CN114425654A - A system and method for fabricating interdigital transducers for acoustic wave devices based on femtosecond laser processing masks - Google Patents

Abstract

The invention discloses a system and method for preparing an interdigital transducer for acoustic wave devices based on a femtosecond laser processing mask. The method utilizes a focused femtosecond laser to directly write the interdigital transducer mask on a metal film, and then The mask is placed on the piezoelectric substrate to evaporate metal, and finally the mask is removed to obtain the interdigital transducer structure. Compared with the traditional microelectronic photolithography process, the invention saves the processes of glue uniformization, drying, photolithography, development, peeling, etc., greatly simplifies the preparation process of the interdigital transducer, and has the advantages of low cost, simple process and green Due to the advantages of environmental protection, reusability, and easy mass production, it has broad application prospects in the preparation of large-wavelength and low-frequency acoustic wave microfluidic devices.

Description

A system and method for fabricating interdigital transducers for acoustic wave devices based on femtosecond laser processing masks

technical field

The invention relates to a system and method for preparing an interdigital transducer of an acoustic wave device based on a femtosecond laser processing mask, and belongs to the technical field of preparation of an acoustic wave device.

Background technique

SAW is an elastic wave that propagates along a solid surface. It was first discovered by British scientist Rayleigh in the process of studying seismic waves, so this kind of wave is also called Rayleigh wave. However, due to the limitation of the scientific level at that time, the initial surface acoustic wave research was mainly concentrated in the field of seismic waves, and it was not practically applied. Until 1965, American scientists White and Walthermer used the interdigital transducer to directly excite the surface acoustic wave by applying a radio frequency signal on the piezoelectric substrate. The invention of the interdigital transducer laid the foundation for the application of the surface acoustic wave. . With the advancement of technology, more surface acoustic waves have been discovered successively, including: horizontal shear wave, Love wave, Sishawar wave, etc. These waves generally need to be excited by interdigital transducers. At present, surface acoustic wave technology has been widely used in the fields of communication, electronics, quantum acoustics, sensing and microfluidics.

Among the many applications of surface acoustic wave technology, the application of surface acoustic wave in sensing and microfluidics is particularly noticeable in recent years, and is generally based on the Rayleigh mode in the acoustic wave mode, that is, Rayleigh wave, and the Rayleigh wave The excitation generally only needs to make a layer of metallized interdigital transducer (interdigital electrode pair) on the piezoelectric substrate. Generally speaking, for acoustic wave sensing, acoustic wave devices are often required to work at high frequencies, and high frequencies often correspond to smaller wavelengths, that is, smaller interdigital electrode widths, so high-precision, high-resolution device preparation is often used. rate of microelectronic lithography. For the use of acoustic wave devices as microfluidics, such as the realization of microfluidic drive, particle/cell separation, enrichment and other functions, the acoustic wave device is often required to work in a low frequency state, so the size of the interdigital electrode is large (hundred microns), no need for high Precision microelectronic lithography process.

At present, the preparation of the interdigital transducer (interdigital electrode) of the acoustic wave device still adopts the standard microelectronic lithography process. This process generally needs to go through the steps of uniform glue, drying, photolithography, development, evaporation, and peeling during the preparation process. and other steps, and need to be completed in a clean room. For the glue leveling process, it is generally necessary to adsorb the piezoelectric substrate on the glue machine and rotate at a high speed. For some flexible piezoelectric substrates (such as piezoelectric films grown on flexible substrates), it is not only difficult to adsorb on the glue machine, but also High-speed rotation will destroy the flatness of the substrate, thereby affecting the accuracy of lithography. At the same time, this process is generally only applied to plane processing due to the need for a glue gluer to do glue evenly. For the drying process, it is often necessary to heat the photoresist on the piezoelectric substrate to above 100°C, which will destroy the piezoelectric properties of the piezoelectric substrate for some piezoelectric substrates with poor temperature stability, such as PVDF. In addition, the development and stripping process in the microelectronic lithography process will produce chemical waste liquid to pollute the environment. Therefore, there is an urgent need for a low-cost, high-efficiency, simple process, and green and environmentally friendly preparation method for an interdigital transducer.

SUMMARY OF THE INVENTION

The invention provides a system and method for preparing an interdigital transducer of an acoustic wave device based on a femtosecond laser processing mask. Femtosecond laser processing technology has the advantages of high processing precision, small heat-affected zone, fast processing speed, simple operation and low cost, and is especially suitable for the rapid preparation of large-sized IDT masks. The mask of the interdigital transducer is directly written by the femtosecond laser, and then the mask pattern is transferred to the piezoelectric substrate to obtain the metallized interdigital electrode structure, which provides a better method for the rapid preparation of the interdigital transducer for acoustic wave devices. solution. In addition, due to the flexibility of the mask, the above method can realize the preparation of metal patterning on the curved surface, and in the preparation process, processes such as gluing, drying, photolithography, development, peeling, etc. are omitted, and no production will occur during the preparation process. Any chemical waste liquid pollutes the environment, and solves the problems of high cost, cumbersome process and complicated operation process in the process of preparing large-size interdigital transducers in the existing microelectronic lithography process.

A method for preparing an interdigital transducer for an acoustic wave device based on a femtosecond laser processing mask, comprising: taking a thin film as a processing object, using a femtosecond laser to process an interdigital transducer mask; The film is placed on the piezoelectric substrate, and the coating process is performed; after the coating is completed, the mask of the interdigital transducer is removed to obtain the interdigital electrode structure of the interdigital transducer.

Preferably, the method for preparing an interdigital transducer for an acoustic wave device based on a femtosecond laser processing mask includes the following steps:

S1: Build a femtosecond laser direct writing system, and use this system to directly write the interdigital transducer pattern on the thin film (such as a metal thin film) to obtain the interdigital transducer mask;

S2: fix the interdigital transducer mask on the piezoelectric substrate and place it in a metal coating system to evaporate metal;

S3: After the metal evaporation is completed, the interdigital transducer mask is removed from the piezoelectric substrate to obtain an interdigital transducer structure.

Preferably, the thin film is a metal thin film.

As a further preference, the metal thin film is aluminum foil or steel foil, and the thickness is 5-15 μm. As a further preference, the metal thin film is a steel foil with a thickness of 10 μm.

During processing, the film is fixed on the three-dimensional positioning mechanism by using positioning parts (such as tapes, clamps, etc.) It is composed of a moving one-dimensional manual stage. The combination of the two realizes the laser beam focusing and the patterned path scanning of the interdigital transducer. Specifically, by adjusting the distance from the metal film on the one-dimensional manual stage to the focusing element, the laser focus is placed on the top surface of the (metal) film, and the stage controller (or computer) is used to control the two-dimensional electric stage to scan the patterned path in turn. , the femtosecond laser directly writes the interdigital transducer pattern on the (metal) thin film to obtain a mask; in the area corresponding to the interdigital electrode of the interdigital transducer, the thin film material is removed under the action of the femtosecond laser.

Preferably, a stage controller for controlling the two-dimensional electric stage is also included.

Preferably, in the femtosecond laser direct writing process, the center wavelength of the femtosecond laser used is 900-1100 μm, the pulse width is 120-140 fs, the laser pulse repetition frequency is 1-3 kHz, and the processing power is 60-100 mW during the processing. The moving speed relative to the mask is 0.15 to 0.25 mm/s (or the moving speed of the two-dimensional electric stage is 0.15 to 0.25 mm/s). As a further preference, the center wavelength of the femtosecond laser is 1030 nm, the pulse repetition frequency is 2 kHz, the pulse width is 130 fs, the processing power is 80 mW, and the sample moving speed is 0.2 mm/s during the processing.

Preferably, an evaporation process is used for coating, and the thickness of the coating is 50-150 nm. As a further preference, the thickness of the metal thin film vapor deposition is 100 nm.

Preferably, the piezoelectric substrate can be selected from various existing piezoelectric substrate materials, including but not limited to LiNbO ₃ , LiTaO ₃ , PZT, PVDF, AlN, ZnO, and the like.

Preferably, the coating material is selected from gold, silver, copper, aluminum, molybdenum and the like.

(进一步优选为

)，镀膜厚度为50～100nm。待金属蒸镀完成后，撕去压电衬底和掩膜上的聚酰亚胺胶带，移除掩膜，获得叉指换能器的叉指电极结构。In actual processing, the interdigital transducer mask is fixed on the piezoelectric substrate with adhesive tape. For example, the interdigital transducer mask can be fixed on the piezoelectric substrate by polyimide adhesive tape. The above-mentioned piezoelectric substrate fixed with a mask is placed in a high-vacuum evaporation coating system to evaporate metal, and the thickness of metal evaporation is controlled by the coating time, and the evaporation speed is

(more preferably

), and the coating thickness is 50 to 100 nm. After the metal evaporation is completed, the polyimide tape on the piezoelectric substrate and the mask is torn off, and the mask is removed to obtain the interdigital electrode structure of the interdigital transducer.

Preferably, the minimum wavelength of the interdigital transducer mask is 120 μm, that is, the width of the interdigital electrode is more than 30 μm.

Preferably, the width of the interdigital electrodes is 30-300 microns, and as a further preference, the width of the interdigital electrodes is 30-150 microns.

A system for preparing an interdigital transducer of an acoustic wave device based on a femtosecond laser processing mask, comprising:

Femtosecond laser direct writing device for processing interdigital transducer masks;

A coating device for coating a piezoelectric substrate with an interdigital transducer mask fixed.

Preferably, the femtosecond laser direct writing device comprises:

Femtosecond lasers that provide femtosecond lasers;

A shutter element that controls the on-off of the laser beam;

Power adjustment element, to adjust the power of the femtosecond laser output laser;

The optical path collimation element is used to collimate and adjust the femtosecond laser beam;

Beam expanding element to expand the beam of the collimated femtosecond laser;

Optical path guide adjustment device, which guides the expanded femtosecond laser to climb and fall;

The focusing element focuses the guided beam, and the laser focused by the focusing element is irradiated vertically to the surface of the film to be processed to perform the femtosecond laser direct writing process.

Preferably, the shutter element is selected from an electric shutter or a mechanical shutter for controlling the on-off of the laser beam;

Preferably, the power adjustment element is selected from a neutral density attenuation plate or a combination of a half-wave plate and a polarizer, for adjusting the laser power;

Preferably, the optical path collimating element is two parallel total reflection mirrors, and the height and the left and right of the optical path are adjusted to make it parallel to the optical platform;

Preferably, the beam expanding element is composed of two confocally placed convex lenses, and the focal lengths of the two convex lenses are 40-80 mm and 100-200 mm respectively; as a further preference, the focal lengths of the two convex lenses are 50 mm and 150 mm, respectively.

Preferably, the optical path guide adjustment device is composed of three total reflection mirrors placed at 45 degrees, and two total reflection mirrors placed at 45 degrees are used to achieve vertical climbing and horizontal guidance of the optical path height; another total reflection mirror placed at 45 degrees is used to achieve vertical climbing and horizontal guidance; The mirror changes the direction of the light path by 90 degrees, and is vertically incident on the top surface of the metal film.

Preferably, the focusing element is a focusing lens (convex lens) with a focal length of 10-30 mm. As a further preference, the focal length of the focusing lens is 20mm.

As an optional solution, the femtosecond laser direct writing device further includes one or more combinations of the following elements:

one or more light path guiding elements;

Illumination source for illuminating the sample;

CCD camera used to assist in adjusting sample position and optical focusing;

a three-dimensional positioning mechanism for positioning the film;

A computer or controller for controlling the parameters of the femtosecond laser output laser or the movement path of the three-dimensional positioning mechanism.

As a specific choice, the illumination light source is a gooseneck lamp, which is used to illuminate the metal film, so that the CCD camera can clearly observe the laser focusing and processing process.

As a preferred solution, the femtosecond laser direct writing device used for preparing the interdigital transducer mask of the present invention includes: a femtosecond laser, and an electric shutter, a half-wave film, polarizer, two parallel total reflection mirrors (first total reflection mirror, second total reflection mirror), beam expander (ie, two confocally placed convex lenses), optical path guide adjustment device, focusing lens and fixed metal The three-dimensional positioning mechanism of the film. The one-dimensional manual stage in the three-dimensional positioning mechanism is used to adjust the focus of the laser on the metal film, and the stage controller controls the two-dimensional electric stage to move along the specified path in turn to complete the laser ablation and cutting, and obtain the interdigital transducer mask. . The laser focusing and direct writing process are recorded in real time by a CCD camera, which is connected to the computer through a signal line; the two-dimensional motorized stage is connected to the stage controller through a signal line; the femtosecond laser is connected to the computer through a signal line and controlled by the computer.

In actual work, the femtosecond laser passes through the shutter element, power adjustment, beam collimation, beam expansion, climbing, falling, and focusing, and the formed focused spot is irradiated vertically to the metal film, which is fixed on the two-dimensional electric displacement stage. On the one-dimensional manual displacement stage, the displacement stage controller controls the two-dimensional electric displacement stage in the three-dimensional positioning mechanism to move along the specified path in turn, and directly write the interdigital transducer mask.

During initial processing, the emitted laser energy of the femtosecond laser is initially adjusted by adjusting the pulse repetition frequency of the laser so that it is higher than the ablation threshold of the metal thin film. The laser power is further adjusted using a power adjustment element (a combination of a half-wave plate and a polarizer). Of course, when the experimental conditions are stable, the adjustment steps and adjustment elements can be omitted, and the final working parameters can be directly used for automatic processing. That is, as an optimized solution, the power adjustment element can be omitted.

A system and method for preparing an interdigital transducer of an acoustic wave device based on a femtosecond laser processing mask proposed by the present invention has the following advantages:

(1) The present invention utilizes the focused femtosecond laser to directly write the interdigital transducer pattern on the metal film, which can realize the low-cost, rapid, batch, and high-precision preparation of the interdigital transducer mask.

(2) Compared with the traditional microelectronic lithography process, the present invention omits processes such as glue uniformization, drying, photolithography, development, and stripping, the process is simple, the flexibility is high, and the minimum processing wavelength reaches 120 μm, which is especially suitable for low frequency. Low-cost and rapid fabrication of sonic microfluidic devices. At the same time, the high-temperature drying process is avoided, which is suitable for the preparation of metallized patterns on the heat-sensitive piezoelectric substrate, and avoids the generation of chemical waste liquid to pollute the environment.

(3) The mask of the present invention has high flexibility and can realize the preparation of metallized patterns on flexible or curved surfaces.

Description of drawings

1 is a schematic structural diagram of a femtosecond laser processing interdigital transducer mask device proposed by the present invention, wherein: 1 is a femtosecond laser, 2 is an electric shutter, 3 is a half-wave plate, 4 is a polarizer, and 5 is a full Mirror, 6 is total reflection mirror, 7 is convex lens, 8 is convex lens, 9 is total reflection mirror, 10 is total reflection mirror, 11 is total reflection mirror, 12 is focusing lens, 13 is metal film, 14 is one-dimensional manual displacement stage, 15 is a two-dimensional motorized stage, 16 is a stage controller, 17 is a gooseneck lamp, 18 is a CCD camera, and 19 is a computer.

FIG. 2 is a physical diagram of the interdigital transducer masks with different wavelengths processed by the present invention, wherein (a) the wavelength is 400 μm; (b) the wavelength is 300 μm; (c) the wavelength is 200 μm.

Fig. 3 is the flow chart of preparing the interdigital transducer of the acoustic wave device according to the present invention.

Figure 4 is a physical diagram of acoustic wave devices prepared on different piezoelectric substrates according to the present invention, wherein (a) LiNbO ₃ substrate, the device wavelength is 400 μm; (b) LiNbO ₃ substrate, the device wavelength is 300 μm; (c) PVDF substrate Bottom (500 μm thick), device wavelength 300 μm; (d) PVDF substrate (200 μm thick), device wavelength 300 μm.

Figure 5 shows the signal transmission and reflection spectra of acoustic wave devices (wavelength 400 μm) prepared on different piezoelectric substrates of the present invention, wherein (a) LiNbO ₃ substrate; (b) PVDF substrate.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below through specific embodiments in conjunction with the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention.

The invention provides a system and method for preparing an interdigital transducer of an acoustic wave device based on a femtosecond laser processing mask. In the processing method, the interdigital transducer mask is directly written on the metal film by the focused femtosecond laser, and then the mask is placed on the piezoelectric substrate to evaporate metal to obtain the interdigital electrode structure; in the preparation process , Compared with the traditional microelectronic lithography process, the present invention omits the processes of uniform glue, drying, photolithography, development, stripping, etc., which greatly simplifies the preparation process, and the prepared mask has low cost, high precision, and can be realized reuse.

A system and method for preparing an interdigital transducer of an acoustic wave device based on a femtosecond laser processing mask proposed by the present invention, the optical path structure of the femtosecond laser direct writing device is shown in Figure 1, including: a femtosecond laser 1, an electric shutter 2. Half-wave plate 3, polarizer 4, total reflection mirror 5, total reflection mirror 6, convex lens 7, convex lens 8, total reflection mirror 9, total reflection mirror 10, total reflection mirror 11, focusing lens 12, metal film 13, One-dimensional manual stage 14 , two-dimensional electric stage 15 , stage controller 16 , gooseneck lamp 17 , CCD camera 18 and computer 19 .

The electric shutter 2 is mainly used to control the on-off of the laser beam, and the setting position can be adjusted according to actual needs.

The optical half-wave plate 3 and the polarizer 4 are used in combination, mainly for adjusting the laser power, and can also be replaced with other power adjusting elements, such as a neutral density attenuation plate.

The total reflection mirror 5 and the total reflection mirror 6 are placed in parallel, mainly adjust the pitch and left and right of the laser optical path, and play the role of optical path collimation. The total reflection mirror 5 and the total reflection mirror 6 can be increased or decreased according to actual needs. It can be adjusted according to actual needs before laser beam expansion.

The convex lens 7 and the convex lens 8 are placed confocally and mainly play the role of beam expansion.

The total reflection mirror 9, the total reflection mirror 10, and the total reflection mirror 11 mainly play a guiding role in raising and falling of the optical path. The total reflection mirror 9 changes the direction of the laser light path by 90 degrees, from horizontal propagation to vertical climbing, The total reflection mirror 10 changes the direction of the vertically climbing laser light path by 90 degrees to horizontally propagate, and the total reflection mirror 11 changes the direction of the horizontally propagated laser light path by 90 degrees, and vertically enters the center of the focusing lens 12 .

The focusing lens 12 mainly plays the role of focusing the light beam, and the focused laser is vertically incident on the surface of the metal film 13 to be processed.

The metal film 13 is fixed on the three-dimensional positioning mechanism by tape, and the three-dimensional positioning mechanism is composed of a one-dimensional manual displacement stage 14 and a two-dimensional electric displacement stage 15, and the one-dimensional manual displacement stage 14 is installed on the two-dimensional electric displacement stage. 15, the two-dimensional electric stage 15 is connected to the stage controller 16 through a signal line, and is controlled by the stage controller 16 (of course, if the software is compatible and the function allows, it can also be controlled by the computer 19 uniformly). The one-dimensional manual displacement stage 14 is mainly used to adjust the distance between the focusing lens 12 and the metal film 13 to be processed, so that the laser focus is on the top surface of the metal film 13 to be processed, and the two-dimensional electric displacement stage 15 is mainly used to realize the metal film to be processed during the processing. The horizontal direction of the film 13 moves to form a patterned cutting path.

The gooseneck lamp 17 is used for illuminating the metal film 13 , so as to observe the focusing of the metal film 13 by the focusing lens 12 under the CCD camera 18 and monitor the whole process in real time.

The CCD camera 18 is connected to the computer 19 through a signal line, and is imaged in real time by the computer 19 screen. The femtosecond laser 1 is connected to the computer 19 through a signal line, and is controlled by the computer 19 .

Before processing, first place the relevant optical components into the optical platform in the order shown in Figure 1 to build a femtosecond laser direct writing optical path. During the processing, the femtosecond laser 1 generates a femtosecond laser. The femtosecond laser first passes through the electric shutter 2, and then is adjusted to an appropriate power by the half-wave plate 3 and the polarizer 4, and then is incident on the total reflection mirror 5, and then passes through the total reflection mirror. 5 and the total reflection mirror 6 are aligned with the laser light path, and the reflected laser is vertically incident on the beam expansion system composed of the convex lens 7 and the convex lens 8. After the beam expansion, the femtosecond laser first climbs vertically through the total reflection mirror 9, and then passes through the total reflection. The mirror 10 propagates horizontally, and finally enters the focusing lens 12 vertically downward through the total reflection mirror 11, and adjusts the distance from the metal film 13 on the one-dimensional manual displacement stage 14 to the focusing lens 12, so that the laser focus is on the top surface of the metal film 13, and the displacement is The stage controller 16 controls the metal thin film 13 on the two-dimensional electric displacement stage 15 to move along the specified path in sequence to complete the scanning and cutting, and obtain the interdigital transducer mask. Then, after coating and removing the mask, the interdigital electrode structure of the interdigital transducer can be obtained.

Example 1: Femtosecond laser direct writing processing of an interdigital transducer mask.

In the embodiment of the present invention, the femtosecond laser used is a ytterbium-doped femtosecond fiber laser (Tangerine HP) of Amplitude Company, the center wavelength of the femtosecond laser is 1030 nm, the pulse width is 130 fs, the maximum repetition frequency is 35 MHz, the single pulse energy is 200 μJ, and the light field distribution is Gaussian distribution; the metal film used is a steel foil with a thickness of 10 μm and a size of 5cm×5cm. As an alternative, the steel foil can also be replaced with aluminum foil or other metal films.

The concrete processing steps of this embodiment are as follows:

S1: The computer 19 completes the group-based movement path programming of the interdigital transducer mask, and writes the path program into the two-dimensional stage controller 16 through the SD memory card;

S2: fix the steel foil 13 on the three-dimensional positioning mechanism composed of the one-dimensional manual displacement stage 14 and the two-dimensional electric displacement stage 15 by tape;

S3: The computer 19 controls the femtosecond laser 1 to emit pulsed laser light, and the optical elements are placed in the optical platform in the order shown in Figure 1, and the optical path is adjusted so that the femtosecond laser passes through the electric shutter 2, the half-wave plate 3, the polarizer 4, and the total reflection mirror. 5. The total reflection mirror 6, the convex lens 7, the convex lens 8, the total reflection mirror 9, the total reflection mirror 10, the total reflection mirror 11 and the focusing lens 12 are vertically incident on the surface of the steel foil 13, and the pulse repetition frequency of the femtosecond laser is set is 2kHz, and the polarizer is rotated so that the average laser power is 80mW.

S4 : Turn on the gooseneck lamp 17 to illuminate the steel foil 13 , adjust the longitudinal feed of the one-dimensional manual displacement stage 14 under the CCD camera 18 , so that the femtosecond laser is focused by the focusing lens 12 on the top surface of the steel foil 13 .

S5: Set the feeding speed of the two-dimensional electric stage 15 to 0.2 mm/s, and the stage controller 16 sequentially loads the program described in step S1, so that the two-dimensional electric stage 15 drives the steel foil 13 on it in turn along the specified The path movement completes the scan cut and obtains the interdigital transducer mask.

Fig. 2 is the actual picture of the interdigital transducer masks with different wavelengths processed by the present invention, wherein (a) the wavelength is 400 μm, the number of pairs of interdigital electrodes is 15, and the acoustic aperture is 6000 μm; (b) the wavelength is 300 μm, The number of electrode pairs is 15, and the acoustic aperture is 5000 μm; (c) The wavelength is 200 μm, the number of electrode pairs is 5, and the acoustic aperture is 3000 μm.

Example 2: Fabrication of an interdigital transducer for acoustic wave devices based on a femtosecond laser processing mask.

金属蒸镀厚度为100nm。作为一种替代的方案，金属蒸镀亦可通过真空溅射镀膜设备实现。In the embodiment of the present invention, the metal coating equipment used is the high-vacuum evaporation coating system of Aifake Vacuum Technology (Suzhou) Co., Ltd. During the coating process, the vacuum degree of the cavity is 5×10 ^-4 Pa, and the evaporation rate is

The metal vapor deposition thickness was 100 nm. As an alternative solution, metal evaporation can also be achieved by vacuum sputtering coating equipment.

The concrete processing steps of this embodiment are as follows:

S1: fix the interdigital transducer mask on the piezoelectric substrate through polyimide tape;

蒸镀时间为33min，即镀膜厚度为100nm。S2: Place the piezoelectric substrate fixed with the interdigital transducer mask in a high-vacuum evaporation coating system to evaporate gold film, and set the metal evaporation speed

The evaporation time is 33min, that is, the coating thickness is 100nm.

S3: After the evaporation is completed, the mask is removed to obtain the interdigital electrode structure of the interdigital transducer of the acoustic wave device.

Fig. 3 is the flow chart of preparing the interdigital transducer of acoustic wave device according to the present invention. First, the mask is directly written by the focused femtosecond laser, then the mask is fixed on the piezoelectric substrate, and then the piezoelectric substrate and the mask are placed Metal is evaporated in a high vacuum evaporation coating system, and finally the mask is removed to obtain an interdigital transducer structure.

Figure 4 is a physical diagram of acoustic wave devices prepared on different piezoelectric substrates according to the present invention, wherein (a) LiNbO ₃ substrate, the number of pairs of interdigital electrodes is 15, the wavelength is 400 μm, and the acoustic aperture is 6000 μm; (b) LiNbO ₃ Substrate, the number of pairs of interdigital electrodes is 15, the wavelength is 300 μm, and the acoustic aperture is 5000 μm; (c) PVDF substrate (500 μm thick), the number of pairs of interdigital electrodes is 15, the wavelength is 300 μm, and the acoustic aperture is 5000 μm; ( d) PVDF substrate (200 μm thick) with 15 pairs of interdigital electrodes, a wavelength of 300 μm, and an acoustic aperture of 5000 μm.

Figure 5 is the signal transmission and reflection spectra of acoustic wave devices (wavelength is 400 μm) prepared on different piezoelectric substrates according to the present invention, wherein (a) LiNbO ₃ substrate, the mode excited by the acoustic wave is Rayleigh (R0) mode; (b) PVDF substrate, the mode excited by the acoustic wave is the zero-order antisymmetric (A0) mode.

The above content is a further detailed description of the present invention in conjunction with specific embodiments, and it cannot be considered that the specific implementation of the present invention is limited to these descriptions. For those of ordinary skill in the technical field of the present invention, without departing from the concept of the present invention, some simple deductions or substitutions can be made, which should be regarded as belonging to the protection scope of the present invention.

Claims (9)

1. A method for manufacturing an acoustic wave device interdigital transducer based on a femtosecond laser processing mask is characterized by comprising the following steps: processing an interdigital transducer mask by using femtosecond laser by taking the film as a processing object; then, placing the mask on a piezoelectric substrate, and performing film coating processing; and after the film coating is finished, removing the interdigital transducer mask to obtain the interdigital electrode structure of the interdigital transducer.

2. The method for fabricating an acoustic wave device interdigital transducer based on a femtosecond laser process mask according to claim 1, wherein the thin film is a metal thin film.

3. The method for manufacturing an acoustic wave device interdigital transducer based on a femtosecond laser processing mask according to claim 2, wherein the metal thin film is an aluminum foil or a steel foil and has a thickness of 5-15 μm.

4. The method for fabricating an acoustic wave device interdigital transducer based on a femtosecond laser process mask according to claim 1, wherein in the femtosecond laser direct writing process, the center wavelength of the femtosecond laser used is 900 to 1100 μm, the pulse width is 120 to 140fs, the laser pulse repetition frequency is 1 to 3kHz, the process power is 60 to 100mW, and the relative movement speed with the mask is 0.15 to 0.25 mm/s.

5. The method for fabricating an acoustic wave device interdigital transducer based on a femtosecond laser process mask according to claim 1, wherein the interdigital electrode width of the interdigital transducer is 30 μm or more.

6. The method for manufacturing an acoustic wave device interdigital transducer based on a femtosecond laser processing mask, according to claim 1, wherein the metal coating is performed by an evaporation process, and the coating thickness is 50-150 nm.

7. A system for fabricating acoustic wave device interdigital transducers based on a femtosecond laser processed mask, comprising:

the femtosecond laser direct writing device is used for processing the interdigital transducer mask;

and a coating device for coating the piezoelectric substrate fixed with the interdigital transducer mask.

8. The system for fabricating an acoustic wave device interdigital transducer based on a femtosecond laser process mask according to claim 7, wherein the femtosecond laser direct writing apparatus comprises:

a femtosecond laser providing femtosecond laser;

the shutter element is used for controlling the on-off of the laser emitted by the femtosecond laser;

the power adjusting element is used for adjusting the power of the laser emitted by the femtosecond laser;

the light path collimation element is used for collimating and adjusting the femtosecond laser;

the beam expanding element is used for expanding the collimated femtosecond laser;

the light path guiding and adjusting device is used for guiding the expanded femtosecond laser to climb and fall;

and the focusing element is used for focusing the guided light beam and vertically irradiating the light beam to the surface of the film to be processed to perform the femtosecond laser direct writing processing.

9. The system for fabricating an acoustic wave device interdigital transducer based on a femtosecond laser process mask according to claim 7, wherein the femtosecond laser direct writing apparatus further comprises one or more combinations of the following elements:

one or more optical path directing elements;

an illumination light source;

a CCD camera for assisting in adjusting the position of the sample and optically focusing;

a three-dimensional positioning mechanism for positioning the film;

and the computer or the controller is used for controlling the parameters of the emergent laser of the femtosecond laser and the moving path of the three-dimensional positioning mechanism.

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