A vibration damping type thin film mechanical loss efficient measurement system and method

Abstract

The present application relates to a kind of vibration attenuation formula thin film mechanical loss measurement system and method, the system includes: the node suspension type support module being arranged in vacuum cavity, for providing the single-point contact condition of being tested piece under vacuum environment;Vibration excitation module, for providing the vibration excitation of set frequency for being tested piece;Light lever vibration detection module, for emitting laser to being tested piece and detecting reflected light spot to carry out vibration detection;Data acquisition and control processing module, for controlling vibration excitation module, and according to the light spot position information obtained by light lever vibration detection module, utilize the vibration free attenuation principle based on dynamic hysteresis elastic behavior, the mechanical loss change before and after the amplitude attenuation variation analysis of test piece coating is extracted to extract thin film mechanical loss.Compared with prior art, the present application has the advantages of simple structure, low contact loss, efficient measurement, high measurement accuracy.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of thin film parameter detection, and in particular to a vibration attenuation type thin film mechanical loss efficient measurement system and method. BACKGROUND

[0002] In an ultra-high precision laser measurement system, the instability requirement of laser frequency is that the change of optical resonant cavity length is about 10 -16 orders of magnitude, and the optical thin film thermal noise directly limits the sensitivity of the measurement system in the 30Hz to 500Hz frequency band. Since the ambient temperature of the measurement system is not absolute zero, the substrate and thin film material molecules of the cavity mirror in the optical resonant cavity are in random Brownian motion, resulting in fluctuation changes in the cavity length of the resonant cavity and generating thermal noise, in which the mechanical thermal noise of the thin film has a greater impact. In order to study and reduce the mechanical thermal noise of the thin film, it is necessary to measure and characterize the mechanical thermal noise, and the direct measurement device of the thin film thermal noise is complex and the data processing is cumbersome, which is not conducive to the process exploration of reducing the thin film thermal noise.

[0003] According to the fluctuation dissipation theory, the mechanical thermal noise of the thin film is positively correlated with its mechanical loss. When the thin film molecules perform Brownian motion, due to the internal friction between the molecules, there is mechanical impedance on the macroscopic level, and there is relative energy loss in the motion cycle, which is manifested as the viscoelasticity of the thin film material. This macroscopic process can be equivalently reproduced by applying stress to the thin film and observing the phase delay angle of the stress and strain over time, which is also known as mechanical loss. This measurement of mechanical loss is relatively easy, and the data processing is relatively simple. Therefore, the way of indirectly characterizing the thin film thermal noise by measuring the mechanical loss of the thin film is more efficient and more important.

[0004] Since 1940s, researchers have started to use vibration method to measure mechanical loss of test pieces, and obtain mechanical loss parameters by making test pieces vibrate mechanically and then observing changes or attenuation of vibration. At present, the existing non-node suspension support device for measuring mechanical loss either has strict requirements on test pieces or has large system contact loss, which is not conducive to efficient and accurate measurement of mechanical loss of thin films. Taking the existing torsional pendulum internal friction instrument as an example, the material to be measured needs to be made into a rod, one end of which is connected to a suspension fixing device, and the other end is connected to a torsional pendulum. The torsional pendulum internal friction instrument has the advantages of simple device, but has the disadvantages of: sample preparation is difficult, not suitable for mechanical loss testing of thin films plated under various processes, and the breaking strength of the material limits the universality of the test; there are many error sources, the test material needs to be fixedly connected with the device to a certain extent, resulting in more contact points, and the horizontal movement of the torsional pendulum may cause errors in the final mechanical loss measurement. In addition, in order to ensure the reliability of the measurement data, reduce the possible measurement deviation caused by the change of the contact points and positions of the test piece and the support part, and reduce the statistical error, it is often necessary to measure a test piece multiple times. However, the existing node suspension support test device abroad has the disadvantage of low efficiency of repeated measurement, and multiple measurements require the test piece to be taken out of the vacuum condition, removed from the silicon plano-convex lens, placed on the silicon plano-convex lens again, and then vacuumized. The waiting time for vacuumization and de-vacuumization is generally long, which greatly reduces the efficiency of repeated measurement. SUMMARY

[0005] The purpose of the present application is to provide a vibration attenuation type thin film mechanical loss efficient measurement system and method with simple structure, low contact loss, efficient measurement and high measurement accuracy.

[0006] The purpose of the present application can be achieved by the following technical solutions:

[0007] According to a first aspect of the present application, a vibration attenuation type thin film mechanical loss measurement system is provided, which comprises:

[0008] A node suspension support module arranged in the vacuum cavity, for providing a single-point contact condition for the test piece in a vacuum environment;

[0009] A vibration excitation module for providing vibration excitation of a set frequency for the test piece;

[0010] A light lever vibration detection module for emitting laser to the test piece and detecting the reflected light spot for vibration detection;

[0011] The data acquisition and control processing module is used for controlling the vibration excitation module, and based on the light spot position information obtained by the light lever vibration detection module, the vibration free decay principle based on dynamic hysteresis elastic behavior is used to analyze the change of the mechanical loss of the test piece before and after coating through the amplitude decay change to extract the mechanical loss of the thin film.

[0012] Preferably, the node suspension support module comprises a silicon plano-convex lens, a silicon plano-convex lens fixing plate, a silicon plano-convex lens support, a device base and a base heightening rod.

[0013] The silicon plano-convex lens is in contact with the silicon plano-convex lens support and is fixed by the silicon plano-convex lens fixing plate; the silicon plano-convex lens support is connected with the device base, and the device base is fixed in the vacuum cavity through the base heightening rod.

[0014] The test piece is placed on the silicon plano-convex lens and only contacts the silicon plano-convex lens at a single point.

[0015] Preferably, the system is further provided with a test piece re-contacting module, which comprises a centering ring, a centering ring support, a linear driver fixing nut and a linear driver.

[0016] The centering ring is fixedly connected with the centering ring support and is fixed on the device base.

[0017] The linear driver penetrates the central hole provided below the device base and is fixedly connected with the device base through the linear driver fixing nut.

[0018] The push rod of the linear driver is fixedly connected with the test piece node suspension support module, is used for loading and positioning the test piece and balancing the test piece, and repeatedly contacts and measures the test piece and the node suspension support module through up-down movement and collision under vacuum conditions.

[0019] Preferably, the push rod of the linear driver is fixedly connected with the test piece node suspension support module, specifically as follows:

[0020] The push rod of the linear driver fixed on the device base is inserted into the hole at the bottom of the silicon plano-convex lens support and is stopped, and the inserted push rod is fixed by rotating a screw into the hole at the side of the silicon plano-convex lens support, so that the test piece node suspension support module is connected with the device base as a whole.

[0021] Preferably, the light lever vibration detection module comprises a laser four-quadrant detector, a laser and a convex lens.

[0022] The laser and the laser four-quadrant detector are located above the vacuum cavity, the outgoing laser irradiates a certain point near the edge of the test piece through the observation window of the vacuum cavity, the light spot is reduced by the convex lens, and then the reflected light is received by the laser four-quadrant detector.

[0023] Preferably, the laser is a 633 nm laser.

[0024] Preferably, the vibration excitation module comprises, in sequence, an electrostatic excitation plate, a high-voltage amplifier and a signal generator.

[0025] The electrostatic excitation plate is fixed on the device base through the provided excitation plate support; the signal generator is connected with the data acquisition and control processing module.

[0026] Preferably, the electrostatic excitation plate is a comb-shaped parallel capacitor type electrostatic excitation plate.

[0027] Preferably, the data acquisition and control processing module comprises, in sequence:

[0028] A data acquisition card, used for acquiring the light spot position information obtained by the light lever vibration detection module;

[0029] A computer, used for controlling the vibration excitation module and analyzing and processing the information collected by the data acquisition card.

[0030] According to the second aspect of the present application, a vibration attenuation type thin film mechanical loss efficient measurement method is provided, characterized in that any one of the systems is used, and the method comprises the following steps:

[0031] 1) loading and balancing the test piece;

[0032] 2) finding the resonance frequency of the test piece through a white noise excitation signal;

[0033] 3) making the test piece resonate;

[0034] 4) performing vibration free attenuation after the test piece resonates;

[0035] 5) monitoring the vibration attenuation information of the test piece;

[0036] 6) calculating the mechanical loss parameters of the test piece by using the free attenuation principle;

[0037] 7) performing mechanical loss measurement after the test piece is re-contacted, i.e., repeating steps 3) to 6);

[0038] 8) performing mechanical loss measurement after the test piece is coated, i.e., repeating steps 1) to 7);

[0039] 9) extracting the mechanical loss of the thin film according to the dilution factor.

[0040] Compared with the prior art, the present application has the following advantages:

[0041] 1) The present application adopts a node suspension type test piece support part, compared with the existing torsional pendulum internal friction instrument and other non-node suspension type support devices, without additional film material preparation steps, the test piece sample preparation can be completed by plating the film on the substrate using the required research process, which can support different specifications, different material substrates and various thin film materials plated on them using various plating processes, and has the advantages of simple sample preparation; at the same time, the test piece is not fixedly connected with the measurement system, which is usually considered as single-point contact, and has the advantages of simple structure and low contact loss.

[0042] 2) The present application adopts a test piece multiple contact module, which facilitates test piece loading, positioning and balancing, optimizes the test piece multiple measurement method, reduces the time consumed by test piece loading and unloading, avoids multiple vacuum pumping and vacuum release steps, and greatly improves the efficiency of repeated measurement compared with the existing node suspension type support film mechanical loss test device. If the single vacuum pumping to the measurement required vacuum degree needs 2 hours, the single test piece mechanical loss measurement needs 0.5 hours, and the single vacuum release to atmospheric level needs 0.5 hours, the existing node suspension type support film mechanical loss test device needs 15 hours to complete 5 repeated tests, while the high-efficiency measurement system using the test piece multiple contact module only needs 5 hours to complete 5 repeated tests.

[0043] 3) The present application adopts an optical lever detection method, which amplifies the vibration amplitude of the test piece through the optical lever effect, thereby ensuring that the measurement system has high measurement accuracy and sensitivity. The measurement system excites the resonance mode of the test piece in the frequency band of 20Hz to 30kHz, and the deviation of the resonance frequency test result from the finite element simulation result is controlled within 0.5%, allowing the test to be performed on mechanical loss values above 2E-8. The repeatability of multiple measurements is also good, with a resonance frequency test repeatability deviation of only 0.01% and a mechanical loss test repeatability deviation controlled within 3%. BRIEF DESCRIPTION OF DRAWINGS

[0044] Figure 1 Figure 1 is a structural schematic diagram of the measurement system;

[0045] Figure 2 Figure 5 is a structural schematic diagram of the silicon plano-convex lens fixing plate;

[0046] Figure 3 Figure 6 is a structural schematic diagram of the silicon plano-convex lens support;

[0047] Figure 4 Figure 7 is a structural schematic diagram of the device base;

[0048] Figure 5 Figure 8 is a structural schematic diagram of the centering ring;

[0049] Figure 6Structure diagram of the centering ring support;

[0050] Figure 7 Structure diagram of the linear driver and the linear driver fixing nut;

[0051] Figure 8 Structure diagram of the comb-shaped parallel capacitor type electrostatic excitation plate;

[0052] Figure 9 Structure diagram of the excitation plate support;

[0053] Figure 10 General effect diagram of the installation of each part connected with the device base (in the low angle);

[0054] Figure 11 General effect diagram of the installation of each part connected with the device base (in the high angle);

[0055] Figure 12 Real-time monitoring curve of the vibration amplitude of the test piece;

[0056] Figure 13 COMSOL simulation of the vibration mode of the test piece;

[0057] The figure mark: 1 is a laser four-quadrant detector, 2 is a 633nm laser, 3 is a convex lens, 4 is a test piece, 5 is a silicon flat-convex lens, 6 is a centering ring, 7 is a centering ring support, 8 is a silicon flat-convex lens fixing piece, 9 is a silicon flat-convex lens support, 10 is a linear driver fixing nut, 11 is a device base, 12 is a linear driver, 13 is a base heightening rod, 14 is an excitation plate support, 15 is a comb-shaped parallel capacitor type electrostatic excitation plate, 16 is a high-voltage amplifier, 17 is a signal generator, 18 is a computer and 19 is a data acquisition card. DETAILED DESCRIPTION

[0058] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work should belong to the protection scope of the present application.

[0059] EMBODIMENT

[0060] The embodiment provides a vibration attenuation type thin film mechanical loss measurement system, and the system comprises:

[0061] The node suspension type support module arranged in the vacuum cavity is used for providing single-point contact conditions of the test piece 4 in a vacuum environment.

[0062] The vibration excitation module is used to provide vibration excitation at a set frequency to the test piece 4;

[0063] The optical lever vibration detection module is used to emit a laser to the test piece 4 and detect the reflected light spot to perform vibration detection;

[0064] The data acquisition and control processing module is used to control the vibration excitation module and, based on the spot position information obtained by the optical lever vibration detection module, uses the principle of vibration free decay based on dynamic hysteresis behavior to analyze the change in mechanical loss of the specimen before and after coating by the amplitude decay change in order to extract the mechanical loss of the thin film.

[0065] Next, the technical solution of the present invention will be described in detail with reference to the accompanying drawings.

[0066] like Figure 1 As shown in the figure, this embodiment provides a high-efficiency measurement system for thin-film mechanical loss using vibration attenuation, including a detection support module, a specimen re-contact module, a vibration excitation module, a vibration detection module, and an overall data acquisition and processing module. Each module includes a vacuum cavity, a laser four-quadrant detector 1, a 633nm laser 2, a convex lens 3, a specimen 4, a silicon plano-convex lens 5, a centering ring 6, a centering ring bracket 7, a silicon plano-convex lens fixing plate 8, a silicon plano-convex lens bracket 9, a linear actuator fixing nut 10, a device base 11, a linear actuator 12, a base elevation rod 13, an excitation plate bracket 14, a comb-type parallel capacitor electrostatic excitation plate 15, a high-voltage amplifier 16, a signal generator 17, a computer 18, and a data acquisition card 19. A schematic diagram of the main processing components is shown below. Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 , Figure 8 , Figure 9 As shown.

[0067] In this embodiment, the detection support module includes a vacuum chamber, a silicon plano-convex lens 5, a silicon plano-convex lens fixing plate 8, a silicon plano-convex lens bracket 9, a device base 11, and a base elevation rod 13. The silicon plano-convex lens 5 is inserted into the silicon plano-convex lens bracket 9. After the lens plane is in contact with the lens bracket, the lens 5 is fixed by connecting the silicon plano-convex lens fixing plate 8 and the lens bracket 9 with screws, thus forming a suspension support part for the specimen node.

[0068] Then, the push rod of the linear driver 12 fixed to the device base 11 is inserted into the bottom hole of the lens bracket 9 and held in place. The screw is screwed in from the side hole of the lens bracket 9 to fix the inserted push rod, thereby connecting the specimen node suspension support part with the device base 11 as a whole to form the specimen node suspension base part.

[0069] Finally, the device base 11 is fixed to the vacuum cavity through four base heightening rods 13 by screws to form a detection support module.

[0070] In this embodiment, the specimen recontact module comprises a centering ring 6, a centering ring support 7, a linear actuator fixing nut 10, and a linear actuator 12. The centering ring 6 is fixed to the centering ring support 7 by screws, and then is fixed to the device base 11 from the side hole by screws. The linear actuator 12 is inserted into the center hole from below the device base 11 and is fixed to the device base 11 by the linear actuator fixing nut 10. The push rod of the linear actuator 12 is fixed to the specimen node suspension support part, thereby forming the specimen recontact module.

[0071] The structure diagram of the linear actuator 12 and the linear actuator fixing nut 10 is shown in Figure 7 The specimen 4 is placed in the counterbore of the centering ring 6.

[0072] In this embodiment, the vibration excitation module comprises a comb-shaped parallel capacitor type electrostatic excitation plate 15, an excitation plate support 14, a high-voltage amplifier 16, and a signal generator 17. The circuit surface of the electrostatic excitation plate 15 is placed downward on the excitation plate support 14, and then is fixed to the excitation plate support 14 by screws and is fixed to the device base 11 from the side hole by screws. The signal generator 17 is connected to the high-voltage amplifier 16 through a coaxial connecting line, and then the high-voltage amplifier 16 is connected to the electrostatic excitation plate 15 through a coaxial connecting line, thereby forming the vibration excitation module, which can excite the resonance mode of the sample in the range of 20 Hz to 30 kHz.

[0073] The total installation effect diagram of each part connected to the device base is shown in Figure 10 , Figure 11 .

[0074] In this embodiment, the vibration detection module comprises a laser four-quadrant detector 1, a 633 nm laser 2, and a convex lens 3. The laser 2 and the laser four-quadrant detector 1 are located above the vacuum cavity. The outgoing laser irradiates a certain point near the edge of the specimen 4 through the observation window of the vacuum cavity, and then the light spot is reduced by the convex lens 3 and is reflected to the laser four-quadrant detector 1, which receives the light spot, thereby forming the light lever vibration detection module.

[0075] In this embodiment, the overall data acquisition and processing module comprises a computer 18 and a data acquisition card 19. The data acquisition and control processing module is connected to the laser four-quadrant detector 1, and then is connected to the computer 18, so that the signal change detected by the detector 1 is transmitted to the computer 18, and the computer 18 analyzes and processes the data to calculate the vibration relaxation time and then obtains the mechanical loss parameter of the specimen 4. The computer 18 is connected to the signal generator 17 and the linear actuator 12 through data lines, and is responsible for controlling the operation of the signal generator 17 and the linear actuator 12.

[0076] The film mechanical loss measurement method based on the above-mentioned film mechanical loss high-efficiency measurement system mainly includes nine steps:

[0077] A) Load and balance the test piece;

[0078] B) White noise excitation signal to find the resonance frequency of the test piece;

[0079] C) Resonate the test piece;

[0080] D) After the test piece resonates, the vibration free decay is carried out;

[0081] E) Monitor the vibration decay information of the test piece;

[0082] F) Calculate the mechanical loss parameters of the test piece by using the free decay principle;

[0083] G) After the test piece is re-contacted, the mechanical loss measurement is carried out, that is, steps C) to F) are repeated;

[0084] H) After the test piece is coated, the mechanical loss measurement is carried out, that is, steps A) to G) are repeated;

[0085] I) Extract the mechanical loss of the film according to the dilution factor.

[0086] Now taking a Φ76.2*1mm double-side polished JGS1 substrate, whose upper surface is coated with a 1018nm thick Ta2O5 film by ion beam sputtering, as an example, the film mechanical loss measurement method based on the above-mentioned film mechanical loss high-efficiency measurement system is described:

[0087] A) Load and balance the JGS1 substrate;

[0088] First, lower the push rod of the linear actuator to the lowest position, at this time the vertex of the silicon plano-convex lens is lower than the plain of the sink hole in the centering ring 6 bearing the test piece, put the JGS1 substrate in the sink hole, at this time the mass center of the JGS1 substrate is approximately on the same vertical line as the vertex of the silicon plano-convex lens; then perform vacuum treatment on the vacuum chamber to achieve a high-vacuum test environment, the vacuum degree needs to be lower than 1x10 -6 mbar; after the vacuum degree meets the requirements, the computer controls the push rod of the linear actuator to rise gradually, with a single step of 0.5mm, until the node suspension support part and the JGS1 substrate are lifted to a height where the JGS1 substrate is not in contact with the centering ring and the electrostatic excitation plate within the vibration motion range of the JGS1 substrate. At this time, the JGS1 substrate is placed horizontally and centrally on the top of the convex surface of the silicon plano-convex lens, in a balanced state and without additional contact except the silicon plano-convex lens.

[0089] B) White noise excitation signal to find the resonance frequency of the JGS1 substrate;

[0090] First, the signal generator produces a wide frequency white noise signal, the bandwidth is 30 kHz; then, the white noise signal through the high voltage amplifier to produce a large amplitude of the electrical signal after loading to the electrostatic excitation plate, amplification factor 250, through the excitation plate generated by the electric field on the JGS1 substrate to apply a wide frequency of random stress, vibration information of the JGS1 substrate real-time monitoring system during the light lever detection; the vibration information of the JGS1 substrate spectrum analysis, the peak value on the spectrum at this time is the approximate resonance frequency of the JGS1 substrate.

[0091] C) the JGS1 substrate resonance;

[0092] First, the signal generator 17 produces a narrow frequency sine wave oscillation scanning signal, the bandwidth is 3 Hz, the scanning signal frequency center is the approximate resonance frequency of each result found by white noise, the scanning signal amplitude at this time is 4V; then, the scanning signal through the high voltage amplifier 16 to amplify the amplitude, the amplification factor is 250, the generated large amplitude 1000V electrical signal after loading to the electrostatic excitation plate 15, through the excitation plate generated by the alternating electric field will be applied to the JGS1 substrate narrow frequency stress, during the light lever vibration detection system real-time monitoring JGS1 substrate vibration amplitude A s and vibration frequency f; when the JGS1 substrate appears the maximum amplitude A m , at this time it is considered to occur resonance, vibration frequency is the accurate resonance frequency f r . The results of four accurate resonance frequencies are shown in Table 1.

[0093] D) JGS1 substrate resonance vibration free decay;

[0094] When the JGS1 substrate appears the maximum amplitude A m , the signal generator signal output is turned off, there is no electrical signal loaded on the electrostatic excitation plate, the external excitation of the JGS1 substrate disappears, due to the high vacuum environment of the JGS1 substrate, the external damping of the JGS1 substrate can be ignored, at this time the JGS1 substrate will appear vibration free decay behavior under the influence of its own mechanical loss φ.

[0095] E) monitoring the JGS1 substrate vibration decay information;

[0096] The laser emitted by the laser passes through the observation window of the vacuum cavity and irradiates a certain point near the edge of the JGS1 substrate, and then is reflected to the four-quadrant detector after being reduced by the convex lens. When the JGS1 substrate vibrates, the position of the irradiation point will move, driving the reflected point on the four-quadrant detector to change at the same frequency. Moreover, due to the optical lever effect, the weak amplitude of the JGS1 substrate will also be proportionally amplified according to the reflection path. The change of the electrical signal of the four-quadrant detector, that is, the change of the normalized X and Y coordinate points of the reflected point on the detector, reflects the movement amplitude and frequency of the reflected point, and also reflects the vibration amplitude and frequency of the JGS1 substrate. The movement amplitude of the reflected point is calculated as The vibration amplitude of the JGS1 substrate is positively correlated with A s ∝A re When the JGS1 substrate starts to vibrate freely and attenuate, the vibration detection system can realize real-time monitoring of the vibration information of the JGS1 substrate. Moreover, due to the optical lever effect, the real-time vibration information can also be obtained when the vibration attenuates to a weak amplitude. The vibration monitoring curve of the resonance frequency of 1133.77 Hz is shown in Figure 12

[0097] F) Calculate the mechanical loss parameters of the JGS1 substrate by using the free attenuation principle;

[0098] When the JGS1 substrate freely attenuates, its amplitude changes exponentially A s =A m e -t / τ , wherein A s is the real-time amplitude, A m is the maximum amplitude, t is the vibration time after resonance, and τ is the vibration relaxation time. The vibration relaxation time τ can be obtained by fitting the amplitude monitoring curve, and then the mechanical loss parameters of the test piece can be calculated according to the relationship between the relaxation time and the mechanical loss φ:

[0099]

[0100] In the formula, f r is the resonance frequency, τ is the vibration relaxation time, is the mechanical loss at the resonance frequency. The parameter fitting is performed on the monitoring curve shown in Figure 12 , and the relaxation time of the substrate at the resonance frequency of 1133.77 Hz is 255.179 s, and the mechanical loss is 1.10E-06. The resonance frequencies and the corresponding mechanical loss results are shown in Table 1.

[0101] Table 1

[0102] Resonant frequency Substrate mechanical loss Coated substrate mechanical loss Thin film mechanical loss 1133.77 Hz 1.10E-06 ± 3.22E-08 rad 4.33E-06 ± 6.11E-08 rad 5.92E-04 rad 2604.93 Hz 1.19E-06 ± 8.71E-09 rad 4.91E-06 ± 5.89E-08 rad 6.70E-04 rad 4535.79 Hz 1.42E-06 ± 2.50E-08 rad 5.21E-06 ± 1.61E-08 rad 6.76E-04 rad 6911.30 Hz 1.51E-06 ± 1.94E-08 rad 5.16E-06 ± 8.70E-08 rad 6.45E-04 rad

[0103] G) After the JGS1 substrate is re-contacted, the mechanical loss measurement is performed again, that is, steps C) to F) are repeated; ​

[0104] After the mechanical loss measurement of the JGS1 substrate is completed, the vibration has weakened to the level that the optical lever vibration detection system cannot detect, and it is considered that the vibration behavior has stopped. At this time, the push rod of the linear drive controlled by the computer is gradually lowered, with a single step of 0.5 mm, until the JGS1 substrate falls into the counterbore of the centering ring again. The push rod continues to descend until the vertex of the silicon plano-convex lens is below the plane of the counterbore of the centering ring that carries the JGS1 substrate, i.e., the silicon plano-convex lens is separated from the JGS1 substrate. The slight collision of the JGS1 substrate with the plane of the counterbore of the centering ring causes a slight displacement of the JGS1 substrate relative to the silicon plano-convex lens. Then the push rod of the linear drive controlled by the computer is gradually raised, with a single step of 0.5 mm, until the JGS1 substrate is lifted to a height where it does not contact the centering ring and the electrostatic excitation plate within the vibration range of the JGS1 substrate. After the JGS1 substrate is re-contacted, mechanical loss measurement is performed again, and the mechanical loss parameters of the JGS1 substrate are obtained multiple times. By controlling the push rod of the linear drive with the computer, the effect of repeated contact of the test piece, multiple removal and reloading for measurement is achieved. The mechanical loss test repeatability deviation is maintained within 3% for 5 repetitions, as shown in Table 1.

[0105] H) After the JGS1 substrate is coated, mechanical loss measurement is performed again, i.e., steps A) to G) are repeated;

[0106] After the vacuum chamber is evacuated, the JGS1 substrate is removed, and an ion beam sputtering coating technology is used to coat a 1018 nm thick Ta2O5 film on the upper surface of the JGS1 substrate. After coating, the coated substrate is subjected to mechanical loss testing, and the mechanical loss parameters of the coated test piece are obtained multiple times. coated The number of repetitions is 5. The mechanical loss measurement results after coating and the deviation are shown in Table 1.

[0107] I) Extract the mechanical loss of the thin film according to the dilution factor.

[0108] Due to the difference in the stored elastic energy in the JGS1 substrate and the Ta2O5 film during vibration, the contributions of the mechanical loss of the substrate and the film to vibration attenuation are different. The dilution factor is calculated by COMSOL simulation software to obtain the elastic energy distribution:

[0109]

[0110] In the formula, D is the dilution factor, E coating is the elastic energy in the film, and E substrate is the elastic energy in the substrate. The vibration mode of the coated substrate at 1134.5 Hz simulated by COMSOL is shown in Figure 13 , and the remaining resonance frequencies and dilution factor results are shown in Table 2.

[0111] Table 2

[0112] Resonant frequency Dilution factor 1134.5 Hz 5.4585E-03 2604.2 Hz 5.5620E-03 4534.5 Hz 5.6261E-03 6911.8 Hz 5.6665E-03

[0113] The mechanical loss of the film can be calculated according to the dilution factor and the change of the mechanical loss parameter of the test piece before and after coating.

[0114]

[0115] In the formula, φ coating is the mechanical loss of the film, φ coated is the mechanical loss of the test piece after coating, and φ substrate is the mechanical loss of the substrate. The mechanical loss of the Ta2O5 film obtained is shown in Table 1.

[0116] The above merely provides a specific implementation of the present application, but the protection scope of the present application is not limited thereto, and any person skilled in the art can easily think of various equivalent modifications or replacements within the technical scope disclosed by the present application, and these modifications or replacements should be encompassed within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A vibration-damping type thin-film mechanical loss measurement system, characterized in that, The system includes: The node suspension support module set in the vacuum chamber is used to provide single-point contact conditions in a vacuum environment for the test piece (4); The vibration excitation module is used to provide vibration excitation at a set frequency to the test piece (4); The optical lever vibration detection module is used to emit a laser to the test piece (4) and detect the reflected light spot for vibration detection; The data acquisition and control processing module is used to control the vibration excitation module and, based on the spot position information obtained by the optical lever vibration detection module, uses the vibration free decay principle based on dynamic hysteresis behavior to analyze the change in mechanical loss of the specimen before and after coating by the amplitude decay change in order to extract the mechanical loss of the thin film. The node suspension support module includes a silicon plano-convex lens (5), a silicon plano-convex lens fixing plate (8), a silicon plano-convex lens bracket (9), a device base (11), and a base raising rod (13). After the silicon plano-convex lens (5) comes into contact with the silicon plano-convex lens bracket (9), it is fixed by the silicon plano-convex lens fixing piece (8); the silicon plano-convex lens bracket (9) is connected to the device base (11), and the device base (11) is fixed in the vacuum cavity by the base raising rod (13). The test piece (4) is placed on the silicon plano-convex lens (5) and only makes single-point contact with the silicon plano-convex lens (5); The system is also equipped with a specimen re-contact module, including a centering ring (6), a centering ring bracket (7), a linear actuator fixing nut (10), and a linear actuator (12). After the centering ring (6) is fixedly connected to the centering ring bracket (7), it is fixed to the device base (11). The linear actuator (12) passes through the central hole provided below the device base (11) and is fixedly connected to the device base (11) through the linear actuator fixing nut (10); The push rod of the linear actuator (12) is fixedly connected to the test piece node suspension support module, which is used to load, position and balance the test piece (4). Through up and down movement and collision, the test piece (4) and the node suspension support module are repeatedly contacted and repeatedly measured under vacuum conditions.

2. The vibration damping type thin-film mechanical loss measurement system according to claim 1, characterized in that, The push rod of the linear actuator (12) is fixedly connected to the specimen node suspension support module, specifically: Insert the push rod of the linear driver (12) fixed to the device base (11) into the bottom hole of the silicon plano-convex lens bracket (9) and hold it in place. Use a screw to screw in the side hole of the silicon plano-convex lens bracket (9) to fix the inserted push rod, and connect the specimen node suspension support module to the device base (11) as a whole.

3. The vibration damping type thin-film mechanical loss measurement system according to claim 1, characterized in that, The optical lever vibration detection module includes a laser quadrant detector (1), a laser (2), and a convex lens (3). The laser (2) and the laser quadrant detector (1) are located above the vacuum cavity. The emitted laser shines through the observation window of the vacuum cavity onto a point near the edge of the test piece (4), and after being reduced in size by the convex lens (3), it is reflected onto the laser quadrant detector (1) and received.

4. The vibration damping type thin-film mechanical loss measurement system according to claim 3, characterized in that, The laser (2) is a 633nm laser (2).

5. The vibration damping type thin-film mechanical loss measurement system according to claim 1, characterized in that, The vibration excitation module includes an electrostatic excitation plate (15), a high-voltage amplifier (16), and a signal generator (17) connected in sequence. The electrostatic excitation plate (15) is fixed on the device base (11) by the provided excitation plate bracket (14); The signal generator (17) is connected to the data acquisition and control processing module.

6. The vibration damping type thin-film mechanical loss measurement system according to claim 5, characterized in that, The electrostatic excitation plate (15) is a comb-shaped parallel capacitor type electrostatic excitation plate.

7. The vibration damping type thin-film mechanical loss measurement system according to claim 1, characterized in that, The data acquisition and control processing module includes the following components connected in sequence: Data acquisition card (19) is used to acquire the position information of the light spot obtained by the optical lever vibration detection module; The computer (18) is used to control the vibration excitation module and to analyze and process the information collected by the data acquisition card (19).

8. A high-efficiency method for measuring the mechanical loss of a thin film by vibration damping, characterized in that, Using the system according to any one of claims 1 to 7, the method includes the following steps: 1) Load and balance the test piece (4); 2) Use white noise excitation signal to find the resonant frequency of the test piece; 3) Cause the test piece (4) to resonate; 4) The test piece (4) undergoes free vibration decay after resonance; 5) Monitor the vibration attenuation information of the test piece (4); 6) Calculate the mechanical loss parameters of the specimen using the principle of free decay; 7) After the test piece (4) re-contacts, mechanical wear is measured again, i.e., steps 3) to 6) are repeated. 8) After coating the test piece (4), perform mechanical wear measurement, i.e., repeat steps 1) to 7). 9) Extract the mechanical loss of the film based on the dilution factor.

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