CN114499443A - Surface acoustic wave device and preparation method thereof - Google Patents

Surface acoustic wave device and preparation method thereof Download PDF

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Publication number
CN114499443A
CN114499443A CN202210109625.6A CN202210109625A CN114499443A CN 114499443 A CN114499443 A CN 114499443A CN 202210109625 A CN202210109625 A CN 202210109625A CN 114499443 A CN114499443 A CN 114499443A
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piezoelectric layer
layer
acoustic wave
surface acoustic
output
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刘宗亮
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Suzhou Dabo New Material Technology Co ltd
Jiangsu Third Generation Semiconductor Research Institute Co Ltd
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Suzhou Dabo New Material Technology Co ltd
Jiangsu Third Generation Semiconductor Research Institute Co Ltd
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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/02—Details
    • H03H9/02535—Details of surface acoustic wave devices
    • H03H9/02818—Means for compensation or elimination of undesirable effects
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H3/00—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators
    • H03H3/007—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks
    • H03H3/08—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks for the manufacture of resonators or networks using surface acoustic waves
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/02—Details
    • H03H9/125—Driving means, e.g. electrodes, coils
    • H03H9/145—Driving means, e.g. electrodes, coils for networks using surface acoustic waves
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/46—Filters
    • H03H9/64—Filters using surface acoustic waves

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  • Physics & Mathematics (AREA)
  • Acoustics & Sound (AREA)
  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Surface Acoustic Wave Elements And Circuit Networks Thereof (AREA)

Abstract

The invention discloses a surface acoustic wave device and a preparation method thereof. The surface acoustic wave device comprises a first piezoelectric layer, an input area and an output area are distributed on the surface of the first piezoelectric layer, an input interdigital transducer is arranged in the input area, an output interdigital transducer is arranged in the output area, the input interdigital transducer is matched with the output interdigital transducer through a transmission channel, the transmission channel comprises a second piezoelectric layer, the second piezoelectric layer is arranged in a groove structure, and the groove structure is arranged on the surface of the first piezoelectric layer and is distributed between the input area and the output area; the first and second piezoelectric layers are formed of a group III nitride. The invention takes the aluminum nitride as the main surface acoustic wave material, and simultaneously forms high-quality gallium nitride on the aluminum nitride as the transmission channel, thereby greatly reducing the transmission loss of the surface acoustic wave, effectively improving the transmission speed of the surface acoustic wave, and obtaining the high-frequency surface acoustic wave device with high electromechanical coupling coefficient.

Description

Surface acoustic wave device and preparation method thereof
Technical Field
The invention relates to an acoustic surface wave device and a preparation method thereof, and belongs to the field of semiconductor devices.
Background
In recent years, with the rapid development of mobile communication, radio communication frequency bands have become a limited and precious natural resource. In a third-generation digital system, the global roaming frequency range is 1.8-2.2 GHz, the frequency of a satellite positioning system (GPS) is 1.575GHz, and the application frequency range of low earth orbit new satellite communication (LEO) is 1.6 GHz-2.5 GHz, so that the application frequency of the current mobile communication system is increasingly high, and a high-frequency Surface Acoustic Wave (SAW) filter is urgently needed. In view of the development of the surface acoustic wave technology itself and the application requirements of surface acoustic wave devices, the surface acoustic wave technology needs to be developed towards high frequency and high performance.
To increase the center frequency of the surface acoustic wave device, there are two approaches: firstly, the surface acoustic wave propagation speed of the device material is higher, namely a high-sound-speed material is selected; and secondly, the interdigital finger of the device is thinner. The latter approach is limited by semiconductor processing technology and has limited ability to increase device frequency, whereas conventional SAW materials, such as quartz and lithium niobate LiNbO, are limited in their ability to increase device frequency3And zinc oxide ZnO and the like, the phase velocity of the surface acoustic wave is low and is generally lower than 4000m/s, so that the further improvement of the frequency of the surface acoustic wave device is severely restricted. Therefore, it is important to find a new material with high surface acoustic wave velocity and design a surface acoustic wave device based on the new material.
Disclosure of Invention
The invention mainly aims to provide a surface acoustic wave device based on a III-nitride material and a preparation method thereof, so as to overcome the defects of the prior art.
In order to achieve the purpose, the technical scheme adopted by the invention comprises the following steps:
one aspect of the invention provides a surface acoustic wave device, which comprises a first piezoelectric layer, wherein an input area and an output area are distributed on the surface of the first piezoelectric layer, an input interdigital transducer is arranged in the input area, an output interdigital transducer is arranged in the output area, the input interdigital transducer is matched with the output interdigital transducer through a transmission channel, the transmission channel comprises a second piezoelectric layer, the second piezoelectric layer is arranged in a groove structure, and the groove structure is arranged on the surface of the first piezoelectric layer and is distributed between the input area and the output area; the first and second piezoelectric layers are formed of a group III nitride.
Further, the material of the first piezoelectric layer comprises AlN, and the material of the second piezoelectric layer comprises GaN.
Further, the depth of the groove structure is smaller than the thickness of the first piezoelectric layer.
Further, a surface of the second piezoelectric layer is flush with a surface of the first piezoelectric layer.
In some embodiments, the first piezoelectric layer has a thickness of 5 to 20 μm.
In some embodiments, the groove structure is a plurality of groove structures, and the plurality of groove structures are arranged at intervals along a second direction, the input area and the output area are arranged at intervals along a first direction, and the second direction is perpendicular to the first direction.
In some embodiments, the depth of the groove structure is one-half to three-quarters of the thickness of the first piezoelectric layer.
Furthermore, the input interdigital transducer comprises a first finger inserting electrode structure, a first input pad and a second input pad, wherein the first input pad and the second input pad are matched with the first finger inserting electrode structure, the first finger inserting electrode structure comprises a first finger strip part and a second finger strip part which are arranged in a penetrating mode, the first finger strip part is electrically connected with the first input pad, and the second finger strip part is electrically connected with the second input pad.
Furthermore, the output interdigital transducer comprises a second finger inserting electrode structure, a first output bonding pad and a second output bonding pad, wherein the first output bonding pad and the second output bonding pad are matched with the second finger inserting electrode structure, the second finger inserting electrode structure comprises a third finger strip part and a fourth finger strip part which are arranged in a penetrating mode, the third finger strip part is electrically connected with the first output bonding pad, and the fourth finger strip part is electrically connected with the second output bonding pad.
Further, the surface acoustic wave device further comprises a first grounding bonding pad and a second grounding bonding pad which are arranged on the surface of the first piezoelectric layer, the first grounding bonding pad and the second grounding bonding pad are distributed on two sides of the transmission channel along a second direction, the input area and the output area are distributed on two sides of the transmission channel along the first direction, and the second direction is perpendicular to the first direction.
Furthermore, the surface acoustic wave device also comprises a substrate, and a nucleation layer, a third piezoelectric layer and a dielectric layer which are sequentially formed on the substrate, wherein the first piezoelectric layer is arranged on the dielectric layer.
Furthermore, the surface acoustic wave device further comprises a first sound absorption structure and a second sound absorption structure, wherein the first sound absorption structure, the input interdigital transducer, the output interdigital transducer and the second sound absorption structure are arranged on the surface of the first piezoelectric layer in sequence along the first direction.
In some embodiments, the material of the substrate comprises GaN.
In some embodiments, the substrate has a thickness of 0.1 to 1 mm.
In some embodiments, the substrate has a dislocation density of 102～104/cm2。
In some embodiments, the nucleation layer is a single layer structure or a multi-layer stack structure.
In some embodiments, the material of the nucleation layer comprises AlN.
In some embodiments, the nucleation layer has a thickness of 0.5 to 5 nm.
In some embodiments, the material of the third piezoelectric layer comprises AlN.
In some embodiments, the third piezoelectric layer has a thickness of 50 nm to 300 nm.
In some embodiments, the material of the dielectric layer includes Al2O3。
In some embodiments, the dielectric layer has a thickness of 3 to 20 nm.
Another aspect of the present invention provides a method for manufacturing the surface acoustic wave device, including:
covering a first mask structure on the surface of a first piezoelectric layer, wherein the first mask structure is provided with a patterned opening corresponding to the input interdigital transducer, the output interdigital transducer, a first grounding pad and a second grounding pad, and depositing a metal material in the patterned opening so as to form the input interdigital transducer, the output interdigital transducer, the first grounding pad and the second grounding pad on the surface of the first piezoelectric layer;
coating a second mask structure on the surface of the first piezoelectric layer, wherein the second mask structure is provided with a graphical opening corresponding to the transmission channel, and etching the first piezoelectric layer from the graphical opening so as to form a groove structure corresponding to the transmission channel in the first piezoelectric layer, and the depth of the groove structure is smaller than the thickness of the first piezoelectric layer;
and forming a second piezoelectric layer in the groove structure, and enabling the surface of the second piezoelectric layer to be flush with the surface of the first piezoelectric layer, thereby forming the transmission channel.
Further, the preparation method specifically comprises the following steps:
providing a substrate;
forming a nucleation layer on the substrate under a first temperature condition;
sequentially forming a third piezoelectric layer on the nucleation layer under a second temperature condition;
forming a dielectric layer on the third piezoelectric layer;
forming a first piezoelectric layer on the dielectric layer under a third temperature condition;
wherein the first temperature is higher than the second temperature and the third temperature is higher than the first temperature.
In some embodiments, the dielectric layer may be formed by sputtering or atomic layer deposition.
Further, the preparation method further comprises the following steps: and forming a first sound absorption structure and a second sound absorption structure on the surface of the first piezoelectric layer.
In some more specific embodiments, the preparation method specifically comprises the following steps:
step 1) providing a substrate;
step 2) depositing a nucleating layer on the substrate by adopting a Metal Organic Chemical Vapor Deposition (MOCVD) mode under a first temperature condition;
step 3) sequentially depositing a third piezoelectric layer on the nucleation layer under the condition of a second temperature, wherein the first temperature is higher than the second temperature;
step 4) forming a dielectric layer on the third piezoelectric layer in a sputtering or atomic layer deposition mode;
step 5) depositing a first piezoelectric layer on the dielectric layer under a third temperature condition, wherein the third temperature is higher than the first temperature;
step 6) covering a first mask structure on the surface of a first piezoelectric layer, wherein the first mask structure is provided with a graphical opening corresponding to the input interdigital transducer, the output interdigital transducer, a first grounding pad and a second grounding pad, and metal materials are deposited in the graphical opening, so that the input interdigital transducer, the output interdigital transducer, the first grounding pad and the second grounding pad are formed on the surface of the first piezoelectric layer;
and 7) coating a second mask structure on the surface of the first piezoelectric layer, wherein the second mask structure is provided with a graphical opening corresponding to the transmission channel, etching the first piezoelectric layer from the graphical opening so as to form a groove structure corresponding to the transmission channel in the first piezoelectric layer, the depth of the groove structure is smaller than the thickness of the first piezoelectric layer, then forming a second piezoelectric layer in the groove structure, and enabling the surface of the second piezoelectric layer to be flush with the surface of the first piezoelectric layer so as to form the transmission channel and finish the preparation of the surface acoustic wave device.
In some embodiments, the first mask structure in step 6) is preferably a patterned photoresist layer, so that the first mask structure can be successfully removed after the deposition of the metal material. Specifically, a photoresist layer may be formed on the surface of the first piezoelectric layer, and then the photoresist layer may be exposed and developed, so as to form corresponding openings in the photoresist layer.
In some embodiments, the second mask structure in step 7 may be a patterned photoresist layer, or a patterned metal baffle structure.
In some embodiments, the groove structure is formed by etching the first piezoelectric layer through physical attack and chemical reaction by using fluorine-based plasma in step 8).
In some embodiments, the preparation processes in step 6) and step 7) may be exchanged, that is, the transmission channel may be prepared first, and then the input interdigital transducer, the output interdigital transducer, and the first ground pad and the second ground pad may be prepared.
Compared with the prior art, the invention has the advantages that:
1) the provided surface acoustic wave device takes the aluminum nitride as a main surface acoustic wave material, utilizes the good piezoelectric property, the high-quality crystal crystallization property and the lower crystal defect of the aluminum nitride, reduces the transmission loss of the surface acoustic wave, and realizes the high-frequency surface acoustic wave device with higher electromechanical coupling coefficient.
2) According to the surface acoustic wave device, the plurality of discontinuous gallium nitride transmission channels are formed on the aluminum nitride, the problem that a large-area high-quality gallium nitride layer is difficult to prepare is solved, the propagation speed of the surface acoustic wave is effectively improved, meanwhile, the lattice coefficients of the gallium nitride and the aluminum nitride are matched, the growth technology is similar, the quality of a formed gallium nitride crystal is high, the propagation speed of the surface acoustic wave is high, and the propagation loss is small.
3) The surface acoustic wave device is provided with the dielectric layer and the thin aluminum nitride layer below the surface aluminum nitride layer, so that acoustic waves can be prevented from being transmitted to the substrate, and loss is further reduced.
4) The provided surface acoustic wave device is compatible with an integrated circuit process, is convenient to form, can save preparation procedures and reduces cost.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments described in the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
Fig. 1 is a top view of a saw device according to an exemplary embodiment of the present invention;
fig. 2 is a cross-sectional view of the surface acoustic wave device in fig. 1 taken along the direction a-a'.
Detailed Description
In view of the defects of the prior art, the inventor of the present invention has made a long-term study and a great deal of practice to provide a technical scheme of the present invention, which mainly aims at the problem that the surface acoustic wave velocity of a surface acoustic wave device prepared based on a traditional surface acoustic wave material is low and is difficult to meet the requirement of high-frequency application, and provides a surface acoustic wave device based on gallium nitride and aluminum nitride and a preparation method thereof, and effectively improves the frequency performance of the surface acoustic wave device by improving the structure and the preparation method of the device.
The surface acoustic wave propagation speed of gallium nitride can reach more than 7000m/s, which is much higher than that of the traditional material (for example, the surface acoustic wave propagation speed of the material using more lithium niobate is only 3500-3700 m/s). For gallium nitride materials, because the bonds of gallium nitride are ionized and the continuous interplanar spacing of gallium atoms and nitrogen atoms is not uniform, when atoms in one plane are squeezed, the atoms in the upper and lower planes move different distances, creating a net charge, electric field, and voltage, and thus gallium nitride has certain piezoelectric properties. The aluminum nitride also has good piezoelectric property and high surface acoustic wave propagation speed, and can be used as a preferred material for manufacturing high-frequency surface acoustic wave devices.
The technical solution, the implementation process and the principle will be further explained with reference to the drawings and the specific embodiments. It should be noted that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention. In addition, the manufacturing processes, such as a mask process, a metal organic chemical vapor deposition process, an atomic layer deposition process, and a plasma etching process, which are related in the embodiments of the present invention are well known in the art, and are not specifically described in the following embodiments.
Example 1: referring to fig. 1-2, a surface acoustic wave device according to an embodiment of the present invention includes a GaN substrate 10, an AlN nucleation layer 20, an AlN single crystal layer 30 (i.e., the third piezoelectric layer), and Al sequentially disposed from bottom to top2O3The surface acoustic wave device comprises a dielectric layer 40 and an AlN single crystal layer 50 (namely, the first piezoelectric layer), wherein an input area and an output area are distributed on the surface of the AlN single crystal layer 50 at intervals along a first direction, an input interdigital transducer 60 is arranged in the input area, an output interdigital transducer 70 is arranged in the output area, a plurality of discontinuous groove structures are arranged on the surface of the AlN single crystal layer 50 between the input area and the output area, the groove structures are distributed at intervals along a second direction vertical to the first direction, a GaN single crystal layer 80 (namely, the second piezoelectric layer) is formed in the groove structures, the GaN single crystal layer 80 forms a transmission channel of the surface acoustic wave device, and the input interdigital transducer 60 is matched with the output interdigital transducer 70 through the transmission channel. The surface of the AlN single crystal layer 50 is further provided with a first ground pad 901 and a second ground pad 902, and the first ground pad 901 and the second ground pad 902 are distributed on two sides of the transmission channel along a second direction.
Wherein the depth of the groove structure is less than the thickness of the first piezoelectric layer, namely, the sidewall and the bottom wall of the groove structure are both AlN single crystal layers 50, and the crystal quality of the GaN single crystal layer 80 grown by using the AlN single crystal layer 50 as a growth template is higher because the lattice matching coefficient of AlN and GaN is higher. If the depth of the recess structure is the same as the thickness of the first piezoelectric layer, Al is used2O3The dielectric layer 40 is a growth template for growing a GaN single crystal layer 80, Al2O3Lattice mismatch with GaN is not favorable for forming the GaN single crystal layer 80 of high quality.
In some preferred embodiments, the depth of the groove structure is one-half to three-quarters of the thickness of the AlN single crystal layer 50.
In some preferred embodiments, the surface of the GaN single crystal layer 80 is flush with the surface of the AlN single crystal layer 50.
Further, the input interdigital transducer 60 comprises a first finger inserting electrode structure, and a first input pad 601 and a second input pad 602 which are matched with the first finger inserting electrode structure, wherein the first finger inserting electrode structure comprises a first finger portion 603 and a second finger portion 604 which are arranged in an inserting mode, the first finger portion 603 is electrically connected with the first input pad 601, and the second finger portion 604 is electrically connected with the second input pad 602.
Further, the output interdigital transducer 70 includes a second interdigital electrode structure, and a first output pad 701 and a second output pad 702 which are matched with the second interdigital electrode structure, the second interdigital electrode structure includes a third finger portion 703 and a fourth finger portion 704 which are alternately arranged, the third finger portion 703 is electrically connected with the first output pad 701, and the fourth finger portion 704 is electrically connected with the second output pad 702.
Further, the surface acoustic wave device further includes a first sound absorption structure and a second sound absorption structure (not shown in the figure), and the first sound absorption structure and the second sound absorption structure are respectively located at the outer sides of the input interdigital transducer 60 and the output interdigital transducer 70, so as to prevent the interference of external sound wave transmission or vibration.
Further, an embodiment of the present invention further provides a method for manufacturing the surface acoustic wave device, which specifically includes the following steps:
step 1) provides a GaN substrate 10.
In some more specific embodiments, the GaN substrate 10 may be a homoepitaxial gallium nitride substrate or a heteroepitaxial gallium nitride substrate with a dislocation density of 102～104/cm2Controlling the lower dislocation density of gallium nitride can further improve the crystal quality of the subsequently grown aluminum nitride, reduce defects, and reduce stress caused by lattice mismatch.
In some more specific embodiments, the GaN substrate 10 may have dimensions of 2 inches, 4 inches, 6 inches, or more, and a thickness of 0.1-1 mm.
Step 2) forms an AlN nucleation layer 20 on the GaN substrate 10. The AlN nucleation layer 20 serves to reduce dislocations caused by lattice mismatch between the GaN substrate 10 and a nitride single crystal grown in a subsequent step, further reduce deformation caused by a difference between coefficients of thermal expansion, and suppress the generation of cracks, so that a nitride single crystal layer of better quality can be obtained on the AlN nucleation layer 20.
In some more specific embodiments, the AlN nucleation layer 20 may be deposited on the GaN substrate 10 using Metal Organic Chemical Vapor Deposition (MOCVD). Specifically, the GaN substrate 10 is placed in a growth chamber of an MOCVD tool, and then a metal source gas (e.g., triethylaluminum metal source gas) and a nitrogen source gas are simultaneously introduced into the growth chamber, thereby forming the AlN nucleation layer 20 on the GaN substrate 10. Meanwhile, the metal source gas and the nitrogen source gas are introduced to ensure the stable growth of the AlN.
In some more specific embodiments, the growth temperature of AlN nucleation layer 20 is 1200 to 1240 ℃.
In some more specific embodiments, the AlN nucleation layer 20 may be a single layer structure or a stacked structure having multiple layers.
In some more specific embodiments, the AlN nucleation layer 20 has a thickness of 0.5 to 5 nm.
3) The metal source gas and the nitrogen source gas are continuously introduced to form the AlN single crystal layer 30 on the AlN nucleation layer 20.
In some more specific embodiments, the growth temperature of the AlN single-crystal layer 30 is 1100 to 1150 ℃.
In some more specific embodiments, the AlN single-crystal layer 30 has a thickness of 50 to 300 nm.
Step 4) formation of Al on the surface of the AlN single-crystal layer 302O3A dielectric layer 40.
Al2O3The crystal lattice matching degree with AlN is high, the formation is convenient, and the crystal quality of AlN formed subsequently above the crystal lattice matching degree is not influenced. By Al2O3The double-layer structure formed by the dielectric layer 40 and the AlN single crystal layer 30 can limit the surface acoustic waves on the surface of the device well, increase the electromechanical coupling performance of the device and realize a wider frequency band. Formation of Al2O3Manner of the dielectric layer 40The Al layer can be formed by sputtering or atomic layer deposition, preferably by atomic layer deposition, although the deposition rate is slow, the Al layer is formed2O3The quality of (2) is better.
In one embodiment, Al2O3The thickness of the dielectric layer 40 is 3-20 nm. Al (Al)2O3The thickness of the dielectric layer 40 cannot be very thin, too thin Al2O3The dielectric layer 40 does not provide sufficient acoustic confinement, and at the same time, Al does not provide sufficient acoustic confinement2O3The thickness of the dielectric layer 40 is not too thick, and although the thickness can better limit the acoustic wave, the thickness can affect the crystal crystallization performance of the aluminum nitride above, thereby affecting the piezoelectric performance of the aluminum nitride.
Step 5) continuing to use triethyl aluminum and nitrogen as a metal source and a nitrogen source respectively at Al2O3An AlN single crystal layer 50 is formed on the surface of the dielectric layer 40.
In one embodiment, the growth temperature of the AlN single-crystal layer 50 is 1250 to 1300 ℃. The growth temperature of the AlN single crystal layer 50 is higher than that of the AlN single crystal layer 30, and the crystal quality of AlN can be improved.
In one embodiment, the AlN single crystal layer 50 has a thickness of 5 to 20 μm.
Step 6) forming the input interdigital transducer 60, the output interdigital transducer 70, and the first ground pad 901, the second ground pad 902 on the surface of the AlN single crystal layer 50.
In one embodiment, a photoresist layer (not shown) may be coated on the surface of the AlN single crystal layer 50, the photoresist layer is exposed and developed according to the shape of the input interdigital transducer 60, the output interdigital transducer 70 and the first and second ground pads 901, 902, so as to form patterned openings corresponding to the input interdigital transducer 60, the output interdigital transducer 70 and the first and second ground pads 901, 902 in the photoresist layer, and then a metal material is deposited in the openings to form the input interdigital transducer 60, the output interdigital transducer 70 and the first and second ground pads 901, 902, and then the photoresist layer is removed.
By forming the corresponding patterned openings and then depositing the metal material to form the input interdigital transducer 60, the output interdigital transducer 70, the first grounding pad 901 and the second grounding pad 902, compared with a method of forming a whole metal layer and etching the whole metal layer according to the corresponding pattern, the etching step can be omitted, and the input interdigital transducer 60, the output interdigital transducer 70, the first grounding pad 901 and the second grounding pad 902 are formed synchronously, so that the process steps can be reduced.
In addition, since the etching metal usually adopts a wet etching process, residues of the wet etching solution are easily remained on the surface of the AlN single crystal layer 50 during the wet etching process, and these residues may corrode the device, affecting the service life and performance of the device.
In one embodiment, the metal material may be any one or more of Al, Cu, Mo, Pt, Ti, Au, and the like.
Step 7) forming a transmission channel on the surface of the AlN single-crystal layer 50.
In one embodiment, a mask structure having a patterned opening corresponding to a predefined transmission channel may be coated on the surface of the AlN single crystal layer 50, and then the AlN single crystal layer 50 may be etched along the opening using the mask structure as a mask, thereby forming a plurality of discontinuous groove structures corresponding to the transmission channel in the AlN single crystal layer 50, and making the depth of the groove structures to be one half to three quarters of the thickness of the AlN single crystal layer 50, and then forming the AlN single crystal layer 80 in the groove structures, thereby forming the transmission channel.
In one embodiment, the AlN single crystal layer 50 at the opening may be etched using physical bombardment, a chemical reaction, using a plasma of a fluorine-based mixed gas.
In one embodiment, the fluorine-based mixed gas is composed of SF6、CHF3、CF4Is mixed with inert gas such as argon or helium, wherein the molar ratio of fluorine-containing gas to the mixed gas is 60-80%, and the inert gas is used as carrier gas for etchingThe direct current bias voltage in the chamber is 800-1000V, and the pressure is 2-5 Pa.
Example 2: the structure of the surface acoustic wave device provided in this embodiment is the same as the device structure shown in fig. 1-2 in embodiment 1, and the manufacturing method provided is also similar to that in embodiment 1, except that:
and step 6) and step 7), namely, firstly forming a transmission channel on the surface of the AlN single crystal layer 50, and then forming the input interdigital transducer 60, the output interdigital transducer 70, the first grounding pad 901 and the second grounding pad 902 on the surface of the AlN single crystal layer 50.
According to the surface acoustic wave device and the preparation method thereof provided by the embodiments of the invention, on one hand, aluminum nitride is selected as a main surface acoustic wave material, and the transmission loss of surface acoustic waves is reduced by utilizing the good piezoelectric property, the high-quality crystal crystallization property and the lower crystal defect of the aluminum nitride, so that a high-frequency surface acoustic wave device with a higher electromechanical coupling coefficient is realized; on the other hand, a plurality of discontinuous gallium nitride transmission channels are formed in the aluminum nitride, so that the problem that a large-area high-quality gallium nitride layer is difficult to prepare is solved, the propagation speed of the surface acoustic wave is effectively improved, meanwhile, the lattice coefficients of the gallium nitride and the aluminum nitride are matched, the growth technology is similar, the quality of the formed gallium nitride crystal is high, the propagation speed of the surface acoustic wave is high, and the propagation loss is small.
In addition, the surface acoustic wave device is provided with the dielectric layer and the thin aluminum nitride layer below the surface aluminum nitride layer, so that the sound wave can be well limited, the sound wave can be prevented from being transmitted to the substrate, and the loss is further reduced.
Moreover, the surface acoustic wave device is compatible with an integrated circuit process, is convenient to form, can save preparation procedures and reduce cost.
It should be understood that the technical solution of the present invention is not limited to the above-mentioned specific embodiments, and all technical modifications made according to the technical solution of the present invention fall within the protection scope of the present invention without departing from the spirit of the present invention and the protection scope of the claims.

Claims (10)

1. A surface acoustic wave device is characterized by comprising a first piezoelectric layer, wherein an input area and an output area are distributed on the surface of the first piezoelectric layer, an input interdigital transducer is arranged in the input area, an output interdigital transducer is arranged in the output area, the input interdigital transducer is matched with the output interdigital transducer through a transmission channel, the transmission channel comprises a second piezoelectric layer, the second piezoelectric layer is arranged in a groove structure, and the groove structure is arranged on the surface of the first piezoelectric layer and distributed between the input area and the output area; the first and second piezoelectric layers are formed of a group III nitride.
2. A surface acoustic wave device as set forth in claim 1, wherein: the material of the first piezoelectric layer comprises AlN, and the material of the second piezoelectric layer comprises GaN.
3. A surface acoustic wave device as set forth in claim 1, wherein: the depth of the groove structure is less than the thickness of the first piezoelectric layer; and/or a surface of the second piezoelectric layer is flush with a surface of the first piezoelectric layer; and/or the thickness of the first piezoelectric layer is 5-20 μm; and/or the groove structures are multiple and are arranged at intervals along a second direction, the input area and the output area are arranged at intervals along a first direction, and the second direction is vertical to the first direction.
4. A surface acoustic wave device according to claim 1 or 3, characterized in that: the depth of the groove structure is one half to three quarters of the thickness of the first piezoelectric layer.
5. A surface acoustic wave device as set forth in claim 1, wherein: the input interdigital transducer comprises a first finger inserting electrode structure, a first input pad and a second input pad, wherein the first input pad and the second input pad are matched with the first finger inserting electrode structure;
and/or the output interdigital transducer comprises a second interdigital electrode structure, a first output bonding pad and a second output bonding pad, wherein the first output bonding pad and the second output bonding pad are matched with the second interdigital electrode structure, the second interdigital electrode structure comprises a third finger strip part and a fourth finger strip part which are arranged in a penetrating mode, the third finger strip part is electrically connected with the first output bonding pad, and the fourth finger strip part is electrically connected with the second output bonding pad.
6. A surface acoustic wave device as set forth in claim 1, wherein:
the surface acoustic wave device further comprises a first grounding bonding pad and a second grounding bonding pad which are arranged on the surface of the first piezoelectric layer, the first grounding bonding pad and the second grounding bonding pad are distributed on two sides of the transmission channel along a second direction, the input area and the output area are distributed on two sides of the transmission channel along the first direction, and the second direction is perpendicular to the first direction;
and/or the surface acoustic wave device further comprises a substrate, and a nucleation layer, a third piezoelectric layer and a dielectric layer which are sequentially formed on the substrate, wherein the first piezoelectric layer is arranged on the dielectric layer;
and/or, the surface acoustic wave device further comprises a first sound absorption structure and a second sound absorption structure, wherein the first sound absorption structure, the input interdigital transducer, the output interdigital transducer and the second sound absorption structure are arranged on the surface of the first piezoelectric layer in sequence along the first direction.
7. A surface acoustic wave device as set forth in claim 6, wherein:
the substrate is made of GaN; and/or the thickness of the substrate is 0.1-1 mm; and/or the substrate has a dislocation density of 102～104/cm2；
And/or the nucleating layer is of a single-layer structure or a multi-layer stacked structure; and/or the material of the nucleation layer comprises AlN; and/or the thickness of the nucleating layer is 0.5-5 nm;
and/or the material of the third piezoelectric layer comprises AlN; and/or the thickness of the third piezoelectric layer is 50-300 nm;
and/or the material of the dielectric layer comprises Al2O3(ii) a And/or the thickness of the dielectric layer is 3-20 nm.
8. A method of manufacturing a surface acoustic wave device according to any one of claims 1 to 7, comprising:
forming a first piezoelectric layer, covering a first mask structure on the surface of the first piezoelectric layer, wherein the first mask structure is provided with a patterned opening corresponding to the input interdigital transducer, the output interdigital transducer, a first grounding pad and a second grounding pad, and depositing a metal material in the patterned opening, so that the input interdigital transducer, the output interdigital transducer, the first grounding pad and the second grounding pad are formed on the surface of the first piezoelectric layer;
coating a second mask structure on the surface of the first piezoelectric layer, wherein the second mask structure is provided with a graphical opening corresponding to the transmission channel, and etching the first piezoelectric layer from the graphical opening so as to form a groove structure corresponding to the transmission channel in the first piezoelectric layer, and the depth of the groove structure is smaller than the thickness of the first piezoelectric layer;
and forming a second piezoelectric layer in the groove structure, and enabling the surface of the second piezoelectric layer to be flush with the surface of the first piezoelectric layer so as to form the transmission channel.
9. The method according to claim 8, wherein the forming the first piezoelectric layer specifically includes:
providing a substrate;
forming a nucleation layer on the substrate under a first temperature condition;
sequentially forming a third piezoelectric layer on the nucleation layer under a second temperature condition;
forming a dielectric layer on the third piezoelectric layer;
forming a first piezoelectric layer on the dielectric layer under a third temperature condition;
wherein the first temperature is higher than the second temperature and the third temperature is higher than the first temperature.
10. The method of manufacturing according to claim 8, further comprising: and forming a first sound absorption structure and a second sound absorption structure on the surface of the first piezoelectric layer.
CN202210109625.6A 2022-01-29 2022-01-29 Surface acoustic wave device and preparation method thereof Withdrawn CN114499443A (en)

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Application publication date: 20220513