JPH05288725A - Detecting method of exfoliation of thin film and evaluating method of adhesion strength - Google Patents

Abstract

PURPOSE:To obtain a highly reliable method for detecting exfoliation of a thin film on the basis of a non-destructive analysis using an ultrasonic wave. CONSTITUTION:In a measuring sequence, an ultrasonic wave P having a prescribed central frequency is transmitted from a single probe 7 to a thin film 22 vertically. A reflected wave of the ultrasonic wave P is received by the probe 7 and a frequency characteristic in the vicinity of the central frequency of the reflected wave is subjected to an FFT analysis. This operation is executed with respect to a plurality of probes being different in the central frequency, and when the frequency characteristic of the reflected wave contains the vibration of a prescribed amplitude or above, it is determined that exfoliation exists between a substrate 21 and the thin film 22.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for nondestructively detecting delamination of a thin film and evaluating the adhesion strength thereof by using ultrasonic waves, and particularly to a thin film having improved reliability based on frequency characteristics by FFT analysis. The present invention relates to a peeling detection method and an adhesion strength evaluation method.

[0002]

2. Description of the Related Art Conventionally, a technique for forming a thin film on a substrate has been widely used in fields such as electronic materials and new materials. Among them, regarding the diamond thin film, the recent C
Attention has been paid to the fact that the VD method has made it possible to synthesize diamond from the vapor phase inexpensively and with high purity. Particularly in the field of cutting, a diamond thin film is expected as a cutting tool having high hardness and excellent wear resistance required for high-precision machining of superhard aluminum alloys, which are in increasing demand.

By the way, one of the important parameters for determining the durability and stability of a thin film is the adhesion strength, and it is essential to evaluate the adhesion strength in order to guarantee the life and performance of the thin film. Further, it is necessary to detect peeling as a state where the adhesion strength is extremely lowered. Therefore, there is a demand for a method capable of measuring and evaluating the peeling strength and adhesion strength of a thin film of a particularly hard material.

Conventionally, a scratching method using an inspection needle is well known as a method for evaluating the adhesion strength of a thin film.
However, in the scratching method, since the inspection needle is heavily worn, it is not suitable for measuring the adhesion strength of an extremely hard material such as a diamond thin film, and an accurate adhesion strength cannot be obtained.

[0005]

Since the conventional thin film delamination detection method and adhesion strength evaluation method use the scratch method or the like as described above, reliability is improved because abrasion of the inspection needle occurs. There was a problem that I could not do it.

The present invention has been made in order to solve the above-mentioned problems, and uses ultrasonic waves capable of nondestructive analysis, and reliability of thin film measurement based on FFT analysis of reflected or transmitted waves. An object of the present invention is to obtain a method for detecting delamination of a thin film and a method for evaluating adhesion strength with improved properties.

[0007]

A thin film delamination detection method according to the present invention comprises a step of transmitting an ultrasonic wave having a predetermined center frequency vertically from a single probe to the thin film.
A measurement sequence including a step of receiving a reflected wave of ultrasonic waves by a probe and a step of performing FFT analysis of frequency characteristics near the center frequency of the reflected wave is performed for a plurality of probes with different center frequencies, When the frequency characteristic of 1 includes vibration with a predetermined amplitude or more, it is determined that peeling exists between the substrate and the thin film.

Further, the thin film adhesion strength evaluation method according to the present invention comprises a step of transmitting an ultrasonic wave having a predetermined center frequency from the first probe to the object at an inclination angle, and transmitting the ultrasonic wave. The step of receiving the wave by the second probe, the step of FFT analyzing the frequency characteristic of the transmitted wave, and the step of comparing the frequency characteristic of the transmitted wave with respect to the subject with the frequency characteristic of the transmitted wave with respect to only the substrate. ,
It is determined that the adhesion strength between the substrate and the thin film is good when the frequency characteristic of the transmitted wave with respect to the subject differs from the frequency characteristic of the transmitted wave only with respect to the substrate by a predetermined amplitude or more.

[0009]

In the thin film delamination detection method according to the present invention, the difference in response to the reflected wave between the thin film in the normal adhesion state and the thin film in which delamination has occurred is measured by a single probe. Ask. Then, the oscillatory property of the reflected wave is detected from the frequency characteristics of the reflected wave obtained in a wide band by the probes having different center frequencies.

Further, in the thin film adhesion strength evaluation method according to the present invention, the difference in response to the transmitted waves of the thin films having different adhesion strengths is determined by comparing the transmitted waves of the ultrasonic waves obliquely incident from the first probe with the second wave. By measuring with the probe of
The difference between the frequency characteristics of the substrate alone and the frequency characteristics of the transmitted wave is evaluated.

[0011]

EXAMPLES Example 1. Hereinafter, Embodiment 1 of the present invention for detecting peeling will be described with reference to the drawings. FIG. 1 is a block diagram showing an ultrasonic exploration imaging apparatus for realizing Embodiment 1 of the present invention. In the figure, reference numeral 1 is a microcomputer having an FFT (Fast Fourier Transform) arithmetic processing function and controlling the entire apparatus. Reference numeral 2 denotes an FD (floppy disk) which is connected to the microcomputer 1 and serves as an external memory. 3 is a color display for displaying output data from the microcomputer 1 and 4 is connected to the color display 3 for printing the output data as appropriate. It is a color hard copy.

Reference numeral 5 is a scanner control device controlled by the microcomputer 1, 6 is an XYZ scanner which is scanned in three-dimensional directions by the scanner control device 5, and 7 is an ultrasonic wave P having a predetermined center frequency positioned by the XYZ scanner 6. A probe for transmitting the ultrasonic wave, 8 an acoustic lens integrally provided on the lower surface of the probe 7, 9 an object to which the ultrasonic wave P is irradiated, 10 a water W serving as a transmission medium of the ultrasonic wave P A container for positioning the subject 9, 11 is the subject 9 received by the probe 7.
The pulse wave receiver R receives the reflected wave signal R from the digital camera, and 12 is a digital oscilloscope that displays the reflected wave signal R transmitted through the pulser receiver 11 and transmits it to the microcomputer 1.

FIG. 2 shows the measuring unit (that is, the probe 7,
FIG. 3 is a side view showing in detail the acoustic lens 8 and the subject 9), 21 is a substrate, 22 is a thin film formed on the substrate 21 and constituting the subject 9 together with the substrate 21. The substrate 21 is, for example, (100)
It is made of a 670 μm thick single crystal silicon wafer having a face on the surface, and the thin film 22 is made of, for example, 5 μm thick diamond.

Next, a first embodiment of the present invention will be described with reference to FIGS. [Transmission Step] First, the subject 9 is installed in the container 10 filled with water W, and the XYZ scanner 6 is driven via the scanner control device 5 under the control of the microcomputer 1.
An ultrasonic wave P having a predetermined center frequency is applied to a single probe 7
Is transmitted perpendicularly to the surface of the thin film 22 of the subject 9.
At this time, as the probe 7 used, for example, Table 1
The characteristics shown in are listed.

Table 1: Characteristics of the probe Probe test frequency Focal length Diameter Panametrics V312 10MHz 12.7mm 6.35mm Hitachi I2-2504T 25MHz 10.0mm 6.35mm Panametrics V324 25MHz Flat type 6.35mm

Here, as will be described later, 2 MHz to 25 M
In order to determine the frequency characteristics of the reflected wave over the range of Hz, two focus type probes having a test frequency of 10 MHz and 25 MHz, namely, Panametrics V312 and Hitachi I2-
The 2504T is used, first the Panametrics V312 and then the transmission of the ultrasound P by the Hitachi I2-2504T.
The test frequency is a value of the nominal center frequency written for each probe 7, and the center frequency exists near the test frequency.

The ultrasonic wave P transmitted from the probe 7 is focused on the inside of the thin film 22.
In place of the subject 9, the reference test piece S0 of only the substrate 21 is installed,
This is performed by adjusting the position of the probe 7 so that the maximum sound pressure of the reflected wave from the surface of the substrate 21 is maximized.

[Receiving Step] The reflected wave from the interface between the thin film 22 and the substrate 21 and the thin film 22 is received by the probe 7 used for transmission and becomes the reflected wave signal R, and the pulsar receiver 11
Is input to the digital oscilloscope 12 via.

[FFT analysis step] The digital oscilloscope 12 samples the reflected wave signal R in units of 12.5 nsec and then inputs the sampled reflected wave signal R to the microcomputer 1. The microcomputer 1 spectrums the sampled reflected wave signal R by the FFT method. Convert to space (frequency characteristics). Thereby, the FFT analysis is performed on the frequency characteristic of the reflected wave near the center frequency.

[Measurement Sequence Repeating Step and Delamination Judging Step] The above measurement sequence is repeated for another probe 7 (that is, Hitachi I2-2504T) having a different center frequency, and the frequency characteristic of the reflected wave is a predetermined amplitude ( It is determined that peeling exists between the substrate and the thin film when the vibration including the (spectral intensity) or more is included.

FIG. 3 is a characteristic diagram showing an example of the frequency characteristic of the reflected wave obtained by the FFT analysis. The vertical axis represents the reflected wave from the subject 9 with respect to the reflected wave signal from the reference test piece S0 of only the substrate 21. The spectrum intensity ratio of the signal R is plotted on the horizontal axis. Here, the average of the sampling results of 512 times is shown, only the result of the range where the spectrum intensity is large with respect to the frequency near the center frequency of the probe 7 is shown, and the others are not shown because they are greatly affected by noise.

In FIG. 3, the solid line and the long broken line indicate the subject 9
If there is no peeling in the thin film 22 of, the short dashed line and the alternate long and short dash line are the respective frequency characteristics when there is peeling in the thin film 22 of the subject 9, and the frequency characteristics of 2 MHz to 10 MHz (solid line and short dashed line).
Is obtained by using the probe 7 having a test frequency of 10 MHz, and the frequency characteristic of 10 MHz to 25 MHz (long dashed line and alternate long and short dash line) is obtained by using the probe 7 having a test frequency of 25 MHz. ..

From FIG. 3, the frequency characteristic for the subject 9 without peeling of the thin film 22 shows that the reference test piece S0 is independent of the frequency.
It can be seen that the frequency characteristics substantially correspond to On the other hand, the frequency characteristic for the subject 9 in which the thin film 22 is peeled off oscillates around the value for the reference test piece S0 depending on the frequency, and the spectrum intensity ratio increases substantially in proportion to the frequency. I understand that.

<< Experimental Support of Example 1 >> Here, the substrate
The support of Example 1 will be described based on an experiment using a reference test piece S0 consisting of only 21, a test piece S1 having no peeling of the thin film 22 and a test piece S2 simulating a peeled state. First, under the conditions of Table 2, two kinds of test pieces S1 and S2 composed of a mixed gas of methane and hydrogen are synthesized in advance by a microwave CVD method and are composed of a silicon substrate and a diamond thin film, which are similar to the subject 9. ..

Table 2: Diamond thin film synthesis conditions Plasma induction microwave frequency 2.45 GHz Substrate temperature 1130K Total pressure in chamber 6.67 kPa Mixture gas flow rate 100 ml / min Methane concentration 0.5 vol.%

The substrates of the reference test piece S0 and the test pieces S1 and S2 are made of a single crystal silicon wafer having a (100) surface on the surface, like the object 9, and have a thickness of 670 μm. or,
The thin film of each test piece S1 and S2 has a thickness of 5 μm.

Here, the test piece S1 was prepared by subjecting the substrate to a scratching treatment with diamond abrasive grains of 2 to 4 μm for 30 minutes before synthesizing the thin film, and strongly bonding the substrate and the thin film. It is a test piece. Usually, a sufficient number of nucleation densities cannot be obtained for forming a continuous thin film on a mirror-finished silicon substrate, so a scratching process is performed to secure the adhesion strength of the thin film.

The test piece S2 is a thin film synthesized under the same conditions as those of the test piece S1. The thin film is separated by etching the substrate with a mixed solution of hydrofluoric acid and nitric acid, and then another mirror-finished substrate. It is a test piece made by adhering to. The thin film of the test piece S2 and the substrate were adhered to each other by fixing the periphery of the thin film to the substrate with an instant adhesive by using the surface tension of water. Therefore, a thin layer of water is formed between the substrate in the central portion to be measured and the thin film, and the test piece S2 simulates the peeled state of the thin film. Since the measurement of the thin film 22 by the ultrasonic wave P is performed in the water W as shown in FIG. 1, it is considered that the water W has entered the peeled portion.

The test pieces S1 and S2 as described above are irradiated with ultrasonic waves P using the focus type probe 7 having test frequencies of 10 MHz and 25 MHz as described above, and the maximum sound of the reflected wave at this time is emitted. Table 3 shows the ratio between the pressure and the maximum sound pressure obtained for the reference test piece S0 under the same conditions.

Table 3: Ratio (sound pressure ratio) between the maximum sound pressure of reflected waves in the test pieces S1 and S2 and the case of the reference test piece S0 ( test sound pressure ratio) Test frequency Sound pressure ratio S1 10MHz 0.0283dB 25MHz -0.0087dB S2 10MHz 0.7548dB 25MHz-1.7201dB

From Table 3, the measurement result for the test piece S1 having no thin film peeling is almost 0 dB regardless of the frequency,
It can be seen that the measurement results for the reference test piece S0 almost match. On the other hand, the measurement result for the test piece S2 in which thin film peeling occurred is higher than that of the reference test piece S0 at 10 MHz and is lower at 25 MHz, and the maximum sound pressure of the reflected wave depends on the frequency. I understand that. Therefore, measurement of only the maximum sound pressure is not suitable for detection of separation.

On the other hand, the spectral characteristics obtained by measurement for each of the test pieces S1 and S2 are the same as those in FIG. That is, the spectral characteristic of the test piece S1 is constant irrespective of the frequency (corresponding to the case of no peeling in FIG. 3), and the spectral characteristic of the test piece S2 has the reflectance characteristic vibrating depending on the frequency and the frequency characteristic. It increases almost proportionally (corresponding to the case of peeling in FIG. 3).

<< Theoretical Support of Example 1 >> Next, test pieces
Taking the cases of S1 and S2 as an example, a theoretical consideration will be given to the first embodiment of the present invention. 4 and 5 are enlarged cross-sectional views showing the surfaces of the test pieces S1 and S2 respectively modeled, where Pi is an incident ultrasonic wave (incident wave), Po is a reflected ultrasonic wave (reflected wave), P ₁ ,
P ₂ , P ₃ , ... Are components for multiple reflection of the reflected wave Po, Wa
Is a water film interposed between the substrate 21 and the thin film 22, and hf is the thin film 22.
, Hw is the thickness of the water film Wa.

Here, an ultrasonic wave Pi composed of plane harmonic waves is used.
2 shows the reflection characteristics when is incident on the thin film 22 vertically. or,
For the sake of convenience, the reflection angle of the reflected wave Po is markedly shown, but it goes without saying that the angle is actually close to zero. A plane harmonic wave is a plane perpendicular to the traveling direction of the wave,
A wave in which displacement and stress are constant regardless of location and change with a sine function with respect to time.

In FIG. 4, the water W and the substrate 21 are approximated by a semi-infinite body, and a thin film 22 having a uniform thickness hf is provided between them.
Exists. Therefore, the incident wave Pi is a thin film from the water W side.
When it enters the thin film 22, multiple reflection occurs in the thin film 22, and the reflected wave Po emitted from the surface of the thin film 22 is formed by superposing a plurality of plane wave components P ₁ , P ₂ , ... Will be things. On the other hand, in FIG. 5, the thin film 22 and the substrate
Since the water film Wa having a uniform thickness hw is interposed between the thin film 22 and the film 21, multiple reflection occurs in the thin film 22 and the water film Wa.

Here, the angular frequency of the incident wave Pi is ω, and the thin film
The sound velocity at 22 is cf and the sound velocity in water W is cw, and the dimensionless quantities θf and θw are defined by the following equations.

Θf = (ω / cf) hf (1) θw = (ω / cw) hw (2)

Θf and θw given by the above equations are the phase lags of the plane harmonics when they pass through the thin film 22 or the water film Wa, and represent the degree of each film thickness with respect to the wavelength of the plane harmonics. Using the dimensionless quantities θf and θw, the reflectances R1 and R2 for the respective test pieces S1 and S2 are calculated as follows. However, j = (-1) ^1/2 .

R1 = | {r _wf · exp (2jθf) + r _fs } / {exp (2jθf) + r _wf r _fs } | (3) R2 = | {r _wf · exp (2jθf) + r ′ _fs } / { exp (2jθf) + r _wf r ′ _fs } | ... (4) r ′ _fs = {r _fw・ exp (2jθw) + r _ws } / {exp (2jθw) + r _fw r _ws }… (5)

Here, r _AB is the reflectance when the ultrasonic wave Pi is incident on the semi-infinite medium A to B, and r ′ _fs is
This is the reflectance of ultrasonic waves at the interface between the thin film 22 and the water film Wa, which is obtained in consideration of multiple reflections in the water film Wa. Generally, the reflectance r _AB is given by the following equation, where the acoustic impedances of the media A and B are Z _A and Z _B , respectively.

R _AB = (Z _B −Z _A ) / (Z _A + Z _B ) ... (6)

The subscripts w, f and s of r instead of A and B indicate that the medium is water W, the thin film 22 and the substrate 21, respectively. In particular, the thickness hf of the thin film 22 is sufficiently smaller than the wavelength of the incident wave Pi, and the second or more terms of θf (θf ² , θf
⁽³ , ...) Can be ignored, the equations (3) and (4) can be modified as follows.

R1 = r _ws (7) R2 = r _ws −2r _wf {(1-r ² _ws ) / (1-r ² _wf )} θf · sin (2jθw) (8)

Here, r _ws gives the reflectance when a plane harmonic wave is incident on the substrate 21 from the water W, that is, the reflectance for the reference test piece S0 without the thin film 22. From equation (7), it can be seen that the reflectance R1 for the test piece S1 is constant irrespective of the frequency and is equal to the reflectance for the reference test piece S0 within a range in which θf is sufficiently small. On the other hand, from the equation (8), the second term on the right side oscillates the reflectance at a cycle of (c _w / 2h _w ) with respect to frequency
Also, it can be seen that the amplitude of this vibration increases in proportion to the frequency.

Therefore, similar to the above-mentioned experimental results, it is proved that the relationship matches the relationship shown in FIG. For example, hf
= 5 μm, c _f = 18.1 km / sec, and the frequency is 25 MHz, it can be seen from the equation (1) that θf = 4.34 × 10 ⁻² , and θf is within the range satisfying the above conditions.

Now, the process of deriving the expressions (3) to (5) will be described in detail. In general, the transmissivity t _AB when an ultrasonic wave is incident on the semi-infinite mediums A to B is expressed as follows using the acoustic impedances Z _A and Z _B of each medium.

T _AB = 2Z _B / (Z _A + Z _B ) ... (A1)

From the expressions (A1) and (6), the following relational expressions regarding r _AB and t _AB are obtained.

1 + r _AB = t _AB (A2) r _AB = -r _BA (A2)

As shown in FIG. 4, the incident wave P on the test piece S1
i is multiply reflected in the thin film 22, and the reflected wave Po is a combination of reflected wave components Pn (n = 1, 2, ...) Having different propagation paths. When the phase delay of the reflected wave Po with respect to the incident wave Pi is α ₁ , the relationship with the reflectance R1 with respect to the test piece S1 is
It looks like this:

R1 · exp (−jα ₁ ) = Po / Pi (A3)

Therefore, when the reflected wave component Pn is expressed by using r _AB and t _AB , and these are superposed, the formula (A3) becomes as follows. Note that θf is the phase delay defined above.

R1 · exp (-jα ₁ ) = r _wf + t _wf r _fs t _fw · exp (-2jθf) × Σ {r _fs r _fw · exp (-2jθf)} ⁿ … (A4)

In the formula (A4), the term of the summation formula (Σ) is n =
The sum operation for 0 to ∞ is shown. Where | r _fs r _fw · exp
Considering (−2jθf) | <1, the terms of the summation formula of n = 0 to ∞ in the formula (A4) are as follows.

Σ {r _fs r _fw · exp (-2jθf)} ⁿ = exp (2jθf) / {exp (2jθf) + r _wf r _fs } ... (A5)

By substituting the expression (A5) into the expression (A4), the following expression is obtained.

R1 · exp (-jα ₁ ) = {r _wf · exp (2jθf) + r _fs } / {exp (2jθf) + r _wf r _fs } (A6)

On the other hand, in the case of the test piece S2, multiple reflection occurs in the thin film 22 and the water film Wa as shown in FIG. 5, but first, focusing on only the multiple reflection in the water film Wa, the water film Wa The reflectance _{r'fs is obtained} by the same method as the equation (A6) as follows.

R ′ _fs = {r _fw · exp (2jθw) + r _ws } / {exp (2jθw) + r _fw r _ws } ... (A7)

Next, focusing on the multiple reflection in the thin film 22, the reflectance R2 for the test piece S2 is as follows.

R2 ・ exp (-jα ₂ ) = r _wf + t _wf・ r ' _fs t _fw・ exp (-2jθf) × Σ {r' _fs r _fw・ exp (-2jθf)} ⁿ = {r _wf・exp (2jθf) + r ′ _fs } / {exp (2jθf) + r _wf · r ′ _fs }… (A8)

In the equation (A8), α ₂ is the phase delay of the reflected wave Po with respect to the incident wave Pi. As described above, the model analysis using the plane harmonic wave can theoretically consider the relationship between the reflectance and the frequency of the ultrasonic wave P due to vertical incidence.

By the way, in FIG. 5, the thickness h of the water film Wa is
When w is made as small as possible, it is possible to simulate a state in which there is no peeling and the adhesive strength is reduced. However, the reflectance with respect to the test piece S2 at this time is equal to the reflectance with respect to the test piece S1 having good adhesion strength from the equation (8). Therefore, with the method of vertically injecting the ultrasonic wave Pi as in Example 1, peeling can be detected, but the difference in adhesion strength cannot be measured and evaluated.

This is because when the thickness hw of the water film Wa is sufficiently smaller than the ultrasonic wavelength, the vertical stress and the vertical displacement in the water film Wa are affected by the multiple reflection in the water film Wa. This is because the vertical stress and the vertical displacement at the interface when the film Wa is not present are substantially equal to each other. Thus, the analysis method based on the normal stress at the interface is not suitable for measuring and evaluating the bond strength. However, if attention is paid to the shear stress at the interface, it can be seen that the adhesion strength can be evaluated based on the transmittance analysis by the tilt angle incidence.

Example 2. Next, a second embodiment of the present invention for the purpose of evaluating adhesion strength will be described with reference to the drawings. In this case, a difference is that ultrasonic waves are transmitted and received at a tilt angle with respect to the surface of the subject 9 by a pair of probes arranged on both sides of the subject 9, but the same device as in FIG. Can be used.

FIG. 6 is a side view showing in detail the measuring section of the second embodiment of the present invention, and other constitutions not shown are as shown in FIG. In FIG. 6, reference numeral 61 is a transmitting (first) probe for the transmitted wave Pi to the subject 9, and 62 is a receiving (second) probe for the received wave Pt transmitted through the subject 9. .. Here, the ultrasonic frequency for measurement is 25 MHz,
A flat type probe or Panametrics V324 (see Table 1) is used as the transmitting probe 61, and a focus type probe or Hitachi I2-2504T is used as the receiving probe 62.

The two probes 61 and 62 are fixed so as to face each other so that their central axes coincide with each other, and the subject 9 is positioned between the respective probes 61 and 62 with respect to the central axis. For example, it is fixed by a jig with an inclination of 13 °. Further, the subject 9 is installed with the thin film 22 side facing the receiving probe 62 side, and the focus position of the probe 62 is adjusted within the thin film 22. This allows the substrate 21
The vibration of the thin film 22 excited by the ultrasonic wave Pi which is incident from the bottom surface at an inclination angle θo of 13 ° can be measured by the transmitted wave Pt. The inclination angle θo (= 13 °) is calculated by
It is a value approximately at the center between the critical angle of the longitudinal wave and the critical angle of the transverse wave, and only the transverse wave propagates in the substrate 21.

Next, a second embodiment of the present invention will be described with reference to FIGS. [Transmission Step] First, a transmission wave Pi having a predetermined test frequency (25 MHz) is transmitted from the probe 61 to the subject 9 at an inclination angle θo. [Reception Step] Next, the transmitted wave Pt of the transmitted wave Pi is received by the probe 62, becomes waveform data via the pulsar receiver 11 in the same manner as described above, is sampled by the digital oscilloscope 12, and then is transmitted to the microcomputer 1. Is entered.

[FFT analysis step] The microcomputer 1 determines the transmitted wave Pt based on the sampling data.
The frequency characteristic of is analyzed by FFT.

At this time, if a strong chemical bond is sufficiently formed between the substrate 21 and the thin film 22, the shear stress due to the vibration of the ultrasonic wave Pi is sufficiently transmitted to the thin film 22, If a strong chemical bond is not formed, slippage by the ultrasonic wave Pi is allowed to some extent at the interface, and shear stress is difficult to be transmitted to the thin film 22.

[Frequency Characteristic Comparison Step and Adhesion Strength Evaluation Step] Therefore, by comparing the frequency characteristic of the transmitted wave Pt with respect to the subject 9 with the frequency characteristic of the transmitted wave with respect to only the substrate 21, the transmitted wave Pt of the subject 9 is compared. When the frequency characteristic differs from the frequency characteristic of the transmitted wave with respect to only the substrate 21 by a predetermined amplitude or more, it can be determined that the adhesion strength between the substrate 21 and the thin film 22 is good.

That is, the difference in response to the transmitted wave of the thin film 22 having different adhesion strength is obtained by measuring the transmitted wave Pt of the ultrasonic wave obliquely incident from the probe 61 with the probe 62, and only the substrate 21 is obtained. Pt for the frequency characteristics in the case of
Evaluate the difference from the frequency characteristics of.

FIG. 7 is a characteristic diagram showing an example of a result obtained by converting the waveform data of the transmitted wave Pt into the spectrum space by the FFT, and shows an average value of 512 samplings, for example. In FIG. 7, the vertical axis represents the ratio of the spectrum intensity to the reference test piece S0, the horizontal axis represents the frequency, the solid line represents the frequency characteristic when the adhesion strength is good, and the broken line represents the frequency characteristic when the adhesion strength is poor.

From FIG. 7, when the adhesion strength is good (solid line), in the vicinity of 20 MHz near the center frequency of the ultrasonic wave Pi,
It can be seen that the spectral intensity (corresponding to the transmittance) is increased by about 1.5 times as compared with the case of the reference test piece S0. On the other hand, when the adhesion strength is poor (broken line), the spectral strength is almost the same as that of the reference test piece S0.

<< Experimental Support of Example 2 >> Here, based on an experiment using the reference test piece S0 and the test piece S1 having good adhesive strength, and the test piece S3 having poor adhesive strength,
The proof of is explained. In addition, the test piece S3 did not scratch the substrate 21 before synthesizing the thin film 22 under the conditions shown in Table 2, and sprayed diamond powder (particle size 1 μm or less) as a seed crystal to form the substrate 21 and the thin film 22. And are weakly bonded test pieces. The method for spraying the diamond powder can be realized by once immersing the substrate 21 in acetone in which the diamond powder is suspended by an ultrasonic cleaner and then drying the substrate 21.

FIGS. 8 (a) and 8 (b) are explanatory views showing the difference in adhesion strength between the substrate 21 and the thin film 22 on the test pieces S1 and S3, and 81 is a Vickers indenter pressed into the thin film 22 with a load of 49N. At this time, the indentation 82 is a peeling region formed around the indentation 81. From FIG. 8, the area of the peeled region 82 is about 3 times larger in the case of the test piece S3 (b) than in the case of the test piece S1 (a), and the adhesion strength of the test piece S3 is larger than that of the test piece S1. You can see that it is decreasing.

Here, in the case of the test piece S3, since the thin film 22 was synthesized from the seed crystal, a strong chemical bond was not formed between the substrate 21 and the thin film 22, and the thin film 22 was not formed at the interface. Sliding by ultrasonic waves is allowed, making it difficult to transmit shear stress. On the other hand, in the case of the test piece S1, since the thin film 22 is firmly bonded to the substrate 21 at the point where the nuclei are generated, it is easy to transmit the shear stress.

By measuring the test pieces S1 and S3 under the same test conditions as described above without changing the condition settings, the same results as in FIG. 7 can be obtained. At this time, the frequency characteristic of the transmitted wave Pt for the test piece S1 corresponds to the solid line in FIG. 7, and the frequency characteristic of the transmitted wave Pt for the test piece S3 corresponds to the broken line.

<< Theoretical Support of Example 2 >> Next, the theoretical consideration of Example 2 of the present invention will be given by taking the case of the test pieces S1 and S3 having the same external structure as an example. Figure 9 is an enlarged sectional view illustrating a modeled ultrasonic propagation path to the layer structure of the specimen S1 and S3, ultrasonic Pi is the transmitted wave, Pt ₁ ~Pt ₁₀ is to complicated reflection and transmission at each interface Ingredient, X ₁
Is the coordinate axis that coincides with the interface between the substrate 21 and the thin film 22, and X ₂ is X ₁
Is a coordinate axis of the substrate 21 in the thickness direction orthogonal to, hf is an X ₂ coordinate of the interface between the water W and the thin film 22, and −hs is an X ₂ coordinate of the interface between the substrate 21 and the water W.

In this way, the modeled test piece S1 and
An orthogonal coordinate system (X ₁ , X ₂ ) is introduced with respect to S3 so that the X ₁ axis coincides with the interface between the thin film 22 and the substrate 21. Where the thin film 2
2 and the substrate 21 have uniform thicknesses hf and hs, respectively, and there are layers of water W above and below which are approximated by a semi-infinite body. Therefore, the coordinates of each interface between the water W and the thin film 22 and the substrate 21. Are respectively represented by X ₂ = hf, X ₂ = 0, and X ₂ = -hs.

Now, let us consider a case where an ultrasonic wave Pi consisting of continuous longitudinal plane harmonics of angular frequency ω enters the substrate 21 from the water W at an incident angle θ ₀ as shown in FIG. At this time, plane ultrasonic waves of longitudinal waves and transverse waves are generated in the substrate 21 and the thin film 22, and plane ultrasonic waves of only longitudinal waves are generated in the water W. still,
The motion of the particles due to the generated plane harmonics is limited to the X ₁ X ₂ plane, and the generated plane harmonics are reflected intricately at each interface and are generated innumerably in the layer composed of the substrate 21 and the thin film 22. It will be.

However, these plane harmonics are four types of plane harmonics in which the vibration direction and the propagation direction of particles are different, that is, transmitted P wave, transmitted S wave, reflected P wave and reflected S wave.
Can be classified into waves. Of these, when the same types of plane harmonics are superposed and arranged, as shown in Fig. 10,
It suffices to consider the types of plane harmonic waves Ptn (n = 1, 2, ..., 10). Here, Pt ₁ , Pt ₄ and Pt ₈ are reflected P waves, Pt
₅ and Pt ₉ are reflected S waves, Pt ₂ , Pt ₆ and Pt ₁₀ are transmitted P waves.
Waves, Pt ₃ and Pt ₇ , represent transmitted S-waves.

The component u _i ⁽ⁿ⁾ of the displacement of each plane harmonic wave Ptn in the Xi (i = 1, 2) direction is the component of the unit vector in the propagation direction in the Xi direction n _i ⁽ⁿ⁾ , and the component of the vibration direction of the particle is When the component of the unit vector in the Xi direction is ν _i ⁽ⁿ⁾ , the displacement amplitude is M ⁽ⁿ⁾ , and the wave number is k ⁽ⁿ⁾ , it is expressed by the following equation.

U _i ⁽ⁿ⁾ = M ⁽ⁿ⁾ ν _i ⁽ⁿ⁾ exp (jξ ⁽ⁿ⁾ ) (9)

In equation (9), ξ ⁽ⁿ⁾ is expressed as follows.

Ξ ⁽ⁿ⁾ = ωt−k ⁽ⁿ⁾ n _l ⁽ⁿ⁾ X _l (10)

In equations (9) and (10), the subscripts follow the summing convention, and n _i ⁽ⁿ⁾ and ν _i ⁽ⁿ⁾ are X ₂
When the angle formed by the axis and the propagation direction is θn (n = 0, 1, ..., 10), it is given by the following equation.

N ₁ ⁽ⁿ⁾ = sin θn, n ₂ ⁽ⁿ⁾ = cos θn (11) ν ₁ ⁽ⁿ⁾ = sin θn, ν ₂ ⁽ⁿ⁾ = cos θn (when Ptn is a longitudinal wave) ... (12) ν ₁ ⁽ⁿ⁾ = -cos θn, ν ₂ ⁽ⁿ⁾ = sin θn (when Ptn is a transverse wave) ... (12)

Here, the acoustic velocities of the longitudinal wave and the transverse wave in the medium A are c _A and c _A2 , respectively, and θ _A1 and θ
Define _A2 (A = w, f, s). Incidentally, w, f and s correspond to the water W, the thin film 22 and the substrate 21, respectively.

Sin θ ₀ / c _w = sin θ _A1 / c _A = sin θ _A2 / c _A2 (13)

However, 0 ≦ θ _AQ ≦ π / 2 (A = w, f, s; Q
= 1, 2), and the relationship between θn and θ _AQ is as follows.

Θ ₀ = θw ₁ , θ ₁ = π−θw ₁ , θ ₂ = θs ₁ (14) θ ₃ = θs ₂ , θ ₄ = π−θs ₁ , θ ₅ = π−θs ₂ (14) ) θ ₆ = θf ₁ , θ ₇ = θf ₂ , θ ₈ = π−θf ₁ (14) θ ₉ = π−θf ₂ , θ ₁₀ = θw ₁ (14)

In this case, since the ultrasonic wave Pi is obliquely incident, the displacement amplitude M from the multiple reflection path of each plane harmonic wave Ptn.
It is difficult to find ⁽ⁿ⁾ . Therefore, the displacement amplitude M ⁽ⁿ⁾
As an unknown quantity, each interface (X ₂ = −hs, X ₂ = 0, X ₂ = h
Stress tensor τ _i2 ⁽ⁿ⁾ (i ＝
1, 2) and the displacement amplitude u _i ⁽ⁿ⁾ . X
₂ = -hs and X ₂ = hf are both a interface between the solid and the liquid, irrespective of the test pieces S1 and S3, below is established (15) and (16).

U ₂ ⁽⁰⁾ + u ₂ ⁽¹⁾ = u ₂ ⁽²⁾ + u ₂ ⁽³⁾ + u ₂ ⁽⁴⁾ + u ₂ ⁽⁵⁾ ... (15) τ ₁₂ ⁽²⁾ + τ ₁₂ ⁽³⁾ + τ ₁₂ ⁽⁴⁾ + τ ₁₂ ⁽⁵⁾ = 0… (15) τ ₂₂ ⁽⁰⁾ ＋ τ ₂₂ ⁽¹⁾ ＝ τ ₂₂ ⁽²⁾ ＋ τ ₂₂ ⁽³⁾ ＋ τ ₂₂ ⁽⁴⁾ ＋ τ ₂₂ ⁽⁵⁾ … (15) ( X ₂ = -hs)

U ₂ ⁽⁶⁾ + u ₂ ⁽⁷⁾ + u ₂ ⁽⁸⁾ + u ₂ ⁽⁹⁾ = u ₂ ⁽¹⁰⁾ … (16) τ ₁₂ ⁽⁶⁾ + τ ₁₂ ⁽⁷⁾ + τ ₁₂ ⁽⁸⁾ + τ ₁₂ ⁽⁹⁾ = 0… (16) τ ₂₂ ⁽⁶⁾ ＋ τ ₂₂ ⁽⁷⁾ ＋ τ ₂₂ ⁽⁸⁾ ＋ τ ₂₂ ⁽⁹⁾ ＝ τ ₂₂ ⁽¹⁰⁾ … (16) (at X ₂ ＝ hf)

At the interface of X ₂ = 0, the boundary conditions of the test piece S1 and the test piece S3 are different, and the test piece having a high thin film bonding property.
In the case of S1, both displacement and stress are continuous above and below the interface, so the boundary condition is as shown in equation (17) below.

U ₁ ⁽²⁾ + u ₁ ⁽³⁾ + u ₁ ⁽⁴⁾ + u ₁ ⁽⁵⁾ = u ₁ ⁽⁶⁾ + u ₁ ⁽⁷⁾ + u ₁ ⁽⁸⁾ + u ₁ ⁽⁹⁾ … (17) u ₂ ⁽²⁾ + u ₂ ⁽³⁾ + u ₂ ⁽⁴⁾ + u ₂ ⁽⁵⁾ = u ₂ ⁽⁶⁾ + u ₂ ⁽⁷⁾ + u ₂ ⁽⁸⁾ + u ₂ ^{(9 )} (17) τ ₁₂ ⁽²⁾ + τ ₁₂ ⁽³⁾ + τ ₁₂ ⁽⁴⁾ + τ ₁₂ ⁽⁵⁾ = τ ₁₂ ⁽⁶⁾ + τ ₁₂ ⁽⁷⁾ + τ ₁₂ ⁽⁸⁾ + τ ₁₂ ^{( 9)} … (17) τ ₂₂ ⁽²⁾ + τ ₂₂ ⁽³⁾ + τ ₂₂ ⁽⁴⁾ + τ ₂₂ ⁽⁵⁾ = τ ₂₂ ⁽⁶⁾ + τ ₂₂ ⁽⁷⁾ + τ ₂₂ ⁽⁸⁾ + τ ₂₂ ⁽⁹⁾ … (17) (at X ₂ = 0)

On the other hand, in the case of the test piece S3 having a low thin film bondability, the boundary condition is expressed by the following expression (18) considering the situation that the shear stress cannot be transmitted at the interface.

U ₂ ⁽²⁾ + u ₂ ⁽³⁾ + u ₂ ⁽⁴⁾ + u ₂ ⁽⁵⁾ = u ₂ ⁽⁶⁾ + u ₂ ⁽⁷⁾ + u ₂ ⁽⁸⁾ + u ₂ ⁽⁹⁾ ... (18) τ ₁₂ ⁽²⁾ + τ ₁₂ ⁽³⁾ + τ ₁₂ ⁽⁴⁾ + τ ₁₂ ⁽⁵⁾ = τ ₁₂ ⁽⁶⁾ + τ ₁₂ ⁽⁷⁾ + τ ₁₂ ⁽⁸⁾ + τ ₁₂ ^{(9 )} = 0 ... (18) τ ₂₂ ⁽²⁾ + τ ₂₂ ⁽³⁾ + τ ₂₂ ⁽⁴⁾ + τ ₂₂ ⁽⁵⁾ ＝ τ ₂₂ ⁽⁶⁾ + τ ₂₂ ⁽⁷⁾ + τ ₂₂ ⁽⁸⁾ + τ ₂₂ ⁽⁹⁾ … (18) (at X ₂ = 0)

The stress tensor τ _ij ⁽ⁿ⁾ is given by the following equation from the constitutive equation of isotropic elastic body.

Τ _ij ⁽ⁿ⁾ = λ _A Emm ⁽ⁿ⁾ δij + 2μ _A Eij ⁽ⁿ⁾ (19)

However, Eij ⁽ⁿ⁾ is a strain tensor and is expressed as follows.

[0103] _{^{Eij (n) = (∂u i}} (n) / ∂Xj + ∂u j (n) / ∂Xi) / 2 ... (20)

In the equation (19), δij is the Kronecker delta, and λ _A and μ _A are the Lame constants in the medium A.
Substituting the above equation (9) into equations (19) and (20), τ _ij ⁽ⁿ⁾
Is expressed by the following equation.

Τ _ij ⁽ⁿ⁾ = −jM ⁽ⁿ⁾ {λ _A ν _m ⁽ⁿ⁾ _nm ⁽ⁿ⁾ δij + μ _A (ν _i ⁽ⁿ⁾ n _j ⁽ⁿ⁾ + ν _j ⁽ⁿ⁾ n _i ⁽ⁿ⁾ )} × k ⁽ⁿ⁾ exp (jξ ⁽ⁿ⁾ )… (21)

Substituting equations (11) and (12) into equation (21),
τ _i2 ⁽ⁿ⁾ (i = 1, 2) is given by the following equation depending on the type of plane harmonic wave.

Τ ₁₂ ⁽ⁿ⁾ = −jM ⁽ⁿ⁾ ωZ _A2 (c _A2 / c _A ) sin (2θ _A1 ) exp (jξ ⁽ⁿ⁾ ) ... (22) (incident wave, transmitted P wave) τ ₁₂ ^{( n)} = jM ⁽ⁿ⁾ ωZ _A2・ cos (2θ _A2 ) exp (jξ ⁽ⁿ⁾ )… (22) (transmitted S wave) τ ₁₂ ⁽ⁿ⁾ = jM ⁽ⁿ⁾ ωZ _A2 (c _A2 / c _A ). sin (2θ _A1 ) exp (jξ ⁽ⁿ⁾ )… (22) (Reflected P wave) τ ₁₂ ⁽ⁿ⁾ ＝ jM ⁽ⁿ⁾ ωZ _A2 · cos (2θ _A2 ) exp (jξ ⁽ⁿ⁾ )… (22) (Reflected S wave)

Τ ₂₂ ⁽ⁿ⁾ = −jM ⁽ⁿ⁾ ωZ _A · cos (2θ _A2 ) exp (jξ ⁽ⁿ⁾ ) ... (23) (incident wave, transmitted P wave) τ ₂₂ ⁽ⁿ⁾ = −jM ^{( n)} ωZ _A2・ sin (2θ _A2 ) exp (jξ ⁽ⁿ⁾ ) ・ ・ ・ (23) (Transmission S wave) τ ₂₂ ⁽ⁿ⁾ = −jM ⁽ⁿ⁾ ωZ _A・ cos (2θ _A2 ) exp (jξ ^{(n )} ) (23) (Reflected P-wave) τ ₂₂ ⁽ⁿ⁾ = jM ⁽ⁿ⁾ ωZ _A2・ sin (2θ _A2 ) exp (jξ ⁽ⁿ⁾ )… (23) (Reflected S-wave)

Here, Z _A and Z _A2 are acoustic impedances for the longitudinal wave and the transverse wave in the medium A and are defined by the following equation.

Z _A = (λ _A +2 μ _A ) / c _A (24) Z _A2 = μ _A / c _A2 (24)

Equations (15), (18), (9), (22) and (23)
Substituting the equation, M for test pieces S1 and S3 respectively
10 independent relations for ⁽ⁿ⁾ (n = 0, 1, ... 10) are obtained. Accordingly, if the displacement amplitude M ⁽⁰⁾ of the incident wave is known, the displacement amplitude M of each plane harmonic wave Ptn, which is 10 unknown quantities, is known.
⁽ⁿ⁾ (n = 0, 1, ... 10) can be determined.

The results of calculating the transmittance (absolute value of M ⁽ⁿ⁾ / M ^{(0) )} for each of the test pieces S1 and S3 by the above method are shown in FIG.
Shown in 10. The acoustic constants shown in Table 4 were used for the calculation for obtaining the transmittance characteristics in FIG.

Table 4: Acoustic constant substances Water Diamond Si (Silicone) Longitudinal wave acoustic impedance 1.50 63.50 19.64 (× 10 ⁶ kg / m ² seconds) Transverse wave acoustic impedance 0.0 43.13 13.61 (× 10 ⁶ kg / m ² seconds) Longitudinal wave speed (km / s) 1.50 18.10 8.43 Transverse wave speed (km / s) 0.0 12.30 5.84

In FIG. 10, the vertical axis represents the ratio of the transmittance to the reference test piece S0, that is, the spectrum intensity ratio, and the horizontal axis represents the frequency. Here, focusing on the frequency around 20 MHz, the transmittance for the test piece S1 is higher than that for the test piece S3. It can be seen that this tendency matches the result of the frequency characteristic shown in FIG.

As described above, based on the analysis of the transmittance characteristic due to the incident angle of incidence of the plane harmonic wave, the transmittance when the adhesion strength of the thin film 22 is high becomes higher than the transmittance when the adhesion strength is lowered. I understand. Therefore, it is possible to theoretically prove that the bond strength can be evaluated.

Although the focus type probe is used as the transmitting and receiving probe 7 in the first embodiment, a flat type probe may be used. Moreover, although the probe whose test frequency is 10 MHz and 25 MHz is used, the probe of other test frequency may be used, and the spectrum intensity of the desired frequency band can be obtained by using three or more types of probes having different test frequencies. May be analyzed.

In the second embodiment, the transmitting probe 61 is used.
A flat probe was used as the ultrasonic wave Pi and the ultrasonic wave Pi was incident from the substrate 21 side. However, a focus probe may be used as the ultrasonic wave Pi.
May be incident from the thin film 22 side.

Further, for the experimental support of each example, the test pieces S1 to S3 having the same specifications as the object 9 to be measured were used, but these test pieces S1 to S3 have the same specifications as the object 9. It is not necessary to set the reference test piece S0 to the substrate 21 of the subject 9
It should have the same specifications as. Furthermore, the theoretical proof of Example 1 and Example 2 related to the equations (1) to (24) is one model analysis example for explaining and interpreting each experimental proof, and other theoretical proofs. Needless to say, it can be substantiated.

[0119]

As described above, according to the present invention, a step of transmitting an ultrasonic wave having a predetermined center frequency perpendicularly to a thin film from a single probe and a reflected wave of the ultrasonic wave are detected. The measurement sequence consisting of the step of receiving by the child and the step of performing FFT analysis of the frequency characteristic near the center frequency of the reflected wave is performed for a plurality of probes having different center frequencies, and the frequency characteristic of the reflected wave is equal to or larger than a predetermined amplitude. Since it is determined that peeling exists between the substrate and the thin film when vibration is included, there is an effect that a thin film peeling detection method with improved reliability can be obtained.

Further, according to the present invention, the step of transmitting an ultrasonic wave having a predetermined center frequency from the first probe to the subject at an inclination angle, and the transmitted wave of the ultrasonic wave to the second probe. The steps of receiving by a tentacle, FFT-analyzing the frequency characteristic of the transmitted wave, and comparing the frequency characteristic of the transmitted wave for the subject with the frequency characteristic of the transmitted wave for the substrate only, When the frequency characteristics of the are different from the frequency characteristics of the transmitted wave only to the substrate by more than a predetermined amplitude, it is determined that the adhesion strength between the substrate and the thin film is good. There is an effect that a strength evaluation method can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing an ultrasonic exploration imaging apparatus for realizing Embodiments 1 and 2 of the present invention.

FIG. 2 is a side view showing in detail an ultrasonic wave irradiation unit in FIG.

FIG. 3 is a characteristic diagram showing an FFT analysis result according to the first embodiment of the present invention.

FIG. 4 is an enlarged cross-sectional view showing a model of a test piece S1 used for experimental support of Example 1 of the present invention together with an ultrasonic wave path.

FIG. 5 is an enlarged cross-sectional view showing a model of a test piece S2 used for experimental support of Example 1 of the present invention together with an ultrasonic path.

FIG. 6 is a side view showing in detail an ultrasonic wave irradiating section of the ultrasonic sounding imaging device for realizing the second embodiment of the present invention.

FIG. 7 is a characteristic diagram showing an FFT analysis result according to the second embodiment of the present invention.

FIG. 8 is an explanatory diagram showing the adhesion strength of test pieces S1 and S3 used for experimental backing of Example 2 of the present invention.

FIG. 9 is an enlarged cross-sectional view showing test pieces S1 and S3 used for experimental support of Example 2 of the present invention, modeled together with an ultrasonic path.

FIG. 10 is a characteristic diagram showing a spectrum analysis result based on theoretical support of Example 2 of the present invention.

[Explanation of symbols]

 7, 61, 62 Probe 9 Subject 21 Substrate 22 Thin film P, Pi Incident wave (incident ultrasonic wave) Po Reflected wave (reflected ultrasonic wave) Pt Transmitted wave (transmitted ultrasonic wave) θo Inclination angle

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Masumi Saka, 1-8-1, Minamiyoshinari, Aoba-ku, Sendai-shi, Miyagi Prefecture (72) Inventor Kiyoshi Hoshikawa 67, Kawauchiyama House, 67, Kawauchi-yama, Aoba-ku, Sendai City, Miyagi Prefecture Room 1 72) Inventor Yoshito Izumi 2-20-13 Higashi-Nakano, Nakano-ku, Tokyo (72) Inventor Hideki Fujita 4-171-11 Makuhari-Hongo, Chiba-shi, Chiba K AWABE 439-306

Claims (2)

[Claims] 1. A surface of a subject having a substrate and a thin film formed on the substrate is irradiated with ultrasonic waves, and peeling between the substrate and the thin film is detected based on a reflected wave of the ultrasonic waves. A step of transmitting ultrasonic waves having a predetermined center frequency perpendicularly to the thin film from a single probe; and a step of receiving reflected waves of the ultrasonic waves by the probe. FFT the frequency characteristics of the reflected wave near the center frequency
A step of analyzing, and performing a measurement sequence consisting of a plurality of probes having different center frequencies, and when the frequency characteristics of the reflected wave include vibration with a predetermined amplitude or more, between the substrate and the thin film. A thin film peeling detection method for determining the presence of peeling. 2. A subject having a substrate and a thin film formed on the substrate is irradiated with ultrasonic waves, and the adhesion strength between the substrate and the thin film is evaluated based on the transmitted wave of the ultrasonic waves. A method of transmitting an ultrasonic wave having a predetermined center frequency from the first probe to the subject at an inclination angle, and receiving a transmitted wave of the ultrasonic wave by a second probe. And a step of FFT-analyzing the frequency characteristic of the transmitted wave, and a step of comparing the frequency characteristic of the transmitted wave with respect to the subject with the frequency characteristic of the transmitted wave with respect to only the substrate. Adhesion strength evaluation of a thin film that determines that the adhesion strength between the substrate and the thin film is good when the frequency characteristics of the wave differ from the frequency characteristics of the transmitted wave for the substrate only by a predetermined amplitude or more Law.