Method and apparatus for determining an objects position, topography and for imaging

• US 5,450,203 A
• Filed: 12/22/1993
• Issued: 09/12/1995
• Est. Priority Date: 12/22/1993
• Status: Expired due to Term

• Current Assignee: Martek, Inc.
• Original Assignee: Electroglas, Inc.
• Inventors: Penkethman, John A.
• Primary Examiner(s): Rosenberger, Richard A.
• Assistant Examiner(s): Eisenberg, Jason D.
• Application Number:
  US08/172,426
• Time in Patent Office: 629 Days
• Field of Search: 356/375, 356/373, 356/73.1, 356/376, 250/227.2, 250/227.26, 250/227.21, 250/227.29
• US Class Current: 356/614
• CPC Class Codes: G01B 11/00 Measuring arrangements characterised by the use of optical techniques

Abstract

Light is supplied via a optical fiber to a probe head. The light exiting the optical fiber is focused to a point by a lens. Reflected light from an object at or near the focal point is reflected back through the lens and then focused to the source optical fiber or a second optical fiber located next the source optical fiber. The return signal is then detected in a detector module. By noting the characteristics of the response curve as the object is moved back and forth relative to the probe head, the position of the object can be determined. By performing this procedure over several points, a detailed topography map can be created. Additionally, the probe head can be scanned at a constant distance from the surface to produce an image of the surface as the response signal varies according to the surface'"'"'s reflectivity. The microprobe can be used, for example, to find the position of probe tips on a wafer prober, to determine the topography of the surface of the wafer, and to find the position of the wafer edge.

Claims

1. A method of determining a position of a point on an object comprising the steps of:

providing radiation;

focusing said radiation to a focal point, said focal point being in a focal plane;

focusing reflected radiation from said object to a first site;

measuring a first intensity of said reflected radiation incident upon said first site;

determining said position of said point on said object in three dimensions relative to a reference position based upon said first intensity.

2. The method as described in claim 1, wherein said radiation is focused by a first lens and said reflected radiation is focused by said first lens.

3. The method as described in claim 2, wherein said radiation is provided from a source through an optical fiber, said source providing said radiation to a first end of said optical fiber, said radiation transmitted through said optical fiber and exiting a second end of said optical fiber located at said first site, and wherein said reflected radiation is focused back to said second end of said optical fiber, said reflected radiation transmitted through said optical fiber and exiting said first end, said reflected radiation directed therefrom to a detector.

4. The method as described in claim 3 further comprising providing a plurality of optical fibers, said method further comprising selecting at least one of said plurality of optical fibers to provide said radiation and selecting at least one of said plurality of optical fibers to transmit said reflected radiation.

5. The method as described in claim 1, wherein said first intensity is measured at a plurality of locations of said object relative to said focal point, wherein said plurality of locations are substantially in a line, said line substantially perpendicular to said focal plane.

6. The method as described in claim 1, wherein said method is used to find said position of a plurality of points on said object to provide a topographical map of a surface of said object.

7. The method as described in claim 6 further comprising the steps of:

passing said surface through said radiation at a constant distance relative to said focal point;

measuring a second intensity of reflected radiation of said radiation from said surface in said detector, to produce an image of said surface.

8. The method as described in claim 1 wherein said object is a probe tip, and wherein said reference position is known relative to a region of a substrate to be tested.

9. A method of determining a position of a point on an object Comprising the steps of:

providing radiation;

focusing said radiation to a focal point, said focal point being in a focal plane;

focusing reflected radiation from said object to a first site;

measuring a first intensity of said reflected radiation incident upon said first site;

determining said position of said point on said object relative to a reference position based upon said first intensity,

wherein said object is a probe tip, and wherein said reference position is known relative to a region of a substrate to be tested.

10. A method of determining a position of a point on an object Comprising the steps of:

providing radiation from a first site;

focusing said radiation to a focal point, said focal point being in a focal plane;

focusing reflected radiation from said object to a second site proximate said first site;

measuring a first intensity of said reflected radiation focused to said second site;

determining said position of said point on said object relative to a reference position based upon said first intensity,

wherein said position is determined in three dimensions.

11. A method of determining a position of a point on an object comprising the steps of:

providing radiation from a first site;

focusing said radiation to a focal point, said focal point being in a focal plane;

focusing reflected radiation from said object to a second site proximate said first site;

measuring a first intensity of said reflected radiation focused to said second site;

determining said position of said point on said object relative to a reference position based upon said first intensity,

wherein said object is a probe tip, and wherein said reference position is known relative to a region of a substrate to be tested.

12. A method of determining a position of a point on an object comprising the steps of:

providing radiation from a first site;

focusing said radiation to a focal point, said focal point being in a focal plane;

focusing reflected radiation from said object to a second site proximate said first site;

measuring a first intensity of said reflected radiation focused to said second site;

determining said position of said point on said object relative to a reference position based upon said first intensity,

wherein said reference position is known relative to a null position which returns a null point in said first intensity, and wherein said position of said point on said object is determined by detecting said null point in said first intensity.

13. A method of determining a position of a point On an object comprising the steps of:

providing radiation from a first site;

focusing said radiation to a focal point, said focal point being in a focal plane;

focusing reflected radiation from said object to a second site proximate said first site;

measuring a first intensity of said reflected radiation focused to said second site;

determining said position of said point on said object relative to a reference position based upon said first intensity;

focusing said reflected radiation to said first site;

measuring a second intensity of said reflected radiation focused to said first site; and

,

determining said position of said point on said object relative to said reference position based upon said second intensity.

14. A method of determining a position of a point on an object comprising the steps of;

providing radiation from a first site, wherein said radiation is provided from a source through a first optical fiber, said source illuminating a first end of said first optical fiber, said radiation exiting a second end of said first optical fiber, said second end of said first optical fiber being disposed at said first site;

focusing said radiation to a focal point, said focal point being in a focal plane;

focusing reflected radiation from said object to a second site proximate said first site, said second site disposed such that the optical paths of said radiation and said reflected radiation are not confocal, wherein said reflected radiation is focused onto a second end of a second optical fiber at said second site, said reflected radiation focused onto said second end of said second optical fiber being transmitted through said second optical fiber to a detector;

measuring a first intensity of said reflected radiation focused to said second site;

determining said position of said point on said object relative to a reference position based upon said first intensity;

focusing said reflected radiation to said second end of said first optical fiber at said first site;

measuring a second intensity of said reflected radiation focused to said first site; and

,

determining said position of said point on said object relative to said reference position based upon said second intensity.

15. The method as described in claim 14 comprising providing a plurality of said first optical fibers and a plurality of said second optical fibers, said method further comprising the steps of selecting at least one of said first optical fibers to provide said radiation and selecting at least one of said second optical fibers to measure said first intensity of said reflected radiation.

16. An apparatus for determining a position of a point on an object comprising:

a radiation source;

a optical fiber having a first and a second end, said first end disposed to receive radiation from said radiation source;

means for focusing radiation exiting said second end of said optical fiber disposed proximate said second end of said optical fiber, said means for focusing disposed to focus reflected radiation from said object to said second end; and

,

means for detecting said reflected radiation exiting said second end of said optical fiber, wherein said apparatus is coupled to a semiconductor wafer prober, and wherein said apparatus is positioned to determine the position of an object selected from the group consisting of a probe tip and a point on a surface of said semiconductor wafer.

17. The apparatus as described in claim 16 further comprising:

a plurality of said optical fibers; and

,

means for selecting at least one of said optical fibers to provide said radiation and means for selecting at least one of said optical fibers to provide said reflected radiation to said means for detecting.

18. An apparatus for determining a position of a point on an object comprising:

a radiation source providing radiation from a first site;

means for focusing said radiation disposed proximate said first site, said means for focusing disposed to focus reflected radiation from said object to a second site proximate said first site; and

,

means for detecting said reflected radiation focused to said second site,

wherein said apparatus is coupled to a semiconductor wafer prober, and wherein said apparatus is positioned to determine a position of an object selected from the group consisting of a point on a surface Of said semiconductor wafer and a probe tip.

19. An apparatus for determining a position of a point on an object comprising:

a radiation source providing radiation from a first site;

means for focusing said radiation disposed proximate said first site, said means for focusing disposed to focus reflected ;

radiation from said object to a second site proximate said first site and,

means for detecting said reflected radiation focused to said second site,

wherein said apparatus further comprises means for encoding said radiation from each of said first optical fibers and wherein said apparatus further comprises means for decoding said reflected radiation to determine which of said first optical fibers provided said radiation.

20. An apparatus for determining a position of a point on an object comprising:

a radiation source providing radiation from a first site;

means for focusing said radiation disposed proximate said first site, said means for focusing disposed to focus reflected radiation from said object to a second site proximate said first site; and

,

means for detecting said reflected radiation focused to said second site,

wherein said means for focusing further focuses said reflected radiation to said first site, said apparatus further comprising means for detecting said reflected radiation focused to said first site.

21. A method of determining a position of a point on an object comprising the steps of:

providing radiation from a first site;

focusing said radiation to a focal point, said focal point being in a focal plane;

focusing reflected radiation from said object to a second site proximate said first site, said second site disposed such that the optical paths of said radiation and said reflected radiation are not confocal;

measuring a first intensity of said reflected radiation focused to said second site;

determining said position of said point on said object relative to a reference position based upon said first intensity, wherein said position is determined in three dimensions.

22. A method of determining a position of a point on an object comprising the steps of:

providing radiation from a first site;

focusing said radiation to a focal point, said focal point being in a focal plane;

focusing reflected radiation from said object to a second site proximate said first site, said second site disposed such that the optical paths of said radiation and said reflected radiation are not confocal;

measuring a first intensity of said reflected radiation focused to said second site;

determining said position of said point on said object relative to a reference position based upon said first intensity wherein said object is a probe tip, and wherein said reference position is known relative to a region of a substrate to be tested.

23. An apparatus for determining a position of a point on an object comprising:

a plurality of radiation sources providing radiation via a plurality of first optical fibers from a plurality of first sites;

means for encoding said radiation from each of said first optical fibers;

means for focusing said radiation disposed proximate said first sites, said means for focusing disposed to focus reflected radiation from said object to a plurality of second sites proximate said first sites, said second sites disposed such that the optical paths of said radiation and said reflected radiation are not confocal;

means for detecting said reflected radiation focused to said second sites, said second sites coupled to said means for detecting via a plurality of second optical fibers;

means for decoding said reflected radiation to determine which of said first optical fibers provided said radiation.

24. An apparatus for determining a position of a point on an object comprising:

a radiation source providing radiation from a first site;

means for focusing said radiation disposed proximate said first site, said means for focusing disposed to focus reflected radiation from said object to said first sight and to a second site proximate said first site, said second site disposed such that the optical paths of said radiation and said reflected radiation focused to said second site are not confocal;

means for detecting said reflected radiation focused to said first site; and

means for detecting said reflected radiation focused to said second site.