Foreign particle detecting method and apparatus

• US 4,669,875 A
• Filed: 11/03/1983
• Issued: 06/02/1987
• Est. Priority Date: 11/04/1982
• Status: Expired

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Uto, Sachio, Koizumi, Mitsuyoshi, Shiba, Masataka
• Primary Examiner(s): Kittle, John E.
• Assistant Examiner(s): Dees, Jose G.
• Application Number:
  US06/548,516
• Time in Patent Office: 1,307 Days
• Field of Search: 356/237, 356/339, 356/343, 356/338, 250/572, 250/578
• US Class Current: 356/237.3
• CPC Class Codes: G01N 2015/0238 Single particle scatter
• CPC Class Codes: G01N 2021/4792 Polarisation of scatter light
• CPC Class Codes: G01N 21/94 Investigating contamination, e.g. dust G01N21/85 takes precedence
• CPC Class Codes: G01N 2201/1053 System of scan mirrors for composite motion of beam

Abstract

The foreign particle detecting method and apparatus are disclosed wherein a polarized laser beam emitted by a laser beam irradiating system from a direction inclined with respect to the direction perpendicular to the surface of a substrate is used by a scanning means to linearly scan the substrate surface from a direction approximately 90° with respect to the laser light irradiating direction; and the laser light reflected from a foreign particle on the substrate surface is detected by a polarized light analyzer and a photoelectric conversion device from a direction set approximately equal to said scanning direction and inclined with respect to the direction perpendicular to the substrate surface.

Claims

1. A foreign particle detecting method comprising the steps of:

irradiating two halves of a substrate having a frame with a pellicle mounted thereon with a respective laser beam emitted by a laser beam irradiating means in a direction inclined with respect to the substrate surface and polarized thereafter so as to scan respective halves of the substrate surface in a predetermined direction while linearly moving said substrate in a direction crossing at substantially right angles to the light scanning direction;

positioning, at least prior to the step of irradiating, a respective polarized-light analyzer in said scanning direction inclined with respect to said substrate surface for analyzing the scattered light from a foreign particle on respective halves of the substrate; and

detecting said scattered light by a photo-electric conversion means;

whereby the entirety of the substrate is enabled to be inspected for detection of foreign particles irrespective of the frame and pellicle mounted on the substrate.

2. A foreign particle detecting method comprising the steps of:

irradiating two halves of a substrate, through a preventive means mounted on the substrate by a frame for preventing adherence of foreign particles to the substrate, with a respective laser beam emitted by a laser beam irradiating means in a direction inclined with respect to the substrate surface so as to scan respective halves the substrate surface which is covered with said preventive means in a predetermined direction while linearly moving said substrate in a direction substantially 90°

with respect to the laser beam crossing at substantially right angles to the light scanning direction;

positioning, at least prior to the step of irradiating, a respective polarized-light analyzer in said scanning direction inclined with respect to said substrate surface for analyzing the scattered light from a foreign particle on respective halves of the substrate; and

detecting said scattered light by a photoelectric conversion means;

wherein the entirety of the substrate is enabled to be inspected for detection of foreign particles irrespective of the frame and preventive means mounted on the substrate.

3. A foreign particle detecting apparatus comprising:

irradiating means for irradiating a respective polarized laser beam spot linearly scanning on respective halves of two halves of a substrate in a direction inclined with respect to the direction perpendicular to the surface of the substrate placed on a horizontal plane and having a frame with a pellicle mounted thereon, said irradiating means including a laser beam oscillator and a polarizer;

scattered light detecting means for detecting scattered light from a foreign particle in the laser beam spot on respective halves of the surface of the substrate, said scattered light detecting means being positioned along an extended direction of said scanning line and being inclined with respect to the direction perpendicular to the surface of the substrate, said scattered light detecting means including a polarized light analyzer, condenser lens, and photoelectric converter, whereby the entirety of the substrate is enabled to be inspected for detection of foreign particles irrespective of the frame and pellicle mounted on the substrate.

4. A foreign particle detecting apparatus according to claim 3, comprising a light blocking means disposed between said condenser lens and photoelectric converter of said scattered light detecting means.

5. A foreign particle detecting apparatus according to claim 3 wherein the inclination angle of at least one of said optical axis of the irradiating means and scattered light detecting means is 22.5°

±

15°

.

6. A foreign particle detecting apparatus according to claim 3 wherein said optical axes of the irradiating means and the scattered light detecting means intersect each other at angle of 90°

±

10°

on said surface of the substrate.

7. A foreign particle detecting apparatus comprising:

frame position detecting means for detecting a position of a frame of a pellicle mounted on a substrate; and

detection means for detecting a foreign particle existing in the inspection area enclosed with said frame according to the frame mounting position detected by said frame position detecting means.

8. A foreign particle detecting apparatus comprising:

laser beam irradiating means for irradiating two halves of a substrate having a frame with a pellicle mounted thereon with a respective polarized laser beam spot, each of said laser beam spots being scanned over one half of the substrate in a direction inclined with respect to a direction perpendicular to the surface of the substrate; and

a pair of light detecting means positioned in the direction along which said scanning line is extended for detecting scattered light from a foreign particle on respective halves of the substrate, for analyzing the scattered light by a polarized light analyzer, for condensing the scattered light by a condenser lens, and for detecting the image formation obtained from said condenser lens by a photoelectric converting means, wherein blocking means for blocking the light scattered from other than the surface of said substrate is disposed between said condenser lens and said photoelectric converting means;

whereby the entirety of the substrate is enabled to be inspected for detection of foreign particles irrespective of the frame and pellicle mounted on the substrate.

9. A foreign particle detecting apparatus according to claim 8 wherein said blocking means of said scattered light detecting means is disposed along a direction inclined with respect to the optical axis of said condenser lens.

10. A foreign particle detecting apparatus according to claim 9 wherein the magnification of said condenser lens of said scattered light detecting means is equal to or less than one.

11. A foreign particle detecting apparatus according to claim 9 wherein said blocking means is formed by a slit.

12. A foreign particle detecting apparatus according to claim 11 wherein the width of said slit of said blocking means changes in the longitudinal direction.

13. A foreign particle detecting apparatus according to claim 8 wherein at least a pair of said irradiating means are disposed opposing to each other with respect to said substrate, at least a pair of said light detecting means is disposed opposing to each other with respect to said substrate.

14. A foreign particle detecting apparatus comprising:

projecting means including;

a laser source;

a rotating mirror for performing scanning by use of a laser beam projected from said laser source in a predetermined direction;

a changeover mirror for changing over the direction of the laser beam by reflecting said laser beam outputted from said rotating mirror;

a pair of projecting optical systems, each of said projecting optical systems being arranged for projecting said laser beam changed over by said changeover mirror as a laser spot from a direction inclined with respect to a substrate having a frame with a pellicle mounted thereon so that said laser beam projected by one of said projecting optical systems is projected in a direction opposite to the direction of projecting of said laser beam by the other of said projecting systems for scanning different halve of said substrate; and

at least a pair of detecting means disposed opposing to each other with respect to said substrate, which detects from an inclined direction with respect to said substrate, scattered light from a foreign particle existing in the laser spot on the different halves of said substrate projected by said projecting optical systems through a polarized-light analyzer and a condenser lens and for providing output electric signals by photoelectric converting means disposed along each axis of said pair of detecting means;

whereby the entirety of the substrate is enabled to be inspected for detection of foreign particles irrespective of the frame and pellicle mounted on the substrate.

15. A foreign particle detecting apparatus comprising:

projecting means including;

a laser source;

a rotating mirror for performing scanning by use of a laser beam projected from said laser source in a predetermined direction;

a changeover mirror for changing over the direction of the laser beam by reflecting said laser beam outputted from said rotating mirror;

a pair of projecting optical systems, each of said projecting optical systems being arranged for projecting said laser beam changed over by said changeover mirror as a laser spot from a direction inclined with respect to a substrate so that said laser beam projected by one of said projecting optical systems is projected in a direction opposite to the direction of projection of said laser beam by the other of said projecting optical systems;

at least a pair of detecting means disposed opposing to each other with respect to said substrate, which detects from an inclined direction with respect to said substrate, scattered light from a foreign particle, existing in the laser spot on said substrate projected by said projecting optical systems through a polarized-light analyzer and a condenser lens and for providing output electric signals by photoelectric converting means disposed along each axis of said pair of detecting means; and

frame detecting means for detecting a position of a frame for supporting means for preventing adherence of foreign particles on said substrate.

16. A foreign particle detecting method comprising the steps of:

actuating one of a set of scanners to scan one half of a substrate to be inspected, the substrate having a frame with a pellicle mounted thereon, each scanner being positioned in a direction capable of scanning an opposite one half of the substrate to be inspected;

actuating the other of the set of scanners to scan the opposite one half of the substrate to be detected; and

inspecting, during the actuation of each of the scanners, a respective one half of the substrate to be inspected using a respective one of a set of detectors positioned substantially at a right angle to the scanning direction, when viewed from above the substrate;

whereby the entirety of the substrate is enabled to be inspected for detection of foreign particles irrespective of the frame and pellicle mounted on the substrate.

17. A foreign particle detecting method according to claim 16, wherein each of the scanners has an optical axis arranged at an inclination angle of 22.5°

±

15°

with respect to the substrate.

18. A foreign particle detecting method according to claim 16, wherein each of the detectors has an optical axis arranged at an inclination angle of 22.5°

±

5°

with respect to the substrate.

19. A foreign particle detecting apparatus comprising:

a pair of light directing means disposed opposing to each other with respect to a substrate for directing a pair of light beams to the substrate in a direction inclined with respect to the substrate so as to enable light to be scattered from a particle on the substrate, the light directing means including;

a laser beam source,

a rotating mirror for performing scanning of a laser beam produced from said laser beam source in a predetermined direction,

a changeover mirror for changing over the direction of the laser beam reflected from the rotating mirror,

table driving means for driving a table carrying the substrate so as to enable two-dimensional scanning of a part of the substrate with the scanning by the rotating mirror, and

lens and mirrors set in a path of said laser beam from said laser beam source for polarizing and focusing the laser beam onto the substrate in the direction inclined with respect to the substrate,

a pair of scattered light detecting means for detecting scattered light from the substrate and disposed opposing to each other and substantially at right angles with respect to said pair of light beams, each of said pair of light detecting means including;

a polarized light analyzer,

a condenser lens,

slit means for blocking light scattered from other than the surface of the substrate, and

photoelectric converting means arranged along said scanning direction and inclined with respect to the substrate,

set-up means for setting up at least four different foreign particle inspecting areas on the substrate including;

sensor means for detecting a metallic attachment for the substrate and for producing signals indicative of the detection result, and

specifying means for specifying the presence or absence and the position of a foreign particle in the inspection area including determining means for determining position signals representing the position of the foreign particle when output signals of said sensor means are greater than a predetermined varying standard.

20. A foreign particle detecting apparatus according to claim 19, wherein the metallic attachment is a frame of a pellicle mounted on the substrate and which encloses the different inspection areas.