Measurement of critical dimensions using X-ray diffraction in reflection mode
A method for X-ray analysis of a sample includes directing a beam of X-rays to impinge on an area of a periodic feature on a surface of the sample and receiving the X-rays scattered from the surface in a reflection mode so as to detect a spectrum of diffraction in the scattered X-rays as a function of azimuth. The spectrum of diffraction is analyzed in order to determine a dimension of the feature.
1. A method for X-ray analysis of a sample, comprising:
directing a beam of X-rays to impinge on an area of a periodic feature on a surface of the sample;
receiving the X-rays scattered from the surface in a reflection mode so as to detect a spectrum of diffraction in the scattered X-rays as a function of azimuth; and
analyzing the spectrum of diffraction by measuring an angular separation between side lobes in the spectrum in order to determine a dimension of the feature.
2. The method according to claim 1 , wherein directing the beam comprises collimating the beam of X-rays that is to impinge on the surface.
3. The method according to claim 1 , wherein directing the beam comprises directing the beam to impinge on the surface at a grazing angle, and wherein receiving the X-rays comprises detecting a variation in the scattered X-rays associated with total external reflection from the area of the surface.
4. The method according to claim 3 , wherein the periodic feature comprises a layer having a first critical angle formed over a substrate having a second critical angle, and wherein directing the beam comprises directing the beam at an angle between the first and second critical angles.
5. The method according to claim 4 , wherein the layer comprises an organic material, and the substrate comprises at least one of a metal, a semiconductor and a dielectric material.
6. The method according to claim 1 , wherein the feature comprises a pattern of parallel linear elements, and wherein analyzing the spectrum comprises determining a spacing between the parallel linear elements responsively to the angular separation between the side lobes.
7. The method according to claim 1 , wherein the feature comprises sidewalls, which are overlaid with a thin film, and wherein analyzing the spectrum comprises measuring a thickness of the thin film on the sidewalls.
8. The method according to claim 1 , wherein the sample comprises a semiconductor wafer.
9. The method according to claim 8 , wherein the periodic feature comprises photoresist deposited on the surface.
10. A method for X-ray analysis, comprising:
directing a beam of X-rays to impinge on an area of a planar sample that comprises a feature having sidewalls perpendicular to a plane of the sample, the sidewalls having a thin film thereon;
detecting a spectrum of the X-rays scattered from the sample due to the feature; and
analyzing the spectrum to measure a characteristic of the thin film on the sidewalls,
wherein the feature comprises a periodic pattern, and wherein analyzing the spectrum comprises analyzing a diffraction spectrum due to the periodic pattern, and
wherein the diffraction spectrum comprises multiple side lobes, and wherein analyzing the diffraction spectrum comprises observing a modulation of the side lobes as a function of angle.
11. The method according to claim 10 , wherein directing the beam comprises collimating the beam of X-rays that is to impinge on the surface.
12. The method according to claim 10 , wherein directing the beam comprises directing the beam to impinge on the surface at a grazing angle, and wherein receiving the X-rays comprises detecting a variation in the scattered X-rays associated with total external reflection from the area of the surface.
13. The method according to claim 10 , wherein observing the modulation comprises determining a thickness of the thin film responsively to an angular spacing of the side lobes.
14. The method according to claim 10 , wherein the sample comprises a semiconductor wafer.
15. The method according to claim 14 , wherein the thin film comprises a barrier layer.
16. Apparatus for X-ray analysis of a sample having a periodic feature on a surface thereof, the apparatus comprising:
an X-ray source, which is adapted to direct a beam of X-rays to impinge on an area of the surface containing the periodic feature;
a detector, which is adapted to receive the X-rays scattered from the surface in a reflection mode so as to detect a spectrum of diffraction in the scattered X-rays as a function of azimuth; and
a signal processor, which is adapted to analyze the spectrum of diffraction by measuring an angular separation between side lobes in the spectrum in order to determine a dimension of the feature.
17. The apparatus according to claim 16 , and comprising collimating optics, which are adapted to collimate the beam of X-rays that is to impinge on the sample.
18. The apparatus according to claim 16 , wherein the X-ray source is adapted to direct the beam to impinge on the surface at a grazing angle, and wherein the detector is positioned to detect a variation in the scattered X-rays associated with total external reflection from the area of the surface.
19. The apparatus according to claim 18 , wherein the periodic feature comprises a layer having a first critical angle formed over a substrate having a second critical angle, and wherein the X-ray source is adapted to direct the beam at an angle between the first and second critical angles.
20. The apparatus according to claim 19 , wherein the layer comprises an organic material, and the substrate comprises at least one of a metal, a semiconductor and a dielectric material.
21. The apparatus according to claim 16 , wherein the feature comprises a pattern of parallel linear elements, and wherein the signal processor is adapted to measure the separation between the side lobes in the spectrum in order to determine a spacing between the parallel linear elements.
22. The apparatus according to claim 16 , wherein the feature comprises sidewalls, which are overlaid with a thin film, and wherein the signal processor is adapted to measure a thickness of the thin film on the sidewalls based on the spectrum.
23. The apparatus according to claim 16 , wherein the sample comprises a semiconductor wafer.
24. The apparatus according to claim 23 , wherein the periodic feature comprises photoresist deposited on the surface.
25. Apparatus for X-ray analysis of a planar sample that includes a feature having sidewalls perpendicular to a plane of the sample, the sidewalls having a thin film thereon, the apparatus comprising:
an X-ray source, which is adapted to direct a beam of X-rays to impinge on an area of the sample containing the feature;
a detector, which is adapted to detect a spectrum of the X-rays scattered from the sample due to the feature; and
a signal processor, which is adapted to analyze the spectrum to measure a characteristic of the thin film on the sidewalls,
wherein the feature comprises a periodic pattern, and wherein the spectrum of the X-rays that is analyzed by the signal processor comprises a diffraction spectrum due to the periodic pattern, and
wherein the diffraction spectrum comprises multiple side lobes, and wherein the signal processor is adapted to measure the characteristic by observing a modulation of the side lobes as a function of angle.
26. The apparatus according to claim 25 , and comprising collimating optics, which are adapted to collimate the beam of X-rays that is to impinge on the surface.
27. The apparatus according to claim 25 , wherein the X-ray source is adapted to direct the beam to impinge on the surface at a grazing angle, and wherein the detector is positioned to detect a variation in the scattered X-rays associated with total external reflection from the area of the surface.
28. The apparatus according to claim 25 , wherein the signal processor is adapted to determine a thickness of the thin film responsively to an angular spacing of the side lobes.
29. The apparatus according to claim 25 , wherein the sample comprises a semiconductor wafer.
30. The apparatus according to claim 29 , wherein the thin film comprises a barrier layer.
31. A cluster tool for producing microelectronic devices, comprising:
a fabrication station, which is adapted to form a periodic feature on a surface of a semiconductor wafer; and
an inspection station, comprising:
an X-ray source, which is adapted to direct a beam of X-rays to impinge on an area of the surface containing the periodic feature;
a detector, which is adapted to receive the X-rays scattered from the surface in a reflection mode so as to detect a spectrum of diffraction in the scattered X-rays as a function of azimuth; and
a signal processor, which is adapted to analyze the spectrum of diffraction by measuring an angular separation between side lobes in the spectrum in order to determine a dimension of the feature.
32. The cluster tool according to claim 31 , wherein the periodic feature comprises sidewalls, which are overlaid with a thin film, and wherein the signal processor is adapted to measure a thickness of the thin film on the sidewalls based on the spectrum.
33. Apparatus for producing microelectronic devices, comprising:
a production chamber, which is adapted to receive a semiconductor wafer;
a fabrication device, which is adapted to form a periodic feature on a surface of the semiconductor wafer within the chamber;
an X-ray source, which is adapted to direct a beam of X-rays toward the semiconductor wafer in the production chamber so as to impinge on an area of the surface containing the periodic feature;
a detector, which is adapted to receive the X-rays scattered from the surface in a reflection mode so as to detect a spectrum of diffraction in the scattered X-rays as a function of azimuth; and
a signal processor, which is adapted to analyze the spectrum of diffraction by measuring an angular separation between side lobes in the spectrum in order to determine a dimension of the feature.
34. The apparatus according to claim 33 , wherein the periodic feature comprises sidewalls, which are overlaid with a thin film, and wherein the signal processor is adapted to measure a thickness of the thin film on the sidewalls based on the spectrum.