Semiconductor inspection system and apparatus utilizing a non-vibrating contact potential difference sensor and controlled illumination

• US 20080217530A1
• Filed: 03/07/2007
• Published: 09/11/2008
• Est. Priority Date: 03/07/2007
• Status: Active Grant

• Current Assignee: Qcept Investments, LLC
• Original Assignee: Qcept Technologies, Inc.
• Inventors: Steele, M. Brandon, Yang, Yeyuan, Schulze, Mark, Hawthorne, Jeffrey Alan
• Granted Patent: US 7,659,734 B2
• Time in Patent Office: Days
• US Class Current: 250/307
• CPC Class Codes: G01N 27/002 by investigating the work function voltage
• CPC Class Codes: G01R 31/2648 Characterising semiconductor materials testing of materials or semi-finished products G01R31/2831; testing during manufacture H01L22/00
• CPC Class Codes: G01R 31/2656 using non-ionising electromagnetic radiation, e.g. optical radiation

Abstract

A method and system for identifying a defect or contamination on the surface of a semiconductor or in a semiconductor. The method and system involves providing a semiconductor with a surface, such as a semiconductor wafer, providing a non-vibrating contact potential difference sensor, providing a source of illumination with controllable intensity or distribution of wavelengths, using the illumination source to provide controlled illumination of the surface of the wafer under or near the non-vibrating contact potential sensor probe tip, using the non-vibrating contact potential difference sensor to scan the wafer surface during controlled illumination, generating data representative of changes in contact potential difference across the wafer surface, and processing that data to identify a pattern characteristic of a defect or contamination.

Claims

1. A method of detecting non-uniformities of a semiconductor wafer, comprising the steps of:

providing a semiconductor comprising a wafer having a wafer surface;

providing a contact potential difference sensor having a probe tip;

providing a source of illumination energy in communication with the wafer surface;

providing a mechanism providing variable illumination;

directing the illumination energy at an area of the wafer surface that includes a sampling area located in proximity with the contact potential difference sensor probe tip;

scanning the wafer surface laterally relative to the contact potential difference sensor while the surface of the semiconductor is illuminated;

generating sensor data representative of changes in the contact potential difference between the sensor probe tip and the wafer surface as the sensor probe tip scans laterally across the wafer surface; and

processing the contact potential difference sensor data to detect a pattern that represents a non-uniformity,

wherein the non-uniformity is selected from the group consisting of chemical non-uniformities, physical non-uniformities, electrical non-uniformities, and combinations thereof.

2. The method of claim 1, wherein the variable illumination energy comprises at least one of a varying intensity, varying light spectrum, and varying angle of input to the wafer surface.

3. The method of claim 1 wherein the illumination energy comprises wavelength(s) of light with energies that are greater than a band gap of the semiconductor wafer.

4. The method of claim 1 wherein the illumination energy comprises wavelength(s) of light with energies that are less than a band gap of the semiconductor.

5. The method of claim 1 wherein the non-uniformity comprises a variation in semiconductor doping density.

6. The method of claim 1 wherein the non-uniformity comprises a contaminant in the semiconductor.

7. The method of claim 6 wherein the contaminant comprises a metal or organic contaminant on the wafer surface of the semiconductor

8. The method of claim 1 wherein the non-uniformity comprises a variation in surface chemistry.

9. The method of claim 1 wherein the source of illumination energy comprises a laser.

10. The method of claim 1 wherein the probe tip of the contact potential difference sensor is transparent to wavelengths of illumination energy.

11. The method of claim 1 wherein the probe tip of the contact potential difference sensor is shaped to allow illumination of the area under the probe tip.

12. The method of claim 1 wherein the semiconductor comprises a covering of a film that is transparent to at least some wavelengths of illumination energy.

13. The method of claim 12 wherein the defect comprises charging on or in the transparent film.

14. The method of claim 1 further including the steps of scanning the wafer surface at least twice where the spectrum or intensity of illumination energy is changed between scans;

and processing the contact potential difference sensor data from the multiple scans to detect a pattern that represents a defect.

15. The method of claim 14 wherein the processing of the contact potential difference sensor data includes calculating the difference between the results of one scan and the results of a second scan, where the two scans were taken with different illumination conditions.

16. A system for detecting non-uniformities of a semiconductor wafer, comprising:

a semiconductor mounting surface adapted to receive a semiconductor wafer having a wafer surface;

a contact potential difference sensor having a probe tip and positionable adjacent to the mounted semiconductor wafer, the sensor and the semiconductor wafer movable relative to each other;

a source of illumination energy in communication with the surface, the source of illumination energy providing directable and variable illumination energy;

the sensor generating contact potential difference data as the sensor probe tip scans laterally across the semiconductor surface while an area of the wafer surface that includes a sampling area located in proximity with the contact potential difference sensor probe tip is illuminated by the illumination source of illumination energy; and

a processor for receiving the contact potential difference sensor data from the sensor and processing the data to detect a pattern that represents a non-uniformity.

17. The system of claim 16, wherein the non-uniformity is selected from the group consisting of chemical non-uniformities, physical non-uniformities, electrical non-uniformities, and combinations thereof.

18. The system of claim 16, wherein the illumination energy has a varying intensity, varying spectrum and varying angle of input to the wafer surface.

19. The system of claim 16 wherein the illumination energy contains wavelength(s) of light with energies that are greater than a band gap of the semiconductor.

20. The system of claim 16 wherein the illumination energy comprises wavelength(s) of light with energies that are less than a band gap of the semiconductor.

21. The system of claim 16 wherein the non-uniformity comprises a variation in semiconductor doping density.

22. The system of claim 16 wherein the non-uniformity comprises a contaminant in the semiconductor.

23. The system of claim 22 wherein the contaminant comprises a metal or organic contaminant on the wafer surface of the semiconductor.

24. The system of claim 16 wherein the non-uniformity comprises a variation in surface chemistry.

25. The system of claim 16 wherein the source of illumination energy comprises a laser.

26. The system of claim 16 wherein the probe tip of the contact potential difference sensor is transparent to wavelengths of the illumination energy.

27. The system of claim 16 wherein the probe tip of the contact potential difference sensor comprises a shape to allow illumination of the area under the probe tip.

28. The system of claim 16 wherein the semiconductor comprises a covering film that is transparent to at least some wavelengths of illumination energy.

29. The system of claim 28 wherein the defect comprises charging on or in the transparent film.