JPH05172736A - Sample surface or inside information detecting method and device thereof - Google Patents

Abstract

(57) [Abstract] [Object] The present invention relates to a photoacoustic signal detection technique, and has a simple structure and is capable of high-speed detection of two-dimensional internal information of a sample, which is hardly affected by reflectance distribution and unevenness distribution of the sample surface. An object of the present invention is to provide a method for detecting the surface or internal information of a sample and an apparatus for the same. [Structure] A structure 201 in which a strip-shaped inspection region of a sample is simultaneously excited in parallel by a stripe-shaped excitation beam 101, optical interference is used to detect a photoacoustic signal generated at each point, and interference light is simultaneously detected in parallel. , 202, the photoacoustic signals in the strip inspection region of the sample can be simultaneously detected in parallel, and the above object can be achieved. [Effect] Since the photoacoustic signals in the strip inspection region of the sample can be simultaneously detected in parallel, the two-dimensional surface of the sample and internal information can be detected at high speed. In addition, it is possible to detect the photoacoustic signal in which the reflectance distribution, the unevenness distribution, and the fluctuation of the optical path on the sample surface are corrected, and it is possible to perform highly sensitive and stable detection.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sample surface or internal information detecting method and apparatus for detecting two-dimensional internal information on the surface or inside of a sample by utilizing a photoacoustic effect.

[0002]

[Prior Art] Photoacoustic Effect
1881 Tyndall, Bell,
Discovered by Rentogen et al. That is,
As shown in FIG. 30, when the intensity-modulated light (intermittent light) 19 is used as excitation light and is focused on the sample 7 by the lens 5 and irradiated, heat is generated in the light absorption region V _op 21 and the thermal diffusion length. This is a phenomenon in which a thermal diffusion region V _th 23 given by μ _s 22 is diffused periodically, and an elastic wave (ultrasonic wave) is generated by this thermal strain wave. The ultrasonic wave, that is, the photoacoustic signal is detected by using a microphone (acoustoelectric converter), a piezoelectric element, or an optical interferometer, and a signal component synchronized with the modulation frequency of the excitation light is obtained to obtain the surface and the inside of the sample. You can get information. Note that the thermal diffusion length μ _s 22 is the thermal conductivity k of the sample 7, the density ρ, and the modulation frequency of the excitation light is f _L.
And the specific heat c are given by the following equation (Equation 1).

[0003]

[Equation 1]

Regarding the above-mentioned photoacoustic signal detection method, for example, reference is made to "Non-destructive inspection; Vol. 36, No. 10, p. 73".
0-p. 736 (October 1987) "and" I-E-E 1986 Ultra Sonics Symposium; pp. 515-526 (1986) (IEEE 1
986ULTRA-SONICS SYMPOSIU
M; p. 515-526 (1986) ".

An example thereof will be described with reference to FIG. The collimated light emitted from the laser 1 is intensity-modulated by an acousto-optic modulator (AO modulator) 2, and the intermittent light, that is, excitation light, is collimated by a beam expander 3 into a collimated light 1 having a desired beam diameter.
After setting to 9, the light is reflected by the half mirror 4 and is focused on the surface of the sample 7 on the XY stage 6 by the lens 5. An ultrasonic wave is generated by the thermal strain wave generated from the light condensing part 21 on the sample 7, and at the same time, a minute displacement is generated on the surface of the sample 7. This minute displacement is detected by the Michelson interferometer described below. After the parallel light emitted from the laser 8 is expanded to a desired beam diameter by the beam expander 9, it is split into two optical paths by the half mirror 10, and one of them is used as the probe light 24 by the lens 5
The light is focused on the light collecting portion 21 on the sample 7 by. The other side irradiates the reference mirror 11. The reflected light from the sample 7 and the reflected light from the reference mirror 11 interfere with each other on the half mirror 10, and the interference light is condensed by a lens 12 on a photoelectric conversion element 13 such as a photodiode. The photoelectrically converted interference intensity signal is amplified by the preamplifier 14,
It is sent to the lock-in amplifier 16. Lock-in amplifier 1
6, the oscillator 15 used to drive the acousto-optic modulator 2
Only the modulation frequency component contained in the interference intensity signal is extracted using the modulation frequency signal from the reference signal as the reference signal. This frequency component has information on the surface or inside of the sample 7 according to the frequency. From Equation 1, the thermal diffusion length μ _s 21 can be changed by changing the modulation frequency, and information in the depth direction of the sample can be obtained. If there is a crack or other defect in the thermal diffusion region V _th 23, the amplitude of the modulation frequency component in the interference intensity signal and the phase with respect to the modulation frequency signal change, so the presence thereof can be known. The XY stage movement signal and the output signal from the lock-in amplifier 16 are processed by the computer 17, and the photoacoustic signal at each point on the sample is output to the display 18 such as a monitor television as two-dimensional image information.

[0006]

The above-mentioned prior art is an extremely effective means for detecting a photoacoustic signal in a non-contact and non-destructive manner, but has the following problems.

That is, in the conventional photoacoustic detection optical system shown in FIG. 29, when the two-dimensional internal information of the sample is to be obtained, the excitation light for generating the photoacoustic effect and the sample generated by the photoacoustic effect are used. It is necessary to two-dimensionally scan the sample relatively with the probe light for detecting the minute displacement of the surface. Since this two-dimensional scanning is so-called point scanning in which information is detected point by point, it takes an enormous amount of detection time to scan the entire surface of the sample.
The fact that this enormous detection time is required is the largest reason that the photoacoustic detection technology has not been applicable to the internal defect inspection of the sample in the production line so far. In addition, the reflectance of the surface may vary depending on the location depending on the sample. In that case, in the conventional technique, the reflected light intensity of the probe light includes not only the internal information but also the surface reflectance information, and it is difficult to accurately detect only the internal information. Further, depending on the sample, the surface shape may not be flat and may be uneven depending on the location. In that case, in the conventional technique, the phase of the reflected light of the probe light changes due to the unevenness of the sample surface, and includes not only the internal information but also the unevenness information of the surface, and it is difficult to accurately detect only the internal information. There was a problem that there is.

The object of the present invention is to have a simple structure and to be hardly affected by the reflectance distribution and unevenness distribution on the sample surface,
It is an object of the present invention to provide a method or apparatus for detecting the surface or internal information of a sample, which enables high-speed detection of two-dimensional internal information on the surface or inside.

[0009]

In order to achieve the above object, the present invention is directed to irradiating the surface of a strip-shaped inspection region of a sample with light whose intensity is modulated at a desired frequency, and irradiating the surface or the inside of the strip-shaped inspection region. To generate photoacoustic effect or photothermal effect,
By irradiating the surface of the strip-shaped inspection area of the sample with light, the interference light between the reflected light and the reference light is detected by the photoelectric conversion element having a conjugate relationship with the sample surface, and from the detected interference light intensity signal, Detecting the thermal strain of the same frequency component as the intensity modulation frequency caused by the photoacoustic effect or the photothermal effect in the strip inspection region, and detecting the surface or internal information of the strip inspection region of the sample from the thermal strain of the frequency component. It is characterized by.

Further, in order to achieve the above object, the present invention shapes two-dimensional internal defects on a sample by shaping and irradiating the intensity-modulated light for irradiating the sample with a shape covering a strip inspection region. It is possible to detect.

Further, in order to achieve the above object, according to the present invention, a plurality of measurement points on the sample are provided by making the intensity-modulated light with which the sample is irradiated into a beam having a continuous linear shape on the sample. It is possible to excite at the same time, and it is possible to detect photoacoustic signals much faster than the conventional method.

In order to achieve the above object, the present invention provides a plurality of measurement points on the sample by forming the intensity-modulated light with which the sample is irradiated into a spot beam array linearly arranged on the sample. It is possible to excite simultaneously, and it is possible to detect photoacoustic signals much faster than the conventional method.

In order to achieve the above object, the present invention improves the detection resolution of photoacoustic images by setting the intervals of the spot beam arrays so that the thermal diffusion regions of the spot beams do not overlap. It is a thing.

Further, in order to achieve the above object, the present invention uses a detector composed of a plurality of storage type photoelectric conversion elements to detect interference light, so that the optical speed is significantly higher than that of the conventional system. This makes it possible to detect acoustic signals.

Further, in order to achieve the above object, the present invention uses a detector composed of a plurality of non-accumulation type photoelectric conversion elements to detect interference light, and thus is much faster than the conventional method. This makes it possible to detect photoacoustic signals.

In order to achieve the above object, the present invention uses a detector in which an interference light intensity signal is output as a one-dimensional signal in time series from a plurality of photoelectric conversion elements. This makes it possible to detect photoacoustic signals at a significantly higher speed.

In order to achieve the above object, the present invention uses a detector in which an interference light intensity signal is simultaneously output in parallel from a plurality of photoelectric conversion elements, and thus is significantly faster than the conventional method. It is possible to detect various photoacoustic signals.

In order to achieve the above object, the present invention uses a detector composed of a plurality of storage type photoelectric conversion elements for detecting interference light, and each storage type photoelectric conversion element of the detector is used. Signals are detected 2n times while shifting the phase of the interference light intensity signal accumulated and output within a desired accumulation time by π / n, and the same frequency component as the intensity modulation frequency is detected based on the 2n pieces of signal data. By calculating the thermal strain of, it is possible to use digital processing instead of analog frequency filtering processing. As a result, it is possible to detect photoacoustic signals with high sensitivity and high accuracy, with less influence of harmonic components. It was done. In addition, the reflectance distribution of the sample surface, the unevenness distribution of the sample surface, the amplitude distribution of the photoacoustic signal, and the phase distribution of the photoacoustic signal, and a total of four surfaces and internal information can be detected simultaneously with only one detector. This makes it possible to perform high-speed composite evaluation of samples. In addition, it is possible to detect photoacoustic signals with the reflectance distribution of the sample surface, the unevenness distribution of the sample surface, and the fluctuation of the optical path corrected, and to enable highly sensitive and stable detection of the sample surface and internal information. is there.

In order to achieve the above object, the present invention provides a method for shifting the phase of an interference light intensity signal output from a detector comprising a storage type photoelectric conversion element by π / n from the sample surface. Of the optical frequency difference between the reflected light and the reference light, the intensity modulation frequency, and the storage time of the storage type photoelectric conversion element are combined into desired values, respectively, so that only one detection is performed. With the instrument, it is possible to simultaneously detect the reflectance distribution of the sample surface, the unevenness distribution of the sample surface, the amplitude distribution of the photoacoustic signal, and the phase distribution of the photoacoustic signal, and a total of four surfaces and internal information. It enables various complex evaluations. In addition, it is possible to detect photoacoustic signals with the reflectance distribution of the sample surface, the unevenness distribution of the sample surface, and the fluctuation of the optical path corrected, and to enable highly sensitive and stable detection of the sample surface and internal information. is there.

In order to achieve the above object, the present invention provides a plurality of photoelectric conversions of the thermal distortion of the same frequency component as the intensity modulation frequency from the interference light intensity signals simultaneously output in parallel from the detector. By detecting elements in parallel at the same time, it is possible to detect photoacoustic signals at a much higher speed than the conventional method.

In order to achieve the above object, the present invention sets the intensity modulation frequency such that the thermal diffusion length based on the photoacoustic effect or the photothermal effect is the same as the depth of the measured internal interface of the sample, or The internal interface can be inspected by setting the length to exceed.

[0022]

In the photoacoustic signal detection device, the surface of the band-shaped inspection region of the sample is irradiated with light whose intensity is modulated to generate a photoacoustic effect or a photothermal effect on or in the band-shaped inspection region. At the same time, the surface of the band-shaped inspection area of the sample is irradiated with light, and the interference light between the reflected light and the reference light is detected by the photoelectric conversion element having a conjugate relationship with the sample surface, and the detected interference light intensity The surface or internal information of the strip inspection region of the sample is detected from the thermal strain of the frequency component detected from the signal by detecting the thermal strain of the same frequency component as the intensity modulation frequency caused by the photoacoustic effect or the photothermal effect in the strip inspection region. Can be detected, and the photoacoustic signal can be detected much faster than the conventional method.

Further, by making the intensity-modulated light with which the sample is irradiated into a beam having a continuous linear shape on the sample,
It becomes possible to excite the band-shaped inspection region on the sample at the same time, and it becomes possible to detect a photoacoustic signal at a much higher speed than the conventional method.

Further, by making the intensity-modulated light with which the sample is irradiated into a spot beam array linearly arranged on the sample, it becomes possible to simultaneously excite the strip-shaped inspection region on the sample, which is more than the conventional method. It is possible to detect photoacoustic signals at a significantly high speed.

Further, by making the intervals of the spot beam rows such that the thermal diffusion regions by the spot beams do not overlap, the photoacoustic signals in the strip inspection regions can be independently detected, and the photoacoustic image can be detected. The detection resolution of is improved.

Further, by using a detector composed of a plurality of storage type photoelectric conversion elements for detecting the interference light,
It is possible to extract the photoacoustic signals in the strip inspection region almost at the same time, and it becomes possible to detect the photoacoustic signals at a much higher speed than the conventional method.

Further, by using a detector composed of a plurality of non-accumulation type photoelectric conversion elements for detecting the interference light, it becomes possible to extract the photoacoustic signals in the strip inspection region almost at the same time. In comparison, it is possible to detect photoacoustic signals at a significantly higher speed.

Further, by using a detector in which the interference light intensity signal is output as a one-dimensional signal in a time series from a plurality of photoelectric conversion elements, it is possible to extract photoacoustic signals in the strip inspection region almost at the same time. Therefore, the photoacoustic signal can be detected at a much higher speed than the conventional method.

Further, by using a detector in which the interference light intensity signal is simultaneously output in parallel from a plurality of photoelectric conversion elements, it becomes possible to extract the photoacoustic signals in the strip inspection region almost at the same time. It is possible to detect photoacoustic signals at a much higher speed than the above.

Further, a detector comprising a plurality of storage type photoelectric conversion elements is used to detect the interference light, and each storage type photoelectric conversion element of the detector is stored and output within a desired storage time. The signal is detected 2n times while shifting the phase of the interference light intensity signal by π / n, and the thermal distortion of the same frequency component as the intensity modulation frequency is calculated based on the 2n pieces of signal data. It is possible to use digital processing instead of frequency filtering processing, and as a result, it is possible to detect photoacoustic signals with high sensitivity and accuracy, with less influence of harmonic components. Also only 1
With each detector, it becomes possible to simultaneously detect the reflectance distribution of the sample surface, the unevenness distribution of the sample surface, the amplitude distribution of the photoacoustic signal, and the phase distribution of the photoacoustic signal, and a total of four surfaces and internal information, High-speed composite evaluation of samples is possible. Further, it becomes possible to detect a photoacoustic signal in which the reflectance distribution of the sample surface, the unevenness distribution of the sample surface, and the fluctuation of the optical path are corrected, and it is possible to detect the surface of the sample and internal information with high sensitivity and stability.

As a method of shifting the phase of the interference light intensity signal output from the detector composed of the accumulation type photoelectric conversion element by π / n, the optical frequency between the reflected light from the sample surface and the reference light is used. Difference, the intensity modulation frequency, and the storage time of the storage-type photoelectric conversion element are combined into desired values, so that the reflectance distribution of the sample surface and the sample surface can be measured by only one detector. It is possible to simultaneously detect the unevenness distribution, the amplitude distribution of the photoacoustic signal, and the phase distribution of the photoacoustic signal, and a total of four surface and internal information, which enables high-speed composite evaluation of the sample. Further, it becomes possible to detect a photoacoustic signal in which the reflectance distribution of the sample surface, the unevenness distribution of the sample surface, and the fluctuation of the optical path are corrected, and it is possible to detect the surface of the sample and internal information with high sensitivity and stability.

Further, from the interference light intensity signals simultaneously output from the detectors in parallel, thermal distortion of the same frequency component as the intensity modulation frequency is simultaneously detected in parallel with respect to a plurality of photoelectric conversion elements. It is possible to detect photoacoustic signals at a much higher speed than the above.

Further, by setting the intensity modulation frequency so that the thermal diffusion length based on the photoacoustic effect or the photothermal effect is equal to or longer than the depth of the internal interface to be measured of the sample, Interface inspection is possible.

[0034]

EXAMPLE An example of the present invention will be described with reference to FIGS.

First, a first embodiment of the present invention will be described with reference to FIGS.
It will be described based on 2. FIG. 1 shows a photoacoustic detection optical system in the first embodiment. The optical system includes an excitation optical system 201, a heterodyne type Twyman-Green interference optical system 202 for detecting a photoacoustic signal, and a signal processing system 203. Ar laser 3 of excitation optical system 201
The parallel beam 32 emitted from 1 (wavelength 515 nm) enters the acousto-optic modulator 33. Now, in FIG. 1, the sine wave 98 of the frequency f _C0 shown in FIG.
From the oscillator 87 to the frequency f shown in FIG.
The rectangular wave 99 of _L (f _L <f _C0 ) is input to the signal combiner 88, and the product of both waveforms is taken to produce the modulated signal 100 shown in FIG. To do. As a result, the first-order diffracted light 35 frequency-shifted by f _C0 is intermittently output at the frequency f _L from the acousto-optic modulator 33. That is, as the excitation light, an intensity-modulated beam having a modulation frequency f _L that is frequency-shifted by f _C0 is obtained.
The 0th order light 34 is blocked by the diaphragm 36. After passing the intensity-modulated beam 35 through the beam splitter 37, it is expanded to a desired beam diameter by a beam expander 38, and is further converted into an elliptical beam 40 by a cylindrical lens (cylindrical lens) 39, and a dichroic prism 41 (wavelength 60
After reflection of 0 nm or less and transmission of 600 nm or more), x is applied to the pupil 43 of the objective lens 42, that is, the rear focal position 44.
Focus only in the direction. On the other hand, with respect to the y direction, the cylindrical lens 39 can be regarded as a plate glass having no curvature, so that the parallel light is incident on the rear focus position 44 of the objective lens as it is. As a result, as shown in FIG. 4, at the front focus position of the objective lens, that is, on the surface of the sample 47, one stripe beam 101 having a width in the x direction and focused in the y direction is obtained as an excitation beam. To be In the beam splitter 37, about 10% of the beam light 49 of the intensity-modulated beam 35 is reflected, detected by the photoelectric conversion element 50 such as a photodiode, and then passed through an amplifier circuit 89 and an oscillator 87.
Sent to. The oscillator 87 compares the set frequency f _L sent from the modulation signal control circuit 90 with the measurement frequency f _L X detected by the photoelectric conversion element 50, and finely adjusts the oscillation frequency so that they match. The oscillator 87 is a PLL (Pha
se Lock Loop) circuit and the like.

The excitation optical system 201 will be described in more detail with reference to FIG. In FIGS. 3A and 3B, the focal position of the cylindrical lens 39 and the rear focal position 44 of the objective lens 42 coincide, and the front focal position of the objective lens coincides with the surface of the sample 47. There is.
Therefore, as shown in FIG. 4A, the beam 40 emitted from the cylindrical lens 39 is focused at the rear focal position 44 of the objective lens 42 in the x direction, and thus the objective lens 4
The beam 46 emitted from No. 2 becomes parallel light and is incident on the surface of the sample 47. On the other hand, as shown in FIG. 7B, in the y direction, the cylindrical lens 39 can be regarded as a plate glass having no curvature, and therefore the beam 40 emitted from the cylindrical lens 39 is incident on the objective lens 42 as parallel light. Beam 46 emitted from the objective lens 42
Is focused on the surface of the sample 47. As a result, as shown in FIG. 4, on the surface of the sample 47, one stripe beam 101 having a width in the x direction and focused in the y direction is obtained as an excitation beam. Now, as a sample, as shown in FIG. 4, an organic polymer material 10 such as polyimide is used.
Cu wiring pattern 102 formed by using 4 as an insulator,
Consider 103. FIG. 5 is a cross-sectional view showing the internal structure of the sample and the thermal diffusion region generated by the excitation beam. The sample 47 has a structure in which a polyimide pattern 104 having a thickness of 20 μm is used as an insulator and Cu patterns 102 and 103 having a thickness of 20 μm are formed as a wiring pattern on a ceramic substrate 109. Internal crack 10 in Cu wiring pattern
7 and peeling 108 at the interface between the base substrate and the Cu pattern are internal defects to be detected. Here, the important point is the difference in thermal properties between the Cu patterns 102 and 103 and the polyimide 104 around them. That is, the thermal conductivity k of Cu is 403
[J · m- ¹ · k- ¹ · s- ¹ ] and the density ρ is 8.93 [× 10
⁶ g · m ~ ^3], the specific heat c whereas a 0.38 ^{[J · g ~ 1 · k ~} 1 ], the thermal conductivity k of the polyimide 0.288
[J · m- ¹ · k- ¹ · s- ¹ ], density ρ is 1.36 [× 10
⁶ g · m ~ ³ ], specific heat c is 1.13 [J · g ~ ¹ · k ~ ¹ ], and the thermal conductivity k of Cu is 14 times that of polyimide.
It is 00 times. Therefore, if the intensity modulation frequency f _L of the excitation light is set to 50 kHz and the above value is substituted into Equation 1, Cu
The thermal diffusion length μ _s in the pattern portions 102 and 103 is about 2
7 μm, the thermal diffusion length in the polyimide portion 104 is about 1.
It becomes 1 μm. As a result, as shown in FIG. 5, the heat applied in the stripe-shaped light absorption region 105 formed by the stripe-shaped excitation beam 101 is largely diffused in the Cu pattern portions 102 and 103 to be inspected, and The thermal diffusion region 106 is formed so as to cover the cross section of the Cu pattern including the interface with the substrate. On the other hand, in the polyimide portion 104 which is not the inspection target, heat is diffused in a small amount and the heat diffusion region is formed only on the surface portion. As a result, as shown in FIGS. 4 and 5, the stripe-shaped excitation beam 101
Is irradiated so as to cover the plurality of Cu wiring patterns 102 and 103, ultrasonic waves (thermoelastic waves) are generated along with the photoacoustic effect or photothermal effect along the light absorption region 105, and ultrasonic waves (thermoelastic waves) are generated. 47 Distribution of minute displacement on the surface 11
0 (broken line) is generated, and the internal information of the Cu wiring patterns 102 and 103 (internal crack 107, peeling defect 108) and the internal information of the polyimide portion 104 are fused into the distribution 110 of the minute displacement. Instead, it is reflected independently. That is, the striped excitation beam 1
If 01 is used, it is possible to simultaneously excite a plurality of inspection targets with high thermal contrast and to independently detect,
The two-dimensional internal information of the sample can be detected at high speed. Next, the configuration and function of the heterodyne type Twyman-Green interference optical system 202 for detecting the distribution 110 (broken line) of the minute displacement on the sample surface based on the photoacoustic effect will be described based on FIGS. 1 to 9. .. In FIG. 1, the deflection direction of the linearly polarized beam 52 emitted from the He-Ne laser 51 (wavelength 633 nm) is set to 45 ° with respect to the x-axis and the y-axis as indicated by 111 in FIG. 6A. Here, with respect to the plane of FIG.
The direction orthogonal to that is the x-axis. The polarization beam splitter 53 causes one of the incident light beams 52 shown in FIG.
The p-polarized component 54 indicated by 12 is the polarization beam splitter 53.
And is incident on the acousto-optic modulator 62. Further, the s-polarized component 55 indicated by 113 in FIG. 6A is reflected by the polarization beam splitter 53. From oscillator 91 to FIG.
A sine wave having a frequency f _C1 similar to that shown in ( ₁ ) is input to the acousto-optic modulator 62 to obtain p-polarized first-order diffracted light 64 frequency-shifted by f _C1 . The 0th order light 63 is blocked by the diaphragm 65. The p-polarized first-order diffracted light 64 is reflected by the mirror 66 and then passes through the polarization beam splitter 61. On the other hand, the s-polarized component 55 reflected by the polarization beam splitter 53 is reflected by the mirror 56, and then the acousto-optic modulator 5
It is incident on 7. A sine wave having a frequency f _C2 (f _C1 ≠ f _C2 ) similar to that shown in FIG. 2A is input to the acousto-optic modulator 57 from the oscillator 91, and the s-polarized wave 1 is frequency-shifted by f _C2.
The next-order diffracted light 59 is obtained. The 0th order light 58 is blocked by the diaphragm 60. The s-polarized first-order diffracted light 59 is reflected by the polarization beam splitter 61 and is combined with the p-polarized first-order diffracted light 64 that has passed through the polarization beam splitter 61. This combined light 67 forms two-frequency orthogonally polarized light, that is, light beams orthogonal to each other in the directions 112 and 113 and having a frequency difference of f _C1 -f _{C2 with} each other, as shown in FIG. 6B. After passing the combined light 67 through the beam splitter 68, it is expanded to a desired beam diameter by a beam expander 70, and is further converted into an elliptical beam by a cylindrical lens (cylindrical lens) 71. This elliptical beam is split into a p-polarized beam 72 and an s-polarized beam 74 by a polarizing beam splitter 73. The p-polarized beam 72 is frequency-shifted by f _C1 and, after passing through the dichroic prism 41, is condensed only in the x direction on the pupil 43 of the objective lens 42, that is, on the rear focal position 44. On the other hand, in the y direction, since the cylindrical lens 71 can be regarded as a plate glass having no curvature, the parallel light is incident on the rear focal position 44 of the objective lens 42 as it is. The beam emitted from the objective lens 42 is a λ / 4 plate 4
After passing five times, it becomes a circularly polarized beam 145, and as shown in FIG. 4, on the front focus position of the objective lens, that is, on the surface of the sample 47, at the same position as the excitation beam 101, there is a width in the x direction as a probe beam and y A striped beam 190 is obtained which is focused in the direction. As shown in FIG. 7, the reflected light from the sample 47 has the distribution 110 (broken line) of the minute displacement generated on the surface of the sample 47 due to the photoacoustic effect as the phase distribution information. In FIG. 1, the reflected light from the sample 47 becomes an s-polarized beam after passing through the λ / 4 plate 45, and after passing through the objective lens 42, is reflected by the polarizing beam splitter 73 through the same optical path again.

On the other hand, the s-polarized beam 74 separated by the polarization beam splitter 73 is frequency-shifted by f _C2 , becomes circularly polarized light after passing through the λ / 4 plate 75, and enters the reference mirror 76. The circularly polarized light beam reflected by the reference mirror 76 again becomes p-polarized light after passing through the λ / 4 plate 75, and passes through the polarizing beam splitter 73 as reference light. 114 of FIG.
Indicates the polarization direction of the reflected light from the sample 47 reflected by the polarization beam splitter 73, and 115 indicates the polarization direction of the reflected light from the reference mirror 76. Since they are orthogonal to each other, they do not interfere as they are. Therefore, by inserting a polarizing plate 79 after the imaging lens 78 and setting the polarization direction to the 45 ° direction as shown by 116 in FIG. 8, both reflected lights interfere and f _B = f _C1 -f _C2 The heterodyne interference light 80 having the beat frequency is obtained. The heterodyne interference light 80 contains, as optical phase distribution information, a one-dimensional distribution in the x direction of minute displacements generated on the surface of the sample 47 due to the photoacoustic effect. This interference light 80 has a center wavelength of 63
After removing stray light through the 3 nm interference filter 81,
An image is formed on a storage type solid-state image pickup device 82 such as a CCD one-dimensional sensor by an image forming lens 78. Since the image pickup surface of the CCD one-dimensional sensor 82 and the surface of the sample 47 are in an image-forming relationship, naturally, the stripe-shaped interference light is imaged on the image pickup surface like the probe beam formed on the surface of the sample 47. The beam splitter 68 reflects about 10% of the combined light 67 of the two-frequency orthogonally polarized light. Both polarization components of this light beam interfere with each other by the polarizing plate 83 whose polarization direction is 45 ° as shown by 116 in FIG. 8, and the beat signal of f _B X = f _C1 X−f _C2 X is generated by a photodiode or the like. Is detected by the photoelectric conversion element 85. This beat signal is sent to the CCD one-dimensional sensor drive control circuit 93 via the amplifier circuit 92. In the drive control circuit 93, the set beat frequency f _B sent from the computer 96 is compared with the measurement frequency f _B X detected by the photoelectric conversion element 85, and the computer 96 and the modulation signal control circuit 90 are compared so that they match each other. Through
The frequency f _C1 or f _C2 of the sine wave output from the oscillator 91 is finely adjusted. The oscillator 91 is a PLL (Phase).
LockLoop) circuit and the like.

The heterodyne type Twyman-Green interference optical system 202 will be described in more detail with reference to FIGS. 3 and 9. As shown in FIGS. 3A and 3B, similarly to the excitation optical system 201, the focal position of the cylindrical lens 71 and the rear focal position 44 of the objective lens 42 coincide with each other, and the front focal point of the objective lens is the same. The position coincides with the surface of the sample 47. Therefore, as shown in FIG.
Regarding the direction, the p-polarized beam 72 emitted from the cylindrical lens 71 is focused on the rear focal position 44 of the objective lens 42, so that the beam 145 emitted from the objective lens 42 becomes parallel light and is incident on the surface of the sample 47. That is why. On the other hand, as shown in FIG. 6B, in the y direction, the cylindrical lens 71 can be regarded as a plate glass having no curvature, so that the beam 72 emitted from the cylindrical lens 71 is incident on the objective lens 42 as parallel light. The beam 145 emitted from the objective lens 42 is condensed on the surface of the sample 47. As a result, as shown in FIG.
7 has a width in the x direction as a probe beam at the same position as the excitation beam 101 on the surface of y and has a width of y.
A striped beam 190 is obtained which is focused in the direction. On the other hand, as shown in FIGS. 3A and 3B, the focal position of the cylindrical lens 71 and the position of the reference mirror 76 coincide with each other. Therefore, as shown in FIG. 7A, s emitted from the cylindrical lens 71 in the x direction.
The polarized beam 74 is condensed on the reference mirror 76, and is incident as parallel light in the y direction as it is as shown in FIG.

As shown in FIGS. 9A and 9B, the front focus position of the objective lens 42 coincides with the surface of the sample 47, and the rear focus position 44 of the objective lens 42 is the imaging lens 78. The focal point of the front side is coincident with the focal point of the front side, and the focal point of the rear side of the imaging lens 78 is coincident with the image pickup surface of the CCD one-dimensional sensor 82. That is, this optical system is a dual telecentric imaging optical system. Therefore, as shown in FIG. 7A, in the x direction, the parallel reflected light from the surface of the sample 47 is focused on the rear focus position 44 after passing through the objective lens 42 and becomes parallel light again after passing through the image forming lens 78. It is incident on the sensor 82. On the other hand, as shown in FIG. 7B, in the y direction, the divergent reflected light from the surface of the sample 47 becomes parallel light after passing through the objective lens 42, and after passing through the imaging lens 78, the focal point on the rear side thereof, that is, on the CCD one-dimensional sensor 82. Focus on. As a result, on the CCD one-dimensional sensor 82,
Similar to the probe beam 190 on the sample 47, one stripe beam having a width in the x direction and focused in the y direction can be obtained. On the other hand, as shown in FIGS. 9A and 9B, the position of the reference mirror 76 and the front focus position of the imaging lens 78 coincide with each other. Therefore, as shown in FIG. 4A, the divergent reflected light from the reference mirror 76 becomes parallel light after passing through the imaging lens 78 and enters the CCD one-dimensional sensor 82 as shown in FIG. In the y direction, after passing through the image forming lens 78, the light is focused on the rear focus position, that is, the CCD one-dimensional sensor 82. Therefore, the heterodyne interference light obtained by the reflected light from the sample 47 and the reference light from the reference mirror 76 becomes the same stripe beam as the probe beam light 72 on the CCD one-dimensional sensor 82, and the one-dimensional optical interference signal in the x direction is detected. To be done.

In the following, the signal processing system 203 causes C
A method for extracting from the output signal of the CD one-dimensional sensor 82 the amplitude and phase of the minute displacement of the surface of the sample 47 that is generated based on the photoacoustic effect without being affected by the reflectance distribution and the unevenness distribution of the surface of the sample 47 will be described. To do. Now, let the wavelength of the probe beam light 72 incident on the surface of the sample 47 be λ,
The amplitude is 1, the reflection coefficient on the surface of the sample 47 is a _s , the reflection coefficient on the reference optical path is a _r , and the optical phase difference between the optical path of the probe light and the reference optical path including the phase change due to the unevenness of the surface of the sample 47. Is φ, the minute displacement of the surface of the sample 47 due to the photoacoustic effect is A, and the phase change amount with respect to the intensity modulation signal is θ, the heterodyne interference light I incident on one pixel of the CCD one-dimensional sensor 82 is expressed by the following equation (2). It is represented by.

[0041]

[Equation 2]

Further, from A << λ, the above equation is approximately
It is changed to the form of (Equation 3).

[0043]

[Equation 3]

Where A · cos (2πf _L t + θ)
Is a term representing the complex amplitude of the minute displacement of the surface of the sample 47 generated based on the photoacoustic effect. CCD one-dimensional sensor 82
Detection signal I _D (n + i) (n +
i is the number of accumulations / outputs of the CCD one-dimensional sensor 82) is given by the following equation, where α / f _B is the accumulation time of the sensor.

[0045]

[Equation 4]

Next, with respect to (Equation 4), conditions for satisfying the following items are obtained.

(1) Second term ≠ 0 (2) Phase shift amount with respect to the number of storage / output times i in the second term = π / 2 or π / 4 (3) Third term ≠ 0 (4) In the third term Phase shift amount for accumulation / output count i = π / 2 (5) 4th term = 0 The condition obtained is as follows, where p and s are integers and α is a non-integer. On the street.

[0048]

[Equation 5]

[0049]

[Equation 6]

For example, if s = 6 and p = 2, then α = 2
⅛, f _L = 50 kHz, and f _B = 210 kHz can be set, and (Equation 4) has the form of the following equation (Equation 7).

[0051]

[Equation 7]

The above parameter α = 21/8, f _L
= 50 kHz and f _B = 210 kHz are all set by the computer 96 and sent to the CCD one-dimensional sensor drive control circuit 93 and the modulation signal control circuit 90 respectively, and the CCD one-dimensional sensor drive and the oscillator 87 and the oscillator 87 based on the value of each parameter. 9
1 drive is controlled. The sensor accumulation time α / f _B is set by the CCD one-dimensional sensor drive control circuit 93.
Based on the set beat frequency f _B sent from the computer 96 and the parameter α, a read shift pulse for the CCD one-dimensional sensor having a frequency f _B / α is produced, and the CCD 1
This is realized by driving the dimension sensor 82. .

In Equation 7, the first term is the DC component, and the second term is the phase shift amount π / 4 with respect to the number of storage / output times i.
The modulation component related to the optical phase difference φ between the optical path of the probe light and the reference optical path including the phase change due to the unevenness of the surface of the sample 47, and the third term is the phase shift amount with respect to the number of accumulation / output times i is π / 2. 47 is a modulation component related to the optical phase difference φ between the optical path of the probe light and the reference optical path including the phase change due to the unevenness of the surface, the amplitude A and the phase θ of the photoacoustic signal. When i = 1 to i = 8 in the equation 7, that is, signals for one cycle for the second term and two cycles for the third term are obtained, the following equations (8) (9) (10) (11) ) (Equation 12) (Equation 13) (Equation 14) (Equation 15)

[0054]

[Equation 8]

[0055]

[Equation 9]

[0056]

[Equation 10]

[0057]

[Equation 11]

[0058]

[Equation 12]

[0059]

[Equation 13]

[0060]

[Equation 14]

[0061]

[Equation 15]

Actually, after the detection signal I _D (n + i) from the CCD one-dimensional sensor 82 is amplified by the amplifier circuit 94,
Considering the SN ratio of the signal as shown in FIG. 10, (Equation 7)
10 data sets from i = 1 to i = 8
A total of 80 accumulated / output data sets are stored in the two-dimensional memory 95. If the number of pixels of the CCD one-dimensional sensor 82 is 256, then 256 × 80 data will be stored. Now, if the data of the w pixel at the time of (n + i) th accumulation / output is represented by (n + i, w),
The order of storage in the two-dimensional memory 95 is (n + 1,1), (n + 1,2), (n + 1,3), ..., (n + 1,256), (n + 2,1), (n + 2,2), (n + 2,3), ..., (n + 2,256), (n + 3,1), (n + 3,2), (n + 3,3), ..., (n + 3,256), :: (n + 80,1), (n + 80) , 2), (n + 80, 3), ..., (n + 80, 256). On the other hand, when reading from the two-dimensional memory 95, 80 accumulated / output data sets are sequentially read out for each pixel and sent to the computer 96 as follows.

(N + 1,1), (n + 2,1), (n + 3,1), ..., (n + 80,1), (n + 1,2), (n + 2,2), (n + 3,2) ,. n + 80,2), (n + 1,3), (n + 2,3), (n + 3,3), ..., (n + 80,3) ,: (n + 1,256), (n + 2,256), (n + 3,256) , (N + 80,256) In the computer 96, the following calculation processing is performed using 80 accumulated / output data sets for each pixel, and the reflectance a _s ^{2 of} the sample 47 surface and the sample 47 surface The optical phase difference φ between the optical path of the probe light and the reference optical path including the phase change due to the unevenness, the amplitude A of the photoacoustic signal for which the reflectance of the sample 47 surface was corrected, and the phase change due to the unevenness of the sample 47 surface were corrected. The phase θ of the photoacoustic signal is obtained.

First, the reflectance a _s ^{2 on the} surface of the sample 47 is expressed by
To (15) are given by the following equation (16).

[0065]

[Equation 16]

The optical phase difference φ between the optical path of the probe light and the reference optical path including the phase change due to the unevenness of the surface of the sample 47 is
From equation (8), equation (10), equation (12), and equation (14),
It is given by the following equation (Equation 17).

[0067]

[Equation 17]

The amplitude of the photoacoustic signal, that is, the minute displacement A on the surface of the sample 47 is expressed by the following equations (8), (9), (12), (1)
The reflectance of the surface of the sample 47 is corrected by the equations (3) and (16), and is given by the following equation (18).

[0069]

[Equation 18]

The phase of the photoacoustic signal, that is, the phase change θ with respect to the intensity-modulated signal of the excitation light, is expressed by (Equation 8), (Equation 9), (Equation 12), (Equation 13), (Equation 16) From the equation and the equation (17), a form in which the phase change due to the unevenness of the surface of the sample 47 is corrected is given by the following equation (19).

[0071]

[Formula 19]

11 (a), 11 (b) and 11 (c) are examples of photoacoustic signal detection in this embodiment. 11
In (a), due to the internal crack 120, the minute displacement 110 (broken line) on the surface of the Cu wiring pattern 102 is
Compared to the surface of the normal Cu wiring pattern 103,
You can see that it is getting bigger. The distribution 121 of the amplitude A of the photoacoustic signal in FIG. 9B and the phase θ of the photoacoustic signal before correction of the phase change due to the unevenness of the surface of the sample 47 in FIG.
In the distribution of + φ 124, the signals 123 (FIG. 11B) and 126 (FIG. 8C) of the internal cracks also appear strongly.

On the other hand, FIGS. 12 (a), 12 (b) and 12 (c)
Is an example of detection of a photoacoustic signal in this embodiment when the surface of the sample 47 has uneven distribution. As shown in FIG. 12B, the distribution 137 of the phase θ + φ of the photoacoustic signal before phase correction.
Is affected by the phase change due to the unevenness of the surface of the sample 47,
The SN ratio of the signal is significantly reduced, and it is extremely difficult to recognize the internal crack 135. However, as shown in FIG. 7C, the distribution 139 of the phase signal θ after the phase correction by the equation 19
Then, the signal 141 of the internal crack 135 can be clearly recognized without being affected by the phase change due to the unevenness of the surface of the sample 47.

A two-dimensional photoacoustic image of the entire surface of the sample 47 is obtained by processing the detection signal from the CCD one-dimensional sensor by the computer 96 while sequentially scanning the sample 47 in the xy directions by the xy stage 48. TV monitor 97
Is output to.

As described above, according to the present embodiment, a plurality of measurement points are arranged in parallel using a stripe-shaped excitation beam, instead of the so-called point scanning method in which information is detected point by point as in the conventional case. It is possible to detect photoacoustic signals at multiple measurement points of a sample simultaneously in parallel by simultaneously exciting and utilizing optical interference to detect photoacoustic signals generated at each point, and simultaneously detecting interference light in parallel. , It becomes possible to detect the two-dimensional internal information of the sample at high speed.

Further, according to this embodiment, only one CC
The D1 dimensional sensor can detect the reflectance distribution of the sample surface, the unevenness distribution of the sample surface, the amplitude distribution of the photoacoustic signal, and the phase distribution of the photoacoustic signal and a total of four surfaces and internal information at the same time. Multiple evaluations are possible.

Further, according to this embodiment, it is possible to detect the photoacoustic signal in which the reflectance distribution of the sample surface, the unevenness distribution of the sample surface, and the fluctuation of the optical path are corrected, and the high sensitivity of the sample surface and the internal information can be obtained. And stable detection becomes possible.

Furthermore, according to the present embodiment, the thermal diffusion length based on the photoacoustic effect is equal to or longer than the depth of the interface between the Cu wiring pattern to be inspected and the ceramic substrate, By setting the intensity modulation frequency of the excitation beam, it is possible to inspect the internal interface.

Furthermore, according to the present embodiment, when the photoacoustic signal is extracted from the optical interference signal, digital processing is used instead of analog frequency filtering processing, so that the influence of harmonic components is small and the sensitivity is high. It is possible to detect a photoacoustic signal with high accuracy.

In the present embodiment, the application example of the present invention to the sample having a plurality of inspection objects with high thermal contrast is described, but the application to the sample made of a uniform material including internal cracks is also sufficiently possible. is there. Even in this case, since it is possible to simultaneously excite a plurality of measurement points on the sample, the above effect can be expected. A second embodiment of the present invention is shown in FIGS.
It will be described based on 1. FIG. 13 shows a photoacoustic detection optical system in the second embodiment. This optical system includes an excitation optical system 301, a heterodyne type differential interference optical system 302 for detecting a photoacoustic signal, and a signal processing system 303. In the pumping optical system 301, the configuration and function of the portion that obtains the intensity-modulated beam 35 having the modulation frequency f _L are exactly the same as in the first embodiment, so a description thereof will be omitted. After passing the intensity modulated beam 35 through the beam splitter 37, it is expanded to a desired beam diameter by the beam expander 38, and is further focused by the cylindrical lens (cylindrical lens) 150 at its focal position 159 only in the y direction. The focus position 159 coincides with the front focus position of the off-axis relay lens 152, the beam after passing through the relay lens 152 becomes parallel light again, and the dichroic prism 153 (reflection is performed at wavelengths of 600 nm or less and transmission of 600 nm or more is transmitted). After reflection, the pupil of the objective lens 154, that is, the rear focus position 155
Incident on. On the other hand, since the cylindrical lens 150 can be regarded as a plate glass having no curvature in the x direction, the beam incident on the relay lens 152 as parallel light remains on the rear side of the objective lens 154 which coincides with the rear focus position of the relay lens 152. The light is focused on the focal position 155. As a result, the front focus position of the objective lens 154, that is, the sample 47
On the surface of, as the excitation beam, has a width in the x direction and y
One striped beam 186 is obtained which is focused in the direction. In the beam splitter 37, about 10% of the intensity modulated beam 35 is the same as in the first embodiment.
9 is reflected and detected by the photoelectric conversion element 50 such as a photodiode, and then sent to the oscillator 87 via the amplifier circuit 89. The oscillator 87 compares the set frequency f _L sent from the modulation signal control circuit 90 with the measurement frequency f _L X detected by the photoelectric conversion element 50, and finely adjusts the oscillation frequency so that they match. The oscillator 87 is a PLL (Phase L
ock Loop) circuit and the like.

The excitation optical system 301 will be described in more detail with reference to FIG. 14A and 14B, the focus position 159 of the cylindrical lens 150 and the front focus position of the off-axis relay lens 152, the rear focus position of the relay lens 152, and the objective lens 154 are shown.
The rear focal position 155, and the front focal position of the objective lens 154 and the surface of the sample 47 respectively match. Therefore, as shown in FIG.
The beam 151 emitted from the cylindrical lens 150 is condensed at the focal position 159, that is, the front focal position of the relay lens 152, so that the beam after passing through the relay lens 152 becomes parallel light again and is incident on the objective lens 154. The beam 156 emitted from the lens 154 is the sample 47.
The light is focused on the surface. The relay lens 152
Is off-axis, the light-collecting position deviates from the center of the objective lens 154. On the other hand, FIG.
Cylindrical lens 1 in the x direction as shown in
Since 50 can be regarded as a plate glass having no curvature, the beam 151 emitted from the cylindrical lens 150 is incident on the relay lens 152 as parallel light and the relay lens 15
The light is focused on the rear focal position 155 of the objective lens 154 which coincides with the rear focal position of 2. As a result, the objective lens 154
The beam 156 emitted from the laser beam is incident on the surface of the sample 47 as parallel light. As a result, as shown in FIG. 15, on the surface of the sample 47, one stripe beam 186 having a width in the x direction and focused in the y direction is obtained as an excitation beam.

In FIG. 16, similarly to the first embodiment, a sample composed of Cu wiring patterns 102 and 103 formed by using an organic polymer material 104 such as polyimide as an insulator is irradiated with the stripe-shaped excitation beam 186. Shows a distribution 185 (broken line) of minute displacement on the sample surface based on the photoacoustic effect generated along the light absorption region 183. Similar to the first embodiment, the minute displacement distribution 185 includes
The internal information of each of the Cu wiring patterns 102 and 103 (internal crack 107, peeling defect 108) and the internal information of the polyimide portion 104 are independently reflected without being fused. That is, this stripe-shaped excitation beam 1
By using 86, a plurality of inspection targets having high thermal contrast can be excited at the same time, and two-dimensional internal information of the sample can be detected at high speed.

Next, regarding the structure and function of the heterodyne type differential interference optical system 302 for detecting the minute displacement distribution 185 (broken line) on the sample surface based on the photoacoustic effect,
It demonstrates based on FIG. 13, FIG. 17-FIG. In the heterodyne type differential interference optical system 302 of FIG. 13, two-frequency orthogonal polarization, that is, 112 and 11 as shown in FIG.
The configuration and function of the portion that obtains the combined light 67 that is orthogonal to each other in the direction of 3 and has a frequency difference of f _C1 -f _{C2 from} each other are the same as those of the first embodiment, and therefore the description thereof is omitted. still,
Here, the direction perpendicular to the plane of the paper of FIG. 13 is the x-axis, and the direction orthogonal to it is the y-axis. After passing the combined light 67 of two-frequency orthogonal polarization through the beam splitter 68, it is expanded to a desired beam diameter by a beam expander 70, and is further converted into an elliptical beam by a cylindrical lens (cylindrical lens) 160. Cylindrical lens 1 in the y direction
Since 60 can be regarded as a plate glass having no curvature, this elliptical beam remains parallel to the y direction and is reflected by the beam splitter 162, so that the cylindrical lens 16
Wollaston prism 163 placed at 0 focus position
(A Lotion prism may be used) to separate the p-polarized beam 164 and the s-polarized beam 165, both of which are parallel light. Since the position of the Wollaston prism 163 coincides with the front focus position of the relay lens 166, the chief rays of these two beams after passing through the relay lens 166 are parallel to each other, and each beam is the rear focus of the relay lens 166. The light is focused on the position 187. Since the rear focus position 187 of the relay lens 166 coincides with the front focus position of the relay lens 168, the chief rays of the two beams after passing through the relay lens 168 pass through the dichroic prism 153, and after the relay lens 168. It focuses on the rear focus position 155 of the objective lens 154 which coincides with the side focus position. Further, at the same time, the two beams are incident on the rear focus position 155 of the objective lens 154 while remaining parallel to each other. On the other hand, x
Regarding the direction, after the beam emitted from the cylindrical lens 160 is focused on the Wollaston prism 163,
After passing through the relay lens 166, it becomes parallel light, and after passing through the dichroic prism 153 by the relay lens 168, it is focused on the rear focus position 155 of the objective lens 154. As a result, at the front focus position of the objective lens 154, that is, on the surface of the sample 47, one stripe beam 18 having a width in the x direction and focused in the y direction is formed as an excitation beam.
6 is obtained. After passing through the λ / 4 plate 45, the two beams emitted from the objective lens 154 become circularly polarized beams 169 and 170, respectively. As shown in FIG. 15, the front side focal position of the objective lens, that is, the surface of the sample 47, has an excitation beam. 186
A striped beam 181 having a width in the x direction and focused in the y direction is obtained as the probe beam at the same position as the probe beam 186.
As a reference beam, a striped beam 182 having a width in the x direction and a focus in the y direction is obtained as a reference beam at a position slightly away from. As shown in FIG. 17, the reflected light from the position of the probe beam 181 of the sample 47 has the distribution 185 (broken line) of the minute displacement generated on the surface of the sample 47 due to the photoacoustic effect as the phase distribution information.
The reference beam 182 is the excitation beam 1 in FIG.
It is assumed that the light beam is incident on a position where the minute displacement 185 of the surface of the sample 47 is generated by 86, that is, outside the range of the thermal diffusion region 184, and as close to the probe beam 181 as possible as shown in FIG. In FIG. 13, sample 4
Each of the reflected lights from the positions of the probe beam 181 and the reference beam 182 of No. 7 becomes the s-polarized beam and the p-polarized beam after passing through the λ / 4 plate 45, and after passing through the objective lens 42, passes through the same optical path again, and the Wollaston prism 163. After being combined in (1), the light passes through the beam splitter 162. Figure 8
114 indicates the polarization direction of the reflected light from the position of the probe beam 181, and 115 indicates the polarization direction of the reflected light from the position of the reference beam 182. Since they are orthogonal to each other, they do not interfere as they are. Therefore, by inserting a polarizing plate 79 after the imaging lens 78 and setting the polarization direction to the 45 ° direction as shown by 116 in FIG.
The two reflected lights interfere with each other to obtain the heterodyne interference light 171 having a beat frequency of f _B = f _C1 −f _C2 . The heterodyne interference light 171 contains, as optical phase distribution information, a one-dimensional distribution in the x direction of minute displacements generated on the surface of the sample 47 due to the photoacoustic effect. This interference light 171 has a center wavelength of 6
After the stray light is removed through the 33 nm interference filter 81, an image is formed on the accumulation type solid-state image sensor 82 such as a CCD one-dimensional sensor by the image forming lens 78. Since the image pickup surface of the CCD one-dimensional sensor 82 and the surface of the sample 47 are in an image-forming relationship, naturally, the stripe-shaped interference light is imaged on the image pickup surface like the probe beam formed on the surface of the sample 47. Note that the beam splitter 68 reflects about 10% of the beam light of the combined light 67 of the two-frequency orthogonally polarized light as in the first embodiment. Both polarization components of this light beam interfere with each other by the polarizing plate 83 whose polarization direction is 45 ° as shown by 116 in FIG. 8, and the beat signal of f _B X = f _C1 X−f _C2 X is generated by a photodiode or the like. Is detected by the photoelectric conversion element 85. This beat signal passes through the amplifier circuit 92 and the CCD 1
It is sent to the dimension sensor drive control circuit 93. In the drive control circuit 93, the set beat frequency f sent from the computer 96
_B is compared with the measurement frequency f _B X detected by the photoelectric conversion element 85, and the frequency f _{C1 of the} sine wave output from the oscillator 91 is output via the computer 96 and the modulation signal control circuit 90 so that they match. Or fine-tune f _C2 . Oscillator 91
Is composed of a PLL (Phase Lock Loop) circuit or the like.

The heterodyne type differential interference optical system 302 will be described in more detail with reference to FIGS. 18, 19 and 20 and 21. As shown in FIGS. 18 and 19, the focal position of the cylindrical lens 160 and the Wollaston
Position of prism 163, Wollaston prism 163
Position and the front focus position of the relay lens 166, the rear focus position 187 of the relay lens 166, and the relay lens 168.
Of the front surface, the rear focus position of the relay lens 168, the rear focus position 155 of the objective lens 154, and the front focus position of the objective lens 154 and the surface of the sample 47, respectively. Therefore, as shown in FIG. 18, since the cylindrical lens 160 can be regarded as a plate glass having no curvature in the y direction, the combined light 161 of the two-frequency orthogonally polarized light emitted from the cylindrical lens 160 remains parallel to the Wollaston prism 163. After entering, it is separated into a p-polarized beam 164 and an s-polarized beam 165 which are both parallel light. Since the position of the Wollaston prism 163 coincides with the front focus position of the relay lens 166, the chief rays of these two beams after passing through the relay lens 166 are parallel to each other, and each beam is the rear focus of the relay lens 166. The light is focused on the position 187. The rear focus position 187 of the relay lens 166 coincides with the front focus position of the relay lens 168.
The chief rays of the two beams have a rear focal position 155 of the objective lens 154 which coincides with a rear focal position of the relay lens 168.
Focus on. Further, at the same time, the two beams remain parallel lights and are incident on the rear focus position 155 of the objective lens 154, so that the two beams 16 emitted from the objective lens 154.
Both 9 and 170 are focused on the surface of the sample 47. The chief rays of both beams are parallel to each other.

On the other hand, as shown in FIG. 19, in the x-direction, the beam emitted from the cylindrical lens 160 is condensed on the Wollaston prism 163 and then becomes parallel light after passing through the relay lens 166. The light is focused on the rear focus position 155 of 154. Therefore, the beams 169 and 170 emitted from the objective lens 154 are both collimated and enter the surface of the sample 47. As a result, as shown in FIG.
On the surface of 7, a striped beam 181 having a width in the x direction and a focus in the y direction is obtained as a probe beam at the same position as that of the excitation beam 186, and slightly from the probe beam 181. As a reference beam at a distant position, a stripe beam 1 which has a width in the x direction and is focused in the y direction as in the probe beam 181.
82 is obtained.

As shown in FIGS. 20 and 21, the objective lens 1
The front focal position of 54 is the surface of the sample 47 and the objective lens 1
The rear focal position 155 of 54 is the rear focal position of the relay lens 168, the front focal position of the relay lens 168 is the rear focal position 187 of the relay lens 166, and the front focal position of the relay lens 166 is the Wollaston prism 163.
And the position of the Wollaston prism 163 coincide with the front focal position of the imaging lens 78, and the rear focal position of the imaging lens 78 coincides with the image pickup surface of the CCD one-dimensional sensor 82. That is, this optical system is a dual telecentric imaging optical system. Therefore, as shown in FIG. 20, y
Regarding the direction, the principal rays of the two divergent reflected lights from the surface of the sample 47 pass through the objective lens 154 and then the rear focal position 155.
And the two beams simultaneously enter the relay lens 168 while remaining as parallel lights. Objective lens 154
Since the rear focal point position 155 of the rear lens coincides with the rear focal point position of the relay lens 168, the chief rays of the two beams after passing through the relay lens 168 become parallel to each other, and at the same time, the two beams of the relay lens 168 respectively. The light is focused on the front focus position, that is, the rear focus position 187 of the relay lens 166. The two beams that have passed through the relay lens 166 are combined by the Wollaston prism 163, and after passing through the imaging lens 78 as parallel light, the focal point on the rear side, that is, C
The light is focused on the CD one-dimensional sensor 82. On the other hand, as shown in FIG. 21, in the x direction, the two parallel reflected lights from the surface of the sample 47 pass through the objective lens 154 and then the rear focal position 1
After converging on 55, it becomes parallel light after passing through the relay lens 168, and is converged on the front focus position of the relay lens 166, that is, the position of the Wollaston prism 163. Further, after passing through the imaging lens 78, it becomes parallel light again and the CCD one-dimensional sensor 8
Incident on 2. As a result, on the CCD one-dimensional sensor 82, similarly to the probe beam 181 and the reference beam 182 on the sample 47, there is a width in the x direction and a focus in the y direction.
A striped beam of books is obtained. That is, the heterodyne interference light obtained by the reflected light from each of the probe beam 181 and the reference beam 182 becomes a stripe beam on the CCD one-dimensional sensor 82, and a one-dimensional optical interference signal in the x direction is detected. The configuration and the function of the signal processing system 303 are exactly the same as those of the signal processing system 203 in the first embodiment, and like the first embodiment, the output signal of the CCD one-dimensional sensor 82 is used to determine the photoacoustic effect. The amplitude and phase of the minute displacement on the surface of the sample 47 generated by
7 can be extracted without being affected by the reflectance distribution and the unevenness distribution on the surface.

While the sample 47 is successively scanned in the xy directions by the xy stage 48, the detection signal from the CCD one-dimensional sensor is processed by the computer 96 to obtain a two-dimensional photoacoustic image of the entire surface of the sample 47. TV monitor 97
Is output to.

As described above, according to the present embodiment, a stripe-shaped excitation beam is used as in the first embodiment, instead of the so-called point scanning method in which information is detected point by point as in the conventional case. Using multiple excitation points in parallel at the same time, utilizing optical interference to detect the photoacoustic signal generated at each point,
By detecting the interference light in parallel at the same time, the photoacoustic signals at a plurality of measurement points of the sample can be simultaneously detected in parallel, and the two-dimensional internal information of the sample can be detected at high speed.

Further, according to this embodiment, as in the first embodiment, the reflectance distribution of the sample surface, the unevenness distribution of the sample surface, the amplitude distribution of the photoacoustic signal, and The phase distribution of the photoacoustic signal and a total of four surface and internal information can be detected at the same time, which enables complex evaluation of the sample.

Further, according to the present embodiment, similarly to the first embodiment, it is possible to detect the photoacoustic signal in which the reflectance distribution on the sample surface, the unevenness distribution on the sample surface, and the fluctuation of the optical path are corrected. It enables highly sensitive and stable detection of information on the surface and inside.

Further, according to this embodiment, as in the first embodiment, the thermal diffusion length based on the photoacoustic effect is the object of inspection C.
The internal interface can be inspected by setting the intensity modulation frequency of the excitation beam so that the length is equal to or more than the depth of the interface between the u wiring pattern and the ceramic substrate.

Further, according to the present embodiment, as in the first embodiment, when the photoacoustic signal is extracted from the optical interference signal, digital processing is used instead of analog frequency filtering processing. It is possible to detect a photoacoustic signal with high sensitivity and high accuracy, which is less affected by.

Further, in the present embodiment, the interference optical system for detecting the minute displacement of the sample surface based on the photoacoustic effect is the differential interference optical system. That is, the reference light is not obtained from the reference mirror provided separately, but the reflected light from the sample surface of the reference beam incident near the probe light is used as the reference light, so that the probe light and the reference light are almost the same. , And the same optical system, the fluctuation of the optical path length between the two lights and the deviation of the wavefront are significantly reduced, and the detection accuracy and the detection sensitivity of the photoacoustic signal are greatly improved. Furthermore,
Since it is not necessary to separately provide the reference optical path, the optical system is simplified, its stability is improved, and the detection accuracy of the photoacoustic signal is improved.

In this embodiment, the example of application of the present invention to the sample having a plurality of inspection objects with high thermal contrast is described. However, application to a sample made of a uniform material including internal cracks is also possible. is there. Even in this case, since it is possible to simultaneously excite a plurality of measurement points on the sample, the above effect can be expected.

A third embodiment of the present invention will be described with reference to FIGS. FIG. 22 shows a photoacoustic detection optical system in the third embodiment. This optical system includes an excitation optical system 201, a heterodyne type Twyman-Green interference optical system 402 for detecting a photoacoustic signal, and a signal processing system 403. The structure and function of the pumping optical system 201 are exactly the same as those in the first embodiment, so the description thereof will be omitted. Further, the configuration of the heterodyne type Twyman-Green interference optical system 402 is the same as the heterodyne type Twyman-Green interference optical system 202 of the first embodiment except that the beat signal detecting beam splitter 68, the polarizing plate 83 and the photoelectric conversion element 85 are removed. Further, the configuration is the same as that of the first embodiment except that a parallel output type photoelectric conversion element array 191 is used instead of the storage type CCD one-dimensional sensor 82 for detecting the interference light, and therefore the description will be made. Is omitted. As shown in FIG. 23, the optical interference signals output from each pixel of the parallel output type photoelectric conversion element array 191 are amplified for each pixel by the preamplifier group 192 arranged in the same number as the number of pixels, and then the same. In the lock-in amplifier group 193 arranged by the same number as the number of pixels, the intensity modulation signal 50a detected by the photoelectric conversion element 50 is used as a reference signal, and the modulation frequency component included in the optical interference signal is used as a photoacoustic signal.
That is, the amplitude and phase of the minute displacement on the surface of the sample 47 generated based on the photoacoustic effect are simultaneously detected for all pixels.
The detected photoacoustic signal is converted into digital data by the AD converter group 194 and then sent to a parallel-in / serial-out type shift register 195 to be converted into a one-dimensional signal. The position signal of the xy stage 48 and the output signal from the shift register 195 are processed by the computer 96, and the photoacoustic signal at each point of the sample 47, that is, the sample 4
A two-dimensional photoacoustic image of the entire 7 surface is obtained and output to the TV monitor 97. In this embodiment, the non-accumulation type parallel output type photoelectric conversion element array 191 is used for detecting the interference light, but the accumulation type is also applicable. In that case, the signal processing system 403 can be used as it is, or the lock-in amplifier group 19 can be used in the signal processing system 403.
3 is removed, the accumulation time of the photoelectric conversion element array is controlled based on the equations 4 to 6 as in the first or second embodiment to obtain a signal whose phases are mutually shifted, and this signal is obtained from the equation 16 to
It is also possible to perform arithmetic processing on a computer based on the equation (19).

The present example is applied to a sample having a plurality of inspection objects with high thermal contrast as shown in FIGS. 4 and 5 and also to a sample made of a uniform material including internal cracks. Is also sufficiently applicable.

As described above, according to the present embodiment, a stripe-like pattern is used as in the first and second embodiments, instead of the so-called point scanning method in which information is detected point by point as in the conventional case. By simultaneously exciting multiple measurement points in parallel using an excitation beam and using optical interference to detect the photoacoustic signal generated at each point, the interference light is detected in parallel at the same time, and Acoustic signals can be simultaneously detected in parallel, and two-dimensional internal information of the sample can be detected at high speed.

Further, if the accumulation type one-dimensional sensor is used in this embodiment, the reflectance distribution of the sample surface, the unevenness distribution of the sample surface, the light distribution can be obtained by using only one one-dimensional sensor as in the first embodiment. The amplitude distribution of the acoustic signal and the phase distribution of the photoacoustic signal and a total of four surface and internal information can be detected at the same time, and composite evaluation of the sample becomes possible.

Further, if the accumulation type one-dimensional sensor is used in this embodiment, the photoacoustic signal in which the reflectance distribution of the sample surface, the unevenness distribution of the sample surface, and the fluctuation of the optical path are corrected as in the first embodiment. Can be detected, and highly sensitive and stable detection of the sample surface and internal information becomes possible.

Further, if the storage type one-dimensional sensor is used in this embodiment, the thermal diffusion length based on the photoacoustic effect is the same as in the first embodiment at the interface between the Cu wiring pattern to be inspected and the ceramic substrate. The internal interface can be inspected by setting the intensity modulation frequency of the excitation beam so that the length is equal to or more than the depth.

Furthermore, if the storage type one-dimensional sensor is used in this embodiment, as in the first embodiment, when the photoacoustic signal is extracted from the optical interference signal, digital processing is performed instead of analog frequency filtering processing. Since it is used, it is possible to detect a photoacoustic signal with high sensitivity and high accuracy, with less influence of harmonic components.

The non-accumulation type photoelectric conversion element array 191
After storing the optical interference signal output from each pixel in the two-dimensional memory, the photoacoustic signal can be detected by one lock-in amplifier as a one-dimensional signal read out for each pixel.

A fourth embodiment of the present invention will be described with reference to FIGS. FIG. 24 shows a photoacoustic detection optical system in the fourth embodiment. This optical system includes an excitation optical system 501, a heterodyne type Twyman-Green interference optical system 202 for detecting a photoacoustic signal, and a signal processing system 203. Since the configurations and functions of the heterodyne type Twyman-Green interference optical system 202 and the signal processing system 203 are exactly the same as those in the first embodiment, the description thereof will be omitted. While the stripe-shaped excitation beam is used in the first to third embodiments, the excitation optical system 5 is used in this embodiment.
No. 01 uses a multi-spot beam parallel irradiation optical system 197, which is a big difference. Other parts are the same as those in the first to third embodiments. The multiple spot beam parallel irradiation optical system 197 will be described with reference to FIG. The expanded parallel light from the beam expander 38 becomes a striped beam after passing through a mask 210 having a striped opening 210a shown in FIG. 28, and enters a one-dimensional microlens array 210. The rear focus position of each micro lens is the relay lens 2
13 is the front focal position 212 of the objective lens 42, and the rear focal position of the relay lens 213 is the rear focal position 214 of the objective lens 42.
Further, the front focus position of the objective lens 42 is coincident with the surface of the sample 47, respectively. Each beam from the one-dimensional microlens array 210 has a front focus position 212 of the relay lens 213.
After converging each of them, the light is collimated after passing through the relay lens 213, and further converged on the surface of the sample 47 as focused light after passing through the objective lens 42. The chief rays of each spot beam are parallel to each other. FIG. 27 shows how each spot beam irradiates the sample at the same time. still,
The number of spot beams is made equal to the number of pixels of the CCD one-dimensional sensor 82 for detecting optical interference, and the interval thereof is the thermal diffusion region 2 generated by each spot beam as shown in FIG.
17 is not duplicated. As the probe beam for detecting heterodyne interference, a striped beam is used as in the first to third embodiments. Signal processing system 203
And the function thereof are exactly the same as those in the first embodiment. Similar to the first embodiment, the minute displacement of the surface of the sample 47 generated from the output signal of the CCD one-dimensional sensor 82 based on the photoacoustic effect. Can be extracted without being affected by the reflectance distribution and the unevenness distribution on the surface of the sample 47.

While the sample 47 is successively scanned in the xy directions by the xy stage 48, the detection signal from the CCD one-dimensional sensor is processed by the computer 96 to obtain a two-dimensional photoacoustic image of the entire surface of the sample 47. TV monitor 97
Is output to.

The present example is applied to a sample having a plurality of inspection objects with high thermal contrast as shown in FIGS. 4 and 5 and also to a sample made of a uniform material including internal cracks. Is also sufficiently applicable.

As described above, according to the present embodiment, a plurality of spot beams are irradiated in parallel at the same time instead of the so-called point scanning method in which information is detected point by point as in the prior art. Simultaneous excitation of measurement points in parallel, using optical interference to detect photoacoustic signals generated at each point,
By detecting the interference light in parallel at the same time, the photoacoustic signals at a plurality of measurement points of the sample can be simultaneously detected in parallel, and the two-dimensional internal information of the sample can be detected at high speed.

Further, according to the present embodiment, since the thermal diffusion regions of the respective excitation beams do not overlap, there is an effect that the detection resolution of the photoacoustic image is improved.

Further, according to this embodiment, as in the first embodiment, the reflectance distribution of the sample surface, the unevenness distribution of the sample surface, the amplitude distribution of the photoacoustic signal, and The phase distribution of the photoacoustic signal and a total of four surface and internal information can be detected at the same time, which enables complex evaluation of the sample.

Further, according to this embodiment, as in the first embodiment, it becomes possible to detect the photoacoustic signal in which the reflectance distribution of the sample surface, the unevenness distribution of the sample surface, and the fluctuation of the optical path are corrected, and It enables highly sensitive and stable detection of information on the surface and inside.

Further, according to the present embodiment, as in the first embodiment, the thermal diffusion length based on the photoacoustic effect is the object of inspection C.
The internal interface can be inspected by setting the intensity modulation frequency of the excitation beam so that the length is equal to or more than the depth of the interface between the u wiring pattern and the ceramic substrate.

Furthermore, according to the present embodiment, as in the first embodiment, when the photoacoustic signal is extracted from the optical interference signal, digital processing is used instead of analog frequency filtering processing. It is possible to detect a photoacoustic signal with high sensitivity and high accuracy, which is less affected by.

In this embodiment, the storage CCD one-dimensional sensor is used for detecting the interference light, but the non-storage type parallel output type photoelectric conversion element array as in the third embodiment is also applicable. In that case, the signal processing system 403 in the third embodiment may be used.

In the first to third embodiments described above, the one-dimensional stripe-shaped excitation beam and the probe beam are used, but a two-dimensional beam having a certain area is used. Is also possible. In that case, of course, a two-dimensional sensor is used for detecting the interference light. Similarly, also in the fourth embodiment, it is possible to arrange a plurality of spot beams in a two-dimensional shape and use a two-dimensional sensor.

[0114]

According to the present invention, it is possible to simultaneously excite strip-shaped inspection regions of a sample in parallel and use optical interference to detect a photoacoustic signal generated in the strip-shaped inspection region, and to detect interference light in parallel at the same time. Thus, it is possible to detect the photoacoustic signals in the strip inspection region of the sample in parallel at the same time, and it is possible to detect the two-dimensional surface or internal information of the sample at a high speed, which is a great effect.

Further, with only one sensor, the reflectance distribution on the sample surface, the unevenness distribution on the sample surface, the amplitude distribution of the photoacoustic signal, and the phase distribution of the photoacoustic signal, a total of four surfaces and internal information are simultaneously detected. This has the effect of enabling high-speed composite evaluation of the sample.

Further, it becomes possible to detect the photoacoustic signal in which the reflectance distribution of the sample surface, the unevenness distribution of the sample surface, and the fluctuation of the optical path are corrected, and the highly sensitive and stable detection of the sample surface and internal information becomes possible. Has the effect of becoming.

Further, the intensity modulation frequency of the excitation beam is set so that the thermal diffusion length based on the photoacoustic effect is equal to or longer than the depth of the internal interface to be inspected. This has the effect of enabling inspection of

Further, when the photoacoustic signal is extracted from the optical interference signal, since digital processing is used instead of analog frequency filtering processing, the influence of harmonic components is small, and the highly sensitive and highly accurate photoacoustic signal can be obtained. It has the effect of enabling detection.

[Brief description of drawings]

FIG. 1 is a diagram showing a photoacoustic detection optical system in a first embodiment of the present invention.

FIG. 2 is a diagram showing a modulation signal input to an acousto-optic modulator.

FIG. 3 is a configuration diagram of an excitation optical system and a heterodyne interference optical system in the first example.

FIG. 4 is a perspective view showing a planar structure of a sample, an excitation beam and a probe beam in the first example.

FIG. 5 is a diagram showing a cross-sectional structure of a sample in the first example and a state in which a photoacoustic effect is generated by a stripe-shaped excitation beam.

FIG. 6 is a diagram showing a polarization direction of a laser beam incident on a heterodyne interference optical system and a dual-frequency orthogonal polarization state.

FIG. 7 is a diagram showing a state in which a striped probe beam is incident on a sample surface in the first embodiment.

FIG. 8 is a diagram showing each polarization direction of reflected light from a sample, reference light, and a polarizing plate.

FIG. 9 is a configuration diagram of a detection unit of the heterodyne interference optical system in the first example.

FIG. 10 is a diagram showing a data configuration in a two-dimensional memory.

FIG. 11 is a diagram showing a detection example of a photoacoustic signal in the first embodiment.

FIG. 12 is a diagram showing an example of photoacoustic signal detection showing the effect of phase correction in the first embodiment.

FIG. 13 is a diagram showing a photoacoustic detection optical system according to a second embodiment of the present invention.

FIG. 14 is a configuration diagram of an excitation optical system in a second example.

FIG. 15 is a perspective view showing a planar structure of a sample, an excitation beam, a probe beam, and a reference beam in a second example.

FIG. 16 is a diagram showing a cross-sectional structure of a sample and a state of generation of a photoacoustic effect by a stripe-shaped excitation beam in the second example.

FIG. 17 is a diagram showing the state of incidence of a striped probe beam and a reference beam on the sample surface in the second example.

FIG. 18 is a configuration diagram of the heterodyne interference optical system in the second example as viewed from the X-axis direction.

FIG. 19 is a configuration diagram of the heterodyne interference optical system shown in FIG. 18 viewed from the Y-axis direction.

FIG. 20 is a configuration diagram of the detection unit of the heterodyne interference optical system according to the second embodiment as viewed from the X-axis direction.

21 is a configuration diagram of the detection unit of the heterodyne interference optical system shown in FIG. 20, viewed from the Y-axis direction.

FIG. 22 is a diagram showing a photoacoustic detection optical system according to a third embodiment of the present invention.

FIG. 23 is a diagram showing a configuration of a signal processing system according to a third embodiment.

FIG. 24 is a diagram showing a photoacoustic detection optical system according to a fourth embodiment of the present invention.

FIG. 25 is a diagram showing a configuration of a multiple spot beam parallel irradiation optical system in a fourth example.

FIG. 26 is a diagram showing the shape of a mask of a multiple spot beam parallel irradiation optical system in a fourth example.

FIG. 27 is a diagram showing how a plurality of spot beams simultaneously irradiate a sample in a fourth example.

FIG. 28 is a diagram showing a thermal diffusion region generated by each spot beam in the fourth embodiment.

FIG. 29 is a diagram for explaining a conventional photoacoustic detection optical system.

FIG. 30 is a principle diagram of a photoacoustic effect.

[Explanation of symbols]

1, 8 ... Laser, 31 ... Ar laser, 51 ... He-Ne
Laser, 33, 57, 62 ... Acousto-optic modulator, 39,
71, 150, 160 ... Cylindrical lens, 42,
154 ... Objective lens, 82 ... CCD one-dimensional sensor, 5
0, 85 ... Photoelectric conversion element, 95 ... Two-dimensional memory, 96,
196 ... Calculator, 47 ... Sample, 102, 103, 13
1, 132 ... Cu wiring pattern, 191 ... Parallel output type photoelectric conversion element array, 193 ... Lock-in amplifier group, 19
7 ... Multiple spot beam parallel irradiation optical system.

Claims (4)

[Claims] 1. A strip-shaped inspection region of a sample is irradiated with light intensity-modulated at a desired frequency to generate a photoacoustic effect or a photothermal effect on the surface or inside of the strip-shaped inspection region, and the light is striped. Irradiate on the surface of the inspection area and detect the interference light between the reflected light and the reference light by the photoelectric conversion element which has a conjugate relationship with the sample surface, and in the band-shaped inspection area from the detected interference light intensity signal. Sample characterized by detecting the thermal strain of the same frequency component as the intensity modulation frequency caused by the photoacoustic effect or the photothermal effect and detecting the surface or internal information of the strip inspection region of the sample from the thermal strain of the frequency component Surface or internal information detection method. 2. A light which is intensity-modulated at a desired frequency is shaped into a shape covering the band-shaped inspection region and irradiated onto the sample surface to generate a photoacoustic effect or a photothermal effect on the surface or inside of the band-shaped inspection region, The sample surface is irradiated with light having a shape that covers the band-shaped inspection region, and the interference light between the reflected light and the reference light is detected by a photoelectric conversion element array having a conjugate relationship with the sample surface, and the detected interference light intensity. From the detected interference light intensity signal, the thermal strain of the same frequency component as the intensity modulation frequency generated by the photoacoustic effect or the photothermal effect in the band-shaped inspection region is detected from the detected thermal strain of the frequency component. A method for detecting the surface or internal information of a sample, which comprises detecting the surface or internal information of a strip inspection region of the sample. 3. A light source, a modulation means for intensity-modulating the light from the light source at a desired frequency, and irradiating the intensity-modulated light onto the surface of the band-shaped inspection region of the sample or the surface of the band-shaped inspection region. Excitation means for generating photoacoustic effect or photothermal effect inside, and photoelectric conversion in which the interference light between the reflected light and the reference light is conjugated with the sample surface by irradiating light on the surface of the strip inspection area of the sample The interference light detecting means for detecting with an element, and detecting the thermal strain of the same frequency component as the intensity modulation frequency generated by the photoacoustic effect or the photothermal effect in the band-shaped inspection region from the detected interference light intensity signal, An internal information detecting device for detecting the surface of a strip-shaped inspection region of a sample or internal information detecting means for detecting internal information from thermal strain of a frequency component. 4. A light source, a modulation means for intensity-modulating the light from the light source at a desired frequency, the intensity-modulated light is shaped into a shape covering a band-shaped inspection region, and the sample surface is irradiated with the band-shaped light. Excitation means for generating a photoacoustic effect or a photothermal effect on the surface or inside of the inspection area, and irradiating the sample surface with light in a shape covering the band-shaped inspection area and interfering light between the reflected light and the reference light on the sample surface Interference light detecting means for detecting with a photoelectric conversion element array having a conjugate relationship with the above, and a photoacoustic effect or a photothermal effect in a band-shaped inspection region from among the detected interference light intensity signals among the detected interference light intensity signals And an internal information detecting means for detecting the thermal strain of the same frequency component as the intensity modulation frequency generated by the above and detecting the surface or internal information of the strip inspection region of the sample from the thermal strain of the frequency component. Sample Surface or internal information detecting device.