CN114497348A - Piezoelectric material, method for manufacturing same, surface acoustic wave resonator, and electronic device - Google Patents

Abstract

The invention discloses a piezoelectric material, a manufacturing method thereof, a surface acoustic wave resonator and an electronic device. According to the piezoelectric material provided by the invention, the aluminum nitride film is used as the piezoelectric layer for generating and transmitting surface acoustic waves on the surface of the piezoelectric layer, and the aluminum nitride film has the advantages of high sound velocity, good thermal stability, high heat conductivity coefficient and the like, so that the frequency of a device is high, and the temperature drift is small; in addition, the silicon substrate is used as the substrate, the aluminum nitride film is made to serve as the piezoelectric material, large-scale production of devices is facilitated, integration with a CMOS (complementary metal oxide semiconductor) process can be achieved, manufacturing cost is reduced, and integration level and performance of the devices are improved.

Description

Piezoelectric material, method for manufacturing same, surface acoustic wave resonator, and electronic device

Technical Field

The invention relates to the field of wireless communication technology and sensors, in particular to a piezoelectric material and a manufacturing method thereof, a surface acoustic wave resonator and an electronic device.

Background

The surface acoustic wave resonator can be used for manufacturing surface acoustic wave filters, pressure sensors, gas detectors, radiation detectors, energy collectors, energy converters, microfluidic devices and the like, wherein the surface acoustic wave filters are widely applied to the field of mobile communication. The piezoelectric material adopted in the existing surface acoustic wave filter is mainly a single crystal wafer of lithium tantalate or lithium niobate, but the temperature drift is large, the piezoelectric material is incompatible with a CMOS (Complementary Metal Oxide Semiconductor) process, and the piezoelectric material is difficult to integrate with a silicon-based device and has high cost.

Disclosure of Invention

The invention mainly aims to provide a piezoelectric material and a manufacturing method thereof, a surface acoustic wave resonator and an electronic device, and aims to solve the problems of large temperature drift, low frequency, incompatibility with a CMOS (complementary metal oxide semiconductor) process, difficulty in integration with a silicon-based device and high cost in the existing surface acoustic wave filter.

In order to achieve the above object, the present invention provides a piezoelectric material for a surface acoustic wave resonator, the piezoelectric material including a silicon substrate and an aluminum nitride film stacked from bottom to top.

Optionally, the aluminum nitride film is of a single crystal structure; and/or

The aluminum nitride film is a doped aluminum nitride film, and the doped aluminum nitride film is doped with at least one of scandium, yttrium, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, chromium, zirconium, manganese and magnesium.

Optionally, an intermediate layer is disposed between the silicon-based substrate and the aluminum nitride thin film, the intermediate layer includes a seed layer and/or a buffer layer and/or a transition layer stacked from bottom to top, the seed layer includes a nitride material, the buffer layer includes an aluminum nitride material, the transition layer includes an aluminum nitride material, and the concentration of aluminum components in the transition layer gradually increases along a direction from bottom to top.

Optionally, a stress absorption layer is disposed between the silicon-based substrate and the intermediate layer, and the material of the stress absorption layer includes a silicon nitride compound or a non-silicon nitride compound.

Optionally, the transition layer is a superlattice structure.

Optionally, an insertion layer is arranged between the transition layer and the silicon-based substrate; and/or the presence of a gas in the gas,

an insertion layer is arranged between the transition layer and the aluminum nitride thin film.

The invention also provides a manufacturing method of the piezoelectric material, which comprises the following steps:

forming a stress absorption layer on a silicon-based substrate;

forming a seed layer on the stress absorption layer;

forming a buffer layer on the seed layer;

forming a transition layer on the buffer layer;

growing an aluminum nitride film on the transition layer;

and doping the aluminum nitride film by an ion implantation method, and annealing after doping to obtain the doped aluminum nitride film.

The invention also provides a surface acoustic wave resonator which comprises the piezoelectric material, wherein the piezoelectric material comprises a silicon substrate and an aluminum nitride film which are stacked from bottom to top.

The invention also provides an electronic device comprising the surface acoustic wave resonator, wherein the surface acoustic wave resonator comprises the piezoelectric material, and the piezoelectric material comprises a silicon-based substrate and an aluminum nitride film which are stacked from bottom to top.

Optionally, the electronic device is a surface acoustic wave filter, a sensor, or a microfluidic device.

In the technical scheme of the invention, the aluminum nitride film is used as the piezoelectric layer for generating and transmitting surface acoustic waves on the surface of the piezoelectric layer, and has the advantages of high sound velocity, good thermal stability, high heat conductivity coefficient and the like, so that the frequency of a device is high, and the temperature drift is small; in addition, the silicon substrate is used as the substrate, the aluminum nitride film is made to serve as the piezoelectric material, large-scale production of devices is facilitated, integration with a CMOS (complementary metal oxide semiconductor) process can be achieved, manufacturing cost is reduced, and integration level and performance of the devices are improved.

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 of the present invention, and for those skilled in the art, other related drawings can be obtained according to the drawings without creative efforts.

Fig. 1 is a schematic view of a first embodiment of a piezoelectric material according to the present invention;

fig. 2 is a schematic view of a second embodiment of the piezoelectric material proposed by the present invention;

fig. 3 is a schematic view of a third embodiment of a piezoelectric material according to the present invention;

fig. 4 is a schematic view of a fourth embodiment of the piezoelectric material proposed by the present invention;

fig. 5 is a schematic view of a fifth embodiment of the piezoelectric material proposed by the present invention;

fig. 6 is a schematic view of a sixth embodiment of a piezoelectric material according to the present invention;

fig. 7 is a schematic view of a seventh embodiment of a piezoelectric material proposed by the present invention;

fig. 8 is a schematic view of an eighth embodiment of a piezoelectric material proposed by the present invention;

fig. 9 is a schematic view of a ninth embodiment of the piezoelectric material proposed by the present invention;

fig. 10 is a schematic view of a tenth embodiment of a piezoelectric material proposed by the present invention;

fig. 11 is a schematic view of an eleventh embodiment of a piezoelectric material proposed by the present invention;

fig. 12 is a schematic view of a twelfth embodiment of a piezoelectric material according to the present invention;

fig. 13 is a schematic view of a thirteenth embodiment of a piezoelectric material proposed by the present invention;

fig. 14 is a schematic flow chart illustrating a method for manufacturing a piezoelectric material according to an embodiment of the present invention;

fig. 15 is a schematic structural view of a surface acoustic wave resonator according to the present invention;

fig. 16 is a schematic diagram of a process for manufacturing a surface acoustic wave resonator according to the present invention.

The reference numbers illustrate:

the implementation, functional features and advantages of the objects of the present invention will be further explained with reference to the accompanying drawings.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. It is to be understood that the described embodiments are merely a few embodiments of the invention, and not all embodiments.

It should be noted that those whose specific conditions are not specified in the examples were performed according to the conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially. In addition, the meaning of "and/or" appearing throughout includes three juxtapositions, exemplified by "A and/or B" including either A or B or both A and B. In addition, technical solutions between various embodiments may be combined with each other, but must be realized by a person skilled in the art, and when the technical solutions are contradictory or cannot be realized, such a combination should not be considered to exist, and is not within the protection scope of the present invention. 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.

The surface acoustic wave resonator can be used for manufacturing surface acoustic wave filters, pressure sensors, gas detectors, radiation detectors, energy collectors, energy converters, microfluidic devices and the like, wherein the surface acoustic wave filters are widely applied to the field of mobile communication. The piezoelectric material adopted in the existing surface acoustic wave filter is mainly a single crystal wafer of lithium tantalate or lithium niobate, but the piezoelectric material has low frequency, large temperature drift, incompatibility with CMOS process, difficult integration with silicon-based devices and high cost.

In view of the above, the present invention provides a piezoelectric material, and fig. 1 to 13 are embodiments of the piezoelectric material provided in the present invention.

Referring to fig. 1, the piezoelectric material is used for a surface acoustic wave resonator, and includes a silicon substrate 1 and an aluminum nitride film 2 stacked from bottom to top.

In the technical scheme of the invention, the aluminum nitride film 2 is used as a piezoelectric layer for generating and transmitting surface acoustic waves on the surface of the piezoelectric layer, and the aluminum nitride film 2 has the advantages of high surface acoustic velocity, good thermal stability, high heat conductivity coefficient and the like, so that the frequency of a device is high, and the temperature drift is small; in addition, the silicon substrate is used as the substrate, and the aluminum nitride film 2 is made to be used as the piezoelectric material, so that the large-scale production of the device is facilitated, the integration with the CMOS process can be realized, the manufacturing cost is reduced, and the integration level and the performance of the device are improved.

Further, the aluminum nitride film 2 is a doped aluminum nitride film doped with at least one of scandium, yttrium, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium, and by doping, it is helpful to increase the piezoelectric coefficient of the aluminum nitride film 2, thereby increasing the electromechanical coupling coefficient of the surface acoustic wave resonator having the silicon-based substrate 1 and the aluminum nitride film 2 as piezoelectric materials. Preferably, one of scandium, yttrium, lanthanum, cerium, erbium or the like is doped, in the case of scandium, after doping, scandium atoms replace part of aluminum atoms to form scandium nitride, scandium nitride is nonpolar III-V nitride having a rock salt structure, aluminum nitride is polar III-V nitride having a wurtzite structure, and after scandium doping is performed on aluminum nitride, a transition region between the wurtzite structure and the rock salt structure is formed, so that the piezoelectric coefficient of the aluminum nitride film 2 is improved, and appropriate scandium doping can increase the piezoelectric coefficient of the aluminum nitride film 2 by 100-.

The aluminum nitride film 2 is of a single crystal structure, and compared with the polycrystalline aluminum nitride film 2, the single crystal aluminum nitride film 2 has various advantages, better crystallinity (smaller half height value-FWHM), higher sound wave transmission speed, higher piezoelectric constant and piezoelectric coupling coefficient. Therefore, the performance of various sensors based on the aluminum nitride film 2 is further improved, and meanwhile, the radio frequency filter based on the aluminum nitride film 2 can meet the requirements of 5G communication on higher bandwidth and better performance.

It should be noted that, for the silicon-based substrate 1, the size may be 4-12 inches, such as 4 inches, 6 inches, 8 inches, 10 inches, 12 inches, etc. Preferably, 6-12 inches is adopted, and the silicon wafer in the size range is used as the substrate, so that the mass production capacity of device manufacturing is improved, and the cost is reduced. In some embodiments, the substrate may also be aluminum nitride, silicon carbide, quartz, glass, etc., and the substrate may have dimensions of generally 2-6 inches, such as 2 inches, 4 inches, 6 inches, etc.

The aluminum nitride material and the substrate material have different lattice constants and thermal expansion coefficients. The difference in lattice constant causes lattice mismatch between the substrate and the aluminum nitride, resulting in dislocation defects; lattice mismatch can also create stress in the material and cause wafer warpage and cracking. In addition, the growth of aluminum nitride material is usually carried out at a relatively high temperature (1000-; the dislocation defects are also caused by the stress generated by the temperature change when the stress caused by the temperature change exceeds the critical stress of the material.

In the embodiment of the present invention, the substrate is a silicon-based substrate 1, and the silicon material and the aluminum nitride material have lattice constants of 5.43A and 3.11A, respectively, and have a lattice mismatch of 53%. The thermal expansion coefficients of the silicon material and the aluminum nitride material are respectively 2.6x10^-6K^-1And 4.5x10^-6K^-1Mismatch reaches 54%.

In order to reduce or eliminate dislocation, warping and cracking caused by lattice mismatch and stress, an intermediate layer 3 is arranged between the silicon substrate 1 and the aluminum nitride thin film 2, the intermediate layer 3 comprises a seed layer 31 and/or a buffer layer 32 and/or a transition layer 33 which are stacked from bottom to top, the seed layer 31 comprises a nitride material, the buffer layer 32 comprises an aluminum nitride material, the transition layer 33 comprises an aluminum-nitrogen compound material, and the concentration of aluminum components in the transition layer 33 is gradually increased along the direction from bottom to top. The seed layer 31 is typically a thin film of nitride, such as aluminum nitride, gallium nitride, having a thickness of 1-10nm, to further reduce or eliminate dislocation defects, wafer warpage, and cracking. The buffer layer 32 is made of undoped high-resistance aluminum nitride, the thickness of the buffer layer 32 is 0.2-3 microns, and the buffer layer 32 has the function that the lattice constant of the buffer layer 32 gradually approaches to the lattice constant of an aluminum nitride crystal along with the increase of the thickness of the buffer layer until the lattice constant is completely the same and reaches 3.11A, so that the dislocation defect between the silicon-based substrate 1 and the single-crystal aluminum nitride film 2 is improved. The thickness of the transition layer 33 is between 0.3-3um, and the transition layer 33 is used for gradually changing the composition of the material of the transition layer 33 to ensure that the lattice constant of the material of the transition layer 33 is finally close to or equal to the lattice constant of the aluminum nitride crystal, thereby achieving lattice adaptation and reducing or eliminating dislocation defects.

It should be noted that the present invention does not limit the specific structure of the intermediate layer 3. The intermediate layer 3 may be a seed layer 31, as shown in fig. 2; the intermediate layer 3 may be a buffer layer 32, as shown in fig. 3; it may be that the intermediate layer 3 is a transition layer 33, as shown in fig. 4; the intermediate layer 3 may be a seed layer 31 and a buffer layer 32 stacked from bottom to top, as shown in fig. 5; the intermediate layer 3 may be a seed layer 31 and a transition layer 33 stacked from bottom to top, as shown in fig. 6; the intermediate layer 3 may be formed by stacking a seed layer 31, a buffer layer 32, and a transition layer 33 from bottom to top, as shown in fig. 7.

It should be noted that, as shown in fig. 6, the seed layer 31 is made of aluminum nitride, and the transition layer 33 is AlGaN, wherein the concentration of the Al component in AlGaN gradually increases from bottom to top, for example, gradually increases from 20% to 100%. When the concentration of the Al component reaches 100%, the concentration of the Ga component becomes zero, and the composition of the transition layer 33 is the same as that of the aluminum nitride film 2, thereby achieving perfect lattice matching. The initial concentration of the Al component may be 20% or any one of 10% to 80%.

As shown in fig. 6, the seed layer 31 is made of gan, and the transition layer 33 is made of AlGaN, wherein the concentration of Al in AlGaN gradually increases from bottom to top, for example, from 0 to 100%. When the concentration of the Al component is zero, the concentration of the Ga component is 100%, and the composition of the transition layer 33 is the same as that of the seed layer 31, thereby achieving perfect lattice matching. When the concentration of the Al component is increased to 100%, the concentration of the Ga component becomes zero, and the composition of the transition layer 33 is the same as that of the aluminum nitride film 2, thereby achieving perfect lattice matching. The initial concentration of the Al component may be 0% or any of 0 to 80%.

Further, as shown in fig. 8, a stress absorbing layer 4 is disposed between the silicon-based substrate 1 and the intermediate layer 3, and the material of the stress absorbing layer 4 includes a silicon nitride compound or a non-silicon nitride compound. The stress absorption layer 4 can effectively absorb the stress generated due to different lattice constants of the materials, and can also effectively absorb the stress caused by different thermal expansion coefficients of the materials, so that dislocation defects, wafer warpage and cracks generated due to the stress are effectively reduced or eliminated, and the performance, the product yield and the reliability of the device are improved.

It should be noted that the stress absorbing layer 4 may be a silicon nitride-based compound, i.e., Si_xN_yE.g. SiN, Si₃N₄SiCN, etc., and may also include unsaturated silicon nitride compounds. Of course, the stress absorbing layer 4 may be other non-silicon nitride based materials.

The stress absorbing layer 4 may be an amorphous structure. The amorphous stress absorbing layer 4 can effectively absorb stress, thereby reducing or eliminating dislocation defects due to lattice mismatch. Furthermore, in some applications, the stress absorbing layer 4 may also be a single crystal or polycrystalline structure. In some applications, the stress absorbing layer 4 is very thin, 1-5nm, in which case the material on the stress absorbing layer 4 may be brought into an epitaxial relationship with the substrate material, thereby reducing dislocation defects in later-grown material layers. In other applications, a sufficiently thick stress absorbing layer 4 is required to effectively absorb stress and dislocation defects due to lattice mismatch or thermal expansion, but if the thickness is too great, the subsequent material layers cannot be brought into epitaxial relationship with the substrate, which is detrimental to the growth of high quality single crystal layers (buffer layer 32, transition layer 33, etc.). The thickness of the stress absorbing layer 4 is 1-20nm, and the specific thickness depends on the composition and crystal structure of the stress absorbing layer 4, the composition, thickness and crystal structure of the subsequently grown material layer, and the composition, thickness and crystal structure of the substrate.

Preferably, the transition layer 33 is a superlattice structure. The superlattice transition layer 33 is composed of compound semiconductors having different compositions which are substituted for each other, and as shown in fig. 9 and 10, the superlattice transition layer 33 is composed of a layer a and a layer B which are compound semiconductor materials having different compositions which are substituted for each other. The composition of the A and B layers may be constant or may vary. The compositional variation may be linear or non-linear, and may be continuous or stepwise. The thicknesses of the A layer and the B layer can be the same or different. The thickness of the A layer at different positions can be the same or different. Similarly, the thicknesses of the B layers at different positions may be the same or different. The combination of the thicknesses of the a and B layers may be of various forms.

The A layer component may be Al_x1In_y1Ga_(1-x1-y1)The N, B layer component may be Al_x2In_y2Ga_(1-x2-y2)N, where x1 ≠ x2, y1 ≠ y2, and when y1 ═ y2 ═ 0, the a layer composition is Al_x1Ga_(1-x1)The component of the N and B layers is Al_x2Ga_(1-x2)N; when x 1-x 2-0, the a layer composition is In_y1Ga_(1-y1)The component of the N and B layers is In_y2Ga_(1-y2)N, and when the composition of the a layer and the B layer In the superlattice transition layer 33 is changed, the concentration of at least one element (Al, Ga, In) is changed. The change of the composition can be realized by changing the process parameters in the manufacturing process. For example, to obtain a higher aluminum composition, an aluminum-containing gas source, such as TMA (trimethylaluminum, C) may be added to the MOCVD reactor₃H₉Al) flow rate. To obtain a higher gallium content, a gallium-containing source gas, such as TMG (trimethylgallium, C) may be added₃H₉Ga) flow rate. Other parameters that may be adjusted include temperature, pressure, etc.

In the superlattice transition layer 33, the aluminum concentration is low in a portion near the substrate (a portion below the superlattice transition layer 33), and the aluminum concentration is high in a portion near the aluminum nitride film 2 (a portion above the superlattice transition layer 33). That is, the composition of aluminum in the superlattice transition layer 33 is gradually increased from bottom to top, so that the lattice constant follows up to or crystallizes the lattice constant of aluminum nitride to achieve lattice matching, thereby reducing or eliminating dislocation defects caused by lattice mismatch. Meanwhile, the superlattice transition layer 33 can reduce stress caused by different thermal expansion coefficients of materials, so that wafer warping or cracking caused by the stress can be reduced or eliminated.

The superlattice transition layer 33 may vary widely depending on application requirements. In some cases, the thickness is between 2-20 um; in other cases, the thickness is between 0.01-2 um. The thickness of the a and B layers in the superlattice transition layer 33 is between 1-20 nm.

An insertion layer 5 is arranged between the transition layer 33 and the silicon-based substrate 1, as shown in fig. 11, so as to further reduce or eliminate stress.

An intervening layer 5 is provided between the transition layer 33 and the aluminum nitride film 2, as shown in fig. 12, to further reduce or eliminate stress.

It should be noted that, when the insertion layer 5 is disposed between the transition layer 33 and the silicon-based substrate 1, and the insertion layer 5 is disposed between the transition layer 33 and the aluminum nitride thin film 2, as shown in fig. 13, the effect of reducing or eliminating stress is best.

The present invention further provides a method for manufacturing a piezoelectric material, which is used for manufacturing the piezoelectric material, and referring to fig. 14, the method for manufacturing a piezoelectric material includes the following steps:

and step S10, forming a stress absorption layer on the silicon-based substrate.

The method for forming the stress absorbing layer is not limited, and the following three methods can be adopted: nitriding the surface of the silicon substrate to form a silicon nitride compound; manufacturing a layer of silicon nitride compound on the surface of a silicon-based substrate; a stress absorbing layer is grown on a device (e.g., MOCVD or MBE epitaxial growth device) used to fabricate subsequent layers of material (nucleation layers, buffer layers, transition layers, etc.), followed by subsequent growth of subsequent layers of material.

And step S20, forming a seed layer on the stress absorption layer.

After the seed layer is formed, the crystal growth quality of a subsequent intermediate layer and the silicon nitride film is improved, and the defects are reduced. The seed layer forming method is usually performed at a relatively low temperature (400-.

And step S30, forming a buffer layer on the seed layer.

The aluminum nitride buffer layer is formed by growing single crystal aluminum nitride, for example: direct nitridation of aluminum (Direct nitridation of aluminum), High nitrogen pressure solution growth (HNPSG-High nitrogen pressure solution growth), Hydride Vapor phase epitaxy (HVPE-Hydride Vapor phase epitaxy growth), Metal Organic Chemical Vapor Deposition (MOCVD-Metal Organic Chemical Vapor Deposition), and Physical Vapor transport growth (PVT-Physical Vapor transport growth). The buffer layer is used for further improving the crystal quality and reducing or eliminating dislocation defects, wafer warpage and cracks.

And step S40, forming a transition layer on the buffer layer.

The transition layer can be formed by adding aluminum-containing gas source or gallium gas source in an MOCVD reaction furnace, and the components of the transition layer are gradually changed by adding the aluminum gas source or the gallium gas source, so that the lattice constant of the transition layer gradually approaches to the lattice constant of the aluminum nitride crystal, thereby achieving lattice adaptation and reducing or eliminating dislocation defects. And the transition layer can also effectively absorb the stress generated in the process of manufacturing and cooling the aluminum nitride film.

And step S50, growing an aluminum nitride film on the transition layer.

There are various methods for making aluminum nitride films. Embodiments of the present invention preferably employ a metalorganic chemical vapor deposition (MOCVD) process that utilizes hydrogen to vaporize metalorganic vapors (e.g., trimethylaluminum and trimethylgallium) and gaseous non-metal hydrides (NH)₃) Is fed into a reaction chamber and thenThe compound is decomposed by heating. The advantages of this method are: (1) the thickness of the synthesized film at the atomic level, namely the novel nano material film, can be controlled. (2) Can be prepared into a large-area uniform film, and is a typical technology which is easy to industrialize. (3) The pure material growth technology does not use a liquid container and a low-temperature growth technology, so that the pollution source is minimized, and the material purity is improved by one order of magnitude compared with other semiconductor material growth technologies.

And step S60, doping the aluminum nitride film through ion implantation, and annealing after doping to obtain the doped aluminum nitride film.

Direct doping of single crystal aluminum nitride is difficult to achieve. The application provides a manufacturing method for obtaining high-quality doped single crystal aluminum nitride, which comprises the following steps: first, a ternary or multicomponent compound containing Al and N, such as Al_xGa_(1-x)N，Al_xIn_(1-x)N，Al_xGa_yIn_(1-x-y)N，Al_xGa_yAs_(1-x-y)N，Al_xGa_yIn_aAs_bP_(1-x-y-a-b)N, etc. The ternary or multicomponent compounds are then doped by ion implantation. In the following description, Al will be referred to_xGa_(1-x)N is illustrated as an example. The same manufacturing method is also applicable to other compounds.

Single crystal Al_xGa_(1-x)The N thin film can be formed by various methods, such as Metal Organic Chemical Vapor Deposition (MOCVD), physical vapor transport growth (PVT), Hydride Vapor Phase Epitaxy (HVPE), and the like. In the following description, the MOCVD method will be exemplified. Other fabrication methods are equally applicable.

When AlGaN is doped, the bond energy for Ga-N is lower than that of Al-N, and the dopant atoms (e.g., Sc) will preferentially replace Ga atoms in the AlGaN crystal to form AlScN or Sc-AlN, i.e., doped monocrystalline aluminum nitride films.

The doping may be performed after the entire AlGaN single crystal thin film is formed, or may be performed in stages. The number of segmentations may be between 2 and 10 and the thickness of each layer between 10 and 1000 nm. For example, if the total thickness is 2um, it can be divided into 5 segments each having a thickness of 40 nm. It can also be carried out in 10 stages, each of 20 nm. The thickness of each section may be the same or different.

If the grown film is quaternary, e.g. Al_xGa_yIn_(1-x-y)N, to achieve rare metal doping, such as Sc doping, and likewise, Sc atoms will preferentially replace Ga and In, forming Sc-doped single crystal AlN crystals.

If binary doping, such as Sc and Er doping, is realized on ternary AlGaN and quaternary AlGaInN, Ga and In the crystal are preferentially replaced to form a single-crystal AlN thin film with binary Sc and Er doping.

The doping may be performed by ion implantation. During doping, the manufacturing process parameters such as temperature, energy, dosage and the like are optimized to meet the requirements on doping elements, doping concentration and doping distribution. The doping temperature is-196 deg.C to 1000 deg.C, energy is 10-2000keV, and dosage is 10¹²/cm²To 10¹⁸/cm²Are not equal.

After ion implantation, the aluminum nitride film can be doped to obtain the doped aluminum nitride film. The annealing treatment helps to recover the structure of the aluminum nitride crystal and eliminate defects, and the annealing temperature of 400-1000 ℃ for 10-120 seconds is preferred in the embodiment of the invention to recover the structure of the aluminum nitride crystal and eliminate defects.

The invention also provides a surface acoustic wave resonator, which comprises the piezoelectric material. The surface acoustic wave resonator is formed by manufacturing an interdigital transducer on a piezoelectric film, so that the conversion of sound energy and electric energy is realized. When two interdigital transducers are formed on the piezoelectric film, a two-port surface acoustic wave resonator is obtained, which includes a piezoelectric film 61 and two interdigital transducers 62 and two reflectors 63 provided on the piezoelectric film 61, as shown in fig. 15. The interdigital transducer 62 (input transducer) at the left end of the piezoelectric film 61 converts an input electric signal into an acoustic wave by the inverse piezoelectric effect, the acoustic wave propagates along the film surface, and the acoustic wave is finally converted into an electric signal by the interdigital transducer 62 (output transducer) at the right end of the piezoelectric film 61 and is output.

Therefore, the surface acoustic wave resonator has all the beneficial effects of the piezoelectric material, and the details are not repeated herein.

It should be noted that, the manufacturing process of the surface acoustic wave resonator provided by the present invention is as follows, as shown in fig. 16:

1) the piezoelectric material is manufactured by the above manufacturing method of the piezoelectric material to obtain the piezoelectric material layer 71, and as shown in fig. 16(a), the thickness of the aluminum nitride thin film contained in the piezoelectric material layer 71 is determined according to the specific application, and the total thickness is between 0.1 and 5 um.

2) Manufacturing the interdigital transducer 72 and the reflection grating 73: the material metal may be Au, Pt, Cu, Al, Mo, Ti, Ta, W, etc. The manufacturing method is different according to different materials. Taking Al metal as an example: al is deposited on the wafer by evaporation or sputtering to obtain a metal layer 711 as shown in fig. 16(b), and then the steps of glue coating, alignment, exposure, development, metal etching, photoresist removal, cleaning, etc. are performed to obtain the interdigital transducer 72 and the reflective grating 73 as shown in fig. 16 (c). The number and spacing of interdigital transducers 72 and reflective gratings 73 will depend upon the particular application and are not intended to be limiting.

3) Alternatively, the passivation layer 74 is fabricated, resulting in the passivation layer 74 as shown in fig. 16 (d): the passivation layer 74 is typically silicon oxide or silicon nitride. Its function is to protect the metal. When the passivation layer 74 is made of silicon oxide or silicon nitride, the passivation layer 74 is generally formed by a Plasma Enhanced Chemical Vapor Deposition (PECVD) method and has a thickness ranging from 10nm to 500 nm. And then the steps of gluing, aligning, exposing, developing, etching, removing glue, cleaning and the like are carried out to finish the open pore etching. The passivation layer 74 may also be fabricated using Atomic Layer Deposition (ALD). The advantages of atomic layer deposition are that the thickness can be made very thin, e.g. 1-50nm, and that a uniform coverage of the metal electrode can be achieved.

The invention also provides an electronic device, which comprises the surface acoustic wave resonator, so that the electronic device has all the beneficial effects of the surface acoustic wave resonator, and the details are not repeated.

Further, the electronic device is a surface acoustic wave filter. Such as IIDT type filters, DMS type filters and Ladder type filters.

The IIDT of a filter of type IIDT is an acronym for Inter-digital transducer, which employs interdigital IDT transducers. Such filters are typically lossy and require external matching circuitry for impedance matching.

The DMS-type filter is a Dual Mode saw filter. The DMS-type filter constructs a filter by disposing IDTs between gratings, realizes a wide operating bandwidth by a combination of respective resonance modes, and matches the input or output of a balanced amplifier by a balanced setting of the input and output; coupling is performed in the longitudinal direction through two identical resonance modes, so that low insertion loss and good out-of-band rejection characteristics are realized.

The third type is a Ladder type filter. The Ladder type filter is constituted by constructing one-port Ladder type surface acoustic wave resonators, generally for one unbalanced input and output, by using two types of one-port surface acoustic wave resonators (one in a series structure and the other in a parallel structure) which have different resonance frequencies and are realized by electrical coupling. Ladder type filters have lower loss characteristics, higher power capability and similar levels of out-of-band rejection.

The surface acoustic wave resonator can be used for manufacturing other devices or devices besides the surface acoustic wave filter, such as temperature and pressure sensors, gas detectors, mass and gravity sensors, radiation detectors, energy collectors, energy converters, chemical and biological sensors, microfluidic devices and the like, and is widely applied to the fields of mobile communication, internet of things, smart homes, WIFI, artificial intelligence, industry, agriculture, navigation, oil field and ocean detection, pipeline leakage monitoring and safety control, aerospace and the like.

The above is only a preferred embodiment of the present invention, and it is not intended to limit the scope of the invention, and various modifications and changes will occur to those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention shall be included in the scope of the present invention.

Claims (10)

1. A piezoelectric material is used for a surface acoustic wave resonator and is characterized by comprising a silicon-based substrate and an aluminum nitride film which are stacked from bottom to top.

2. The piezoelectric material according to claim 1, wherein the aluminum nitride thin film is a single crystal structure; and/or the presence of a gas in the gas,

the aluminum nitride film is a doped aluminum nitride film, and the doped aluminum nitride film is doped with at least one of scandium, yttrium, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, chromium, zirconium, manganese and magnesium.

3. The piezoelectric material according to claim 1 or 2, wherein an intermediate layer is disposed between the silicon-based substrate and the aluminum nitride thin film, the intermediate layer includes a seed layer and/or a buffer layer and/or a transition layer stacked from bottom to top, the seed layer includes a nitride material, the buffer layer includes an aluminum nitride material, the transition layer includes an aluminum nitride material, and the concentration of the aluminum component in the transition layer gradually increases in a direction from bottom to top.

4. The piezoelectric material according to claim 3, wherein a stress absorbing layer is disposed between the silicon-based substrate and the intermediate layer, and the material of the stress absorbing layer includes a silicon nitride compound or a non-silicon nitride compound.

5. The piezoelectric material of claim 3, wherein the transition layer is a superlattice structure.

6. The piezoelectric material of claim 5, wherein an intervening layer is disposed between the transition layer and the silicon-based substrate; and/or the presence of a gas in the gas,

an insertion layer is arranged between the transition layer and the aluminum nitride film.

7. A method for manufacturing a piezoelectric material is characterized by comprising the following steps:

forming a stress absorption layer on a silicon-based substrate;

forming a seed layer on the stress absorption layer;

forming a buffer layer on the seed layer;

forming a transition layer on the buffer layer;

growing an aluminum nitride film on the transition layer;

and doping the aluminum nitride film by an ion implantation method, and annealing after doping to obtain the doped aluminum nitride film.

8. A surface acoustic wave resonator comprising the piezoelectric material according to any one of claims 1 to 6.

9. An electronic device comprising the surface acoustic wave resonator according to claim 8.

10. The electronic device of claim 9, wherein the electronic device is a surface acoustic wave filter, a sensor, or a microfluidic device.

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