DEFECT DETECTION USING TIME DELAY LOCK-IN THERMOGRAPHY (LIT) AND DARK FIELD LIT

• US 20100073665A1
• Filed: 02/05/2008
• Published: 03/25/2010
• Est. Priority Date: 02/05/2008
• Status: Active Grant

• Current Assignee: KLA-Tencor Corporation (KLA Corporation)
• Original Assignee: KLA-Tencor Corporation (KLA Corporation)
• Inventors: Dharmadhikari, Vineet, Levy, Ady, Vaez-Iravani, Mehdi, Zhao, Guoheng, Ngai, Samuel, Zapalac, Geordie
• Granted Patent: US 7,709,794 B2
• Time in Patent Office: Days
• US Class Current: 356/36
• CPC Class Codes: G01N 25/72 Investigating presence of flaws
• CPC Class Codes: G01R 31/308 using non-ionising electromagnetic radiation, e.g. optical radiation investigating or analysing materials by the use of optical means G01N21/00; image analysis G06T7/00

Abstract

To increase inspection throughput, the field of view (FOV) of an IR camera can be moved over the sample at a constant velocity. Throughout this moving, a modulation (e.g. optical or electrical) can be provided to the sample and IR images can be captured using the IR camera. Moving the FOV, providing the modulation, and capturing the IR images can be synchronized. The IR images can be filtered to generate the time delay LIT, thereby providing defect identification. In one embodiment, this filtering accounts for the number of pixels of the IR camera in a scanning direction. For the case of optical modulation, a dark field region can be provided for the FOV throughout the moving, thereby providing an improved signal-to-noise ratio (SNR) during filtering.

Claims

1. A method of performing time delay lock-in thermography (LIT) on a sample, the method comprising:

moving a field of view (FOV) of an IR camera over the sample, the moving being at a constant velocity;

providing a modulation to the sample throughout the moving;

capturing IR images using the IR camera throughout the moving, wherein moving the FOV, providing the modulation, and capturing the IR images are synchronized; and

filtering the IR images to generate a time delay LIT image, thereby providing defect identification.

wherein filtering includes performing two equations;

2. The method of claim 1, wherein the modulation is one of optical and electrical.

3. The method of claim 1, wherein the sample is one of a semiconductor wafer, a solar cell, a solar panel, a continuous web, and a printed circuit board.

6. The method of claim 1, wherein moving includes using at least one of a scanning stage, bi-directional linear stages in a gantry system, a gantry bridge, a conveyor, and at least one roller.

4. (canceled)

5. The method of claim 4, further including providing a dark field illumination for the FOV throughout the moving.

7. A method of performing dark field lock-in thermography (LIT) on a sample, the method comprising:

positioning a field of view (FOV) of an IR camera within a dark field region on the sample;

providing a modulation to the sample;

capturing IR images using the IR camera,

wherein providing the modulation and capturing the IR images are synchronized; and

filtering the IR images to generate an LIT image, thereby providing defect identification, wherein filtering includes performing two equations;

8. The method of claim 7, further including rotating the sample to reposition the FOV and the dark field region on another section of the sample, and then repeating providing the modulation, capturing the IR images, and filtering the IR images.

9. The method of claim 7, wherein the modulation is one of optical and electrical.

10. The method of claim 7, wherein the sample is one of a semiconductor wafer, a solar cell, a solar panel, a continuous web, and a printed circuit board.

12. The method of claim 7, wherein positioning and rotating include using at least one of a scanning stage, bi-directional linear stages in a gantry system, a gantry bridge, a conveyor, a rotating chuck, and at least one roller.

11. (canceled)

13. A system for performing time delay lock-in thermography (LIT) on a sample, the system comprising:

an IR camera for capturing images of the sample;

scanning components for moving a field of view (FOV) of the IR camera over the sample at a constant velocity;

modulation components for providing a modulation to the sample when moving the FOV;

a clock source for synchronizing the capturing of images, the moving of the FOV, and the providing of the modulation; and

an image processor for receiving the captured images and generating a time delay LIT image to provide defect detection,

wherein the image processor includes filters that implement two equations;

14. The system of claim 13, further including one of a light shield and a light pipe for providing a dark field region for the FOV.

15. The system of claim 13, wherein the scanning components include at least one of a scanning stage, a conveyor, bi-direction linear stages in a gantry system, a gantry bridge, and at least one roller.

16. The system of claim 13, wherein the sample is one of a semiconductor wafer, a solar cell, a solar panel, a continuous web, and a printed circuit board.

17. (canceled)

18. A system for performing dark field, lock-in thermography (LIT) on a sample, the system comprising:

an IR camera for capturing images of the sample;

positioning components for positioning a field of view (FOV) of the IR camera over the sample;

optical modulation components for providing an optical modulation to the sample after positioning the FOV;

a light directing component for providing a dark field region for the FOV;

a clock source for synchronizing the capturing of images and the providing of the modulation; and

an image processor for receiving the captured images and generating a time delay LIT image to detect a defect on the sample,

wherein the image processor includes filters that implement two equations;

19. The system of claim 18, wherein the light directing component includes a light shield.

20. The system of claim 18, wherein the light directing component includes a light pipe.

21. The system of claim 18, wherein the positioning components include at least one of a scanning stage, a conveyor, bi-direction linear stages in a gantry system, a gantry bridge, a rotating chuck, and at least one roller.

22. The system of claim 18, wherein the sample is one of a semiconductor wafer, a solar cell, a solar panel, a continuous web, and a printed circuit board.

23. (canceled)