Optical method and system for defects detection in three-dimensional structures

Patent metadata

Field	Value
Publication number	US-10018574-B2
Application number	US-201515325877-A
Country	US
Kind code	B2
Filing date	Jul 14, 2015
Priority date	Jul 14, 2014
Publication date	Jul 10, 2018
Grant date	Jul 10, 2018

Abstract

An inspection system and method are presented for inspecting structures having a pattern formed by an array of elongated grooves having high aspect-ratio geometry, such as semiconductor wafers formed with vias. The inspection system comprises an imaging system and a control unit. The imaging system is configured and operable for imaging the structure with a dark-field imaging scheme and generating a dark-field image. The control unit comprises an analyzer module for analyzing pixels brightness in the dark-field image for identifying a defective groove, being a groove characterized by pixels brightness in the dark-field image lower than nominal brightness by a predetermined factor.

First claim

The invention claimed is:

1. A method for inspecting patterned structures for detecting defective features of a pattern, where the features under inspection are narrow grooves having high aspect ratio geometry, the method comprising:
performing dark-field imaging of at least a region of the structure including a plurality of the grooves, said dark-field imaging comprising illuminating said at least region of the structure including the plurality of the grooves according to a predetermined dark-field imaging scheme and detecting light returned from inside of the grooves in said region; and generating data indicative of a dark-field image of said at least region of the structure;
processing said data indicative of the dark-field image, said processing comprising analyzing pixels brightness within the image, and upon identifying a condition that brightness of the pixels corresponding to at least one of said grooves in said dark-field image is lower than nominal brightness by a predetermined factor, generating output data indicative of existence of at least one defective groove in said at least region of the structure.

2. The method according to claim 1 , wherein said imaging is performed with a field of view selected such that the image includes a portion of the pattern including the plurality of the grooves.

3. The method according to claim 1 , wherein the nominal brightness is defined by at least one of the following: (i) brightness of pixels in said dark-field image corresponding to other grooves in said pattern; and (ii) brightness of pixels corresponding to grooves in a reference dark-field image.

4. The method according to claim 1 , wherein said processing further comprises determining location data for said at least one defective groove.

5. The method according to claim 4 , wherein said analyzing of the pixels brightness further comprises comparing the dark-field image with the bright-field image.

6. The method according to claim 1 , wherein said imaging further comprises applying a bright field imaging scheme to said at least region of the structure, and generating a bright-field image.

7. The method according to claim 1 , wherein said analyzing of the pixels brightness comprises comparing said data indicative of the dark-field image to a reference dark-field image.

8. The method according to claim 1 , further comprising at least one of the following: (a) utilizing said output data indicative of said at least one defective groove, classifying the corresponding structure as a defective structure, and generating classification data; and (b) inspecting at least one site of the structure including said at least one defective groove.

9. The method according to claim 1 , further comprising utilizing said output data indicative of said at least one defective groove, classifying the corresponding structure as a defective structure, generating classification data, and storing the classification data.

10. The method according to claim 1 , wherein said predetermined dark-field imaging scheme comprises illuminating the structure with normal incidence mode.

11. The method according to claim 10 , wherein the predetermined dark-field imaging scheme further comprises a cross-polarization scheme.

12. The method according to claim 1 , wherein the structure is a semiconductor wafer formed with the pattern of vias.

13. The system according to claim 1 , wherein said imaging system is further configured for performing a bright field imaging scheme for said at least region of the structure, and, generating a bright-field image, said analyzer module being configured for analyzing the pixels brightness by comparing the dark-field image with the bright-field image.

14. The method according to claim 1 , wherein the geometry of the grooves has the high aspect ratio of at least 6.

15. The method according to claim 1 , wherein the predetermined dark-field imaging scheme comprises a cross-polarization scheme.

16. A method for inspecting patterned structures comprising narrow grooves having high aspect ratio geometry for detecting defective grooves in the patterned structure, the method comprising:
imaging at least a region of the structure, said imaging comprising performing at least dark-field imaging said at least region of the structure including a plurality of the grooves having high aspect ratio geometry with a dark-field imaging scheme comprising illumination of said at least region of the structure with normal incidence mode to detect light returned from inside of the grooves in said region, and generating data indicative of a dark-field image of said at least region of the structure;
processing said data indicative of the dark-field image, said processing comprising analyzing pixels brightness within the image, and upon identifying a condition that brightness of the pixels corresponding to at least one of said grooves in said dark-field image is lower than nominal brightness by a predetermined factor, generating output data indicative of existence of at least one defective groove in said at least region of the structure.

17. The method according to claim 16 , wherein the geometry of the grooves has the high aspect ratio of at least 6.

18. The method according to claim 16 , wherein the predetermined dark-field imaging scheme further comprises a cross-polarization scheme.

19. The method according to claim 16 , wherein the structure is a semiconductor wafer formed with the pattern of grooves.

20. An inspection system for inspecting structures having a pattern formed by an array of narrow grooves having high aspect ratio geometry for detecting defective grooves, the system comprising:
an imaging system configured and operable for imaging the structure by applying a dark-field imaging scheme to at least a region of the structure comprising a plurality of the grooves by illuminating said at least region and detecting light returned from inside of the grooves, and generating data indicative of a dark-field image of said at least region of the structure;
a control unit configured for data communication with the imaging system to receive said data indicative of the dark-field image of said at least region of the structure, the control unit comprising a data processor configured to process the dark-field image to identify one or more defective groves among the one or more of the narrow grooves in said at least region of the structure being imaged, the data processor comprising an analyzer module configured to analyze pixels brightness within said data indicative of the dark-field image, and upon identifying a condition that brightness of the pixels corresponding to at least one of said grooves in said dark-field image is lower than nominal brightness by a predetermined factor, generating output data indicative of existence of at least one defective groove in said at least region of the structure.

21. The system according to claim 20 , wherein said imaging system comprises a polarization unit configured and operable with a cross-polarization scheme; said imaging system is configured to perform said dark-field imaging scheme using normal incidence mode.

22. The system according to claim 20 , wherein the nominal brightness is defined by at least one of the following: the nominal brightness is defined by brightness of pixels in said dark-field image corresponding to other grooves in said pattern; and the nominal image brightness is defined by brightness of pixels corresponding to grooves in a reference dark-field image.

Assignees

• Nova Measuring Instr Ltd

Inventors

• Barak Gilad
• Dotan Elad
• Belleli Alon

Classifications

• G01N21/9501

  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

• G01N2021/8825

  Separate detection of dark field and bright field · CPC title

• G01N2021/8848

  Polarisation of light · CPC title

• G06T2207/10056

  Microscopic image · CPC title