Vibration analysis system, vibration analysis device, and vibration analysis method

Abstract

The purpose of the present invention is to provide a vibration analysis system, a vibration analysis device, and a vibration analysis method that enable vibration analysis of samples that generate minute vibrations while keeping down construction costs.　In this vibration analysis system, a differential interference microscope is used to irradiate a sample driven by a voltage signal of a prescribed frequency with pulsed light modulated in phase synchronization with the voltage signal and capture a microscopic image of the sample, the differential interference microscope being capable of emitting pulsed light split through a differential interference prism and measuring the protrusion shapes and depression shapes of a sample surface in a prescribed measurement range.

Description

[Technical Field]

[0001] The present disclosure relates to a vibration analysis system, a vibration analysis apparatus, and a vibration analysis method. [Background Art]

[0002] Conventionally, there are techniques for performing vibration analysis on micro-vibration devices such as MEMS (Micro Electro Mechanical Systems) devices. A MEMS device has an overall length on the order of millimeters, and its components are on the order of micrometers. Therefore, the scale of vibration analysis for such MEMS devices ends up being minute, on the order of nanometers or even smaller.

[0003] Mainly two types of methods have been used for vibration analysis of MEMS devices. One is a method using a laser Doppler vibrometer based on the optical Doppler effect. This method can achieve high-sensitivity vibration measurement, but it is limited to measuring only one point at a time, making two-dimensional vibration analysis difficult.

[0004] Another method involves using a dual-beam interference microscope, such as a Michelson interferometer. Several techniques for two-dimensional vibration analysis of MEMS devices using this method have been proposed and put into practical use. This technique is described in Patent Document 1 and Non-Patent Documents 1-3. Patent Document 1 is Japanese Patent Publication No. 2016-501373. Non-Patent Document 1 is "A. Bosseboeuf, et al., presented at the Microsystems Metrology and Inspection, 1999." Non-Patent Document 2 is "J. Reed, et al., Journal of Microelectromechanical Systems 16, 668 (2007)." Non-Patent Document 3 is "I. Shavrin, et al., Opt. Express 21, 16901 (2013)." The following points are common to this method. The first commonality is that the surface shape of the MEMS device is measured using an interference microscope, and the two-dimensional height of the MEMS device surface is measured by interference between a reference light and a measurement light. The second commonality is that the vibration shape is analyzed by irradiating the elements of the MEMS device with a pulse light source that is phase-locked to the vibration of the MEMS device and sampling the high-speed vibrations. [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] However, prior art using conventional interference microscopes for two-dimensional vibration analysis of MEMS devices had the problem of difficulty in adjusting the optical system. Therefore, high-precision optical mechanical components were required to construct the vibration analysis system, resulting in high costs. Furthermore, prior art had the problem of a narrow measurement range, preventing sufficient measurements from being performed.

[0006] This disclosure aims to provide a vibration analysis system, a vibration analysis apparatus, and a vibration analysis method that can analyze the vibrations of samples that generate minute vibrations while suppressing the costs associated with their construction. [Means for solving the problem]

[0007] The vibration analysis system of this disclosure is configured to irradiate a sample driven by a voltage signal of a predetermined frequency with pulsed light modulated in phase synchronization with the voltage signal, and to capture a microscopic image of the sample. This is done using a differential interference microscope capable of measuring the protrusion and depression shapes on the sample surface within a predetermined measurement range.

[0008] The vibration analysis apparatus of this disclosure comprises a differential interference microscope capable of measuring the protrusion and depression shapes of a sample surface within a predetermined measurement range by irradiating pulsed light branched through a differential interference prism; a signal source that applies a voltage signal of a predetermined frequency to the sample; a light source that irradiates the sample with the pulsed light modulated in phase synchronization with the voltage signal; and an optical system that captures a microscopic image of the sample.

[0009] The vibration analysis method of this disclosure includes the steps of: irradiating a sample with pulsed light branched through a differential interference prism using a differential interference microscope capable of measuring the protrusion and depression shapes of the sample surface within a predetermined measurement range; applying a voltage signal of a predetermined frequency to the sample; irradiating the sample with the pulsed light modulated in synchronization with the voltage signal; and capturing a microscopic image of the sample. [Brief explanation of the drawing]

[0010] [Figure 1A] This is a simplified schematic diagram of a conventional vibration analysis method using an interference microscope. [Figure 1B] This is a schematic diagram for comparing vibration analysis methods using differential interference microscopy. [Figure 2A] This is an image of a bent MEMS beam observed with a standard microscope. [Figure 2B] This is an image of a bent MEMS beam observed using a Michelson interference microscope. [Figure 2C]This is an image of a bent MEMS beam observed with a differential interference microscope. [Figure 3] This is a diagram showing the configuration of the vibration analysis system of this embodiment. [Figure 4A] This graph illustrates high-speed vibrations caused by pulsed light sources. [Figure 4B] This graph illustrates high-speed vibrations caused by pulsed light sources. [Figure 5A] This is a microscopic image. [Figure 5B] This is a graph of light intensity. [Figure 6A] This figure shows the measurable frequency range. [Figure 6B] This figure shows the pulse width of the illumination light. [Figure 7] Block diagram showing the hardware configuration of the control unit. [Figure 8] This diagram shows the processing flow of the measurement program. [Figure 9] This is an example of the measurement results for vibration amplitude. [Figure 10A] These are the measurement results for the mode shape. [Figure 10B] These are the measurement results for the mode shape. [Figure 10C] These are the measurement results for the mode shape. [Modes for carrying out the invention]

[0011] Embodiments of this disclosure will be described in detail below with reference to the drawings.

[0012] Before describing embodiments of the present disclosure, the problems mentioned in the above-mentioned issues, namely (1) the difficulty of adjusting the optical system and (2) the narrow measurement range, in vibration analysis of MEMS devices which are microvibration devices will be described. In the following description, a case where the vibration analysis method of the present embodiment is applied with a MEMS device as a sample will be described as an example, but the present invention is not limited thereto. The vibration analysis method of the present embodiment enables measurement on a nanometer-scale. Therefore, similarly to MEMS devices, the vibration analysis method of the present embodiment can also be applied to other microvibration devices having micro sizes such as millimeter-unit or micrometer-unit sizes in the height direction and the lateral direction. In addition, the vibration analysis method of the present embodiment is not limited to microvibration devices, and can also be applied to substances, cells, and the like as long as the sample can generate microvibration.

[0013] Regarding (1), conventional interferometers use interference fringes of reference light and measurement light, so it was necessary to precisely align the surface of the device with a reference mirror used as a reference. The height of the sample must be adjusted with an accuracy of several tens of nanometers, and the inclination angle of the sample surface must be adjusted to 0.01° or less. Such settings require extremely difficult optical adjustment and high-precision optomechanical components. For this reason, the cost related to the optical system has been increased. In addition, vibration received from the environment has a great influence on the stability of interference fringes, so strict vibration isolation was also required. Therefore, conventional vibration analysis systems for MEMS devices have the problem of high construction costs.

[0014] Regarding (2), in conventional two-dimensional vibration analysis, the maximum measurable displacement is smaller than one quarter of the wavelength of the irradiated light (generally about 100 to 200 nm), which does not provide a sufficient measurable range for many studies such as measurement of nonlinear vibration of MEMS devices. Furthermore, if there is a structure with a large stepwise phase change on the surface of the MEMS device, there is a possibility that accurate measurement cannot be performed.

[0015] In order to solve these two problems, a vibration analysis system using a differential interference microscope instead of a conventional interference microscope is constructed to perform two-dimensional vibration analysis of MEMS devices.

[0016] Figure 1 (Figures 1A and 1B) is a simplified schematic diagram for comparing the conventional vibration analysis method using an interference microscope and the vibration analysis method using a differential interference microscope. As shown in Figure 1A, the conventional method using an interference microscope of (A) adopts a configuration in which pulsed light is reflected using a reference mirror to measure interference fringes. On the other hand, the method using the differential interference microscope according to the present embodiment in (B) of Figure 1B adopts a configuration where pulsed light is split using a differential interference prism without using a reference mirror.

[0017] In the vibration analysis method using the conventional interference microscope of (A), the configuration includes an interference microscope (Ma), a camera (Mb), a light source (Mc), and a MEMS device (Md). In the interference microscope (Ma), pulsed light (mc1) emitted from the light source (Mc) is irradiated onto the MEMS device (Md) through a lens (ma1), a beam splitter (ma2), and an objective lens (ma3) to serve as measurement light, and reference light is reflected by a reference mirror (ma4). This enables measurement of interference fringes of phase difference that vary according to the unevenness of the sample. In the vibration analysis method using the differential interference microscope according to the present embodiment of (B), the configuration includes a differential interference microscope (Ma2), a camera (Mb), a light source (Mc), and a MEMS device (Md). Without using the reference mirror (ma4), a differential interference prism (ma5) is used to split the pulsed light into two light beams which are then irradiated onto the sample. The small lateral shift between the two light beams is referred to as shear amount. The shear amount is determined by the differential interference prism and the objective lens. For example, when an Olympus differential interference prism U-DICR is combined with an Olympus objective lens LMPlanFL10x, the shear amount is approximately 2.5 μm. When there is a difference in optical paths as described above, the light intensity is modulated and appears as interference fringes.

[0018] When using a differential interference microscope (DISM), the following advantages are available: Since a DISM microscope does not use a reference light, it eliminates the need for complex adjustments between the reference light and the measurement light. Furthermore, because all interference light is reflected from the sample surface, the effects of ambient vibration, ambient light noise, and sample tilt are significantly reduced, eliminating the need for special vibration isolation or light shielding. Additionally, since DISM measurements measure displacement deviations, there are virtually no limitations on the total displacement. The measurement range is more than 10 times larger compared to a Michelson interference microscope.

[0019] Figure 2 (Figures 2A, 2B, and 2C) compares images of a bent MEMS beam observed with a conventional microscope, a Michelson interference microscope, and a differential interference microscope. The MEMS beam is a cantilevered beam structure using MEMS devices. Figure 2A(a) is an image observed with a conventional microscope, and the surface shape of the bent MEMS beam in part (a1) cannot be shown. Figure 2B(b) is an image observed with a conventional Michelson interference microscope, and the bending shape of the MEMS beam is shown by interference fringes. However, even when the tilt angle of the MEMS device is adjusted to a very small angle of 0.05°, the interference fringes are strongly affected by the tilt angle. Part (b1) is the interference fringe due to bending, part (b2) is the interference fringe due to tilt, and part (b3) is the interference fringe due to the electrodes. Furthermore, if the measurement optical path length constantly changes due to sample vibration, it is not possible to maintain the zero optical path length difference condition that is essential for generating interference fringes, making long-term measurements extremely difficult. On the other hand, the image observed with the differential interference microscope in Figure 2C(c) is extremely stable and completely unaffected by the small tilt angle of the MEMS device. Although no adjustments were made to the tilt of the element, the change in light intensity due to the bending of the MEMS beam in section (c1) is clearly observed, and there is almost no "background interference" caused by the tilt of the device or surface electrodes like in (b).

[0020] From the above comparison between conventional interference microscopes and differential interference microscopes, it can be concluded that a vibration analysis system with the following advantages can be realized by using a differential interference microscope.

[0021] Conventional interference microscopes require the sample surface to be perfectly aligned with the reference plane. However, by employing a differential interference microscope, only reflected light from the sample surface is used for interference, eliminating the need for most optical adjustments. Therefore, complex optical interference (zero point and tilt) adjustments become unnecessary, improving convenience. Furthermore, because differential interference microscopy uses only reflected light from the sample surface, environmental vibrations have less impact on the interference fringes compared to conventional techniques. Therefore, it is less sensitive to vibration, eliminating the need for vibration isolation tables. Moreover, commercially available differential interference microscopes, which are less expensive than dedicated interference microscopes, can be used. This reduces the cost required to construct a vibration analysis system. Furthermore, compared to conventional technology, the measurement displacement range is larger (more than 10 times), making it possible to measure samples with complex surfaces. Furthermore, because it eliminates the need for expensive and precise mechanical adjustment systems, differential interference microscopes are less expensive than dedicated dual-beam interference microscopes, offering a cost advantage.

[0022] The configuration of the vibration analysis system according to the embodiment of this disclosure will be described below.

[0023] Figure 3 shows the configuration of the vibration analysis system of this embodiment. As shown in Figure 3, the vibration analysis system 1 consists of a differential interference microscope 10, a digital camera 12, a light source 14 (pulse-modulated LED or laser light source), a function generator 16, and a control unit 18. In this configuration, the vibration analysis system 1 observes the MEMS device 20, which is the sample to be observed. The vibration analysis system 1 is configured as the vibration analysis apparatus of this disclosure by comprising all of these components.

[0024] Each functional component of the vibration analysis system 1 functions as follows: (1) The differential interference microscope 10 visualizes surface information of the MEMS device on an nm scale. (2) The digital camera 12 captures images recording the interference pattern of the differential interference microscope 10. (3) The light source 14 incidents periodic pulsed light (illumination light) synchronized with the drive voltage of the MEMS device. The vibration analysis system 1 samples the high-speed MEMS vibrations generated by the pulses. (4) The function generator 16 supplies a phase-synchronized drive voltage to the pulse-modulated LED 12 and the MEMS device 20. (5) The control unit 18 is a computer that includes analysis software and programs, and calculates the amplitude of the MEMS device 20 and the mode shape of the vibration by controlling the measurement process. Each functional component is described below.

[0025] The differential interference microscope 10 comprises a beam splitter 10a, a polarizer 10b, a differential interference prism 10c, and an objective lens 10d. The beam splitter 10a is positioned to direct pulsed light (Pu) incident from a lens (not shown) towards the MEMS device 20. The polarizer 10b converts the pulsed light (Pu) into deflection. The differential interference prism 10c splits the pulsed light (Pu1) incident via the polarizer 10b into two beams of light (Pu2). In the following description, when distinguishing between the beams before and after splitting, the pulsed light before splitting will be referred to as (Pu1), and the two resulting pulsed beams after splitting will be referred to as (Pu2). When not distinguishing between them, they will simply be referred to as (Pu). The objective lens 10d irradiates the MEMS device with the two split beams of light (Pu2). Note that the configuration of the differential interference microscope 10 is not limited to this. Rather, it may be configured as appropriate according to the design of the microscope. The differential interference microscope 10 should be configured to irradiate the MEMS device 20 with pulsed light (Pu2) branched through a differential interference prism (10c) and measure the surface irregularities (protrusions and depressions) of the MEMS device 20. The measurement range for irregularities is usually from 1 nm to several thousand nm, preferably from 1 nm to 1000 nm. The parameter that determines the measurement range for irregularities is the differential displacement caused by the irregularities, and the parameter for the differential displacement caused by the irregularities is approximately from 0.05 nm to 60 nm.

[0026] The digital camera 12 is attached to the differential interference microscope 10, and a microscopic image of the MEMS device 20 is captured through the differential interference microscope 10. Any color or monochrome CMOS or CCD camera can be used as the digital camera 12. The digital camera 12 is an example of an optical system for capturing a microscopic image of the sample in this disclosure.

[0027] Here, the measurement principle of the vibration analysis system 1 will be explained. The vibration analysis system 1, which uses a differential interference microscope 10 equipped with a digital camera 12, can, in principle, observe the movement of the MEMS device 20. However, the frame rate of most digital cameras is around several tens of Hz, which is far slower than the operating frequency band of the MEMS device (several tens of kHz to several tens of MHz). Figure 4 (Figures 4A and 4B) shows graphs illustrating high-speed vibration due to a pulsed light source. As shown in Figure 4A(a), the light source 14 (pulse-modulated LED or laser light source) irradiates the MEMS device 20 with pulsed light (Pu) that is phase-locked to the excitation signal. Since the vibration of the MEMS device 20 has the same frequency as the excitation signal, the pulsed light (Pu) is also synchronized with the MEMS vibration, and the phase difference between them can be modulated. θ in (a) represents the phase difference. In the vibration of the MEMS device 20, when it deviates from the equilibrium position, the shape of the surface of the MEMS device 20 changes, and the light intensity obtained by the differential interference microscope 10 is modulated. By irradiating the MEMS device 20 with such modulated pulsed light (Pu), a microscopic image can be acquired at a specific phase of the vibration of the MEMS device 20. Furthermore, by modulating the phase of the irradiated pulsed light (Pu), the entire vibration can be measured. Figure 5 (Figures 5A and 5B) shows the microscopic image and the light intensity graph. Image 5A(a) shows the microscopic image of the MEMS device 20 and the vibration measurement point (a1). The light intensity at (a1) is measured. In the graph 5B(b), the phase changes from 0° to 1080°, indicating that the light intensity changes periodically due to the vibration of the MEMS device 20.

[0028] The light source 14 uses a pulse-modulated LED or laser light source whose pulse width satisfies a predetermined measurable frequency band of the resonator related to the MEMS device 20. The principle of pulse width applied to the light source 14 is explained below.

[0029] To sample the resonant motion of the MEMS device 20, it is ideal to use narrow-width pulsed light. Since the measurement of vibrational motion is averaged over the time the pulsed light is incident, increasing the pulse width reduces the modulation of light intensity due to vibration. Figure 6 (Figures 6A and 6B) shows the measurable frequency range and the pulse width of the illumination light. Figure 6A(a) is a graph showing the frequency bandwidth of the light intensity modulation due to vibration. The frequency bandwidth (a1) is 1 / (30ns × 2) = approximately 17MHz. The pulse width ΔT of the light source 14 must be smaller than half the period T of the resonator of the MEMS device 20 (T / 2). Therefore, the measurable frequency bandwidth is given by equation (1) below. Frequency bandwidth = 1 / (2Δt) ···(1)

[0030] Figure 6B(b) is a graph showing the pulse width of the red LED (light source 14) used in the vibration analysis system 1. As shown in (b), Δt can achieve a pulse width of approximately 30 ns, which corresponds to a frequency bandwidth up to 16 MHz. Furthermore, by using a commercially available LED with a frequency bandwidth of 70 MHz for the light source 14, a higher frequency bandwidth can be achieved. It is possible to achieve the measurement frequency.

[0031] The function generator 16 outputs (applies) two synchronized voltage signals, using one voltage signal (vs1) for driving the MEMS device (vs1) and the other voltage signal (vs2) for modulating the pulsed light (Pu) of the light source 14. Therefore, the function generator 16 needs to be able to output voltage signals on at least two channels. In this embodiment, the function generator 16 is a device that can output arbitrary signals of 25 MHz on two channels. If a higher-end device is used, it is also possible to output signals of 240 MHz. The function generator 16 is an example of a signal source that applies a voltage signal of a predetermined frequency to the sample of this disclosure.

[0032] The control unit 18 is a computer that performs various controls related to the vibration analysis system 1. The control unit 18 performs controls related to the acquisition of microscope images by the digital camera 12, the output of voltage signals by the function generator 16, and the calculation of amplitude using the microscope images. By controlling the function generator 16, the control unit 18 sets the drive voltage and drive frequency of the resonator of the MEMS device 20 based on the voltage signal output from the function generator 16, and sets the phase sweep of the pulsed light (Pu) irradiated from the light source 14. This makes it possible to set the vibration of the MEMS device 20 to a specific phase. The drive voltage causes vibration of the MEMS device 20. As explained in the principle of measurement above, the light intensity obtained by the differential interference microscope 10 is modulated by the change in the shape of the surface of the MEMS device 20 that occurs when the MEMS device 20 shifts from its vibration equilibrium position. The control unit 18 causes the digital camera 12 to capture microscope images for each phase, thus representing a specific phase of the MEMS device 20. The control unit 18 also measures the overall vibration from the microscope images for each phase. Regarding the measurement method, measurements can be taken using the two measurement programs described later.

[0033] Figure 7 is a block diagram showing the hardware configuration of the control unit 18. As shown in Figure 7, the control unit 18 includes a CPU (Central Processing Unit) 111, a ROM (Read Only Memory) 112, a RAM (Random Access Memory) 13, storage 114, an input unit 115, a display interface (I / F) 116, and a communication interface (I / F) 117. Each component is connected to the others via a bus 119 so as to be able to communicate with each other.

[0034] The CPU 111 is a central processing unit that executes various programs and controls various parts. Specifically, the CPU 11 reads a program from the ROM 112 or 1114 and executes the program using the RAM 13 as a working area. The CPU 111 performs various calculations related to the above control according to the program stored in the ROM 12 or storage 114. In this embodiment, the ROM 112 or storage 114 stores a program.

[0035] ROM 112 stores various programs and data. RAM 113 temporarily stores programs or data as a working area. Storage 114 consists of a storage device such as an HDD (Hard Disk Drive) or SSD (Solid State Drive) and stores various programs, including the operating system, and various data.

[0036] The input unit 115 includes a pointing device such as a mouse and a keyboard, and is used for various types of input. The display interface 116 is, for example, a liquid crystal display and displays various types of information. The display interface 116 may also function as the input unit 115 by employing a touch panel method. The communication interface 117 is used for other devices such as terminals. It is an interface for communication between devices, and standards such as Ethernet®, FDDI, and Wi-Fi® are used.

[0037] Two measurement programs that can be executed in the control unit 18 will be described. Figure 8 shows the processing flow of the measurement programs, which is common to both measurement programs.

[0038] The first measurement program measures the resonant frequency of the MEMS device 20. As shown in Figure 8, in step S100, the CPU 111 sets the drive voltage of the resonator of the MEMS device 20. In step S102, the CPU 111 sets the range of drive frequencies for the resonator of the MEMS device 20. In step S104, the CPU 111 sets the sweep parameters based on the drive frequency range and the phase of the pulsed light to be irradiated, and sweeps to achieve each phase. Since the amplitude takes its maximum value at resonance, the frequency function of the calculated amplitude is used to determine the resonant frequency of the MEMS device 20. In other words, there are two sweep parameters in the first program: the drive frequency within the set range and the phase. A sweep is performed at each set drive frequency and the phase for each drive frequency. In step S106, the CPU 111 images the surface of the MEMS device 20 with the digital camera 12 and acquires a microscope image showing the resonance at each phase. Then, in step S108, the CPU 111 uses microscope images showing resonance at each phase to calculate the vibration amplitude at the drive frequency as the measurement target.

[0039] The microscope image is controlled so that at least three phases (0°, 120°, 240°, etc.) are captured during one period. Increasing the number of phases measured improves the signal-to-noise ratio. Note that the measurement time also increases with increasing the number of phases. Figure 9 shows the vibration amplitude measurement results plotted from the resonance spectrum of the MEMS beam measured when different drive voltages were applied to the MEMS device 20. The measured amplitude is the difference displacement at the measurement point (a1) in Figure 5 caused by the vibration. The excitation voltages were 20mV, 40mV, 60mV, 80mV, and 100mV. From the measurement results, it can be seen that the resonance frequency of the MEMS beam is approximately 696kHz. It has also been shown that increasing the drive voltage increases the frequency due to the nonlinear vibration of the MEMS beam, so the nonlinear vibration of the MEMS device 20 can also be analyzed by measurement.

[0040] The second measurement program measures the mode shape of the two-dimensional resonance of the MEMS device 20. The flow is the same as the first measurement program, so only the steps that differ will be explained. In the second measurement program, in step S102, the CPU 111 sets the drive frequency of the MEMS device 20 to the resonance frequency of the MEMS device 20. In step S104, the CPU 111 sets the sweep parameters based on the drive frequency set to the resonance frequency and the phase of the pulsed light to be irradiated, and sweeps to each phase. In step S108, the CPU 111 uses microscope images showing the resonance at each phase to calculate the mode shape of the resonance from the difference image of the vibration modes as the calculation of the measurement target.

[0041] In the second measurement program, the signal-to-noise ratio of the measurement can be improved by averaging multiple frames of the acquired microscope images. Figure 10 (Figures 10A, 10B, and 10C) shows the measurement results of the mode shapes. The shape of the first bending mode of the measured MEMS device is shown in Figure 10A(a). For comparison, the simulation results are shown in Figure 10B(b). Comparing Figure 10A(a) and Figure 10B(b), it can be confirmed that the measurement results are in very good agreement with the simulation results. Furthermore, the measurement result in Figure 10A(a) is the difference in the vibration mode shapes of the MEMS device 20, that is, the gradient of the displacement during vibration. Generally, the resonance mode can be determined by the gradient of the displacement, but it is also possible to derive the actual displacement. Integrating the difference result in Figure 10A(a) yields the actual mode shape in Figure 10C(c). This also shows good agreement with the simulation result in Figure 10B(b). Therefore, the second measurement program of the control unit 18 can analyze the two-dimensional shape of the resonance mode of the MEMS device 20 with high sensitivity.

[0042] As described above, the vibration analysis system 1 of this embodiment allows for vibration analysis of samples that generate minute vibrations while suppressing construction costs.

[0043] Furthermore, the vibration analysis system 1 can be used for analyses such as dynamic resonance analysis and static displacement measurement. These play an important role in processes such as characterization, operational verification, and failure analysis of the MEMS device 20.

[0044] The vibration analysis system 1 described above was explained as a standalone configuration equipped with each component for a differential interference microscope 10, but it is not limited to this. Such a standalone configuration is just one example of the vibration analysis apparatus of this disclosure. In the practical application of the technology of this disclosure, the vibration analysis system 1 is compact, easy to use, inexpensive, and high-performance, making it suitable for research and development of MEMS devices 20. Therefore, the vibration analysis system 1 can also be developed as an add-on module for the differential interference microscope 10. Since the differential interference microscope 10 accounts for a large portion of the cost of the vibration analysis system 1, the overall cost of the vibration analysis system 1 can be further reduced by adding the vibration analysis function of the control unit 18 to an existing differential interference microscope 10 through collaborative research with microscope manufacturers. Similarly, the digital camera 12, light source 14, and function generator 16 can also be made into add-on modules. Modularization in this way is also effective in disseminating the method of this disclosure through the microscope manufacturer's existing sales channels.

[0045] This disclosure is not limited to the embodiments described above, and various modifications and applications are possible without departing from the spirit of the invention.

[0046] The disclosure of Japanese Patent Application No. 2021-208457, filed on 22 December 2021, is incorporated herein by reference in its entirety. All documents, patent applications, and technical standards described herein are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard were specifically and individually noted to be incorporated by reference. [Explanation of Symbols]

[0047] 1. Vibration Analysis System 10 Differential Interference Microscope 12 Digital Cameras 14 Light source 16 Function Generators 18 Control Unit 20 MEMS devices

Claims

1. Using a differential interference microscope capable of measuring the protrusion and depression shapes on the sample surface within a predetermined measurement range by irradiating it with pulsed light branched through a differential interference prism, A sample driven by a voltage signal of a predetermined frequency is irradiated with the pulsed light modulated in phase synchronization with the voltage signal. A vibration analysis system for capturing a microscopic image of the aforementioned sample, Includes a control unit that performs predetermined control, The control unit controls the acquisition of the microscope image by the camera, the driving of the micro-vibration device which is the sample by outputting the voltage signal by the function generator, the modulation of the pulsed light, and the calculation of the amplitude using the microscope image. The control unit has a first measurement program and a second measurement program capable of performing calculations related to the amplitude. The first measurement program, in the control, sets the drive voltage of the micro-vibration device and sets the range of the drive frequency of the micro-vibration device. The first measurement program applies different drive voltages to the micro-vibration device during measurement, measures the vibration amplitude at each drive frequency included in the range of drive frequencies for each drive voltage, obtains a resonance spectrum by plotting the measured vibration amplitudes against the drive frequency, identifies the resonance frequency of the micro-vibration device based on the resonance spectrum, and displays the resonance spectrum as the vibration amplitude measurement result. The second measurement program, in the control, sets the drive frequency of the micro-vibration device to the specified resonant frequency, The second measurement program, in the measurement, obtains a difference image as the measurement result of the gradient of the displacement during vibration of the micro-vibration device for the vibration mode of the micro-vibration device in the microscope image at the resonant frequency, obtains an integral image of the simulated difference displacement from the difference image, obtains the actual mode shape by integrating the difference results of the difference image, and displays the difference image, the integral image, and the actual mode shape as the measurement results of the vibration mode. Vibration analysis system.

2. Using a differential interference microscope capable of measuring the protrusion and depression shapes on the sample surface within a predetermined measurement range by irradiating it with pulsed light branched through a differential interference prism, A sample driven by a voltage signal of a predetermined frequency is irradiated with the pulsed light modulated in phase synchronization with the voltage signal. A vibration analysis system for capturing a microscopic image of the aforementioned sample, As the light source for the pulsed light, a pulse-modulated LED or laser light source is used in which the pulse width Δt is less than half the period of the vibration of the sample and the measurable frequency band is 1 / (2Δt). Vibration analysis system.

3. The vibration analysis system according to claim 1 or claim 2, wherein the sample is a micro-vibration device whose size in the height and lateral directions is in millimeters or micrometers.

4. The vibration analysis system according to claim 1, wherein the pulse width of the pulsed light source is a pulse-modulated LED or laser light source that satisfies a predetermined frequency band that can be measured by the resonator of the sample.

5. Includes a control unit that performs predetermined control, The vibration analysis system according to claim 2, wherein the control unit controls the acquisition of the microscope image by the camera, the driving of the micro-vibration device which is the sample by outputting the voltage signal by the function generator, the modulation of the pulsed light, and the calculation of the amplitude using the microscope image.

6. In the control described above, The voltage signal output from the function generator sets the drive voltage and drive frequency of the resonator of the micro-vibration device, and sets the phase sweep of the pulsed light to be irradiated, thereby setting the vibration of the micro-vibration device to a specific phase. The vibration of the micro-vibration device causes it to shift from its equilibrium position, and the resulting change in the shape of the micro-vibration device's surface modulates the light intensity obtained by the differential interference microscope. The camera is made to capture the microscope images for each phase, The vibration analysis system according to claim 5, wherein the entire vibration is measured from the microscope images for each phase.

7. In the control described above, the drive frequency is set to the resonant frequency of the micro-vibration device. The vibration analysis system according to claim 6, wherein, in the measurement, the vibration amplitude at the resonant frequency is measured as a calculation related to the amplitude using the microscope image.

8. In the control described above, the drive frequency is set to the resonant frequency of the micro-vibration device. The vibration analysis system according to claim 6, wherein, in the measurement described above, the mode shape of the resonance is measured from the difference image of the vibration mode of the micro-vibration device in the microscope image at the resonance frequency, as a calculation of the amplitude using the microscope image.

9. A differential interference microscope capable of measuring the shape of protrusions and depressions on a sample surface within a predetermined measurement range by irradiating pulsed light branched through a differential interference prism, A signal source that applies a voltage signal of a predetermined frequency to a sample, A light source that irradiates the sample with the pulsed light modulated in phase synchronization with the voltage signal, An optical system for capturing a microscopic image of the aforementioned sample, A vibration analysis apparatus comprising a control unit that performs predetermined control, The control unit controls the acquisition of the microscope image by the camera, the driving of the micro-vibration device which is the sample by outputting the voltage signal by the function generator, the modulation of the pulsed light, and the calculation of the amplitude using the microscope image. The control unit has a first measurement program and a second measurement program capable of performing calculations related to the amplitude. The first measurement program, in the control, sets the drive voltage of the micro-vibration device and sets the range of the drive frequency of the micro-vibration device. The first measurement program applies different drive voltages to the micro-vibration device during measurement, measures the vibration amplitude at each drive frequency included in the range of drive frequencies for each drive voltage, obtains a resonance spectrum by plotting the measured vibration amplitudes against the drive frequency, identifies the resonance frequency of the micro-vibration device based on the resonance spectrum, and displays the resonance spectrum as the vibration amplitude measurement result. The second measurement program, in the control, sets the drive frequency of the micro-vibration device to the specified resonant frequency, The second measurement program, in the measurement, obtains a difference image as the measurement result of the gradient of the displacement during vibration of the micro-vibration device for the vibration mode of the micro-vibration device in the microscope image at the resonant frequency, obtains an integral image of the simulated difference displacement from the difference image, obtains the actual mode shape by integrating the difference results of the difference image, and displays the difference image, the integral image, and the actual mode shape as the measurement results of the vibration mode. Vibration analysis equipment.

10. The vibration analysis apparatus according to claim 9, wherein the sample is a micro-vibration device whose size in the height and lateral directions is in millimeters or micrometers.

11. The vibration analysis apparatus according to claim 9 or claim 10, wherein the light source includes a light-emitting diode or a laser light source.

12. The procedure involves irradiating a sample with pulsed light branched through a differential interference prism, using a differential interference microscope capable of measuring the protrusion and depression shapes on the sample surface within a predetermined measurement range, and The steps include applying a voltage signal of a predetermined frequency to the sample, The steps include irradiating the sample with the pulsed light modulated in synchronization with the voltage signal, The steps include: capturing a microscopic image of the sample; A vibration analysis method comprising the step of performing predetermined control, The aforementioned control is used to control the acquisition of the microscope image by the camera, the driving of the micro-vibration device which is the sample by outputting the voltage signal by the function generator, the modulation of the pulsed light, and the calculation of the amplitude using the microscope image. The control includes a first measurement program and a second measurement program capable of performing calculations related to the amplitude, The first measurement program, in the control, sets the drive voltage of the micro-vibration device and sets the range of the drive frequency of the micro-vibration device. The first measurement program applies different drive voltages to the micro-vibration device during measurement, measures the vibration amplitude at each drive frequency included in the range of drive frequencies for each drive voltage, obtains a resonance spectrum by plotting the measured vibration amplitudes against the drive frequency, identifies the resonance frequency of the micro-vibration device based on the resonance spectrum, and displays the resonance spectrum as the vibration amplitude measurement result. The second measurement program, in the control, sets the drive frequency of the micro-vibration device to the specified resonant frequency, The second measurement program, in the measurement, obtains a difference image as the measurement result of the gradient of the displacement during vibration of the micro-vibration device for the vibration mode of the micro-vibration device in the microscope image at the resonant frequency, obtains an integral image of the simulated difference displacement from the difference image, obtains the actual mode shape by integrating the difference results of the difference image, and displays the difference image, the integral image, and the actual mode shape as the measurement results of the vibration mode. Vibration analysis method.

Images