Metrology tool with combined XRF and SAXS capabilities

Patent metadata

Field	Value
Publication number	US-9778213-B2
Application number	US-201414461416-A
Country	US
Kind code	B2
Filing date	Aug 17, 2014
Priority date	Aug 19, 2013
Publication date	Oct 3, 2017
Grant date	Oct 3, 2017

Abstract

Methods and systems for performing simultaneous X-ray Fluorescence (XRF) and small angle x-ray scattering (SAXS) measurements over a desired inspection area of a specimen are presented. SAXS measurements combined with XRF measurements enables a high throughput metrology tool with increased measurement capabilities. The high energy nature of x-ray radiation penetrates optically opaque thin films, buried structures, high aspect ratio structures, and devices including many thin film layers. SAXS measurements of a particular location of a planar specimen are performed at a number of different out of plane orientations. This increases measurement sensitivity, reduces correlations among parameters, and improves measurement accuracy. In addition, specimen parameter values are resolved with greater accuracy by fitting data sets derived from both SAXS and XRF measurements based on models that share at least one material parameter. The fitting can be performed sequentially or in parallel.

First claim

What is claimed is:

1. A metrology tool comprising:
at least one x-ray illumination source configured to generate an amount of incident x-ray radiation directed to a specimen;
a first x-ray detector configured to receive an amount of radiation scattered from the specimen in response to the incident x-ray radiation and generate signals indicative of a first property of the specimen, wherein the at least one x-ray illumination source and the first x-ray detector are disposed in a Small Angle X-Ray Scatterometry (SAXS) measurement configuration; and
a second x-ray detector configured to receive an amount of radiation fluoresced from the specimen in response to the incident x-ray radiation and generate signals indicative of a second property of the specimen, wherein the at least one x-ray illumination source and the second x-ray detector are disposed in a X-Ray Fluorescence (XRF) measurement configuration.

2. The metrology tool of claim 1 , further comprising:
an x-ray illumination optics subsystem configured to shape and direct the incident x-ray radiation to the specimen over a first inspection area of the specimen.

3. The metrology tool of claim 1 , further comprising:
a first x-ray illumination optics subsystem configured to shape and direct a first portion of the incident x-ray radiation to the specimen over a first inspection area of the specimen, wherein the first portion of the incident x-ray radiation is generated by a first x-ray illumination source; and
a second x-ray illumination optics subsystem configured to shape and direct a second portion of the incident x-ray radiation to the specimen over a second inspection area of the specimen, wherein the second portion of the incident x-ray radiation is generated by a second x-ray illumination source.

4. The metrology tool of claim 2 , further comprising:
a beam controller operable to communicate a command signal to the x-ray illumination optics subsystem to redirect the incident x-ray radiation, wherein the command signal is determined based at least in part on the amount of radiation received by the first x-ray detector.

5. The metrology tool of claim 1 , further comprising:
a wafer positioning system configured to selectively position the specimen at a plurality of different orientations out of plane from a planar surface of the specimen, wherein the wafer positioning system is configured to selectively position the specimen within a range of at least one degree about one or more axes of rotation aligned in-plane with the surface of the specimen.

6. The metrology tool of claim 1 , further comprising:
a model building and analysis engine configured to:
generate a structural model of a measurement target of the specimen;
generate a XRF response model and a SAXS response model based at least in part on the structural model, wherein both the XRF response model and the SAXS response model include at least one common material parameter from the structural model;
receive the signals generated by the first x-ray detector to obtain a SAXS measurement data set;
receive the signals generated by the second x-ray detector to obtain a XRF measurement data set;
determine at least one specimen parameter value based on a fitting analysis on the XRF measurement data set with the XRF response model and a fitting analysis of the SAXS measurement data set with the SAXS response model; and
store the at least one specimen parameter value.

7. The metrology tool of claim 6 , wherein a value of the at least one common material parameter is determined based on the fitting analysis on the XRF measurement data set and the determined value is treated as a constant in the fitting analysis of the SAXS measurement data set.

8. The metrology tool of claim 6 , wherein the at least one common material parameter is treated as a global parameter in a parallel fitting analysis including both the fitting analysis on the XRF data set and the fitting analysis of the SAXS data set.

9. The metrology tool of claim 1 , wherein the at least one x-ray illumination source and the first x-ray detector are disposed in a Transmission Small Angle X-Ray Scatterometry (T-SAXS) or a grazing incidence Small Angle X-ray Scatterometry (GI-SAXS) configuration.

10. The metrology tool of claim 1 , wherein the at least one x-ray illumination source and the second x-ray detector are disposed in a confocal XRF measurement configuration or a total reflection XRF configuration.

11. The metrology tool of claim 1 , wherein the at least one x-ray illumination source comprises,
an electron beam source configured to direct an electron beam at a primary target that generates an amount of primary radiation in response to the electron beam, and
a secondary target that receives the amount of primary radiation and generates the amount of incident x-ray radiation in response to the amount of primary radiation.

12. A method comprising:
illuminating a specimen with an amount of incident x-ray radiation generated by at least one x-ray illumination source;
receiving an amount of radiation scattered from the specimen in response to the incident x-ray radiation on a first x-ray detector, wherein the at least one x-ray illumination source and the first x-ray detector are disposed in a Small Angle X-Ray Scatterometry (SAXS) measurement configuration;
generating signals indicative of a first property of the specimen in response to the amount of scattered radiation;
receiving an amount of radiation fluoresced from the specimen in response to the incident x-ray radiation on a second detector, wherein the at least one x-ray illumination source and the second x-ray detector are disposed in a X-Ray Fluorescence (XRF) measurement configuration;
generating signals indicative of a second property of the specimen in response to the amount of fluoresced radiation; and
storing an indication of the signals indicative of the first and second properties of the specimen.

13. The method of claim 12 , further comprising:
redirecting at least a portion of the amount of incident x-ray radiation based on the received amount of radiation scattered from the specimen.

14. The method of claim 12 , further comprising:
rotating the specimen to a plurality of different orientations out of plane from the surface of the specimen.

15. The method of claim 12 , further comprising:
generating a structural model of a measurement target of the specimen;
generating a XRF response model and a SAXS response model based at least in part on the structural model, wherein both the XRF response model and the SAXS response model include at least one common material parameter from the structural model;
receiving the signals indicative of a first property of the specimen in response to the amount of scattered radiation to obtain a SAXS measurement data set;
receiving the signals indicative of a second property of the specimen in response to the amount of fluoresced radiation to obtain a XRF measurement data set;
determining at least one specimen parameter value based on a fitting analysis on the XRF measurement data set with the XRF response model and a fitting analysis of the SAXS measurement data set with the SAXS response model; and
storing the at least one specimen parameter value.

16. The method of claim 15 , further comprising:
determining a value of the at least one common material parameter based on the fitting analysis on the XRF measurement data set, wherein the determined value is treated as a constant in the fitting analysis of the SAXS measurement data set.

17. The method of claim 15 , further

Assignees

• Kla Tencor Corp

Inventors

• Bakeman Michael S
• Shchegrov Andrei V
• Peterlinz Kevin
• Dziura Thaddeus Gerard

Classifications

• G01N2223/6116

  semiconductor wafer · CPC title

• G01N23/223 Primary

  by irradiating the sample with X-rays or gamma-rays and by measuring X-ray fluorescence · CPC title

• G01N23/201

  by measuring small-angle scattering · CPC title