JPH0771911A - Position detecting device - Google Patents

Abstract

PURPOSE:To precisely detect the position of a base plate surface by arranging a light shielding member for shielding a reflected light between conjugate positions to the surface and reverse surface of the base plate in an objective optical system, and removing the reflected light from the reverse surface of the base plate. CONSTITUTION:In the infrared ray from a light source 1, the half of its luminous flux is shielded 4, and the other half luminous flux L1 is converged on the surface of a base plate 7 through a half mirror 5 and an objective lens 6. The luminous flux L3 reflected by the reverse surface of the base plate 7 is passed through the mirror 5, reflected by a dichroic mirror 10, converged at a conjugate position B concerning the lens 6, and then shielded by a light shielding plate 9. Thus, only the luminous flux L2 reflected by the surface of the base plate 7 is similarly converged once at a conjugate position A concerning the lens 6, and converged on the light receiving surface of a photoelectric detector 8 by a relay optical system 20. Two photoelectric signals obtained from detecting areas 8a, 8b of the light receiving surfaces are outputted to an object face detecting part 14, and the position of the base plate 7 surface to the object surface (reference plane) P0 of the lens 6 is detected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a position detecting device for detecting the position of a substrate as an object to be inspected, for example, a device suitable for focus detection of a microscope.

[0002]

2. Description of the Related Art A focus detecting device used in an epi-illumination type microscope is known, for example, from US Pat. No. 3,721,827. Therefore, the focus detection device disclosed in US Pat. No. 3,721,827 will be specifically described with reference to FIG.

In FIG. 7, (a) shows a focused state, (b) shows
Shows the front pinned state, and (c) shows the rear pinned state. First, as shown in FIG. 7A, the light from the light source 1 is condensed by the condenser lens 2 and the slit plate 3 having the slit-shaped opening is illuminated to form a slit-shaped light source. Then, of the light beams passing through the slit plate 3 which is divided into two by the surface including the optical axis of the condenser lens 2 (the surface perpendicular to the paper surface in the figure), half of one light beam (lower light beam) is shielded. The light is shielded by the plate 4, and half of the other light flux (upper light flux) L
₁ reflects the half mirror 5. Then, the light flux L ₁ reflected by the half mirror 5 passes through the left half of the objective lens 6 (the left half of the pupil of the objective lens 5) and the surface 70 to be inspected.
It is condensed on (the object plane of the objective lens 6).

The slit plate 3 is provided on the surface 70 to be inspected.
The image of the opening of the image is formed, and the light flux L ₂ reflected on the surface 70 to be inspected passes through the right half of the objective lens 6 (the right half of the pupil of the objective lens 5) and then the half mirror 5. Then, the light is collected on the light receiving surface of the photoelectric detector 8, and an image of the opening of the slit plate 3 is formed here. The light receiving surface of the photoelectric detector 8 has light receiving areas 8a and 8b on the left and right with the area intersecting the optical axis Ax of the objective lens 6 as a boundary, and the image forming state of the image of the opening of the slit plate 3 is photoelectrically converted. To detect.

Further, as shown in FIG. 7B, the surface to be inspected 70
Is located at a position P ₁ below the position P ₀ of the object plane (reference plane or planned focal plane) of the objective lens 6, the test surface 7
Light flux L that is reflected by 0 and passes through the right half of the objective lens 6
₂ is condensed before the light receiving surface of the photoelectric detector 8 and reaches the left side area 8a of this light receiving surface. Here, since the slit image is formed at the condensing position B in front of the light receiving surface of the photoelectric detector 8, the photoelectric detector 8 photoelectrically converts the defocus image of the slit in the front focus state. To detect.

Further, as shown in FIG.
There the located position P ₂ of the upwardly from the position P ₀ of the object plane of the objective lens 6 (reference surface), the light beams passing through the right half of the objective lens 6 is reflected by the test surface 70 is photoelectrically detected Bowl 8
The light reaches the right side region 8b of the light receiving surface so that the light is collected behind the light receiving surface. Then, the photoelectric detector 8 photoelectrically detects the defocus image of the slit in the rear focus state.

Here, the focus detection based on the photoelectric detector 8 is to balance two light amount signals respectively detected in the left and right light receiving regions 8a and 8b of the photoelectric detector 8, that is, to take a differential between the two light amount signals. Done in. For example, in FIG. 7A, the image is in focus, and in this case, the detection light is detected at the center of the light receiving surface of the photoelectric detector 8. Therefore, the outputs of the two light amount signals respectively detected in the left and right side regions 8a and 8b of the light receiving surface become equal, and the differential signal becomes zero.

FIG. 7 (b) shows the front focus state. In this case, the detection light is mainly detected in the area 8a on the left side of the light receiving surface of the photoelectric detector 8. Therefore, the left and right side regions 8 of the light receiving surface
As the differential signal based on the two light amount signals respectively detected by a and 8b, for example, an output signal of a certain positive level is obtained. Further, in FIG. 7C, the rear focus state is set, and in this case, the detection light is mainly detected in the area 8b on the right side of the light receiving surface of the photoelectric detector 8. Therefore, a differential signal based on the two light amount signals respectively detected in the left and right side regions 8a and 8b of the light receiving surface is an output signal of a certain negative level, for example.

In this way, the two obtained from the photoelectric detector 8
By taking the differential of two signals, the direction of defocus can be detected by the positive / negative of the differential signal, and the defocus amount can be detected by the output level of the differential signal.

[0010]

In recent years, the proportion of liquid crystal displays in displays and the like has been rapidly increasing. Therefore, inspection of a liquid crystal substrate, which is a source of liquid crystal display, has become important, and this liquid crystal substrate is mainly inspected by a microscope. However, when trying to focus on the surface of the liquid crystal substrate using the microscope equipped with the focus detection device described above, not only the reflected light from the surface of the liquid crystal substrate that should be originally detected, but also the reflected light from the back surface of the liquid crystal substrate. Even the light reaches the photoelectric detector, which has a great influence on the focus detection accuracy.

Therefore, since the surface of the liquid crystal substrate cannot be accurately inspected in a focused state, there is a problem that a defective product cannot be accurately discriminated. Therefore, the present invention has been made in view of the above problems, and a position that can detect the position of the front surface of the substrate with high accuracy even when reflected light from the back surface of the substrate including the liquid crystal substrate is generated. The purpose is to provide a detection device.

[0012]

In order to achieve the above object, the present invention provides an optical axis A of an objective optical system 6 as shown in FIG.
Light that has passed through one of the first regions, which is divided into two parts with the surface including x as a boundary, is projected onto the surface 7a of the substrate, and the light reflected from the surface 7a of the substrate includes the optical axis of the objective optical system 6. In the position detecting device for detecting the position of the substrate 7 by photoelectrically detecting with the detector 8 through the other second region divided into two with the surface as a boundary, the objective optical system 6 and the detector 8 , And the surface 7a of the substrate condensed by the objective optical system 6 at a predetermined position.
In the case where the relay optical system 20 for condensing the reflected light from the detector 8 on the light receiving surface of the detector 8 is arranged and the substrate 7 is at the reference position P ₀ (the reference object plane of the objective optical system 6 or the planned focal plane). In relation to the objective optical system 6, the first position A conjugate with the surface 7a of the substrate and the substrate 7 are at the reference position P ₀ (reference object plane or planned focal plane of the objective optical system 6). A light blocking member 9 for blocking the reflected light from the back surface 7b of the substrate through the second region is arranged between the back surface 7b of the substrate and the second position B which is conjugate with the second position B from the first position A. Assuming that the distance L along the optical axis of the objective optical system to the position B and the distance d along the optical axis of the objective optical system from the first position A to the light shielding member 9 are 0 <d <L It is configured to be satisfied.

Based on the above basic structure, the light shielding member 9 is preferably provided so as to be movable in the optical axis direction of the objective optical system 6 according to the thickness of the substrate 7. Further, the objective optical system may be configured to include an objective lens that forms an image of reflected light from the substrate and a re-imaging lens that re-images the reflected light formed by the objective lens at the predetermined position. good.

[0014]

[Operation] Here, the principle of the present invention will be described with reference to FIGS. FIG. 6 is a diagram showing how reflected light from the back surface of the substrate is detected when the conventional focus detection device is focused on the front surface of the substrate. As shown in FIG. 6, the upper half L ₁ of the slit-shaped light flux formed by the light source 1, the condenser lens 2 and the slit plate 3 passes through the left half of the objective lens 6 and is condensed on the substrate 7. . This board 7
The light beam L ₂ reflected by the surface 7a (surface to be inspected) of the objective lens 6 and passing through the right half of the objective lens 6 is once condensed by the objective lens 6 at the position A to form an aerial image. After that, the light is condensed again on the light receiving surface A ′ of the photoelectric detector 8 by the relay optical system 20.

Here, a part of the slit-shaped light flux which passes through the left half of the objective lens 6 and is condensed on the substrate 7 is transmitted through the front surface 7a of the substrate and reflected by the back surface 7b of the substrate. The reflected light L ₃ reflected by the back surface 7b and passing through the right half of the objective lens 6 is once condensed by the objective lens 6 at a position B before the position A, and then relay optics. The system 20 collects light at a position B ′ in front of the light receiving surface 8a of the photoelectric detector 8 and collects it on the right side region 8 of the light receiving surface of the photoelectric detector 8.
The light is received at b.

In this case, the photoelectric signal obtained by the photoelectric detector 8 will be examined. As shown in FIG. 6, since the front surface 7a of the substrate is in focus (the front surface 7a of the substrate is at the reference position P ₀ ), the optical axis Ax of the objective lens 6 is generated by the reflected light from the front surface 7a of the substrate. Although the light amount signals obtained in the left and right light receiving regions of the photoelectric detector with the same sandwiching the
Since the reflected light from the back surface 7b of the substrate is incident on the light receiving region 8b on the right side of the photoelectric detector, defocusing is performed (the front surface 7a of the substrate is below the in-focus position) by an amount corresponding to this incident light amount. It is also detected as being present.

Therefore, in the present invention, as shown in FIG. 5, when the surface 7a of the substrate 7 is at the reference position P ₀ (in focus), the first position conjugate with the surface 7a of the substrate with respect to the objective lens 6. The back surface 7b of the substrate with respect to A and the objective lens 6
A light blocking member 9 for blocking the reflected light from the back surface 7b of the substrate is provided between the second position B and the second position B, which is conjugate with the second position B, on the left side of the optical axis Ax.

By this, only the reflected light from the front surface 7a of the substrate can be efficiently extracted, so that the position of the front surface 7a of the substrate can be detected with extremely high accuracy. Here, as described above, in the light shielding member 9, when the front surface 7a of the substrate is in focus (the front surface 7a of the substrate is at the reference position), the reflected light from the back surface 7a of the substrate is reflected by the objective lens 6. It is preferably arranged between a position A where light is condensed and a position B where light reflected from the back surface 7b of the substrate is condensed by the objective lens 6.

In the above, the detection of the position of the substrate surface where the thickness t of the substrate is constant has been described. However, in order to detect the position of the substrate surface having a different thickness, the light shielding member 9 is used.
Is preferably provided so as to be movable in the optical axis Ax direction.

[0020]

1 shows an example in which the present invention is applied as a focus detecting device for a microscope. As shown in FIG. 1, the light flux in the visible region from the epi-illumination system 12 is reflected by the half mirror 11, transmits the visible light and reflects the infrared light, the half mirror 5, and the objective lens as the objective optical system. The substrate 7 is illuminated via 6. The substrate 7 is placed on a stage 16, and the stage 16 is driven by an X-axis driving unit (not shown) provided inside.
It is provided so as to move two-dimensionally in the Y direction and move in the Z direction (vertical direction).

By illuminating the substrate 7 under visible light, the light reflected from the surface 7a of the substrate is the objective lens 6, the half mirror 5, and the dichroic mirror 1.
After forming an image through 0 and the half mirror 11, it passes through the eyepiece lens 13. Here, a spatial image I of the surface 7a of the substrate is formed at the position where the image is formed by the objective lens 6, and when observed through the eyepiece lens 13, the spatial image I of the substrate surface 7a is enlarged and observed. The objective lens 6
And the eyepiece lens 13 constitute an observation optical system.

On the other hand, the infrared light from the light source 1 for position detection is condensed by the condenser lens 2 and then illuminates the slit plate 3 having a slit-shaped opening. A slit-shaped light beam is formed on the. Half of one light beam (lower light beam) of the light beams passing through the slit plate 3 which is divided into two by the surface including the optical axis Ax of the condenser lens 2 (the surface perpendicular to the paper surface in the drawing) is the light shielding plate. Half of the other light flux (upper light flux) L ₁ is shielded by 4, and is reflected by the half mirror 5. Then, the light flux reflected by the half mirror 5 passes through the left half of the objective lens 6 (the left half of the pupil of the objective lens 5), and on the surface 7a of the substrate, strictly speaking, the object plane of the objective lens 6 (reference plane or Planned focal plane of objective lens 6)
It is focused on P ₀ .

Here, the slit plate 3 is provided with respect to the objective lens 6 at a position conjugate with the object plane (reference plane or planned focal plane of the objective lens 6) P _{0 of the} objective lens 6 and the objective lens 6. An image of the opening of the slit plate 3 is formed on the object plane of 6. Therefore, substantially slit-shaped light is projected on the substrate surface 7a as the test surface,
As a result, the light flux L ₂ reflected on the substrate surface 7a passes through the right half of the objective lens 6 (right half of the pupil of the objective lens 5) and the half mirror 5, and then is reflected by the dichroic mirror 10 to move to the position A At once to collect light. After that, the light flux from the position A is condensed by the relay optical system 20 on the light receiving surface of the photoelectric detector 8 such as a line sensor. The position A and the light receiving surface of the photoelectric detector 8 are conjugated with respect to the relay optical system 20.

The light receiving surface of the photoelectric detector 8 is provided at a position conjugate with the object plane (reference plane or planned focal plane of the objective lens 6) P ₀ with respect to the objective lens 6 and the relay optical system 20, and the optical axis. A first detection area 8a and a second detection area 8b are provided in the up-down direction with a position where a light receiving surface intersects with a surface perpendicular to the paper including Ax as a boundary. In this embodiment, between the dichroic mirror 10 and the relay optical system 20,
One side of the area that is divided into two parts with the surface including the optical axis Ax of the objective lens 6 as a boundary is shielded, and unnecessary reflected light L ₃ from the back surface 7b of the substrate that passes under the optical axis Ax as a boundary. A light shielding plate 9 to be removed is arranged.

Here, as the optimum arrangement of the light shielding plate 9 in the optical axis direction, the substrate 7 is the reference position P ₀ (the objective lens 6).
Of the reference object plane or the planned focal plane of the objective lens 6, the position A (the reflected light L ₂ that reflects the surface 7a of the substrate) conjugate with the surface of the substrate with respect to the objective lens 6 is condensed by the objective lens 6. (A position where the objective lens 6 collects the reflected light L ₃ that reflects the rear surface 7b of the substrate) and a position B that is conjugate with the front surface of the substrate with respect to the objective lens 6). ing. In other words, position A
From the position B to the position B along the optical axis of the objective lens 6,
When the distance d from the position A to the light shielding plate 9 is along the optical axis of the objective lens 6, the light shielding plate 9 is arranged so as to satisfy the relationship of the following mathematical formula.

[0026]

0 <d <L As a result, only the reflected light L ₂ from the substrate surface 7a is efficiently extracted, and the extracted light L ₂ reaches the light receiving surface of the photoelectric detector 8. Instead of the light blocking plate 9, a partial light blocking plate having a transmissive portion and a light blocking portion may be used to block light only in a necessary area.

Now, the first on the light receiving surface of the photoelectric detector 8
The two photoelectric signals obtained from both the detection area 8a and the second detection area 8b are output to the object plane detection unit (focus position detection unit) 14. The object plane detection unit 14 includes a differential signal processing circuit for obtaining a differential signal of two photoelectric signals, and if the objective lens 6 is focused on the substrate surface 7a, the differential signal becomes zero, and the differential signal becomes zero. When in focus, a certain differential signal corresponding to the defocus amount can be obtained. Therefore, the object surface detection unit 14 detects the position of the substrate surface 7a with respect to the object surface (reference surface) of the objective lens 6.

Thereafter, the focus detection information from the object plane detection unit 14 is input to the control unit 15, and based on this input information, the stage 16 is moved in the vertical direction (Z direction) by a predetermined amount for focusing. . Next, considering the optimum position of the light shield plate 9, in order to give the light shield plate 9 a function of removing the reflected light (unnecessary infrared light) L ₃ from the back surface 7b of the substrate, at the time of focusing, Light reflected from the front surface 7a of the substrate L ₂
It is understood that it is preferable to dispose between the position A where the light is condensed by the objective lens 6 and the position B where the reflected light L ₃ that reflects the back surface 7b of the substrate is condensed by the objective lens 6.

Therefore, if the arrangement conditions of the light shielding plate 9 are more specifically expressed as a mathematical expression, when the substrate surface 7a is at the reference position P ₀ (when the substrate surface 7a is in focus).
At the position A conjugate with the surface of the substrate with respect to the objective lens 6.
From the light-shielding plate 9 in the direction of the optical axis, the refractive index of the substrate 7 with respect to the wavelength of the focus detection light is n, the thickness of the substrate is t,
The substrate surface 7a is the object plane (reference position) P _{0 of the} objective lens 6.
(When the substrate surface 7a is in focus), the lateral magnification of the objective lens 6 is β ₁ , the focal length of the objective lens 6 on the test surface side (object side) is f ₁₁ , and the detection of the objective lens 6 is performed. When the focal length on the side (image side) is f ₁₂ , the above formula 1 becomes like the following formula 2.

[0030]

[Equation 2]

Therefore, it is more desirable to dispose the light shielding member 9 so as to satisfy the above-mentioned formula 2. While removing unnecessary reflected light L ₃ reflected from the back surface 7b of the substrate,
In order to make the detection ranges of the front pin and the rear pin equal, it is preferable to satisfy the following Expression 3.

[0032]

[Equation 3]

As described above, in this embodiment, the back surface 7 of the substrate is
Since the unnecessary reflected light L ₃ from b can be blocked by the light blocking plate 9, the position of the substrate surface 7a with respect to the object plane of the objective lens 6 can always be detected with high accuracy. Therefore, the substrate surface 7a can be inspected with high accuracy by the observation optical system (6, 13). Next, a second embodiment according to the present invention will be described with reference to FIG. In FIG. 2, members having the same functions as the members shown in FIG. 1 are designated by the same reference numerals.

In the above-described first embodiment, an example in which the position of the surface 7a of the substrate 7 having a constant thickness is accurately detected has been described, but in the second embodiment, the surface 7a of the substrate 7 having a different thickness is detected. An example of accurately detecting the position will be described. Now, when trying to detect the substrate front surface 7a having a different thickness, the reflected light L ₃ from the back surface 7b of the substrate by the objective lens 6 as the objective optical system is detected.
The condensing position A of moves along the optical axis Ax direction. Therefore, in order to remove the unnecessary reflected light L ₃ from the back surface 7a, it is necessary to move and adjust the light shielding plate 9 along the optical axis Ax direction as the thickness of the substrate 7 changes.

Therefore, in this embodiment, as shown in FIG.
The light shielding plate 9 is driven by the drive unit 18 along the Ax direction (arrow direction a).
It is provided so that it can be moved. Therefore, the operation of setting the position of the light shielding plate 9 in this embodiment will be described. First, a mark, for example, a bar code BC is provided at the end of the substrate surface, and the thickness t of the substrate 7 is provided at this mark. Also, information such as the refractive index n of the substrate 7 is included.
A bar code reader 17 as mark detecting means for reading the bar code BC is provided at the end of the stage 16. When the bar code reader 17 reads the bar code BC on the board 7, the bar code reader 17 outputs this information to the calculation unit 18, where a predetermined calculation is performed.

The calculation unit 18 has the calculation formulas of the above-mentioned formulas 2 or 3 stored in advance, and the bar code reader 1
The calculation is performed based on the information output from 7 and the calculation result is output to the drive unit 19. Based on the calculation result, the drive unit 19 moves the light shield 9 in the optical axis Ax direction (arrow direction a) and sets the light shield 9 at an optimum position according to the thickness of the substrate 7.

With the above configuration, the light-shielding plate 9 can be set at the optimum position even when the thickness t of the substrate as the object to be inspected changes, so that the substrate surface 7 with respect to the object plane of the objective lens 6 can be set.
The position of a can always be detected with high accuracy. Therefore, the observation optical system (6, 13) can inspect the substrate surface 7a with higher accuracy. Next, a third embodiment in which the apparatus according to the present invention is applied to a microscope will be described with reference to FIG. In FIG. 3, members having the same functions as the members shown in FIG. 1 are designated by the same reference numerals.

The third embodiment is different from the above-described first embodiment in that the objective lens 6 as an objective optical system in the focus detection optical system is composed of two objective lenses 61 and 63. The point is that a parallel system is formed between the two objective lenses 61 and 63. The present embodiment will be described in detail. A first objective lens 61 that collimates light from the substrate surface 7a (test surface) and parallel light from the first objective lens 61 is collected and tested. Second forming an aerial image I of surface 7a
An objective optical system is configured with the objective lens 62. An aerial image I of the surface to be inspected is formed by both of the objective lenses 61 and 62, and the aerial image I is passed through the eyepiece lens 13.
Is magnified and observed.

On the other hand, a dichroic mirror 10 having a function of transmitting visible light and reflecting infrared light is obliquely provided between the first objective lens 61 and the second objective lens 62, and this dichroic mirror 10 is provided. A third objective lens 63 for focus detection is provided in the reflection direction of. Here, the first objective lens 61 and the third objective lens 63 form an objective optical system for focus detection (position detection).

With respect to the infrared light from the light source 1 that has passed through the condenser lens 2, the light flux on the right side of the optical axis Ax is blocked by the light blocking plate 4 via the slit plate 3, and the light flux L on the left side of the optical axis Ax.
Only ₁ reflects off the half mirror 21. The reflected light is reflected by the lower half of the third objective lens 63 (the lower half of the pupil of the third objective lens 63), the dichroic mirror 10 and the left half of the first objective lens (the left side of the pupil of the first objective lens 63). Light is focused on the substrate surface 7a via the (half). Here, the slit plate 3 is an object plane (reference plane) P formed by the first and second objective lenses with respect to the first and third objective lenses.
An image of the opening of the slit plate 3 is substantially formed on the substrate surface 7a as a surface to be inspected, which is provided at a position conjugate with ₀ .

Therefore, substantially slit-shaped infrared light is projected onto the substrate surface 7a as the surface to be inspected, and the infrared light L ₂ reflected on the substrate surface 7a by this is the first infrared light L2. Right half of the objective lens (right half of the pupil of the first objective lens 63), dichroic mirror 10 and third objective lens 6
After passing through the upper half of 3 (the upper half of the pupil of the third objective lens 63), the light passes through the half mirror 21 and is once focused. However, when the substrate surface 7a coincides with the focal plane of the first objective lens 61, the light L _{2 that} has passed through the half mirror 21 is condensed at the position A. Then, the infrared light L ₂ which has passed through the half mirror 21 and is once focused passes through the lower half of the relay optical system 20 and is focused on the light receiving surface of the photoelectric detector 8.

The light receiving surface of the photoelectric detector 8 is provided at a position conjugate with the object plane (reference plane) P ₀ of the objective optical system (61, 63), that is, the focal plane of the objective lens 61, and photoelectric detection is performed. The device 8 photoelectrically detects the image formation state of the image of the opening of the slit plate 3. The object plane detection unit 14 detects the in-focus state based on the signal output from the photoelectric detector 8, and the control unit 15 controls the vertical position of the stage 16 based on the detection result.

Also in this embodiment, similarly to the above-mentioned embodiments, the light-shielding plate 9 for removing unnecessary infrared light reflected from the back surface 7b of the substrate is focused so as to satisfy the above mathematical expression 1. The objective lenses 61 and 63 are arranged between the position A where the reflected light L ₂ from the front surface 7a of the substrate is focused and the position B where the reflected light L ₃ from the back surface 7b of the substrate is focused. Has been done.

As described above, the back surface 7 of the substrate is also used in this embodiment.
Since the unnecessary reflected light from b can be blocked by the light blocking plate 9, the position of the substrate surface 7a with respect to the object planes of the objective lenses 61 and 63 (or the focal plane of the objective lens 61) can always be detected with high accuracy. As a result, the substrate surface 7a
Can be inspected with higher accuracy. In this embodiment as well, as in the second embodiment shown in FIG. 2, a mark such as a bar code is provided at the end of the substrate surface 7a, and the calculation of the above formula 2 or formula 3 is performed based on the detection information of this mark. The light shielding plate 9 may be moved in the direction of the optical axis based on the result of this calculation to set it at the optimum position.

Further, in each of the embodiments described above, the stage 16 is provided so as to be movable in the Z direction in order to correct the deviation of the surface to be inspected (substrate surface) from the object plane of the objective optical system (61, 63). However, as shown in FIG. 3, focusing may be performed by moving the first objective lens 61 for collimating the light from the surface to be inspected in the optical axis Ax direction. In this case, focusing can be performed by moving only the first objective lens 61 without moving the substrate as the surface to be inspected.

Finally, a fourth embodiment in which the apparatus according to the present invention is applied to a microscope will be described with reference to FIG.
4, members having the same functions as those of the members shown in FIG. 3 are designated by the same reference numerals. The difference between this embodiment and the third embodiment described above is that the objective optical system focuses the reflected light from the substrate surface 7a on the objective lens (61, 63).
And a re-imaging lens 64 for re-imaging the reflected light imaged by the objective lens (61, 63) at a predetermined position, and between the re-imaging lens 64 and the relay optical system 20. Light shield 9 for removing unnecessary infrared light reflected from the back surface 7b of the substrate
Is the point.

Here, the light-shielding plate 9 is designed so that the objective optical system (the objective lens (61, 61,
63) and the re-imaging lens 64) collects the reflected light L ₂ from the surface 7a of the substrate at the first position A ′, and the objective optical system (objective lenses (61, 63) and It is arranged between the second position B ′ where the reflected light L ₃ from the back surface 7b of the substrate is condensed by the re-imaging lens 64).

When the optimum arrangement condition of the light shielding plate 9 is expressed by a mathematical expression, the objective optical system (objective lens (objective lens (objective lens (objective lens ()) is obtained when the substrate surface 7a is at the reference position P ₀ (when the substrate surface 7a is focused). 61, 63) and the reimaging lens 64), the distance in the optical axis direction from the position A ′ conjugate with the surface of the substrate to the light shielding plate 9 is d, and the refractive index of the substrate 7 with respect to the wavelength of the light for focus detection. N, the thickness of the substrate 7 is t, the substrate surface 7a
Is on the object plane (reference position) P ₀ of the objective lens (61, 63) (when the substrate surface 7a is in focus), the lateral magnification of the objective lens (61, 63) is β ₁ , and the objective lens ( 61, 63) the focal length of the surface to be inspected (object side) is f ₁₁ , the objective lens (61, 63)
When the focal length on the detection side (image side) is f ₁₂ , and the substrate surface 7a is at the object plane (reference position) P ₀ of the objective lens (61, 63) (when the substrate surface 7a is in focus). The lateral magnification of the re-imaging lens 64 is β ₂ , the focal length of the re-imaging lens 64 on the test surface side (object side) is f ₂₁ , and the focal length of the re-imaging lens 64 on the detection side (image side) is f 2. When it is set to ₂₂ , the following Expression 4 is obtained.

[0049]

[Equation 4]

Further, in order to make the detection ranges of the front pin and the rear pin equal in this embodiment, it is desirable to satisfy the following expression 5.

[0051]

[Equation 5]

As described above, also in this embodiment, the back surface 7 of the substrate is
Since the unnecessary reflected light from b can be blocked by the light blocking plate 9, the position of the substrate surface 7a with respect to the object planes of the objective lenses 61 and 63 (or the focal plane of the objective lens 61) can always be detected with high accuracy. As a result, the substrate surface 7a
Can be inspected with higher accuracy. Also in this embodiment, as in the second embodiment shown in FIG. 2, a mark such as a bar code is provided at the end of the substrate surface 7a, and the calculation of the above formula 4 or formula 5 is performed based on the detection information of this mark. The light shielding plate 9 may be moved in the direction of the optical axis based on the result of this calculation to set it at the optimum position.

Furthermore, in each of the above-described embodiments, an example in which the present invention is applied to focus detection of a microscope is shown, but it is needless to say that the present invention is not limited to this and can be applied to focus detection or position of other devices. .

[0054]

As described above, according to the present invention, since only the reflected light from the surface of the substrate can be efficiently extracted, the position detecting device capable of detecting the position of the surface of the substrate with higher accuracy. Can be achieved. Moreover, a great effect can be expected by adding a slight improvement to the conventional device.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of a first embodiment in which the present invention is applied to a microscope.

FIG. 2 is a diagram showing a schematic configuration of a second embodiment in which the present invention is applied to a microscope.

FIG. 3 is a diagram showing a schematic configuration of a third embodiment in which the present invention is applied to a microscope.

FIG. 4 is a diagram showing a schematic configuration of a fourth embodiment in which the present invention is applied to a microscope.

FIG. 5 is a principle diagram showing the principle of the present invention.

FIG. 6 is a diagram showing how reflected light from the back surface of a substrate is detected in a conventional focus detection device.

FIG. 7 is a diagram showing a schematic configuration of a conventional focus detection device.

[Explanation of symbols for main parts]

1 ... Light source, 2 ... Condensing lens, 3 ... Slit plate,
4, 9 ... Light-shielding plate 5, 11 ... Half mirror, 6 ... Objective lens, 7 ...
Substrate, 8 ... Light source detector 10 ... Dichroic mirror, 12 ... Epi-illumination system,
13 ... Eyepiece, 14 ... Focus detection unit, 15 ... Control unit, 16 ... Stage

Claims (3)

[Claims] Claim: What is claimed is: 1. Light projected through a first region, which is bisected by a plane including an optical axis of an objective optical system, onto a surface of the substrate, and light reflected from the surface of the substrate is projected. In a position detection device that detects the position of the substrate by photoelectrically detecting with a detector through the other second region that is divided into two with a surface including the optical axis of the objective optical system as a boundary, Between the objective optical system and the detector, while arranging a relay optical system for condensing the reflected light condensed at a predetermined position by the objective optical system on the light receiving surface of the detector,
A first position conjugate with the front surface of the substrate with respect to the objective optical system when the substrate is at the reference position, and a second conjugate position with the back surface of the substrate with respect to the objective optical system when the substrate is at the reference position. A light blocking member that blocks the reflected light from the back surface of the substrate through the second region is disposed between the position and the position, and is provided on the optical axis of the objective optical system from the first position to the second position. A position detection device characterized by satisfying the following relationship: 0 <d <L, where L is a distance along the optical axis of the objective optical system from the first position to the light blocking member. . 2. The position detecting device according to claim 1, wherein the light shielding member is provided so as to be movable in the optical axis direction of the objective optical system according to the thickness of the substrate. 3. The objective optical system includes an objective lens for forming an image of reflected light from the substrate, and a re-imaging lens for re-forming an image of the reflected light imaged by the objective lens at the predetermined position. The position detecting device according to claim 1 or 2, further comprising: