Wafer inspection

Patent metadata

Field	Value
Publication number	US-10488348-B2
Application number	US-201815882946-A
Country	US
Kind code	B2
Filing date	Jan 29, 2018
Priority date	Jul 12, 2011
Publication date	Nov 26, 2019
Grant date	Nov 26, 2019

Abstract

Systems configured to inspect a wafer are provided. One system includes an illumination subsystem configured to direct pulses of light to an area on a wafer; a scanning subsystem configured to scan the pulses of light across the wafer; a collection subsystem configured to image pulses of light scattered from the area on the wafer to a sensor, wherein the sensor is configured to integrate a number of the pulses of scattered light that is fewer than a number of the pulses of scattered light that can be imaged on the entire area of the sensor, and wherein the sensor is configured to generate output responsive to the integrated pulses of scattered light; and a computer subsystem configured to detect defects on the wafer using the output generated by the sensor.

First claim

What is claimed is:

1. A system configured to inspect a wafer, comprising:
an illumination subsystem configured to direct multiple light beams to substantially the same area on a wafer, wherein the multiple light beams have substantially the same wavelength and polarization characteristics;
a scanning subsystem configured to scan the multiple light beams across the wafer;
a collection subsystem configured to image light scattered from the substantially the same area on the wafer to a sensor, wherein the sensor generates output responsive to the scattered light; and
a computer subsystem configured to detect defects on the wafer using the output of the sensor, wherein the computer subsystem is further configured to use the output responsive to the scattered light from the substantially the same area due to illumination by a first of the multiple light beams to determine a power of a second of the multiple light beams that should be directed to the substantially the same area.

2. The system of claim 1 , wherein the multiple light beams arc directed to the substantially the same area on the wafer at substantially the same polar angles and different azimuth angles.

3. The system of claim 1 , wherein the multiple light beams are directed to the substantially the same area on the wafer simultaneously.

4. The system of claim 1 , wherein the multiple light beams are laser beams.

5. The system of claim 1 , wherein the multiple light beams illuminate the substantially the same area on the wafer in area illumination mode.

6. The system of claim 1 , wherein the substantially the same area on the wafer has a lateral dimension of greater than 50 microns.

7. The system of claim 1 , wherein the multiple light beams are pulsed light beams, and wherein the illumination subsystem is further configured to direct the second of the multiple light beams to the substantially the same area on the wafer later than the first of the multiple light beams is directed to the substantially the same area by the illumination subsystem such that a peak pulse power incident on the wafer due to the multiple light beams is less than if the multiple light beams were directed to the substantially the same area on the wafer at the same time.

8. The system of claim 1 , wherein the multiple light beams are pulsed light beams, and wherein the illumination subsystem is further configured to direct the second of the multiple light beams to the substantially the same area on the wafer later than the first of the multiple light beams is directed to the substantially the same area by the illumination subsystem such that the pulsed light beams illuminate the substantially the same area as one continuous pulse of light having a duration longer than each of the pulsed light beams.

9. The system of claim 1 , wherein the multiple light beams are pulsed light beams, wherein the illumination subsystem is further configured to direct the first of the multiple light beams to the substantially the same area on the wafer earlier in time than the second of the multiple fight beams is directed to the substantially the same area by the illumination subsystem, wherein the first and second of the multiple light beams have different shapes and sizes on the wafer from each other, and wherein the computer subsystem is further configured to use the output responsive to the scattered light from the substantially the same area due to illumination by the first of the multiple light beams to determine if the second of the multiple light beams should be directed to the substantially the same area.

10. The system of claim 9 , wherein the illumination subsystem comprises a Q-switched laser, and Wherein if the computer subsystem determines that the second of the multiple light beams should not be directed to the substantially the same area, then the computer subsystem prevents the second of the multiple light beams from illuminating the substantially the same area.

11. The system of claim 1 , wherein the multiple light beams are pulsed light beams, wherein the illumination subsystem is further configured to direct the first of the multiple light beams to the substantially the same area on the wafer earlier in time than the second of the multiple fight beams is directed to the substantially the same area by the illumination subsystem, and wherein the first and second of the multiple light beams have different shapes and sizes on the wafer from each other.

12. The system of claim 11 , wherein the illumination subsystem comprises a Q-switched laser, and wherein the computer subsystem attenuates a power of the Q-switched laser based on the determined power.

13. The system of claim 11 , wherein the computer subsystem is further configured to monitor a power of the second of the multiple light beams that is actually directed to the substantially the same area and to alter one or more parameters of the system based on the power directed to the substantially the same area to normalize the power of the second of the multiple light beams that is actually directed to the substantially the same area.

14. The system of claim 1 , wherein the multiple light beams are generated by only one single laser of the illumination subsystem.

15. The system of claim 1 , wherein the multiple light beams are generated by multiple lasers of the illumination subsystem.

16. The system of claim 1 , wherein the multiple light beams comprise one light beam generated by a light source of the illumination subsystem and another light beam formed by collecting light reflected from the substantially the same area on the wafer and directing the collected reflected light back to the substantially the same area on the wafer.

17. The system of claim 1 , wherein the illumination subsystem is further configured to vary the multiple light beams directed to the substantially the same area on the wafer as a function of time, wherein the collection subsystem is further configured to image the light scattered from multiple areas on the wafer to the sensor, and wherein the sensor and a light source of the illumination subsystem are gated in sync with one another.

18. The system of claim 17 , wherein the multiple light beams are directed to the substantially the same area on the wafer at different azimuth angles, different polar angles, or different azimuth and polar angles.

19. The system of claim 17 , wherein the illumination subsystem is further configured to alter the wavelength and polarization characteristics of the multiple light beams, and wherein the multiple light beams directed to the substantially the same area on the wafer as the function of time have different wavelength characteristics from each other, different polarization characteristics from each other, or different wavelength and polarization characteristics from each other.

20. The system of claim 1 , further comprising an optical element configured to separate the scattered light collected in different segments of a collection numerical aperture of the collection subsystem, wherein the sensor is further configured to detect one of the different segments, and wherein the system further comprises another sensor configured to detect another of the different segments.

21. The system of claim 20 , wherein the system is further configured to alter or replace the optical element depending on the one of the different segments that is to be detected by the sensor and the other of the different segments that is to he detected by the other sensor.

22. The syste

Assignees

• Kla Tencor Corp

Inventors

• Romanovsky Anatoly
• Maleev Ivan
• Kavaldjiev Daniel
• Yuditsky Yury
• Woll Dirk
• Biellak Stephen
• Vaez-Iravani Mehdi
• Zhao Guoheng

Classifications

• G01N21/47

  Scattering, i.e. diffuse reflection (G01N21/25, G01N21/41 take precedence {G01N21/55 takes precedence}) · CPC title

• G01N21/9501 Primary

  Semiconductor wafers (manufacturing processes per se of semiconductor devices implementing a measuring step H10P74/20) · CPC title

• G01N21/8851

  Scan or image signal processing specially adapted therefor, e.g. for scan signal adjustment, for detecting different kinds of defects, for compensating for structures, markings, edges (G01N21/8806 and G01N21/93 - G01N21/95692 take precedence; optical measurement of dimensions G01B11/00; optical scanning G02B26/10; image transformation G06T3/00; computerised image enhancement G06T5/00; image processing per se for flaw detection G06T7/0002) · CPC title

• G01N21/956

  Inspecting patterns on the surface of objects {(contactless testing of electronic circuits G01R31/308; testing currency G07D; manufacturing processes per se of semiconductor devices implementing a measuring step H10P74/20)} · CPC title

• G01N21/8806

  Specially adapted optical and illumination features · CPC title