DEFECT INSPECTION METHOD AND DEFECT INSPECTION APPARATUS
A method, of inspecting a semiconductor device for defects, includes: acquiring an observation image of the semiconductor device, the observation image including a defect inspection object area which has a repetitive pattern; superposing a reference on the observation image thereby to form a test-mule image representing a version of the observation image in which signals have been removed from a given area, including the defect inspection area, masked with the reference ; and inspecting for defects in the test-mule image thereby to identify corresponding defects in the observation image.
1 . A method of inspecting a semiconductor device for defects, the method comprising:
acquiring an observation image of the semiconductor device, the observation image including a defect inspection object area which has a repetitive pattern;
superposing a reference on the observation image thereby to form a test-mule image representing a version of the observation image in which signals have been removed from a given area, including the defect inspection area, masked with the reference; and
inspecting for defects in the test-mule image thereby to identify corresponding defects in the observation image.
2 . The method as defined in claim 1 , further comprising:
working the observation image so as to extract a worked image;
aligning the worked image and a reference image;
performing pattern matching between the worked image and the reference image so as to determine a desired registration relationship there between; and
obtaining positional information on the basis of the desired registration relationship;
wherein the superposing is performed on the basis of the positional information.
3 . The method as defined in claim 1 , wherein the superposing obtains the test-mule image by forming a differential image between corresponding parts of repetitive patterns in the reference and the observation image.
4 . The method as defined in claim 1 , wherein the inspecting uses a voltage contrast.
5 . The method as defined in claim 1 , wherein the defect inspection object area having the repetitive pattern is an area where contact plugs are embedded in an insulating film, and the reference image masks the contact plugs.
6 . The method as defined in claim 1 , wherein the defect inspection object area having the repetitive pattern is a MOS transistor area where gate electrodes are formed over active regions, and the reference image masks the active regions or the gate electrodes.
7 . The method as defined in claim 1 , wherein the acquiring an observation image acquires the same from an electron microscope.
8 . The method as defined in claim 1 , wherein the removed signals represent seams.
9 . The method as defined in claim 1 , further comprising: selecting as the reference image a member from the group consisting of a pattern which masks contact plugs, a pattern which masks active regions of a MOS transistor area, and a pattern which masks gate electrodes of the MOS transistor area.
10 . An apparatus to inspect for defects in a semiconductor device, the apparatus comprising:
an imager to obtain an observation image of the semiconductor device, the observation image including a defect inspection object area which has a repetitive pattern;
an image masking device to work the observation image so as to extract a worked image, to superpose a reference image on the observation image thereby to form a test-mule image representing a version of the observation image in which signals have been removed from a given area, including the defect inspection area, masked with the masking pattern;
an image comparison device to inspect defects in the test-mule image thereby to identify corresponding defects in the observation image.
11 . The apparatus as defined in claim 10 , wherein:
said imager extracts a worked image for use in pattern matching for position alignment from the observation image; and
said image masking device performs pattern matching between the worked image and the reference image so as to determine a desired registration relationship there between, obtains positional information on the basis of the desired registration relationship; and superposes on the basis of the positional information.
12 . The apparatus as defined in claim 10 , wherein said image comparison device forms a differential image and detects a voltage contrast.
13 . The apparatus as defined in claim 10 , wherein the reference image is a member selected from the group consisting of a pattern which masks contact plugs, a pattern which masks active regions of a MOS transistor area, and a pattern which masks gate electrodes of the MOS transistor area.
14 . The apparatus as defined in claim 10 , wherein the imager is an electron microscope.
15 . The apparatus as defined in claim 10 , further comprising:
a memory to store the masking pattern; and
a controller to provide the reference to said image masking device, and to receive defect information from said image comparison device.
16 . The apparatus as defined in claim 10 , wherein the removed signals represent seams.