POLARIZED IMAGE ACQUISITION APPARATUS, PATTERN INSPECTION APPARATUS, POLARIZED IMAGE ACQUISITION METHOD, AND PATTERN INSPECTION METHOD

• US 20180364472A1
• Filed: 06/01/2018
• Published: 12/20/2018
• Est. Priority Date: 06/19/2017
• Status: Active Grant

• Current Assignee: NuFlare Technology, Inc. (Toshiba Corporation)
• Original Assignee: NuFlare Technology, Inc. (Toshiba Corporation)
• Inventors: Ogawa, Riki
• Granted Patent: US 10,444,487 B2
• Time in Patent Office: Days
• CPC Class Codes: G02B 21/0092 Polarisation microscopes
• CPC Class Codes: G02B 21/02 Objectives
• CPC Class Codes: G02B 21/26 Stages; Adjusting means therefor
• CPC Class Codes: G02B 21/367 providing an output produced by processing a plurality of individual source images, e.g. image tiling, montage, composite images, depth sectioning, image comparison
• CPC Class Codes: G02B 27/126 The splitting element being a prism or prismatic array, including systems based on total internal reflection
• CPC Class Codes: G02B 27/286 for controlling or changing the state of polarisation, e.g. transforming one polarisation state into another G02B5/3083 takes precedence; light guide coupling means utilising polarising elements G02B6/34
• CPC Class Codes: G06T 2207/10004 Still image; Photographic image
• CPC Class Codes: G06T 2207/30148 Semiconductor; IC; Wafer
• CPC Class Codes: G06T 7/001 using an image reference approach

Abstract

A polarized image acquisition apparatus includes a rotatable diaphragm to restrict a passage region of light passed through an objective lens to two regions mutually opposite across the central axis in 4n equal regions divided rotationally symmetrically in the plane orthogonal to the traveling direction of the light passed through the objective lens, and to change the angle of the passage region so that each two regions of the 4n equal regions become passage regions in order; and a rotating half-wave plate to convert, for each angle of the passage region, a P-polarized component passed through the diaphragm, in the same direction as the angle of the passage region, and an S-polarized component passed through the diaphragm, orthogonal to the angle of the passage region, into polarized waves in orthogonal first and second directions.

Claims

1. A polarized image acquisition apparatus comprising:

a stage configured to be movable and to mount thereon a mask substrate for exposure on which a pattern is formed;

an objective lens configured to receive a transmitted light having passed through the mask substrate;

a diaphragm configured to be rotatable, to restrict a passage region of a light having passed through the objective lens to two regions opposite to each other with respect to a central axis in 4n equal regions divided rotationally symmetrically in a plane orthogonal to a traveling direction of the light having passed through the objective lens, and to change an angle of the passage region so that each the two regions of the 4n equal regions become passage regions in order;

a rotating half-wave plate configured to convert, for each of the angle of the passage region, a P-polarized component having passed through the diaphragm and being in same direction as the angle of the passage region and an S-polarized component having passed through the diaphragm and being in a direction orthogonal to the angle of the passage region into a polarized wave in a first direction and a polarized wave in a second direction, where the first and second directions have been set previously and are orthogonal to each other;

a Rochon prism configured to separate a trajectory of the polarized wave in the first direction from a trajectory of the polarized wave in the second direction;

an image forming lens configured to focus and form an image of the polarized wave in the first direction having passed through the Rochon prism, at an image formation position, and an image of the polarized wave in the second direction having passed through the Rochon prism, at an other image formation position;

a mirror configured to reflect the polarized wave in the second direction, at the other image formation position of the polarized wave in the second direction which is different from the image formation position of the polarized wave in the first direction;

a first image sensor configured to capture an optical image of a polarized wave of the P-polarized component and an optical image of a polarized wave of the S-polarized component, as an optical image of the polarized wave in the first direction, while replacing the optical image of the polarized wave of the P-polarized component and the optical image of the polarized wave of the S-polarized component with each other depending on the angle of the passage region of the diaphragm; and

a second image sensor configured to capture an optical image of a polarized wave of the S-polarized component and an optical image of a polarized wave of the P-polarized component, as an optical image of the polarized wave in the second direction, while replacing the optical image of the polarized wave of the S-polarized component and the optical image of the polarized wave of the P-polarized component with each other depending on the angle of the passage region of the diaphragm.

2. The apparatus according to claim 1, further comprising:

a combining processing circuitry configured to combine optical images of 2n polarized waves of the P-polarized component and optical images of 2n polarized waves of the S-polarized component which have been image-captured for the each of the angle of the passage region; and

a comparison processing circuitry configured to compare a first die image of a first die, where the optical images of the 2n polarized waves of the P-polarized component and the optical images of the 2n polarized waves of the S-polarized component are combined, with a second die image, corresponding to the first die image, of a second die on which same pattern as that of the first die is formed, where the optical images of the 2n polarized waves of the P-polarized component and the optical images of the 2n polarized waves of the S-polarized component are combined.

3. The apparatus according to claim 1, wherein the angle of the passage region of the diaphragm is defined by a central line of the passage region which passes through the central axis.

4. The apparatus according to claim 3, wherein,

in a case where the angle of the passage region of the diaphragm is same as the first direction, the rotating half-wave plate converts the P-polarized component to the polarized wave in the first direction, and the S-polarized component to the polarized wave in the second direction, and

in a case where the angle of the passage region of the diaphragm is same as the second direction, the rotating half-wave plate converts the P-polarized component to the polarized wave in the second direction, and the S-polarized component to the polarized wave in the first direction.

5. A pattern inspection apparatus comprising:

a stage configured to be movable and to mount thereon a mask substrate for exposure on which a pattern is formed;

an objective lens configured to receive a transmitted light having passed through the mask substrate;

a diaphragm configured to be rotatable, to restrict a passage region of a light having passed through the objective lens to two regions opposite to each other with respect to a central axis in 4n equal regions divided rotationally symmetrically in a plane orthogonal to a traveling direction of the light having passed through the objective lens, and to change an angle of the passage region so that each the two regions of the 4n equal regions become passage regions in order;

a rotating half-wave plate configured to convert a P-polarized component having passed through the diaphragm and being in same direction as the angle of the passage region and an S-polarized component having passed through the diaphragm and being in a direction orthogonal to the angle of the passage region into a polarized wave in a first direction and a polarized wave in a second direction, where the first and second directions have been set previously and are orthogonal to each other;

a Rochon prism configured to separate a trajectory of the polarized wave in the first direction from a trajectory of the polarized wave in the second direction;

an image forming lens configured to focus and form an image of the polarized wave in the first direction having passed through the Rochon prism, at an image formation position, and an image of the polarized wave in the second direction having passed through the Rochon prism, at an other image formation position;

a mirror configured to reflect the polarized wave in the second direction, at the other image formation position of the polarized wave in the second direction which is different from the image formation position of the polarized wave in the first direction;

a first image sensor configured to capture an optical image of a polarized wave of the P-polarized component and an optical image of a polarized wave of the S-polarized component, as an optical image of the polarized wave in the first direction, while replacing the optical image of the polarized wave of the P-polarized component and the optical image of the polarized wave of the S-polarized component with each other depending on the angle of the passage region of the diaphragm;

a second image sensor configured to capture an optical image of a polarized wave of the S-polarized component and an optical image of a polarized wave of the P-polarized component, as an optical image of the polarized wave in the second direction, while replacing the optical image of the polarized wave of the S-polarized component and the optical image of the polarized wave of the P-polarized component with each other depending on the angle of the passage region of the diaphragm;

a beam splitter configured to branch an illumination light to go to the objective lens, and make a reflected light from the mask substrate pass through the beam splitter itself via the objective lens;

a first transfer mechanism configured to move the diaphragm, the rotating half-wave plate, and the Rochon prism between an inside and an outside of an optical path; and

a second transfer mechanism configured to move the beam splitter between the inside and the outside of the optical path,

wherein,

the diaphragm, the rotating half-wave plate, and the Rochon prism are arranged instead of the beam splitter, in the optical path in a case where a polarized image is acquired, and the beam splitter is arranged instead of the diaphragm, the rotating half-wave plate, and the Rochon prism, in the optical path in a case where a pattern inspection is performed,

the image forming lens, in the case where the pattern inspection is performed, focuses and forms an image of one of the transmitted light and the reflected light, at the image formation position of the polarized wave in the first direction, and focuses and forms an image of an other one of the transmitted light and the reflected light, at the other image formation position of the polarized wave in the second direction,

the mirror, in the case where the pattern inspection is performed, reflects the other one of the transmitted light and the reflected light, at the other image formation position of the polarized wave in the second direction,

the first image sensor, in the case where the pattern inspection is performed, captures the image of the one of the transmitted light and the reflected light, and

the second image sensor, in the case where the pattern inspection is performed, captures the image of the other one of the transmitted light and the reflected light.

6. The apparatus according to claim 5, further comprising:

a combining processing circuitry configured to combine optical images of 2n polarized waves of the P-polarized component and optical images of 2n polarized waves of the S-polarized component which have been image-captured for the each of the angle of the passage region; and

a comparison processing circuitry configured to compare a first die image of a first die, where the optical images of the 2n polarized waves of the P-polarized component and the optical images of the 2n polarized waves of the S-polarized component are combined, with a second die image, corresponding to the first die image, of a second die on which same pattern as that of the first die is formed, where the optical images of the 2n polarized waves of the P-polarized component and the optical images of the 2n polarized waves of the S-polarized component are combined.

7. The apparatus according to claim 5, wherein the angle of the passage region of the diaphragm is defined by a central line of the passage region which passes through the central axis.

8. The apparatus according to claim 7, wherein,

in a case where the angle of the passage region of the diaphragm is same as the first direction, the rotating half-wave plate converts the P-polarized component to the polarized wave in the first direction, and the S-polarized component to the polarized wave in the second direction, and

in a case where the angle of the passage region of the diaphragm is same as the second direction, the rotating half-wave plate converts the P-polarized component to the polarized wave in the second direction, and the S-polarized component to the polarized wave in the first direction.

9. A polarized image acquisition method comprising:

focusing an illumination light to form an image on a mask substrate for exposure on which a pattern is formed;

receiving a transmitted light having passed through the mask substrate by focusing the illumination light, into an objective lens;

restricting a passage region of the transmitted light having passed through the objective lens, using a diaphragm being rotatable and including two open regions opposite to each other with respect to a central axis in 4n equal regions divided rotationally symmetrically in a plane orthogonal to a traveling direction of the transmitted light having passed through the objective lens, to the two open regions, and changing an angle of the passage region so that each the two open regions of the 4n equal regions become passage regions in order;

converting, by using a rotating half-wave plate, for each of the angle of the passage region, a P-polarized component which has passed through the diaphragm and is in same direction as the angle of the passage region and an S-polarized component which has passed through the diaphragm and is in a direction orthogonal to the angle of the passage region into a polarized wave in a first direction and a polarized wave in a second direction, where the first and second directions have been set previously and are orthogonal to each other;

separating a trajectory of the polarized wave in the first direction from a trajectory of the polarized wave in the second direction by using a Rochon prism;

focusing, by using an image forming lens, to form an image of the polarized wave in the first direction having passed through the Rochon prism, at an image formation position, and an image of the polarized wave in the second direction having passed through the Rochon prism, at an other image formation position;

reflecting, by using a mirror, the polarized wave in the second direction, at the other image formation position of the polarized wave in the second direction which is different from the image formation position of the polarized wave in the first direction;

capturing, by using a first image sensor, an optical image of a polarized wave of the P-polarized component and an optical image of a polarized wave of the S-polarized component, as an optical image of the polarized wave in the first direction, while replacing the optical image of the polarized wave of the P-polarized component and the optical image of the polarized wave of the S-polarized component with each other depending on the angle of the passage region of the diaphragm; and

capturing, by using a second image sensor, an optical image of a polarized wave of the S-polarized component and an optical image of a polarized wave of the P-polarized component, as an optical image of the polarized wave in the second direction, while replacing the optical image of the polarized wave of the S-polarized component and the optical image of the polarized wave of the P-polarized component with each other depending on the angle of the passage region of the diaphragm.

10. A pattern inspection method comprising:

focusing a first illumination light to form an image on a mask substrate for exposure on which a pattern is formed;

receiving a first transmitted light having passed through the mask substrate by focusing the first illumination light, into an objective lens;

restricting a passage region of the first transmitted light having passed through the objective lens, by using a diaphragm being rotatable and including two open regions opposite to each other with respect to a central axis in 4n equal regions divided rotationally symmetrically in a plane orthogonal to a traveling direction of the first transmitted light having passed through the objective lens, to the two open regions, and changing an angle of the passage region so that each the two open regions of the 4n equal regions become passage regions in order;

converting, by using a rotating half-wave plate, for each of the angle of the passage region, a P-polarized component, which has passed through the diaphragm and is in same direction as the angle of the passage region, into a polarized wave in a first direction, and an S-polarized component, which has passed through the diaphragm and is in a direction orthogonal to the angle of the passage region, into a polarized wave in a second direction, where the first and second directions have been set previously and are orthogonal to each other;

separating, by using a Rochon prism, a trajectory of the polarized wave in the first direction from a trajectory of the polarized wave in the second direction;

focusing, by using an image forming lens, to form an image of the polarized wave in the first direction having passed through the Rochon prism, at an image formation position, and an image of the polarized wave in the second direction having passed through the Rochon prism, at an other image formation position;

reflecting, by using a mirror, the polarized wave in the second direction, at the other image formation position of the polarized wave in the second direction which is different from the image formation position of the polarized wave in the first direction;

capturing, by using a first image sensor, an optical image of a polarized wave of the P-polarized component and an optical image of a polarized wave of the S-polarized component, as an optical image of the polarized wave in the first direction, while replacing the optical image of the polarized wave of the P-polarized component and the optical image of the polarized wave of the S-polarized component with each other depending on the angle of the passage region of the diaphragm;

capturing, by using a second image sensor, an optical image of a polarized wave of the S-polarized component and an optical image of a polarized wave of the P-polarized component, as an optical image of the polarized wave in the second direction, while replacing the optical image of the polarized wave of the S-polarized component and the optical image of the polarized wave of the P-polarized component with each other depending on the angle of the passage region of the diaphragm;

moving the diaphragm, the rotating half-wave plate, and the Rochon prism from an inside to an outside of an optical path;

moving a beam splitter from the outside to the inside of the optical path;

illuminating the mask substrate with a second illumination light by using a transmission inspection illumination optical system;

illuminating the mask substrate with a third illumination light by using a reflection inspection illumination optical system;

receiving a second transmitted light having passed through the mask substrate by the second illumination light, and a reflected light having been reflected from the mask substrate by the third illumination light, into the image forming lens through the objective lens and the beam splitter;

focusing and imaging, by using the image forming lens, one of the second transmitted light and the reflected light, at the image formation position of the polarized wave in the first direction, and an other one of the second transmitted light and the reflected light, at the other image formation position of the polarized wave in the second direction;

reflecting, by using the mirror, the other one of the second transmitted light and the reflected light, at the other image formation position of the polarized wave in the second direction;

capturing, by using the first image sensor, an image of the one of the second transmitted light and the reflected light; and

capturing, by using the second image sensor, an image of the other one of the second transmitted light and the reflected light.