Optical inspection module and method for detecting particles and defects on substrates in integrated process tools

• US 5,909,276 A
• Filed: 03/30/1998
• Issued: 06/01/1999
• Est. Priority Date: 03/31/1997
• Status: Expired due to Term

• Current Assignee: Nanometrics Incorporated (Onto Innovation Inc.)
• Original Assignee: Microtherm Inc.
• Inventors: Kinney, Patrick D., Rao, Nagaraja P.
• Primary Examiner(s): Kim, Robert
• Assistant Examiner(s): Ratliff, Reginald A.
• Application Number:
  US09/050,267
• Time in Patent Office: 428 Days
• Field of Search: 356/237, 356/430, 356/335, 356/336, 356/337, 356/338, 356/342
• US Class Current: 356/237.2
• CPC Class Codes: G01N 21/94 Investigating contamination, e.g. dust G01N21/85 takes precedence
• CPC Class Codes: G01N 21/9501 Semiconductor wafers manufacturing processes per se of semiconductor devices implementing a measuring step H01L22/10
• CPC Class Codes: H01L 22/12 for structural parameters, e.g. thickness, line width, refractive index, temperature, warp, bond strength, defects, optical inspection, electrical measurement of structural dimensions, metallurgic measurement of diffusions electrical measurement of diffusions H01L22/14

Abstract

An optical inspection module detects defects on an active surface of a substrate in an integrated process tool system. The optical inspection module includes an enclosure, a substrate holder, a light source, a light beam path, a lens and a photodetector array. The light source has a light beam port. The light beam path extends from the light beam port to the substrate holder and has a grazing angle of incidence with respect to the active surface of the substrate. The light beam path illuminates substantially the entire active surface. The lens is oriented to collect non-secularly reflected light scattered from the light beam path by any defects on the active surface. The photodetector array has a plurality of pixels which are positioned within a focal plane of the lens. Each pixel corresponds to an area on the active surface, and the plurality of pixels together form a field of view that covers substantially the entire active surface.

Claims

1. An optical inspection cluster tool module for detecting particles on an active surface of a substrate in a cluster tool system, the optical inspection cluster tool module comprising:

an enclosure having a material transport aperture which is adapted to receive a common material transport arm;

a substrate holding position within the enclosure;

a light source having a light beam port;

a light beam path extending from the light beam port to the substrate holding position and having a grazing angle of incidence with respect to the active surface of the substrate, wherein the light beam path illuminates substantially the entire active surface;

a lens which is oriented to collect non-specularly reflected light that is scattered from the light beam path by any defects on the active surface, the lens having a focal plane; and

a photodetector array having a plurality of pixels which are positioned within the focal plane of the lens, wherein each pixel corresponds to an area on the active surface and the plurality of pixels together form a field of view that covers substantially the entire active surface.

2. The optical inspection cluster tool module of claim 1 and further comprising a substrate holder secured within the enclosure at the substrate holding position.

3. The optical inspection cluster tool module of claim 1 wherein the optical inspection cluster tool module is free of mechanically-moving components within the enclosure.

4. The optical inspection cluster tool module of claim 1 wherein the light beam port comprises a broadband collimated, circular light beam port and the light beam path comprises a circular-to-rectangular beam shape converter.

5. The optical inspection cluster tool module of claim 1 wherein the light source comprises a monochromatic laser light source.

6. The optical inspection cluster tool module of claim 1 wherein the lens and the photodetector array together comprise a charge coupled device ("CCD") array camera.

7. The optical inspection cluster tool module of claim 6 wherein CCD array camera comprises a slow-scan, cooled CCD array camera.

8. The optical inspection cluster tool module of claim 1 wherein the lens and the photodetector array together comprise a video camera.

9. The optical inspection cluster tool module of claim 1 wherein the enclosure is light-proof.

10. The optical inspection cluster tool module of claim 1 wherein the enclosure comprises a light-absorbing internal surface.

11. The optical inspection cluster tool module of claim 1 and further comprising a beam trapping device which is oriented relative to the light beam path and the substrate holding position for trapping specularly reflected light from the active surface.

12. The optical inspection cluster tool module of claim 1 and further comprising means coupled to the photodetector array for measuring an intensity of the collected non-specular light within the focal plane at each of the plurality of pixels and for identifying presence of the defects as a function of the measured intensity.

13. The optical inspection cluster tool module of claim 1 and further comprising means coupled to the photodetector array for measuring an intensity of the collected non-specularly reflected light within the focal plane within at least one of the plurality of pixels and for measuring surface roughness based on the measured intensity.

14. The optical inspection cluster tool module of claim 1 and further comprising a light intensity controller coupled to the light source.

15. The optical inspection cluster tool module of claim 1 wherein the photodetector array has an output indicating light intensity applied within each of the plurality of pixels and wherein the module further comprises a computer controller coupled to the output.

16. The optical inspection cluster tool module of claim 1 wherein the enclosure comprises a vacuum chamber.

17. An integrated cluster tool system for processing a substrate having an active surface, the system comprising:

a loading module having a substrate loading input;

a plurality of substrate processing modules;

a substrate inspection module comprising;

an enclosure having a substrate loading aperture;

a substrate holding position within the enclosure;

a light source having a light beam port;

a light beam path extending from the light beam port to the substrate holding position and having a grazing angle of incidence with respect to the active surface when the substrate is held in the substrate holding position, wherein the light beam path illuminates substantially the entire active surface;

a lens which is oriented relative to the substrate holding position to collect non-specular light scattered from the light beam path by any defects, including particles, on the active surface, the lens having a focal plane; and

a photodetector array having a plurality of pixels which are positioned within the focal plane of the lens, wherein each pixel corresponds to a unit area on the active surface and the plurality of pixels together have a field of view that covers substantially the entire active surface; and

a common substrate transport arm which interfaces with the substrate loading input, each of the substrate processing modules and the substrate inspection module along a substrate travel path.

18. The integrated cluster tool system of claim 17 wherein the plurality of substrate processing modules comprises a substrate scrubbing module, a substrate rinsing module and a substrate drying module.

19. The integrated cluster tool system of claim 17 wherein the plurality of substrate processing modules further comprises a substrate polishing module.

20. The integrated cluster tool system of claim 17 wherein the substrate inspection module is free of mechanically-moving components within the enclosure.

21. The integrated cluster tool system of claim 17 wherein the common substrate transport arm comprises a substrate holder having a retracted position and an extended position, wherein the substrate holder is external to the enclosure when the common substrate transport arm is in the retracted position and wherein the substrate holder is internal to the enclosure and in the substrate holding position when the common substrate transport arm is in the extended position.

22. The integrated cluster tool system of claim 21 and further comprising:

inspection controller means coupled to the light source, the photodetector array and the common substrate transport arm for controlling the light source to illuminate the active surface through the light beam path and for measuring a resulting intensity of the non-specularly scattered light within the plurality of pixels when the common substrate transport arm supports the substrate holder in the extended position.

23. The integrated cluster tool system of claim 17 and further comprising:

cluster tool controller means operatively coupled to the loading module, the plurality of substrate processing modules, the substrate inspection module and the common substrate support arm for controlling a sequence of process steps on the substrate within the integrate cluster tool system; and

wherein the substrate inspection module further comprises inspection controller means coupled to the light source, the photodetector array and the cluster tool controller means for controlling the light source to illuminate the active surface through the light beam path, measuring a resulting intensity of the non-specularly scattered light within the plurality of pixels, and providing an output indicative of the measured intensity to the cluster tool controller means.

24. An electronic substrate processing and inspection chamber for processing and in-situ inspecting an active surface of a electronic substrate, the chamber comprising:

a chamber enclosure;

an electronic substrate holder positioned within the chamber enclosure for holding the electronic substrate;

an electronic substrate processing device supported within the chamber enclosure relative to the electronic substrate holder;

an optically transparent window formed in the chamber enclosure;

illumination means supported external to the chamber enclosure for illuminating substantially the entire active surface of the electronic substrate through the optically transparent window at a grazing angle of incidence with respect to the active surface; and

camera means having a field of view covering substantially the entire active surface of the electronic substrate for detecting non-specularly reflected light that is scattered from any defects on the active surface and for generating a digital output representative of intensity of the detected non-specularly reflected light per unit area of the active surface.

25. The electronic substrate processing and inspection chamber of claim 24 and further comprising means for digitally processing the digital output for detecting presence of the defects.

26. A method of processing and inspecting an active surface of a substrate, the method comprising:

polishing the active surface;

cleaning the active surface after polishing;

illuminating substantially the entire active surface with a first light beam oriented at a grazing angle of incidence with respect to the active surface such that any defects remaining on the active surface after polishing and cleaning scatter light from the first light beam;

applying the scattered light from the first light beam to a photodetector array having a plurality of pixels, wherein each pixel corresponds to a unit area on the active surface and the plurality of pixels together have a field of view covering substantially the entire active surface; and

measuring intensity of the scattered light applied to the photodetector array.

27. The method of claim 26 and further comprising:

identifying any defects remaining on the active surface within each unit area as a function of the measured intensity within the corresponding pixel in the photodetector array.

28. The method of claim 27 wherein identifying any defects comprises:

comparing the measured intensity within each of the plurality of pixels with an intensity threshold;

identifying the pixels in which the measured intensity exceeds the intensity threshold;

identifying the unit areas on the active surface that correspond to the pixels in which the measured intensity exceeds the intensity threshold; and

generating a list of defect locations based on the identified unit areas.

29. The method of claim 26 wherein the substrate comprises a patterned semiconductor wafer and wherein the method further comprises identifying defects on the active surface of the patterned semiconductor wafer as a function of the measured intensity within the plurality of pixels in the photodetector array.

30. The method of claim 26 wherein the defects include particles residing on the active surface following polishing and cleaning and wherein the method further comprises:

comparing the measured intensity within each of the plurality of pixels with an intensity threshold;

counting the pixels in which the measured intensity exceeds the intensity threshold;

generating a count of the particles residing on the active surface based on the count of pixels in which the measured intensity exceeds the threshold.

31. The method of claim 26 and further comprising:

comparing the measured intensity within each of the plurality of pixels with an intensity threshold;

identifying a group of the pixels in which the measured intensity exceeds the intensity threshold and in which each of the pixels in the group is spatially contiguous with the other pixels in the group within the photodetector array; and

associating the group of the pixels with a single defect on the active surface.

32. The method of claim 26 and further comprising:

identifying scratches on the active surface produced by the step of polishing based on a pattern of the measured intensity within the plurality of pixels in the photodetector array.

33. The method of claim 26 wherein the active surface has a surface roughness following polishing and cleaning which scatters light from the first light beam and wherein the method further comprises:

measuring the surface roughness as a function of the measured intensity.

34. The method of claim 26 wherein the active surface has a surface roughness following polishing and cleaning which scatters light from the first light beam and wherein measuring intensity comprises:

measuring intensity within each of the plurality of pixels; and

subtracting a surface roughness intensity value, which is representative of the surface roughness, from the measured intensity within each of the plurality of pixels.

35. The method of claim 26 wherein the substrate has a perimeter with an orienting feature and wherein the method further comprises:

illuminating the entire active surface and the entire perimeter of the substrate with a second light beam oriented at a substantially normal angle of incidence with respect to the active surface;

applying reflected light of the second light beam from the active surface to the photodetector array such that the plurality of pixels together have a second field of view which includes substantially the entire active surface and the entire perimeter; and

measuring intensity of the applied reflected light;

identifying a position of the perimeter and a position of the orienting feature within the second field of view; and

defining coordinates on the active surface based on the positions of the perimeter and the locating feature.

36. The method of claim 26 wherein polishing comprises planarizing the active surface with a chemical mechanical polisher.

37. The method of claim 26 wherein cleaning comprises mechanically scrubbing the active surface, rinsing the active surface with a liquid and spinning the active surface until the active surface is dry.

38. The method of claim 26 and further comprising:

transporting the substrate along a mechanical substrate transport path from a first substrate holder to a polishing station;

performing the step of polishing at the polishing station;

transporting the substrate along the mechanical substrate transport path from the polishing station to a cleaning station;

performing the step of cleaning at the cleaning station;

transporting the substrate along the mechanical substrate transport path from the cleaning station to an inspection station;

performing the steps collecting, transmitting, mapping and measuring at the inspection station; and

transporting the substrate along the mechanical substrate transport path from the inspection station to a second substrate holder.

40. The apparatus of claim 38 and further comprising:

first controller means operatively coupled to the polishing station, the cleaning station, the drying station and the inspection station for controlling a sequence of process steps on the substrate within the apparatus; and

wherein the substrate inspection station further comprises second controller means coupled to the light source, the photodetector array and the first controller means for controlling the light source to illuminate the active surface through the light beam path, measuring a resulting intensity of the non-specularly scattered light within the plurality of pixels, and providing an output indicative of the measured intensity to the first controller means.

39. A substrate polishing and inspection apparatus comprising:

a substrate travel path for carrying a substrate having an active surface to be polished;

a polishing station positioned along the substrate travel path;

a cleaning station positioned along the substrate travel path, downstream of the polishing station;

a drying station positioned along the substrate travel path, downstream of the cleaning station; and

a substrate inspection station positioned along the substrate travel path, downstream of the drying station and comprising;

an enclosure having a substrate loading aperture which communicates with the substrate travel path;

a substrate holding position within the enclosure;

a light source having a light beam port;

a light beam path extending from the light beam port to the substrate holding position and having a grazing angle of incidence with respect to the active surface when the substrate is held in the substrate holding position, wherein the light beam path illuminates substantially the entire active surface;

a lens which is oriented relative to the substrate holding position to collect non-specularly reflected light scattered from the light beam path by any defects, including particles, on the active surface, the lens having a focal plane; and

a photodetector array having a plurality of pixels which are positioned within the focal plane of the lens, wherein each pixel corresponds to a unit area on the active surface and the plurality of pixels together have a field of view that covers substantially the entire active surface.