JPH06265329A - Inclination detector for plane board - Google Patents

Abstract

PURPOSE:To provide an inclination detector for a plane board which has a small size, eliminates a complicated aligning and can accurately detect an inclination. CONSTITUTION:A waveguide 4 propagates a light from a light source 1 in a zero order mode and irradiates a plane board with the light. A reflected light is again incident on the waveguide 4, and propagated in one or both of zero order mode and a first order mode. Detecting means 12, 13 detect an inclination of the board corresponding to the mode excited in the waveguide 4 by detecting it from a distribution of the propagated light.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for detecting the inclination of a flat substrate such as a semiconductor wafer.

[0002]

2. Description of the Related Art A device for detecting the inclination of a flat substrate is used in various industrial equipment. For example, when used in a semiconductor exposure apparatus, it is necessary to detect the inclination of the surface of a wafer or reticle with high accuracy. The exposure apparatus uses the detection result to correct the inclination of the surface of the wafer or reticle,
The entire surface of the exposure area of the wafer is accurately set within the depth of focus of the projection lens of the exposure apparatus.

Conventionally, as a tilt detection device for a flat substrate used in an exposure apparatus, there is a non-contact detection device for detecting whether or not the flat substrate is in a vertical position with respect to the optical axis of the projection lens of the exposure apparatus. It is provided. This will be described with reference to FIG. As shown in FIG. 2, the detection device includes a light source 21, such as a light emitting diode, having a small coherence, a condenser lens 22, a pinhole 23, and a collimator lens 24.
5 are arranged in order to form an illumination optical system. Further, the coupling lens 26 and the four-divided light receiving element 27 are sequentially arranged on the optical axis 28 to form a detection optical system. The optical axis 25 is an optical axis of incident light that is incident on the wafer 20 as a flat substrate in an oblique direction. The optical axis 28 is the optical axis 2
Light 5 is the optical axis of the reflected light reflected by the wafer 20.

The light emitted from the light source 21 is condensed by the condenser lens 22 and the pinhole 23, collimated by the collimator lens 24, and obliquely irradiated onto the wafer 20.

The light flux of specularly reflected light on the wafer 20 is condensed near the center of the four-division light receiving element 27 via the imaging lens 26 to form a conjugate image 29 of the pinhole opening.
If the wafer 20 is horizontal, the light beam 25 is focused on the center of the four-division light receiving element 27, and when the wafer 20 is tilted, the light beam 28 is also tilted along with the tilt, and the conjugate image 29 is located at the four-division light receiving element. Off the center of 27. The tilt direction of the wafer 20 is detected from the position where the conjugate image 29 deviates.

[0006]

In the conventional inclination detecting device for a flat substrate described above, it is necessary to align and adjust the optical components constituting the illumination optical system and the detection optical system as shown in FIG. . Therefore, there is a problem that adjustment is time-consuming and expensive.

In view of the above-mentioned conventional problems, the present invention can detect the inclination of the flat substrate with high accuracy, requires less adjustment of the optical system, and is small in size. An object is to provide a detection device.

[0008]

In order to achieve the above object, an apparatus for detecting inclination of a flat substrate according to a first aspect of the present invention includes an illuminating unit for irradiating the flat substrate with light and the flat substrate. And a waveguide section for propagating the light illuminated from the illuminating means and the reflected light from the plane substrate, wherein the waveguide section is a main conductor. The lighting unit includes a waveguide section, a branch section for branching the main waveguide into three waveguides, and three branch waveguides connected to the branch section. It is arranged at the position where the light enters the central branch waveguide of the waveguide,
The detection means is arranged at a position for detecting light propagating in the branch waveguides on both sides of the three branch waveguides, and the central branch waveguide of the three branch waveguides is a single mode. A waveguide, the main waveguide is a double-mode waveguide, the central branch waveguide and the main waveguide propagate the illumination light emitted from the illumination means, the main waveguide The planar substrate is irradiated with the light from the end face, the main waveguide propagates the reflected light from the planar substrate, and the branching unit propagates the light propagating in the main waveguide to the three branch waveguides. It is characterized in that it is distributed to the branch waveguides on both sides.

An optical component is further arranged between the end face of the main waveguide and the flat substrate to convert the light emitted from the end face of the main waveguide into parallel light, and then irradiate the flat substrate. Can also be taken.

The main waveguide is made of a material having an electro-optical effect, and an electrode for applying a voltage to the main waveguide is arranged on the main waveguide portion, whereby the main waveguide optical The physical properties can be controlled.

Further, by using a semiconductor substrate as a waveguide substrate for producing the waveguide, a photodetector for detecting light propagating in the branch waveguides on both sides of the branch waveguide, and a central waveguide. It becomes possible to form the illuminating means for making the light incident on the waveguide monolithically on the substrate together with the waveguide portion.

Further, a conversion means for converting the polarization direction is arranged between the end face of the main waveguide and the plane substrate,
The main waveguide is formed of a material having anisotropy in refractive index, is a single-mode waveguide for linearly polarized light in the polarization direction a, and is linearly polarized in the polarization direction b (where a ≠ b). The illumination means emits linearly polarized light in the polarization direction a, and the central branch waveguide and the main waveguide are zero-mode illumination light emitted in the polarization direction a. The light propagates in the next mode and irradiates the flat substrate from the end face of the main waveguide, and the conversion means converts linearly polarized light in the polarization direction a emitted from the end face of the main waveguide into circularly polarized light, The circularly polarized light reflected by the flat substrate is converted into linearly polarized light in the polarization direction b,
Further, the main waveguide can also be configured to propagate the reflected light in the deflection direction b from the plane substrate in one or both of the 0th-order mode and the 1st-order mode.

Further, in order to achieve the above object, according to the second aspect of the present invention, an illuminating means for irradiating the plane substrate with light and a detection for detecting the reflected light from the plane substrate. Means and a waveguide portion for propagating the reflected light from the plane substrate, wherein the waveguide portion has a waveguide structure in at least two directions perpendicular to the direction of propagating the reflected light, The reflected light propagates in either or both of the 0th-order mode and the 1st-order mode in the two directions, and the detection means includes the waveguide in the reflected light from the planar substrate. There is provided an inclination detecting device for a flat substrate, which is arranged at a position for detecting light propagating through a section and detects an intensity distribution of light in the at least two directions of the waveguide section.

[0014]

In the present invention, the waveguide substrate in which the double mode waveguide is formed is used for detecting the inclination of the substrate as described above.

First, the characteristics of the double mode waveguide will be described.

When the incident light entering the double mode waveguide has asymmetry of intensity or phase with respect to the direction having the waveguide structure of the double mode waveguide (width direction of the waveguide), double A 0th-order mode and a 1st-order mode are excited in the mode waveguide. These two modes cause mode interference in the double-mode waveguide, and light whose energy oscillates in the lateral direction is excited in the double-mode waveguide. The half cycle of this vibration is called a complete coupling length (hereinafter referred to as Lc) and is determined by the shape of the waveguide, the refractive index distribution, and the wavelength of the guided light.

Then, except when the length L of the double mode waveguide is L = Lc.multidot. (2n + 1/2) (n = 0, 1, 2, ...) (1), the intensity of the incident light spot is The splitting ratio of the light in the splitting means changes according to the degree of asymmetry.
The amount of this change becomes maximum when the length of the double mode waveguide is an integral multiple of Lc.

On the other hand, when an incident light spot having a symmetrical intensity distribution is incident on the incident end face of the above-mentioned double-mode waveguide with respect to the direction having the waveguide structure, the zero-order light is introduced in the double-mode waveguide. Since only the modes are excited, the oscillation of light energy as described above does not occur. Therefore, the light propagating in the double mode waveguide is equally distributed by the branching means.

Further, the asymmetry of the intensity distribution of the incident light spot is relative to the incident surface of the double mode waveguide, and even if the shape of the incident light spot itself is symmetrical, the double mode waveguide is If the center of the light spot is laterally displaced with respect to the center of the incident surface in the width direction, the splitting ratio of the light by the splitting means changes as in the case where the intensity distribution is asymmetric in the incident light spot. .

Therefore, the amount of deviation of the incident light spot incident on the double mode waveguide whose length is an integral multiple of Lc from the center of the incident surface of the double mode waveguide independently detects the amount of emitted light after branching. This can be known as a change in the branching ratio. The sign of the difference signal between the outputs from the two photodetectors that detect the branched light is reversed depending on the direction of deviation of the incident light spot from the center of the double-mode waveguide entrance surface. You can know the direction.

In the tilt detecting device for a flat substrate according to the present invention utilizing the characteristics of the double mode waveguide described above, the light emitted from the main waveguide, which is a double mode waveguide, is irradiated onto the flat substrate and reflected. Is incident on the waveguide entrance end face again.

When the flat substrate is placed at a position perpendicular to the parallel light flux, the reflected light from the substrate returns along the same optical path as the irradiation light, and the light spot is focused at the same place as the emitted light. Tie Therefore, as described above, an incident light spot having a symmetric intensity distribution is incident on the main waveguide with respect to the width direction of the incident end surface of the main waveguide, and only the 0th-order mode is excited in the main waveguide. Therefore, the vibration of light energy as described above does not occur. Therefore, the light propagating in the main waveguide is equally distributed at the branching portion. The signals of the two photodetectors are equal and the difference between them is zero.

On the other hand, when the plane substrate is tilted with respect to the parallel luminous flux, the reflected light from the substrate does not pass through the same optical path as the irradiation light, and the light spot is focused at a position displaced from the center of the waveguide. In this case, since the center of the light spot is laterally displaced from the center of the incident surface of the main waveguide in the direction having the waveguide structure, the difference signal between the signals of the two photodetectors is not 0 as described above. The inclination of the flat substrate can be detected. The sign of the difference signal also tells the direction of the tilt of the planar substrate.

Further, in the present invention, since the waveguide from which the illumination light is emitted is used for detection, the labor of adjustment can be reduced.

Further, when a collimator lens for collimating light emitted from the end face of the main waveguide into parallel light flux and irradiating the collimated light is arranged between the emission end face of the main waveguide of the waveguide section and the plane substrate. Since the reflected light from the flat substrate is condensed on the end face of the main waveguide, the inclination of the flat substrate can be detected more accurately.

As described above, in an apparatus for detecting an inclination using a double mode waveguide due to the deviation of the reflected light from the flat substrate, it is necessary to irradiate the flat substrate with a center-symmetrical light spot having no deviation. . In the configuration of the first aspect of the present invention, the three branch waveguides are arranged in such a positional relationship that the center line of the central branch waveguide and the center line of the main waveguide are coincident with each other. Light that enters the main waveguide from the central branch waveguide of the branch waveguides is configured to excite only even modes in the main waveguide. Therefore, the light with which the flat substrate is irradiated is light that has propagated through the main waveguide in the 0th-order mode, and is light that is centrosymmetric and has no deviation.

In the case of this structure, when the waveguide is manufactured, the center lines of the central branch waveguide and the main waveguide are misaligned, the branch portions are asymmetric rather than center symmetrical, and the main waveguide If the refractive index distribution is deviated, there is a possibility that not only the 0th-order mode but also the 1st-order mode is excited in the main waveguide. Therefore, in the present invention, the possibility that the primary mode is excited can be eliminated by adopting the following configuration.

First, the light for illuminating the flat substrate and the reflected light from the flat substrate are converted into linearly polarized light having different polarization directions and propagated through the main waveguide. Further, the main waveguide is formed of a material having anisotropy in refractive index, and by forming the waveguide in an orientation in which the refractive index for polarized light of reflected light is larger than the refractive index for polarized light of illumination light,
It propagates each light as a single mode waveguide for the illumination light and as a double mode waveguide for the reflected light from the flat substrate.

Therefore, since the main waveguide is always a single mode waveguide for the illumination light, there is no fear of exciting the first-order mode, and the illumination light is always propagated only in the zero-order mode, and the amount of light is increased. And the spot light having a normal distribution of phase is emitted to the flat substrate. Therefore, the connection relationship between the central branch waveguide and the main waveguide is sufficient if the propagating light can be efficiently transferred, and it is not necessary to manufacture it with strict accuracy, and it can be easily formed by a known method. can do.

On the other hand, the main waveguide is always a double mode waveguide for the reflected light from the flat substrate, and as described above, the inclination of the flat substrate can be detected from the deviation of the reflected light. .

As described above, according to the present invention, the polarization directions of the illumination light and the reflected light are set to different directions, and the main waveguide is formed of a material whose refractive index is anisotropic in the polarization direction. Single mode for illumination light,
Double mode is used for reflected light. As a result, it is possible to realize the inclination detector of the flat substrate which is a waveguide which can be easily manufactured and which has a waveguide which can propagate only the illumination light in the 0th mode.

When the main waveguide portion is made of a material having an electro-optic effect, a voltage is applied to the main waveguide via an electrode arranged on the main waveguide, whereby the complete coupling length Lc Can be changed. Therefore, even if the length of the double mode region is a constant value L, L can be an integral multiple of Lc by the electro-optical effect while keeping the mechanical length of the double mode region constant by adjusting the voltage.

Further, in the inclination detecting device for a flat substrate according to the second aspect of the present invention, by using the waveguide portion having the double mode waveguide structure in at least two directions, the directions having this waveguide structure are respectively The tilt can be detected. Thereby, the inclination direction of the flat substrate can be detected two-dimensionally.

[0034]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a flat substrate inclination detecting apparatus according to a first embodiment of the present invention.

The flat substrate inclination detecting apparatus of the first embodiment is a laser light source 1 for irradiating the flat substrate 7 with light as shown in FIG. 1, and a photodetector for detecting the reflected light from the flat substrate 7. 12 and 13 are provided. Further, a waveguide substrate 2 having a waveguide for propagating the illumination light emitted from the laser light source 1 and the reflected light from the flat substrate 7 is arranged.

On the waveguide substrate 2, the main channel waveguide 4 is provided.
And a branch portion 8 for branching the main channel waveguide 4 into three waveguides, and three branch channel waveguides 3, 9, 10 connected to the branch portion 8.

The laser light source 1 is arranged on the end face of the central branch channel waveguide 3 so as to maximize the light coupling efficiency. The central branch channel waveguide 3 is formed to be a single mode waveguide, and the main channel waveguide 4 is formed to be a double mode waveguide. Since the center line of the center branch channel waveguide 3 and the center line of the main trunk channel waveguide 4 are arranged to coincide with each other, the light incident from the center branch channel waveguide 3 to the main trunk channel waveguide 4 is 0. Only the next mode is excited. The light emitted from the laser light source 1 propagates through the branch channel waveguide 3 and the main trunk channel waveguide 4 in the center, and is irradiated onto the plane substrate 7 from the end surface 5 of the main trunk channel waveguide.

A collimator lens 6 is arranged between the waveguide substrate 2 and the plane substrate 7, and the plane substrate 7 is irradiated with a parallel light flux. This optical system also serves as an optical system that focuses the reflected light from the flat substrate 7 on the end surface 5 of the main channel waveguide.

The reflected light from the plane substrate 7 enters from the end face 5 of the main channel waveguide, is guided through the main channel waveguide 4, and is then branched to be on both sides of the three branch channel waveguides. It propagates through the branch channel waveguides 9 and 10. The photodetectors 12 and 13 are arranged on the end faces of the branch channel waveguides 9 and 10 on both sides and detect the intensity of the propagated light.

The photodetectors 12 and 13 are connected to a differential detecting means 14 for obtaining a difference in light quantity. When the output signal 15 of the differential detector 14 is 0, the plane substrate 7 is perpendicular to the optical axis, and when the differential signal 15 is not 0, the plane substrate 7 is inclined, and the inclination directions are different. It can be seen from the sign of the motion signal 15.

Next, the method for detecting the inclination of the flat substrate in the present invention will be specifically described with reference to FIGS. FIG. 3 is an enlarged view of part of FIG. 1 described above. Figure 3
In, the light reflected by the flat substrate 7 enters the entrance end 5 of the main channel waveguide on the waveguide substrate 2.

At this time, if the center of the reflected light from the flat substrate 7 is not located exactly in the center of the width of the main channel waveguide 4, the intensity distribution of the incident light is asymmetric with respect to the central axis of the main channel waveguide 4 (see FIG. 3 shows the medium intensity distributions 40 and 41), and the 0th and 1st order modes of light are excited in the main channel waveguide 4 and the optical power oscillates in the width direction of the main channel waveguide due to the interference of both modes (Fig. 3). Middle, route 43,
44). At this time, since the length of the main channel waveguide 4 is almost an integral multiple of the complete coupling length Lc of the 0th and 1st modes, the reflected light from the flat substrate 4 and the double mode waveguide 4 are branched at the branching portion 8. Light is distributed according to the amount of deviation between the width centers. Therefore, the light after branching is guided 3
Channel waveguides 9 on both sides of the book branch channel waveguide,
Signals of different intensities are obtained from the photodetectors 12 and 13 provided at the output end of 10.

FIG. 5 is an enlarged view of the waveguide exit end, the collimator lens and the plane substrate of FIG. 1 described above. In FIG. 5, the light emitted from the main channel waveguide 4 is collimated by the collimator lens 6, is reflected by the plane substrate 7, and the reflected light passes through the collimator lens 6 again.
It is condensed and enters the exit end 5 of the main channel waveguide. FIG. 5A shows the case where the plane substrate 7 is arranged at a position perpendicular to the parallel light flux, and the reflected light from the plane substrate 7 returns through the same optical path as the irradiation light, and the end face of the main channel waveguide 5, a light spot is formed at the same place 50. In this case, the center of the light spot of the reflected light coincides with the center of the emitted light spot, which coincides with the center of the main channel waveguide 4. FIG. 5B shows a case where the plane substrate 7 is tilted from a position perpendicular to the parallel light flux, and the reflected light on the plane substrate 7 does not pass through the same optical path as the irradiation light, and the main channel waveguide end face 5
A light spot is formed at a position 52 which is deviated from the light spot 51 of the emitted light. In this case, the center of the light spot of the reflected light is displaced from the center of the main channel waveguide 4.

The difference between the signal intensities of the two detectors 12 and 13 when the plane substrate 7 is tilted is such that the tilt of the plane substrate 7 which is not perpendicular to the parallel light beam is displaced by a displacement means (not shown). Becomes closer to the vertical direction with respect to the parallel light flux, the center of the light spot of the reflected light at the incident end 5 of the main channel waveguide becomes smaller as it approaches the center of the width of the main channel waveguide 7. And the flat substrate 7
Is perpendicular to the parallel light flux, and the center of the light spot at the waveguide entrance end of the reflected light is located exactly at the center of the main channel waveguide (indicated by intensity distribution 42 in FIG. 3), the main channel waveguide Since only the 0th-order mode light is excited in 4, the incident light is equally distributed to the branch channel waveguides 9 and 10 on both sides of the three branch channel waveguides as shown by a path 45 in FIG. The difference between the signal intensities of the detectors 12 and 13 is zero.

Further, when the center of the reflected light on the plane substrate 7 moves away from the center of the width of the main channel waveguide 4 to the opposite side from the approaching direction, the distribution of the incident light intensity becomes asymmetric again and the photodetector 12 , 13 output signals are not 0, and the positive and negative signs are opposite when approaching.

The relationship between the difference signal between the outputs of the photodetectors 12 and 13 and the deviation amount between the center of the reflected light from the plane substrate 7 and the center of the width of the main channel waveguide 4 is schematically shown in FIG. Like In the figure, the vertical axis represents the difference signal intensity of the outputs of the photodetectors 12 and 13, and the horizontal axis represents the deviation amount between the center of the reflected light on the plane substrate 7 and the center of the main channel waveguide 4. , The intersection of both axes indicates the position where the deviation amount is zero.

As shown in FIG. 4, the photodetector 12,
From the difference signal intensity and sign of 13, it is possible to know the magnitude and direction of the lateral deviation between the center of the reflected light on the plane substrate 7 and the center of the width of the main channel waveguide 4, so that the inclination of the plane substrate 7 The direction and tilt angle are known.

At this time, the length L of the main channel waveguide 4 may be set to L = mLc (m = 1, 2, ...) (2) with the complete coupling length being Lc.

Since lithium niobate has an electro-optical effect, the complete bond length Lc can be changed by changing the voltage applied to the electrode 11 by a power source (not shown) connected to the electrode 11. You can

Next, the waveguide substrate 2, the waveguides 3, 4,
A method of forming 9, 10 and the branched portion 8 will be described.
First, the X-cut lithium niobate substrate 2 serving as a clad
A 300 Å Ti film is formed on the top by EB deposition. This Ti film is patterned into the shapes of the branch portion 8 and the waveguides 3, 4, 9, and 10 by a lithography method. The propagation direction of the waveguide is Z propagation. The patterned Ti film and the lithium niobate substrate 2 are
A heat treatment is performed at 0 ° C. for 6 hours to diffuse Ti on the lithium niobate substrate to form a core portion. In this embodiment, the width of the main channel waveguide portion 4 is 8 μm, and the widths of the other channel waveguides are 4 μm. Finally, the entrance end and the exit end are polished to complete. At this time, the length of the main channel waveguide 4 is polished so as to satisfy the formula (2). However, as described above, in the present embodiment, by changing the voltage applied to the electrode 11, the complete coupling length Lc is changed and the length L of the main channel waveguide 4 is adjusted so as to satisfy the expression (2). can do. Therefore, the length L of the main channel waveguide during polishing may be within a range that can be adjusted so as to satisfy the formula (2) by applying a voltage to the electrode 11. As described above, the present tilt detection device for a flat substrate is capable of measuring the tilt of the flat substrate by using the waveguide and having a configuration that is small and simple and requires less adjustment.

Another example of the material suitable for forming the channel waveguide in the structure of the first embodiment will be described.

As a clad substrate for the waveguide, for example, S
i, soda glass, Pyrex, fused silica, etc. can be used. These have no electro-optic effect,
It can be used in this embodiment by precisely adjusting the length of the waveguide so as to satisfy the conditional expression (2) necessary for detection. Further, as a material having an electro-optical effect, L
iTaO3, GaAs, InP, etc. can also be used. By forming electrodes based on these electro-optical effects, it is possible to change the complete coupling length L of the main channel waveguide 4. When Si is used for the substrate, it is possible to integrate the light receiving element,
When aAs and InP are used, both the light source and the light receiving element can be integrated. Small size of equipment, weighing,
Labor savings in coordination can be further promoted. However, if it is difficult to integrally form the photodetector with the waveguide, these may be arranged separately and the light may be guided by an optical fiber or a lens system. Further, the main channel waveguide can be replaced with two single mode channel waveguides arranged close to each other.

FIG. 6 shows a flat substrate inclination detecting device according to a second embodiment of the present invention.

The apparatus for detecting the inclination of the flat substrate of the second embodiment has a laser light source 60 for irradiating the flat substrate 67 with light and a photodetector for detecting the reflected light from the flat substrate 67 as shown in FIG. 72 and 73 are provided. In addition, a waveguide substrate 61 is provided on which a waveguide for propagating the illumination light emitted from the laser light source 60 and the reflected light from the flat substrate 67 is formed.

On the waveguide substrate 61, a main channel waveguide 63, a branch 68 for branching the main channel waveguide 63 into three channel waveguides, and three branch channel waveguides connected to the branch 68. 62, 69 and 70 are formed.

The laser light source 60 is a semiconductor laser that emits linearly polarized light in the polarization direction a (polarization in the depth direction of the waveguide), and is arranged on the end face of the central branch channel waveguide 62. The central branch channel waveguide 62 is used for the laser light source 60.
It is formed so as to be a single mode waveguide for linearly polarized light of the polarization direction a emitted from the. The light emitted from the laser light source 60 is transmitted through the branch channel waveguide 6 at the center.
2 and the main channel waveguide 63 are propagated, and the flat substrate 67 is irradiated from the end surface 64 of the main channel waveguide.

A quarter-wave plate 65 and a collimator lens 66 are arranged in this order between the waveguide substrate 61 and the plane substrate 67 to convert the linearly polarized light of the illumination light into circularly polarized light. Irradiate a parallel light beam on the. These optics
An optical system that converts the circularly polarized reflected light from the flat substrate 67 into linearly polarized light having a polarization direction b (polarization direction in the width direction of the waveguide) orthogonal to the illumination light and condenses it on the end face 64 of the main channel waveguide. Also serves as.

The reflected light from the plane substrate 67 enters from the end face 64 of the main channel waveguide, is guided through the main channel waveguide 63, and is then branched to be on both sides of the three branch channel waveguides. It propagates through the branch channel waveguides 69 and 70.
The photodetectors 72 and 73 are branch channel waveguides 69 and 7 on both sides.
The intensity of the propagated light arranged on the end face of 0 is detected.
The main channel waveguide 63 is formed of a material having anisotropy in refractive index. As described above, the single-mode channel waveguide is linear polarization in the polarization direction a (polarization in the depth direction of the waveguide), but is linear polarization in the polarization direction b (polarization in the width direction of the waveguide). A double-mode channel waveguide is formed for the reflected light.

The photodetectors 72 and 73 are connected to a differential detecting means 74 for obtaining a difference in light quantity. Similar to the first embodiment, when the output signal of the differential detector 74 is 0, the plane substrate is perpendicular to the optical axis, and when the differential signal 75 is not 0, the plane substrate is inclined, and the inclination is The direction of is known from the sign of the differential signal 75.

Next, the structure of each of the waveguides 62, 63, 69 and 70 formed on the waveguide substrate 61 will be described in detail with reference to FIG. In the second embodiment, a semiconductor laser is used as the laser light source 60. Further, as the waveguide substrate 61, an x-cut y-propagation lithium niobate single crystal was used.
As shown in FIG. 7, in the main channel waveguide 63, the Ti-diffused lithium niobate region 82 is centered and the Ti-diffused and proton-exchanged lithium niobate regions 81 a and 81 are provided.
b, and proton exchange lithium niobate regions 80a, 80
and b. The branch channel waveguide 62 is composed of Ti-diffused lithium niobate. The branch channel waveguides 69 and 70 are composed of proton-exchanged lithium niobate.

Among the methods for forming an optical waveguide in a lithium niobate single crystal, the Ti diffusion method, the proton exchange method and the Li outward diffusion method are widely used methods.

When Ti is diffused in a lithium niobate single crystal, the refractive index of both ordinary rays and extraordinary rays increases. In the case of the second embodiment, since the crystal orientation is x-cut y-propagation, linearly polarized light having a polarization direction in the width direction (z direction) of the waveguide becomes an extraordinary ray, and the direction of depth of the waveguide ( Linearly polarized light having a polarization direction of (x direction) becomes an ordinary ray. On the other hand, when this lithium niobate single crystal is proton-exchanged, the refractive index for extraordinary rays increases more than that of Ti diffusion, but the refractive index for ordinary rays decreases to the contrary. Further, the proton-exchanged lithium niobate has a reduced refractive index due to the heat treatment after the proton exchange.

Branch channel waveguide 62 made by Ti diffusion
Is a linear waveguide that is single mode for both extraordinary and ordinary rays. In the proton exchange lithium niobate regions 80a and 80b of the main channel waveguide 63, only the refractive index with respect to the extraordinary ray (polarized light in the width direction of the waveguide) increases, so the main channel waveguide 63 causes the extraordinary ray to the region 80a Double mode channel waveguide propagating by 80b, 81a, 81b and 82. On the other hand, regarding the ordinary ray (the polarization direction in the depth direction), the regions 81a and 81a
Only b and 82 propagate and become a single mode channel waveguide.

As described above, the main channel waveguide 63 is a double-mode channel waveguide for polarized light in the width direction of the waveguide (extraordinary ray), but for polarized light in the depth direction of the waveguide (ordinary ray), It is a single mode channel waveguide. In the second embodiment, the polarization direction a of the laser light source 60
However, the laser light source 60 is arranged so as to coincide with the depth direction of the waveguide of the main channel waveguide 63. Further, the quarter-wave plate 65 is arranged in a direction in which the polarization direction of the reflected light from the flat substrate 67 matches the width direction of the main channel waveguide 63. As a result, the main channel waveguide 6
3 always propagates the illumination light emitted from the laser light source 60 in the zero-order mode and emits it from the end face 64. Since the light quantity and the phase of the light propagated in the 0th-order mode are constant, the reflected light from the flat substrate 67 has a light spot of a position deviated from the center line of the main channel waveguide 63 when the flat substrate 67 is tilted. The center comes.

Then, as described above, when the plane substrate 67 is tilted, the ratio of the optical power reaching the two photodetectors 72 and 73 changes. Therefore, the inclination of the plane substrate 67 can be detected by obtaining the difference signal 75 of the outputs of the two detectors 72 and 73 by the differential detection means 74.

At this time, the length L of the double-mode waveguide 63 with respect to the extraordinary light may be set to L = mLc (m = 1, 2, ...) With the perfect coupling length being Lc.

Since lithium niobate has an electro-optical effect, the complete bond length Lc can be changed by changing the voltage applied to the electrode 71 by a power source (not shown) connected to the electrode 71. You can

Next, the waveguides 62,
A manufacturing method for manufacturing 63, 69 and 70 will be described. First, on the lithium niobate substrate 61, a region of the branch channel waveguide 62 and a region 8 of the main channel waveguide 63 are formed.
Ti was diffused into 1a, 81b and 82 by a thermal diffusion method.
In the thermal diffusion method, Ti is deposited on the above-mentioned region on the waveguide substrate 61, and this is heated in a high-temperature furnace for a certain period of time to diffuse the deposited Ti into the substrate 61 to diffuse Ti-diffused lithium niobate. Make a single crystal.

Next, the regions of the branch channel waveguides 69 and 70 on both sides of the lithium niobate substrate 61 and the regions 80a and 80b of the main channel waveguide 63 are subjected to the proton exchange method. First, a portion other than the above region is masked, the waveguide substrate 61 is dipped in a solution, and the ions in the waveguide substrate 61 are exchanged with the ions in the solution to form a high refractive index layer near the surface of the waveguide substrate 61. Create. Benzoic acid, silver nitrate, pyrophosphoric acid and the like are used as the solution. After that, the mask is removed, and annealing is performed under previously determined conditions to change the refractive index and the refractive index distribution of the proton-exchanged region to a desired size, thereby completing the process.

As described above, in the second embodiment, the main channel waveguide 63 is formed of a material having an anisotropic refractive index so that the main channel waveguide 63 reflects the illumination light in a single mode and reflects. Double mode is used for light. As a result, the illumination light always propagates in the main channel waveguide 63 only in the 0th order mode. Conventionally, since the first-order mode is not excited, it has been necessary to mechanically and highly accurately manufacture the connecting portion between the central branch channel waveguide 62 and the main channel waveguide 63.
In the embodiment, since both are single modes, there is no fear of excitation of the primary mode, and it is sufficient that the light amount is efficiently delivered. As a result, the branch portion 68 on the substrate 61 can be easily manufactured, so that the manufacturing cost can be reduced, the waveguide 68 can propagate the illumination light only in the 0th mode, and the cost is low. A substrate tilt detection device is realized.

FIG. 8 shows the second embodiment of the present invention.
7 shows another example of the configuration of a waveguide that can be used in the inclination detecting device for a flat substrate according to the embodiment. The waveguide shown in FIG. 8 is a main channel waveguide 63 that is a double mode for extraordinary rays.
Is a region 91 where both Ti diffusion waveguide and proton exchange are performed and regions 90a and 90b where only proton exchange is performed.
Are formed from. Branch channel waveguides 62, 69, 7
Since the shape of 0 and the manufacturing method are the same as those in the second embodiment, description thereof will be omitted. Since only the refractive index for extraordinary rays (polarized light in the width direction of the waveguide) increases in the proton exchange region, the extraordinary ray is a double mode channel waveguide in which the extraordinary rays propagate in the regions 90a, 90b and 91, and the ordinary ray is the region. 91
It is a single-mode channel waveguide that propagates only by itself.

Here, the propagation of light in the waveguide of FIG. 8 will be described. The light emitted from the laser light source propagates through the central branch channel waveguide 62. As described above, the light propagating through the branch channel waveguide 62 is an ordinary ray. The light that has passed through the branch portion 68 is converted into the region 9 of the main channel waveguide 63.
Propagate 1. Since the region 91 has a single mode with respect to the guided light of the ordinary ray, the propagated guided light is only the 0th mode. The polarized light of the light reflected by the plane substrate and returned to the waveguide becomes the polarized light orthogonal to the polarization direction of the light emitted from the waveguide, and the light incident on the waveguide substrate 61 is the region of the main channel waveguide 63. The regions 90a, 90b, and 91 propagate in the 0th and / or 1st order modes. The main channel waveguide 63 is a double mode for the guided light of the extraordinary ray. The light that has passed through the branch portion 68 propagates through the branch channel waveguides 69 and 70 and reaches the photodetector connected to the waveguide substrate 61.

FIG. 9 is a schematic configuration diagram showing a flat substrate inclination detecting device according to a fourth embodiment of the present invention. In this configuration, the polarizer 102 using the metal cladding is arranged on the single mode channel waveguides 101 and 103, and the light source 10
The light returning to 0 is prevented. The polarizer 102 using the metal cladding absorbs the guided light of the TM mode and
It is a known device that transmits guided light of modes.

The laser light source 100 is a semiconductor laser light source and has a lithium niobate substrate 99 having an electro-optical effect.
The optical coupling efficiency is maximized with respect to the single mode channel waveguide 101 formed above, and the guided light is fixed to the lithium niobate substrate 99 so that it is only ordinary rays. Since the polarizer 102 using the metal cladding is used in this configuration, the crystal orientation of the lithium niobate substrate 99 is z-cut, and the guided light of ordinary rays is in TE mode. The guided light guided through the single mode channel waveguide 101 is a polarizer 102 using a metal cladding.
Incident on, but is transmitted because it is in TE mode. The light incident on the single mode channel waveguide 103 receives the light from the branching unit 1
09, and propagates through the main channel waveguide 104 in which the electrode 112 is arranged on the substrate surface. A power source (not shown) is connected to the electrode 112.

In the branching portion 109 of the waveguide, three channel waveguides 10 are provided for the main channel waveguide 104.
3, 110 and 111 are coupled, and the above-described central branch channel waveguide 103 is used for illumination, and the branch channel waveguides 110 and 111 on both sides are used for detection.

The illumination light flux emitted from the end surface 105 of the main channel waveguide 104 is linearly polarized light, and the polarized light is converted into circularly polarized light by passing through the quarter-wave plate 106, and is incident on the collimator lens 107 to be planar. The parallel light flux is irradiated onto the substrate 108. The light beam reflected by the plane substrate 108 and then passed through the collimator lens 107 again passes through the quarter-wave plate 106, whereby the polarized light changes from circularly polarized light to linearly polarized light having a polarization direction orthogonal to the polarization direction at the time of waveguide exit. And is condensed on the end face 105 of the main channel waveguide 104 formed on the lithium niobate substrate 99, where a light spot is formed. After this, as in the case of the first embodiment, if the planar substrate is inclined, the branch channel waveguides 110 and 111 on both sides of the three branch channel waveguides are provided.
The power ratio distributed to the optical waveguide is changed, and the photodetectors 113 and 114 fixed to the waveguide substrate detect the light from the branch channel waveguides 110 and 111 on both sides. Is obtained. The light reflected by the plane substrate 108 is also guided to the central branch channel waveguide 103 of the three branch channel waveguides, but since it is in the TM mode, it is all when passing through the polarizer 102 using the metal cladding. The absorbed light is not propagated to the central branch channel waveguide 101, and the returned light does not affect the laser light source.

For the main channel waveguide 104 which is a double mode for extraordinary rays and a single mode for ordinary rays, which of the configurations shown in FIG. 7 and FIG. 8 should be used. You can also

FIG. 10 is a schematic block diagram showing a flat substrate inclination detecting apparatus according to a fifth embodiment of the present invention. In this configuration, in order to prevent the returning light to the laser light source 120, a mode splitter for separating different polarized lights (TE mode and TM mode) from each other is used. The mode splitter is composed of a double mode channel waveguide 125 and a branch section 137. The electrode 124 is a mode splitter electrode for finely adjusting the mode split ratio of the mode splitter. The mode splitter guides the guided light of the ordinary ray entering from the single mode channel waveguide 122 to the single mode channel waveguide 126 and guides the guided light of the extraordinary ray entering the mode splitter from the single mode channel 126 to the single mode channel guide. It is a known device for guiding light to the waveguide 123.

Although the mode splitter electrode 124 may be omitted, by adjusting the voltage applied to the mode splitter electrode, the incompleteness of the TE / TM mode split caused by the variation in the waveguide manufacturing process can be eliminated. Since it can be removed, it is preferably installed.

The laser light source 120 is a semiconductor laser light source and has the highest optical coupling efficiency with respect to the single mode channel waveguide 122 formed on the lithium niobate substrate 128 having an electro-optical effect, and the guided light is an ordinary ray. It is fixed to the lithium niobate substrate 128 so that it becomes only. The laser light that has entered the single mode channel waveguide 122 is an ordinary ray and enters the mode splitter that has the double mode channel waveguide 125. The guided light of the ordinary ray that has entered the single mode channel waveguide 126 from the mode splitter propagates through the branch portion 133 to the main channel waveguide 127 in which the electrode 136 is arranged on the substrate surface. A power source (not shown) is connected to the electrode 136.

In the branch portion 133 of the waveguide, three channel waveguides 13 are provided for the main channel waveguide 127.
4, 126 and 135 are combined, and the above-mentioned central branch channel waveguide 126 is used for illumination, and both side branch channel waveguides 134 and 135 are used for detection.

The illumination light flux emitted from the end face 129 of the main channel waveguide is linearly polarized light, and the quarter-wave plate 130 is used.
The polarized light is converted into circularly polarized light by passing through, and enters the collimator lens 131, and the plane substrate 132 is irradiated with the parallel light flux. After being reflected by the plane substrate 132, the light flux that has passed through the collimator lens 131 again passes through the quarter-wave plate 130, so that the polarized light changes from circularly polarized light to linearly polarized light having a polarization direction orthogonal to the polarization direction at the time of waveguide exit. And is condensed on the end face 129 of the main channel waveguide formed on the lithium niobate substrate 128. A light spot is formed here. After this, it is the same as the first embodiment,
When the flat substrate 132 is inclined, the power ratio distributed to the channel waveguides 134 and 135 on both sides changes, and the photodetectors 138 and 139 fixed to the waveguide substrate 128 change the power ratio.
When the light from the branch channel waveguides 134 and 135 is detected and the differential signal detecting means 140 takes the differential signal 141, a tilt signal is obtained. The light reflected by the plane substrate 132 is guided also to the central branch channel waveguide 126 of the three channel waveguides, but when it enters the mode splitter, it is converted into an extraordinary ray of guided light. Therefore, all of this light is guided to the single mode channel waveguide 123 by the mode splitter and reaches the photodetector 121. At this time, since the light does not proceed to the single mode channel waveguide 122, the return light does not affect the laser light source 120.

Main channel waveguide 1 which is a double mode for extraordinary rays and a single mode for ordinary rays
27 can use either the configuration shown in FIG. 7 or the configuration shown in FIG.

FIG. 11 is a schematic block diagram showing a flat substrate inclination detecting device according to a sixth embodiment of the present invention. This structure has two detecting means. What constitutes the first detection means is the waveguide device formed on the first waveguide substrate 151, and what constitutes the second detection means is the second waveguide substrate 1
75 is a waveguide device. Both the waveguide device formed on the first waveguide substrate 151 and the waveguide device formed on the second waveguide substrate 175 have the same configuration as the waveguide device used in the first embodiment. However, the first waveguide substrate 151 is different from the second main waveguide substrate 175 in each of the main channel waveguides 15.
The width directions (directions having the waveguide structure) of 3, 166 are configured to be orthogonal to each other.

The light emitted from the emission end 154 of the main channel waveguide 153 of the first waveguide substrate 151 is emitted by the half mirror 1.
After passing through 55, the plane substrate 157 is irradiated with the parallel light flux through the collimator lens 156. The light reflected by the plane substrate 157 passes through the collimator lens 156 and partly passes through the half mirror 155 to form a light spot on the end face 154 of the main channel waveguide of the first waveguide substrate 151. The remaining part of the light reflected by the plane substrate 157 and passed through the collimator lens 156 is reflected by the half mirror 155,
The optical waveguide substrate 175 is configured to form an optical spot on the end face 167 of the main channel waveguide 166.

When the plane substrate 157 is arranged perpendicularly to the emitted parallel light flux, the first waveguide substrate 1
The center of the light spot formed on the end face 154 of the main channel waveguide 153 of 51 and the center of the main channel waveguide 153 coincide. At this time, the second waveguide substrate 175 is arranged so that the center of the light spot formed on the end face 167 of the main channel waveguide 166 and the center of the main channel waveguide 166 coincide with each other.

In the first detecting means, the first detecting means of the flat substrate 157 is used.
Although the inclination of the main channel waveguide 153 of the waveguide substrate 151 in the width direction is detected, the inclination of the main channel waveguide 153 of the first waveguide substrate 151 of the plane substrate 157 in the depth direction cannot be detected. Therefore, by arranging the second detecting means as described above, the flat substrate 1 can be processed by the second detecting means.
57 main channel waveguide 1 of the first waveguide substrate 151
The inclination of 53 in the depth direction can be detected.

Waveguide device of first detecting means and second
The waveguide device of the detecting means is the second embodiment, the third embodiment,
Although it may be the one used in the fourth and fifth embodiments, in that case, it is necessary to dispose a quarter-wave plate between the half mirror 155 and the collimator lens 156. Although the laser light sources 150 and 164 are provided on both of the two waveguide substrates, the other laser light source is not always necessary because the illumination light may be supplied from only one of them. When the laser light sources are provided on both of the waveguide substrates, the laser light is supplied from only one of them, and if one of the laser light sources fails, the other light source is replaced. It becomes possible to continue the inclination detection of the flat substrate without any trouble.

In each of the above-mentioned embodiments, the waveguide is made of lithium niobate diffused with Ti, but the refractive index can be increased even when a transition metal other than Ti is diffused. In the case of a lithium niobate substrate, a transition metal such as Ti, V, Ni or Cu is used as the metal to be diffused.

A single crystal substrate having an electro-optical effect, such as lithium tantalate, can be used as the waveguide substrate for producing the waveguide. In the lithium tantalate substrate, diffusion of transition metals such as Cu, Ti and Nb is used to increase the refractive index.

As a method of forming the high refractive index layer on the waveguide substrate, the Li2O outward diffusion method can be used. The Li2O outward diffusion method is a method of forming a high refractive index layer by heating a substrate to a high temperature to release Li2O from the crystal surface to the outside.

Incidentally, the above-mentioned first embodiment, second embodiment and fifth embodiment
In the embodiment and the sixth embodiment, the channel waveguides 4 and 6 are used.
Electrodes 11, 71, 124, 136, 161, 17 for applying voltage to 3, 125, 127, 153, 166.
4 are waveguides 4, 63, 125, 127, 153, 1 respectively.
Although the two-electrode arrangement is symmetrical with respect to 66, the three-electrode arrangement may be optimal depending on the condition of the substrate used (in the case of a crystal substrate, the direction of the crystal axis, etc.). Select the appropriate electrode arrangement.

FIG. 12 shows a flat substrate inclination detecting device according to a seventh embodiment of the present invention. As shown in FIG. 12, in the flat substrate inclination detecting apparatus according to the present embodiment, the semiconductor laser light source 201 and the half mirror 202 for deflecting the light emitted from the semiconductor laser light source 201 are collimated to collimate the light and generate a parallel light flux on the flat substrate 2.
The collimator lens 204 for irradiating the laser beam 05 is arranged in order on the optical axis to provide an illumination optical system. Further, the flat substrate tilt detecting apparatus of the present embodiment further includes a three-dimensional channel waveguide 227 and a photodetector 208 including a silicon photodiode whose light-receiving surface is divided into four parts. The collimator lens 204 also serves as a condensing optical system that condenses the reflected light from the flat substrate 205. The three-dimensional channel waveguide 227 and the photodetector 208 form an optical system for detecting the light reflected by the flat substrate 205. The light receiving surface of the detector 208 is composed of four square light receiving surfaces 209, 210, 211 and 212 having the same area. Four light receiving surfaces 209, 210, 211, 2
12 are arranged in a grid pattern along the XY axes. The detector 208 is aligned so that the center of the light-receiving surface is aligned with the center of the exit 207b of the three-dimensional channel waveguide, and is joined to the exit 207b.

In addition, the light receiving surfaces 209 and 21 of the detector 208.
The signal lines 22 for outputting the detected light amount as an electric signal to the signal processing circuit 228 are connected to 0, 211 and 212.
9,230,231,232 are connected. The signal processing circuit 228 for processing these signals includes a sum detecting means 213 for adding output signals of the light receiving surface 209 and the light receiving surface 211 adjacent to each other along the X axis, and the light receiving surface adjacent to each other along the X axis. 210 and a sum detecting means 217 for adding the output signals of the light receiving surface 212. Further, the sum detection means 214 for adding the output signals of the light receiving surfaces 209 and 210 adjacent to each other along the Y axis, and the output signals of the light receiving surface 211 and the light receiving surface 212 also adjacent to each other along the Y axis are added. And a sum detection means 218 for The differential detector 221 obtains the difference in the amount of light in the Y direction by detecting the differential signal I2 of the output signals of the sum detecting means 213 and the sum detecting means 218. The differential detector 222 is the sum detection means 21.
4 and the differential signal I1 of the output signal of the sum detection means 218 are detected to obtain the difference in the light amount in the X direction.

The three-dimensional channel waveguide 227 will be further described. The three-dimensional channel waveguide 227 is made of SiO _x N _y having a refractive index of 1.475 as a material and has a width (X direction in FIG. 12) of 3 μm and a depth (Y direction of FIG. 12) of 3 μm. It is a double-mode three-dimensional channel waveguide composed of a cladding portion 206 made of SiO ₂ having a ratio of 1.465. When the mode order of the waveguide 227 in the X direction is p and the mode order in the Y direction is q, and the mode of the waveguide 227 is represented by E _pq , E ₀₀ , E ₁₀ , E
Only the ₀₁ mode propagates as a guided mode, and the E ₁₁ mode cannot propagate.

The entrance 20 of the core portion 207 of the waveguide 227
The length L from 7a to the outlet 207b is L≈mL ₀₁ and L≈nL ₀₂ , where L ₀₁ is the complete coupling length of the E ₀₀ -E ₁₀ mode and L ₀₂ is the complete coupling length of the E ₀₀ -E ₀₁ mode. (M = 1, 2, ...) And (n = 1, 2, ...).

A method of manufacturing the three-dimensional channel waveguide 227 will be described. S with a refractive index of 1.465 to be the clad
Si with a refractive index of 1.475 to be the core is formed on the iO ₂ substrate.
After forming the O _x N _y film by RF sputtering, the SiO _x N _y film is patterned into a core shape by lithography. By adjusting the amount of oxygen and the amount of nitrogen introduced at the time of RF sputtering, it is possible to adjust x and y of the SiO _x N _y film to have an arbitrary refractive index. Next, a SiO ₂ film is formed by RF sputtering to cover the periphery of the core-shaped SiO _x N _y film with the SiO ₂ film.
Thereby, the core portion 207 made of SiO _x N _y is used.
Then, a clad portion made of SiO ₂ is formed. Finally, it is cut into the above-mentioned length L, and the entrance and the exit are polished to complete.

Next, the operation of the inclination detecting device for a flat substrate of this embodiment will be described.

In FIG. 12, a semiconductor laser light source 201
The light emitted from the mirror is reflected by the half mirror 202, enters the collimator lens 204, and irradiates a plane substrate 205 with a parallel light flux. The light reflected on the surface of the flat substrate 205 passes through the collimator lens 204 again, and then passes through the half mirror 202.
Through the core 207 of the three-dimensional channel waveguide 227.
The light is focused on the entrance port 207a. The three-dimensional channel waveguide 227 is a waveguide having a double mode in the width direction (X direction) and the direction (Y direction) perpendicular thereto, and the light propagating in the core portion 207 of the three-dimensional channel waveguide 227 is The light-receiving surface emitted from the emission port 207b and joined to the core portion 207 reaches the photodetector 208 which is divided into four. The photodetector 208 is bonded so that the center of the four-divided light receiving surface and the center of the three-dimensional channel waveguide 227 coincide with each other.

Assuming that the mode order in the width direction of the waveguide is p and the mode order in the direction perpendicular to the width direction of the waveguide is q, and the mode of the waveguide is represented by E _pq , as described above. If the planar substrate 205 is inclined in the width direction (X direction) of the waveguide, the three-dimensional channel waveguide 227
Both the E ₀₀ and E ₁₀ modes are excited in the core portion 207 of the.
The intensity of the sum signal 216 obtained by the sum detection means 214 of the output of the light receiving surface 209 of the photodetector 208 and the output of the light receiving surface 210 due to the interference of both modes, and the sum detection of the output of the light receiving surface 211 and the output of the light receiving surface 212. The intensities of the sum signal 220 obtained by the means 218 are not equal. Therefore, the light receiving surfaces 209 and 210 of the photodetector 208 are detected by the differential detecting means 222.
Sum signal 216 and sum signal 220 of light receiving surfaces 211 and 212
By taking the differential signal 224, the inclination of the waveguide of the plane substrate 205 in the width direction (X direction) can be detected. At this time, no signal is output from the differential means 221.

Similarly, when the plane substrate 205 is inclined in the direction (Y direction) perpendicular to the width direction of the waveguide, both the E ₀₀ and E ₀₁ modes are excited in the core portion 207 of the double mode waveguide 227. It The intensity of the sum signal 215 obtained by the sum detection means 213 of the output of the light receiving surface 209 of the photodetector 208 and the output of the light receiving surface 211 due to the interference of both modes, and the light receiving surface 2
The intensity of the sum signal 219 obtained by the sum detection means 217 of the output of 10 and the output of the light receiving surface 212 is not equal. Therefore, the differential detection means 221 causes the sum signal 215 of the light receiving surfaces 209 and 211 of the photodetector 208 and the light receiving surfaces 210 and 21.
By taking the differential signal 223 of the sum signal 219 of 2
The tilt of the plane substrate 205 in the direction perpendicular to the width direction of the waveguide (Y direction) can be detected. At this time, no signal is output from the differential means 222.

Similarly, when the plane substrate 205 is not tilted, only the E ₀₀ mode is excited. The intensity of the signal 215 obtained by the sum detection means 213, the intensity of the signal 219 obtained by the sum detection means 217, the intensity of the signal 216 obtained by the sum detection means 214, and the intensity of the signal 220 obtained by the sum detection means 218. Are the same, and it is detected that the plane substrate 205 is not inclined.

Furthermore, the plane substrate 205 is moved in the Y direction in the X direction.
When it is also inclined in the direction, the modes E ₀₀ , E ₁₀ , and E ₀₁ are excited. At this time, due to the interference of each mode, the light receiving intensity of the light receiving surfaces 209, 210, 211, and 212 is different, so that the differential signals 223 and 224 are output from both the differential unit 221 and the differential unit 222, and the X direction and the Y direction. The tilt of the substrate in the direction is detected.

In this embodiment, the illumination light is not propagated through the waveguide, and the laser light source is separate. However, instead of the detector whose light-receiving surface is divided into four, a semiconductor laser and photodiode are integrated. By using, the waveguide can also be used as a waveguide for illumination. In that case, the labor of adjustment can be omitted.

As described above, according to each of the embodiments, it is possible to provide the inclination detecting device for the flat substrate which is capable of detecting the inclination with high accuracy, though it is a small device having an easy and simple structure using the waveguide. . In the first to sixth embodiments, the light for illuminating the flat substrate is propagated through the central branch waveguide and is emitted from the main waveguide, so that the end face emitting the illumination light and the reflected light are The end face to be incident becomes the same end face,
Since the reflected light returns to the end face through the same optical path as the illumination light, a tilt detection device for a flat substrate that does not require complicated alignment is provided.

Further, in the second and third embodiments, a single-mode main waveguide is realized for the light for illuminating the flat substrate, and a double-mode main waveguide is realized for the reflected light from the flat substrate. . As a result, it is possible to illuminate the flat substrate with a light spot that is centrosymmetrical and has no unevenness.
It is possible to detect the inclination of the flat substrate more accurately.

Further, in the fourth and fifth embodiments of the present invention, the means for removing the return light to the light source is provided on the waveguide, so that the fluctuation of the output light of the light source due to the return light can be avoided. it can. Furthermore, when the waveguide is made of a material having an electro-optical effect, the voltage can be applied from the electrodes to change the complete coupling length.
By changing the perfect coupling length according to the length of the double mode waveguide so as to satisfy the condition required for detection, the allowable error range of the waveguide can be increased, thus improving the manufacturing efficiency. be able to. Furthermore, by arranging the waveguide structures in two directions as in the sixth and seventh embodiments, the inclination of the flat substrate can be detected two-dimensionally.

In this way, electrical means for matching the emitting portion of the illumination light and the incident portion of the reflected light, providing a means for removing the returning light, detecting the two-dimensional inclination, and providing an electrode. The fact that the manufacturing efficiency can be improved by means of this embodiment is made possible for the first time because the present embodiment uses the waveguide.

[0109]

As described above, according to the present invention, since the waveguide is used, there is no need for complicated alignment, and a flat substrate tilt detecting device capable of detecting tilt accurately with a compact structure. Can be provided.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of a flat substrate inclination detection device according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a conventional flat substrate tilt detection device.

FIG. 3 is an explanatory diagram showing an incident light intensity distribution and a waveguide path in a double mode channel waveguide in the flat substrate tilt detecting device of the first embodiment.

FIG. 4 is a graph showing the behavior of reflected light from the flat substrate in the flat substrate inclination detection device of the first embodiment.

5 is a difference signal output of the photodetector in the device of FIG.
Explanatory drawing which showed the relationship of the shift | offset | difference between an incident light spot and the center of a double mode waveguide.

FIG. 6 is a block diagram showing the configuration of a flat substrate inclination detection device according to a second embodiment of the present invention.

FIG. 7 is an explanatory diagram showing a configuration of a waveguide portion of a tilt detection device for a flat substrate according to a second embodiment.

FIG. 8 is an explanatory diagram showing a configuration of a waveguide portion of a tilt detection device for a flat substrate according to a third embodiment.

FIG. 9 is a block diagram showing the configuration of a flat substrate tilt detection device according to a fourth embodiment.

FIG. 10 is a block diagram showing the configuration of a flat substrate inclination detection device according to a fifth embodiment.

FIG. 11 is a block diagram showing the configuration of a flat substrate inclination detection device according to a sixth embodiment.

FIG. 12 is a block diagram showing the configuration of a flat substrate inclination detection device according to a seventh embodiment.

[Explanation of symbols]

1, 60, 100, 120, 150, 164, 201
..Laser light sources, 3, 62, 101, 103, 122,
123, 126, 152, 165 ... Single-mode channel waveguides, 2, 61, 99, 128, 151, 1
75 ... Lithium niobate substrate, 63, 104, 12
7 ... Channel waveguides that are single mode for guided light of ordinary rays and double mode for guided light of extraordinary rays 4, 125, 153, 166 ... Double mode channel waveguides, 9 10, 69, 70, 11
0, 111, 134, 135, 159, 160, 16
9, 170 ... Channel waveguide, 11, 71, 11
2, 124, 136, 161, 174 ... Electrodes, 1
2, 13, 72, 73, 113, 114, 121, 13
8, 139, 162, 163, 172, 173, 208
... Photodetector, 227 ... Three-dimensional channel waveguide.

Claims (20)

[Claims] 1. Illuminating means for irradiating a plane substrate with light, detecting means for detecting reflected light from the plane substrate, light emitted from the illuminating means and reflected light from the plane substrate. And a waveguide portion for propagating, and the waveguide portion is connected to the main waveguide, a branch portion for branching the main waveguide into three waveguides, and the branch portion. 3 branch waveguides, the illuminating means is arranged at a position where light is incident on a central branch waveguide of the 3 branch waveguides, and the detecting means is provided with the 3 branch waveguides. The main waveguide is a double-mode waveguide, and the central branch waveguide among the three branch waveguides is arranged at a position for detecting light propagating through the branch waveguides on both sides of the waveguide. A single mode waveguide for the light from the illumination means, and the central branch waveguide and the The trunk waveguide means that the illumination light emitted from the illuminating means propagates in the 0th mode and irradiates the planar substrate from the end face of the master waveguide, and the trunk waveguide is diverged from the planar substrate. Reflected light in one or both of the 0th-order mode and the 1st-order mode is propagated, and the branching portion propagates the light propagated in the main waveguide to both sides of the three branch waveguides. An inclination detecting device for a flat substrate, characterized by being distributed to a waveguide. 2. The optical component for converting light emitted from the end face of the main waveguide into parallel light is arranged between the end face of the main waveguide and the planar substrate. A flat substrate inclination detecting device characterized by the above. 3. The tilt detection of a flat substrate according to claim 1, wherein the main waveguide is made of a material having an electro-optical effect, and has an electrode for applying a voltage to the main waveguide. apparatus. 4. The flat substrate according to claim 1, wherein the waveguide portion is formed on a semiconductor substrate, and the photodetection means is formed on the semiconductor substrate together with the waveguide. Tilt detection device. 5. The flat substrate tilt detecting device according to claim 4, wherein the illumination means is formed on the semiconductor substrate together with the waveguide. 6. When the length of the main waveguide is L and the perfect coupling length of the even-odd mode in the main waveguide is Lc in claim 1, L = mLc (m = 1, 2 ,.・ ・) Inclination detection device for flat substrates, which satisfies the relationship 7. The complete coupling length Lc between even and odd modes in the main waveguide is Lc ₁ due to an electro-optical effect by applying a voltage to an electrode arranged on the main waveguide in claim 3. When a change is made to, the inclination detecting device for a flat substrate is characterized in that L = mLc ₁ (m = 1, 2, ...) Is established for the length L of the double mode region. . 8. The conversion means for converting the polarization direction is arranged between the end face of the main waveguide and the plane substrate, and the main waveguide has a material having anisotropy in refractive index. Is a single-mode waveguide for linearly polarized light of polarization direction a, and polarization direction b (where a ≠
b) is a double mode waveguide for linearly polarized light, the illuminating means emits linearly polarized light in the polarization direction a, and the central branch waveguide and the main waveguide are emitted from the illuminating means. The illumination light in the polarization direction a propagates in the 0th order mode, irradiates the flat substrate from the end face of the main waveguide, and the conversion means emits linearly polarized light in the polarization direction a emitted from the end face of the main waveguide. Is converted into circularly polarized light, and the circularly polarized reflected light reflected by the plane substrate is converted into linearly polarized light in the polarization direction b. Further, the main waveguide converts the reflected light in the polarization direction b from the plane substrate. An apparatus for detecting inclination of a flat substrate, which propagates in either or both of a 0th-order mode and a 1st-order mode. 9. The waveguide according to claim 8, wherein the main waveguide is 3
Composed of the above materials, one of the materials is
An apparatus for detecting inclination of a flat substrate, wherein one of the light in the polarization direction a and the light in the polarization direction b becomes a core and the other light becomes a clad. 10. The tilt detection of a flat substrate according to claim 8, wherein the illuminating means includes a light source and a polarizing means that allows only light in a polarization direction a of light emitted from the light source to pass therethrough. apparatus. 11. The light of polarization direction b, which is incident on the central branch waveguide from the end face of the main waveguide, propagates through the central branch waveguide and is incident on the illuminating means. An inclination detecting device for a flat substrate, further comprising return light preventing means for preventing the occurrence of the above-mentioned problem. 12. The main waveguide according to claim 8,
A tilt detecting device for a flat substrate, comprising a lithium niobate single crystal in a clad and a lithium niobate single crystal in which a transition metal is diffused in a core. 13. The main waveguide according to claim 9,
A lithium niobate single crystal, a lithium niobate single crystal in which a transition metal is diffused, and a proton-exchanged lithium niobate single crystal are included, and the lithium niobate single crystal has a polarization direction a and a polarized light. The lithium niobate single crystal in which the transition metal is diffused and becomes a clad for the light in the direction b becomes the core in the light in the polarization directions a and b, and the proton-exchanged lithium niobate single crystal is A tilt detecting device for a flat substrate, which functions as a clad for light in the polarization direction a and as a core for light in the polarization direction b. 14. When the length of the main waveguide is L and the perfect coupling length of even-odd mode for light in the polarization direction b in the main waveguide is Lc in claim 8, L = mLc (m = 1, 2, ...) A flat substrate inclination detecting device characterized by satisfying the following relationship. 15. The main waveguide according to claim 8,
The waveguide section is made of a material having an electro-optical effect, and the waveguide section further has voltage applying means for applying a voltage to the main waveguide, and the length of the main waveguide is L, and the main waveguide is When the even-odd mode complete coupling length with respect to the light in the polarization direction b at Lc is Lc, the complete coupling length Lc is changed to Lc1 by the electro-optic effect by applying a voltage to the main waveguide L = An inclination detecting device for a flat substrate, wherein the relationship of mLc1 (m = 1, 2, ...) Is established. 16. The waveguide section according to claim 1, wherein the waveguide section has first and second waveguide sections provided with the main waveguide, the branch section, and the three branch waveguides, respectively. The illuminating means allows light to enter at least one of the central branch waveguides of the first and second waveguide portions, and the detecting means includes both sides of the first and second waveguide portions. Has first and second detecting means for respectively detecting the light propagating through the branch waveguides, and the first and second waveguide portions are reflected from the same point on the plane substrate. The main waveguides of the first and second waveguide portions are respectively arranged at positions where light is incident on the main waveguide, and the main waveguides have a waveguide structure in one direction perpendicular to a propagation direction. In the second waveguide part, the direction having the waveguide structure of each main waveguide part is Inclination detecting unit for a planar substrate, characterized in that it is arranged so that difference. 17. Illuminating means for irradiating light onto the flat substrate, detecting means for detecting reflected light from the flat substrate, and a waveguide section for propagating the reflected light from the flat substrate. The waveguide section has a double-mode waveguide structure in at least two directions perpendicular to the direction in which the reflected light propagates, and the reflected light has a zero-order mode and a zero-order mode in the two directions, respectively. Propagating in either one or both modes of the primary mode, the detecting means is arranged at a position for detecting the light propagating through the waveguide part among the reflected light from the planar substrate, An inclination detecting device for a flat substrate, wherein the intensity distribution of light in the at least two directions of the part is detected. 18. The detecting means according to claim 17,
A tilt detecting device for a flat substrate, comprising a light receiving portion divided into two in each of the at least two directions, as a center of an emission end face of the waveguide portion. 19. The waveguide section according to claim 17,
Waveguide structure having a waveguide structure in two directions perpendicular to the propagation direction, where the mode order in one direction of the two directions having the waveguide structure is p and the mode order in the other direction is q When the mode is represented by Epq, the waveguide has a refractive index such that E ₀₀ , E ₀₁ , and E ₁₀ modes can be propagated and E ₁₁ mode cannot be propagated. apparatus. 20. In claim 17, the length of the waveguide is L, the complete coupling length of the E ₀₀ mode and the E ₀₁ mode is Lc ₁ , and the complete coupling of the E ₀₀ mode and the E ₁₀ mode is performed. When the length is Lc ₂ , L = mLc ₁ and L = nLc ₂ (m = 1, 2, ...) (n = 1, 2, ...) apparatus.