Inspection apparatus and inspection method

An inspection apparatus comprising:

• a wafer stage for carrying a wafer;
• an illumination module which irradiates an inspection beam on the wafer carried on said wafer stage;
• a detection module which detects scattering rays or reflection rays from the wafer on said wafer stage and outputs an image signal;
• a coordinates control module which stores information about the arrangement of individual inspection areas on said wafer;
• a comparison module which compares an image signal of an inspection area detected by said detection module with an image signal of corresponding pixels of a reference area, also detected by said detection module, to detect a difference between the two image signals;
• an imperfect area recognition module which recognizes, based on the inspection area arrangement information stored in said coordinates control module, an imperfect inspection area interfering with a wafer edge;
• a filter module which excludes from valid data, when the imperfect inspection area interfering with the wafer edge is inspected, inspection data lying in said imperfect inspection area externally of the wafer edge;
• a foreign matter decision module which decides the presence or absence of a foreign matter by comparing a difference between image signals of mutually corresponding pixels of the inspection area and the reference area with a threshold value;
• and
• a threshold value operation module which computes the threshold value based on a statistical value of image signals of mutually corresponding pixels of individual inspection areas.

An inspection method comprising the steps of:

• mutually comparing image signals of mutually corresponding pixels of an inspection area and a reference area which are both on a wafer to detect a difference between the two signals;
• recognizing, based on information about the arrangement of inspection areas, an imperfect inspection area interfering with a wafer edge;
• excluding from valid data, when inspecting an imperfect inspection area interfering with the wafer edge, inspection data lying inside the inspection area externally of the wafer edge;
• and
• comparing the difference between the image signals of mutually corresponding pixels of the inspection area and the reference area with a threshold value to decide the presence or absence of a foreign matter,
• wherein the threshold value is computed based on a statistical value of image signals of mutually corresponding pixels of individual inspection areas.

An inspection method comprising the steps of:

• recognizing, based on information about the arrangement of inspection areas on a wafer, an imperfect area interfering with a wafer edge;
• determining that the imperfect area interfering with the wafer edge is an invalid area;
• and
• deciding a degree of validity of an inspection area from a difference between an image signal of the whole inspection area and an image signal of a whole reference area.