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 metrology method of measuring a sample having a periodic structure by X-ray reflectance scatterometry, the method comprising:
forming an incident converging X-ray beam having a central axis;
impinging the converging X-ray beam on the sample such that the central axis forms a non-zero incidence angle relative to a horizontal plane defined by an uppermost surface of the sample, and the central axis forms a non-zero azimuthal angle relative to an orthogonal to the periodic structure;
performing one measurement by collecting only a first order diffraction from the sample.
2. The method of claim 1 , wherein the incident converging X-ray beam has a converging angle approximately in the range of 20-40 degrees.
3. The method of claim 2 , wherein non-zero incident angle is set to approximately in the range of 10-15 degrees.
4. The method of claim 1 , wherein the incident converging X-ray beam has a converging angle approximately in the range of 2-10 degrees.
5. The method of claim 4 , wherein non-zero azimuthal angle is set to at least 45 degrees.
6. The method of claim 1 , further comprising performing another measurement by collecting only a zero order diffraction from the sample.
7. The method of claim 6 , wherein the another measurement is performed by impinging the converging X-ray beam on the sample such that the central axis forms a non-zero incidence angle relative to the horizontal plane defined by the uppermost surface of the sample, and the central axis forms a zero azimuthal angle relative to the orthogonal to the periodic structure.
8. The method of claim 1 , wherein impinging the incident converging X-ray beam comprises impinging a low energy X-ray beam having an energy of approximately 1 keV or less.
9. The method of claim 8 , wherein impinging the low energy X-ray beam comprises generating the low energy X-ray beam from a source selected from the group consisting of carbon (C), molybdenum (Mo) and Rhodium (Rh).
10. The method of claim 1 , wherein forming an incident converging X-ray beam comprises directing a low energy X-ray beam towards a toroidal multilayer monochromator.
11. The method of claim 1 , wherein collecting only a first order diffraction from the sample comprises using a two-dimensional detector to simultaneously sample scattered signal intensity of scattered X-ray beam from the sample.
12. The method of claim 11 , further comprising: estimating a shape of the periodic structure of the sample by inversion of scattering solutions relative to the sampled scattered signal intensity.
13. The method of claim 1 , wherein impinging the incident converging X-ray beam on the sample comprises impinging an X-ray beam having a wavelength less than a periodicity of the periodic structure.
14. A metrology method of measuring a sample having a periodic structure by X-ray reflectance scatterometry, the method comprising:
forming an incident converging X-ray beam having a central axis and simultaneously a plurality of incident angles and a plurality of azimuthal angles;
and performing the non-ordered steps of:
performing one measurement by impinging the converging X-ray beam on the sample such that the central axis of the converging X-ray beam forms a non-zero incidence angle relative to a horizontal plane defined by an uppermost surface of the sample, and the central axis forms a zero azimuthal angle relative to an orthogonal to the periodic structure, and collecting only a zero order diffraction from the sample; and,
performing another measurement by impinging the converging X-ray beam on the sample such that the central axis forms a non-zero incidence angle relative to the horizontal plane defined by the uppermost surface of the sample, and the central axis forms a non-zero azimuthal angle relative to the orthogonal to the periodic structure, and collecting only a first order diffraction from the sample.
15. The method of claim 14 , further comprising estimating a shape of the periodic structure of the sample by inversion of scattering solutions relative to the zero order diffraction and the first order diffraction.
16. The method of claim 14 , wherein the converging X-ray beam has a wavelength wherein λ/d<1, wherein λ is the wavelength and d is a fundamental dimension of the periodic structure.
17. The method of claim 14 , wherein non-zero incident angle is set to sine −1 (1−λ/d).
18. The method of claim 14 , wherein impinging the incident converging X-ray beam comprises impinging a low energy X-ray beam having an energy of approximately 1 keV or less.
19. The method of claim 15 , wherein forming an incident converging X-ray beam comprises directing a low energy X-ray beam towards a focusing monochromator that extends in two dimensions.
20. A metrology method of measuring a sample having a periodic structure by X-ray reflectance scatterometry, the method comprising:
forming an incident converging X-ray beam having a central axis;
impinging the converging X-ray beam on the sample such that the central axis forms a non-zero incidence angle relative to a horizontal plane defined by an uppermost surface of the sample, and the central axis forms a non-zero azimuthal angle relative to an orthogonal to the periodic structure;
performing a measurement by collecting both a zero order and a first order diffraction from the sample without order overlap.