JP2001272355A - Foreign matter inspecting apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a foreign matter inspecting apparatus for quickly and accurately detecting foreign matters in a large plate-shaped sample, without using any sophisticated expensive optical system. SOLUTION: When the surface 1a of a sample 1 held on an inspection stage 2 is irradiated with a light beam from a light source, a scattered light beams from the sample surface is incident on an optical detector, and on the basis of scattered light intensity from the optical detector, the foreign matter inspecting device detects the existence/absence of a foreign matter on the sample surface. In this foreign matter inspecting device, a laser pattern projector 4 is used as the light source, while a linear array sensor 9 is used as the optical detector.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a glass substrate incorporated in a liquid crystal display device, a reticle or mask used for printing a circuit pattern on a semiconductor wafer in an LSI manufacturing process, or a product on which a circuit pattern is formed. On the surface of a plate-like sample such as a wafer,
The present invention relates to a foreign matter inspection apparatus capable of specifying whether or not foreign matter is attached, its size, and the place of attachment.

[0002]

2. Description of the Related Art In the above-described foreign particle inspection apparatus, it is necessary to measure the entire surface of a sample to be inspected. As a conventional foreign particle inspection apparatus of this type, for example, there is one shown in FIG. That is, 71 is a plate-shaped sample 7 such as glass.
The inspection stage 2 is mounted horizontally, is held by a stage driving mechanism 73, and is configured to be able to move linearly in an arrow X direction and an arrow Y direction orthogonal thereto.

An irradiation optical system 74 irradiates a laser beam 75 as a probe beam to the surface 72a of the sample 72 while scanning the laser beam 75 linearly in the direction of the arrow X. The irradiation optical system 74 emits a laser beam 75 having a fixed deflection angle. Scanning mirror 7 driven and controlled by a laser light source 76 composed of a He-Ne laser oscillator, a beam expander 77, and a galvanometer 78
9 and a condensing lens 80 such as an fθ lens, and irradiates a laser beam 75 from a laser light source 76 from a diagonally upper direction of the sample 72 at a predetermined angle in the X direction while performing reciprocal linear scanning. It is configured.

Reference numeral 81 denotes a laser beam 75 irradiated on a sample 72.
A detection optical system for detecting the scattered light 82 from the sample surface 72a is disposed obliquely above one end of the sample 72 in the X direction. The detection optical system 81 includes a condenser lens 83 and a scattered light. It comprises a slit member 84 having an elongated slit 84a for restricting incident light with respect to 82, and a photodetector 85 such as a photomultiplier tube.

The foreign matter inspection device is controlled by a computer or other suitable arithmetic and control unit (not shown) such as a computer, and moves the inspection stage 71 linearly in the direction of the arrow Y while moving the laser beam from the laser light source 76. Light 75,
Irradiation is performed while reciprocating linearly scanning within a predetermined range in the X direction from an obliquely upward direction of the sample 72 at a predetermined angle, and the scattered light 82 from the sample surface 72 a at that time is incident on the photodetector 85. .

When no foreign matter is present on the sample surface 72a, high intensity scattered light 82 is not generated. However, when foreign matter is present, high intensity scattered light is emitted from the foreign matter. This is incident on the photodetector 85. Therefore, a detection output representing the scattered light intensity from the light detector 85 is input to the arithmetic and control unit. In this arithmetic and control unit, a threshold value is set in advance. When the output is larger than the threshold value, it is determined that a foreign substance is present on the sample surface 72a. It is determined that no foreign matter exists on the surface 72a. Then, in the arithmetic and control unit, the laser beam irradiation position and the detection result are associated with each other, and it is possible to know at what position on the sample surface 72a what kind of foreign matter is present.

Further, as shown in FIG.
Is a mask or reticle, the microscope 8
6, the sample 72 is moved linearly sequentially in the X direction and the Y direction, so that the entire surface of the sample surface 72a can be observed through the microscope 86. Further, as shown in FIG. In the case of a circular shape, while the probe light 87 is fixedly irradiated on the sample surface 72a,
There is a method of measuring the entire surface of the sample surface 72a by moving the sample 72 linearly in the X direction and rotating it in the R direction.

[0008]

However, in the foreign matter inspection apparatus shown in FIG. 7, since the lens system is used in the irradiation optical system 74 and the detection optical system 81, the configuration is extremely complicated. In particular, since expensive components such as the galvanometer 78 are used for the irradiation optical system 74, there is a disadvantage that the cost of the entire apparatus increases.
Further, it is necessary to scan with the laser light 75 as the probe light, which has the drawback that the control is troublesome and the inspection takes time.

In the method shown in FIGS. 7 and 8, the area that can be measured at a time is the probe light 7
5, 87 and the size of the field of view of the microscope 86. The magnitude is determined by a method of discriminating a pattern signal and a foreign substance signal on the sample 72, respectively.
If this is inadvertently increased, the measurement accuracy is usually significantly reduced. In order to simply increase the measurement speed, it is necessary to move the sample such as the sample 72 at a high speed and perform measurement with the same accuracy. However, there is a disadvantage that the detection sensitivity cannot be secured.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above-mentioned problems, and has as its object to perform a foreign substance inspection on a large plate-like sample at high speed and with high accuracy without using a complicated and expensive optical system. An object of the present invention is to provide a foreign matter inspection device.

[0011]

In order to achieve the above object, according to a first aspect of the present invention, a surface of a sample held on an inspection stage is irradiated with light from a light source to scatter light from the sample surface at that time. In a foreign matter inspection apparatus that makes light incident on a light detector and inspects the presence or absence of foreign matter on a sample surface based on the intensity of scattered light from the light detector, a laser pattern projector is used as the light source, and a linear array is used as the light detector. A sensor is used (claim 1).

Since the laser pattern projector itself irradiates a laser beam as shown in FIG. 1, it requires an optical scanning mechanism such as a galvanometer or a scanning mirror as in a conventional foreign matter inspection apparatus. do not do. Therefore, even without the use of complicated and expensive optical systems, high-speed and high-precision detection of foreign matter in large plate-shaped samples, such as glass-shaped samples such as glass and non-patterned samples and wafers with patterned patterns, such as wafers. can do.

In the second invention, the surface of the sample held on the inspection stage is irradiated with light from a light source, and the scattered light from the surface of the sample at that time is made incident on a photodetector. In a foreign matter inspection device for inspecting the presence or absence of foreign matter on a sample surface based on the intensity of scattered light by a sampler, light that is parallel in the traveling direction with respect to the sample surface is spread over the entire measurement width of the sample surface. An irradiation optical system for irradiating the sample so as to form a certain angle, and a detection optical system for mainly detecting scattered light in a direction perpendicular to the sample surface and including a line of intersection of the sample surface and the incident light. (Claim 2).

In the second aspect of the present invention, the detection optical system may include a cylindrical lens and a line sensor provided on the Fourier transform plane on the center side or the rear side of the cylindrical lens. A detection optical system, a gradient index lens array, a mask slit provided on the Fourier transform surface on the center side or the rear side of the gradient index lens array, and a line sensor provided at a focal position of the gradient index lens array. (Claim 4).

In the second aspect of the present invention, since the scattered light from one foreign substance on the sample surface is detected by a plurality of adjacent sensor elements, the signals from the foreign substance are grouped based on the intensity distribution and displayed. Can be.

In the second invention, as in the first invention, an optical scanning mechanism such as a galvanometer or a scanning mirror is not required, so that a foreign substance inspection on a large sample can be performed at high speed without using a complicated and expensive optical system. It can be carried out. And
It is possible to detect foreign substances not only in a plate-shaped sample having no pattern formed thereon, such as glass, but also in a plate-shaped sample having a pattern formed, such as a wafer, at high speed and with high accuracy.

[0017]

Embodiments of the present invention will be described with reference to the drawings. First, FIG. 1 schematically shows an example of the configuration of an optical system in a foreign matter inspection apparatus according to the first invention. In FIG. 1, reference numeral 1 denotes a plate-like sample such as glass, which is horizontally placed on an inspection stage 2. It is placed on. The inspection stage 2 has a stage driving mechanism (not shown).
, And can linearly reciprocate in the direction of the arrow X in the figure.

Reference numeral 3 denotes an irradiation optical system for irradiating the surface (upper surface) 1a of the sample 1 on the inspection stage 2 with laser light, and comprises a laser light source 4 and a condenser lens 5. The laser light source 4 is formed of a laser pattern projector, and is provided obliquely above one end of the inspection stage 2 in the X direction. The laser pattern projector 4 emits a laser beam 6 that spreads linearly in the Y direction (the width direction of the inspection stage 2) orthogonal to the X direction about the light emitting point 4a.
There is a collimating line projector manufactured by ASIRIS. The condensing lens 5 is made of, for example, a cylindrical lens or a telecentric fθ lens, has a length enough to irradiate the entire width (length in the Y direction) of the sample 1, and performs inspection with the laser pattern projector 4. It is interposed in the optical path between the stage 2.

Reference numeral 7 denotes a detection optical system for detecting scattered light 8 generated on the sample surface 1a when the sample surface 1a is irradiated with the laser light 6 from the irradiation optical system 3, and includes a photodetector 9 and a condenser lens array 10 Consists of And the photodetector 9
Is composed of a CCD array sensor and is provided horizontally in the Y direction. Here, the reason why the CCD array sensor is used as the photodetector 9 is that the laser beam 6 from the laser pattern projector 4 is not beam-scanned unlike the conventional one, and to compensate for this, the position information is obtained as a photodetector. CCD
They use an array sensor. The condensing lens array 10 is provided below the photodetector 9 so as to correspond to the photodetector 9, and three or four rows of GRIN-based cylindrical lenses having a refractive index distribution in the radial direction of the cylinder are arranged. In the cylindrical lens array, as such a condensing lens array 10, there is an array of refractive index distribution lenses such as a SELFOC lens (trade name). The detection optical system 7 has such a length that the whole of the sample 1 in the width direction can be detected.

Each component of the foreign matter inspection device is controlled by an appropriate arithmetic and control unit (not shown) such as a computer. Light 6 is applied to sample 1
Irradiation is performed in a state where the light is spread from the obliquely upward direction at a predetermined angle to the entire Y direction, and the scattered light 8 from the sample surface 1a at that time is incident on the photodetector 9. In the foreign substance inspection apparatus according to this embodiment, the presence / absence and size of the foreign substance are detected in the same manner as in the conventional foreign substance inspection apparatus shown in FIG.

As described above, in the foreign matter inspection apparatus of the first invention, the entire surface of the sample 1 can be irradiated with the laser beam 6 without providing an optical scanning mechanism such as a galvanometer or a scanning mirror. Even if the width (length in the Y direction) of the laser beam becomes large, it is not necessary to scan with the laser beam 6 as in the related art, and the inspection can be performed at high speed. Therefore, the configuration of the optical system, particularly the irradiation optical system 3, is simplified, the control thereof is facilitated, the entire apparatus can be configured at low cost, and the time required for inspection can be reduced.

In the above foreign matter inspection apparatus, a condenser lens 5 is provided in the irradiation optical system 3, and the laser beam 6 is focused on the sample surface 1a in a direction perpendicular to the line (a direction orthogonal to the X and Y directions). Irradiation improves sensitivity.

Next, FIG. 2 schematically shows an example of the configuration of an optical system in the foreign matter inspection apparatus of the second invention. In FIG. 2, the reference numerals in FIG. 1 are the same. In FIG. 2, reference numeral 11 denotes a plate-like sample such as a wafer, which is placed horizontally on an inspection stage (not shown) and is configured to be able to move at a constant speed in the direction of arrow X.

Reference numeral 12 denotes an irradiation optical system for irradiating the surface 11a of the sample 11 with monochromatic laser light 13 as probe light, and comprises a laser light source 14 and a telecentric fθ lens 15. The laser light 13 used here is a parallel light beam in the direction of its travel in the double arrow Y direction (perpendicular to the X direction), and is parallel in the direction perpendicular to the Y direction. Or sample 11
To slightly converge. That is, the irradiation optical system 12 is configured to irradiate the laser beam 13 which is a parallel light beam in the traveling direction over the entire measurement width of the sample surface 11a so as to form a fixed angle with the sample surface.

The irradiation optical system 12 may be formed by a combination of a line pattern generator 15 composed of a prism and a parabolic mirror 16, as shown in FIG. In FIG. 3, the paraboloid of the parabolic mirror 16 is only in the longitudinal direction (direction indicated by 17 in the figure), and is flat in the short direction.

The sample surface 11 of the laser beam 13
The degree of convergence at a may be appropriately determined based on the required detection sensitivity and the like. When the laser beam 13 is converged, it is preferable to focus on the sample surface 11a.

Referring again to FIG. 2, reference numeral 18 denotes the sample surface 11a.
Is a detection optical system that mainly detects scattered light on a surface including an intersection 19 where the sample surface 11a intersects with the laser beam 13 incident thereon, in a direction perpendicular to the sample surface 11a, and is provided in a normal direction of the sample surface 11a. It comprises a lens 20 and a line sensor 21 composed of a plurality of sensor elements provided on the Fourier transform surface on the center side or the rear side of the cylindrical lens 20.

The cylindrical lens 20 is placed above the sample 11 in a state parallel to the sample surface 11a and perpendicular to the X direction so that the line of intersection between the laser beam 13 and the sample surface 11a can be seen over the entire area. Is provided. The line sensor 21 is provided in parallel with the intersection line 19 and on the axis of the cylindrical lens 20.

In the detection optical system 18, when a pattern is formed on the sample surface 11a, the scattered / diffracted light generated by the incidence of the laser beam 13 on this pattern is transmitted through the cylindrical lens 20 to the line. The light enters the sensor 21. However, by setting the incident angle of the laser light 13 to the sample surface 11a as described later, light other than the scattered / diffracted light from the pattern parallel to the intersection line 19 hardly enters the cylindrical lens 20.

That is, when the detection optical system 18 is provided above the sample 11 and perpendicular to the sample surface 11a, at least the conditions for not detecting the regular reflection light of the laser beam 13 are as follows. Now, the sample surface 1 of the laser beam 13
The incident angle to the 1a theta, the angle of convergence of the tilt direction of the laser beam 13 [psi, when the numerical aperture of the cylindrical lens 20 and α, (θ-ψ / 2 )> sin - satisfy at least the alpha ...... (1) To do so.

Then, of the patterns having various angle components, which angle component (the diffracted light signal becomes stronger as approaching the intersection line 19) is weakened, and the size of the foreign matter is determined by the size of the foreign matter. It is necessary to adjust the incident angle θ and the numerical aperture α depending on whether the detection is performed without detection. Considering the easiness in configuring the apparatus and the transmittance of the pellicle film which is a dust evasion for the sample 11, the incident angle θ
Is preferably 60 ° or less. Also, if the numerical aperture α is larger than 0.5, it will take in even low-order diffracted light,
It becomes difficult to discriminate the pattern from the foreign matter.

Further, in the detection optical system 18,
Since the line sensor 21 is provided on the Fourier transform surface of the cylindrical lens 20, the light incident on the line sensor 21 is a light ray in a plane connecting the intersection line 19 and the line sensor 21, or a light parallel to the light. There is only a light beam (actually, there is a spread by the thickness of the line sensor 21). That is, of the scattered light / diffracted light from the pattern on the sample surface 11a, those from components that are not parallel to the light beam are excluded by the arrangement of the incident light 13 and the cylindrical lens 20, and the light from the line segment parallel to the light beam is removed. Most are excluded to a space that does not intersect with the line sensor 21.

In the case of foreign matter, since the incident light 13 and the scattered light component directed to the plane formed by the line sensor 21 are almost always present, the scattered light can be reliably detected.

When the cylindrical lens 20 is used, the width perpendicular to the line of intersection of the line sensor 21 is large, so that more diffraction light is detected on the Fourier transform plane, and discrimination between patterns / foreign substances is not sufficient. , Line sensor 2
Instead of 1, a thinner slit may be provided, and the line sensor 21 may be arranged at a position conjugate with the intersection line 19 with respect to the cylindrical lens 20.

The second invention is not limited to the above embodiment, but can be implemented in various modifications.
For example, at the position of the line sensor 21 in FIG. 2 (that is, the Fourier transform surface of the cylindrical lens 20),
A slit may be provided, an image forming lens may be provided, and a line sensor 21 may be provided at a subsequent stage. A bundle of optical fibers may be provided on the Fourier transform surface, and light may be guided to the line sensor 21 via the optical fibers.

Further, the detection optical system 18 may be configured as shown in FIG. That is, in FIG. 4, reference numeral 22 denotes a gradient index lens array such as a SELFOC lens (trade name), and 23 denotes a gradient index lens array 22.
Is a mask slit provided on the center-side or rear-side Fourier transform surface. And the line sensor 21
It is provided at the focal position of the gradient index lens array 22 after the mask slit 23.

The reason for the above construction is as follows. That is, unlike the cylindrical lens 20, the refractive index distribution lens array 22 cannot have the function of a slit for limiting the diffracted light on the line of the line sensor 21. A mask slit 23 having a large number of strip-like slits 23a as shown in FIG. 5, for example, is provided on the Fourier transform surface of the distribution lens. The mask slit 23 is provided so that the strip-shaped slit 23 a is parallel to the intersection line 19. In this case, the line sensor 21 is disposed at an optically conjugate position through the intersection line 19 and the refractive index distribution lens 22.

In the case where the refractive index distribution lens array 22 is provided in the detection optical system 18, unlike the case where the cylindrical lens 20 is provided, light can be collected also in the direction of the intersection line 19, so that one sensor element , And the detection sensitivity of foreign matter scattered light is improved. When the gradient index lens array 22 is used, light cannot be transmitted unless it is within a certain numerical aperture in the direction of the intersection line 19 as well. Is difficult to enter, and the S / N is improved.

As the mask slit 23, a slit 24 having a plurality of slits 24a having a shape as shown in FIG. 6 may be used. That is, as shown in the enlarged view, the mask slit 24 has a shape in which a plurality of slits 24a formed in the mask slit 24 are formed by abutting triangles having an apex angle β of 10 ° to 40 °. 24
c is set so as to be parallel to the intersection line 19. The mask slit 24 having such a shape can increase the amount of light passing therethrough and can surely block a diffraction component that becomes stray light, as compared with the mask slit 23 shown in FIG. The angle β is preferably increased when sensitivity is required, and decreased when a discrimination function is required.

[0040]

As described above, unlike the conventional foreign matter inspection apparatus, the first and second inventions do not need to scan a beam such as a laser beam used for measurement. This eliminates the necessity, simplifies the configuration of the apparatus, reduces the cost of the apparatus, and allows the foreign substance inspection of the sample to be performed in a short time. Then, even if the size of a sample such as a glass substrate or a wafer to be inspected becomes large, it is possible to perform a foreign substance inspection in a short time and with high accuracy, and it is possible to suitably cope with an increase in the size of a liquid crystal display device or a wafer. .

In particular, according to the second aspect of the present invention, foreign matter in a plate-like sample on which a pattern is not formed, such as glass, as well as a foreign matter in a plate-like sample on which a pattern is formed, such as a wafer, can be discriminated from the pattern at a high speed. Detection can be performed with higher accuracy.

[Brief description of the drawings]

FIG. 1 is a perspective view schematically showing an example of a configuration of an optical system in a foreign matter inspection device according to a first invention.

FIG. 2 is a perspective view schematically showing an example of a configuration of an optical system in the foreign matter inspection device of the second invention.

FIG. 3 is a diagram showing another example of the configuration of the irradiation optical system in the foreign matter inspection device.

FIG. 4 is a perspective view schematically showing another example of the configuration of the optical system in the foreign matter inspection device of the second invention.

FIG. 5 is a perspective view schematically showing an example of a mask slit used in the foreign matter inspection device.

FIG. 6 is a perspective view schematically showing another example of the mask slit together with an enlarged view.

FIG. 7 is a perspective view schematically showing a configuration of an optical system of a conventional foreign matter inspection device.

FIG. 8 is a diagram schematically showing a conventional foreign matter inspection method.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... sample, 1a ... sample surface, 2 ... inspection stage, 4 ... laser light source (laser pattern projector), 6 ... laser light, 8 ... scattered light, 9 ... detector (linear array sensor),
11: sample, 11a: sample surface, 12: irradiation optical system, 1
3 incident light, 14 light source, 18 detection optical system, 19 intersection line, 20 cylindrical lens, 21 line sensor, 22 refractive index distribution lens array, 23, 24 mask slit.

Claims (4)

[Claims] 1. A light source irradiates a surface of a sample held on an inspection stage with light from a light source, and scattered light from the substrate surface at that time is made incident on a photodetector. 1. A foreign matter inspection apparatus for inspecting the presence or absence of foreign matter on a sample surface based on a laser pattern projector as the light source and a linear array sensor as the light detector. 2. A light source irradiates a surface of a sample held by an inspection stage with light from a light source, and scattered light from the sample surface at that time is incident on a photodetector, and the scattered light intensity by the photodetector is obtained. In a foreign matter inspection device for inspecting the presence or absence of foreign matter on a sample surface based on the light, which is a parallel light flux in the traveling direction with respect to the sample surface, the entire surface or a part of the measurement width of the sample surface, the sample surface An irradiation optical system for irradiating the sample so as to form a certain angle, and a detection optical system for mainly detecting scattered light in a direction perpendicular to the sample surface and including a line of intersection of the sample surface and the incident light. A foreign matter inspection device, characterized in that: 3. The foreign matter inspection apparatus according to claim 2, wherein the detection optical system includes a cylindrical lens and a line sensor provided on a Fourier transform surface on a center side or a rear side of the cylindrical lens. 4. A refractive index distribution lens array, a mask slit provided on a Fourier transform surface on a center side or a rear side of the refractive index distribution lens array, and a detection optical system provided at a focal position of the refractive index distribution lens array. 3. The foreign matter inspection device according to claim 2, further comprising a line sensor.