LIGHTING DEVICE AND INSPECTION APPARATUS HAVING THE SAME

• US 20200132977A1
• Filed: 08/21/2019
• Published: 04/30/2020
• Est. Priority Date: 10/29/2018
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: HIDAKA, YASUHIRO, KAJINAMI, MASATO, SASAOKA, TAKAYUKI
• Granted Patent: US 11,314,073 B2
• Time in Patent Office: Days
• CPC Class Codes: G01N 21/8806 Specially adapted optical and illumination features
• CPC Class Codes: G01N 21/9501 Semiconductor wafers manufacturing processes per se of semiconductor devices implementing a measuring step H01L22/10
• CPC Class Codes: G02B 21/0016 Technical microscopes, e.g. for inspection or measuring in industrial production processes
• CPC Class Codes: G02B 21/084 having annular illumination around the objective
• CPC Class Codes: G02B 21/14 affording illumination for phase-contrast observation
• CPC Class Codes: G02B 21/36 arranged for photographic purposes or projection purposes G02B21/18 takes precedenceor digital imaging or video purposes including associated control and data processing arrangements image data processing per se G06T
• CPC Class Codes: G02B 26/06 for controlling the phase of light G02B26/08 takes precedence , measuring optical phase difference G01J9/00
• CPC Class Codes: G03F 7/70616 Monitoring the printed patterns

Abstract

A lighting device includes a light source generating a beam of illumination light, a ring-shaped aperture shielding a central portion of the illumination light and transforming the beam of illumination light into ring-shaped illumination light, and an object lens focusing the ring-shaped illumination light such that a specimen can be illuminated with the ring-shaped illumination light. An inspection apparatus including the light device also has a beam splitter and an image sensor picking up light reflected and/or diffracted from the specimen through the beam splitter. Because a central portion of the illumination light is shielded, lens flare of light transmitted by the beam splitter and the object lens is prevented thereby preventing speckles in the image produced by the image sensor.

Claims

1. A lighting device comprising:

a light source that generates a beam of illumination light along an optical path of the lighting device;

a ring-shaped aperture disposed along the optical path such that a central portion of the illumination light is shielded and the illumination light transmitted through the aperture has a ring-shaped cross section in a plane perpendicular to the optical path; and

an object lens positioned downstream of the ring-shaped aperture along the optical path to focus the illumination light having the ring-shaped cross section on a focal plane onto a specimen disposed at the focal plane.

2. The lighting device of claim 1, further comprising an optical phase modulator disposed along the optical path and operative to change a phase of the illumination light temporally or spatially.

3. The lighting device of claim 2, wherein the optical phase modulator comprises an optical diffuser whose position relative to the optical path is variable over time.

4. The lighting device of claim 1, further comprising optics configured to transmit the illumination light as a parallel beam, a divergent beam and a convergent beam along respective portions of the optical path, and wherein the ring-shaped aperture is positioned in the portion of the optical path along which the parallel beam of the illumination light transmitted.

5. The lighting device of claim 1, wherein the ring-shaped aperture is positioned at a working distance of the object lens.

6. The lighting device of claim 1, further comprising optics configured to transmit the illumination light as a parallel beam, a divergent beam and a convergent beam along respective portions of the optical path, and wherein the ring-shaped aperture is positioned in the portion of the optical along which the divergent beam or the convergent beam is transmitted.

7. The lighting device of claim 1, wherein the ring-shaped aperture is defined between an inner light shield and an outer light shield delimiting an outer boundary or the aperture, the inner light shield being arranged centrally with respect to the outer boundary of the aperture delimited by the outer light shield.

8. The lighting device of claim 7, wherein transmittance of the inner light shield, with respect to the illumination light, decreases from a central portion to a peripheral portion thereof.

9. The lighting device of claim 7, further comprising a reflective member on the inner light shield.

10. The lighting device of claim 9, wherein the reflective member has a reflectance that decreases from a central portion to a peripheral portion of the inner light shield.

11. The lighting device claim 1, wherein the light source comprises a laser.

12. The lighting device claim 11, wherein the laser is a semiconductor laser that has a Fabry-Perot resonator

13. An inspection apparatus comprising:

a light source that generates a beam of illumination light along an optical path;

a ring-shaped aperture disposed along the optical path such that a central portion of the illumination light is shielded and the illumination light transmitted through the aperture has a ring-shaped cross section in a plane perpendicular to the optical path;

an object lens positioned downstream of the ring-shaped aperture along the optical path to focus the illumination light having the ring-shaped cross section on a focal plane to a specimen disposed at the focal plane such that a central portion of the illumination light generated by the light source is not to be reflected from the specimen; and

an image sensor positioned relative to the object lens to receive the peripheral portion of the illumination light reflected from the specimen and operative to generate an image of the specimen from the illumination light reflected from the specimen.

14. The inspection apparatus of claim 13, wherein the ring-shaped aperture is defined between an inner light shield unit and an outer light shield delimiting an outer boundary or the aperture, the inner light shield being arranged centrally with respect to the outer boundary of the aperture delimited by the outer light shield.

15. An inspection apparatus comprising:

a light source that generates a beam of illumination light along an optical path;

a diaphragm disposed along the optical path, the diaphragm including an outer light shield delimiting an outer boundary of an aperture and an inner light shield disposed centrally with respect to the outer boundary of the aperture such that the diaphragm transmits the illumination light through the aperture as a beam with an umbra at a central portion of the beam;

an object lens positioned downstream of the aperture along the optical path to focus the beam with an umbra at its central portion on a focal plane, whereby a peripheral portion of the beam of illumination light generated by the light source and focused by the object lens is to illuminate and reflect from a specimen disposed at the focal plane; and

an image sensor positioned relative to the object lens to receive the beam of illumination light reflected from the specimen and operative to generate an image of the specimen from the beam of the illumination light reflected from the specimen.

16. The inspection apparatus of claim 15, wherein the inner light shield is opaque with respect to the illumination light generated by the light source.

17. The inspection apparatus of claim 15, wherein the inner light shield is partially transparent with respect to the illumination light generated by the light source and has a transmittance that decreases from a central portion to a peripheral portion thereof.

18. The inspection apparatus of claim 15, wherein the light source comprises a laser that generates a laser beam as the illumination light.

19. The inspection apparatus of claim 18, wherein the inner light shield comprises a member or coating that is reflective.

20. The inspection apparatus of claim 18, further comprising an optical phase modulator disposed along the optical path between the laser of the light source and the aperture.