Method and apparatus for inspecting pattern defects

• US 7,388,979 B2
• Filed: 11/22/2004
• Issued: 06/17/2008
• Est. Priority Date: 11/20/2003
• Status: Expired due to Fees

• Current Assignee: Hitachi High-Technologies Corporation (Hitachi, Ltd.)
• Original Assignee: Hitachi High-Technologies Corporation (Hitachi, Ltd.)
• Inventors: Sakai, Kaoru, Okabe, Takafumi, Maeda, Shunji
• Primary Examiner(s): Desire; Gregory M
• Application Number:
  US10/992,759
• Publication Number:
  US 20050147287A1
• Time in Patent Office: 1,303 Days
• Field of Search: 348/87, 348/92, 348/126, 356/237.4, 356/237.5, 382/144, 382/149, 382/195, 382/218, 382/224, 700/121
• US Class Current: 382/149
• CPC Class Codes: G01N 21/9501 Semiconductor wafers manufacturing processes per se of semiconductor devices implementing a measuring step H01L22/10
• CPC Class Codes: G01N 21/95607 using a comparative method
• CPC Class Codes: G06T 2207/30148 Semiconductor; IC; Wafer
• CPC Class Codes: G06T 7/001 using an image reference approach

Abstract

The present invention relates to a pattern defect inspection method and apparatus that reveal ultramicroscopic defects on an inspection target in which ultramicroscopic circuit patterns are formed, and inspect the defects with high sensitivity and at a high speed. The present invention provides a pattern inspection apparatus for comparing the images of corresponding areas of two formed patterns that should be identical with each other, and judging any mismatched image area as a defect. The pattern inspection apparatus includes means for performing an image comparison process on a plurality of areas in a parallel manner. Further, the pattern inspection apparatus also includes means for converting the gradation of the image signals of compared images in each of a plurality of different processes. Therefore, the present invention can properly detect defects even if the same patterns of compared images differ in brightness.

Claims

1. An apparatus for inspecting pattern defects, the apparatus comprising:

an image acquisition means which picks up an image of an inspection target, acquires a detected image signal and a reference image signal, and stores the acquired signals in an image memory;

a defect candidate extraction unit which performs a defect candidate extraction process by comparing the detected image signal with the reference image signal, which are read from said image memory; and

a defect detection unit which performs a defect detection process and a defect classification process based on a partial image containing a defect candidate that is extracted by said defect candidate extraction unit,

wherein the processes performed by said defect candidate extraction unit and/or said defect detection unit is performed asynchronously with an image acquisition process that is performed by said image acquisition means.

2. The apparatus for inspecting pattern defects according to claim 1, wherein said defect candidate extraction unit performs a defect candidate extraction process about a plurality of areas on said inspection target in a parallel manner.

3. The apparatus for inspecting pattern defects according to claim 1, wherein said defect detection unit performs a defect detection process and a defect classification process in a parallel manner based on a plurality of the partial images containing the defect candidate.

4. The apparatus for inspecting pattern defects according to claim 1, wherein said defect candidate extraction unit comprises:

a positional displacement detection section which calculates amount of positional displacement between the detected image signal and the reference image signal for each field unit;

a brightness correction section which calculates amount of signal correction for adjusting brightness difference between the detected image signal and the reference image signal, for each area; and

an image comparison section which performs a brightness comparison at corresponded positions between the detected image signal and the reference image signal by using the positional displacement amount, which is calculated for the each field unit by said positional displacement detection section, and the signal correction amount, which is calculated for the each area by said brightness correction section.

5. The apparatus for inspecting pattern defects according to claim 1, wherein said defect detection unit comprises a comparative collation section, which detects defects only by collating feature amount of the defect candidate calculated by said defect candidate extraction unit with feature amount of the defect candidate calculated by said defect detection unit.

6. An apparatus for inspecting pattern defects, the apparatus comprising:

an image acquisition means which picks up an image of an inspection target, acquires a detected image signal and a reference image signal, and stores the acquired signals in an image memory;

a defect candidate extraction unit which extracts defect candidate by comparing the detected image signal with the reference image signal, which are read from said image memory, and performs a process for storing in a memory a partial image containing the extracted defect candidate; and

a defect detection unit which performs a defect detection process and a defect classification process based on a partial image containing a defect candidate that is read from said memory,

wherein the process performed by said defect detection unit, the process performed by said defect candidate extraction unit, and an image acquisition process that is performed by said image acquisition means are performed asynchronously with each other.

7. The apparatus for inspecting pattern defects according to claim 6, wherein said defect candidate extraction unit performs a defect candidate extraction process about a plurality of areas on said inspection target in a parallel manner.

8. The apparatus for inspecting pattern defects according to claim 6, wherein said defect detection unit performs a defect detection process and a defect classification process in a parallel manner based on a plurality of partial images containing the defect candidate.

9. The apparatus for inspecting pattern defects according to claim 6, wherein said defect candidate extraction unit comprises:

a positional displacement detection section which calculates amount of positional displacement between the detected image signal and the reference image signal for each field unit;

a brightness correction section which calculates amount of signal correction for adjusting brightness difference between the detected image signal and the reference image signal, for each area; and

an image comparison section which performs a brightness comparison at corresponded positions between the detected image signal and the reference image signal by using the positional displacement amount calculated for the each field unit by said positional displacement detection section, and the signal correction amount calculated for the each area by said brightness correction section.

10. The apparatus for inspecting pattern defects according to claim 6, wherein said defect detection unit comprises a comparative collation section, which detects defects only by collating feature amount of the defect candidate calculated by said defect candidate extraction unit, with feature amount of the defect candidate calculated by said defect detection unit.

11. A method for inspecting pattern defects, the method comprising:

an image acquisition step of picking up the image of an inspection target, acquiring a detected image signal and a reference image signal, and storing the acquired signals in an image memory;

a defect candidate extraction step of performing a defect candidate extraction process by comparing the detected image signal with the reference image signal, which are read from said image memory; and

a defect detection step of performing a defect detection process and a defect classification process based on a partial image containing a defect candidate that is extracted in said defect candidate extraction step,

wherein the processes performed in said defect candidate extraction step and/or said defect detection step are performed asynchronously with an image acquisition process that is performed in said image acquisition step.

12. The method for inspecting pattern defects according to claim 11, wherein said defect candidate extraction step performs a defect candidate extraction process about a plurality of areas on said inspection target in a parallel manner.

13. The method for inspecting pattern defects according to claim 11, wherein said defect detection step performs a defect detection process and a defect classification process in a parallel manner based on a plurality of partial images containing the defect candidate.

14. The method for inspecting pattern defects according to claim 11, wherein said defect candidate extraction step comprises:

a positional displacement detection step of calculating amount of positional displacement between the detected image signal and the reference image signal for each field unit;

a brightness correction step of calculating amount of signal correction for adjusting brightness difference between the detected image signal and the reference image signal, for each area; and

an image comparison step of performing a brightness comparison at corresponded positions between the detected image signal and the reference image signal by using the positional displacement amount, which is calculated for the each field unit in said positional displacement detection step, and the signal correction amount, which is calculated for the each area in said brightness correction step.

15. The method for inspecting pattern defects according to claim 11, wherein said defect detection step automatically sets threshold values for performing the defect detection process and the defect classification process in accordance with feature amount of the partial image containing the defect candidate.

16. The method for inspecting pattern defects according to claim 11, wherein said defect detection step detects defects only by collating feature amount of the defect candidate calculated in said defect candidate extraction step with feature amount of the defect candidate calculated in said defect detection step.

17. A method for inspecting pattern defects, the method comprising:

an image acquisition step of acquiring a detected image signal and a reference image signal from an inspection target, and storing the acquired signals in an image memory;

a defect candidate extraction step of extracting defect candidates by comparing the detected image signal with the reference image signal, which are read from said image memory, and performing a process for storing in a memory a partial image containing the extracted defect candidate; and

a defect detection step of performing a defect detection process and a defect classification process based on the partial image containing the defect candidate that is read from said memory,

wherein the process performed in said defect detection step, the process performed in said defect candidate extraction step, and an image acquisition process that is performed in said image acquisition step are performed asynchronously with each other.

18. The method for inspecting pattern defects according to claim 17, wherein said defect candidate extraction step performs a defect candidate extraction process about a plurality of areas on said inspection target in a parallel manner.

19. The method for inspecting pattern defects according to claim 17, wherein said defect detection step performs a defect detection process and a defect classification process in a parallel manner based on a plurality of partial images containing the defect candidate.

20. The method for inspecting pattern defects according to claim 17, wherein said defect candidate extraction step comprises:

a positional displacement detection step of calculating amount of positional displacement between the detected image signal and the reference image signal for each field unit;

a brightness correction step of calculating amount of signal correction for adjusting brightness difference between the detected image signal and the reference image signal, for each area; and

an image comparison step of performing a brightness comparison at corresponded positions between the detected image signal and the reference image signal by using the positional displacement amount, which is calculated for the each field unit in said positional displacement detection step, and the signal correction amount, which is calculated for the each area in said brightness correction step.

21. The method for inspecting pattern defects according to claim 17, wherein said defect detection step automatically sets threshold values for performing the defect detection process and the defect classification process in accordance with feature amount of the partial image containing the defect candidate.

22. The method for inspecting pattern defects according to claim 17, wherein said defect detection step detects defects only by collating feature amount of the defect candidate calculated in said defect candidate extraction step with feature amount of the defect candidate calculated in said defect detection step.