JPH0694998A - Confocal laser scanning differential interference microscope - Google Patents

Abstract

PURPOSE:To provide a confocal laser scanning differential interference microscope capable of quantitatively measuring the level difference of a specimen in terms of height. CONSTITUTION:The specimen 7 is irradiated by 1st, 2nd and 3rd light spots 8, 9 and 10 arranged in order, and even and odd modes are excited in a double mode waveguide from the reflected light beam of the 2nd light spot 9 among three light spots 8, 9 and 10. By using the interference of the even and odd modes, the differential information of an area irradiated by the 2nd light spot 9 on the specimen is obtained. The reflected light beams of the 1st and the 3rd light spots 8 and 10 among three light spots 8, 9 and 10 are made to interfere to obtain a phase difference, so that a height difference between the areas of the specimen irradiated by the 1st and the 3rd light spots 8 and 10 is obtained.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a confocal laser scanning microscope.

[0002]

2. Description of the Related Art Regarding conventional confocal laser scanning differential interference microscopes, for example, OPTICS COMMUNICATION 1
st September 1991 No.2,3 Vol.85 pp177-182. As shown in FIG. 2, the conventional confocal laser scanning differential interference microscope includes a laser light source 101, a half mirror 102, and a condensing optical system 104, and condenses laser light onto an object 105 to be inspected. Irradiate. Object to be inspected 1
As a means for detecting the reflected light from 05, a substrate 106 having an electro-optical effect in which a channel waveguide is formed is provided. The channel waveguide includes a double mode waveguide region 107 having an incident end face on the detection surface, and two single mode waveguides 109 and 110 including the double mode waveguide 107.
And a photo-detection element 111, 1 for detecting light propagating through the two single-mode waveguides 109, 110 that are further branched.
Have twelve. An electrode 114 is provided on the substrate surface of the double mode waveguide region 107.

When the portion of the object 105 to be inspected which is illuminated by the laser spot has an inclination or a gradient of reflectance, an inclination occurs in the phase distribution or intensity distribution of the laser spot imaged at the incident end of the channel waveguide 107. , Two modes (fundamental mode and first mode) are excited in the double mode waveguide region 107 due to this inclination, and the signal 11 generated by the two photodetection elements 111 and 112 due to the interference of both modes.
From 3, it is possible to detect a minute step (phase information) or a reflectance change (amplitude information) of the object 105 to be inspected. Here, if the complete coupling length of the double mode waveguide 7 (the length at which the phase difference between the fundamental mode and the first mode is π) is Lc and the length L of the double mode region is L, then L = Lc (2m + 1) ( When m = 0,1,2, ...), the phase distribution of the reflected light due to the step of the object is detected, and when L = mLc (m = 1,2, ...), the object is transmitted. The intensity distribution of the reflected light based on the distribution of the reflectance and the reflectance is detected, and this configuration is a differential interference system.

As described above, by using the waveguide device as the light detecting means, the phase information and the amplitude information of the object to be measured can be obtained independently.

[0005]

However, in the configuration of the conventional confocal laser scanning microscope described above, it is possible to obtain differential information about the information of the phase distribution of the reflected light due to the step of the object to be inspected, It was not possible to quantitatively measure the height difference of the step.

Therefore, an object of the present invention is to provide a confocal laser scanning differential interference microscope capable of quantitatively measuring the height difference of the step of the object to be inspected.

[0007]

To achieve the above object, the present invention is to obtain a differential interference contrast image using a waveguide device and simultaneously measure a step difference by an interferometer composed of another waveguide device. .

That is, an illumination optical system for irradiating a light spot on the object to be inspected, a scanning means for moving the light spot relative to the object to be inspected, and the object to be inspected for the light spot. A confocal laser scanning differential interference microscope having a detection optical system for detecting reflected light from the illumination optical system, wherein the illumination optical system is arranged on the object to be inspected first, second, and third. Irradiate three light spots, and the detection optical system obtains the differential information of the region of the object to be inspected irradiated with the second light spot from the reflected light of the second light spot among the three light spots. From the first detection optical system to obtain and the reflected light of the first and third light spots of the three light spots, between the regions irradiated with the first and third light spots of the test object. A second detection optical system for obtaining step information The first detection optical system has a double mode waveguide section having an incident end on the optical path of the reflected light of the second light spot, and the light propagating through the double mode waveguide is split into two. A first waveguide optical system including a branching portion for guiding and two waveguides for respectively guiding and emitting the two lights branched by the branching portion, and a first waveguide optical system. First and second detection means, which are respectively disposed at the emission ends of the two waveguide portions of the system, to detect the intensity of the emitted light, and the detection signal of the first detection means and the second detection means. A second calculation optical system for calculating a difference from the detection signal, and the second detection optical system has two incident ends on the optical paths of the reflected light of the first and third light spots. The single mode waveguide section and the light propagating through the two single mode waveguide sections are combined. A second waveguide optical system, and a second single-mode waveguide section that guides and outputs the combined light of the multiplex section, and the second waveguide optical system. A confocal laser scanning differential interference microscope is provided, which is arranged at an emission end of one single-mode waveguide part of the system and has a third detection means for detecting the intensity of emitted light.

[0009]

In the confocal laser scanning differential interference microscope of the present invention, the first detection optical system detects the second light spot of the object to be detected from the reflected light of the second light spot among the three light spots. Obtain differential information of the illuminated area.

First, regarding the principle of obtaining differential information,
An overview will be given. The double-mode channel waveguide of the first waveguide optical system of the first detection optical system is provided on the optical path of the reflected light of one spot image in the middle of the three spot images on the object to be inspected by the illumination optical system. It is arranged so that the centers of the parts coincide. When the spot image amplitude distribution in the width direction of the waveguide has an origin at the spot center, only an even mode is excited in the double-mode waveguide if it is an even function. In other cases, even and odd modes are excited.

Here, if a waveguide branch for branching into two channel waveguides is provided following the double mode region, when only even modes are excited, an equal amount of light is distributed to the two branches, In other cases, even-mode and odd-mode interference occurs, so that the light amounts distributed to the two light-receiving surfaces are generally not equal.

Generally, not only the inclination of the object to be inspected with respect to the entrance of the double mode channel waveguide, that is, the physical inclination but also all inclinations that change the optical path length such as the refractive index inclination and the light transmittance distribution or the light reflectance distribution When there is an inclination, the amplitude distribution of the spot image has an odd function component, and at this time both even and odd modes are excited in the double mode waveguide, and as a result, the amounts of light distributed to the two branches are not equal. Therefore, it is possible to detect the microscopic inclination of the object to be inspected by converting the light amount of the two light receiving surfaces into an electric signal by the photodetector and detecting the difference signal between them.

Now, let θ be the inclination angle of the object to be detected with respect to the entrance of the double-mode waveguide, and sin θ = α. Slope θ
In the case of, the spot amplitude distribution is u (x), and the intrinsic electric field distribution of the double mode waveguide is fe (x) and fo (x) for both even and odd modes, respectively, and u (x), fe (x).
Is an even function and fo (x) is an odd function. The spot amplitude distribution uα (x) with an inclination is k = 2π / λ (λ = wavelength), and uα (x) ≈u (x) exp (ikαx) = u (x) [cos (kαx) + isin (kαx) )] (1)

Here, the even mode excitation efficiency η _e is

[0015]

[Equation 1]

On the other hand, the odd excitation efficiency η
_o is

[0017]

[Equation 2]

[0018] If the integration range is properly selected and | kαx | << 2π in this range, cos (kαx) ≈1, sin (kαx) ≈kαx, so u (x), fo (x), fe (x) are Since it is a constant function, it can be seen that η _e ≈ constant η _o ∝iα (4). The change in light intensity due to the interference between the even mode and the odd mode is I ∝ | η _e , where C ₁ and C ₂ are real constants and φ is the phase difference between the even and odd modes at the exit of the double mode waveguide. ± iη _o exp {iφ} | ² = | C ₁ ± iαC ₂ exp {iφ} | ² (5) Therefore, if exp {iφ} = ± i, then (5) is roughly I = C ₁ ² ± 2αC ₁ It becomes C ₂ (6) and an intensity change proportional to α is obtained, and a so-called differential image can be obtained. Therefore, in order to obtain such a differential image, it is necessary to introduce a phase difference of an odd multiple of 90 ° between both modes at the branch point of the double mode waveguide. For this reason, the length L from the entrance to the exit of the double mode waveguide is the well-known complete coupling length of both modes (the length at which the phase difference between the even and odd modes is 180 °) L _C. If set to _{L = L C (2m + 1} ) / 2 (m = 0,1,2, ···) (7) preferably with.

Since equation (1) considers the inclination of the object, it means that a phase object is assumed.

When the substrate has an electro-optical effect, the complete coupling length Lc can be changed by applying a voltage to this region through the electrodes arranged on the double mode region. Therefore, even if the length of the double mode region is a constant value L that does not satisfy the equation (7), it is possible to satisfy the equation (7) by adjusting the voltage. Therefore, it is possible to obtain the phase information of the object by applying a voltage using the electro-optical effect while keeping the mechanical length of the double mode region constant.

That is, by applying a voltage to the electrodes arranged on the double mode region of the channel waveguide,
The complete bond length Lc in the double mode region is changed to a different complete bond material Lc _2, and L≈Lc ₂ (2m + 1) / 2 (m = 0, 1, 2,・
..) is established, the phase information of the object can be obtained as in the above equation (7) in the case of Lc ₂ .

Further, the second detection optical system is a region where the first and third light spots of the object to be inspected are irradiated from the reflected light of the first and third light spots of the three light spots. Get the height difference between. Of the above-mentioned three spot images, two separate single mode channel waveguides are arranged on the optical path of the reflected light of the first and third spot images. When the lights propagating through the respective single mode waveguides are combined in the branch region, they interfere with each other. For one of the first and third light spots, the optical path length from the object to be detected to the combining portion of the second detection optical system, and for the other light spot, The difference ΔL from the optical path length from the object to be detected to the combining part of the second detection optical system is ΔL = mλ (m = 0, 1, 2, ...) (8) where λ is the wavelength of the laser light source. In this case, the intensity of light that is combined and interfered in the branching region is maximum. When the optical path difference ΔL does not satisfy the expression (8), the intensity of the light that is combined and interfered in the branching region is weaker than when the optical path difference satisfies the expression (8). That is, when the phase difference Δφ of the light propagating through the two single mode waveguides is Δφ = 2mπ (m = 0,1,2, ...) (9), the light that has been combined and interfered in the branching region Intensity becomes maximum, while on the other hand, when Δφ = (2m + 1) π / 2 (m = 0,1,2, ...) (10), the intensity of light that is combined and interfered in the branching region is Δφ
Is half the intensity when the expression (9) is satisfied.

When there is a difference in height due to a step on the surface of the object to be inspected in a portion where two light spots of the object to be inspected are formed, an optical path difference of 2d occurs when the height difference is d.
When the expression (10) is satisfied, the phase difference Δφ between the two single mode waveguides immediately before the branching region is caused by the difference in the optical paths.
1 becomes Δφ1 = 4πd / λ + (2m + 1) π / 2 (m = 0, 1, 2, ...) (11).

When the light quantity when the object surface is a flat surface and the expression (9) is satisfied is P _I , the light quantity P ₀ when there is a step and the expression (11) is satisfied is P ₀ = P _I sin ² (Δφ 1 / 2) (12) is given. Therefore, the third detecting means of the second detecting optical system detects the light amount P ₀ emitted from the second waveguide portion and substitutes it into the equation (11) to obtain the height difference d.
Can be obtained quantitatively. Further, which of the measured steps is higher and which is lower can be obtained from the sign of the difference signal obtained when the differential image of the phase information is obtained.

When the substrate of the second waveguide of the second detection optical system has the electro-optical effect, the electrode arranged between the waveguide entrance end and the branch region of one of the single mode waveguides. By applying a voltage to this region via, it is possible to change the phase of the light propagating in the waveguide. Even when the above-mentioned optical path difference ΔL does not satisfy the expression (8), by changing the voltage, 2
The phase difference Δφ of the light propagating through the two single mode waveguides can be adjusted so as to satisfy the expression (9).

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A confocal laser scanning differential interference microscope according to an embodiment of the present invention will be described with reference to FIG.

The confocal laser scanning differential interference microscope of the present embodiment has a semiconductor laser light source 1 as shown in FIG.
Collimator lens 2, diffraction grating 3, half mirror 4
And an objective lens 6 are sequentially arranged on the optical path to provide an illumination optical system. The illumination optical system irradiates the test object 7 with three light spots 8, 9, and 10. Further, between the half mirror 4 and the objective lens 6, three light spots 8,
An XY scanning device 5 for moving 9, 10 relative to the object to be inspected is arranged.

Further, on the optical path of the reflected light from the object 7 to be inspected, a condenser lens 11 and a substrate 12 in which a waveguide is formed and having an electro-optical effect are arranged. The substrate 12 has a double mode waveguide 14 having an incident end on the optical path of the reflected light of the light spot 9, a branch portion 21 for splitting the light propagating through the double mode waveguide 14 into two, and a branch portion. Two waveguide waves 25 and 28 that respectively guide and emit the two lights branched at 21 are continuously formed. Further, a pair of electrodes 17 is formed on the double mode waveguide 14. A power source (not shown) is connected to the electrode 17.

The substrate 12 is further provided with two single mode waveguides 13 and 15 each having an incident end on the optical path of the reflected light of the two light spots 8 and 10 on both sides.
A branching section 18 for branching the single mode waveguide section 13 into two single mode waveguides 19 and 20, and a single mode waveguide section 15 for two single mode waveguides 2.
A branching section 23 that branches into two and 24, a combining section 27 for combining the light that has propagated through the two single-mode waveguides 20 and 22, and the combined light of the combining section 27 is guided. One single-mode waveguide 26 that emits as a single light is continuously formed. Further, a pair of electrodes 16 is formed on the single mode waveguide 13. A power source (not shown) is connected to the electrode 16.

Photodetectors 30 and 32 are arranged at the exit ends of the waveguides 25 and 26, respectively. Further, the photodetectors 30 and 32 are provided with a differential circuit 34 that obtains a difference between the signals detected by the photodetectors 30 and 32. Differential circuit 3
4 obtains the inclination of the area of the object to be inspected 7 irradiated with the light spot 9.

A photodetector 31 is arranged at the exit end of the waveguide 27. The output of the photodetector 31 is the area where the light spot 8 is irradiated on the object to be inspected and the light spot 10.
The height difference between the illuminated area and the area. Photodetectors 29 and 33 are arranged at the exit ends of the waveguides 19 and 24, respectively. The outputs of the photodetectors 29 and 33 are used for alignment. A control device 36 is connected to the differential circuit 34, the photodetector 31, and the photodetectors 29 and 33. A monitor 37 is connected to the control device 36.

In this embodiment, the substrate 12 is x-cut,
z-propagating LiNbO ₃ is used, and the waveguide is Ti-diffused Li
It is formed in a channel shape with NbO ₃ . In the branch portion 21, the angle formed by the waveguide 25 and the waveguide 28 is
It was set to 1/100 rad. Furthermore, the angle at which the waveguide 20 intersects the waveguide 25, and the waveguide 22 is the waveguide 28.
The angle intersecting with was set to a sufficiently large angle so that crosstalk did not occur.

Next, the operation of the confocal laser scanning differential interference microscope of this embodiment will be described. The light emitted from the semiconductor laser light source 1 is collimated by the lens 2, and the diffraction grating 3 generates 0th-order, 1st-order, and -1st-order diffracted light, and is divided into three light fluxes. Is reflected by the laser beam, passes through the well-known XY two-dimensional scanning means 5, enters the objective lens 6, and is condensed on the object plane 7 as three light spots 8, 9, 10. Light spots 8 and 1
0 is for measuring the height difference of the step, and the light spot 9 is for differential interference. The light reflected by the object plane 7 and then transmitted again through the objective lens 6 and the XY scanning means 5 and then through the half mirror 4 is a double mode waveguide formed on the substrate 12 having the electro-optical effect by the lens 11. 14 and the single mode waveguides 13 and 15 are focused as three spots on the detection surface on which the incident end faces are arranged.

The reflected light from the light spot 8 on the object plane 7 enters the single mode waveguide 15. The reflected light from the light spot 9 enters the double mode waveguide 14, and the reflected light from the light spot 10 enters the single mode waveguide 13.

The double mode waveguide 14 has an electrode 17 on the substrate. The light propagating through the double mode waveguide 14 eventually reaches the branching portion 21 and the two channel waveguides 2
The power is distributed to 5, 28 and reaches two photodetectors 30, 32 bonded to the substrate 12. The waveguide 25 intersects the single-mode waveguide 20 and the waveguide 28 intersects the single-mode waveguide 22, but at a sufficiently large angle so that there is no crosstalk. Since the incident end of the single mode waveguide 14 functions like a pinhole, this structure constitutes a confocal laser scanning microscope. Here, the half mirror 4 and the objective lens 6 form an illumination optical system, and the objective lenses 6 and 11 form a condensing optical system.

The single-mode waveguide 13 is a single-mode waveguide in which an electrode 16 is arranged on a substrate, and the light propagating in the single-mode waveguide 13 eventually reaches a branching portion 18 and two single-mode waveguides 19 are provided. , 20 are distributed. The light propagating through the single mode waveguide 19 reaches the photodetector 29 joined to the substrate 12. The light propagating through the single mode waveguide 20 reaches the multiplexing unit 27,
The light that propagates through the single-mode waveguide 22 undergoes multiplexing interference,
The light propagating through the single mode waveguide 26 reaches the photodetector 31 joined to the substrate 12.

Similarly, the light propagating through the single mode waveguide 15 eventually reaches the branch portion 23, and the power is distributed to the two single mode waveguides 22 and 24. The light propagating through the single mode waveguide 24 reaches the photodetector 33 joined to the substrate 12. The light propagating through the single mode waveguide 22 reaches the multiplexing unit 27, and the single mode waveguide 2
The single mode waveguide 2
The light propagated through 6 reaches the photodetector 31 joined to the substrate 12.

As described above, when the area on the object 7 illuminated by the light spot 9 is tilted, the phase distribution of the light spot imaged at the incident end of the single mode waveguide 14 is tilted. Due to this inclination, the double mode waveguide 14
Both even and odd modes are excited inside, and the ratio of the optical power reaching the two detectors 30 and 32 changes due to the interference of both modes. The differential circuit 34 detects the inclination of a minute step or the like on the surface of the object 7 by obtaining the differential signals of the outputs of the two detectors 30 and 32.

Further, since the substrate 12 has an electro-optical effect, the complete coupling length Lc can be changed by changing the voltage applied to the electrode 17. Electrode 1
In Fig. 7, the length L of the double mode region at the time of setting the optical system is L = Lc (2m + 1) / 2 (m = 0,1,2, ...) (13), where Lc is the complete bond length. So that the voltage is adjusted and applied.

Since the substrate 12 has an electro-optical effect, the phase of light propagating through the single mode waveguide 20 can be changed by changing the voltage applied to the electrode 16. In the present embodiment, when setting the optical system, a flat surface having no steps is used as the object surface 7 to set the electrode 16
The phase difference Δφ between the light propagating in the single mode waveguide 20 and the light propagating in the single mode waveguide 22 is Δφ = (2m + 1) π / 2 (m = 0, 1, 2, ...・ ・) (10) At this time, the intensity of light of the photodetector 31 due to interference is such that the phase difference Δφ between the light propagating in the single mode waveguide 20 and the light propagating in the single mode waveguide 22 is Δφ = 2mπ (m = 0, 1, 2, , ...) It is half the amount of light when (9).

When the object surface 7 having a step as shown in FIG. 1 is measured, the light spot 8 and the single mode waveguide 15 are measured.
There is a difference between the optical path length between the incident ends of the light spot 10 and the incident end of the single mode waveguide 13, which is twice the height difference of the step. As described above, the amount P ₀ of light received by the photodetector 31 is equal to
Then, the phase difference Δφ is Δφ = 2mπ (m = 0, 1, 2,
In the case of ...), the amount of light received by the photodetector 31 is P _I ,
When the wavelength of the light source is λ, P _O = P _I sin ² (2πd / λ + (2m + 1) π / 4) (m = 0, 1, 2, ...) (12) Therefore, the light quantity of the detector 31 The height difference d of the step is obtained from P _O. Which of the steps is higher and which is lower is determined by the sign of the differential signal 35.

When the light spots 8 and 10 are inclined due to the surface texture of the object plane 7, since the single mode waveguides 13 and 15 are single mode waveguides, the odd mode caused by the inclination of the object disappears. The height difference of the step can be obtained by averaging the inclinations in the light spot.

The control device 36 has a built-in storage device,
The differential signal 35, the photodetector 31, and the position of the light spot 9 on the object to be inspected 7 obtained from the XY two-dimensional scanning means 5 are stored in association with each other. Then, a differential interference contrast image is created from the operation signal 35 and the position of the light spot 9 and is displayed on the monitor 37. Regarding the height difference of the step, the height difference of the step is displayed by confirming the step position on the monitor 37 and reading the signal of the photodetector 31 stored in the storage device 36 corresponding to the beam position.

Next, on the substrate 12, the branch portions 18, 21,
23, multiplexing section 27, waveguides 13, 14, 15, 19, 2
A method of forming 0, 22, 24, 25, 26, 28 will be described. First, x-cut LiNb that becomes the clad
A 300 Å Ti film is formed on the O ₃ substrate 12 by RF sputtering. This Ti film is patterned into a shape of a waveguide having the branching portion and the combining portion by a lithography method. The propagation direction of the waveguide is z propagation. The patterned Ti film and the LiNbO ₃ substrate 12 are heat-treated at 1000 ° C. for 6 hours to convert Ti to LiNbO 3.
₃ Diffuse into the substrate 12 to form a core portion. In this embodiment, the width of the double mode waveguide 14 is 7 μm, and the widths of the other waveguides are 4 μm. Finally, the entrance end and the exit end are polished to complete. At this time, polishing is performed so that the length L of the double mode waveguide 14 satisfies the above-mentioned formula (13). However, as described above, in the present embodiment, by changing the voltage applied to the electrode 17, the complete coupling length Lc is changed so that the length L of the double mode waveguide 14 satisfies the expression (13). Can be adjusted to. Therefore, the double mode waveguide 1 at the time of polishing
The length L of 4 may be in a range that can be adjusted so as to satisfy Expression (13) by applying a voltage to the electrode 17.

Further, the length from the incident end of the single mode waveguide 13 to the combining portion 27 is calculated by the formula ((φ) of the light phase at the combining portion 27 in the standard object having no step when setting the optical system. 10) is satisfied. However, as described above, in this embodiment, the phase difference Δφ can be changed by changing the voltage applied to the electrode 16, and the adjustment can be performed so as to satisfy the expression (10).
Therefore, the length L of the single mode waveguide 13 at the time of polishing can be calculated by applying the voltage to the electrode 17 by the formula (10).
Any range that can be adjusted to satisfy

As described above, the confocal laser scanning differential interference microscope of the embodiment is based on the new principle of using a waveguide, does not need to use complicated optical elements, has a small and simple structure, and can detect an object to be inspected. It is possible to quantitatively measure the differential interference image of the step and the height difference of the step.

Further, in this embodiment, since the substrate 12 having the electro-optical effect is used, it is possible to adjust by applying voltage so as to satisfy the conditional expressions (10) and (13) necessary for detection. Therefore, it is possible to easily allow an error in the waveguide length and a positional shift when setting the optical system by applying a voltage. Therefore, the substrate 1 having the waveguide
Since the allowable range of the waveguide length of 2 and the positional deviation at the time of setting the optical system can be widened, it is possible to manufacture at a high yield and at a low cost.

In the configuration of each of the above embodiments, another example of a suitable material for forming the channel waveguide is as follows:
It shows in Table 1. As a clad substrate for the waveguide, for example, S
i, soda glass, Pyrex, and fused quartz can be used. Although these do not have an electro-optical effect, the length of the waveguide and the alignment of the optical system are precisely adjusted so as to satisfy the conditional expressions (10) and (13) necessary for detection, and this embodiment is described below. Can be used for. Also,
LiTaO ₃ , GaAs, InP and the like can be used as the material having an electro-optical effect (indicated by * in Table 1). By forming electrodes based on these electro-optical effects, it is possible to change the complete coupling length L _C of the double mode waveguide 14 and the phase difference Δφ in the multiplexing section 27. For GaAs and InP,
It is also possible to monolithically integrate the laser diode LD and the light detection element of the light source 1. When Si is used for the substrate, the light receiving element can be integrated.
Therefore, although the laser light source and the photodetector are external to the waveguide device in the above-mentioned embodiment, the photodetector is on the same substrate as the waveguide device by using a compound semiconductor substrate such as gallium arsenide. It is possible to further reduce the size and weight of the device and save labor for adjustment. However, when it is difficult to configure the laser light source and the photodetector integrally with the waveguide, these may be arranged separately and the light may be guided by an optical fiber or a lens system. Further, the double mode waveguide can be replaced by two single mode waveguides arranged close to each other. Including these, the materials of the substrate and the waveguide layer for forming the channel waveguide that can be used in the present invention can be arranged as shown in Table 1, and appropriate materials can be selected based on the characteristics of each material. It is preferable to use.

[0049]

[Table 1]

By the way, in the above-mentioned embodiment, the objective lens is shared by the illumination optical system and the condensing optical system, and a so-called epi-illumination type microscope is constructed. It goes without saying that the illumination optical system may be arranged on one side and the condensing optical system may be arranged on the other side to form a so-called transmission microscope.

Needless to say, images having various contrasts can be obtained by applying appropriate processing to the signals obtained by processing the two differential signals from the photodetector.

In each of the embodiments, the light spot is scanned on the test object by an XY two-dimensional scanner such as a vibrating mirror or a rotating mirror as a means for moving the test object and the light spot relative to each other. Although the configuration is adopted, conversely, it is possible to fix the light spot and scan the stage on which the object to be inspected is placed. When a light beam in the optical system is oscillated by a vibrating mirror or rotating mirror to scan the light spot, the light spot on the object to be inspected and the incident end of the waveguide are condensed due to the influence of residual aberration of the optical system. There is a possibility that the conjugate relationship with the optical spot to be scanned cannot be strictly maintained. In such a case, it is desirable to scan the stage.

In the above embodiment, the electrode 17 for applying a voltage to the double mode waveguide 14 is provided in the waveguide 1.
The electrode 16 for applying a voltage to the single-mode waveguide 13 is arranged symmetrically with respect to the waveguide 4, and the electrode 16 for applying a voltage to the single mode waveguide 13 is arranged symmetrically with respect to the waveguide 13. It is also possible to use a three-electrode arrangement, depending on the crystallographic axis direction, etc.

Further, in this embodiment, the waveguides 14, 25, 28 for obtaining differential information and the waveguides 13, 15, 22, 2, 2 for obtaining quantitative information on the height difference of the step.
Although 0 and 27 are arranged on the same substrate, they are not limited to this shape and can be arranged on different substrates as a matter of course.

In the present embodiment, the single mode waveguides 13 and 15 are branched into two and the outputs of the single mode waveguides 19 and 24 are used for alignment. However, the single mode waveguide 19 for alignment is used. , 24
If the output of is not required, single mode waveguide 1
It is not necessary to branch 3, 15 into two.

[0056]

As described above, according to the present invention, a special objective lens and a special optical element such as a Nomarski prism or a wave plate are not necessary, and a compact and simple structure based on a new principle using a waveguide is provided. However, it is possible to provide a confocal laser scanning differential interference microscope capable of simultaneously performing differential information on the step of the object to be inspected and quantitatively measuring the height difference of the step.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a configuration of a confocal laser scanning differential interference microscope according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a configuration of a conventional confocal laser scanning differential interference microscope.

[Explanation of symbols]

1 ... Laser light source, 5 ... XY scanning device, 14 ...
Double mode waveguide, 13, 15, 19, 20, 22,
24, 26 ... Single mode waveguide, 25, 28 ... Waveguide, 29, 30, 31, 32, 33 ... Photodetector, 16,
17 ... Electrode, 34 ... Differential circuit, 36 ... Control device, 37 ...
monitor.

Claims (6)

[Claims] 1. An illumination optical system for irradiating a light spot on a test object, scanning means for moving the light spot relative to the test object, and the test object for the light spot. A confocal laser scanning differential interference microscope having a detection optical system for detecting reflected light from the illumination optical system, wherein the illumination optical system is arranged on the object to be inspected first, second, and third. The detection optical system irradiates three light spots, and the detection optical system obtains differential information of a region irradiated with the second light spot of the object to be inspected from the reflected light of the second light spot among the three light spots. From the first detection optical system to obtain and the reflected light of the first and third light spots of the three light spots, between the regions irradiated with the first and third light spots of the test object. And a second detection optical system for obtaining a height difference, First detection optical system includes a double-mode waveguide section having an entrance end on the optical path of the reflected light of the second light spot,
A branching part for branching the light propagating through the double mode waveguide part into two parts, and two waveguide parts for respectively guiding and emitting the two lights branched by the branching part are provided. A first waveguide optical system, and first and second detecting means respectively arranged at the emission ends of the two waveguide portions of the first waveguide optical system to detect the intensity of emitted light, A difference calculating means for obtaining a difference between the detection signal of the first detecting means and the detection signal of the second detecting means, wherein the second detecting optical system has two light spots of the first and third light spots. Two single mode waveguide sections each having an incident end on the optical path of the reflected light, and a combining section for combining the lights propagating through the two single mode waveguide sections,
A second waveguide optical system including one single-mode waveguide portion that guides and emits the combined light of the combining portion;
A third waveguide arranged at the emission end of one single-mode waveguide portion of the second waveguide optical system to detect the intensity of emitted light;
And a confocal laser scanning differential interference microscope. 2. The length L of the double mode waveguide portion of the first detection optical system according to claim 1, wherein a complete coupling length Lc of even / odd modes guided through the double mode waveguide portion is Lc.
L = Lc (2m + 1) / 2 (m = 0, 1, 2, ...
..) A confocal laser scanning differential interference microscope having a length represented by: 3. The one of the first and third light spots as claimed in claim 1, when the first and third light spots illuminate an object to be inspected having a flat surface having no height difference. The optical path length from the object to be detected to the combining portion of the second detection optical system for the light spot of the above, and the combination of the second detection optical system from the object to be detected for the other light spot. The difference ΔL with the optical path length to the wave portion is represented by ΔL = mλ (m = 0, 1, 2, ...) Using the wavelength λ of the light emitted by the illumination optical system. A confocal laser scanning differential interference contrast microscope. 4. The double mode waveguide portion of the first detection optical system according to claim 2, wherein the double mode waveguide portion is made of a material having an electro-optical effect, and the complete coupling length Lc of the double mode waveguide portion is changed. Therefore, a confocal laser scanning differential interference microscope having an electrode for applying a voltage to the double mode waveguide. 5. The electro-optical device according to claim 3, wherein at least one of the two single-mode waveguide portions of the second detection optical system is made of a material having an electro-optical effect. In order to change the phase of light in the single mode waveguide part made of a material having an effect, an electrode for applying a voltage to the single mode waveguide part made of the material having an electro-optical effect is provided. A confocal laser scanning differential interference contrast microscope. 6. The optical waveguide system according to claim 1, wherein the first optical waveguide system and the second optical waveguide system are channel type waveguides formed on the same substrate. Confocal laser scanning differential interference microscope.