determining the value of the at least one common geometric parameter based on a parallel fitting analysis of the first amount of measurement data with the optical response model and the second amount of measurement data with the x-ray response model.

14. The method of claim 11 , further comprising:
determining a resi

Assignees

• Kla Tencor Corp

Inventors

• Bakeman Michael S
• Shchegrov Andrei V
• Zhao Qiang
• Tan Zhengquan

Classifications

• G03F1/70

  Adapting basic layout or design of masks to lithographic process requirements, e.g., second iteration correction of mask patterns for imaging · CPC title

• G03F7/70608 Primary

  Monitoring the unpatterned workpiece, e.g. measuring thickness, reflectivity or effects of immersion liquid on resist · CPC title

• G01N21/00 Primary

  Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light (G01N3/00 - G01N19/00 take precedence) · CPC title

• G01N23/00

  Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 · CPC title

• G06F30/39 Primary

  Circuit design at the physical level (physical level design for reconfigurable circuits G06F30/347) · CPC title