CN108649916B - Film bulk acoustic resonator and method for leading out back electrode thereof - Google Patents
Film bulk acoustic resonator and method for leading out back electrode thereof Download PDFInfo
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- H03H3/007—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks
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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
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Abstract
The invention belongs to the technical field of film bulk acoustic resonators, and discloses a film bulk acoustic resonator and a method for leading out a back electrode of the film bulk acoustic resonator. The film bulk acoustic resonator comprises a substrate, wherein a back electrode and a piezoelectric layer are sequentially arranged on the substrate, a groove is formed in the surface of the substrate, an air cavity is formed by the back electrode and the groove in the surface of the substrate, a through hole is formed in the piezoelectric layer, the back electrode is arranged below the through hole, a top electrode is arranged on the piezoelectric layer on one side of the through hole, and back electrode materials are arranged in the other side of the through hole and the through hole. The back electrode leading-out method mainly comprises the steps of preparing a through hole on a piezoelectric film, arranging a back electrode below the through hole, depositing a top electrode on the piezoelectric film on one side of the through hole, depositing back electrode materials on the piezoelectric film on the other side of the through hole and in the through hole, and leading out the back electrode through the through hole. The invention avoids etching the piezoelectric film in large area, and has less damage to the film; the through hole leading-out electrode is easy to cover; the invention can reduce the size of the device, reduce the power consumption and improve the performance.
Description
Technical Field
The invention belongs to the technical field of film bulk acoustic resonators, and particularly relates to a film bulk acoustic resonator and a method for leading out a back electrode of the film bulk acoustic resonator.
Background
In the last decade, as the demand of the internet communication field for the radio frequency signal receiving technology becomes higher, the advantages of the Film Bulk Acoustic Resonator (FBAR) technology itself are gradually revealed. A very important part of mobile communication terminals is the rf filter, and in the past, handsets usually only operate in a few bands in a specific region of the world, but at present, handsets operate in multiple radio bands at substantially the same time, so handset manufacturers have begun to expand the use of FBAR technology to solve the problem faced by 4G/LTE. At present, filters adopting the FBAR technology are introduced into smart phone designs of 15 different working frequency bands in the United states, Europe, Asia and other regions, the FBAR technology becomes mainstream, and the market demand is huge. At this stage, many semiconductor manufacturing companies and academic institutions put a great deal of time and effort on the research of FBAR technology. Meanwhile, the research range of the FBAR academia is gradually expanded, including an acoustic propagation model of the FBAR, preparation and properties of materials, and application of the FBAR in a sensor direction.
In testing RF (radio frequency) and microwave characteristics of FBAR chips, a ground-signal-ground (GSG) probe is typically used to implement a coplanar waveguide structure to achieve the desired accuracy and characteristic impedance feeding, which requires that the signal and ground terminals of the bare chip be coplanar during GSG testing. In order to meet the requirement, the traditional process utilizes a process method that a back electrode, a piezoelectric film and a top electrode are sequentially deposited on a substrate, a pattern covered by a step is formed by an etching or corrosion method, and the step formed by the etched piezoelectric film is covered by the metal of the top electrode and is extended to the plane of the back electrode. In the process method, the process of leading the top electrode to the back electrode table is complex, the electrode coverage at the step is poor, and great stress exists at the interface of the electrode film and the piezoelectric film.
Disclosure of Invention
In order to overcome the defects and shortcomings of the prior art, the invention aims to provide a method for leading out a back electrode in a film bulk acoustic resonator and the film bulk acoustic resonator obtained by the method. The invention prepares through holes on the piezoelectric film, then deposits electrode material on the surface of the piezoelectric film and in the through holes, and the back electrode under the piezoelectric film is led to the upper surface of the piezoelectric layer through the through holes. The invention can avoid the problem of poor coverage of metal steps by utilizing the metal through holes. And moreover, the back electrode is led out through the through hole, the length of an electrode wire can be shortened, the size and parasitic parameters of the device are reduced, the power consumption is reduced, the performance of the device is improved, and the method is suitable for manufacturing the radio frequency filter in high-frequency and high-power occasions.
The purpose of the invention is realized by the following technologies:
a back electrode leading-out method in a film bulk acoustic resonator comprises the following steps:
the method comprises the steps of sequentially depositing a back electrode and a piezoelectric film on a substrate with a groove in the surface, forming an air cavity by the back electrode and the groove in the surface of the substrate, then preparing a through hole on the piezoelectric film, forming the back electrode below the through hole, depositing a top electrode on the piezoelectric film on one side of the through hole, depositing a back electrode material on the piezoelectric film on the other side of the through hole and in the through hole, continuously depositing the back electrode material on the piezoelectric film on the other side of the through hole and in the through hole, leading the back electrode out through the through hole, and leading the back electrode to the surface of the piezoelectric film.
The through holes are formed by photoetching through hole patterns on the piezoelectric film and then etching.
The substrate is made of silicon, sapphire, SiC and the like, and the piezoelectric film is made of AlN, ZnO, lead zirconate titanate and the like.
The top electrode is spaced from the back electrode material. And intervals are arranged between the top electrode and the back electrode material in the through hole and on the surface of the piezoelectric film.
The back electrode leading-out method in the film bulk acoustic resonator specifically comprises the following steps:
(1) sequentially depositing a back electrode and a piezoelectric film on a substrate with a groove on the surface to obtain the piezoelectric film/the back electrode/the substrate;
(2) preprocessing the piezoelectric film/the back electrode/the substrate to remove impurities on the surface of the piezoelectric film;
(3) photoetching and etching the pretreated piezoelectric film to obtain a through hole on the piezoelectric film; the photoetching photoresist is a positive photoresist;
(4) cleaning the piezoelectric film/back electrode/substrate etched with the through holes to remove impurities; and then evaporating a top electrode material on the piezoelectric film on one side of the through hole by an electron beam evaporation coating method, evaporating a back electrode material in the through hole and on the piezoelectric film on the other side of the through hole by the electron beam evaporation coating method, and leading the back electrode to the surface of the piezoelectric film through the through hole.
The specific steps of the step (3) are as follows:
forming a bottom film (tackifying layer) on the surface of the piezoelectric film in a gas phase manner, spin-coating positive photoresist, drying, exposing through a mask plate with a through hole pattern, soaking in a developing solution, and etching according to the through hole pattern to obtain the through hole. The exposure conditions are 300-340W exposure power and 3-5s exposure. The soaking time of the developing solution is 40-60 s.
The deposition method in the step (1) is a conventional deposition method, such as MOCVD, PLD and other deposition methods;
the pretreatment in the step (1) refers to ultrasonic treatment by acetone, then cleaning by ethanol and water in sequence, and then cleaning by H2SO4、H2O2And H2Prepared from OSoaking in HF solution, washing with water, and oven drying.
The washing in the step (4) is to soak the fabric in hydrochloric acid and wash the fabric with water.
The top electrode material and the back electrode material in the step (4) are independently metals such as Ti, Pt, Al, Au and the like which are suitable for deposition by an electron beam evaporation method.
The film bulk acoustic resonator comprises a substrate, wherein a back electrode and a piezoelectric layer are sequentially arranged on the substrate, a groove is formed in the surface of the substrate, an air cavity is formed by the back electrode and the groove in the surface of the substrate, the piezoelectric layer is provided with a through hole, the back electrode is arranged below the through hole, a top electrode is arranged on the piezoelectric layer on one side of the through hole, and back electrode materials are arranged on the other side of the through hole and in the through hole. A space is provided between the top electrode and the back electrode material.
According to the invention, the piezoelectric film is coated with photoresist for photoetching, then the through hole is etched, and then the electrode material is evaporated on the piezoelectric layer through electron beam evaporation, so that the back electrode under the piezoelectric layer can be led to the upper surface of the piezoelectric layer through the through hole. From the process perspective, the complex process of depositing the top electrode to the table top of the back electrode after etching the AlN film layer is improved, and the problem of poor coverage of a metal step possibly existing can be avoided by utilizing the metal through hole. And moreover, the back electrode is led out through the through hole, the length of an electrode wire can be shortened, the size and parasitic parameters of the device are reduced, the power consumption is reduced, the performance of the device is improved, and the method is suitable for manufacturing the radio frequency filter in high-frequency and high-power occasions.
Compared with the traditional process for depositing the top electrode, the method has the following advantages and beneficial effects:
1. the invention avoids etching the piezoelectric film (such as AlN) in large area, and has less damage to the film;
2. the step coverage of the traditional process is poor, and the electrode is easy to cover through the through hole leading-out electrode;
3. the invention can shorten the length of the electrode wire, reduce the size of the device, reduce the power consumption and improve the performance;
4. the invention has high reliability of thermal expansion and small parasitic parameter in the actual process.
Drawings
FIG. 1 is a schematic structural diagram of a film bulk acoustic resonator prepared by the present invention (b) and a conventional process (a);
FIG. 2 is an SEM image (top view) of a through hole on a piezoelectric film before metal materials are evaporated; (a) an SEM photograph of a through hole etched in the piezoelectric film AlN of example 1, and (b) an SEM photograph of a through hole etched in the piezoelectric film AlN of example 2;
FIG. 3 is a graph of the energy spectrum of the through holes of examples 1 and 2 after evaporation of the electrodes; (a) sem and thermogram (1500 x) of example 1 (b) sem and thermogram (1500 x) of example 2;
fig. 4 is a bias-capacitance curve and a bias-loss tangent curve of the thin film bulk acoustic resonator in examples 1 and 2;
fig. 5 is a graph showing frequency-capacitance and frequency-loss tangent curves of the thin film bulk acoustic resonators in example 1 and example 2.
Detailed Description
The present invention will be described in further detail with reference to examples and drawings, but the present invention is not limited thereto.
Fig. 1 shows a schematic structural diagram of a film bulk acoustic resonator prepared by the present invention and a conventional process, where a is the film bulk acoustic resonator prepared by the conventional process, and b is the film bulk acoustic resonator prepared by the present invention.
The film bulk acoustic resonator prepared by the traditional process comprises a substrate 1, wherein a sacrificial layer 2 and a back electrode 3 are sequentially arranged on the substrate, a groove is formed in the surface of the sacrificial layer, an air cavity is formed by the back electrode and the groove in the surface of the sacrificial layer, the back electrode does not completely cover the sacrificial layer, a piezoelectric layer 4 is arranged on the back electrode and the sacrificial layer which is not covered by the back electrode, the piezoelectric layer does not completely cover the sacrificial layer, and a top electrode 5 is arranged on the piezoelectric layer and the sacrificial layer which is not covered by the piezoelectric layer.
The film bulk acoustic resonator comprises a substrate 1, wherein a back electrode 2 and a piezoelectric layer 3 are sequentially arranged on the substrate, a groove is formed in the surface of the substrate, an air cavity is formed by the back electrode and the groove in the surface of the substrate, the piezoelectric layer is provided with a through hole 5, the back electrode is arranged below the through hole, a top electrode 4 is arranged on the piezoelectric layer on one side of the through hole, and back electrode materials are arranged on the other side of the through hole and in the through hole. A space is provided between the top electrode and the back electrode material. And intervals are arranged between the top electrode and the back electrode material in the through hole and on the surface of the piezoelectric film.
Example 1
The film bulk acoustic resonator comprises a substrate Si, wherein a back electrode Ti and a piezoelectric layer AlN are sequentially arranged on the Si substrate, a groove is formed in the surface of the substrate, an air cavity is formed by the back electrode and the groove in the surface of the substrate, a through hole is formed in the piezoelectric layer AlN, the back electrode is arranged below the through hole, a top electrode Ti is arranged on the piezoelectric layer AlN on one side of the through hole, and a back electrode material Ti is arranged on the other side of the through hole and in the through hole. A space is provided between the top electrode and the back electrode material. The substrate thickness is 430 μm, the back electrode thickness is 100nm, the piezoelectric layer thickness is 1.5 μm, the top electrode thickness is 100nm, and the back electrode material thickness on the piezoelectric layer surface is 100 nm.
The extraction of the back electrode in the film bulk acoustic resonator comprises the following steps:
(1) sequentially depositing (MOCVD, PLD and other methods) back electrode Ti and piezoelectric film AlN on the Si substrate to obtain AlN/Ti/Si;
(2) cleaning an AlN/Ti/Si film: firstly, performing ultrasonic treatment on the mixture for 5min by using acetone at 40kHz, and respectively cleaning the mixture by using ethanol and water to remove organic pollutants on the surface; then using the solution (H) prepared at 40 DEG C2SO4(concentration 98%): h2O2(concentration 35%): h2O volume ratio 1:3:3) wash sample for 10min, HF solution (HF (40%): h2O volume ratio of 1:10) washing the sample for 10min, washing with water, removing inorganic pollutants on the surface, and drying;
(3) photoetching of the through hole: putting the pretreated AlN/Ti/Si into an HMDS oven for inflation to form an HMDS tackifying layer on the surface of the AlN; spin-coating RJZ-304 type positive photoresist, and baking at 100 deg.C for 100s to remove part of water; passing through a mask plate with a through hole pattern, and then exposing (300- & ltSP & gt 340- & ltSP & gt exposure power, exposure for 3-5 s); soaking in TMAH developer for 60s, and checking whether the line width of the pattern is qualified; then, introducing 60sccm oxygen plasma into the photoetched piezoelectric film in an inductively coupled plasma etching machine, and treating for 300s under the power of 80W to remove residual glue;
(4) etching the through hole:
etching the piezoelectric film with the residual photoresist removed according to a pattern formed by the photoresist (the smoothness of etching, the damage to AlN and the conflict between high-selectivity etching are comprehensively considered for etching through hole patterns), and setting the process parameters of the inductively coupled plasma etching machine: the pressure of the reaction chamber is 4mTorr, the power of the upper electrode and the lower electrode is 330W/180W respectively, the etching gas is 100sccmCl2/30 sccmcbcl 3, the flow rate of the tray He is 4Torr, the temperature of the base plate is 0 ℃, the SEM photograph of the piezoelectric film etched through holes is shown in (a) in figure 2, and the diameter of the through holes is 50 μm;
(5) cleaning before vapor deposition:
the requirement of the evaporation process on the cleanness degree of the surface of the substrate is very high, and the uneven or dirty surface can cause the falling-off of the metal film; before vapor deposition, the volume ratio of AlN/Ti/Si etched out of the through hole is HCl (37%): h2Cleaning with 1:1 hydrochloric acid solution for 10min, and drying by flushing water;
(6) fixing the cleaned AlN/Ti/Si etched with the through hole on a sample table, putting the sample table into a vacuum chamber, roughly pumping the sample to a vacuum degree of 10 < -2 > Pa, starting a molecular pump to pump the sample to a vacuum degree of less than 10 < -4 > Pa, and starting an electron beam switch to prepare for starting film coating; after the speed displayed on the crystal oscillator film thickness instrument is stable, opening a baffle, bombarding the target by using a high-energy electron beam, evaporating metal Ti of the target, and condensing the electrode material after the electrode material is transported to the surface of the film in vacuum to evaporate the electrode film; during the period, the data displayed by the film thickness meter is observed, the beam power and the beam spot position are controlled, and the evaporation rate is set to be
The compactness and the evaporation efficiency of the electrode film are balanced, the energy spectrum analysis of the metal film is shown in figure 3 (figure 3 is an energy spectrum diagram after the electrode is evaporated in the through hole), and the uniform distribution of Ti inside and outside the through hole and on the side wall can be seen.
The film bulk acoustic resonator prepared in this example was fixed to a jig for impedance testing. The method comprises the steps of carrying out resistivity test by using a SZT-2A four-probe resistance meter, carrying out electrical performance test under different bias voltages and electrical performance test under different frequency sweeps by using an Agilent 4294A impedance analyzer, wherein the resistivity of a film (film bulk acoustic resonator) is 47.36k omega/cm. The electrical property test under different bias voltages reflects the static electrical properties of the film under direct current excitation, including the dielectric constant and the loss tangent of the film, the fixed scanning frequency is 10kHz, and the bias voltage is set to scan from-3V to 3V. As shown in fig. 4 (fig. 4 shows a bias-capacitance curve and a bias-loss tangent curve of the film bulk acoustic resonator), the change of the dc bias hardly affects the magnitude of the static capacitance of the film. C is 1.07pF, and r is 2.46 calculated from the capacitance calculation formula C r 0S/d. Although the piezoelectric material will change in thickness under an applied dc bias, resulting in a change in the capacitance of the film. But there is little effect here, probably because the presence of the Si substrate releases the thickness variation of the piezoelectric thin film AlN.
The electrical performance test under different frequency sweeps reflects that the dielectric constant and the loss tangent of the film under the excitation of alternating current are the frequency corresponding characteristics of the film, the fixed bias voltage is 1V, and the scanning frequency is from 1 kHz to 1000 kHz. As shown in fig. 5 (fig. 5 is a frequency-capacitance and frequency-loss tangent curve of the film bulk acoustic resonator), the dielectric loss is dominated by the conductance loss at low frequencies. As the frequency of the alternating electric field increases, a change in the polarization retardation electrode begins to occur and the sample dielectric properties become more consistent with the piezoelectric material.
Example 2
The film bulk acoustic resonator comprises a substrate Si, wherein a back electrode Ti and a piezoelectric layer AlN are sequentially arranged on the Si substrate, a groove is formed in the surface of the substrate, an air cavity is formed by the back electrode and the groove in the surface of the substrate, a through hole is formed in the piezoelectric layer AlN, the back electrode is arranged below the through hole, a top electrode Ti is arranged on the piezoelectric layer AlN on one side of the through hole, and a back electrode material Ti is arranged on the other side of the through hole and in the through hole. A space is provided between the top electrode and the back electrode material. The substrate thickness is 430 μm, the back electrode thickness is 100nm, the piezoelectric layer thickness is 1.5 μm, the top electrode thickness is 100nm, and the back electrode material thickness on the piezoelectric layer surface is 100 nm.
The extraction of the back electrode in the film bulk acoustic resonator comprises the following steps:
(1) sequentially depositing (MOCVD, PLD and other methods) back electrode Ti and piezoelectric film AlN on the Si substrate to obtain AlN/Ti/Si;
(2) cleaning an AlN/Ti/Si film: firstly, performing ultrasonic treatment on the mixture for 5min by using acetone at 40kHz, and respectively cleaning the mixture by using ethanol and water to remove organic pollutants on the surface; then using the solution (H) prepared at 40 DEG C2SO4(concentration 98%): h2O2(concentration 35%): h2O volume ratio 1:3:3) wash sample for 10min, HF solution (HF (40%): h2O volume ratio of 1:10) washing the sample for 10min, washing with water, removing inorganic pollutants on the surface, and drying;
(3) photoetching of the through hole: putting the pretreated AlN/Ti/Si into an HMDS oven for inflation to form an HMDS tackifying layer on the surface of the AlN; spin-coating RJZ-304 type positive photoresist, and baking at 100 deg.C for 100s to remove part of water; passing through a mask plate with a through hole pattern, and then exposing (300- & ltSP & gt 340- & ltSP & gt exposure power, exposure for 3-5 s); soaking in TMAH developer for 60s, and checking whether the line width of the pattern is qualified; then, introducing 60sccm oxygen plasma into the photoetched piezoelectric film in an inductively coupled plasma etching machine, and treating for 300s under the power of 80W to remove residual glue;
(4) etching the through hole:
etching the piezoelectric film with the residual photoresist removed according to a pattern formed by the photoresist (the smoothness of etching, the damage to AlN and the conflict between high-selectivity etching are comprehensively considered for etching through hole patterns), and setting the process parameters of the inductively coupled plasma etching machine: the pressure of the reaction chamber is 4mTorr, the power of the upper electrode and the lower electrode is 330W/180W respectively, the etching gas is 100sccm Cl2/30sccm BCl3, the flow rate of the dilution gas Ar is 20sccm, the flow rate of the tray He is 4Torr, the temperature of the chassis is 0 ℃, the SEM photograph of the piezoelectric film etched through hole is shown in (b) in figure 2, and the diameter of the through hole is 50 μm;
(5) cleaning before vapor deposition:
the requirement of the evaporation process on the cleanness of the substrate surface is very high, and the uneven or dirty surface can cause the falling-off of the metal film(ii) a Before vapor deposition, the volume ratio of AlN/Ti/Si etched out of the through hole is HCl (37%): h2Cleaning with 1:1 hydrochloric acid solution for 10min, and drying by flushing water;
(6) fixing the cleaned AlN/Ti/Si etched with the through hole on a sample table, putting the sample table into a vacuum chamber, roughly pumping the sample to a vacuum degree of 10 < -2 > Pa, starting a molecular pump to pump the sample to a vacuum degree of less than 10 < -4 > Pa, and starting an electron beam switch to prepare for starting film coating; after the speed displayed on the crystal oscillator film thickness instrument is stable, opening a baffle, bombarding the target by using a high-energy electron beam, evaporating metal Ti of the target, and condensing the electrode material after the electrode material is transported to the surface of the film in vacuum to evaporate the electrode film; during the period, the data displayed by the film thickness meter is observed, the beam power and the beam spot position are controlled, and the evaporation rate is set to be
The compactness and the evaporation efficiency of the electrode film are balanced, the energy spectrum analysis of the metal film is shown in figure 3 (figure 3 is an energy spectrum diagram after the electrode is evaporated in the through hole), and the uniform distribution of Ti inside and outside the through hole and on the side wall can be seen.
The film bulk acoustic resonator prepared in this example was fixed to a jig for impedance testing. The method comprises the following steps of carrying out resistivity test by using a SZT-2A four-probe resistance meter, carrying out electrical performance test under different bias voltages and electrical performance test under different frequency sweeps by using an Agilent 4294A impedance analyzer, and obtaining the film with the resistivity of 47.36k omega/cm. The electrical property test under different bias voltages reflects the static electrical properties of the film under direct current excitation, including the dielectric constant and the loss tangent of the film, the fixed scanning frequency is 10kHz, and the bias voltage is set to scan from-3V to 3V. As shown in fig. 4 (fig. 4 shows a bias-capacitance curve and a bias-loss tangent curve of the film bulk acoustic resonator), the change of the dc bias hardly affects the magnitude of the static capacitance of the film. C is 1.13pF, and r is 3.10 according to the capacitance calculation formula C r 0S/d. Although the piezoelectric material will change in thickness under an applied dc bias, resulting in a change in the capacitance of the film. But there is little effect here, probably because the presence of the Si substrate releases the thickness variation of the piezoelectric thin film AlN.
The electrical performance test under different frequency sweeps reflects that the dielectric constant and the loss tangent of the film under the excitation of alternating current are the frequency corresponding characteristics of the film, the fixed bias voltage is 1V, and the scanning frequency is from 1 kHz to 1000 kHz. As shown in fig. 5 (fig. 5 is a frequency-capacitance and frequency-loss tangent curve of the film bulk acoustic resonator), the dielectric loss is dominated by the conductance loss at low frequencies. As the frequency of the alternating electric field increases, a change in the polarization retardation electrode begins to occur and the sample dielectric properties become more consistent with the piezoelectric material.
The conditions in the etching process of the invention are as follows: and setting technological parameters such as the pressure (7-10mTorr) of the reaction chamber of the inductively coupled plasma etching machine, the power (50-400W) of an upper electrode and a lower electrode, the flow rate (50-200 sccm) of etching gas and diluent gas, the flow rate (4-8sccm) of tray He and the like.
The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.
Claims (7)
1. A back electrode leading-out method in a film bulk acoustic resonator is characterized in that: the method comprises the following steps:
sequentially depositing a back electrode and a piezoelectric film on a substrate with a groove on the surface, forming an air cavity by the back electrode and the groove on the surface of the substrate, then preparing a through hole on the piezoelectric film, wherein the back electrode is arranged below the through hole, a top electrode is deposited on the piezoelectric film on one side of the through hole, a back electrode material is deposited on the piezoelectric film on the other side of the through hole and in the through hole, the back electrode material on the piezoelectric film on the other side of the through hole and in the through hole is continuously deposited, and the back electrode is led out through the through hole and led to the surface of the piezoelectric film;
the top electrode is spaced from the back electrode material;
the film bulk acoustic resonator comprises a substrate, wherein a back electrode and a piezoelectric layer are sequentially arranged on the substrate, a groove is formed in the surface of the substrate, an air cavity is formed by the back electrode and the groove in the surface of the substrate, the piezoelectric layer is provided with a through hole, the back electrode is arranged below the through hole, a top electrode is arranged on the piezoelectric layer on one side of the through hole, and back electrode materials are arranged on the other side of the through hole and in the through hole; a space is provided between the top electrode and the back electrode material.
2. The method for extracting a back electrode from a film bulk acoustic resonator according to claim 1, comprising:
the through holes are formed by photoetching through hole patterns on the piezoelectric film and then etching.
3. The method for extracting a back electrode from a film bulk acoustic resonator according to claim 1, comprising: the method specifically comprises the following steps:
(1) sequentially depositing a back electrode and a piezoelectric film on a substrate with a groove on the surface to obtain the piezoelectric film/the back electrode/the substrate;
(2) preprocessing the piezoelectric film/the back electrode/the substrate to remove impurities on the surface of the piezoelectric film;
(3) photoetching and etching the pretreated piezoelectric film to obtain a through hole on the piezoelectric film; the photoetching photoresist is a positive photoresist;
(4) cleaning the piezoelectric film/back electrode/substrate etched with the through holes to remove impurities; and then evaporating a top electrode material on the piezoelectric film on one side of the through hole by an electron beam evaporation coating method, evaporating a back electrode material in the through hole and on the piezoelectric film on the other side of the through hole by the electron beam evaporation coating method, and leading the back electrode to the surface of the piezoelectric film through the through hole.
4. The method of claim 3, wherein the back electrode is extracted from the film bulk acoustic resonator by: the specific steps of the step (3) are as follows:
forming a bottom film on the surface of the piezoelectric film in a gas phase manner, spin-coating positive photoresist, drying, exposing through a mask with a through hole pattern, soaking in a developing solution, and etching according to the through hole pattern to obtain the through hole.
5. The method for extracting a back electrode from a film bulk acoustic resonator according to claim 4, wherein: the exposure condition is 300-340W exposure power, and the exposure time is 3-5 s; the soaking time of the developing solution is 40-60 s.
6. The method of claim 3, wherein the back electrode is extracted from the film bulk acoustic resonator by: the pretreatment in the step (1) refers to ultrasonic treatment by acetone, then cleaning by ethanol and water in sequence, and then cleaning by H2SO4、H2O2And H2Soaking the solution prepared by O, soaking the solution by using HF solution, washing the solution by using water and drying the solution.
7. The method of claim 3, wherein the back electrode is extracted from the film bulk acoustic resonator by: the washing in the step (4) is to soak the fabric in hydrochloric acid and wash the fabric with water.
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