Methods and systems for measuring periodic structures using multi-angle x-ray reflectance scatterometry (XRS)
Methods and systems for measuring periodic structures using multi-angle X-ray reflectance scatterometry (XRS) are disclosed. For example, a method of measuring a sample by X-ray reflectance scatterometry involves impinging an incident X-ray beam on a sample having a periodic structure to generate a scattered X-ray beam, the incident X-ray beam simultaneously providing a plurality of incident angles and a plurality of azimuthal angles. The method also involves collecting at least a portion of the scattered X-ray beam.
1. A method of characterizing a sample by X-ray reflectance scatterometry, the method comprising:
impinging an incident X-ray beam having an energy of 1 keV or less on a sample having a periodic structure to generate X-ray scattering having multiple diffraction orders, while configuring the incident X-ray beam to converge in an incidence and azimuth planes to thereby simultaneously provide a plurality of incident angles and a plurality of azimuthal angles and thereby cause angular separation of the multiple diffraction orders of the X-ray scattering; and,
sampling an intensity of at least a portion of the X-ray scattering.
2. A system for measuring a sample by X-ray reflectance scatterometry, the system comprising:
an X-ray source for generating an X-ray beam having an energy of approximately 1 keV or less;
a sample holder for positioning a sample having a periodic structure;
a monochromator positioned between the X-ray source and the sample holder, the monochromator for focusing the X-ray beam to provide an incident X-ray beam to the sample holder, the incident X-ray beam simultaneously having a plurality of incident angles and a plurality of azimuthal angles, the monochromator configured to focus the X-ray beam so as to cause multiple orders of X-ray diffraction from the sample to be spatially separated; and
a detector for collecting at least a portion of a scattered X-ray beam from the sample.
3. The method of claim 1 , wherein sampling the intensity is done simultaneously for the multiple diffraction orders.
4. The method of claim 3 , wherein the multiple diffraction orders include zero and first orders.
5. The method of claim 1 , wherein sampling the intensity is done by collecting at least a portion of a scattered X-ray beam onto a two-dimensional detector.
6. The method of claim 1 , wherein sampling the intensity is done by scanning a a slit for the detector.
7. The method of claim 1 , wherein configuring the incident X-ray beam to converge comprises converging to an angle in the range from 20 degrees to 40 degrees.
8. The method of claim 1 , wherein configuring the incident X-ray beam to converge comprises converging such that a central axis of the incident X-ray beam has a fixed non-zero incident angle in a range of 10 degrees to 15 degrees from a horizontal plane.
9. The method of claim 1 , wherein configuring the incident X-ray beam to converge comprises passing the X-ray beam through a monochromator.
10. The method of claim 9 , further comprising configuring the monochromator to assure the sampling is substantially free of scattering order-overlap.
11. The method of claim 9 , wherein the incident X-ray beam is not collimated between the passing the X-ray beam through a monochromator and the impinging on the sample.
12. The method of claim 1 , wherein the range of the plurality of incident angles is less than an angle of a nominal first-order angle at zero degrees.
13. The method of claim 1 , further comprising: estimating a shape of the periodic structure of the sample by inversion of scattering solutions relative to the sampled scattered signal intensity.
14. The method of claim 1 , wherein the converging incident X-ray beam has a wavelength that is less than a periodicity of the periodic structure.
15. The method of claim 1 , wherein the incident X-ray beam is generated from an X-ray source selected from the group consisting of carbon (C), molybdenum (Mo) and Rhodium (Rh).
16. The system of claim 2 , wherein the detector samples the intensity simultaneously for the multiple diffraction orders.
17. The system of claim 2 , wherein the detector comprises a two-dimensional detector.
18. The system of claim 2 , further comprising a scanning slit.
19. The system of claim 2 , wherein the monochromator focuses the X-ray beam to have converging angle in a range of from 20 degrees to 40 degrees.
20. The system of claim 2 , wherein the monochromator is configured to assure detected signal is substantially free of scattering order-overlap.
21. The system of claim 2 , wherein the incident X-ray beam is not collimated between the monochromator and the sample.
22. The system of claim 2 , wherein the range of the plurality of incident angles is less than an angle of a nominal first-order angle at zero degrees.
23. The system of claim 2 , further comprising a controller estimating a shape of the periodic structure of the sample by inversion of scattering solutions relative to the sampled scattered signal intensity.
24. The system of claim 2 , wherein the converging incident X-ray beam has a wavelength that is less than a periodicity of the periodic structure.
25. The system of claim 2 , wherein the X-ray source for generating an X-ray beam selected from the group consisting of carbon (C), molybdenum (Mo) and Rhodium (Rh).