Apparatus for optical inspection of wafers during polishing

• US 6,752,689 B2
• Filed: 07/05/2001
• Issued: 06/22/2004
• Est. Priority Date: 05/23/1995
• Status: Expired due to Term

• Current Assignee: Nova Measuring Instruments Limited (Honeywell International Inc.)
• Original Assignee: Nova Measuring Instruments Limited (Honeywell International Inc.)
• Inventors: Finarov, Moshe
• Primary Examiner(s): Morgan, Eileen P.
• Application Number:
  US09/898,467
• Publication Number:
  US 20020051135A1
• Time in Patent Office: 1,083 Days
• Field of Search: 451/6, 451/41, 451/54, 451/63, 451/285, 451/287, 451/288, 451/9, 451/10, 156/345.13, 156/345.15, 156/345.16, 438/691, 438/692
• US Class Current: 451/6
• CPC Class Codes: B24B 37/005 Control means for lapping machines or devices
• CPC Class Codes: B24B 37/013 Devices or means for detecting lapping completion
• CPC Class Codes: B24B 49/12 involving optical means
• CPC Class Codes: H01L 21/67253 Process monitoring, e.g. flow or thickness monitoring
• CPC Class Codes: H01L 21/6838 with gripping and holding devices using a vacuum; Bernoulli devices
• 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
• CPC Class Codes: H01L 22/20 Sequence of activities consisting of a plurality of measurements, corrections, marking or sorting steps

Abstract

An optical system is disclosed for the inspection of wafers during polishing which also includes a measurement system for measuring the thickness of the wafers top layer. The optical system views the wafer through a window and includes a gripping system, which places the wafer in a predetermined viewing location while maintaining the patterned surface completely under water. The optical system also includes a pull-down unit for pulling the measurement system slightly below the horizontal prior to the measurement and returns the measuring system to the horizontal afterwards.

Claims

1. A measurement station for use with a processing machine that includes a processing station for processing a semiconductor wafer and an exit station outside the processing station and including a wafer transfer means and at least one wafer cassette, the measurement station being so dimensioned as to be installable within the exit station of the processing machine and comprising a spectrophotometric measuring unit and a holding unit for receiving and holding the wafer in a measuring position during measurements, said measuring unit comprising an optical system including an imaging system operable to locate measurements, a focusing optics for focusing illuminating light onto the wafer and collecting light reflected from the illuminated water;

a beam splitter for directing the illuminating light towards the wafer and directing the collected reflected light towards the spectrophotometer; and

a pin hole mirror accommodated in an optical path of the collected light propagating towards the spectrophotometer and separating a portion of the collected light to propagate to a charge coupled device (CCD) for imaging.

2. The measurement station according to claim 1, wherein said measuring unit is operable to measure a thickness of at least a top layer of the wafer.

3. The measurement station according to claim 1, wherein said measuring unit is operable to carry out optical inspect ion of the processed wafer.

4. The measurement station according to claim 1, comprising a support assembly for supporting the wafer that is to be received by the holding unit.

5. The measurement station according to claim 1, wherein the measuring and holding units are separated by a window through which at least a part of the wafer being held is viewable to enable optical measurements.

6. The measurement station according to claim 1, wherein said holding unit comprises an assembly movable along an axis perpendicular to the wafer'"'"'s surface, thereby enabling said holding of the wafer in the measuring position.

7. The measurement station according to claim 1, having a footprint in at least one dimension of about a size of the wafer'"'"'s diameter.

8. The processing machine according to claim 1, wherein said processing tool is a polisher.

9. The processing machine according to claim 1, and also comprising a robot for supplying the processed wafer to the measurement station.

10. The measurement station according to claim 4, wherein the support assembly is configured to receive the wafer from the wafer transfer means of the exit station and enable the wafer transfer into the measuring position.

11. The measurement station according to claim 10, wherein the support assembly includes two support elements displaceable with respect to each other.

12. The measurement station according to claim 4, wherein the support assembly is configured for supporting the wafer at its periphery region.

13. The measurement station according to claim 1, wherein the optical imaging system is operable to perform pattern recognition.

14. The measurement station according to claim 1, wherein the measuring unit comprises a fiber optics for directing light from a light source towards the focusing optics.

15. The measurement station according to claim 1, wherein the focusing optics comprises an objective lens arrangement.

16. The measurement station according to claim 1, wherein the imaging system includes a lens arrangement accommodated between the light detector and the pin hole mirror.

17. The measurement station according to claim 1, wherein the spectrophotometric measuring unit comprises a lens arrangement accommodated between the pin hole mirror and a spectrophotometer.

18. The measurement station according to claim 1, wherein the optical system is configured for providing substantially normal incidence of the illuminating light.

19. The measurement station according to claim 1, wherein the pin hole mirror is accommodated so as to be an aperture stop in an optical path of the collected light, the pin hole mirror thereby appearing as a dark area in an image of a measurement spot on the wafer and allowing for locating the measurement spot.

20. The measurement station according to claim 1, wherein the holding unit comprises a vacuum assembly for holding the wafer by vacuum.

21. A processing machine for processing a semiconductor wafer, the processing machine comprising a processing station having a processing tool to be applied to the wafer, and an optical measurement station, the optical measurement station being associated with an exit station of the processing machine that includes a wafer transfer means and at least one wafer cassette, the optical measurement station comprising:

a holding unit for receiving the wafer and holding it in a measuring position during measurements; and

an optical system including a spectrophotometric measuring unit, an imaging system including a light detector operable to locate measurements, a focusing optics for focusing illuminating light onto the wafer and collecting light reflected from the illuminated water;

a beam splitter for directing the illuminating light towards the wafer and directing the collected reflected light towards the spectrophotometer; and

a pin hole mirror accommodated in an optical path of the collected light and separating a portion of the collected light to the light detector.

22. The processing machine according to claim 21, wherein said measuring unit is operable to measure a thickness of at least a top layer of the wafer.

23. The processing machine according to claim 21, wherein said imaging system comprises a charge coupled device (CCD).

24. The processing machine according to claim 21, comprising a support assembly for supporting the wafer that is to be received by the holding unit.

25. The processing machine according to claim 21, wherein the measuring and holding unit are separated by a window through which at least a part of the water being held is viewable to enable optical measurements.

26. The processing machine according to claim 21, wherein said holding unit comprises an assembly movable along an axis perpendicular to the wafer'"'"'s surface, thereby enabling said holding of the wafer in the measuring position.

27. The processing machine according to claim 21, wherein said measurement station has a footprint in at least one dimension of about a size of the wafer'"'"'s surface.

28. The processing machine according to claim 24, wherein the support assembly is configured to receive the wafer from the wafer transfer means of the exit station and enable the wafer transfer into the measuring position.

29. The processing machine according to claim 28, wherein the support assembly includes two support elements displaceable with respect to each other.

30. The processing machine according to claim 24, wherein the support assembly is configured for supporting the wafer at its periphery region.

31. The processing machine according to claim 21, wherein the optical imaging system is operable to perform pattern recognition.

32. The processing machine according to claim 21, wherein the measuring unit comprises a fiber optics for directing light from a light source towards the focusing optics.

33. The processing machine according to claim 21, wherein the focusing optics comprises an objective lens arrangement.

34. The processing machine according to claim 21, wherein the imaging system includes a lens arrangement accommodated between the light detector and the pin hole mirror.

35. The processing machine according to claim 21, wherein the spectrophotometric measuring unit comprises a lens arrangement accommodated between the pin hole mirror and a spectrophotometer.

36. The processing machine according to claim 21, wherein the optical system is configured for providing substantially normal incidence of the illuminating light.

37. The processing machine according to claim 21, wherein the pin hole mirror is accommodated so as to be an aperture stop in an optical path of the collected light, the pin hole mirror thereby appearing as a dark area in an image of a measurement spot on the wafer and allowing for locating the measurement spot.

38. The processing machine according to claim 21, wherein the holding unit comprises a vacuum assembly for holding the wafer by vacuum.