KR101656185B1

KR101656185B1 - A signal analyzing method of a acoustic microscope

Info

Publication number: KR101656185B1
Application number: KR1020150077699A
Authority: KR
Inventors: 박익근; 박태성; 곽동열
Original assignee: 서울과학기술대학교 산학협력단
Priority date: 2015-06-02
Filing date: 2015-06-02
Publication date: 2016-09-09

Abstract

The present invention discloses a signal analysis method of an ultrasonic microscope. A method for analyzing signals incident and reflected on a sample using an ultrasonic beam of an ultrasonic microscope having a transducer, a buffer rod and a lens as an intermediate medium, the method comprising the steps of: (a) An acoustic lens is designed; (b) selecting a coupling agent on a simulation tool menu; (c) calculating a focal distance of the sonic and acoustic beams in the coupling medium; (d) simulating the output voltage of the transducer according to the focal distance of the beam; And (e) separating the surface wave component from the simulated output voltage curve and calculating the velocity of the surface wave component to extract the elasticity information of the sample. According to the present invention, it is possible to reduce the time and expense required to prepare and observe the sample, to overcome the space and environmental constraints, and to accurately identify the cause of the error in the signal analysis process .

Description

[0001] The present invention relates to a signal analyzing method of an acoustic microscope,

The present invention relates to a signal analysis method, and more particularly, to a signal analysis method of an ultrasonic microscope capable of precisely measuring the velocity of a Rayleigh wave generated in an ultrasonic microscope and theoretically simulating and analyzing the material characteristic of the nanoscale using ultrasonic waves &Lt; / RTI >

Nanotechnology refers to the art of synthesizing, assembling, controlling, or measuring and characterizing materials at small size units such as atoms or molecules.

Nanotechnology is the core technology that will lead the new industry in the 21st century, leading to economic growth and increasingly needed as breakthrough technology to overcome the limit of existing technology.

For this reason, nanotechnology is being applied to a wide variety of industries including biotechnology, chemistry, energy, semiconductors, automobiles, solar cells, information communication, and displays (flexible substrates) .

In Korea, we have already established the Nanotechnology Comprehensive Plan since 2001 to secure future technology and to take the lead in future growth by developing nanotechnology.

In the Nanotechnology Comprehensive Plan, the six nanotechnology fields (nanomaterials, nanodevices, nanobio, process and equipment measurement, energy environment, and nanostability) are classified.

In particular, in the fields of process and equipment measurement, nanotechnology has played a role in the measurement technology compared to the existing industry in order to cope with the analysis of nanotechnology and products as the development of nanotechnology exceeds the resolution / measurement and detection limit of analysis and measurement equipment Is becoming more important.

However, the measurement technique of the nanoscale region requires a more precise measurement technique because the unit constituting the material becomes smaller at the nanoscale, and not only the surface characteristics of the material but also the physical properties play a significant role in the nanomaterial characteristics.

In general, nanotechnology involves forming various dielectric thin films, semiconductor thin films, and metal thin films selectively on a semiconductor substrate or glass.

That is, it is a series of processes to manufacture devices with desired characteristics by using electrical, chemical, and characteristics inherent to the thin film or by diffusion or ion implantation process to change the electrical characteristics of the semiconductor.

In order to apply these thin films to specific applications, it is necessary to precisely measure the thickness, composition, roughness, and other physical and optical properties of the thin film.

Also, recently, as these thin films become more and more highly integrated, there is an increasing need to more accurately control and measure the properties of the film including the thickness of the thin film, which is a factor that greatly affects the characteristics of the thin film.

Accordingly, in the case of the existing nanomaterials industry, a number of microscopic analysis techniques have been developed for analysis, and they are now making unremitting efforts to continuously develop them.

Electron microscopy (ie, SEM, TEM, AES, SIMS, etc.) is well known for microscopic analysis that can analyze the surface of representative materials.

However, such an electron microscopic analysis method requires much time and expense to prepare and observe the sample, and there is a problem that the space and the environmental restriction are large.

In addition, when the sample is difficult to form a step or when the surface of the substrate is not flat, measurement is difficult. In measuring the thickness of the thin film, the error is small, but when the thin film sample having good ductility is cut, There is a limit in that it is very difficult to precisely measure the thickness when the thickness of the thin film is very thin or the surface of the substrate on which the thin film is formed is not smooth.

Particularly, since this electron microscopic analysis method can be operated only in an ultra-high vacuum state of 10 ^-6 to 10 ^-9 Torr, in order to actually expand its application range, a wide range of the product level and an analysis technique in air or water .

In order to solve these problems, ultrasonic microscope technology which can evaluate the material characteristics in the micro area including the surface and interior of the material and the interface has been proposed in the 1930 's.

In addition, the output voltage V (z) curve method, which can precisely measure the velocity of the Rayleigh wave closely related to the characteristics of the material, has been developed, and it is now possible to precisely measure the characteristics of the material for the minute domain.

However, in order to precisely measure and calculate the velocity of the Rayleigh wave when using the output voltage V (z) curve method, the signal processing such as removing the noise signal from the measured signal or separating the longitudinal wave component generated simultaneously with the Rayleigh wave It is essential.

It is also necessary to simulate the change in speed in advance in order to measure and verify the speed of the actual test object.

Accordingly, the present inventor has developed a signal analysis method of an ultrasonic microscope capable of precisely measuring the velocity of a Rayleigh wave generated in an ultrasonic microscope and theoretically simulating and analyzing the material characteristics of the nanoscale using the ultrasonic wave in accordance with the necessity .

(Patent Document 1) JP 5406729 B2

(Patent Document 2) KR 10-0110481 B1

It is an object of the present invention to provide a data base for a sensor characteristic and a characteristic of a sample to be used at the time of using an output voltage curve method of an ultrasonic microscope and to use the measured output voltage curve signal for a variety of signal processing, And to provide a signal analysis method of an ultrasonic microscope capable of evaluating material characteristics of a sample by measurement and calculation.

In addition, considering the fact that the velocity of the Rayleigh wave varies depending on the type of the contact medium and the temperature used to increase the ultrasonic wave transmission efficiency when using an actual ultrasonic microscope, The present invention aims to provide a method for predicting the change and comparing the theoretical simulated data with the actually measured data to identify the cause of the error in the signal analysis process.

The problem to be solved by the present invention is not limited to the above-mentioned problem (s), and another problem (s) not mentioned can be clearly understood by a person skilled in the art from the following description.

In order to accomplish the above object, the present invention provides a signal analysis method of an ultrasonic microscope, comprising the steps of: analyzing a signal incident on and reflected from a sample using an ultrasonic beam of an ultrasonic microscope having a transducer, a buffer rod and a lens as an intermediate medium; A method comprising the steps of: (a) designing an acoustic lens with acoustic lens parameters set; (b) selecting a coupling agent on a simulation tool menu; (c) calculating a focal distance of the sonic and acoustic beams in the coupling medium; (d) simulating the output voltage of the transducer according to the focal distance of the beam; And (e) separating the surface wave component from the simulated output voltage curve and calculating the velocity of the surface wave component to extract the elasticity information of the sample.

In order to achieve the above object, the step (d) of the method of analyzing a signal of an ultrasonic microscope according to the present invention includes the steps of (d-1) sequentially calculating acoustic fields of the transducer surface, the back focal plane, the front focal plane, ; (d-2) sequentially calculating an acoustic field in the reflection direction of the sample surface, the front focal plane, the rear focal plane, and the transducer plane; And (d-3) calculating an output voltage of the transducer by two-dimensionally integrating the product of the incident direction acoustic field (u0 +) and the reflection direction acoustic field (u0-) of the transducer surface .

In order to accomplish the above object, the step (d-1) of the ultrasonic wave microscope signal analysis method of the present invention includes a step of fast Fourier transforming the acoustic field u0 + of the transducer surface in the spatial domain, Calculating an acoustical field U0 + of the ducer surface; Calculating an acoustic field (U1 +) in the back focal plane on the wave number domain in consideration of a phase change from the transducer plane to the rear focal plane; And performing an inverse fast Fourier transform on the acoustic field U1 + to calculate an acoustic field u1 + of the back focal plane in the spatial domain; Computing an acoustical field (u2 +) of the front focal plane on the spatial domain by considering the fast Fourier transform of the pupil function and the phase change from the rear focal plane to the front focal plane; Calculating the acoustic field U2 + of the front focal plane in the wave number domain by FFT-transforming the acoustic field u2 +; Calculating an acoustic field U3 + of the sample surface on the wave number domain in consideration of a phase change from the front focal plane to the sample plane; And performing an inverse fast Fourier transform on the acoustic field U3 + to calculate an acoustic field u3 + of the sample surface in the spatial domain.

In order to attain the above object, the step (d-2) of the ultrasonic microscope signal analysis method of the present invention includes the step of calculating the acoustic field U3- of the sample surface on the wave number domain in consideration of the reflection function of the sample ; Performing an inverse fast Fourier transform on the acoustic field U3- to calculate an acoustic field u3- of the sample surface in the spatial domain; Calculating an acoustic field (U2-) of the front focal plane on the wave number domain in consideration of a phase change from the sample surface to the front focal plane; Performing an inverse fast Fourier transform of the acoustic field U2- to calculate an acoustic field u2- of the front focal plane in the spatial domain; Computing an acoustic field (u1 < - >) of the back focal plane on the spatial domain by considering the fast Fourier transform of the pupil function and the phase change from the front focal plane to the rear focal plane; Performing inverse fast Fourier transform of the acoustic field (u1-) to calculate an acoustic field (U1-) of the back focal plane in the wave number domain; And calculating an acoustic field (u0-) of the transducer plane on the spatial domain by convoluting the inverse fast Fourier transform of the phase change from the acoustic field (u1-) and the rear focal plane to the transducer plane .

According to another aspect of the present invention, there is provided a method of analyzing a signal of an ultrasonic microscope, the acoustic lens parameter including parameters for the transducer, the buffer rod, the lens, and the coupling medium.

According to another aspect of the present invention, there is provided a method of analyzing a signal of an ultrasound microscope, wherein the parameter for the transducer includes a transducer component, a center frequency, a transducer dimension, and a distance to a rear focal plane.

In order to attain the above object, a parameter of the buffer rod of the ultrasonic microscope signal analysis method of the present invention is characterized by including a buffer rod constituent material, a velocity of a transverse wave, a velocity of a longitudinal wave and a density.

According to another aspect of the present invention, there is provided a method of analyzing a signal of an ultrasonic microscope, the method comprising the steps of: measuring an aperture angle, an aperture diameter, a radius of curvature, and a focal length.

In order to achieve the above object, a parameter of the coupling medium of the ultrasonic microscope signal analysis method of the present invention is characterized by including a coupling medium constituent material, a velocity of a transverse wave, a velocity of a longitudinal wave, a density and a thickness.

In order to achieve the above object, in the step (e) of the ultrasonic wave signal analysis method of the present invention, a predetermined portion of the output voltage curve of the transducer is selected and subjected to Fourier transform on the selected portion, Converting; Power spectruming the waveform transformed into the frequency domain, and converting the frequency axis into a velocity axis within the power spectrum; Selecting a lobe including a value estimated at a speed of the surface wave in the spectrum; Performing inverse Fourier transform on the selected lobes to re-transform the frequency domain into a spatial domain; Power spectruming the waveform re-transformed into the spatial domain, and converting the frequency axis into a velocity axis within the power spectrum; And calculating a velocity of the surface wave component by reading a maximum amplitude of the power spectrum and reading a velocity value corresponding to the maximum amplitude.

The details of other embodiments are included in the detailed description and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and / or features of the present invention and the manner of achieving them will be apparent from and elucidated with reference to the embodiments described hereinafter in conjunction with the accompanying drawings. It should be understood, however, that the invention is not limited to the disclosed embodiments, but may be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. And is provided to fully explain the scope of the present invention to those skilled in the art.

According to the present invention, unlike the conventional electron microscopic analysis method capable of analyzing the surface of a sample, the time and cost required for preparation and observation of the sample can be reduced, space and environmental constraints can be overcome, Theoretically, by comparing and analyzing the simulated data and the actual measured data, it is possible to accurately identify the cause of the error in the signal analysis process.

In addition, the measurement is easy even when the sample is difficult to form a step or the surface of the substrate is not flat, and when the thickness of the thin film is measured, the boundary between the base and the film is not clear when the thin film sample is cut, The thickness can be precisely measured even when the surface of the thin or thin film formed substrate is not smooth.

1 is a block diagram of a signal analysis apparatus for implementing a signal analysis method of an ultrasonic microscope according to the present invention.
2 is a flowchart showing a signal analysis method of an ultrasonic microscope according to the present invention.
3 is a geometrical view of the ultrasonic microscope in the signal analysis apparatus shown in FIG.
4 is a detailed flowchart showing a simulation step of calculating an output voltage of the transducer in the flowchart of the signal analysis method of the ultrasonic microscope shown in FIG.
5 is a formula of the output voltage of the transducer calculated through the simulation step shown in FIG.
6 is a characteristic graph showing a waveform in which the curve of the output voltage V (z) of the transducer displayed through the simulation step shown in FIG. 4 is divided into a longitudinal wave component and a surface wave component.
FIG. 7 is a characteristic graph comparing an actually measured experimental result with an output voltage V (z) curve of a transducer displayed through the simulation step shown in FIG.
FIG. 8 is a detailed flowchart showing a method of calculating the surface wave velocity using the output voltage V (z) curve of the transducer shown in FIG.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary terms and the inventor can properly define the concept of the term to describe its invention in the best way Should be construed in accordance with the principles and meanings and concepts consistent with the technical idea of the present invention.

In the specification, when a component is referred to as being "comprising" or "including" an element, it is to be understood that this may include other elements, . Also, the terms "part", "unit", "module", "device", "step", and the like described in the specification mean units for processing at least one function or operation, Lt; / RTI >

1 is a block diagram of a signal analysis apparatus for implementing a signal analysis method of an ultrasonic microscope according to the present invention.

2 is a flowchart showing a signal analysis method of an ultrasonic microscope according to the present invention.

The operation of the signal analysis method of the ultrasonic microscope according to the present invention will be described with reference to FIGS. 1 and 2. FIG.

Theoretically, the output voltage V (z) curve can be explained by the interference of specularly reflected acoustic waves and leaky surface acoustic waves.

That is, when a half aperture angle of the acoustic lens is larger than a critical angle for generating a surface wave, a leaky surface wave is generated at the interface between the coupling medium 140 and the sample 150.

At this time, the surface wave propagates along the surface of the sample 150 and emits energy from the critical angle to the coupling medium 140. When the mode used is the burst mode, the leaked surface wave interferes with the reflec- And this interference forms a graph in which the voltage periodically changes according to the distance between the acoustic lens and the sample 150. [

The graph of the voltage change caused by this phenomenon is called the output voltage V (z) curve.

That is, as the probe moves toward the acoustic lens, the voltage changes. The change in the voltage has a periodic characteristic. In the graph of the voltage having the periodicity, the interval between the peaks and the peaks or between the bones and the valleys is measured, Can be measured.

1 and 2, the transmitter 110 generates a high-power radio frequency (RF) signal having a tone-burst signal with an amplitude of about 10 V and outputs the generated signal.

When a radio frequency (RF) signal passes through a circulator 115 that separates input and output signals and is delivered to a transducer 120 at the top of the buffer rod 130, the input electrical signal passes through a transducer 120, Thereby vibrating the piezoelectric element incorporated in the piezoelectric element.

Here, the transducer 120 is made of zinc oxide and transfers acoustic energy to the buffer rod 130 in the form of ultrasonic plane waves.

The buffer rod 130 is made of sapphire for fast propagation of acoustic energy. The buffer rod 130 moves an ultrasonic plane wave in the interior of the buffer rod 130, passes through the acoustic lens, and converts the ultrasonic wave into a spherical wave, such as an ultrasonic beam.

As shown in FIG. 1, an aperture of the lens is provided with an anti-acoustic reflection coating (AARC), which is a matching layer for compensating impedance mismatch between the buffer rod 130 and the coupling medium 140 .

The ultrasound beam is propagated through the coupling medium 140 to focus on the sample 150 and then reflected from the sample 150 to transmit the acoustic elasticity information of the sample 150.

The reflected ultrasound beam returns to the lens, passes through the lens and is converted back to an ultrasonic plane wave, and the acoustic energy is converted back into an electrical signal through the transducer 120.

When the operating frequency range is 100 MHz to 1 GHz and the input source is about 10 V, the output voltage of the transducer 120 ranges from 300 mV to 1 V.

This means that there is a loss of about 30 to 80 dB, and the output electrical signal must be amplified to 30 to 80 dB to compensate for the loss.

The amplitude of the compensated output signal is interpreted by the image processing module and displayed at a constant point on the monitor.

The sample 150 is mechanically scanned by moving the stage of the acoustic lens or the sample 150 to construct a two-dimensional ultrasound image.

In order to visualize the surface of the sample 150, the axial position of the acoustic lens (Z-axis in FIG. 1) is set to the focal length, usually expressed as Z = 0 um.

As shown in FIG. 2, in the method of analyzing a signal of an ultrasonic microscope according to the present invention, an acoustic lens parameter is first set for acoustic lens simulation (S100).

Acoustic lens parameters are categorized into four categories: transducer 120, buffer rod 130, lens and coupling medium 140.

The parameters for the transducer 120 include the transducer material, the center frequency, the transducer dimension, and the distance to the back focal plane.

The parameters for the buffer load 130 include the buffer load constituent material, the velocity of the transverse waves, the velocity and density of the longitudinal waves.

The parameters for the lens include aperture angle, aperture diameter, radius of curvature, and focal length.

The parameters for the coupling medium 140 include the medium constituent material, the velocity of the transverse wave, the velocity of the longitudinal wave, the density and the thickness.

Based on the set acoustic lens parameters, the acoustic lens is designed (S200) and the coupling medium 140 is selected on the simulation tool menu (S300).

In this embodiment, distilled water with a temperature of 20 degrees Celsius was selected, and the temperature of the coupling medium 140 influences the calculation of the focal length of the acoustic beam and the acoustic beam at the coupling medium 140 (S400) .

Simulation is then performed to calculate the output voltage of the transducer 120 according to the focal length of the beam using the focal distance of the acoustic and acoustic beams in the coupling medium 140 thus calculated (S500).

The output voltage result of the simulated transducer 120 is plotted as an output voltage V (z) curve and displayed on the screen (S600), and the design of the acoustic lens from the vibration waveform of the output voltage V (z) (S700).

If the design of the acoustic lens is appropriate, the acoustic lens simulation is terminated. Otherwise, the process returns to step S100 and the above operation is repeated.

FIG. 3 is a geometrical view of the ultrasonic microscope in the signal analysis apparatus shown in FIG. 1, in which the transducer 120, the back focus, the front focus, and the sample surface are indexed with 0, 1, 2, and 3, respectively.

In FIG. 3, the superscript '+' denotes the + Z direction of the incident wave propagation direction, and the subscript '-' denotes the -z direction, which is the propagation direction of the reflected wave.

Also, u _i ^+/- represents the acoustic field in the spatial region of the i-th surface, and U _i ^+/- represents the acoustic field in the frequency region of the i-th surface.

4 is a detailed flowchart showing a simulation step S500 for calculating an output voltage of the transducer 120 in the flow chart of the signal analysis method of the ultrasonic microscope shown in FIG.

5 is a formula of the output voltage of the transducer 120 calculated through the simulation step S500 shown in FIG.

The operation of the simulation step S500 of calculating the output voltage of the transducer 120 in the signal analysis method of the ultrasonic microscope according to the present invention will be described with reference to FIGS. 1 to 5 as follows.

4, the simulation of the output voltage V (z) curve of the transducer 120 is based on an angular-spectrum approach based on Fourier transform, with a transducer surface, a back focal plane, Acoustic fields on the front focal plane and the sample plane are sequentially calculated (S510 to S540).

Then, the acoustic fields in the front focal plane, the back focal plane, and the transducer plane are calculated again from the sample surface in the reverse direction (S550 to S580).

5, a pupil function determined by the geometry of the lens is considered in relation to the back focal plane and the front focal plane, and the pupil function is determined depending on the acoustic elastic characteristics of the sample 150 on the sample plane. A reflection function is considered.

The output voltage of the transducer 120 is calculated by two-dimensionally integrating the incident acoustic field u0 + and the reflected acoustic field u0- on the sequentially calculated transducer plane.

In other words, the incident acoustical field can be assumed to be a Gaussian distribution, and the deformation from the incident acoustical field u0 + of the transducer plane in the spatial domain to the wave number domain can be performed by fast Fourier transform. Calculate the acoustic field U0 + of the incident direction transducer plane.

(U1 +) on the back focal plane on the domain of the wave number in consideration of the phase change from the transducer plane to the rear focal plane, calculates an inverse fast Fourier transform of the acoustic field Lt; + > of the back focal plane of the light source.

(U2 +) of the front focal plane on the spatial domain in consideration of the fast Fourier transform of the pupil function and the phase change from the back focal plane to the front focal plane, (U2 +) is calculated.

(U3 +) of the sample surface in the wave number domain is calculated in consideration of the phase change from the front focal plane to the sample surface, and the acoustic field (u3 +) of the sample surface in the spatial domain is calculated from the inverse fast Fourier transform thereof .

Then, in the reflection step, the acoustic field U3- of the reflection direction sample surface on the wave number domain is calculated in consideration of the reflection function of the sample 150, and the acoustic field U3- of the reflection direction sample face in the spatial domain from the inverse fast Fourier transform thereof Calculate acoustical field (u3-).

(U2-) of the front focal plane on the wave number domain is calculated in consideration of the phase change from the sample surface to the front focal plane, and from the inverse fast Fourier transform thereof, the acoustic field (u2- ).

The inverse fast Fourier transform of the pupil function calculates the acoustic field u1- of the back focal plane on the spatial domain by considering the phase change from the front focal plane to the rear focal plane, Calculate the acoustic field U1- of the back focal plane.

The acoustic field u1- of the rear focal plane on the spatial domain and the inverse fast Fourier transform of the phase change from the rear focal plane to the transducer plane are convolved to calculate the acoustic field u0- of the transducer plane in the spatial domain.

The output voltage of the transducer 120 is calculated by two-dimensionally integrating the product of the acoustic field u0 + of the incident direction transducer surface and the acoustic field u0- of the reflection direction transducer surface.

FIG. 6 is a characteristic graph showing a waveform in which the curve of the output voltage V (z) of the transducer 120 displayed through the simulation step shown in FIG. 4 is divided into a longitudinal wave component and a surface wave component, wherein (A) 120), (B) is the separated longitudinal wave component, and (C) is the separated surface wave component.

FIG. 7 is a characteristic graph comparing output voltage V (z) curves of the transducer 120 displayed through the simulation step shown in FIG. 4 and actually measured actual measurement results. The solid line is a simulation result, to be.

Acoustic microscopy scanning has other features that are called ultrasound image and also the output voltage V (z) curve analysis of the transducer 120.

The curve of the output voltage V (z) of the transducer 120 is a plot of the output voltage of the transducer 120 according to the z-axis distance perpendicular to the direction of movement of the acoustic lens.

The output voltage V (z) curve analysis of the transducer 120 exploits the fact that the propagation of the sound waves and the elastic properties of the constituent material are directly related.

The curve of the output voltage V (z) of the transducer 120 can be explained from the phenomenon of interference occurring when the acoustic wave moves from the liquid to the solid surface at a Rayleigh angle.

That is, the combined energy of the incident wave and the leaky surface acoustic wave at or near the Rayleigh angle affects the propagation of the specularly reflected energy.

As shown in FIG. 6 (A), the interference phenomenon forms an oscillation curve shape at the output voltage V (z) of the transducer 120.

Therefore, the curve decomposition of the output voltage V (z) of the transducer 120 includes a longitudinal wave component and a surface acoustic wave component, as shown in Figs. 6 (B) and 6 (C).

In Fig. 7, the lenses used the same operating frequency of 400 MHz, and at an aperture angle of 120 degrees, a radius of curvature of 866 mu m and a focal length of 577.50 mu m, the operating temperature was 20 degrees Celsius.

As shown in Fig. 7, even though the simulated waveform and the measured result waveform may not appear to be exactly the same in amplitude, this is merely due to simplification of the pupil function, and the difference in amplitude affects the accuracy of the velocity calculation of the surface acoustic wave Do not.

This is because it is not the amplitude but the null interval (? Z) between the peaks, which is important for the calculation of the speed of the surface acoustic wave.

8 is a detailed flowchart showing a method of calculating the surface wave velocity using the output voltage V (z) curve of the transducer 120 shown in FIG.

The operation of calculating the surface wave velocity in the signal analysis method of the ultrasonic microscope according to the present invention will be described with reference to FIGS. 1 to 8 as follows.

Since the curve of the output voltage V (z) of the transducer 120 shown in FIG. 7 has elasticity information of the sample 150, the velocity of the surface wave is calculated from the curve of the output voltage V (z) Information can be extracted.

First, since the curve of the output voltage V (z) of the transducer 120 has the information of the transverse wave, the longitudinal wave and the surface wave, the component of the surface wave must first be extracted.

That is, since the curve of the output voltage V (z) is plotted in the spatial domain, a predetermined portion is selected from the V (z) curve (S810) and Fourier transformed on the selected portion (S820) (S830). After power spectrum (S840), the frequency axis is converted into a frequency axis in the spectrum (S850).

In addition, a lobe including a value estimated by the speed of the surface wave in the power spectrum is selected (S860), and the inverse Fourier transform is performed on the selected lobe (S870).

In step S990, the selected part is subjected to Fourier transform (step S900), and then the frequency domain is transformed from the spatial domain to the frequency domain again (step S910). After the power spectrum is obtained (step S920) To the speed axis (S930).

The maximum amplitude of the power spectrum is read (S940), and the velocity Vsaw of the surface wave component as shown in Equation 1 is calculated by reading the velocity value matching the maximum amplitude (S950).

Here, Vw is the sonic velocity in the water, f is the frequency of the transducer 120, and z is the minimum value distance in the curve of the output voltage V (z) of the transducer 120.

As described above, the signal analysis method of the ultrasonic microscope according to the present invention is a method of analyzing the characteristics of the sensor 150 to be used in the use of the output voltage curve method of the ultrasonic microscope and the measured output voltage curve signal, A signal analyzing method of an ultrasonic microscope capable of evaluating a material characteristic of a sample 150 by measuring and calculating a velocity of a Rayleigh wave with higher precision using the same.

In addition, considering the fact that the velocity of the Rayleigh wave varies depending on the type of the contact medium and the temperature used to increase the ultrasonic wave transmission efficiency when using an actual ultrasonic microscope, Predicts the change, and provides a method to identify the cause of errors that can occur in the signal analysis process by comparing and analyzing the theoretical simulated data and actual measured data.

Unlike conventional electron microscopy, which can analyze the surface of a sample, it is possible to reduce the time and expense required to prepare and observe the sample, to overcome space and environmental constraints, and to simulate theoretically By comparing and analyzing the data with the actual measured data, it is possible to accurately identify the cause of the error in the signal analysis process.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims

A method of analyzing a signal incident on and reflected from a sample using an ultrasonic beam of an ultrasonic microscope having a transducer, a buffer rod and a lens as an intermediate medium,
(a) an acoustic lens parameter is set so that an acoustic lens is designed;
(b) selecting a coupling agent on a simulation tool menu;
(c) calculating a focal distance of the sonic and acoustic beams in the coupling medium;
(d) simulating the output voltage of the transducer according to the focal distance of the beam; And
(e) separating a surface wave component from the simulated output voltage curve and calculating a velocity of the surface wave component to extract elasticity information of the sample;
Lt; / RTI >
The step (d)
(d-1) sequentially calculating acoustic planes of the transducer plane, the back focal plane, the front focal plane, and the sample plane;
(d-2) sequentially calculating an acoustic field in the reflection direction of the sample surface, the front focal plane, the rear focal plane, and the transducer plane; And
(d-3) calculating an output voltage of the transducer by two-dimensionally integrating a product of the incident direction acoustic field (u0 +) and the reflection direction acoustic field (u0-) of the transducer surface;
&Lt; / RTI >
Signal Analysis Method of Ultrasonic Microscope.

delete

The method according to claim 1,
The step (d-1)
Calculating an acoustic field (U0 +) of the transducer surface in the domain of the wave number by performing a fast Fourier transform on the acoustic field (u0 +) of the transducer surface in the spatial domain;
Calculating an acoustic field (U1 +) in the back focal plane on the wave number domain in consideration of a phase change from the transducer plane to the rear focal plane; And
Performing an inverse fast Fourier transform of the acoustic field U1 + to calculate an acoustic field u1 + of the back focal plane in the spatial domain;
Computing an acoustical field (u2 +) of the front focal plane on the spatial domain by considering the fast Fourier transform of the pupil function and the phase change from the rear focal plane to the front focal plane;
Calculating the acoustic field U2 + of the front focal plane in the wave number domain by FFT-transforming the acoustic field u2 +;
Calculating an acoustic field U3 + of the sample surface on the wave number domain in consideration of a phase change from the front focal plane to the sample plane; And
Performing an inverse fast Fourier transform on the acoustic field U3 + to calculate an acoustic field u3 + of the sample surface in the spatial domain;
&Lt; / RTI >
Signal Analysis Method of Ultrasonic Microscope.

The method according to claim 1,
The step (d-2)
Calculating an acoustic field U3 < - > of the sample surface on the wave number domain in consideration of the reflection function of the sample;
Performing an inverse fast Fourier transform on the acoustic field U3- to calculate an acoustic field u3- of the sample surface in the spatial domain;
Calculating an acoustic field (U2-) of the front focal plane on the wave number domain in consideration of a phase change from the sample surface to the front focal plane;
Performing an inverse fast Fourier transform of the acoustic field U2- to calculate an acoustic field u2- of the front focal plane in the spatial domain;
Computing an acoustic field (u1 < - >) of the back focal plane on the spatial domain by considering the fast Fourier transform of the pupil function and the phase change from the front focal plane to the rear focal plane;
Performing inverse fast Fourier transform of the acoustic field (u1-) to calculate an acoustic field (U1-) of the back focal plane in the wave number domain; And
Calculating an acoustic field (u0-) of the transducer plane on the spatial domain by convoluting the inverse fast Fourier transform of the phase change from the acoustic field (u1-) and the rear focal plane to the transducer plane;
&Lt; / RTI >
Signal Analysis Method of Ultrasonic Microscope.

The method according to claim 1,
The acoustical lens parameter
The parameters for the transducer, the buffer rod, the lens, and the coupling medium.
Signal Analysis Method of Ultrasonic Microscope.

6. The method of claim 5,
The parameters for the transducer are
Transducer dimensions, and the distance to the back focal plane. &Lt; RTI ID = 0.0 >
Signal Analysis Method of Ultrasonic Microscope.

6. The method of claim 5,
The parameters for the buffer load are
Buffer load constituent material, velocity of transverse waves, velocity and density of longitudinal waves,
Signal Analysis Method of Ultrasonic Microscope.

6. The method of claim 5,
The parameters for the lens are
Aperture diameter, aperture diameter, radius of curvature, and focal length.
Signal Analysis Method of Ultrasonic Microscope.

6. The method of claim 5,
The parameters for the coupling medium are
Coupling agent composition material, velocity of transverse waves, velocity of longitudinal waves, density and thickness.
Signal Analysis Method of Ultrasonic Microscope.

The method according to claim 1,
The step (e)
Selecting a predetermined portion from an output voltage curve of the transducer and performing Fourier transform on the selected portion to convert the spatial domain to the frequency domain;
Power spectruming the waveform transformed into the frequency domain, and converting the frequency axis into a velocity axis within the power spectrum;
Selecting a lobe including a value estimated at a speed of the surface wave in the spectrum;
Performing inverse Fourier transform on the selected lobes to re-transform the frequency domain into a spatial domain;
Power spectruming the waveform re-transformed into the spatial domain, and converting the frequency axis into a velocity axis within the power spectrum; And
Calculating a velocity of the surface wave component by reading a maximum amplitude of the power spectrum and reading a velocity value corresponding to the maximum amplitude;
&Lt; / RTI >
Signal Analysis Method of Ultrasonic Microscope.