CN114070245A - Magnetic tuning film bulk acoustic resonator and preparation method and application thereof - Google Patents
Magnetic tuning film bulk acoustic resonator and preparation method and application thereof Download PDFInfo
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- H—ELECTRICITY
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- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
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- 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
- H03H3/02—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 piezoelectric or electrostrictive resonators or networks
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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
- H03H9/46—Filters
- H03H9/54—Filters comprising resonators of piezo-electric or electrostrictive material
- H03H9/56—Monolithic crystal filters
- H03H9/564—Monolithic crystal filters implemented with thin-film techniques
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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
- H03H9/46—Filters
- H03H9/54—Filters comprising resonators of piezo-electric or electrostrictive material
- H03H9/58—Multiple crystal filters
- H03H9/582—Multiple crystal filters implemented with thin-film techniques
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- 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
- H03H3/02—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 piezoelectric or electrostrictive resonators or networks
- H03H2003/023—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 piezoelectric or electrostrictive resonators or networks the resonators or networks being of the membrane type
Abstract
The invention discloses a magnetic tuning film bulk acoustic resonator and a preparation method and application thereof. The magnetic tuning film bulk acoustic resonator comprises a first electrode, a piezoelectric material layer and a second electrode which are sequentially stacked; the second electrode comprises at least one first material layer and at least one second material layer which are alternately stacked, wherein the at least one first material layer is a magnetostrictive film, and the magnetostrictive film and the piezoelectric material layer are matched to form a magnetoelectric heterojunction. The embodiment of the invention provides a magnetic tuning film bulk acoustic resonator, which takes a magnetic telescopic composite film as an upper electrode and utilizes the magnetoelectric effect of a magnetic material and a piezoelectric material to realize the adjustment of the resonant frequency of an FBAR in the low-frequency, medium-frequency or even high-frequency range under the action of a magnetic field.
Description
Technical Field
The invention particularly relates to a magnetic tuning film bulk acoustic resonator and a preparation method and application thereof, belonging to the technical field of communication.
Background
With the rapid development of 5G technology, there is a strong demand for small-sized, high-frequency, broadband, high-performance and low-power consumption rf filters. Filtering technologies such as Surface Acoustic Wave (SAW), body surface wave (BAW), and Film Bulk Acoustic Resonator (FBAR) have been explored by the industry and academia to better meet the real needs of 5G mobile communications. The Film Bulk Acoustic wave Resonator Filter (Film Bulk Acoustic Resonator Filter) has the advantages of excellent and reliable filtering performance, small volume, low power consumption, easy integration and the like, and is considered to be the best solution of the radio frequency Filter of the current communication terminal.
The film bulk acoustic wave filter is small in tuning range, is a typical narrow-band device, can be freely switched in a plurality of communication frequency bands through one film bulk acoustic wave filter, is adjustable in working bandwidth, meets the requirement of broadband signal processing, and has important value in fully utilizing the precious frequency spectrum resources and simplifying a wireless communication system.
The FBAR frequency adjustment technology mainly focuses on the following three aspects: adjusting in the preparation process, adjusting after preparation and adjusting in the using process. In the FBAR preparation process, the uniformity of a film is improved by Chemical Mechanical Polishing (CMP), a temperature compensation layer is added to reduce frequency drift caused by temperature, and the stability of a device is improved, but the two frequency tuning technologies have smaller flexibility; after preparation, the resonant frequency can be adjusted through film or mass deposition, but the process is complicated and difficult to implement, and the frequency adjustment technology before and after preparation has the problem of small tuning range, and can be suitable for devices with specific high-precision resonant frequency.
The existing tuning scheme in the using process is generally based on the reversible adjustment of the resonance frequency of the FBAR within a certain range based on the changes of external conditions such as an electric field, temperature, a magnetic field and the like, but the existing technology still has the defects of small adjustment range, complex device structure and preparation process, harsh material preparation conditions, difficulty in large-range application and the like, wherein the upper electrode of the FBAR is changed into a magnetic material, and a magnetoelectric heterojunction formed by the magnetic material and a piezoelectric material has a strong magnetoelectric effect. The magnetic material used in the experiment at present mainly comprises a single FeGa or FeCo material, and a certain effect is achieved, but the defects of large driving magnetic field, large hysteresis loss and eddy current loss at high frequency and the like still exist, so that the change of the resonant frequency of the FBAR at high frequency along with the magnetic field is not obvious, although the hysteresis loss and the eddy current loss of the FeGaB material at high frequency are improved well compared with those of the FeGa and FeCo material, and the Young modulus of the FeGaB material is high in variation under the action of the magnetic field, the single material is still difficult to adapt to the application requirement of a modern high-frequency communication system on frequency adjustment.
Disclosure of Invention
The invention mainly aims to provide a magnetic tuning film bulk acoustic resonator, a preparation method and application thereof, so as to overcome the defects in the prior art.
In order to achieve the purpose, the technical scheme adopted by the invention comprises the following steps:
the embodiment of the invention provides a magnetic tuning film bulk acoustic resonator, which comprises a first electrode, a piezoelectric material layer and a second electrode which are sequentially stacked; the method is characterized in that: the second electrode comprises at least one first material layer and at least one second material layer which are alternately stacked, wherein the at least one first material layer is a magnetostrictive film, and the magnetostrictive film and the piezoelectric material layer are matched to form a magnetoelectric heterojunction.
Further, the second material layer includes any one or a combination of a soft magnetic film, an acoustic matching layer, and a magnetostrictive film, but is not limited thereto.
Further, the material of the magnetostrictive film may be FeGa, FeGaB, FeCo, etc., and the material of the acoustic matching layer may be Al2O3And SiO2And the like, the material of the soft magnetic thin film may be NiFe and the like.
In some more specific embodiments, the bottom layer of the second electrode is a first material layer, and the top layer is a second material layer, or both the bottom layer and the top layer of the second electrode are the first material layer, and the second material layer is located between the bottom layer and the top layer.
Further, the bottom layer of the second electrode is grown on the piezoelectric layer.
In some more specific embodiments, the bottom layer of the second electrode is a magnetostrictive film, and the top layer may be one of a soft magnetic film, an acoustic matching layer, and a magnetostrictive film.
Furthermore, the number of the first material layers and the second material layers in the second electrode is equal, or the first material layers are one more than the second material layers; it can be understood that, assuming that the first material layer is a, the second material layer is B, and the number of layers or the number ratio is n, the structure of the second electrode is: (A/B)nOr (A/B)nIn the structure of A, the bottom layer of the second electrode is required to be a magnetostrictive film, and the top layer can be any one of a soft magnetic film, an acoustic matching layer and a magnetostrictive film; wherein A/B represents a film structure formed by alternately depositing a first material layer and a second material layer, and the volume ratio of the two materials is changed as follows: 1: 1-5: 1; if (A/B)nAnd a structure a, wherein a must be the same magnetostrictive material, i.e. the bottom layer and the topmost layer of the second electrode are both the first material layer and are also a magnetostrictive film.
Further, the ratio of the total volume of all the first material layers to the total volume of all the second material layers in the second electrode is 1: 1-5: 1.
in some more specific embodiments, the first electrode, the piezoelectric material layer, and the second electrode are sequentially stacked on the cavity structure.
Further, the first electrode, the piezoelectric material layer and the second electrode are sequentially stacked on a substrate, and the cavity structure is formed in the substrate.
Further, the cavity structure is formed on the first surface of the substrate, and the first electrode, the piezoelectric material layer and the second electrode are sequentially stacked on the first surface of the substrate; or the cavity structure is formed on the second surface of the substrate, and the first electrode, the piezoelectric material layer and the second electrode are sequentially stacked on the first surface of the substrate, wherein the first surface is opposite to the second surface.
Further, the first electrode, the piezoelectric material layer and the second electrode are sequentially stacked on the substrate, wherein at least a local region of the second electrode is recessed along a direction away from the substrate to form a cavity structure.
The embodiment of the invention also provides a preparation method of the magnetic tuning film bulk acoustic resonator, which comprises the steps of manufacturing a first electrode, a piezoelectric material layer, a second electrode and a cavity structure; wherein the step of forming the second electrode comprises: and alternately stacking at least one first material layer and at least one second material layer on the piezoelectric material layer, wherein at least one first material layer is formed by a magnetostrictive film, and the magnetostrictive film is matched with the piezoelectric material layer to form a magnetoelectric heterojunction.
Further, the step of manufacturing the second electrode further includes: first, a first material layer is formed on a piezoelectric material layer to serve as a bottom layer of a second electrode, and then the rest of structure layers forming the second electrode are grown.
The embodiment of the invention also provides a bulk acoustic wave filter which comprises the magnetic tuning film bulk acoustic wave resonator.
The embodiment of the invention also provides a communication device which comprises a radio frequency filter, wherein the radio frequency filter comprises the magnetic tuning film bulk acoustic resonator.
Compared with the prior art, the invention has the advantages that:
1) the embodiment of the invention provides a magnetic tuning film bulk acoustic resonator, which takes a magnetic telescopic composite film as an upper electrode, and realizes the adjustment of the resonant frequency of an FBAR in the low-frequency, medium-frequency or even high-frequency range under the action of a magnetic field by utilizing the magnetoelectric effect of a magnetic material and a piezoelectric material;
2) the invention adopts FeGa, FeCo or FeGaB multilayer composite film, so that the magnetic telescopic composite film has good soft magnetic performance, large magnetostriction, low hysteresis loss and eddy current loss of large piezomagnetic coefficient under high frequency, and further realizes that the resonant frequency of the FBAR can be tuned in a high frequency band through a magnetoelectric coupling mechanism generated by the product effect of a piezoelectric material and a magnetostriction material.
Drawings
Fig. 1 is a schematic structural diagram of a magnetically tuned film bulk acoustic resonator with a recessed air gap according to embodiment 1 of the present invention;
fig. 2 is a schematic structural diagram of a magnetically tuned film bulk acoustic resonator with an upwardly convex cavity structure provided in embodiment 2 of the present invention;
fig. 3 is a schematic structural diagram of a magnetically tuned bulk silicon etched type magnetically tuned thin film bulk acoustic resonator provided in embodiment 3 of the present invention.
Detailed Description
In view of the deficiencies in the prior art, the inventors of the present invention have made extensive studies and extensive practices to provide technical solutions of the present invention. The technical solution, its implementation and principles, etc. will be further explained as follows.
The inventor of the present invention finds that, by adopting a single-layer magnetostrictive material, the problems of large eddy current loss and poor soft magnetic performance at high frequency or the problem of sacrificing the saturation magnetostrictive coefficient of the material itself exist, and further limits the resonant frequency adjustment range of the resonator under the drive of a magnetic field.
In order to realize the large-range frequency adjustment of the FBAR in the low frequency, the medium frequency, and even the high frequency region, the upper electrode (i.e., the second electrode, the same below) of the FBAR device provided in the embodiment of the present invention mainly comprises a magnetostrictive film, and achieves the resonant frequency of the FBAR device based on the magnetostrictive performance and Δ E effect of the magnetostrictive film itself and a magnetoelectric coupling mechanism generated by the product effect of the piezoelectric material and the magnetostrictive material, and achieves the purpose of performing dynamic adjustment in a certain range through a magnetic field.
According to the magnetic tuning film bulk acoustic resonator provided by the embodiment of the invention, the magnetostrictive composite film is used as the upper electrode and forms a magnetoelectric heterojunction with the piezoelectric material layer, theoretical derivation proves that the resonance frequency of the correspondingly formed FBAR device showing the thickness epitaxial vibration mode is determined by the equivalent Young modulus of the magnetoelectric heterojunction, and when the magnetostrictive film is under the action of an external magnetic field, the Young modulus of the magnetostrictive film can be correspondingly changed, and the equivalent Young modulus of the magnetoelectric heterojunction is also correspondingly changed, so that the resonance frequency of the FBAR device is correspondingly changed along with the change of the magnetic field.
The resonant frequency of the magnetic tuning film bulk acoustic wave resonator provided by the embodiment of the invention can be changed to a certain extent along with a magnetic field, so that the switching of the passband center frequency of the bulk acoustic wave filter within the range of 0-100 MHz is realized, and the dynamic modulation is carried out through the magnetic field according to the required application program and operating conditions, so that the number of radio frequency front-end filters for frequency band switching in a modern communication system is greatly reduced, the complexity of equipment is reduced, and the cost of a mobile phone is reduced.
The specific principle is as follows: resonant frequency f of a bulk acoustic wave resonator0Determined by the equivalent young's modulus of the magnetoelectric heterojunction, see formula 1):
in the formula, T0Denotes the thickness of the bulk acoustic wave resonator, equation EeqAnd ρeqFor the equivalent Young's modulus and equivalent density of the resonator, E can be used respectivelyeq＝∑Eivi and ρeq＝∑ρivi, where EiIs Young's modulus, ViIs the volume ratio of each layer of the magnetoelectric heterojunction in the device (namely the volume ratio of each layer of the magnetoelectric heterojunction consisting of the piezoelectric material and the second electrode); therefore, as a magnetic field is applied to the bulk acoustic wave resonator, the mechanical resonance frequency shifts due to the variation of the young's modulus of the magnetostrictive film with the magnetic field (Δ E effect), so that the bulk acoustic wave resonator has magnetic tunability.
At present, the magnetic thin films with the most outstanding magnetostriction performance comprise FeGa, FeGaB, FeCo and the like, the FeGa thin films have large magnetostriction performance and good soft magnetic performance, but the large spin lattice coupling of the high magnetostriction also causes high magnetic hysteresis and large Gilbert damping coefficient, so that the single FeGa thin film is difficult to realize high magnetic elastic coupling; although the FeGaB film has excellent soft magnetic performance and large piezomagnetic coefficient, the doping of B element reduces the saturation magnetostriction and magnetization performance of the FeGaB film.
According to the embodiment of the invention, the FeGa, FeCo or FeGaB magnetostrictive films are compounded with other functional films to form the magnetostrictive composite film as the upper electrode, so that the upper electrode has good soft magnetic performance, large magnetostriction and large piezomagnetic coefficient, hysteresis loss and eddy current loss under high frequency are reduced, and the resonant frequency of the FBAR can be further tuned in a high frequency band through a magnetoelectric coupling mechanism generated by the product effect of the piezoelectric material and the magnetostrictive material.
The embodiments, implementations, principles, and so on of the present invention will be further explained with reference to the drawings and the detailed embodiments, and unless otherwise specified, the thin film fabrication process, the photolithography and etching, and so on used in the embodiments of the present invention are well known to those skilled in the art.
The structures of three magnetic tuning film bulk acoustic wave resonators based on magnetostrictive films provided by the embodiment of the invention are respectively shown in fig. 1, fig. 2 and fig. 3, wherein fig. 1 is a cavity-type (convex) device, fig. 2 is a cavity-type (concave) device and fig. 3 is a bulk silicon etched device.
Referring to fig. 3, taking a bulk silicon etched FBAR as an example, a magnetic tuning bulk silicon etched FBAR includes a high-resistance Si substrate, a buffer layer, a lower electrode (i.e. the first electrode, the same below) and a piezoelectric material layer sequentially disposed on the upper surface of the high-resistance Si substrate, wherein the piezoelectric material layer is provided with an upper electrode and forms a magnetoelectric heterojunction with the piezoelectric material layer, and the upper electrode includes at least one material layer a (i.e. the first material layer, the same below) and a material layer B (i.e. the second material layer, the same below), wherein the material layer a is a magnetostrictive layer, and the material layer B is any one of a soft magnetic film, an acoustic matching layer and a magnetostrictive film.
Specifically, the substrate is a high-resistance silicon substrate, and the high-resistance silicon is selected as the substrate, so that the occurrence of a plurality of parasitic effects can be reduced, and the substrate can be integrated with a CMOS (complementary metal oxide semiconductor) process, so that the cost is reduced; the buffer layer can be an AlN layer, the lower electrode is a metal electrode, and the material of the lower electrode can be any one of Mo, Pt, Al, W and Ru.
Specifically, the selectable material of the piezoelectric material layer includes binary piezoelectric single crystal (which can be formed by metal organic chemical vapor deposition process) or polycrystalline thin films AlN, ZnO (which can be formed by magnetron sputtering process), ternary or multicomponent piezoelectric polycrystalline thin films AlScN, AlErN, BaSrTiO3And a ternary system piezoelectric single crystal film (which can be manufactured by adopting a grinding and thinning process or an intelligent stripping process) LiNbO3、LiTaO3。
In some more specific embodiments, the layers of the a material layer and the B material layer in the upper electrode may be the same and alternately arranged, for example, the upper electrode may be formed by a multilayer magnetostrictive film and a multilayer soft magnetic film; the multilayer magnetostrictive film and the multilayer acoustic matching layer can also be composed of various multilayer magnetostrictive films, and the following conditions are specifically provided:
1) the A material layer in the magnetostrictive film is a magnetostrictive film with certain thickness such as FeGa, FeGaB or FeCo, and the B material layer is Al with certain thickness2O3And SiO2An equal acoustic matching layer; for example, the upper electrode may be [ FeGaB (45nm)/Al2O3(5nm)]X 10 or FeGa (450nm)/Al2O3(50nm) multilayer magnetostrictive composite film, compared with the magnetostrictive film with the same thickness, the magnetostrictive composite film comprising the acoustic matching layer can realize acoustic matching, can increase the resistance of a single magnetostrictive film, enables the composite film to have better high-frequency soft magnetic characteristics, and can effectively reduce eddy current loss and Gilbert damping (note: taking the total thickness of the film of 500nm as an example, the specific structure is two [ A (45 nm)/Al: ])2O3(5nm)]X 10 and A (45nm)/Al2O3(50nm) in which AIs one of magnetostrictive films such as FeGa, FeGaB or FeCo);
2) the A material layer in the upper electrode is a magnetostriction film (not including FeGaB) with certain thickness such as FeGa, FeCo and the like, and the B material layer is a NiFe soft magnetic film with certain thickness; for example, the upper electrode may be [ FeGa/NiFe ]]nThin film or [ FeGa/NiFe]nThe exchange coupling effect between the soft magnetic film and the magnetostrictive film can further improve the piezomagnetic coefficient of the upper electrode due to the addition of the NiFe soft magnetic film, so that [ FeGa/NiFe ]]nThe film has high magnetic permeability and low coercive force of NiFe and high saturation magnetostriction and saturation magnetization of FeGa and the like, so that the FMR line width of single-phase FeGa under the same thickness is reduced, and hysteresis loss and eddy current loss under high frequency are reduced to a great extent, and the film is very suitable for a strain-mediated ME heterojunction; notably, [ FeGa/NiFe ]]nThe total thickness of the film, the thickness of each layer of the FeGa film and the NiFe film and the volume ratio between the FeGa film and the NiFe film can be changed correspondingly according to actual requirements.
Example 1
Referring to fig. 1, a magnetic tuning film bulk acoustic resonator with a recessed air gap includes a high-resistance Si substrate, and an AlN buffer layer, a Mo electrode, an AlN piezoelectric material layer, and [ FeGa/NiFe ] sequentially stacked on the upper surface of the high-resistance Si substrate]nThin film of [ FeGa/NiFe ]]nA film is stacked on the AlN piezoelectric material layer and used as an upper electrode, and the [ FeGa/NiFe ]]nThe thin film is combined with the AlN piezoelectric material layer to form a magnetoelectric heterojunction; and the upper surface of the high-resistance Si substrate is also provided with at least one groove, and the upper surface of the high-resistance Si substrate and the inner wall of the groove are also covered with SiO2And a passivation layer.
In this embodiment, a manufacturing process of a magnetic tuning film bulk acoustic resonator with a recessed air gap includes:
1) cleaning the high-resistance silicon substrate: sequentially carrying out ultrasonic treatment on the mixture for 5min by using acetone, ultrasonic treatment on the mixture for 5min by using isopropanol and ultrasonic treatment on the mixture for 2min by using deionized water, wherein the mixture is repeatedly washed for 5 times by using the deionized water;
2) processing the upper surface of the high-resistance silicon substrate by adopting a Reactive Ion Etching (RIE) mode to form a groove cavity structure with the depth of 2.5 mu m;
3) forming a layer of 200nm SiO on the upper surface, the bottom and the four walls of the high-resistance silicon substrate at 350 ℃ by adopting a Plasma Enhanced Chemical Vapor Deposition (PECVD) method2A cavity passivation layer for preventing the subsequent process from generating adverse effect on the high-resistance silicon substrate;
4) depositing a layer of amorphous silicon in the cavity by adopting a PECVD (plasma enhanced chemical vapor deposition) mode to be used as a sacrificial layer, wherein the thickness of the sacrificial layer is larger than that of the cavity, so that the sufficient grinding thickness is ensured during CMP;
5) performing Chemical Mechanical Polishing (CMP) treatment on the upper surface of the high-resistance silicon substrate to retain SiO originally deposited on the upper surface of the high-resistance silicon substrate2Passivating layer of cavity, and is higher than SiO2Removing partial amorphous Si on the edge of the cavity passivation layer and the upper surface of the cavity to ensure that the upper surface of the amorphous Si of the sacrificial layer and SiO on the substrate outside the cavity2The upper surface of the cavity passivation layer is in the same level, and only amorphous Si which is used as a sacrificial layer in the cavity is left and is cleaned;
6) depositing a thin (50nm) AlN buffer layer, a Mo metal lower electrode with a certain thickness (200nm), a (1 mu m) AlN piezoelectric material layer and [ FeGa/NiFe ] on the upper surface of the high-resistance silicon substrate in sequence by means of magnetron sputtering and the like]nA film;
7) etching out [ FeGa/NiFe ] by Ion Beam Etching (IBE)]16An upper electrode pattern;
8) etching the AlN pattern of the piezoelectric material by using an Inductively Coupled Plasma (ICP) etching machine (Oxford ICP180), wherein the etching gas is as follows: cl2:BCl3Ar is 32sccm, 8sccm, 5sccm, wherein Cl is2And BCl3Plays a role in reacting with AlN, and Ar is used for physical bombardment;
9) etching the lower electrode Mo pattern by an Inductively Coupled Plasma (ICP) etching machine (Oxford ICP380), wherein the etching gas is: the etching rate of SF 680 sccm is about 4.7 nm/s;
10) growth of 400nmSiO by means of PECVD (350 ℃), in particular2Isolation layer and etching by reactive ion(RIE) etching the isolation layer pattern;
11) adopting a liff-off process, evaporating a Ti/Au upper electrode with 30nm/200nm by an Ei-5z electron beam, then stripping, and patterning an upper electrode area;
12) obtaining a release window around the cavity by dry etching, injecting HF solution from the release window, and injecting SiO2And removing the isolation layer to form a cavity.
Example 2
Referring to fig. 2, a magnetic tuning film bulk acoustic resonator with an upward-convex cavity structure includes a Si (100) substrate, and an AlN buffer layer, a Mo electrode, an AlN piezoelectric material layer, and [ FeGa/NiFe ] sequentially stacked on the upper surface of the Si (100) substrate]nThin film of [ FeGa/NiFe ]]nA film is stacked on the AlN piezoelectric material layer and used as an upper electrode, and the [ FeGa/NiFe ]]nThe thin film is combined with the AlN piezoelectric material layer to form a magnetoelectric heterojunction; and at least one groove is further formed in the surface of one side, close to the Si substrate, of the AlN buffer layer.
In this embodiment, a process for manufacturing a magnetically tuned film bulk acoustic resonator with an upward convex cavity structure includes:
1) cleaning the high-resistance silicon substrate: sequentially carrying out ultrasonic treatment on the mixture for 5min by using acetone, ultrasonic treatment on the mixture for 5min by using isopropanol and ultrasonic treatment on the mixture for 2min by using deionized water, wherein the mixture is repeatedly washed for 5 times by using the deionized water;
2) depositing a layer of metal germanium on the upper surface of the high-resistance silicon substrate as a sacrificial layer;
3) depositing a thin (50nm) AlN buffer layer, a lower electrode Mo metal layer with a certain thickness (200nm), a (1 mu m) AlN piezoelectric material layer and 480nm [ FeGa/NiFe ] on the upper surface of the high-resistance silicon substrate in sequence by adopting a magnetron sputtering mode]16A film;
4) etching out [ FeGa/NiFe ] by Ion Beam Etching (IBE)]16An upper electrode pattern;
5) etching the AlN pattern of the piezoelectric material by using an Inductively Coupled Plasma (ICP) etching machine (Oxford ICP180), wherein the etching gas is as follows: cl2:BCl3Ar is 32sccm, 8sccm, 5sccm, wherein Cl is2And BCl3Plays a role in reacting with AlN, and Ar is used for physical bombardment;
6) etching the lower electrode Mo pattern by an Inductively Coupled Plasma (ICP) etching machine (Oxford ICP380), wherein the etching gas is: the etching rate of SF 680 sccm is about 4.7 nm/s;
7) growth of 400nmSiO by means of PECVD (350 ℃), in particular2Etching the isolation layer by Reactive Ion Etching (RIE) to form an isolation layer pattern;
8) evaporating Ti/Au upper electrode 30nm/200nm by Ei-5z electron beam by liff-off process, stripping, and patterning upper electrode region
9) Dry etching to obtain a release window around the cavity2O2Injecting the solution from the release window to inject SiO2And removing the isolation layer to form a cavity.
Example 3
Referring to fig. 3, a magnetic tuning bulk silicon etching type magnetic tuning film bulk acoustic resonator comprises a high-resistance Si (100) substrate, and an AlN buffer layer, a Mo electrode, an AlN piezoelectric material layer and [ FeGa/NiFe ] sequentially stacked on the upper surface of the high-resistance Si (100) substrate]nThin film of [ FeGa/NiFe ]]nA film is stacked on the AlN piezoelectric material layer and used as an upper electrode, and the [ FeGa/NiFe ]]nThe thin film is combined with the AlN piezoelectric material layer to form a magnetoelectric heterojunction; and a through hole penetrating through the Si substrate along the thickness direction is further formed in the Si substrate.
Specifically, [ FeGa/NiFe ]]nThe film is sequentially provided with FeGa/NiFe/FeGa/NiFe … … FeGa/NiFe structures from the bottommost layer to the topmost layer, when [ FeGa/NiFe]nAfter the total thickness of the film is fixed, a proper film combination can be selected according to actual requirements in two aspects of the layer number and the volume ratio of FeGa to NiFe:
for example, [ FeGa/NiFe ]]nThe total thickness of the film was 480nm, [ FeGa/NiFe ] when n is 1]nThe composition of the film is: (240nmFeGa/240 nmNiFe); when n is 8, [ FeGa/NiFe]nThe film composition is as follows: (30nmFeGa/30nm NiFe)8(ii) a When n is 16, [ FeGa/NiFe]nThe film composition is as follows: (15nmFeGa/15nm NiFe)16(ii) a When n is 3At 0, [ FeGa/NiFe ]]nThe film composition is as follows: (8nmFeGa/8nm NiFe)30。
It should be noted that [ FeGa/NiFe ] theoretically increases with the number of layers]nThe performance of the film will first become better (i.e. have high magnetostriction of FeGa and good soft magnetic performance of NiFe) and then deteriorate, and the specific number of layers depends on the process conditions of the actual growth of the material (as the number of layers increases [ FeGa/NiFe ]]nStress between each layer of the film can seriously obstruct the subsequent processing and preparation of the device, and the device is easy to fail) and the practical application requirement.
In this embodiment, a process for manufacturing a magnetically tuned bulk silicon etched type magnetically tuned film bulk acoustic resonator includes:
1) cleaning the high-resistance silicon substrate: sequentially carrying out ultrasonic treatment on the mixture for 5min by using acetone, ultrasonic treatment on the mixture for 5min by using isopropanol and ultrasonic treatment on the mixture for 2min by using deionized water, wherein the mixture is repeatedly washed for 5 times by using the deionized water;
2) depositing a thin (50nm) AlN buffer layer, a lower electrode Mo metal layer with a certain thickness (200nm), a (1 mu m) AlN piezoelectric material layer and 480nm [ FeGa/NiFe ] on the upper surface of the high-resistance silicon substrate in sequence by adopting a magnetron sputtering mode]16A film;
3) etching out [ FeGa/NiFe ] by Ion Beam Etching (IBE)]16An upper electrode pattern;
4) etching the AlN pattern of the piezoelectric material by using an Inductively Coupled Plasma (ICP) etching machine (Oxford ICP180), wherein the etching gas is as follows: cl2:BCl3Ar is 32sccm, 8sccm, 5sccm, wherein Cl is2And BCl3Plays a role in reacting with AlN, and Ar is used for physical bombardment;
5) etching the lower electrode Mo pattern by an Inductively Coupled Plasma (ICP) etching machine (Oxford ICP380), wherein the etching gas is: SF6The etching rate of 80sccm is about 4.7 nm/s;
6) growth of 400nmSiO by means of PECVD (350 ℃), in particular2Etching the isolation layer by Reactive Ion Etching (RIE) to form an isolation layer pattern;
7) adopting a liff-off process, evaporating a Ti/Au upper electrode with 30nm/200nm by an Ei-5z electron beam, then stripping, and patterning an upper electrode area;
8) and (3) high-resistance silicon thinning and polishing (from 695 mu m to 100 mu m), forming a shape corresponding to the upper electrode resonance region by adopting a back overlay technology of a double-sided photoetching machine MA6, and finally releasing a window through a deep silicon etching process to form an air interface in the lower electrode region.
Example 4
A magnetically tuned bulk silicon etching type magnetically tuned film bulk acoustic resonator comprises a high-resistance Si (100) substrate, and an AlN buffer layer, a Mo electrode, an AlN piezoelectric material layer and (FeGa/NiFe) which are sequentially stacked on the upper surface of the high-resistance Si (100) substratenFeGa film, [ FeGa/NiFe ]]nAnd the magnetostrictive film is stacked on the AlN piezoelectric material layer and is used as an upper electrode.
Specifically, (FeGa/NiFe)nThe FeGa films and the NiFe films in the FeGa films are sequentially and alternately arranged, the bottommost layer and the topmost layer are the FeGa films, and when the total thickness of the magnetostrictive film is fixed and the FeGa to NiFe (volume ratio) is kept unchanged, the number n of layers is adjusted according to actual requirements; for example, (FeGa/NiFe)nWhen the total thickness of the FeGa film is 100nm and the volume ratio of FeGa to NiFe is 1:1, the number of layers of the FeGa film and the NiFe film is shown in Table 1:
table 1 shows the structural parameters of the magnetostrictive films
When (FeGa/NiFe)nAfter the total thickness of the FeGa film and the number n of layers are fixed, the volume ratio of the FeGa film to the NiFe film can be changed, for example, (FeGa/NiFe)nWhen the total thickness of the FeGa thin film is 100nm and the number of layers n is 3, the volume ratio of the FeGa thin film to the NiFe thin film is shown in table 2:
table 2 shows the structural parameters of the magnetostrictive films
Example 5
A magnetically tuned bulk silicon etching type magnetically tuned film bulk acoustic resonator comprises a high-resistance Si (100) substrate, and an AlN buffer layer, a Mo lower electrode, an AlN piezoelectric material layer and (FeGa/Al) sequentially stacked on the upper surface of the high-resistance Si (100) substrate2O3)nOr (FeGaB/Al)2O3)nThin film of (FeGa/Al)2O3)nOr (FeGaB/Al)2O3)nAnd the thin film is stacked on the AlN piezoelectric material layer and is used as an upper electrode.
Specifically, after the thickness of the FeGa film is determined, the number n of layers is determined according to the actual application requirement, wherein Al is2O3The thickness of (A) can be selected to be a relatively suitable thickness of 5nm, which has been proven at present, for example (FeGa/Al)2O3)nThe total thickness of the film is 500nm, n is defined as 10 layers, then (FeGa/Al)2O3)nThe configuration of the film is: (45nmFeGa/5nmAl2O3)10Or is (41nmFeGa/5nmAl2O3)10/41nmFeGa。
In this embodiment, a process for manufacturing a magnetically tuned bulk silicon etched type magnetically tuned film bulk acoustic resonator includes:
1) cleaning the high-resistance silicon substrate: sequentially carrying out ultrasonic treatment on the mixture for 5min by using acetone, ultrasonic treatment on the mixture for 5min by using isopropanol and ultrasonic treatment on the mixture for 2min by using deionized water, wherein the mixture is repeatedly washed for 5 times by using the deionized water;
2) depositing a thin (50nm) AlN buffer layer, a lower electrode Mo metal layer with a certain thickness (200nm), a (1 mu m) AlN piezoelectric material layer and a (45nm FeGa/5nm Al) AlN piezoelectric material layer on the upper surface of the high-resistance silicon substrate in sequence by adopting a magnetron sputtering mode2O3)10A film;
3) etching (45nmFeGa/5 nmAl) by Ion Beam Etching (IBE)2O3)10An upper electrode pattern;
4) etching the AlN pattern of the piezoelectric material by an Inductively Coupled Plasma (ICP) etching machine (Oxford ICP180), wherein etching gas is used for etching the AlN patternThe body is as follows: cl2:BCl3Ar is 32sccm, 8sccm, 5sccm, wherein Cl is2And BCl3Plays a role in reacting with AlN, and Ar is used for physical bombardment;
5) etching the lower electrode Mo pattern by an Inductively Coupled Plasma (ICP) etching machine (Oxford ICP380), wherein the etching gas is: the etching rate of SF 680 sccm is about 4.7 nm/s;
6) growth of 400nmSiO by means of PECVD (350 ℃), in particular2Etching the isolation layer by Reactive Ion Etching (RIE) to form an isolation layer pattern;
7) adopting a liff-off process, evaporating a Ti/Au upper electrode with 30nm/200nm by an Ei-5z electron beam, then stripping, and patterning an upper electrode area;
8) and (3) high-resistance silicon thinning and polishing (from 695 mu m to 100 mu m), forming a shape corresponding to the upper electrode resonance region by adopting a back overlay technology of a double-sided photoetching machine MA6, and finally releasing a window through a deep silicon etching process to form an air interface in the lower electrode region.
Example 6
A magnetically tuned bulk silicon etching type magnetically tuned film bulk acoustic resonator comprises a Si substrate, and an AlN buffer layer, a Mo electrode, an AlN piezoelectric material layer and FeGa/Al which are sequentially stacked on the upper surface of the Si substrate2O3Or (FeGa/NiFe) n/Al2O3Film of said FeGa/Al2O3Or (FeGa/NiFe) n/Al2O3And the thin film is stacked on the AlN piezoelectric material layer and is used as an upper electrode.
For example, the upper electrode may be 450nmFeGa/50nmAl2O3Thin film, which is the simplest of FeGa and Al2O3Combining, namely depositing a FeGa film with a certain thickness in advance and depositing Al with a certain thickness2O3Thin films of FeGa and Al2O3The specific thickness is determined by actual requirements.
It should be noted that the FeGa in the above examples may be replaced by FeGa or various combinations of the aforementioned FeGa/NiFe.
In this embodiment, a process for manufacturing a magnetically tuned bulk silicon etched type magnetically tuned film bulk acoustic resonator includes:
1) cleaning the high-resistance silicon substrate: sequentially carrying out ultrasonic treatment on the mixture for 5min by using acetone, ultrasonic treatment on the mixture for 5min by using isopropanol and ultrasonic treatment on the mixture for 2min by using deionized water, wherein the mixture is repeatedly washed for 5 times by using the deionized water;
2) depositing a thin (50nm) AlN buffer layer, a lower electrode Mo metal layer with a certain thickness (200nm), a (1 mu m) AlN piezoelectric material layer and 450nmFeGa/50nmAl on the upper surface of the high-resistance silicon substrate in sequence by adopting a magnetron sputtering mode2O3A film;
3) etching to obtain 450nmFeGa/50nmAl by Ion Beam Etching (IBE)2O3An upper electrode pattern;
4) etching the AlN pattern of the piezoelectric material by using an Inductively Coupled Plasma (ICP) etching machine (Oxford ICP180), wherein the etching gas is as follows: cl2:BCl3Ar is 32sccm, 8sccm, 5sccm, wherein Cl is2And BCl3Plays a role in reacting with AlN, and Ar is used for physical bombardment;
5) etching the lower electrode Mo pattern by an Inductively Coupled Plasma (ICP) etching machine (Oxford ICP380), wherein the etching gas is: the etching rate of SF 680 sccm is about 4.7 nm/s;
6) growth of 400nmSiO by means of PECVD (350 ℃), in particular2Etching the isolation layer by Reactive Ion Etching (RIE) to form an isolation layer pattern;
7) adopting a liff-off process, evaporating a Ti/Au upper electrode with 30nm/200nm by an Ei-5z electron beam, then stripping, and patterning an upper electrode area;
8) and (3) high-resistance silicon thinning and polishing (from 695 mu m to 100 mu m), forming a shape corresponding to the upper electrode resonance region by adopting a back overlay technology of a double-sided photoetching machine MA6, and finally releasing a window through a deep silicon etching process to form an air interface in the lower electrode region.
Comparative example 1
The structure and the manufacturing process of the magnetic tuning film bulk acoustic resonator with the concave air gap are basically consistent with those of the embodiment 1, and the difference is that: comparative example 1 Using FeGa film as an upper electrodeAnd the FeGa film is the same as [ FeGa/NiFe ] in example 1]nThe magnetostrictive films were of the same thickness.
Comparative example 2
The structure and the manufacturing process of the magnetic tuning film bulk acoustic resonator with the convex-type cavity structure are basically the same as those of the embodiment 2, and the difference is that: comparative example 2 using a FeGa film as an upper electrode, and the FeGa film was compared with [ FeGa/NiFe ] in example 2]nThe magnetostrictive films were of the same thickness.
Comparative example 3
A magnetically tuned bulk silicon etched type magnetically tuned bulk acoustic resonator having a structure and fabrication process substantially the same as those of embodiment 3, except that: comparative example 3 using a FeGa film as an upper electrode, and the FeGa film was compared with [ FeGa/NiFe ] in example 3]nThe magnetostrictive films were of the same thickness.
Through comparative tests of the devices in examples 1-6 and comparative examples 1-3, the inventors of the present invention found that a single FeGa film and [ FeGa/NiFe ] with the same thickness are used]nCompared with the magnetostrictive thin film, the relevant magnetic properties, such as eddy current loss, coercive force, FMR line width and piezomagnetic coefficient, are deteriorated, specifically, the large eddy current loss, the high coercive force, the large FMR and the small piezomagnetic coefficient are shown, so that the magnetoelectric coupling property between the FeGa thin film and the piezoelectric material is deteriorated, and the change of the resonant frequency of the device is reduced or the response to the magnetic field is weakened under the action of the same magnetic field.
The devices of comparative examples 1 to 3 are slightly different in structure, but the core of the devices is that three different air gap structures are used to confine the acoustic wave to the piezoelectric oscillation stack (FBAR is a film bulk acoustic resonator, and the core structure is a sandwich piezoelectric oscillation stack composed of electrodes/piezoelectric layers/electrodes, operating in a thickness direction oscillation mode, applying a radio frequency voltage between upper and lower electrodes, converting an electrical signal into an acoustic wave by using piezoelectricity of a material, and by a transmission line theory, in order to confine the acoustic wave to the piezoelectric stack, it is necessary that load acoustic impedances of the upper and lower electrodes are zero or infinite, the acoustic wave forms a standing wave between two interfaces to generate resonance, acoustic impedance of air is approximately 0, which is a good reflection medium, the upper electrode of the device is exposed in air, and a good acoustic reflection interface is formed on the top, so that an air interface is introduced on the lower surface by micromachining, so there are three structures herein) but the three structures have no effect on the change in the resonant frequency of the device under a magnetic field. The embodiment of the invention provides a magnetic tuning film bulk acoustic resonator, which takes a magnetic telescopic composite film as an upper electrode, and realizes the adjustment of the resonant frequency of an FBAR in the low-frequency, medium-frequency or even high-frequency range under the action of a magnetic field by utilizing the magnetoelectric effect of a magnetic material and a piezoelectric material; in addition, the invention adopts FeGa, FeCo or FeGaB multilayer composite film, so that the magnetic telescopic composite film has good soft magnetic performance, large magnetostriction, low hysteresis loss and eddy current loss of large piezomagnetic coefficient under high frequency, and further realizes that the resonant frequency of the FBAR can be tuned in a high frequency band through a magnetoelectric coupling mechanism generated by the product effect of the piezoelectric material and the magnetostriction material.
It should be understood that the above-mentioned embodiments are merely illustrative of the technical concepts and features of the present invention, which are intended to enable those skilled in the art to understand the contents of the present invention and implement the present invention, and therefore, the protection scope of the present invention is not limited thereby. All equivalent changes and modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.
Claims (15)
1. A magnetic tuning film bulk acoustic resonator comprises a first electrode, a piezoelectric material layer and a second electrode which are sequentially stacked; the method is characterized in that: the second electrode comprises at least one first material layer and at least one second material layer which are alternately stacked, wherein the at least one first material layer is a magnetostrictive film, and the magnetostrictive film and the piezoelectric material layer are matched to form a magnetoelectric heterojunction.
2. The magnetically tuned thin film bulk acoustic resonator according to claim 1, wherein: the second material layer comprises any one or combination of a soft magnetic film, an acoustic matching layer and a magnetostrictive film.
3. The magnetically tuned thin film bulk acoustic resonator according to claim 1, wherein: the bottom layer of the second electrode is a first material layer, and the top layer of the second electrode is a second material layer, or the bottom layer and the top layer of the second electrode are the first material layer, and the second material layer is positioned between the bottom layer and the top layer.
4. The magnetically tuned film bulk acoustic resonator according to claim 3, wherein: the bottom layer of the second electrode is grown on the piezoelectric layer.
5. The magnetically tuned thin film bulk acoustic resonator according to claim 1, wherein: the bottom layer of the second electrode is a magnetostrictive film, and the top layer of the second electrode is one of a soft magnetic film, an acoustic matching layer and a magnetostrictive film.
6. The magnetically tuned thin film bulk acoustic resonator according to claim 1, wherein: the number of the first material layers and the second material layers in the second electrode is equal, or the first material layers are more than the second material layers.
7. The magnetically tuned thin film bulk acoustic resonator according to claim 1, wherein: the ratio of the total volume of all the first material layers to the total volume of all the second material layers in the second electrode is 1: 1-5: 1.
8. the magnetically tuned thin film bulk acoustic resonator according to claim 1, wherein: the first electrode, the piezoelectric material layer and the second electrode are sequentially stacked on the cavity structure.
9. The magnetically tuned thin film bulk acoustic resonator according to claim 8, wherein: the first electrode, the piezoelectric material layer and the second electrode are sequentially stacked on a substrate, and the cavity structure is formed in the substrate.
10. The magnetically tuned thin film bulk acoustic resonator according to claim 9, wherein: the cavity structure is formed on the first surface of the substrate, and the first electrode, the piezoelectric material layer and the second electrode are sequentially stacked on the first surface of the substrate; or the cavity structure is formed on the second surface of the substrate, and the first electrode, the piezoelectric material layer and the second electrode are sequentially stacked on the first surface of the substrate, wherein the first surface is opposite to the second surface.
11. The magnetically tuned thin film bulk acoustic resonator according to claim 8, wherein: the first electrode, the piezoelectric material layer and the second electrode are sequentially stacked on the substrate, wherein at least a local area of the second electrode is recessed along a direction far away from the substrate to form a cavity structure.
12. A method of manufacturing a magnetically tuned thin film bulk acoustic resonator as claimed in any of the claims 1-11, comprising the steps of fabricating a first electrode, a layer of piezoelectric material, a second electrode and a cavity structure; wherein the step of forming the second electrode comprises: and alternately stacking at least one first material layer and at least one second material layer on the piezoelectric material layer, wherein at least one first material layer is formed by a magnetostrictive film, and the magnetostrictive film is matched with the piezoelectric material layer to form a magnetoelectric heterojunction.
13. The method of claim 12, wherein the step of forming a second electrode further comprises: first, a first material layer is grown to serve as a bottom layer of the second electrode, and then the rest of structure layers forming the second electrode are grown on the bottom layer.
14. A bulk acoustic wave filter comprising a magnetically tuned thin film bulk acoustic resonator according to any of claims 1 to 11.
15. A communication device comprising a radio frequency filter, characterized in that: the radio frequency filter comprising a magnetically tuned thin film bulk acoustic resonator as claimed in any one of claims 1 to 11.
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| CN115603698A (en) * | 2022-11-28 | 2023-01-13 | 电子科技大学（Cn） | Tunable film bulk acoustic resonator based on elastic softening effect |
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| CN114566792A (en) * | 2022-03-02 | 2022-05-31 | 中国科学院苏州纳米技术与纳米仿生研究所 | Acoustic drive magnetoelectric antenna and preparation method thereof |
| CN114566792B (en) * | 2022-03-02 | 2024-04-19 | 中国科学院苏州纳米技术与纳米仿生研究所 | Acoustic drive magneto-electric antenna and preparation method thereof |
| CN115603698A (en) * | 2022-11-28 | 2023-01-13 | 电子科技大学（Cn） | Tunable film bulk acoustic resonator based on elastic softening effect |
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