JPH09171149A - Wafer character reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an erect reflected image with a high contrast, reduce the size, and confirm the focus position of an optical element with the naked eye. SOLUTION: A light source means 2 is arranged above a sample 3. Light from the light source means 2 which irradiates the sample 3 is converted by a collimator lens 4 from diverged light to parallel light, which is passed through a half-mirror 5 to irradiate the sample 3. The reflected light from the sample 3 is bent by a half-mirror 5 to a right-angled direction and made incident on a 2nd collimator lens 6. The reflected light made incident on the 2nd collimator lens 6 is converged on the focus position. Reflected light which is made incident on a reflecting mirror 7 arranged almost on the rear image space focal plane of the 2nd collimator lens 6 is reflected by a reflecting mirror 7 and made incident on an image pickup means 10, which reads its real image.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wafer character reader, and more particularly to a wafer character reader having an improved telecentric optical system.

[0002]

2. Description of the Related Art Conventionally, a so-called telecentric optical system in which a transmitted or reflected light is converged by an optical element to an apparatus for inspecting a glass substrate, a semiconductor wafer or the like, and then an aperture stop is arranged in an image space focal plane. Often used. For example, the inspection device shown in FIG. 11 to FIG. 12 sends a light source 32, a first collimator lens 34 that makes light emitted from the light source 32 a parallel light beam, and light from the first collimator lens 34 to the sample 33. Half mirror 3
5, the sample 33 mounted on the stage, the second collimator lens 36 that collects the reflected light, the aperture stop 37 that is arranged behind the second collimator lens 36 and around its focal point, and its real image. And an imaging device 40 for imaging. The image pickup device 40 is arranged coaxially with the second collimator lens 36, and is of a type (FIG. 11) that directly takes an image of light that is condensed and imaged by the second collimator lens 36. The light that is condensed and imaged is divided into a type (FIG. 12) in which the mirror 38 changes the direction by 90 degrees.

By disposing the above-mentioned aperture stop 37 in the focal plane of the rear image space of the second collimator lens 36, the scattered light scattered by the unevenness of the sample surface is completely blocked, and the surface condition of the entire sample is obtained. Is being observed in real time and accurately.

[0004]

However, arranging the conventional aperture stop around the rear image space focal plane of the second collimating lens (optical element) increases the distance in the optical axis direction. The problem remains that it is difficult to downsize the inspection device itself. In particular, as shown in FIG. 12, in the type in which the mirror 38 is arranged in front of the image pickup device, the image pickup device must be provided in the direction perpendicular to the optical axis, and thus the size must be increased. .

Further, when it is desired to filter the wavelength of the reflected light from the sample, it is necessary to separately install an infrared cut filter or the like in the optical path, which also leads to an increase in the size of the inspection apparatus.

Further, in the case of the aperture stop, ideally, the aperture stop should be arranged on the focal plane of the second optical element, but since the aperture stop is a hole and light passes through, the degree of convergence of light is increased. However, there is also a problem that it is impossible to confirm whether or not the focal point is definitely located.

The present invention is applied to a wafer character reading device by applying an optical system used in a conventional inspection device. In order to solve various problems in the above-described inspection device, a positive contrast having a high contrast is used. An object of the present invention is to provide a wafer character reading device which can obtain a reflected image, can be miniaturized, and can visually confirm the position arranged on the focal plane of the second optical element.

[0008]

SUMMARY OF THE INVENTION In a wafer character reading apparatus according to the present invention, a light source means for emitting light at a right angle or an oblique direction to a sample and divergent light emitted from the light source means are converted into parallel light. A wafer character reading device comprising optical element means for condensing the transmitted light or reflected light and an image pickup means for reading a real image of the reflected light condensed by the optical element means, the wafer character reading device comprising: It is characterized in that a reflecting mirror is arranged on or near the image space focal plane.

The optical element means may include a first optical element for converting divergent light into parallel light and a second optical element for condensing transmitted light or reflected light.

Furthermore, it is even more preferable that the center of the reflecting mirror is aligned with the center of the optical axis of the second optical element.

Further, the reflection mirror may be divided into a plurality of types and arranged in one plate.

Further, the wafer character reading apparatus includes a light source means for emitting light in a direction perpendicular to the sample, a first optical element for converting divergent light emitted from the light source means into parallel light, and the first optical element. A half mirror disposed between the element and the sample, a second optical element that collects the reflected light from the half mirror, a rear image space focal plane of the second optical element,
Alternatively, it is configured by including a reflection mirror arranged in the vicinity thereof and an image pickup device for picking up a real image by the reflection mirror.

Further, the present invention is a sample surface inspection apparatus, and the sample surface inspection apparatus according to the present invention includes light source means for emitting light in a direction perpendicular or oblique to the sample surface, and light emitted from the light source means. A sample surface inspection apparatus including optical element means for converting divergent light into parallel light and condensing transmitted light or reflected light thereof, and imaging means for observing a real image of reflected light condensed by the optical element means. Therefore, the reflecting mirror is arranged on the rear image space focal plane of the optical element means or in the vicinity thereof.

Further, the wafer character reading apparatus of the present invention converts the divergent light emitted from the light source means emitted in a direction perpendicular or oblique to the sample into parallel light and transmits the transmitted light. Or a wafer character reading device comprising an optical element means for condensing reflected light and an imaging means for reading a real image of the reflected light condensed by the optical element means, wherein a rear image space focal plane of the optical element means, Alternatively, a reflecting mirror is arranged in the vicinity thereof, and the reflecting mirror has an elliptical mirror aperture stop formed in a plurality of elliptical or substantially elliptical shapes having different sizes. .

Preferably, a plurality of elliptical mirror aperture stops having different sizes are concentrically arranged on the circular plate, and the circular plate is rotatably arranged at its center. I wish I had it.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings.

The wafer character reading device according to the present invention is
It is suitable for use in operations such as character recognition, collation, classification, and sorting of wafers whose ID numbers are marked with a laser or the like, and FIG. 1 is an overall view of a wafer character reading device 1 according to an embodiment. It is shown.

The light source means 2 is arranged above the sample, and is configured as a point light source that emits light emitted from a light emitting source such as a halogen by an optical element such as a concave mirror or a lens and emits it from a pinhole. Has been done. In this case the sample is
The wafer 3 is marked with an ID number.
The light source means 2 emits a light beam in a direction perpendicular to the sample 3,
The emitted light is converted into parallel light by a first collimator lens 4 as an optical element, passes through a half mirror 5 arranged at an intermediate position between the first collimator lens 4 and the sample 3, and the sample 3 To irradiate.

The half mirror 5 is used for splitting the outgoing light into the orthogonal direction with respect to the incident light. In this case, the light reflected from the sample 3 is bent in the orthogonal direction by the half mirror 5, and the second collimator is used. The light passes through the lens 6 and is condensed at the focal position. At this time, of the reflected light reflected by the sample 3, only the specularly reflected light having the same optical axis as the incident light is
The light is focused on the focal position by the collimator lens 6. However, the scattered light that is diffusely reflected on the surface of the sample and has an angle different from that of the incident light is not condensed at the focal position even when passing through the collimator lens 6.

A circular reflection mirror 7 is disposed at a focal position on the rear image space focal plane of the second collimator lens 6 at an angle of 45 ° with the optical axis. Even if the angle between the optical axis and the reflection mirror 7 is not 45 °, an appropriate angle can be set as appropriate. Also, on the reflecting surface of the reflecting mirror 7,
For example, if a thin film that absorbs infrared rays is coated, it is not necessary to provide a new filter for filtering the wavelength of reflected light. Further, the size of the reflection mirror 7 is arbitrary, but by disposing a mirror having a smaller diameter in the converging spot 9 formed by the second collimating lens 6, specular reflection light only near the center of the converging axis can be obtained. You can take it out. Therefore, as shown in FIGS. 2 to 3, the reflection mirrors 7a, 7b, and 7c having different sizes are set to one.
If the black matting plates 8 are arranged side by side on the black matting plates 8 so that the respective reflection mirrors 7 can move to the converging spots 9, the brightness can be adjusted and the optical axis near the optical axis can be adjusted. The reflection component can be extracted. The light ray K1 in FIG.
The case where the reflection mirror is large (7a) is shown, and the light ray K2 shows the case where the reflection mirror is small (7c).

The reflected light whose traveling direction is changed by 45 ° by the reflection mirror 7 forms a real image on the image pickup means 10,
It is possible to read an image formed only by the specularly reflected light reflected from the sample.

For example, as shown in FIG.
In the case of a semiconductor wafer marked with the number N, I
Since the wafer surface portion H that is not the D number N is the same as the mirror surface, the light incident as parallel light from the vertical direction is directly reflected as parallel light. On the other hand, since the portion of the ID number N is engraved by a laser or the like, the surface has an uneven shape, and parallel light from the vertical direction is diffusely reflected by the uneven surface.

The diffused reflected light of the ID number N portion incident on the second collimator lens 6 at an angle cannot be condensed on the focal point of the second collimator lens 6 and becomes black in terms of contrast. Further, the regular reflection light is condensed by the second collimator lens 6, is reflected by the reflection mirror 7, enters the image pickup device, and becomes white in terms of contrast. Therefore, the ID number N of the wafer 3 can be read as black characters on a white background.

FIG. 5 shows another embodiment of the wafer character reading device, which is constructed so that the flow of light rays is opposite to that of the wafer character reading device 1.

The wafer character reading device 11 includes a sample 13
On the other hand, the light source means 12 arranged in the upper right direction, and the first collimator lens 14 arranged in parallel with the light source means 12 and converting the light beam emitted from the light source means 12 from divergent light to parallel light. A half mirror 15 which is arranged above the sample 13 and splits incident parallel light into the sample 13 in the vertical direction.
A second collimating lens 16 for converging the light reflected by the sample 13 and passing through the half mirror 15, and a reflecting mirror 17 positioned on the focal plane of the rear image space of the second collimating lens 16 and its combination. And an image pickup means 20 for picking up an image.

The center of the reflection mirror 17 is arranged so as to substantially coincide with the optical axis center of the second collimator lens 16,
The reflecting surface of the reflecting mirror 17 may be coated with an infrared absorbing thin film as described above. Then, several types of reflecting mirrors 17 having different sizes are used for one black matting plate 1.
8 may be mounted and arranged in the same manner as in the wafer character reading device 1 described above. In this case, the real image appears as an image opposite to the sample, but it may be dealt with by image processing.

The wafer character reading device shown in FIG.
It shows one embodiment in which the irradiation of the sample from the light source means is performed in an oblique direction, that is, in oblique light.

The wafer character reading device 21 can omit the half mirror, and has a light source means 22 arranged at an angle of about 45 ° to the upper right with respect to the sample 23 and a divergence incident from the light source means 22. The first collimator lens 24 that converts light into parallel light, the second collimator lens 26 that is disposed on the extension line of the optical axis reflected from the sample 23, and focuses the light on the focus, and the second collimator lens 26. It is configured to include a reflecting mirror 27 located on the focal plane of the rear image space and an image pickup means 30 for picking up an image thereof.

The center of the reflection mirror 27 is arranged so as to be substantially coincident with the center of the optical axis of the second collimator lens 24, and is attached at an angle of about 45 ° with respect to the reflected light of the sample 23. Then, on the anti-slope surface of the reflection mirror 27, the
Infrared filter is coated. Also in this case, the real image appears as an image opposite to the sample, but it can be dealt with by image processing.

As shown in FIG. 7, it is also possible to move the light source means 22 or the first collimator lens 24 in FIG. 6 and change the positional relationship between them to irradiate the sample with divergent light. In this case, since the divergent light is incident on the parallel light in an oblique direction, the specularly reflected light from the sample surface formed on the mirror surface is second collimator lens 26.
Of the irregularly reflected light from the ID number part becomes parallel light, which coincides with the optical axis toward the second collimator lens 26 and is incident on the second collimator lens 26.
Then, the reflected light from the surface of the wafer 3 having no unevenness becomes the second light.
Since the collimator lens 26 cannot focus light, the contrast becomes black, and the reflected light from the ID number part is the second
The light is focused by the collimator lens 26 and enters the image sensor, so that the contrast becomes white. Therefore, as opposed to the wafer character reading device 1, the ID number can be read as white characters with black as the background.

A reflection mirror may be additionally provided in the middle of the optical path to change the optical path. in this case,
Since the real image is read in the same shape as the sample 3, it does not have to be dealt with by image processing.

Further, the light source means 22 is a line fiber 22A for irradiating a line shape, and the first collimating lens 2 is used.
If 4 is changed to the cylindrical lens 24A, only the ID number N on the wafer can be efficiently irradiated as shown in FIG.

In the wafer character reading devices 1, 11, and 21 according to the above-described embodiment, as shown in FIG. 9, the observation means such as the viewing window 41 and the small CCD camera is provided at the position where the reflection mirror can be observed. By observing the focal plane of the second collimator lens, the optimum position of the reflection mirror can be confirmed, and the focus state of the second collimator lens can be confirmed.

Further, as shown in FIG. 10, a half mirror 47 is used as the reflection mirror to observe the size of the focused spot, and a separate eyepiece lens 42 is attached to allow regular reflection from the sample even with the naked eye. Images can be observed simultaneously.

The wafer character reading device of the present invention can be used and applied not only as a wafer character reading device but also as a sample surface inspection device for inspecting unevenness on the sample surface.

In the wafer character reading device shown in FIGS. 13 to 14, the reflecting mirror has an elliptical mirror aperture stop.

The wafer character reading device 51 includes a sample 53.
On the other hand, the light source means 52 arranged in the upper right direction, the condenser lens 54 arranged in parallel with the light source means 52 and converting the light beam emitted from the light source means 52 from divergent light to parallel light, and the sample 53. A half mirror 55A that is arranged above the beam splitter and splits incident parallel light into the sample 53 in the vertical direction.
And passes through the half mirror 55A, and the half mirror 55A
And a total reflection mirror 55B arranged in parallel with the half mirror 55A above the second reflection mirror 55B, and the light reflected from the sample 53 is bent at a right angle to the total reflection mirror 55B and focused on the second focus.
The collimator lens 56, the reflection mirror 57 located in the rear image space focal plane of the second collimator lens 56, and the image pickup means (CCD camera or the like) 60 for picking up an image thereof are configured.

As shown in FIG. 14, the reflection mirror 57 includes a mirror support board 58 as a circular plate formed of a glass body, and an incident side surface portion 58a of the mirror support board 58.
And the elliptical mirror aperture stops 57a, 57b, 57c, 57d, 57 of different sizes which are concentrically deposited and arranged.
and a portion other than the elliptical mirror aperture diaphragms 57a, 57b, 57c, 57d, and 57e of the incident side surface portion 58a is subjected to a treatment such as a black matte coating to prevent reflection. The reflection mirror 57 is rotatably arranged at the center of the mirror support board 58, and the centers of the elliptical mirror aperture stops 57a, 57b, 57c, 57d, and 57e (centers of the mirror support board 58) are the second collimator lenses 56. Is rotated to a predetermined position so as to substantially coincide with the optical axis center of the.

Each elliptic mirror aperture stop 57a, 5
The reflecting surfaces of 7b, 57c, 57d and 57e are the same as above.
An infrared absorbing thin film may be coated.

Since the elliptic mirror aperture stop having five stages is arranged in this way, for example, when the amount of light is required in the dark, the largest elliptic mirror aperture stop 57a may be set. When the amount of light is not so high when it is bright, the smallest elliptic mirror aperture stop 57e may be set. Therefore, each elliptical mirror aperture stop can be adjusted according to an appropriate light amount.

The elliptic mirror aperture stop is not limited to being set in five stages, but may be in any number of stages as necessary. Also, the shape is not limited to an ellipse,
It may be formed in a substantially elliptical shape. In any case, the reflection mirror 57 may be formed so as to have a shape close to a circle when viewed from a direction parallel to the optical axis when the reflection mirror 57 is tilted at about 45 °.

[0042]

According to the wafer character reader of the present invention, the aperture stop in the conventional telecentric optical system is abolished, and the reflection mirror is arranged around the focal plane of the rear image space of the optical element. The light of only the specular reflection component from is reflected and enters the image pickup means. Therefore, a specular reflection image with high contrast can be obtained.

Further, the installation of the mirror makes it possible to reduce the size of the system, which has conventionally been increased in size by disposing the aperture stop.

Furthermore, by coating the surface of the reflecting mirror with an infrared absorbing thin film, it is not necessary to install a new filter, and the size can be reduced.

Further, by disposing a plurality of reflecting mirrors having different sizes in a single plate, it is possible to adjust the brightness and extract the specular reflection component near the optical axis.

Further, the reflection mirror has a plurality of elliptical mirror aperture stops of different sizes formed in an elliptical or substantially elliptical shape, and the elliptical mirror aperture stops are concentric with the center of the circular plate. Since it is arranged, an appropriate amount of light can be selected by rotating the circular plate about its center.

[Brief description of the drawings]

FIG. 1 is a wafer character reading device showing an embodiment of the present invention.

FIG. 2 is a front view in which reflecting mirrors of different sizes are arranged.

FIG. 3 is a side view of FIG. 2;

FIG. 4 is a diagram showing a state in which a wafer is irradiated with light.

FIG. 5 is a wafer character reading device showing another embodiment of the present invention.

FIG. 6 is a wafer character reading device showing another embodiment of the present invention.

FIG. 7 is a view showing another form of the wafer character reading device in FIG.

FIG. 8 is a view showing another form of the wafer character reading device in FIG.

FIG. 9 is a diagram showing an observation state of a reflection mirror.

10 is a view showing the wafer character reading device in FIG. 1 provided with an eyepiece lens.

FIG. 11 Conventional inspection device

FIG. 12 Conventional inspection device

FIG. 13 is a wafer character reading device showing another embodiment of the present invention.

FIG. 14 is a detailed view showing the elliptical mirror aperture stop in FIG.

[Explanation of symbols]

1, 11, 21, 51 ... Wafer character reading device 2, 12, 22, 52 ... Light source means 3, 13, 23, 53 ... Sample (wafer) 4, 14, 24 ... First optical element (first collimating lens) 5, 15, 55 ... Half mirror 6, 16, 26 ... Second optical element (second collimating lens) 7, 17, 27, 57 ... Reflection mirror 10, 20, 30, 60 ... Imaging means 57a, 57b, 57c, 57d, 57e ... Elliptical mirror aperture stop 58 ... Mirror support board (circular plate)

Claims (8)

[Claims] 1. A light source means for emitting light in a direction perpendicular or oblique to a sample, and an optical element for converting divergent light emitted from the light source means into parallel light and condensing transmitted light or reflected light thereof. A wafer character reading device comprising: means and an image pickup means for reading a real image of the reflected light condensed by the optical element means, wherein a reflection mirror is provided at or near a rear image space focal plane of the optical element means. A wafer character reading device characterized by: 2. The optical element means comprises a first optical element for converting divergent light into parallel light, and a second optical element for condensing transmitted light or reflected light thereof. 1. The wafer character reading device described in 1. 3. The wafer character reading device according to claim 1, wherein the center of the reflection mirror coincides with the center of the optical axis of the second optical element. 4. The wafer character reading device according to claim 1, wherein the reflection mirror is arranged by being divided into a plurality of types within one plate. 5. A light source means for emitting light in a direction perpendicular to the sample, a first optical element for converting divergent light emitted from the light source means into parallel light, and an arrangement between the first optical element and the sample. A half mirror provided, a second optical element that collects the reflected light from the half mirror, a reflection mirror that is arranged at or near the rear image space focal plane of the second optical element, and the reflection A wafer character reading device, comprising: an image pickup device that picks up a real image of light reflected by a mirror. 6. A light source means for emitting light at a right angle or an oblique direction with respect to a sample surface, and an optical for converting divergent light emitted from the light source means into parallel light and condensing transmitted light or reflected light thereof. What is claimed is: 1. A sample surface inspection apparatus comprising: an element means and an image pickup means for observing a real image of the reflected light condensed by the optical element means, wherein a reflection mirror is provided at or near the rear image space focal plane of the optical element means. A sample surface inspection device characterized by being provided. 7. A light source means for emitting light at a right angle or an oblique direction to a sample, and an optical element for converting divergent light emitted from the light source means into parallel light and condensing transmitted light or reflected light thereof. Means and an image pickup means for reading a real image of the reflected light condensed by the optical element means, wherein a reflecting mirror is arranged at or near the rear image space focal plane of the optical element means. The wafer mirror reading device is characterized in that the reflecting mirror has a plurality of elliptical or substantially elliptical elliptical mirror aperture stops having different sizes. 8. A plurality of elliptical mirror aperture stops of different sizes are concentrically arranged on a circular plate, and the circular plate is rotatably arranged at its center. Wafer character reading device.