Image capturing device and inspection apparatus and inspection method

Abstract

An image capturing device comprising, a light source configured to emit light having a predetermined wavelength, a polarization beamsplitter configured to receive the light from the light source, a Faraday rotator configured to rotate a polarization plane of the light via the polarization beamsplitter by changing the intensity of the magnetic field, an objective lens configured to illuminate an inspection target with the light transmitted through the Faraday rotator and a sensor configured to capture an optical image of the inspection target by causing the light reflected by the inspection target to be incident through the objective lens, the Faraday rotator, and the polarization beamsplitter.

1 - 20  (canceled) 
     
     
         21 . An image capturing device comprising:
 a light source configured to emit light having a predetermined wavelength;   a polarization beam splitter configured to receive the light from the light source;   a Faraday rotator configured to rotate a polarization plane of the light forwarded by the polarization beam splitter by a rotation angle, the rotation angle being accommodated to a pattern formed in a target for inspection;   an objective lens configured to illuminate the target with the light having the polarization plane rotated by the Faraday rotator; and   a sensor configured to capture an optical image of the inspection target by causing the light reflected by the inspection target to be incident through the objective lens, the Faraday rotator, and the polarization beam splitter,   wherein the sensor captures the optical image of the target from the reflected light which is generated by illuminating the inspection target with the light having the polarization plane rotated by the Faraday rotator by the accommodated rotation angle.   
     
     
         22 . The image capturing device according to  claim 21 , wherein
 the Faraday rotator includes an optical material that transmits the light, and   the magnetic field is applied to the optical material by one selected from a group consisting of an electromagnet, a permanent magnet, and a combination of the electromagnet and permanent magnet.   
     
     
         23 . The image capturing device according to  claim 22 , wherein the sensor captures the optical image of the target from the reflected light generated by illumination of the light having the polarization plane with the rotation angle accommodated by changing the intensity of a magnetic field, by using the one selected from the group or changing the thickness of the optical material. 
     
     
         24 . The image capturing device according to  claim 23 , wherein
 one permanent magnet selected from a plurality of permanent magnets having different intensities of a magnetic field is provided for the Faraday rotator, and   the rotation angle of the Faraday rotator is accommodated by selecting the permanent magnet from the plurality of permanent magnets.   
     
     
         25 . The image capturing device according to  claim 23 , wherein
 the Faraday rotator includes an electromagnet configured to apply different intensities of a magnetic field to the optical material, and   the image capturing device further comprises a rotation angle controller configured to control the intensity of the electromagnet applied to the optical material of the Faraday rotator to accommodate the rotation angle of the Faraday rotator.   
     
     
         26 . The image capturing device according to  claim 23 , wherein
 the Faraday rotator includes an electromagnet with a coil through which an electric current passes to generate the magnetic field of the electromagnet, and   the rotation angle of the Faraday rotator is accommodated by controlling the current.   
     
     
         27 . The image capturing device according to  claim 22 , wherein
 one selected from a plurality of optical materials having different thicknesses is provided for the Faraday rotator, and   the rotation angle of the Faraday rotator is accommodated by selecting the one of the plurality of optical materials.   
     
     
         28 . The image capturing device according to  claim 21 , further comprising:
 a half-wavelength plate arranged between the polarization beam splitter and the target, wherein the half-wavelength plate changes a polarization direction of the light with which the inspection target is illuminated.   
     
     
         29 . The image capturing device according to  claim 28 , wherein the half-wavelength plate is arranged between the polarization beam splitter and the Faraday rotator. 
     
     
         30 . The image capturing device according to  claim 28 , wherein the half-wavelength plate is arranged between the Faraday rotator and the target. 
     
     
         31 . The image capturing device according to  claim 28 , wherein
 the half-wavelength plate includes a rotation mechanism, and   the rotation mechanism changes the polarization direction of the light illuminating the target by changing an angle of the half-wavelength plate by the rotation mechanism.   
     
     
         32 . The image capturing device according to  claim 21 ,
 wherein the sensor captures the optical image of a pattern formed in the target which is smaller than a resolution limit defined by the predetermined wavelength of the light from the light source and a numerical aperture of the objective lens.   
     
     
         33 . The image capturing device according to  claim 32 , wherein the pattern formed in the target has a short-circuit defect and an open-circuit defect. 
     
     
         34 . The image capturing device according to  claim 21 , further comprising an image processor configured to obtain a gradation value in each pixel of the optical image,
 wherein the image processor obtains the accommodated rotation angle of the Faraday rotator by:   (1) minimizing a standard deviation of the gradation value, or   (2) minimizing a value which is obtained by dividing the standard deviation of the gradation values of a plurality of optical images captured by changing the rotation angle, by a square root of an average gradation value obtained from the gradation value.