Circuit pattern inspection method and apparatus

• US 6,898,305 B2
• Filed: 02/22/2001
• Issued: 05/24/2005
• Est. Priority Date: 02/22/2001
• Status: Expired due to Term

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Miyai, Hiroshi, Watanabe, Masahiro, Hiroi, Takashi, Nozoe, Mari, Tanaka, Maki, Kuni, Asahiro, Shishido, Chie, Nara, Yasuhiko
• Primary Examiner(s): Mehta, Bhavesh M.
• Assistant Examiner(s): Chawan, Sheela
• Application Number:
  US09/791,911
• Publication Number:
  US 20020114506A1
• Time in Patent Office: 1,552 Days
• Field of Search: 382/149, 382/141, 382/278, 382/164, 382/168, 382/151, 382/205, 382/147, 382/172, 382/155, 250/310, 250/307, 250/208.1, 250/554, 324/210, 731/05, 731/173, 356/601, 356/399, 356/394
• US Class Current: 382/149
• CPC Class Codes: G01N 21/95684 Patterns showing highly reflecting parts, e.g. metallic elements
• CPC Class Codes: G06T 2207/10056 Microscopic image
• CPC Class Codes: G06T 2207/30148 Semiconductor; IC; Wafer
• CPC Class Codes: G06T 7/001 using an image reference approach

Abstract

The present invention provides techniques, including a method and system, for inspecting for defects in a circuit pattern on a semi-conductor material. One specific embodiment provides a trial inspection threshold setup method, where the initial threshold is modified after a defect analysis of trial inspection stored data. The modified threshold is then used as the threshold in actual inspection.

Claims

1. A method for inspecting a specimen, comprising:

setting a first threshold value;

detecting an image of a specimen;

comparing the image detected by said detecting to a reference image;

extracting from the comparing, a defect candidate using the first threshold value;

storing an information of the defect candidate to a memory;

setting a second threshold value; and

extracting a defect from the defect candidate using the stored information and the second threshold value,

wherein said second threshold value is determined by using information of distribution of defect candidates extracted from the comparing by using the first threshold value.

2. A method of inspecting a specimen according to claim 1, wherein the information of the defect candidate stored in the memory includes at least one of the following:

a defect candidate position, a defect candidate area, a defect candidate x and y projection size, a maximum difference between the detected image and the reference image, a defect texture, or a reference texture.

3. A method of inspecting a specimen according to claim 1, wherein the information of the defect candidate stored in the memory includes an image of the defect candidate.

4. The method of claim 1 wherein the specimen includes a circuit pattern on a semiconductor wafer.

5. A method for inspecting a circuit pattern on a semiconductor material comprising:

setting an initial threshold value;

detecting an image of a specimen;

generating a difference image by comparing said image of a specimen detected by said detecting and a reference image;

extracting defect candidate by thresholding said difference image, wherein said thresholding uses said initial threshold value;

storing said image of a specimen in which said defect candidate is extracted by using said initial threshold value and a reference image in a memory;

modifying said initial threshold value to a modified threshold value by using information on distribution of defect candidates extracted from the comparing by using the initial threshold value; and

detecting a defect in said image stored in said memory using said modified threshold value.

6. A method according to the claim 5, further comprising displaying information on distribution of defect candidates extracted from the comparing by using the initial threshold value.

7. A method according to the claim 5, further comprising displaying in a map form a distribution of defect detected in said detecting by using the modified threshold value.

8. A method according to the claim 7, further comprising displaying an image of a defect candidate stored in the memory by designating a location on the map.

9. A method according to the claim 5, wherein in modifying said initial threshold value, said information includes a distribution of difference value between said image of a specimen and said reference image stored in said memory.

10. A method for inspecting a circuit pattern on a semiconductor material comprising:

setting an initial threshold value;

detecting an image of a specimen;

comparing said image of a specimen detected by said detecting and a reference image and detecting a difference value between said image of a specimen and the reference image;

extracting defect candidates from said detected difference value by using said initial threshold value;

storing an image of a defect candidate extracted in said extracting and a reference image thereof in a memory;

displaying on a screen a distribution of defect candidates extracted in said extracting; and

modifying said initial threshold value by using information displayed on said screen and the images stored in the memory.

11. A method according to the claim 10, wherein in said displaying, a map of the distribution of defect candidates extracted in said extracting is displayed on the screen.

12. A method according to the claim 11, further comprising displaying an image of a defect candidate stored in the memory by designating a location on the map.

13. A method according to the claim 10, wherein in modifying said initial threshold value, said information includes a distribution of said detected difference value between said image of a defect candidate and said reference image stored in said memory.

14. A method for inspecting a circuit pattern on a semiconductor material comprising:

setting a threshold value for inspecting a circuit pattern on a semiconductor material with an inspecting apparatus; and

inspecting a circuit pattern on a semiconductor material with said inspecting apparatus,

wherein setting the threshold value comprises;

setting an initial threshold value for inspecting a circuit pattern on a semiconductor material with said inspecting apparatus;

detecting an image of the circuit pattern with a detecting unit of said inspecting apparatus;

generating a difference image by comparing an image of the circuit pattern detected by the detecting and a reference image;

extracting defect candidate by comparing said difference image with said initial threshold value;

storing said image of a specimen in which said defect candidate is extracted by using said initial threshold value and a reference image in a memory;

modifying said initial threshold value by using information of distribution of defect candidates extracted from the comparing by using the initial threshold value; and

setting a modified initial threshold modified by said modifying for inspecting a circuit pattern.

15. An apparatus for inspecting a specimen comprising:

a first memory to store a first threshold value;

a detecting unit to detect an image of a specimen;

a comparator to compare the image detected by said detecting unit to a reference image;

a first processor to extract a defect candidate from an output of said comparator by using the first threshold value;

a second memory to store information of the defect candidate extracted by said extractor;

a display to display said information of the defect candidate;

a third memory to store a second threshold value; and

a second processor to extract a defect from the defect candidate by using the information stored in said second memory and the second threshold value stored in said third memory,

wherein said second threshold value is determined by using information of distribution of defect candidates extracted from comparing said image detected to said reference image using the first threshold value.

16. An apparatus according to the claim 15, wherein said detecting unit detects a SEM image of a specimen.

17. An apparatus according to the claim 15, wherein said detecting unit detects an optical image of a specimen.

18. An apparatus according to the claim 15, wherein said detecting memory stores an image detected by said detecting unit in which said defect candidate is extracted by using said first threshold value and a reference image.

19. An apparatus according to the claim 15, wherein said display further displays information of the defect extracted by said second processor.

20. An apparatus for inspecting a specimen comprising:

a first memory to store an initial threshold value;

a detecting unit to detect an image of a specimen;

an image processor to generate a difference image by comparing said image of the specimen detected by said detecting unit and a reference image;

a defect image processor to extract defect candidate by thresholding said difference image generated by said image processor using said initial threshold value stored in said first memory;

a display to display said information of the defect candidate extracted by said defect image processor;

a second memory to store said image of a specimen in which said defect candidate is extracted by using said initial threshold value and the reference image;

a third memory to store a modified threshold value which is modified from said initial threshold value by using information of distribution of defect candidates extracted by said defect image processor using the first threshold value stored in said first memory; and

a processor to detect a defect in said image stored in said second memory by using said modified threshold stored in said third memory.

21. An apparatus according to the claim 20, wherein said detecting unit detects a SEM image of a specimen.

22. An apparatus according to the claim 20, wherein said detecting unit detects an optical image of a specimen.

23. An apparatus according to the claim 20, wherein said second memory stores an image detected by said detecting unit in which said defect candidate is extracted by using said first threshold value and a reference image.

24. An apparatus according to the claim 20, wherein said display further displays information of the defect extracted by said second processor.