Image Alignment Method, Comparative Inspection Method, and Comparative Inspection Device for Comparative Inspections

• US 20070133863A1
• Filed: 10/10/2006
• Published: 06/14/2007
• Est. Priority Date: 06/15/2000
• Status: Abandoned Application

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Sakai, Kaoru, Okabe, Takafumi, Maeda, Shunji
• Application Number:
  US11/548,259
• Publication Number:
  US 20070133863A1
• Time in Patent Office: Days
• US Class Current: 382/151
• CPC Class Codes: G01N 21/95607 using a comparative method
• CPC Class Codes: G03F 1/84 Inspecting
• CPC Class Codes: G06T 2207/30148 Semiconductor; IC; Wafer
• CPC Class Codes: G06T 7/001 using an image reference approach
• CPC Class Codes: G06T 7/32 using correlation-based methods

Abstract

The present invention provides a high-precision alignment method, device and code for inspections that compare an inspection image with a reference image and detect defects from their differences. In one embodiment an inspection image and a reference image are divided into multiple regions. An offset is calculated for each pair of sub-images. Out of these multiple offsets, only the offsets with high reliability are used to determine an offset for the entire image. This allows high-precision alignment with little or no dependency on pattern density or shape, differences in luminance between images, and uneven luminance within individual images. Also, detection sensitivity is adjusted as necessary by monitoring alignment precision.

Claims

1. An apparatus for inspecting a specimen, comprising.

an image detection means for detecting an image of a specimen on which plural patterns are formed;

an offset determining means for determining offsets between said detected image and a reference image stored in a memory by selecting patterns among said plural patterns which are advantageous to determine the offsets;

an alignment means for aligning said detected image and said reference image using said offsets determined by the offset determining means; and

a comparing means for comparing said aligned inspection image and said reference image to detect a defect candidate; and

a feature extracting unit for extracting a feature of said defect candidate.

2. An apparatus according to the claim 1, wherein said offset determining means calculates offsets between the patterns of said detected image and the patterns of said reference image by evaluating correlations between shift amount in X-direction and shift amount in Y-direction and a reliability measurement over portions of a full image of the pattern.

3. An apparatus according to the claim 2, wherein said offset determining means calculates offsets between plural images divided from said detected image and plural images divided from said reference image in parallel.

4. An apparatus for inspecting a specimen, comprising.

an image detection means having an illuminating unit to illuminate a specimen on. which patterns are formed with light and a detecting unit to detect an image of the specimen;

a processor which determines an offset between said detected image and a reference image, correcting the offset between said detected image and a reference by using a data of said determined offset, compares said detected image and said reference image whose offset is corrected to detect a defect candidate, and extracts a feature of said defect candidate; and

an output means for outputting information on said extracted feature of said defect candidate,

wherein said processor determines said offset between said detected image and a reference image by selecting patterns among said plural patterns which are advantageous to determine the offset by evaluating correlations between shift amount in X-direction and shift amount in Y-direction and a reliability measurement over portions of a full image of the pattern.

5. An apparatus according to the claim 5, wherein said processor calculates offsets between plural images divided from said detected image and plural images divided from said reference image in parallel.

6. A method for inspecting a specimen, comprising:

detecting an image of a specimen on which plural patterns are formed;

determining an offset between said detected image and a reference image stored in a memory by selecting patterns among said plural patterns which are advantageous to determine the offsets;

aligning said detected image and said reference image using said determined offset;

comparing said aligned inspection image and said reference image to detect a defect candidate; and

extracting a feature of said defect candidate.

7. A method according to the claim 6, wherein in the step of determining an offset, said offset between the patterns of said detected image and the patterns of said reference image is determined by evaluating correlations of shift amount between the patterns of said detected image and the patterns of said reference image in X-direction and Y-direction and a reliability measurement over portions of a full image of the pattern.

8. A method according to the claim 7, wherein said offsets between plural images divided from said detected image and plural images divided from said reference image are calculated in parallel.

9. A method according to the claim 8, wherein in the step of aligning, said plural images divided from said detected image and plural images divided from said reference image are aligned in parallel, and in the step of said comparing, said aligned plural images divided from said detected image and plural images divided from said reference image are compared in parallel.

10. A method for inspecting a specimen, comprising.

detecting an image of a specimen on which patterns are formed;

processing said detected image for detecting defect candidate by determining an offset between said detected image and a reference image, aligning said detected image and said reference image using a data of said calculated offset;

comparing said aligned inspection image and said reference image to detect a defect candidate, and extracting a feature of said defect candidate; and

outputting information on said extracted feature of said defect candidate,

wherein in the step of processing, said offset is determined by selecting patterns among said plural patterns which are advantageous to determine the offset by evaluating correlations between shift amount in X-direction and shift amount in Y-direction and a reliability measurement over portions of a full image of the pattern.