JPH1172443A - Automatic macroscopic inspection apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an automatic macroscopic inspection apparatus by which the macrocopic inspection of various objects to be inspected can be performed with good efficiency while an illumination device, an imaging device and the like are kept fixed. SOLUTION: An automatic macroscopic inspection apparatus is constituted of an illumination optical system 100 which is fixed, arranged and installed at a first prescribed angle with reference to a wafer 3 and by which illumination light comprising nearly parallel luminous fluxes is irradiated toward the whole face of the wafer 3, of an imaging element 6 which is fixed, arranged and installed at a second prescribed angle with reference to the wafer 3, which receives diffracted light or scattered light from the wafer 3 and which images the image of the wafer 3 and of an image processor 7 which fetches an image signal obtained by the imaging element 6 so as to perform an image processing operation and which performs a macroscopic inspection. It is provided with a plurality of interference filters by which the wavelength of the illumination light from the illumination optical system 100 is set so as to be variable.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for inspecting the surface of a glass substrate for manufacturing a liquid crystal or a wafer for manufacturing an IC, and more particularly to an apparatus for inspecting the entire surface of an object to be inspected, which is called a macro inspection. Related to the device to perform.

[0002]

2. Description of the Related Art Macro inspection of the surface of a glass substrate for manufacturing a liquid crystal or a wafer for manufacturing an IC (hereinafter, also referred to as an object to be inspected) is performed by scratching the surface of the substrate or wafer, unevenness in resist coating, photo The inspection is performed by observing the entire surface of the inspection object for a defect or the like in the lithography process. In the conventional macro inspection, an inspector visually inspects and inspects while rotating an object to be inspected using a spotlight-like white diffused light source.

However, in the visual inspection by inspectors, there is a problem that there is a difference in technical level between the inspectors and a variation in the inspection levels due to the physical condition of the inspectors, so that it is difficult to obtain a stable inspection result and the efficiency is not good. is there. Also,
When manufacturing glass substrates for liquid crystal manufacturing, wafers for manufacturing ICs, and the like, surface contamination due to the attachment of fine foreign substances and the like must be avoided. Therefore, inspection steps by humans that cause dust generation should be avoided as much as possible.

[0004] For this reason, it has been proposed to automate the macro inspection process. As such, there is an apparatus disclosed in Japanese Patent Publication No. 6-8789. This apparatus irradiates the wafer surface with light, receives the reflected light from the surface with an ITV camera, acquires a reflected light image of the entire surface of the inspection object, and obtains the reflected light image thus obtained. Is compared with a reflected light image of a normal inspection object measured in advance to perform a macro inspection of the inspection object. In this apparatus, the wafer surface angle and the illumination angle can be variably set while the ITV camera is fixed so that the inspection can be performed while changing the irradiation angle of light on the wafer surface in various ways.

[0005]

However, in such an automatic macro inspection apparatus, a mechanism for variably setting the wafer surface angle and the illumination angle is required. There is a problem that dust may be generated and contaminate the surface of the inspection object. Note that the apparatus disclosed in the above publication performs macro inspection using light directly reflected from the surface of the inspection object, and determines the incident angle of the irradiation light on the inspection object surface and the reflection of the reflected light. A camera is provided at a position where the angles are equal.

However, recently, it has been considered that diffracted light, scattered light, and the like generated according to the repetitive pattern on the surface of the inspection object are to be inspected. In such a case, the reflection angle of the reflected light to be inspected changes according to the pattern pitch of the inspection object, and so on. Needs to be adjusted. For this reason,
Also in this case, an angle adjusting mechanism is necessary, and contamination of the surface of the inspection object by dust generated from this mechanism becomes a problem.

The present invention has been made in view of such a problem.
Without variably adjusting the illumination angle, the surface angle of the inspection object, the light receiving angle of the light receiving device or the imaging device, that is,
An object of the present invention is to provide an automatic macro inspection apparatus capable of efficiently performing a macro inspection of various inspection objects while fixing a lighting device, an imaging device, and the like.

[0008]

In order to achieve the above object, an automatic macro inspection apparatus according to the present invention is fixedly disposed at a first predetermined angle with respect to an object to be inspected, and is provided over the entire surface of the object to be inspected. An illumination device for irradiating illumination light having a light beam substantially parallel to the inspection object; and an illumination device fixedly disposed at a second predetermined angle with respect to the inspection object, receiving diffracted light or scattered light from the inspection object and inspecting the inspection object. Image pickup means for picking up an image of an object, image processing means for taking in an image signal obtained by the image pickup means, performing image processing and performing macro inspection of the object to be inspected, and varying the wavelength of illumination light from the illumination device And an illumination wavelength setting means for setting.

In the case of the automatic macro inspection apparatus having such a configuration, since the wavelength of the illumination light can be variably set by the illumination wavelength setting means, the directions of the diffracted light and the scattered light emitted from the inspection object are imaged and photographed. If the wavelength is set so as to match the light receiving direction of the means, efficient macro inspection can be performed. For this reason, in the case of this macro inspection device, the illumination device and the imaging device can be fixed, and a movable mechanism for changing the direction of the device is unnecessary as in the conventional device.
An unnecessary dust source is eliminated, and contamination of the inspection object is suppressed.

It is preferable that the illuminating device is composed of a diffusion light source and parallel conversion means for converting light from the light source into a substantially parallel light beam. In this case, the parallel conversion means is arranged so that the diffusion light source is located at a focal position. It is preferable to constitute the concave mirror arranged. The use of the concave mirror eliminates the problem of chromatic aberration even in the case of illumination using white light. For the same reason, the imaging means is constituted by a concave mirror for converging diffracted light or scattered light from the object to be inspected, and a camera means for taking an image of the object from the light converged by the concave mirror. Is preferred.

Further, the illumination device may be composed of a linear diffused light source and cylindrical lenses opposed to each other along the line of the linear diffused light source.
In this case, the inspection object is illuminated by using the cylindrical lens to generate a light beam that is substantially parallel to the light from the linear diffusion light source in at least one direction.

Here, the wavelength setting by the illumination wavelength setting means is performed as follows. That is, the first predetermined angle is an angle θi with respect to a line perpendicular to the surface of the inspection object, and the second predetermined angle is an angle θd with respect to a line perpendicular to the surface of the inspection object. Sometimes the wavelength λ of the illumination light
Is set so as to satisfy the following equation (1).

[0013]

(Sin θi−sin θd) = n · λ / p (1) where n: the order of diffracted light to be imaged p: pattern pitch on the surface of the inspection object

By setting the wavelength λ of the illumination light in this way,
The imaging means can efficiently capture the nth-order diffracted light and efficiently perform a macro inspection using the diffracted light.

When the macro inspection is performed by capturing the scattered light instead of the diffracted light by the imaging means, the wavelength is set by the illumination wavelength setting means as follows. That is,
The first predetermined angle is an angle θi with respect to a line perpendicular to the surface of the object, and the second predetermined angle is an angle θd with respect to a line perpendicular to the surface of the object. Where λ is the wavelength of the illumination light set by the following equation (2)
Is set by the illumination wavelength setting means so that θd ′ <θd <θd ″ with respect to the angle θd ′ determined by the following equation and the angle θd ″ determined by the following equation (3).

[0016]

(Sin θi−sin θd ′) = n · λ / p (2) (sin θi−sin θd ″) = (n + 1) · λ / p (3) where n: generated from illumination light Order of diffracted light to be emitted p: Pattern pitch on the surface of the inspection object

If the wavelength λ of the illumination light is set in this way, the imaging means is located between the direction of the n-th order diffracted light and the direction of the (n + 1) th order diffracted light. Does not enter and only scattered light is obtained. Therefore, in this case, the macro inspection using the scattered light can be efficiently performed.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below. FIG. 1 shows a schematic configuration according to a first embodiment of an automatic macro inspection apparatus according to the present invention. This apparatus is an illumination optical system that irradiates the surface of a wafer (inspection object) 3 with illumination light of a parallel light flux. The system 100 includes a light receiving system 101 that receives diffracted light, scattered light, and the like from the wafer 3, an imaging device (imaging camera) 6, and an image processing device 7.

The illumination optical system 100 includes a light source 1 and a concave mirror 2.
Composed of The light source unit 1 is disposed at the focal position of the concave mirror 2, and the diffused light from the light source unit 1 is converted into a parallel light beam by the concave mirror 2 and radiated toward the wafer 3. At this time, the concave mirror 2 has a diameter capable of illuminating the entire surface of the wafer 3, and the entire surface of the wafer 3 is simultaneously illuminated by the illumination light of the parallel light flux. The light source unit 1 includes a halogen lamp, which is a white light source, and an interference filter that limits an illumination wavelength range. The interference filter functions as a band-pass filter that transmits light in a predetermined wavelength range, and switches a plurality of interference filters that transmit light in different wavelength ranges from the outside by manual or remote control, and the light emitted from the light source unit 1 Wavelength can be selected.

The light receiving system 101 receives the diffracted light or the scattered light generated from the wafer 3 when the wafer 3 is irradiated as described above, and takes in the diffracted light or the scattered light from the entire surface of the wafer 3. A concave mirror 4 having a sufficient diameter, and a light receiving lens 5 for forming an image of the light incident on the concave mirror 4 and condensed. At this time, the light receiving lens 5
Is formed on the image pickup device 6, and the image of the diffracted light or the scattered light of the wafer 3 is photographed by the image pickup device 6.

The image of the wafer photographed by the image pickup device 6 in this manner is sent to the image processing device 7 and compared with the image of a normal wafer previously photographed and stored therein.
Macro inspection such as surface defect inspection is performed.

In this example, the light source unit 1 is arranged near the front focal point of the concave mirror, and the wafer 3 is arranged near the rear focal plane of the concave mirror 4, whereby a concave reflecting mirror is used. It is a reflection type telecentric optical system.
Since the concave mirror is used in the optical system, there is no problem of chromatic aberration, and a highly accurate inspection can be performed.

An example in which a macro inspection of the wafer 3 is performed by using the automatic macro inspection apparatus having the above configuration will be described. First,
The wafer 3 is transferred to the inspection position shown in FIG. 2 by a transfer mechanism (not shown). Then, the interference filter of the light source unit 1 is selected corresponding to the above arrangement and the type of inspection. In this example, the illumination optical system 100 and the light receiving system 101 are fixedly arranged, the incident angle of the illumination light from the illumination optical system 100 to the wafer 3 is always constant, and the diffracted light incident on the light receiving system 101 is Since the diffraction angle is always constant, the interference filter is selected so that the desired inspection light is incident on the light receiving system 101.

This will be described in detail with reference to FIGS. As shown in FIG. 3, when a repetitive pattern is provided at the basic pitch p on the surface of the wafer 3, the incident angle θi of the illumination light and the emission angle θd of the diffracted light
Is as shown in the following equation (4).

[0025]

(Sinθi−sinθd) = n · λ / p (4) where λ: wavelength of illumination light n: order of diffracted light to be imaged

For this reason, the illumination optical system 100 is provided so that the parallel light beam illumination is performed on the wafer 3 from the direction in which the incident angle becomes the angle θi, and the concave mirror 4 faces the reflection angle θd of the diffracted light. It is understood that when the light receiving system 101 is disposed such that the light is located, the light receiving system 101 can most efficiently receive the n-th order diffracted light when the wavelength of the illumination light is λ.
In this example, the illumination optical system 100 and the light receiving system 101 are fixedly arranged, and the wavelength λ is such that the n-th order diffracted light is most efficiently received by the light receiving system 101 with respect to the arrangement position. The interference filter is selected as follows.

On the other hand, there is a case where the macro inspection is performed by receiving the scattered light by the light receiving system 101. In this case, as shown in FIG. 4, the emission angle θd ′ of the n-th order diffracted light and (n +
1) The wavelength λ of the illumination light is set so that the concave mirror 4 of the light receiving system 101 is located at a position between the emission angle θd ″ of the next diffracted light.
Is set. Specifically, the emission angle θ of the n-th order diffracted light
d ′ is determined by the following equation (5), and the emission angle θd ″ of the (n + 1) th-order diffracted light is determined by the following equation (6).
Angle θd of the diffracted light incident on the concave mirror 4 is θd ′ <θ
The illumination light wavelength λ such that d <θd ”is set by the illumination wavelength setting means.

[0028]

(Sinθi−sinθd ′) = n · λ / p (5) (sinθi−sinθd ″) = (n + 1) · λ / p (6)

When the wavelength λ is selected as described above, when the illumination light of this wavelength is applied to the wafer 3, the n-th order diffracted light is emitted in the direction of the angle θd 'as shown in FIG. Then, the (n + 1) th order diffracted light is emitted in the direction of θd ″,
Since the concave mirror 4 of the light receiving system 101 is located between them,
No diffracted light enters the light receiving system 101, only scattered light is received, and an efficient macro inspection using scattered light is performed.

Here, returning to the original state, the diffracted light or the scattered light received by the light receiving system 101 as described above is condensed on the light receiving lens 5 by the concave mirror 4 and is also reflected on the image sensor 6 by the light receiving lens 4. Is imaged. The image information photographed by the image pickup device 6 in this manner is sent to the image processing device 6, and is compared with the image of the normal wafer, and the macro inspection is automatically performed.

The apparatus for supporting the wafer 3 at the inspection position may be provided with a rotation support mechanism so that the rotation position of the wafer 3 can be adjusted. In this case, when the illumination light, the intensity of the diffracted light, and the direction in which the scattered light is generated differ depending on the rotational position, such as the pattern direction of the wafer 3 and the scratch defect, the wafer 3 is most rotated and inspected. It can be set in a direction that is more efficient.

Although the concave mirror is used in the above embodiment, a reflection type Fresnel zone plate may be used instead. Further, a lens obtained by performing chromatic aberration correction with a refractive optical system using a lens can also be used.

Next, a second embodiment of the automatic macro inspection apparatus according to the present invention will be described with reference to FIG. In addition,
In the apparatus of this example, the same parts as those of the apparatus of the first embodiment are denoted by the same reference numerals and described. This device includes an illumination optical system 102, a light receiving system 101, an image sensor 6, and an image processing device 7, and only the illumination optical system 102 is a first optical system.
It is different only from the device of the embodiment of FIG.

The illumination optical system 102 includes a light source unit 10, an optical fiber light transmission system 11 and a cylindrical lens 12, and irradiates the wafer 3 with a light beam capable of illuminating the entire surface of the wafer 3. The light source unit 10 includes a halogen lamp that is white light source light, and an interference filter that limits an illumination wavelength range. This is the same configuration as the first embodiment.

The optical fiber transmission system 11 has one end (incident end) facing the light source 10 to receive the illumination light from the light source 10 and the other end (emission end) in a one-dimensional line shape. It is arranged and configured. Therefore, the optical fiber transmission system 11
The light beam emitted from the other end of the light source is diffused light having a spread angle of θ in a plane parallel to the paper surface of FIG. 2, and a light source having a depth corresponding to the fiber line length in a direction perpendicular to the paper surface. Become.

The other end of the optical fiber light transmission system 11 is located at a position to be the rear focal point of the cylindrical lens 12, and the diffused light emitted from the other end of the optical fiber light transmission system 11 is a cylindrical lens. 12, the light is converted into a light flux close to a parallel light flux in a plane parallel to the paper surface. This allows
At least in a plane parallel to the plane of FIG. 2, a parallel light beam equivalent to the telecentric optical system shown in the first embodiment is irradiated onto the entire surface of the wafer 3.

When the wafer 3 is irradiated with the illuminating light as described above, the diffracted light or the scattered light generated by the illuminating light is converted into the light receiving system 1.
01, an image is picked up by the image pickup device 6, image processing is performed in the image processing device 7, and macro inspection is performed. However, since this is the same as in the first embodiment, description thereof will be omitted.

In the case of the macro inspection apparatus having such a configuration, the configuration of the illumination optical system can be reduced in size, size, and cost.

In the first and second embodiments, the light source may be constituted by combining a white light source and a spectroscope.

[0040]

As described above, according to the present invention,
An illumination device fixedly disposed at a first predetermined angle; an imaging unit fixedly disposed at a second predetermined angle and imaging an image of the inspection object by diffracted light or scattered light; Image processing means for performing macro-inspection of the inspection object from the image obtained, and furthermore, it is configured such that the wavelength of the illumination light can be variably set by the illumination wavelength setting means. If the wavelength is set so that the directions of the light and the scattered light coincide with the light receiving direction of the imaging unit, efficient macro inspection can be performed. For this reason, in the case of this macro inspection device, the illumination device and the imaging device can be fixed, and a movable mechanism for changing the direction of the device is unnecessary as in the conventional device, and an extra dust source is not generated. As a result, contamination of the inspection object can be suppressed.

It is preferable that the illuminating device is composed of a diffusion light source and parallel conversion means for converting light from the light source into a substantially parallel light beam. In this case, the parallel conversion means is arranged so that the diffusion light source is located at the focal position. It is preferable to constitute the concave mirror arranged. The use of the concave mirror eliminates the problem of chromatic aberration even in the case of illumination using white light. For the same reason, the imaging means is constituted by a concave mirror for converging diffracted light or scattered light from the object to be inspected, and a camera means for taking an image of the object from the light converged by the concave mirror. Is preferred.

Also, the illumination device can be composed of a linear diffused light source and cylindrical lenses arranged opposite to each other along the line of the linear diffused light source.
In this case, the inspection object is illuminated by using the cylindrical lens to generate a light beam that is substantially parallel to the light from the linear diffusion light source in at least one direction. In this way, the size and size of the lighting device can be reduced, and the cost can be reduced.

When the macro inspection using the diffracted light is performed, the wavelength setting by the illumination wavelength setting means is made to satisfy the above-mentioned equation (1). This equation (1) is a condition for diffracted light to be emitted toward the light receiving system (imaging means), whereby the n-th order diffracted light is efficiently captured by the imaging means, and this diffracted light is used. Macro inspection can be performed efficiently.

When the macro inspection is performed by capturing the scattered light instead of the diffracted light by the imaging means, the wavelength setting by the illumination wavelength setting means is performed by the angle θd ′ determined by the above equation (2).
And the angle θd ″ determined by the above equation (3), the wavelength λ of the illumination light is set by the illumination wavelength setting means so that θd ′ <θd <θd ″. When the wavelength λ of the illumination light is set in this manner, the imaging unit is located between the direction of the n-th order diffracted light and the direction of the (n + 1) th order diffracted light, and the diffracted light is incident on the imaging unit. Scattered light only. Therefore, in this case, the macro inspection using the scattered light can be efficiently performed.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an automatic macro inspection apparatus according to a first embodiment of the present invention.

FIG. 2 is a schematic view showing an automatic macro inspection apparatus according to a second embodiment of the present invention.

FIG. 3 is an explanatory diagram showing a relationship between illumination light and diffraction light applied to a wafer.

FIG. 4 shows the illumination light applied to the wafer and the n-th order light and (n +
1) It is an explanatory view showing the relationship between the next diffracted light and the position of the concave mirror of the light receiving system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1,10 Light source part 2,4 Concave mirror 3 Wafer 5 Light receiving lens 6 Image sensor 7 Image processing device 11 Optical fiber light transmission system 12 Cylindrical lens 100,102 Illumination optical system 101 Light receiving system

Claims (7)

[Claims] An illumination device fixedly arranged to face an object to be inspected at a first predetermined angle and irradiating illumination light having a light flux substantially parallel to the entire surface of the object to be inspected; The inspection object is fixedly disposed opposite to the inspection object at a second predetermined angle, receives the diffraction light or the scattered light generated by the irradiation of the illumination light from the inspection object, and forms an image of the inspection object. Imaging means for taking an image; image processing means for taking in an image signal obtained by the imaging means, performing image processing and performing a macro inspection of the object to be inspected, and variably setting a wavelength of illumination light from the illumination device. An automatic macro inspection apparatus comprising: an illumination wavelength setting unit. 2. The automatic macro inspection apparatus according to claim 1, wherein the illumination device includes a diffused light source and a parallel conversion unit that converts light from the diffused light source into a substantially parallel light flux. 3. The automatic macro inspection apparatus according to claim 2, wherein said parallel conversion means comprises a concave mirror arranged so that said diffused light source is located at a focal position. 4. The image pickup means forms a concave mirror for converging the diffracted light or scattered light from the test object, and forms an image of the test object from the diffracted light or scattered light converged by the concave mirror. The automatic macro inspection apparatus according to any one of claims 1 to 3, further comprising a camera means for taking an image by making an image. 5. The illumination device comprises a linear diffused light source and a cylindrical lens disposed to face the line of the linear diffused light source, and the light from the linear diffused light source is provided by the cylindrical lens. 2. The automatic macro inspection apparatus according to claim 1, wherein a light beam substantially parallel to at least one direction is generated to illuminate the inspection object. 6. The apparatus according to claim 1, wherein the first predetermined angle is an angle θi with respect to a line perpendicular to the surface of the object, and the second predetermined angle is an angle θi with respect to a line perpendicular to the surface of the object. Angle θd
Where, the wavelength λ of the illumination light set by the illumination wavelength setting means is given by the following equation: (sin θ i −sin θ d) = n · λ / p where n: the order of the diffracted light to be imaged p: 2. The method according to claim 1, wherein the pattern pitch is set so as to satisfy a pattern pitch of a surface of the inspection object.
An automatic macro inspection apparatus according to item 1. 7. The method according to claim 1, wherein the first predetermined angle is an angle θi with respect to a line perpendicular to the surface of the object to be inspected, and the second predetermined angle is an angle θi with respect to a line perpendicular to the surface of the object to be inspected. Angle θd
Where λ is the wavelength of the illuminating light set by the illuminating wavelength setting means, the following equation is given: (sin θi−sin θd ′) = n · λ / p where n: diffraction light generated from the illumination light Order p: θd ′ <θd <θd ″, where θd ′ is determined by the pattern pitch of the surface of the inspection object and θd ″ is determined by (sinθi−sinθd ″) = (n + 1) · λ / p. 2. The automatic macro inspection apparatus according to claim 1, wherein the wavelength [lambda] of the illumination light is set by the illumination wavelength setting unit.