Inspection system and apparatus

• US 7,107,158 B2
• Filed: 03/11/2005
• Issued: 09/12/2006
• Est. Priority Date: 02/03/2003
• Status: Expired due to Fees

• Current Assignee: Qcept Investments, LLC
• Original Assignee: Qcept Technologies, Inc.
• Inventors: Hawthorne, Jeffrey Alan, Steele, M. Brandon
• Primary Examiner(s): Barlow, John
• Assistant Examiner(s): Walling, Meagan S
• Application Number:
  US11/078,255
• Publication Number:
  US 20050162178A1
• Time in Patent Office: 550 Days
• Field of Search: 702/35, 702/36, 324/765, 438/12, 438/200, 438/906, 134/1.2, 134/1.3
• US Class Current: 702/35
• CPC Class Codes: G01N 2033/0095 Semiconductive materials
• CPC Class Codes: G01N 27/002 by investigating the work function voltage
• CPC Class Codes: G01R 31/312 by capacitive methods

Abstract

A method and system for identifying a defect or contamination on a surface of a sample. The system operates by detecting changes in work function across a surface via both vCPD and nvCPD. It utilizes a non-vibrating contact potential difference (nvCPD) sensor for imaging work function variations over an entire sample. The data is differential in that it represents changes in the work function (or geometry or surface voltage) across the surface of a sample. A vCPD probe is used to determine absolute CPD data for specific points on the surface of the sample. The combination of vibrating and non-vibrating CPD measurement modes allows the rapid imaging of whole-sample uniformity, and the ability to detect the absolute work function at one or more points.

Claims

1. An analysis method for inspecting a surface of a sample, comprising the steps of:

providing a processing system including a sample scanning system for analyzing defects;

fixing the sample upon a sample stage of the sample scanning system;

providing a contact potential difference (CPD) sensor having a vibrating contact potential difference (vCPD) sensor mode and a non-vibrating contact potential difference (nvCPD) sensor mode;

engaging a positioning mechanism in communication with the CPD sensor in an nvCPD mode whereby the CPD difference sensor is positionable in relation to the sample stage via the positioning mechanism;

continuously scanning, via relative motion, the CPD sensor about the sample;

generating relative CPD data from the nvCPD mode of the CPD sensor during at least the scanning of the sample relative to the CPD sensor, the relative CPD data being representative of relative CPD along a track of the sample surface relative to the CPD sensor;

assembling the relative CPD data to form CPD data representative of the sample surface;

identifying at least one point on the sample surface to measure absolute CPD;

positioning the CPD sensor above the at least one point in vCPD mode; and

generating absolute CPD data for the at least one point.

2. The method of inspecting a sample'"'"'s surface of claim 1 further comprising the step of amplifying the topographical signal relative to the chemical signal.

3. The method of inspecting a sample'"'"'s surface of claim 1 further comprising the step of voltage biasing a portion of the inspection system.

4. The method of inspecting a sample'"'"'s surface of claim 3 further comprising the steps of:

providing two different bias voltages to a portion of the inspection system chosen from the group consisting of the nvCPD sample, the sample, and combinations thereof; and

subtracting the signal formed with one bias voltage from the signal formed with the other different bias voltage.

5. The method of inspecting a sample'"'"'s surface of claim 1, wherein the relative motion is accomplished by rotating the sample about a central axis with the sensor tracing tracks of data at varying radii.

6. The method of inspecting a sample'"'"'s surface of claim 5, further comprising the step of decreasing rotational velocity in proportion with the motion of the sensor to provide the sensor with substantially even data density.

7. The method of inspecting a sample'"'"'s surface of claim 1 further comprising the step of providing a plurality of nvCPD sensors.

8. The method of inspecting a sample'"'"'s surface of claim 7, wherein the plurality of sensors are arranged in a linear array.

9. The method of inspecting a sample'"'"'s surface of claim 8, wherein the plurality of sensors are arranged in a two-dimensional array.

10. The method of inspecting a sample'"'"'s surface of claim 8 further comprising the step of providing the plurality of sensors at a plurality of heights.

11. The method of inspecting a sample'"'"'s surface of claim 8 further comprising the step of providing a voltage bias to the plurality of sensors.

12. The method of inspecting a sample'"'"'s surface of claim 1, wherein the relative motion is provided by moving the nvCPD sensor with respect to the sample which is maintained substantially stationary.

13. The method of inspecting a sample'"'"'s surface of claim 1, wherein the relative motion is provided by moving the sample with respect to the nvCPD sensor which is substantially stationary.

14. The method of inspecting a sample'"'"'s surface of claim 1 further including the step of providing a height sensor.

15. The method of inspecting a sample'"'"'s surface of claim 1, further including the step of calibrating the height of the nvCPD sensor to measurements made by the height sensor.

16. The method of inspecting a sample'"'"'s surface of claim 1, wherein the step of calibrating the height of the nvCPD sensor to measurements made by the height sensor further comprises the steps of:

positioning the height sensor above a reference surface so that the distance between the reference surface and the height sensor is within a range of detection for the height sensor;

recording the height of the sensors as z1;

recording the height of the height sensor reading above a reference point as h1;

moving the nvCPD sensor to a position above the reference point on the reference surface;

slowly moving the nvCPD sensor down towards the reference surface while monitoring the level of the nvCPD sensor signal; and

recording as z2 the height when the nvCPD sensor contacts the reference surface as indicated by a significant change in the output of the nvCPD sensor.

17. The method of inspecting a sample'"'"'s surface of claim 16 further comprising the step of positioning the nvCPD sensor at a desired height of h* by the steps of:

positioning the height sensor above the surface so that the surface is within a measurement range of the height sensor;

recording this height as z3 and the height sensor reading as h3;

positioning the non-vibrating contact potential probe above the point z3; and

adjusting the height to z*=z3−

(h3−

h1)−

(z1−

z2)+h*, wherein the height of the nvCPD sensor is located above the surface of point z3 at height h*.

18. The method of inspecting a sample'"'"'s surface of claim 1, wherein the sample comprises a liquid crystal panel.

19. The method of inspecting a sample'"'"'s surface of claim 1, wherein the sample comprises a semiconductor wafer.

20. The method of inspecting a sample'"'"'s surface of claim 1, wherein the relative CPD data has a first signal portion characteristic of a topographical feature of the sample'"'"'s surface and further has a second signal portion representing chemical features of the sample'"'"'s surface.

21. The method of inspecting a sample'"'"'s surface of claim 1, further comprising the step of processing the relative CPD to automatically detect a pattern that represents a chemical defect or chemical non uniformity present on the sample surface.

22. The method of inspecting a sample'"'"'s surface of claim 1, further comprising performing a calibration of the CPD sensor.

23. The method of inspecting a sample'"'"'s surface of claim 1, wherein the step of identifying at least one point is performed automatically according to predetermined rules.

24. The method of inspecting a sample'"'"'s surface of claim 1, wherein the step of identifying at least one point is performed manually by a user.

25. A system for inline processing of a semiconductor wafer comprising:

a semiconductor wafer processing system to identify at least one of contaminants and non uniformities on a semiconductor wafer, the processing system including a wafer scanning system;

a semiconductor wafer stage of the wafer scanning system for receiving the semiconductor wafer;

the semiconductor wafer stage being rotatable and engageable with the semiconductor wafer;

a contact potential difference sensor system including a non-vibrating contact potential difference probe and a vibrating contact potential difference probe;

a positioning assembly in communication with the sensor system whereby the sensor system can be positioned relative to the semiconductor wafer secured on the semiconductor wafer stage;

the non-vibrating contact potential difference probe adapted to produce a relative contact potential difference signal characteristic of the contaminants on the semiconductor wafer in response to a change in the contact potential difference generated by the relative motion of the non-vibrating contact potential difference probe and the semiconductor wafer;

the vibrating contact potential difference probe adapted to produce an absolute contact potential difference signal characteristic of the contaminants on the semiconductor wafer in response to a change in the contact potential difference generated by the vibration of the probe while positioned over a point on the semiconductor wafer surface;

a computer system in communication with the contact potential difference sensor system, whereby relative contact potential difference data and absolute contact potential difference data is output by the probe to the computer; and

a display providing a visual image characteristic of the chemical contaminants and their spatial distribution on the semiconductor wafer generated by the computer system and representative of the absolute and relative contact potential difference data.

26. The system of claim 25, wherein a generated bias voltage is applied to a portion of the system.

27. The system of claim 25 further comprising a probe height sensor.

28. The system of claim 25, wherein the relative motion is provided by moving the semiconductor wafer with respect to the non-vibrating contact potential difference sensor which is substantially stationary.

29. The system of claim 25 further comprising a plurality of non-vibrating contact potential probes.

30. The system of claim 25, wherein the contact potential difference sensor system comprise one probe having a vibrating mode and a non-vibrating mode.

31. The system of claim 25, wherein the contact potential difference sensor system comprises a first probe operating as a non-vibrating contact potential difference probe and a second probe operating as a vibrating contact potential difference probe.

32. A method for inspecting the surface of a sample, comprising the steps of:

providing a processing system including a sample scanning system for analyzing defects;

fixing the sample upon a sample stage of the sample scanning system;

providing a contact potential difference (CPD) sensor system having a vibrating contact potential difference (vCPD) sensor mode and a non-vibrating contact potential difference (nvCPD) sensor mode;

engaging a positioning mechanism in communication with the CPD sensor system in the nvCPD mode whereby the CPD sensor system is positionable in relation to the sample stage via the positioning mechanism;

continuously scanning the sample surface with the nvCPD mode of the CPD sensor system, generating relative CPD data from the CPD system;

the relative CPD data being representative of relative CPD of the sample surface;

selecting a point on the sample surface;

positioning the CPD sensor system in vCPD mode above the point and determining absolute CPD data for the point; and

determining the absolute CPD for the sample surface based on the point'"'"'s absolute CPD data and the sample'"'"'s relative CPD data.

33. The method for inspecting the surface of a sample of claim 32, wherein the step of selecting a point further comprises, identifying at least a first point and a second point on the sample surface to measure absolute CPD.

34. The method for inspecting the surface of a sample of claim 33, further comprising the steps of:

positioning the CPD sensor above the first point in vCPD mode;

generating absolute CPD data for the first point;

continuously scanning, via relative motion, the CPD sensor, in nvCPD mode, from the first point to the second point;

generating a first track of relative CPD data from the nvCPD mode of the CPD sensor during the scanning of the sample, the first track of relative CPD data being representative of relative CPD from the first point of the plurality of points to the second point of the plurality of points;

positioning the CPD sensor above the second point in the vCPD mode;

generating absolute CPD data for the second point; and

determining absolute CPD data for sample surface along the first track.

35. The method for inspecting the surface of a sample of claim 32, wherein a plurality of tracks are generated representing substantially all of the sample surface.