CN114425654A - System and method for preparing acoustic wave device interdigital transducer based on femtosecond laser processing mask - Google Patents
System and method for preparing acoustic wave device interdigital transducer based on femtosecond laser processing mask Download PDFInfo
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- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K26/00—Working by laser beam, e.g. welding, cutting or boring
- B23K26/36—Removing material
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K26/00—Working by laser beam, e.g. welding, cutting or boring
- B23K26/02—Positioning or observing the workpiece, e.g. with respect to the point of impact; Aligning, aiming or focusing the laser beam
- B23K26/06—Shaping the laser beam, e.g. by masks or multi-focusing
- B23K26/064—Shaping the laser beam, e.g. by masks or multi-focusing by means of optical elements, e.g. lenses, mirrors or prisms
- B23K26/0643—Shaping the laser beam, e.g. by masks or multi-focusing by means of optical elements, e.g. lenses, mirrors or prisms comprising mirrors
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K26/00—Working by laser beam, e.g. welding, cutting or boring
- B23K26/02—Positioning or observing the workpiece, e.g. with respect to the point of impact; Aligning, aiming or focusing the laser beam
- B23K26/06—Shaping the laser beam, e.g. by masks or multi-focusing
- B23K26/064—Shaping the laser beam, e.g. by masks or multi-focusing by means of optical elements, e.g. lenses, mirrors or prisms
- B23K26/0648—Shaping the laser beam, e.g. by masks or multi-focusing by means of optical elements, e.g. lenses, mirrors or prisms comprising lenses
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- B—PERFORMING OPERATIONS; TRANSPORTING
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- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K26/00—Working by laser beam, e.g. welding, cutting or boring
- B23K26/08—Devices involving relative movement between laser beam and workpiece
- B23K26/082—Scanning systems, i.e. devices involving movement of the laser beam relative to the laser head
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- B—PERFORMING OPERATIONS; TRANSPORTING
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- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K26/00—Working by laser beam, e.g. welding, cutting or boring
- B23K26/70—Auxiliary operations or equipment
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Abstract
The invention discloses a system and a method for preparing an acoustic wave device interdigital transducer based on a femtosecond laser processing mask. Compared with the traditional microelectronic photoetching process, the preparation method of the interdigital transducer has the advantages of low cost, simple and convenient process, environmental protection, reusability, easiness in large-scale production and the like, saves the processes of spin coating, drying, photoetching, developing, stripping and the like, greatly simplifies the preparation process of the interdigital transducer, and has wide application prospect in the preparation of large-wavelength and low-frequency acoustic wave microfluidic devices.
Description
Technical Field
The invention relates to a system and a method for preparing an acoustic wave device interdigital transducer based on a femtosecond laser processing mask, belonging to the technical field of acoustic wave device preparation.
Background
Surface acoustic wave is an elastic wave that propagates along a solid surface, and was first discovered by british scientists rayleigh in the study of seismic waves, so this wave is also known as rayleigh wave. However, due to the limitation of the scientific level at that time, the initial surface acoustic wave research mainly focuses on the seismic wave field and is not practically applied. Until 1965, american scientists, white and volmer, used interdigital transducers to directly excite surface acoustic waves by applying radio frequency signals on a piezoelectric substrate, and the invention of the interdigital transducers laid the foundation of surface acoustic wave application. As technology advances, more surface acoustic waves are successively discovered, including: horizontal shear waves, love waves, sizawa waves, and the like, which generally require interdigital transducer excitation. At present, the surface acoustic wave technology has been widely applied in the fields of communication, electronics, quantum acoustics, sensing, microfluid and the like.
In many applications of the surface acoustic wave technology, the application of the surface acoustic wave in sensing and microfluidics is particularly focused in recent years, and the surface acoustic wave is generally based on a rayleigh mode, i.e. a rayleigh wave, among acoustic wave modes, and the excitation of the rayleigh wave generally only needs to make a layer of metalized interdigital transducers (interdigital electrode pairs) on a piezoelectric substrate. Generally, for acoustic wave sensing, an acoustic wave device is required to operate at a high frequency, and the high frequency corresponds to a smaller wavelength, i.e., a smaller interdigital electrode width, so a high-precision and high-resolution microelectronic lithography process is often used for device fabrication. For the application of the acoustic wave device as microfluid, for example, the functions of microfluid driving, particle/cell separation, enrichment and the like are realized, the acoustic wave device is often required to work in a low-frequency state, so that the interdigital electrode has a large size (hundreds of microns) and does not need a high-precision microelectronic photoetching process.
At present, the preparation of the interdigital transducer (interdigital electrode) of the acoustic wave device still adopts a standard microelectronic photoetching process, and the process generally needs steps of glue homogenizing, drying, photoetching, developing, vapor plating, stripping and the like in the preparation process and needs to be completed in an ultra-clean room. For the spin coating process, the piezoelectric substrate generally needs to be adsorbed on the spin coating machine to rotate at a high speed, which is difficult to adsorb on some flexible piezoelectric substrates (such as piezoelectric thin films grown on the flexible substrates), and the high-speed rotation may damage the flatness of the substrate, thereby affecting the precision of the photolithography processing. Meanwhile, the process is generally only applied to plane processing because a spin coater is required for spin coating. For the baking process, the photoresist on the piezoelectric substrate is often required to be heated to more than 100 ℃, which may destroy the piezoelectric characteristics of the piezoelectric substrate for some piezoelectric substrates with poor temperature stability, such as PVDF. In addition, the development and stripping processes in the microelectronic photolithography process can generate chemical waste liquid to pollute the environment. Therefore, a method for manufacturing an interdigital transducer, which has the advantages of low cost, high efficiency, simple process and environmental protection, is needed.
Disclosure of Invention
The invention provides a system and a method for preparing an acoustic wave device interdigital transducer based on a femtosecond laser processing mask. The femtosecond laser processing technology has the advantages of high processing precision, small heat affected zone, high processing speed, simple operation and low cost, and is particularly suitable for the rapid preparation of large-size interdigital transducer masks. The femtosecond laser is used for directly writing out the interdigital transducer mask, and then the mask pattern is transferred to the piezoelectric substrate to obtain the metallized interdigital electrode structure, thereby providing a better solution for the rapid preparation of the interdigital transducer of the acoustic wave device. In addition, due to the flexibility of the mask, the method can realize the preparation of the metal patterning on the curved surface, and the processes of glue homogenizing, drying, photoetching, developing, stripping and the like are omitted in the preparation process, so that no chemical waste liquid is generated in the preparation process to pollute the environment, and the problems of high cost, complicated process and complex operation process in the process of preparing the large-size interdigital transducer by the conventional microelectronic photoetching process are solved.
A method for manufacturing an acoustic wave device interdigital transducer based on a femtosecond laser processing mask comprises the following steps: processing an interdigital transducer mask by using femtosecond laser by taking the film as a processing object; then, placing an interdigital transducer mask on a piezoelectric substrate, and carrying out 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.
Preferably, the method for preparing the acoustic wave device interdigital transducer based on the femtosecond laser processing mask comprises the following steps:
s1: constructing a femtosecond laser direct writing system, and directly writing an interdigital transducer pattern on a film (such as a metal film) by using the system to obtain an interdigital transducer mask;
s2: fixing an interdigital transducer mask on a piezoelectric substrate and placing the interdigital transducer mask in a metal coating system to evaporate metal;
s3: and after the metal evaporation is finished, removing the interdigital transducer mask from the piezoelectric substrate to obtain the interdigital transducer structure.
Preferably, the film is a metal film.
More preferably, the metal film is an aluminum foil or a steel foil, and the thickness is 5 to 15 μm. More preferably, the metal thin film is a steel foil having a thickness of 10 μm.
When in processing, a film is fixed on a three-dimensional positioning mechanism by utilizing a positioning piece (such as an adhesive tape, a clamp and the like), the three-dimensional positioning mechanism consists of a two-dimensional electric displacement table for realizing horizontal direction (XY) movement and a one-dimensional manual displacement table for realizing longitudinal direction (Z) movement, and the two tables are combined to realize laser beam focusing and interdigital transducer patterning path scanning. Specifically, the distance from a metal film on a one-dimensional manual displacement table to a focusing element is adjusted to enable the laser focus to be positioned on the top surface of the (metal) film, a displacement table controller (or a computer) is utilized to control a two-dimensional electric displacement table to sequentially complete the scanning of a patterning path, femtosecond laser is enabled to directly write an interdigital transducer pattern on the (metal) film, and a mask is obtained; wherein, in the corresponding area of the interdigital electrode of the interdigital transducer, the film material is removed under the action of femtosecond laser.
Preferably, the apparatus further comprises a displacement table controller for controlling the two-dimensional motorized displacement table.
Preferably, in the femtosecond laser direct writing process, the center wavelength of the femtosecond laser is 900-1100 μm, the pulse width is 120-140 fs, the laser pulse repetition frequency is 1-3 kHz, the processing power is 60-100 mW, and the relative movement speed with the mask is 0.15-0.25 mm/s (or the movement speed of the two-dimensional electric displacement table is 0.15-0.25 mm/s) in the processing process. Further preferably, the femtosecond laser has a center wavelength of 1030nm, a pulse repetition frequency of 2kHz, a pulse width of 130fs, a processing power of 80mW, and a sample moving speed of 0.2mm/s during processing.
Preferably, the coating is carried out by adopting an evaporation process, and the thickness of the coating is 50-150 nm. More preferably, the metal thin film is deposited to a thickness of 100 nm.
Preferably, the piezoelectric substrate can be selected from various existing piezoelectric substrate materials, including but not limited to LiNbO3、LiTaO3PZT, PVDF, AlN, ZnO, etc.
Preferably, the material for plating is selected from gold, silver, copper, aluminum, molybdenum, and the like.
In practice, the interdigital transducer mask is fixed on the piezoelectric substrate by using an adhesive tape, for example, the interdigital transducer mask can be fixed on the piezoelectric substrate by using a polyimide adhesive tape. Placing the piezoelectric substrate fixed with the mask in a high vacuum evaporation coating system for evaporation coating, wherein the metal evaporation thickness is controlled by the coating time, and the evaporation speed is
(more preferably still)
) The thickness of the plating film is 50-100 nm. And after the metal evaporation is finished, tearing off the polyimide adhesive tape on the piezoelectric substrate and the mask, and removing the mask 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 30 μm or more.
Preferably, the width of the interdigital electrode is 30-300 micrometers, and further preferably, the width of the interdigital electrode is 30-150 micrometers.
A system for fabricating an acoustic wave device interdigital transducer based on a femtosecond laser processed mask, comprising:
the femtosecond laser direct writing device is used for processing the interdigital transducer mask;
and the film coating device is used for performing film coating processing on the piezoelectric substrate fixed with the interdigital transducer mask.
Preferably, the femtosecond laser direct writing device comprises:
a femtosecond laser providing femtosecond laser;
a shutter element for controlling the on-off of the laser beam;
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 beam;
the beam expanding element is used for expanding the collimated femtosecond laser;
the light path guiding and adjusting device is used for conducting climbing and falling guiding on the expanded femtosecond laser;
and the focusing element is used for focusing the guided light beam, and the laser focused by the focusing element is vertically irradiated to the surface of the film to be processed for the femtosecond laser direct writing processing.
Preferably, the shutter element is selected from an electric shutter or a mechanical shutter and is used for controlling the on-off of the laser beam;
preferably, the power adjusting element is selected from a neutral density attenuator plate or a combination of a half-wave plate and a polarizer plate for adjusting the laser power;
preferably, the light path collimating elements are two total reflection mirrors which are arranged in parallel, and the height and the left and the right of the light path are adjusted to be parallel to the optical platform;
preferably, the beam expanding element consists of two convex lenses which are arranged in a confocal manner, 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 50mm and 150mm, respectively.
Preferably, the optical path guiding and adjusting device consists of three total reflection mirrors placed at 45 degrees, and the two total reflection mirrors placed at 45 degrees are used for realizing longitudinal climbing and horizontal guiding of the height of the optical path; the light path direction is changed by 90 degrees by using another total reflection mirror placed at 45 degrees, and the light is vertically incident to 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. Further preferably, the focal length of the focusing lens is 20 mm.
Alternatively, the femtosecond laser direct writing device further comprises one or more of the following elements in combination:
one or more optical path directing elements;
an illumination source for illuminating the sample;
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 or the moving path of the three-dimensional positioning mechanism.
As a specific option, the illumination light source is a gooseneck lamp, and is used for polishing the metal film, so that the laser focusing and processing processes can be clearly observed by the CCD camera.
As a preferred scheme, the femtosecond laser direct writing device for preparing the interdigital transducer mask comprises: the femtosecond laser is sequentially provided with an electric shutter, a half-wave plate, a polaroid, two parallel holophotes (a first holophote and a second holophote), a beam expanding element (namely two convex lenses which are arranged in a confocal way), a light path guiding and adjusting device, a focusing lens and a three-dimensional positioning mechanism fixed with a metal film along the emergent laser direction of the femtosecond laser. And a one-dimensional manual displacement table in the three-dimensional positioning mechanism is used for adjusting the focusing of the laser on the metal film, and a displacement table controller controls a two-dimensional electric displacement table to move along an appointed path in sequence to complete laser ablation cutting so as to obtain the interdigital transducer mask. The laser focusing and direct writing processes are recorded in real time by a CCD camera, and the CCD camera is connected with a computer through a signal line; the two-dimensional electric displacement table is connected with a displacement table controller through a signal wire; the femtosecond laser is connected with a computer through a signal wire and is controlled by the computer.
During actual work, femtosecond laser irradiates a metal film vertically through a focusing light spot formed by a shutter element, power adjustment, light beam collimation, beam expansion, climbing, falling and focusing, the metal film is fixed on a one-dimensional manual displacement table arranged on a two-dimensional electric displacement table, and a displacement table controller controls the two-dimensional electric displacement table in a three-dimensional positioning mechanism to move along a specified path in sequence to directly write out an interdigital transducer mask.
During primary processing, the emergent laser energy of the femtosecond laser is adjusted for the first time by adjusting the pulse repetition frequency of the laser, so that the emergent laser energy is higher than the ablation threshold of the metal film. The laser power is further adjusted using a power adjustment element (half-wave plate in combination with polarizer). Of course, when the experimental conditions are stable, the adjustment step and the adjustment element can be omitted, and the final working parameters are directly adopted for automatic processing. That is, as an optimization, the power conditioning element may be omitted.
The invention provides a system and a method for preparing an acoustic wave device interdigital transducer based on a femtosecond laser processing mask, which have the advantages that:
(1) the invention directly writes the interdigital transducer pattern on the metal film by utilizing the focused femtosecond laser, and can realize the low-cost, quick, batch and high-precision preparation of the interdigital transducer mask.
(2) Compared with the traditional microelectronic photoetching process, the invention omits the processes of spin coating, drying, photoetching, developing, stripping and the like, has simple process and high flexibility, has the minimum processing wavelength of 120 mu m, and is particularly suitable for low-cost and rapid preparation of low-frequency acoustic microfluid devices. Meanwhile, the method avoids the use of a high-temperature drying process, is suitable for preparing the metallized patterns on the thermosensitive piezoelectric substrate, and avoids generating chemical waste liquid to pollute the environment.
(3) The mask has high flexibility, and can realize the preparation of flexible or curved metallized patterns.
Drawings
Fig. 1 is a schematic structural diagram of a femtosecond laser processing interdigital transducer mask device provided by the invention, wherein: the device comprises a femtosecond laser 1, an electric shutter 2, a half-wave plate 3, a polarizing plate 4, a holophote 5, a holophote 6, a convex lens 7, a convex lens 8, a holophote 9, a holophote 10, a holophote 11, a holophote 12, a focusing lens 12, a metal film 13, a one-dimensional manual displacement table 14, a two-dimensional electric displacement table 15, a displacement table controller 16, a gooseneck lamp 17, a CCD camera 18 and a computer 19.
FIG. 2 is a diagram of an interdigital transducer mask of different wavelengths processed in accordance with the present invention, wherein (a) the wavelength is 400 μm; (b) the wavelength is 300 μm; (c) the wavelength was 200. mu.m.
FIG. 3 is a flow chart of the present invention for fabricating an acoustic wave device interdigital transducer.
FIG. 4 is a pictorial view of an acoustic wave device of the present invention fabricated on different piezoelectric substrates, wherein (a) LiNbO3A substrate, a device wavelength of 400 μm; (b) LiNbO3A substrate, a device wavelength 300 μm; (c) PVDF substrate (500 μm thick), device wavelength 300 μm; (d) PVDF substrate (200 μm thick), device wavelength 300 μm.
FIG. 5 is a signal transmission and reflection spectrum of an acoustic wave device (wavelength 400 μm) of the present invention prepared on a different piezoelectric substrate, wherein (a) LiNbO3A substrate; (b) a PVDF substrate.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following detailed description and accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
The invention provides a system and a method for preparing an acoustic wave device interdigital transducer based on a femtosecond laser processing mask. In the processing mode, focused femtosecond laser is used for directly writing an interdigital transducer mask on a metal film, and then the mask is placed on a piezoelectric substrate to be subjected to metal evaporation to obtain an interdigital electrode structure; compared with the traditional microelectronic photoetching process, the preparation process has the advantages that the processes of spin coating, drying, photoetching, developing, stripping and the like are omitted, the preparation flow is greatly simplified, the prepared mask is low in cost and high in precision, and the mask can be reused.
The invention provides a system and a method for preparing an acoustic wave device interdigital transducer based on a femtosecond laser processing mask, wherein the structure of an optical path of a femtosecond laser direct writing device is shown as a figure 1, and the system comprises the following components: the device comprises a femtosecond laser 1, an electric shutter 2, a half-wave plate 3, a polaroid 4, a holophote 5, a holophote 6, a convex lens 7, a convex lens 8, a holophote 9, a holophote 10, a holophote 11, a focusing lens 12, a metal film 13, a one-dimensional manual displacement table 14, a two-dimensional electric displacement table 15, a displacement table controller 16, a gooseneck lamp 17, a CCD camera 18 and a computer 19.
The electric shutter 2 is mainly used for controlling the on-off of the laser beam, and the set position can be adjusted according to actual needs.
The optical half-wave plate 3 and the polaroid 4 are used in combination, are mainly used for adjusting laser power, and can be replaced by other power adjusting elements, such as a neutral density attenuator.
The total reflection mirror 5 and the total reflection mirror 6 are arranged in parallel, the pitching and the left and right of a laser light path are mainly adjusted, the light path collimation effect is achieved, the total reflection mirror 5 and the total reflection mirror 6 can be increased and decreased according to actual needs, and the arranged positions can be adjusted according to the actual needs before laser beam expansion.
The convex lens 7 and the convex lens 8 are placed in a confocal mode and mainly play a role in beam expanding.
The total reflection mirror 9, the total reflection mirror 10 and the total reflection mirror 11 mainly play guiding roles of lifting and dropping the optical path height, the total reflection mirror 9 changes the laser optical path direction by 90 degrees, horizontal propagation is changed into vertical climbing, the total reflection mirror 10 changes the laser optical path direction which vertically climbs by 90 degrees into horizontal propagation, the total reflection mirror 11 changes the laser optical path direction which horizontally propagates by 90 degrees, and the laser optical path direction vertically enters the center of the focusing lens 12.
The focusing lens 12 mainly plays a role in focusing light beams, and focused laser is vertically incident to the surface of the metal film 13 to be processed.
The metal film 13 is fixed on a three-dimensional positioning mechanism through an adhesive tape, the three-dimensional positioning mechanism is composed of a one-dimensional manual displacement table 14 and a two-dimensional electric displacement table 15, the one-dimensional manual displacement table 14 is installed on the two-dimensional electric displacement table 15, and the two-dimensional electric displacement table 15 is connected with a displacement table controller 16 through a signal line and is controlled by the displacement table controller 16 (certainly, under the conditions of software compatibility and function permission, the two-dimensional electric displacement table 15 can also be controlled by a computer 19 in a unified manner). The one-dimensional manual displacement table 14 is mainly used for adjusting the distance from the focusing lens 12 to the metal film 13 to be processed, so that the laser focus is positioned on the top surface of the metal film 13 to be processed, and the two-dimensional electric displacement table 15 is mainly used for realizing the horizontal movement of the metal film 13 to be processed in the processing process and forming a patterned cutting path.
The gooseneck lamp 17 is used for illuminating the metal film 13 so as to observe the focusing of the focusing lens 12 on the metal film 13 under the CCD camera 18 and monitor the whole processing process in real time.
The CCD camera 18 is connected with the computer 19 through a signal line, real-time imaging is carried out on a screen of the computer 19, and the femtosecond laser 1 is connected with the computer 19 through a signal line and controlled by the computer 19.
Before processing, firstly, related optical elements are sequentially placed into an optical platform according to the sequence of figure 1, and a femtosecond laser direct writing light path is built. In the processing process, a femtosecond laser 1 generates femtosecond laser, the femtosecond laser firstly passes through an electric shutter 2, then is adjusted to proper power through a half-wave plate 3 and a polaroid 4, then is incident on a holophote 5, after the laser path is collimated through the holophote 5 and the holophote 6, the reflected laser is vertically incident on a beam expanding system consisting of a convex lens 7 and a convex lens 8, after beam expanding, the femtosecond laser firstly vertically climbs through the holophote 9, then is horizontally transmitted through the holophote 10, finally is vertically downward incident on a focusing lens 12 through the holophote 11, the distance from a metal film 13 on a one-dimensional manual displacement table 14 to the focusing lens 12 is adjusted, so that the laser focus is positioned on the top surface of the metal film 13, and a displacement table controller 16 controls the metal film 13 on a two-dimensional electric displacement table 15 to sequentially move along a specified path to complete scanning and cutting, thereby obtaining the interdigital mask. And then, obtaining the interdigital electrode structure of the interdigital transducer by coating and removing the mask.
Example 1: and (3) femtosecond laser direct writing processing of the interdigital transducer mask.
In the embodiment of the invention, the adopted femtosecond laser is an ytterbium-doped femtosecond fiber laser (Tangerine HP) of Amplified company, the center wavelength of the femtosecond laser is 1030nm, the pulse width is 130fs, the highest repetition frequency is 35MHz, the single-pulse energy is 200 muJ, and the light field distribution is Gaussian distribution; the metal film is steel foil with thickness of 10 μm and size of 5cm × 5cm, and as an alternative, the steel foil can be replaced by aluminum foil or other metal film.
The specific processing steps of this example are as follows:
s1: completing the patterning moving path programming of the interdigital transducer mask on the computer 19, and writing a path program into the two-dimensional displacement table controller 16 through an SD memory card;
s2: fixing the steel foil 13 on a three-dimensional positioning mechanism consisting of a one-dimensional manual displacement table 14 and a two-dimensional electric displacement table 15 through an adhesive tape;
s3: the computer 19 controls the femtosecond laser 1 to emit pulse laser, each optical element is sequentially arranged in an optical platform according to the sequence of figure 1, the light path is debugged to enable the femtosecond laser to vertically enter the surface of the steel foil 13 after passing through the electric shutter 2, the half-wave plate 3, the polaroid 4, the holophote 5, the holophote 6, the convex lens 7, the convex lens 8, the holophote 9, the holophote 10, the holophote 11 and the focusing lens 12, the pulse repetition frequency of the femtosecond laser is set to be 2kHz, and the polaroid is rotated to enable the average power of the laser to be 80 mW.
S4: and turning on a gooseneck lamp 17 to illuminate the steel foil 13, and adjusting the longitudinal feeding of the one-dimensional manual displacement table 14 under a CCD camera 18 so that the focus of the femtosecond laser focused by the focusing lens 12 is positioned on the top surface of the steel foil 13.
S5: setting the feeding speed of the two-dimensional electric displacement table 15 to be 0.2mm/S, and sequentially loading the program in the step S1 by the displacement table controller 16, so that the two-dimensional electric displacement table 15 drives the steel foil 13 thereon to sequentially move along a specified path to complete scanning and cutting, and obtaining the interdigital transducer mask.
FIG. 2 is a diagram of an interdigital transducer mask with different wavelengths processed by the present invention, wherein (a) the wavelength is 400 μm, the interdigital electrode pairs are 15 pairs, and the acoustic aperture is 6000 μm; (b) the wavelength is 300 μm, the number of electrode pairs is 15 pairs, and the acoustic aperture is 5000 μm; (c) the wavelength is 200 μm, the number of electrode pairs is 5 pairs, and the acoustic aperture is 3000 μm.
Example 2: and manufacturing the acoustic wave device interdigital transducer based on the femtosecond laser processing mask.
In the embodiment of the invention, the metal coating equipment is a high vacuum evaporation coating system of Aifa vacuum technology (Suzhou) limited company, and the vacuum degree of a cavity is 5 multiplied by 10 in the coating process-4Pa, deposition rate of
The thickness of the metal evaporation is 100 nm. Alternatively, the metal deposition can also be carried out by a vacuum sputter coating device.
The specific processing steps of this example are as follows:
s1: fixing an interdigital transducer mask on a piezoelectric substrate through a polyimide adhesive tape;
s2: putting the piezoelectric substrate fixed with the interdigital transducer mask in a high vacuum evaporation coating system for evaporating a gold film, and setting the metal evaporation speed
The evaporation time is 33min, namely the thickness of the coating film is 100 nm.
S3: and after the evaporation is finished, removing the mask to obtain the interdigital electrode structure of the acoustic wave device interdigital transducer.
FIG. 3 is a flow chart of the manufacturing process of the acoustic wave device interdigital transducer, firstly, a mask is directly written by utilizing focused femtosecond laser, then the mask is fixed on a piezoelectric substrate, then the piezoelectric substrate and the mask are placed in a high vacuum evaporation coating system for metal evaporation, and finally the mask is removed to obtain the interdigital transducer structure.
FIG. 4 is a pictorial view of an acoustic wave device of the present invention fabricated on different piezoelectric substrates, wherein (a) LiNbO3The number of pairs of interdigital electrodes is 15, the wavelength is 400 mu m, and the acoustic aperture is 6000 mu m; (b) LiNbO3The number of pairs of interdigital electrodes on the substrate is 15, the wavelength is 300 mu m, and the acoustic aperture is 5000 mu m; (c) PVDF substrate (500 μm thickness), interdigital electrode pair number15 pairs, wavelength 300 μm, acoustic aperture 5000 μm; (d) PVDF substrate (200 μm thick), 15 pairs of interdigital electrode pairs, wavelength 300 μm, and acoustic aperture 5000 μm.
FIG. 5 shows signal transmission and reflection spectra of acoustic wave devices (400 μm wavelength) prepared on different piezoelectric substrates according to the present invention, wherein (a) LiNbO3A substrate, wherein the mode excited by the sound wave is a Rayleigh (R0) mode; (b) PVDF substrate, the mode excited by sound wave is zero order antisymmetric (A0) mode.
The foregoing is a more detailed description of the present invention that is presented in conjunction with specific embodiments, and the practice of the invention is not to be considered limited to those descriptions. For those skilled in the art to which the invention pertains, several simple deductions or substitutions can be made without departing from the spirit of the invention, and all shall be considered as belonging to the protection scope of the 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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