JP2000241114A - Surface shape-measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To quickly measure a surface shape by simultaneously applying light to a plurality of points on a specimen, and by simultaneously detecting each reflected light from an application part. SOLUTION: Light emitted from a light source 1 is set to parallel light by a collimator lens 2, and enters a half mirror array 3. Then, one part is reflected by a half mirror 7 and is directed toward an objective lens array 4, and the remainder is transmitted toward the adjacent half mirror 7. Due to the repetition, the light emitted from the light source 1 is divided by the number of the half mirrors, each light being divided by each half mirror is simultaneously condensed onto a plurality of the points of a specimen 5 by each objective lens of the objective lens array 4. Each reflected light reflected by each of the plurality of points on the specimen 5 passes through each of objective lens of the objective lens array 4, is transmitted through each half mirror 7 of the half mirror array 3, and is condensed to each incidence position 11 of each incidence end face of a double mode waveguide array 8 being formed on a substrate 10 by a condensing lens array 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a surface profile measuring device using an optical waveguide.

[0002]

2. Description of the Related Art In recent years, optical waveguides have attracted attention in the fields of optical communication and optical measurement. The reason is that the size and weight of the optical system can be reduced by using the optical waveguide.
This is because there is an advantage that adjustment of the optical axis becomes unnecessary. As one of measuring instruments using an optical waveguide, Japanese Patent Application Laid-Open No. Hei 6-331841 discloses a technique of a focus detection device. In Japanese Patent Application Laid-Open No. Hei 6-331841, a double mode waveguide is used as an optical waveguide as shown in FIG.

[0003] When a laser beam is made incident on a double mode waveguide, the laser beam enters the waveguide in accordance with the amplitude distribution of the incident laser beam.
The next mode and the first mode are excited. These two modes interfere in the waveguide, resulting in an asymmetry in the overall light intensity distribution. Here, there are two factors that cause asymmetry of the light intensity distribution in the waveguide. One is when the intensity distribution of the incident laser light is asymmetric, and the other is when the phase of the incident laser light is asymmetric. If the length of the double mode region is appropriately selected, the asymmetry in any case can be detected well (H. Okinawa).
nd J.J. Iwasaki, Optics Commu
nations 85 (1991) 177).

Using the mode interference in the double mode waveguide, displacement (focal position shift) of the incident laser light in the optical axis direction is detected. The incident position of the laser spot is adjusted to come to a position slightly shifted from the center of the double mode waveguide. When the laser spot is at the focal position, the light phase at the incident position has no inclination (FIG. 4B), but when the laser spot deviates from the focal position, (See Fig. 4)
(A), (b)), the focus position shift is detected by detecting the asymmetry of the phase distribution due to this.

In FIG. 3, light emitted from a light source 101 is collimated by a collimator lens 102, reflected by a half mirror 103, and condensed and radiated to one point on a test object 105 by an objective lens 104. Is done. Test object 1
The light reflected on the light source 05 passes through the objective lens 104 again, passes through the half mirror 103, and is formed by the condenser lens 106 on the double mode waveguide 111 formed on the substrate 110.
Is focused at the incident position 107. The incident position 107 is located at a position slightly shifted in the lateral direction from the center of the double mode waveguide 111.

The double mode waveguide 111 branches into two waveguides 112 and 113 at the position of the length L. Waveguide 11
If the light emitted from the light emitting elements 2 and 113 is detected by the photodetectors 114 and 115 and the differential signal is obtained by the differential amplifier 116, the differential signal causes a focus error (a focus position shift amount) as shown in FIG. Since the relationship is constant, the relationship between the differential signal and the focus error is measured by another method to obtain the relationship shown in FIG. With reference to FIG. 5, the focus error signal 117 is obtained from the measured magnitude of the differential signal, and the shift amount of the focal position of the test object 105 can be known.

In the conventional example shown in FIG. 3, the length L of the double mode waveguide is represented by the phase distribution of the object when the perfect coupling length (the length at which the phase difference between the 0th-order mode and the 1st-order mode is π) is Lc. L = Lc (2m + 1) / 2 (m = 0, 1, 2,...) (1).

[0008]

Problems to be Solved by the Invention Japanese Patent Application Laid-Open No. 6-33184
In order to measure the surface shape of the object to be measured using the focus detection device shown in FIG. 3 in FIG. 3, the focused light spot is scanned over the entire surface of the object to be measured, or It is necessary to scan the test object against a stationary light spot. In this case, there is a problem that it takes a long time to measure the entire test object because the light spot condensed on the test object, that is, the measurement spot is one point. As an example, it took several minutes to several tens of minutes to measure the planar shape of a 6 to 8 inch wafer.

An object of the present invention is to provide an inexpensive surface shape measuring apparatus which can solve the above-mentioned problems and can measure the surface shape in a short time.

[0010]

In order to solve the above-mentioned problems, the present invention firstly comprises a method of: "irradiating two or more points on a test object at the same time with light; And a detection unit for simultaneously detecting each reflected light from each irradiation point, wherein the detection unit comprises a channel waveguide formed on a substrate for allowing the reflected light to enter for the detection. The present invention provides a surface shape measuring device (claim 1).

According to the present invention, in a surface shape measuring apparatus, a light spot is applied to a test object by multi-spot irradiation.
A plurality of waveguides on the detection side are also arranged in an array. In this way, the invention is an invention in which the measurement time is reduced by simultaneously measuring multiple points. Secondly, "each of the channel waveguides comprises a double-mode waveguide, and two waveguides branched from the double-mode waveguide, and the detection unit further comprises, for each of the channel waveguides, 2. A surface shape measuring apparatus according to claim 1, wherein each detecting element for detecting light propagating through said two waveguides is provided at each end of said two waveguides. )"I will provide a.

Third, "the reflected light is adjusted to be focused at a position slightly shifted from the center of the double mode waveguide, and the asymmetry of the light intensity distribution in the double mode waveguide is detected. The surface shape of the object to be measured is measured by performing the measurement. Fourth, "L = Lc (2m + 1) / where L is the length of the double mode waveguide and Lc is the complete coupling length between the 0th and 1st modes in the double mode waveguide. 2 (m = 0, 1, 2, ...
The surface shape measuring device according to any one of claims 2 to 3, characterized by satisfying the following (4).

Fifth, at least a core portion of the double mode waveguide is made of a material exhibiting an electro-optic effect or a thermo-optic effect, and furthermore, electrodes for applying a voltage to the double mode waveguide are provided on both sides. The length of the double-mode waveguide is L, and the complete coupling length between the zero-order mode and the first-order mode in the double-mode waveguide when no voltage is applied between the two electrodes is Lc 1. age,
When the complete coupling length when an appropriate voltage is applied is Lc different from Lc1, L = Lc (2m + 1) / 2 (m = 0, 1, 2,...)
The surface shape measuring device according to any one of claims 2 to 3, wherein In the above part, a claim will be entered after the examination is completed (Claim 5).

[0014]

[Embodiment 1] FIG. 1 shows a schematic configuration diagram of a surface shape measuring apparatus according to Embodiment 1 of the present invention. In FIG. 1, 1 is a light source, 2 is a collimator lens,
3 is a half mirror array, 4 is an objective lens array, 5 is a test object, 6 is a condensing lens array, 8 is a double mode waveguide array, 13 and 14 are each a waveguide, and 10 is a waveguide. Substrate, 100 is a photodetector array, 9 is a plurality of differential amplifiers. The half mirror array 3 is composed of half mirrors 7 arranged in a straight line, the number of which is equal to or more than the number of light spots to irradiate the test object 5. The half mirror 7 includes an optical thin film and the like, and separates incident light into reflected light and transmitted light. The objective lens array 4 is composed of a plurality of objective lenses arranged in a straight line, the number being equal to or more than the number of light spots to irradiate the test object 5. The condenser lens array 6 is composed of a plurality of condenser lenses arranged in a straight line, the number being equal to or more than the number of light spots to be irradiated on the object 5 to be inspected. The double mode waveguide array 8 is composed of a plurality of pairs of double mode waveguides 12 and waveguides 13 and 14 arranged in a straight line, the number being equal to or greater than the number of light spots irradiating the test object 5. The photodetector array 100 includes a plurality of pairs of photodetectors 15 arranged in a straight line, the number being equal to or more than the number of light spots irradiating the test object 5.
16. The plurality of differential amplifiers 9 include a plurality of linearly arranged differential amplifiers 17 equal to or more than the number of light spots that irradiate the test object 5.

The light emitted from the light source 1 is collimated by the collimator lens 2 and then enters the half mirror array 3. A part of the light incident on the half mirror array 3 is reflected by the half mirror 7 to the objective lens array, and the rest of the light is transmitted toward the adjacent half mirror.
By this repetition, the light emitted from the light source 1 is split by the number of half mirrors, and each light split by each half mirror is simultaneously focused on a plurality of points on the test object 5 by each objective lens of the objective lens array 4. It is collected. Each reflected light reflected at a plurality of points on the test object 5 passes through the objective lenses of the objective lens array 4 again and passes through the half mirror array 3.
Through each half mirror 7 and by each condenser lens of the condenser lens array 6, each incident position of each entrance end face 23 of each double mode waveguide of the double mode waveguide array 8 formed on the substrate 10. The light is condensed on 11. Here, each incident position 11 is adjusted so as to be located at a position slightly shifted in the lateral direction from the center of each double mode waveguide.

FIG. 6 shows the meaning of the slightly shifted position.
Will be described. FIG. 6 illustrates the case where the focal position shift amount is zero, 21 is a light beam condensed from one condensing lens constituting the condensing lens array, 20 is an equal phase surface, and B is a double mode waveguide. The center position of the light spot image condensed and focused so as to be incident on 12 is shown, and this center position is called an incident position 11. When the incident position is B, the portion 22 on the incident end face 23 of the condensed and focused light spot image enters the double mode waveguide 12. The incident position is not preferable because the wavefront does not tilt at the center position C of the double mode waveguide 12. Conversely, if the incident position shifts too far from the center position of the double mode waveguide 12 and reaches the position A, the light is condensed. The formed light spot image is not applied to the incident end face of the double mode waveguide 12 at all, and light is not incident, which is not preferable. The incident position is determined to be a position where the maximum sensitivity is generally obtained between A and C not including A and C.

Each incident end face 2 of each double mode waveguide 12
3 are propagated in each double mode waveguide 12 while causing mode interference, and when propagated from each incident end face 23 by the length of L, each incident light is converted into each waveguide 1.
Branch to 3 and 14. The light emitted from each of the waveguides 13 and 14 after being branched from one double mode waveguide 12 and propagated through each of the waveguides 13 and 14 is transmitted to each of the waveguides 13 and 14.
Are detected by the photodetectors 15 and 16 provided at the ends of the photodetector 15 respectively.
6, that is, the differential signal 18 is obtained. This differential signal 18 is taken simultaneously for each double mode waveguide 12.

If the length L of each double mode waveguide 12 is Lc, the perfect coupling length (the length at which the phase difference between the 0th and 1st modes of the propagation mode of the double mode waveguide is π) is Lc. L = Lc (2m + 1) / 2 (m = 0, 1, 2,...) (1) which is a condition for observing the phase distribution of

As described in the conventional example, from the relationship shown in FIG. 5, it is possible to know a focus error (a shift amount of the focus position) of the focal point of the irradiation light on the test object 5 from the differential signal 18, and The amount of displacement corresponds to the displacement of the focal point of the irradiation light. Therefore, by scanning the object, the surface shape of the object can be measured. In the surface shape measuring apparatus having one light spot as in the conventional example, the entire surface of the test object must be scanned with only one light spot, whereas the surface shape measuring apparatus according to the first embodiment is required. In this case, since multiple points can be measured at the same time, in order to measure the entire surface of the object 5 to be measured, scanning may be performed by sharing each part of the surface of the object 5 with multiple light spots. Therefore, the measurement time can be significantly reduced. Second Embodiment FIG. 2 shows a surface shape measuring apparatus according to a second embodiment of the present invention.

In FIG. 2, 1 is a light source, 21 is a branch waveguide, 20
Is a substrate on which the branch waveguide 21 is formed, 30 is a collimator lens array, 31 is a half mirror, 4 is an objective lens array, 5 is an object to be measured, 26 is a condenser lens array, 8 is a double mode waveguide array, 12 Is a double mode waveguide,
13 and 14 are waveguides, 10 is a substrate on which the waveguides are formed, 100 is a photodetector array, and 9 is a plurality of differential amplifiers.

The branch waveguide 21 has a plurality of emission ends equal to or more than the number of light spots to be irradiated on the object 5 to be inspected. The array 24 forms an image on the object 5 as a plurality of light spots. Here, the branch waveguide 21 is preferably a single mode waveguide. The half mirror 23 includes an optical thin film and the like, and separates incident light into reflected light and transmitted light (transmitted light is not shown). The double mode waveguide array 8 is composed of a plurality of pairs of double mode waveguides 12 and branch waveguides 13 and 14 arranged in a straight line, the number being equal to or greater than the number of light spots irradiating the test object 5. The photodetector array 100 includes the object 5
And a plurality of pairs of photodetectors 15 and 16 arranged in a straight line, the number of which is equal to or more than the number of light spots to be irradiated. The plurality of differential amplifiers 9 include a plurality of linearly arranged differential amplifiers 17 equal to or more than the number of light spots that irradiate the test object 5.

Light emitted from the light source 1 is incident on a branch waveguide 21 formed on a substrate 20, is branched into a plurality of waveguides, and is emitted from a plurality of waveguide end faces (emission ends). The emitted light is collimated by a collimator lens 22, reflected by a half mirror 23,
As a result, a plurality of light spots are focused on the test object 5. Light reflected at a plurality of points on the test object 5 passes through the objective lens 4 again, passes through the half mirror 23, and is condensed by the condenser lens 26 to each of the double mode waveguide arrays 12 formed on the substrate 10. Each incident position 1 on the incident end face 23
The light is condensed on 1. That is, a plurality of points form an image on each incident end face. Here, the incident position 1 on each incident end face 23
Numerals 1 are each adjusted to be at a position slightly shifted laterally from the center of each double mode waveguide. The meaning of the position slightly shifted in the horizontal direction is exactly the same as in the first embodiment. Each incident light incident on each incident position 11 of each double mode waveguide 12 propagates through each double mode waveguide 12 while causing mode interference. Branches into the waveguides 13 and 14. The light emitted from each of the waveguides 13 and 14 after being branched from one double mode waveguide 12 and propagated through each of the waveguides 13 and 14 is transmitted to each of the waveguides 1 and 14.
The signals are detected by photodetectors 15 and 16 provided at the ends of the photodetectors 3 and 14, respectively. The difference between the output of the photodetector 15 and the output of the photodetector 16, that is, a differential signal 18 is obtained by a differential amplifier 17. . This differential signal 18 is taken simultaneously for each double mode waveguide 12.

The length L of each double mode waveguide 12 is exactly the same as that of the first embodiment, and the perfect coupling length (the phase difference between the 0th mode and the 1st mode of the propagation mode of the double mode waveguide is π and π). Let Lc be Lc, and L = Lc (2m + 1) / 2 (m = 0, 1, 2,...) (1) which is a condition for observing the phase distribution of the object.

As described in the first embodiment, from the relationship shown in FIG. 5, it is possible to know a focus error (a shift amount of a focus position) of a converging point of irradiation light on the test object 5 from the differential signal 18. , The focal position shift amount corresponds to the displacement of the focal point of the irradiation light. Therefore, by scanning the object, the surface shape of the object can be measured. In the surface shape measuring apparatus having one light spot as in the conventional example, the entire surface of the test object must be scanned with only one light spot, whereas the surface shape measuring apparatus according to the second embodiment is used. In this case, since multiple points can be measured at the same time, in order to measure the entire surface of the object 5 to be measured, each partial area of the surface of the object 5 may be scanned with multiple light spots. Therefore, the measurement time can be significantly reduced.

In the first and second embodiments, an example is shown in which a double mode waveguide is used as a detection unit. However, a waveguide interferometer as disclosed in Japanese Patent Laid-Open No. 7-139908 is arranged in an array. A surface shape measuring device provided with a plurality of detectors is also included in the scope of the present invention. [Embodiment 3] FIG. 7 is a diagram for explaining the present embodiment. For simplicity, only one pair of the double mode waveguide and the two waveguides is shown, but these are applied to all the double mode waveguides of the double mode waveguide array shown in the first and second embodiments. The overall schematic configuration is the same as in the first and second embodiments except for the electrode portion.

In FIG. 7, reference numeral 23 denotes an incident end face, 11 denotes an incident position of a light spot image, 12 denotes a double mode waveguide, and at least a core portion is formed of a material such as lithium niobate having an electro-optical effect. . 24 and 25 are connected to electrodes, and 26 and 27 are connected to a power supply for applying a voltage between the electrodes 24 and 25. Reference numerals 13 and 14 denote two branched waveguides, and reference numerals 15 and 16 denote respective photodetectors.

Here, the length of the double mode waveguide is L, and the complete coupling length between the zero-order mode and the first mode in the double-mode waveguide when no voltage is applied between the two electrodes is Lc. 1, L ≠ Lc 1 (2m + 1) / 2 (m = 0, 1, 2,...)
+ Positive integer). Here, when an appropriate voltage is applied, the refractive index changes by applying the voltage because the waveguide is formed of an electro-optic material. As a result, it is assumed that the complete bond length has now changed to Lc different from Lc1. Thus, L = Lc (2m + 1) / 2 (m = 0, 1, 2,...)
Is a positive integer of the relationship.

The third embodiment provides a surface shape measuring apparatus which can be easily adjusted so as to satisfy the relational expression (1) between the length L of the double mode waveguide and the complete coupling length Lc. As described above, the core portion of the double mode waveguide is formed of a material having an electro-optic effect, but the core portion may be formed of a material having a thermo-optic effect. As this material, ordinary optical glass is preferable, but germanium-doped glass, particularly germanium-doped SiO glass, is more preferable. When a material having a thermo-optic effect is used, a heater is used instead of the electrodes 24 and 25.

As described above, the present invention has been described with reference to the first, second, and third embodiments. According to the present invention, the surface shape of a test object can be measured at a higher speed than a conventional apparatus. Further, according to the third embodiment, the relationship between the length of the double mode waveguide and the complete coupling length can be easily adjusted.

[0030]

As described above, since a plurality of points on the object to be measured can be measured at the same time, the surface shape can be measured at a higher speed than the conventional apparatus. Further, according to the third embodiment, the relationship between the length of the double mode waveguide and the complete coupling length can be easily adjusted.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a surface shape measuring device according to a first embodiment.

FIG. 2 is a schematic configuration diagram of a surface shape measuring device according to a second embodiment.

FIG. 3 is a schematic configuration diagram of a focus detection and displacement detection device according to a conventional example.

FIG. 4 is a diagram illustrating the principle of a conventional focus detection and displacement detection device.

FIG. 5 shows a relationship between a differential signal and a focus error signal of a conventional focus detection and displacement detection device.

FIG. 6 is an explanatory diagram of the meaning of an incident position slightly shifted in the lateral direction from the center of the double mode waveguide.

FIG. 7 illustrates Embodiment 3;

[Description of Signs] 1 light source 2 collimator lens 3 half mirror array 4 objective lens array 5 test object 6 condensing lens array 7 half mirror 8 double mode waveguide array 9 plural differential amplifiers 10 substrate 11 incident position 12 double mode Waveguide 13 Waveguide 14 Waveguide 15 Photodetector 16 Photodetector 17 Differential amplifier 18 Differential signal 20 Equi-phase plane 21 Light beam 22 Part of light spot image condensed and formed incident on double mode waveguide 23 Incident end face 24 Electrode 25 Electrode 26 Terminal connected to power supply 27 Terminal connected to power supply 30 Collimator lens array 31 Half mirror 100 Photodetector array A Indicates the incident position where light does not enter the double mode waveguide B Indicates the incident position of the light spot image C Indicates the center position of the double mode waveguide

Claims (5)

[Claims] An irradiation unit for simultaneously irradiating two or more points on a test object with light, and a detection unit for simultaneously detecting each reflected light from each irradiation point on the test object. A surface shape measuring device, wherein the detecting unit includes channel waveguides formed on a substrate for receiving the reflected lights for the detection. 2. Each of the channel waveguides comprises a double mode waveguide and two waveguides branched from the double mode waveguide, and the detecting unit further comprises: 2. The surface shape measuring apparatus according to claim 1, wherein each detecting element for detecting light propagating through the two waveguides is provided at each end of the two waveguides. 3. The method according to claim 1, wherein the reflected light is adjusted to be focused at a position slightly shifted from the center of the double mode waveguide, and the asymmetry of the light intensity distribution in the double mode waveguide is detected. 3. The surface shape measuring apparatus according to claim 2, wherein the surface shape of the test object is measured. 4. The length of the double mode waveguide is L,
When the complete coupling length between the zero-order mode and the first-order mode in the double mode waveguide is Lc, L = Lc (2m + 1) / 2 (m = 0, 1, 2,...)
The surface shape measuring device according to any one of claims 2 to 3, wherein 5. The double mode waveguide, wherein at least a core portion is made of a material exhibiting an electro-optic effect or a thermo-optic effect, and further comprises electrodes on both sides for applying a voltage to the double mode waveguide. The length of the double mode waveguide is L, and the 0th mode and the 1st mode in the double mode waveguide when no voltage is applied between the two electrodes.
When the complete coupling length with the next mode is Lc 1 and the complete coupling length when an appropriate voltage is applied is Lc different from Lc 1, L = Lc (2m + 1) / 2 (m = 0,1 , 2, ...
The surface shape measuring device according to any one of claims 2 to 3, wherein