Differential numerical aperture methods and device

• US 20020039184A1
• Filed: 10/02/2001
• Published: 04/04/2002
• Est. Priority Date: 10/03/2000
• Status: Active Grant

• Current Assignee: Onto Innovation Inc.
• Original Assignee: Accent Optical Technologies, Inc. (Onto Innovation Inc.)
• Inventors: Sandusky, John V.
• Granted Patent: US 6,750,968 B2
• Time in Patent Office: Days
• US Class Current: 356/369
• CPC Class Codes: G01J 3/02 Details
• CPC Class Codes: G01J 3/0229 using masks, aperture plates, spatial light modulators or spatial filters, e.g. reflective filters
• CPC Class Codes: G01N 2021/214 Variangle incidence arrangement
• CPC Class Codes: G01N 21/47 Scattering, i.e. diffuse reflection G01N21/25, G01N21/41 take precedence G01N21/55 takes precedence

Abstract

Devices and methods for differential numerical aperture analysis of samples, utilizing angle-of-incidence measurements resulting from variable illumination or observation numerical apertures, or both. Metrology applications are provided, and more particularly including scatterometer, ellipsometer and similar analysis methods, including bi-directional reflectance or transmission distribution function measurement. The provided devices and methods enable analysis of critical dimensions of samples utilizing a minimum of moving parts, with the range of striking or scattering angles varied by means of a variable numerical aperture or apertures.

Claims

1. An apparatus for determining parameters of a sample comprising:

a source for generating a beam of light;

a variable illumination numerical aperture component, variable over a numerical aperture range while obtaining data for determining parameters, the varying numerical aperture thereby varying the range of angles at which illuminating rays strike the sample;

a variable observation numerical aperture component, variable over a numerical aperture range while obtaining data for determining parameters, the varying numerical aperture thereby varying the range of angles at which scattered rays from the sample are accepted; and

a first detection system positioned to receive and characterize the light accepted by the variable observation numerical aperture component.

2. The apparatus of claim 1, further comprising a beam splitter positioned to direct the beam of light generated by the source to the sample.

3. The apparatus of claim 1, further comprising a lens positioned such that the lens focuses the illuminating rays striking the sample and collects scattered rays from the sample.

4. The apparatus of claim 1, further comprising:

a first component for polarizing light positioned such that the component polarizes light striking the sample; and

a second component for polarizing light positioned such that the component polarizes light scattered from the sample prior to receipt and characterization by the first detection system.

5. The apparatus of claim 4, wherein the first component for polarizing light and the second component for polarizing light comprise elements selected from the group consisting of a polarizer, a wave plate, an electrooptic modulator, a photoelastic modulator and a liquid crystal.

6. The apparatus of claim 1, further comprising a second detection system positioned to receive and characterize a first portion of the light subsequent to the variable illumination numerical aperture but prior to striking the sample.

7. The apparatus of claim 6, further comprising a beam splitter positioned to direct the first portion of the light to the second detection system and a second portion of the light to the sample.

8. The apparatus of claim 1, wherein the variable illumination numerical aperture comprises a member selected from the group consisting of an aperture with an iris, a zoom lens assembly, a variable beam expander, a variable aperture stop magnification imaging assembly, a spatial Fourier transform of the aperture stop assembly and a combination of the foregoing.

9. The apparatus of claim 8, wherein the iris is of any shape.

10. The apparatus of claim 1, wherein the first detection system comprises a member selected from the group consisting of a photodetector and a spectrometer.

11. The apparatus of claim 1, wherein the first detection system comprises a computer-compatible output for recording data relating to receipt and characterization of light.

12. The apparatus of claim 1, further comprising a processor for controlling the numerical aperture of the variable illumination numerical aperture component and the aperture of the variable observation numerical aperture component.

13. The apparatus of claim 1, wherein the numerical aperture of the variable illumination numerical aperture component is variable over a numerical aperture range from 0 to about 1.

15. The apparatus of claim 14, further comprising a beam splitter positioned to direct the beam of light generated by the source to the sample.

16. The apparatus of claim 14, wherein the first detection system comprises a detector array for detecting the light accepted by the observation aperture component over the range of angles accepted by the observation aperture component.

17. The apparatus of claim 14, further comprising:

a first component for polarizing light positioned such that the component polarizes light striking the sample; and

a second component for polarizing light positioned such that the component polarizes light scattered from the sample prior to receipt and characterization by the first detection system.

18. The apparatus of claim 17, wherein the first component for polarizing light and the second component for polarizing light comprise elements are selected from the group consisting of a polarizer and a wave plate.

19. The apparatus of claim 14, further comprising a second detection system positioned to receive and characterize a first portion of the light subsequent to the variable illumination numerical aperture component but prior to striking the sample.

20. The apparatus of claim 19, further comprising a beam splitter positioned to direct the first portion of the light to the second detection system and a second portion of the light to the sample.

21. The apparatus of claim 14, wherein the variable illumination numerical aperture component comprises a member selected from the group consisting of an aperture with an iris, a zoom lens assembly, a variable beam expander, a variable aperture stop magnification imaging assembly, a spatial Fourier transform of the aperture stop assembly and a combination of the foregoing.

22. The apparatus of claim 14, wherein the first detection system comprises a member selected from the group consisting of a photodetector and a spectrometer.

23. The apparatus of claim 14, wherein the first detection system comprises a computer-compatible output for recording data relating to receipt and characterization of light.

24. The apparatus of claim 14, further comprising a processor for controlling the numerical aperture of the variable illumination numerical aperture component.

26. The apparatus of claim 25, further comprising a beam splitter positioned to direct the beam of light generated by the source to the sample.

27. The apparatus of claim 25, further comprising a lens positioned such that the lens focuses the illuminating rays striking the sample and collects scattered rays from the sample.

28. The apparatus of claim 25, further comprising:

a first component for polarizing light positioned such that the component polarizes light striking the sample; and

a second component for polarizing light positioned such that the component polarizes light scattered from the sample prior to receipt and characterization by the first detection system.

29. The apparatus of claim 28, wherein the first component for polarizing light and the second component for polarizing light comprise elements are selected from the group consisting of a polarizer, a wave plate, an electrooptic modulator, a photoelastic modulator and a liquid crystal.

30. The apparatus of claim 25, further comprising a second detection system positioned to receive and characterize a first portion of the light subsequent to the illumination aperture component but prior to striking the sample.

31. The apparatus of claim 30, further comprising a beam splitter positioned to direct the first portion of the light to the second detection system and a second portion of the light to the sample.

32. The apparatus of claim 25, wherein the first detection system comprises a member selected from the group consisting of a photodetector and a spectrometer.

33. The apparatus of claim 25, wherein the first detection system comprises a computer-compatible output for recording data relating to receipt and characterization of light.

34. The apparatus of claim 14, further comprising a processor for controlling the numerical aperture of the variable observation numerical aperture component.

36. The method of claim 35, wherein the step of varying at least one parameter comprises varying both the range of angles of incidence of the beam of light to the sample and the range of angles of detected scatter from the sample.

37. The method of claim 36, where the range of angles of incidence of the beam of light to the sample is varied by means of a first variable numerical aperture and the range of angles of detected scatter from the sample is varied by means of a second variable numerical aperture.

38. The method of claim 35, further comprising the steps of:

polarizing the light striking the sample; and

polarizing the light scattered from the sample.

39. The method of claim 35, wherein the at least one variable numerical aperture comprises a member selected from the group consisting of an aperture with an iris, a zoom lens assembly, a variable beam expander, a variable aperture stop magnification imaging assembly, a spatial Fourier transform of the aperture stop assembly and a combination of the foregoing.

40. The method of claim 35, wherein detecting and characterizing comprises use of a device selected from the group consisting of a photodetector and a spectrometer.

41. The method of claim 35, wherein detecting and characterizing comprises a computer-compatible output for recording data relating to receipt and characterization of light.

14. An apparatus for determining parameters of a sample comprising:

a source for generating a beam of light;

a variable illumination numerical aperture component for varying the numerical aperture over a numerical aperture range while obtaining data for determining parameters, thereby varying the range of angles at which illuminating rays strike the sample;

an observation aperture component, accepting scattered rays from the sample at a fixed range of angles; and

a first detection system positioned to receive and characterize the light accepted by the observation aperture component.

25. An apparatus for determining parameters of a sample comprising:

a source for generating a beam of light;

an illumination aperture component, determining the range of angles at which illuminating rays strike the sample;

a variable observation numerical aperture component for varying the numerical aperture over an incremental numerical aperture range while obtaining data for determining parameters, thereby varying the range of angles at which scattered rays from the sample are accepted; and

a first detection system positioned to receive and characterize the light accepted by the variable observation aperture component.

35. A method for determining parameters of a sample comprising the steps of:

generating a beam of light;

focusing the beam of light on the sample;

varying at least one parameter selected from the group consisting of the range of angles of incidence of the beam of light to the sample and the range of angles of detected scatter from the sample by means of at least one variable numerical aperture; and

detecting and characterizing the scattered light.