System and method to determine depth for optical wafer inspection

Patent metadata

Field	Value
Publication number	US-9989479-B1
Application number	US-201615180641-A
Country	US
Kind code	B1
Filing date	Jun 13, 2016
Priority date	Mar 15, 2013
Publication date	Jun 5, 2018
Grant date	Jun 5, 2018

Abstract

A computer-based apparatus for adjusting an auto-focus in a wafer inspection system, including: a wafer adjustment system; and an electronic feedback loop system configured to compare an intensity of a first light beam rotating in a first spiral about a first central axis, and when the intensity is less than a preselected threshold, adjust, using the wafer adjustment system, a position of the wafer until the intensity reaches the preselected threshold.

First claim

What is claimed is:

1. A computer-based method for inspecting a wafer, comprising:
storing, in a memory element for at least one computer, non-transitory computer readable instructions;
detecting, using a detector, a first light beam rotating in a first spiral about a first central axis; and,
executing, using a processor for the at least one computer, the non-transitory computer readable instructions to:
generate, using the detected first light beam, an image consisting of only one single shape;
determine an orientation of the only one single shape and a size of the only one single shape; and,
calculate a depth of a defect within the wafer according to the orientation or the size of the only single shape.

2. The computer-based method of claim 1 , further comprising:
illuminating, using a light source, the wafer with a second light beam rotating in a second spiral about a second central axis, wherein the first light beam includes the second light beam scattered by or reflected from the wafer.

3. The computer-based method of claim 1 , further comprising:
illuminating, using a light source, the wafer with light free of a spiral wavefront or orbital angular momentum; and,
filtering, using a phase and transmission filter, the light scattered by or reflected from the wafer to generate the first light beam.

4. The computer-based method of claim 1 , wherein:
the first light beam includes orbital angular momentum.

5. The computer-based method of claim 1 , wherein:
the only one single shape is a disc; and,
determining the size of the only one single shape includes determining a diameter of the disk.

6. The computer-based method of claim 1 , wherein determining the size of the only one single shape includes determining a rotational position of the only one single shape with respect to a point within the only one single shape.

7. The computer-based method of claim 1 , further comprising executing, using the processor, the non-transitory computer readable instructions to:
deconvolute, prior to determining the orientation, the image according to a predetermined orientation; or,
amplify a signal for the only one single shape when the only one single shape matches a predetermined orientation, or attenuate a signal for the only one single shape when the only one single shape does not match a predetermined orientation.

8. The computer-based method for inspecting a wafer of claim 1 , wherein calculating the depth of the defect includes calculating the depth of the defect from a surface of the wafer.

9. The computer-based method for inspecting a wafer of claim 1 , wherein calculating the depth of the defect includes calculating the depth of a defect extending to a surface of the wafer.

10. The computer-based method for inspecting a wafer of claim 1 , wherein calculating the depth of the defect includes calculating the depth of a defect that does not extend to a surface of the wafer.

11. The computer-based method for inspecting a wafer of claim 1 , wherein:
the wafer includes a silicon layer and a layer of silicon dioxide overlaying the silicon layer;
a surface of the wafer is formed by the silicon dioxide layer; and,
the surface of the wafer is not in contact with the silicon layer.

12. The computer-based method for inspecting a wafer of claim 1 , wherein:
the wafer includes a plurality of layers, each layer including a respective material;
the defect is within at least one layer included in the plurality of layers; and,
a surface of the wafer is formed by a first layer included in the plurality of layers; and,
wherein:
at least one layer in the plurality of layers includes separate segments of the respective material; or,
at least one layer in the plurality of layers includes a second material different from the respective material.

13. The computer-based method for inspecting a wafer, of claim 1 , further comprising:
generating the only one single shape in the image using a phase and transmission filter inserted in the first light beam.

14. The computer-based method for inspecting a wafer, of claim 1 , further comprising:
comparing, using an electronic feedback loop system, an intensity of a first light beam rotating in a first spiral about a first central axis; and,
when the intensity is less than a preselected threshold, adjusting, using a wafer adjustment system, a position of the wafer until the intensity reaches the preselected threshold.

15. The computer-based method for inspecting a wafer, of claim 1 , further comprising:
optimizing a linear combination of Laguerre polynomials such that the slope of a rotation line in a modal plane is greater than 2.0, wherein:
the slope of the rotational line is defined by a change in values for respective energy numbers divided by a change in values for respective azimuthal numbers for a plurality of Gauss-Laguerre Eigen modes;
the energy numbers form a first axis in a modal plane; and
the azimuthal numbers form a second axis, orthogonal to the first axis, in the modal plane.

16. A computer-based apparatus for inspecting a wafer, comprising:
at least one computer including a processor and a memory element configured to store non-transitory computer readable instructions; and,
a detector arranged to detect a first light beam rotating in a first spiral about a first central axis, wherein:
the processor is configured to execute the non-transitory computer readable instructions to:
generate, using the detected first light beam, an image consisting of only one single shape;
determine an orientation of the only one single shape and a size of the only one single shape; and,
calculate a depth of a defect within the wafer according to the orientation or the size of the only one single shape.

17. The computer-based apparatus of claim 16 , further comprising:
a light source arranged to emit light free of a spiral wavefront or orbital angular momentum; and,
a phase and transmission filter arranged to filter the light to generate a second light beam, rotating in a second spiral about a second central axis, to illuminate the wafer, wherein:
the first light beam includes the second light beam scattered by or reflected from the wafer.

18. The computer-based apparatus of claim 16 , further comprising:
a light source arranged to illuminate the wafer with light free of a spiral wavefront or orbital angular momentum; and,
a phase and transmission filter arranged to filter the light scattered by or reflected from the wafer to generate the first light beam.

19. The computer-based apparatus of claim 16 , wherein:
the only one single shape is a disc; and,
determining the size of the only one single shape includes determining a diameter of the disk.

20. The computer-based apparatus of claim 16 , wherein determining the size of the only one single shape includes determining a rotational position of the only one single shape with respect to a point within the only one single shape.

21. The computer-based apparatus of claim 16 , wherein the processor is configured to execute the non-transitory computer readable instructions to:
deconvolute, prior to determining the first orientation, the image according to a predetermined orientation; or,
amplify a signal for the only one single shape when the only one single shape matches a predetermined orientation, or attenuate a signal for the only one single shape when the only one single shape does not match a predetermined orientation.

22. The computer-based

Assignees

• Kla Tencor Corp

Inventors

• Kolchin Pavel
• Haurylau Mikhail
• Danen Robert

Classifications

• H04N23/56

  provided with illuminating means · CPC title

• G01N21/8851

  Scan or image signal processing specially adapted therefor, e.g. for scan signal adjustment, for detecting different kinds of defects, for compensating for structures, markings, edges (G01N21/8806 and G01N21/93 - G01N21/95692 take precedence; optical measurement of dimensions G01B11/00; optical scanning G02B26/10; image transformation G06T3/00; computerised image enhancement G06T5/00; image processing per se for flaw detection G06T7/0002) · CPC title

• G06T7/0012

  Biomedical image inspection · CPC title

• G02B5/28

  Interference filters · CPC title

• G06T7/70

  Determining position or orientation of objects or cameras (camera calibration G06T7/80) · CPC title