X-ray reflectivity system with variable spot

• US 7,139,365 B1
• Filed: 12/28/2004
• Issued: 11/21/2006
• Est. Priority Date: 12/28/2004
• Status: Expired due to Fees

• Current Assignee: Kla-Tencor Technologies Corporation (KLA Corporation)
• Original Assignee: Kla-Tencor Technologies Corporation (KLA Corporation)
• Inventors: Janik, Gary R.
• Primary Examiner(s): Glick, Edward J.
• Assistant Examiner(s): Yun, Jurie
• Application Number:
  US11/025,472
• Time in Patent Office: 693 Days
• Field of Search: 378 70- 90, 378/119, 378121-138, 378/143, 378/145, 378/146
• US Class Current: 378/70
• CPC Class Codes: G01N 23/20 by using diffraction of the radiation by the materials, e.g. for investigating crystal structure; by using scattering of the radiation by the materials, e.g. for investigating non-crystalline materials; by using reflection of the radiation by the materials

Abstract

Thin film thickness measurement accuracy in x-ray reflectometry systems can be enhanced by minimizing scattering and beam spreading effects. A reflectometry system can include an x-ray tube that can produce an x-ray beam having any cross-sectional shape by scanning an electron beam in an appropriate pattern over a target in an x-ray tube. For example, the electron beam can be scanned over the target in a pattern having a non-unitary aspect ratio, so that the x-ray beam is generated from a source region having a non-unitary aspect ratio. The elongation allows the beam direction dimension to be substantially reduced, without causing overheating of the target. By blocking portions of the x-ray beam focused on the thin film and generating reflectivity curves in increments, the effects of scattering can be minimized.

Claims

1. An x-ray reflectometry system for performing reflectometry on a test sample, the x-ray reflectometry system comprising:

an x-ray tube for generating an x-ray beam;

beam focusing optics for focusing the x-ray beam onto a measurement location on the test sample; and

a sensor for measuring x-rays reflected from the test sample,

wherein the x-ray tube comprises;

a target;

an electron source for generating an electron beam; and

a scanning mechanism for scanning the electron beam across a source region of the target to cause the source region to emit the x-ray beam, wherein the source region is larger than a cross-section of the electron beam.

2. The x-ray reflectometry system of claim 1, wherein the source region has a non-unitary aspect ratio, and

wherein a long dimension of the source region is positioned substantially perpendicular to a direction of the x-ray beam.

3. The x-ray reflectometry system of claim 1, wherein the scanning mechanism comprises a beam deflection element.

4. The x-ray reflectometry system of claim 1, wherein the scanning mechanism comprises a positioning mechanism for adjusting a relative position between the electron source and the target.

5. The x-ray reflectometry system of claim 1, wherein the x-ray tube further comprises a beam shaping element for adjusting a cross-sectional shape of the electron beam before the electron beam is scanned across the source region of the target.

6. The x-ray reflectometry system of claim 1, wherein the sensor comprises a sensor array for measuring intensities of the x-rays reflected from the test sample over a plurality of measurement locations on the sensor array.

7. The x-ray reflectometry system of claim 6, wherein the x-ray beam consists of a plurality of source x-rays,

a first gate for blocking a first group of the plurality of source x-rays without impeding a second group of the plurality of source x-rays, the second group of the plurality of source x-rays forming a plurality of incident angles with the measurement location.

8. The x-ray reflectometry system of claim 7, further comprising a second gate for blocking x-rays scattered by the first gate without impeding the second group of the plurality of x-rays.

9. The x-ray reflectometry system of claim 1, further comprising a positional adjustment mechanism for adjusting an angle of incidence between the x-ray beam and the measurement location.

10. The x-ray reflectometry system of claim 9, wherein the positional adjustment mechanism comprises a goniometer.

11. The x-ray reflectometry system of claim 9, wherein the x-ray tube and focusing optic generate the x-ray beam with a narrow cone.

12. The x-ray reflectometry system of claim 9, wherein the sensor comprises a single element detector for measuring a total intensity of the x-rays reflected from the test sample.

13. The x-ray reflectometry system of claim 9, wherein the x-ray source spot area is set to automatically change with the position of the x-ray source and x-ray focusing optic.

14. The x-ray reflectometry system of claim 9, wherein the e-beam power is set to automatically change with the position of the x-ray source and x-ray focusing optic.

15. A method for taking an x-ray reflectometry measurement, the method comprising:

generating a first x-ray beam by scanning a first electron beam across a first source region of a target to cause the first source region to emit the first x-ray beam;

focusing the first x-ray beam onto a measurement location on a test sample; and

measuring a first set of x-rays reflected from the measurement location.

16. The method of claim 15, wherein the first source region has a non-unitary aspect ratio, and

wherein a long dimension of the first source region is substantially perpendicular to a direction of the first x-ray beam.

17. The method of claim 15, wherein measuring the first set of x-rays reflected from the measurement location comprises:

measuring an intensity at each of a set of detection locations on a sensor array; and

correlating the intensity at each of the set of detection locations with an angle of incidence to generate a reflectivity curve.

18. The method of claim 15, further comprising:

generating a second x-ray beam by scanning a second electron beam across a second source region of the target to cause the second source region to emit the second x-ray beam;

focusing the second x-ray beam onto the measurement location on the test sample; and

measuring a second set of x-rays reflected from the measurement location.

19. The method of claim 18, wherein the second source region has a different shape than the first source region.

20. The method of claim 19, wherein measuring the first set of x-rays reflected from the measurement location comprises measuring a first total intensity of the first set of x-rays and correlating the first total intensity with a first angle of incidence between the first x-ray beam and the measurement location, and

wherein measuring the second set of x-rays reflected from the measurement location comprises measuring a second total intensity of the second set of x-rays and correlating the second total intensity with a second angle of incidence between the second x-ray beam and the measurement location.

21. The method of claim 20, wherein the second angle of incidence is greater than the first angle of incidence, and

wherein a power of the second electron beam is greater than a power of the first electron beam.