CN109756203A - A kind of FBAR resonance frequency and each thickness degree corresponding relationship method for building up of oscillating membrane - Google Patents
A kind of FBAR resonance frequency and each thickness degree corresponding relationship method for building up of oscillating membrane Download PDFInfo
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Abstract
The invention discloses a kind of FBAR resonance frequencies and each thickness degree corresponding relationship method for building up of oscillating membrane, for providing the requirement frequency of application, the thickness of set layers of material with alliteration mirror surface FBAR, and the thickness of each oscillating membrane layer material known, working frequency are also determining.The present invention is established by the thickness corresponding relationship of resonance frequency and oscillating membrane layers of material to FBAR, makes the two that can carry out mutually deriving prediction.In the design of FBAR, to determining frequency, and each oscillating layer film thickness is predicted, and to determining each oscillating layer film thickness, and resonance frequency is predicted, it is simple to provide one kind, quickly and effectively method, research and development and manufacturing schedule can be accelerated.
Description
Technical field
The present invention relates to radio-frequency techniques and FBAR wave filter technology field, and in particular to a kind of FBAR resonance frequency and oscillation
Each thickness degree corresponding relationship method for building up of film.
Background technique
To meet more communication functions and better communication experiences, modern communication technology needs to meet higher efficiency sum aggregate
At the requirement of change.By the filter of FBAR cascade construction, there is high q-factor, filter with low insertion loss, squareness factor is good, and direction selection is good, tool
Have good zero deeply, the advantage in Out-of-band rejection is good etc. performance, moreover, it is small in size, with COMS process compatible, it can do and collect
At.In addition, working frequency can accomplish high frequency, therefore, by the filter of FBAR cascade construction, can be good at meeting modern
The these requirements of the communication technology.
FBAR (film bulk acoustic resonator, membrane well acoustic resonance) is with piezoelectric effect material and energy
Enough components constructed for forming (inverse) piezoelectric effect structure.Using silicon base plate, by MEMS technology and thin film technique and
It manufactures.The working principle of FBAR is, in the core that electrode-piezoelectric material-electrode composition " sandwich " structure is constituted
In part, by electrode apply voltage, piezoelectric material generate deformation, and when application be alternating voltage when, structure meeting at this time
Generate inverse piezoelectric effect.During this, electric energy is converted to mechanical energy, is propagated in the structure by sound wave, and is causing to vibrate
While, vibration can also generate electric signal, i.e., by piezoelectric effect, mechanical energy is converted to electric energy, signal output comes.Piezoelectricity effect
It should exist simultaneously, interact, and resonance can be generated in the process of interaction, thus signal behavior with inverse piezoelectric effect
Out.
Currently, be directed to FBAR filter research and design and manufacture, there is no good method go carry out resonance frequency and
Each layer film thickness prediction, thus Theoretical Design needs obtained by other multiple types of tools and method as a result, and on the other hand,
Causing again cannot be by studying the good FBAR filter of current detection performance, and further progress verifying and guides new
FBAR filter designs and manufactures.
Summary of the invention
Aiming at the problems existing in the prior art, the embodiment of the present invention provides a kind of FBAR resonance frequency and oscillating membrane is each
Thickness degree corresponding relationship method for building up, it is known that each thickness degree of FBAR oscillating membrane, the foundation of respective resonant frequencies relationship.It can lead to
Each each thickness degree of FBAR in acquisition FBAR filter is crossed, to predict the resonance frequency of FBAR, and obtains the work of FBAR filter
Working frequency.It is good to detecting by being compared the FBAR resonance frequency of prediction with actual resonance frequency to realize
The research of FBAR filter provides comparison of design parameter for further design FBAR filter, so that guidance is to FBAR filter
Design and manufacture.
The embodiment of the present invention provides a kind of FBAR resonance frequency and each thickness degree corresponding relationship method for building up of oscillating membrane,
Know each thickness degree of FBAR oscillating membrane, the foundation of respective resonant frequencies relationship, comprising the following steps:
According to FBAR ideal piezoelectric layer condition of resonance, the ideal piezoelectric layer of foundation is associated with mould with FBAR parallel resonance frequency
Type；
According to the corresponding relationship of electromechanical coupling factor and FBAR resonance frequency, electromechanical coupling factor and FBAR resonance frequency are established
The correlation model of rate；
For each of FBAR filter FBAR, the thickness of every layer of structure is obtained, every layer of structure includes at least
Piezoelectric layer, upper electrode layer and lower electrode layer；
The thickness for the every layer of structure that will acquire is converted into ideal piezoelectric layer thickness, and it is in parallel with FBAR humorous to substitute into ideal piezoelectric layer
The correlation model of vibration frequency obtains FBAR parallel resonance frequency；
The electromechanical coupling factor for obtaining piezoelectric layer material therefor, by the mechanical-electric coupling of the piezoelectric layer material therefor acquired
Coefficient and FBAR parallel resonance frequency substitute into the correlation model of electromechanical coupling factor and FBAR resonance frequency, and it is humorous to obtain FBAR series connection
Vibration frequency.
Preferably, it after getting FBAR parallel resonance frequency and series resonance frequency, further comprises the steps of: described in acquisition
The working frequency of FBAR filter.
A kind of FBAR resonance frequency provided in an embodiment of the present invention and each thickness degree corresponding relationship method for building up of oscillating membrane,
Known each thickness degree of FBAR oscillating membrane, the foundation of respective resonant frequencies relationship.Pass through each layer of FBAR in measurement FBAR filter
Thickness predict the resonance frequency of FBAR, and then calculate the working frequency of FBAR filter.Pass through the FBAR resonance that will be predicted
Frequency is compared to realize the research to good FBAR filter is detected with actual resonance frequency, for further design
FBAR filter provides comparison of design parameter, so that guidance designs and manufactures FBAR filter.To determining layers of material
Thickness, can predict resonance frequency, be generally used for carrying out prepared device performance prediction, and to next step analysis or
Adjustment provides reference.Or according to specific process conditions, determine the thickness of layers of material, the performance of device is predicted.
The embodiment of the present invention provides a kind of FBAR resonance frequency and each thickness degree corresponding relationship method for building up of oscillating membrane,
Know FBAR resonance frequency, the foundation of corresponding each layer thickness relationship of oscillating membrane, comprising the following steps:
According to FBAR ideal piezoelectric layer condition of resonance, the ideal piezoelectric layer of foundation is associated with mould with FBAR parallel resonance frequency
Type；
According to the corresponding relationship of electromechanical coupling factor and FBAR resonance frequency, electromechanical coupling factor and FBAR resonance frequency are established
The correlation model of rate；
The working frequency for obtaining FBAR filter, the work of FBAR filter is determined according to the working frequency of FBAR filter
Frequency range, and according to the working frequency range and FBAR cascade construction principle, determine each FBAR parallel resonance frequency in FBAR filter
Rate and FBAR series resonance frequency；
It is in parallel with FBAR humorous to substitute into ideal piezoelectric layer for the FBAR parallel resonance frequency and FBAR series resonance frequency that will acquire
The correlation model of vibration frequency obtains ideal piezoelectric layer thickness；
According to practical piezoelectric layer thickness ratio, practical piezoelectric layer thickness is determined；
The FBAR parallel resonance frequency and FBAR series resonance frequency that will acquire substitute into electromechanical coupling factor and FBAR resonance
The correlation model of frequency obtains the electromechanical coupling factor of piezoelectric material, and according to the electromechanical coupling factor, determines piezoresistive material
Material；
By ideal piezoelectric layer thickness and the practical piezoelectric layer thickness determined, equivalent piezoelectric layer thickness is obtained；
By equivalent piezoelectric layer thickness, in conjunction with the material of other each layer choosings in addition to piezoelectric layer, it is obtained in addition to piezoelectric layer
His layers of material thickness, described other each layers in addition to piezoelectric layer include at least upper electrode layer and lower electrode layer.
A kind of FBAR resonance frequency and each thickness degree corresponding relationship method for building up of oscillating membrane that embodiment provides, feature
It is, it is known that FBAR resonance frequency, the foundation of corresponding each layer thickness relationship of oscillating membrane, by being filtered to FBAR of good performance
Device is detected, and the working frequency of FBAR filter is obtained, and by the working frequency, is calculated FBAR filter and respectively cascaded FBAR
Parallel resonance frequency and series resonance frequency, to predict the thickness of each FBAR layers of material in the FBAR filter.It obtains
To the thickness of FBAR layers of material can substitute into and carry out simulation study in FBAR simulation softwares, to be filtered with the FBAR
Device compares, and finds out optimization and design FBAR better method, or provides design parameter more particularly to FBAR design.
It to determining resonance frequency, is carrying out predicting in the thickness of layers of material, for determining the process of material layer one by one,
Used time has carried out the structure prediction to FBAR.The determination of every layer of material thickness be as a result, and for which layer needed, which layer is used
What material, then provides thickness, and the layer of structure of such device is also just apparent.
Preferably, according to FBAR ideal piezoelectric layer condition of resonance, ideal piezoelectric layer and FBAR parallel resonance frequency are established
Correlation model specifically includes:
By ideal piezoelectric layer condition of resonance formula:
Obtain ideal piezoelectric layer thickness:
It, θ is phase deviation angle, and k is wave number, 2HaFor ideal piezoelectric layer thickness, vaFor piezoelectric material longitudinal wave velocity, fpFor
FBAR parallel resonance frequency.
Ideal piezoelectric layer refers to the piezoelectricity nuclear structure constituted for basic electrode layer-piezoelectric layer-electrode layer, sound
Wave contacts one side with piezoelectric layer from electrode layer and reaches another surface by electrode layer and all reflect, and electrode layer is set as
It is unlimited thin, that is, there is electrode layer, but electrode layers thickness is ignored, such sound-wave path is limited in piezoelectric layer entirely.
Layers of material thickness, which can be regarded as, to be dispensed from ideal piezoelectric material thickness, the piezoelectric layer of same material,
It can directly subtract, but the thickness of different materials, be needed by setting up resonance frequency and layers of material thickness from this thickness
Relational expression, in this way, being equivalent to the thickness for carrying out different materials and corresponding calculating the piezoelectric material thickness conversion distributed.
Preferably, it according to the corresponding relationship of electromechanical coupling factor and FBAR parallel resonance frequency and series resonance frequency, builds
The correlation model of vertical electromechanical coupling factor and FBAR resonance frequency, specifically:
kt 2For electromechanical coupling factor, fsFor FBAR series resonance frequency.
Preferably, the thickness for the every layer of structure that will acquire is converted into ideal piezoelectric layer thickness, specifically: set up resonance frequency
The relationship of rate and layers of material thickness:
Or
Wherein
2Ha=2ha+2h1+2h2+......+2hn (6)
Wherein, 2hn(n=1,2,3 ...) is the thickness of the layers of material in addition to piezoelectric layer, vn(n=1,2,3 ...) is institute
Represent the longitudinal wave velocity of material, 2haFor piezoelectric layer actual (real) thickness.
Formula (4) and (5) are the applications to formula (2), wherein formula (4) is basisSound wave in each material
The time weight propagated in material is replaced in formula (2) by acquiring the equivalent rate propagated in entire oscillating membrane
va, and overall thickness can about be fallen in molecule and denominator, obtain formula (4).Formula (5) is to each material layer, it is assumed that wherein sound
Velocity of wave propagation is all va, then, equivalent, there are proportionate relationships for the speed ratio of the thickness of layers of material and material, and are building
In vertical relationship, there is effect spread distance that should regard layers of material actual (real) thickness as multiplied by scale factor.
Preferably, a kind of FBAR resonance frequency and each thickness degree corresponding relationship method for building up of oscillating membrane, it is known that FBAR is humorous
Vibration frequency, the foundation of corresponding each layer thickness relationship of oscillating membrane, according to following methods determine each FBAR parallel resonance frequency and
FBAR series resonance frequency:
According to the working frequency of the FBAR filter, by the working frequency range of FBAR filter, maximum twice FBAR's
The difference of resonance frequency determines the difference of the resonance frequency of FBAR；
For the FBAR, parallel resonance frequency f of connectingpFor FBAR filter passband most high frequency, series resonance frequency fsFor FBAR
Filter passband intermediate frequency；For FBAR in parallel, parallel resonance frequency fpFor FBAR filter passband intermediate frequency, series resonance frequency fs
For FBAR filter passband lowest frequency, so that it is determined that FBAR parallel resonance frequency fpWith series resonance frequency fs。
Preferably, equivalent piezoelectric layer thickness is that ideal piezoelectric layer thickness subtracts piezoelectric layer original depth；
Other layers of material thickness in addition to piezoelectric layer are obtained in conjunction with the material of each layer choosing by equivalent piezoelectric layer thickness,
Specifically:
Pass through formula
Or
Equivalent piezoelectric layer thickness is converted to the thickness of other each layers in addition to piezoelectric layer；Wherein, 2hn(n=1,2,3 ...)
The thickness of other layers of material, vn(n=1,2,3 ...) is the longitudinal wave velocity for representing other layers of material, and there are following relationships:
2Ha=2ha+2h1+2h2+......+2hn (4)
2haFor piezoelectric layer original depth.
Preferably for cascade FBAR filter, band bandwidth is 2 (fp-fs), frequency range fp±(fp-fs) or fs±
(fp-fs), frequency range is mainly selected in parallel or series by FBAR.As the parallel resonance frequency f for predicting FBARpAnd string
Join resonance frequency fs, the working frequency range and and working frequency of FBAR filter can be predicted.
It is concerned about frequency requirement, general indicator requires to be and to reflect to cascade construction filter FBAR filter
On FBAR, the considerations of being corresponding FBAR resonance frequency.According to most basic FBAR cascade (by the series connection parallel connection of a FBAR and one FBAR structure
At) principle of filter function is realized it is found that FBAR filter passband, the difference of two resonance frequencies of maximum twice FBAR (take
Just), then, for connect FBAR, fpFor filter passband most high frequency, fsFor filter passband intermediate frequency, and parallel connection FBAR, fpFor
Filter passband intermediate frequency, fsFor filter passband lowest frequency.In this way, by resonance frequency, it can be with the passband of predictive filter.
The method provided is embodied in the present invention, has the advantage that
1. a kind of FBAR resonance frequency and each thickness degree corresponding relationship method for building up of oscillating membrane, FBAR resonance frequency and
Layers of material thickness is associated by setting up relational expression, FBAR relevant parameter, and mutual interactively is quantized
It is intuitive to embody, directive function is provided to research and production.
2. reduce FBAR enters gate threshold, by the way that relevant parameter relationship is embodied by formula, facilitate analysis and
Research, simplifies analysis process, facilitates and speeds up and research and analyse to FBAR, and design and prepare.
3. FBAR resonance frequency prediction technique provided by the invention and each thickness degree prediction technique of FBAR, generally two sides
To, and it is unified into formula, then being all reversible for since any one direction.Two aspects can mutually turn
Change, there is important role in practical applications.
Detailed description of the invention
Fig. 1 is a kind of FBAR structural schematic diagram of the present invention；
Fig. 2 is each thickness degree of FBAR oscillating membrane known to the present invention, and the method for building up process of respective resonant frequencies relationship is shown
It is intended to；
Fig. 3 is FBAR resonance frequency known to the present invention, and the method for building up process of corresponding each layer thickness relationship of oscillating membrane is shown
It is intended to.
In attached drawing: 21, silicon substrate；22, cavity；23, supporting layer；24, lower electrode layer；25, piezoelectric layer；26, upper electrode layer；
27, cavity structure.
Specific embodiment
In the following, being described further in conjunction with attached drawing and specific embodiment to the present invention, it should be noted that not
Under the premise of conflicting, new implementation can be formed between various embodiments described below or between each technical characteristic in any combination
Example.
In FBAR resonance frequency prediction technique provided in an embodiment of the present invention and each thickness degree prediction technique of FBAR, FBAR's
Basic structure etches cavity 22, on silicon substrate 21 as shown in Figure 1, include silicon substrate 21 made of monocrystalline on silicon substrate 21
Supporting layer 23 is set, and cavity 22 is formed closed space with silicon substrate 21 by supporting layer 23 together.Electricity under being arranged on supporting layer
Pole layer 24, piezoelectric layer 25, upper electrode layer 26 is arranged on piezoelectric layer.26 layers of top electrode, piezoelectric layer 25 and lower electrode layer 24 form electricity
Pole-piezoelectric layer-electrode core layer.Particularly, it is provided with cavity structure 27 on upper electrode layer 26, i.e., has below core layer
Cavity 22, there is cavity structure 27 above core layer, and cavity 22 and cavity structure 27 constitute the fully reflecting surface of oscillation sound wave.Root
Some other layer can also be increased, strictly according to the facts between electrode-piezoelectric layer-electrode core layer according to other demands and process conditions
In the preparation of border, tuning layer can also be set on upper electrode layer 26, or do the protective layer that isolation air does protective effect.Lower electrode
Supporting layer 23 is also not necessarily required under layer 24, that is, electrode and piezoelectric layer is descended to be set up directly on silicon substrate 21, or can also be
Temperature compensation layer is arranged in the position of supporting layer.
Embodiment 1:
As shown in Fig. 2, each thickness degree of known FBAR oscillating membrane provided by the invention, the foundation of respective resonant frequencies relationship
Method includes the following steps:
S31: according to FBAR ideal piezoelectric layer condition of resonance, the ideal piezoelectric layer of foundation is associated with FBAR parallel resonance frequency
Model；
S32: according to the corresponding relationship of electromechanical coupling factor and FBAR resonance frequency, it is humorous with FBAR to establish electromechanical coupling factor
The correlation model of vibration frequency；
S33: for each of FBAR filter FBAR, the thickness of every layer of structure is obtained, every layer of structure is at least
Including piezoelectric layer 25, upper electrode layer 26 and lower electrode layer 24；Measuring instrument or other any measurable methods can be passed through
The thickness of every layer of structure is obtained, for example, some layers can be mentioned using standard component by measurement standard part or by official
The standard component thickness of confession obtains the thickness degree；
S34: the thickness for the every layer of structure that will acquire is converted into ideal piezoelectric layer thickness, substitutes into ideal piezoelectric layer and FBAR simultaneously
Join the correlation model of resonance frequency, obtains FBAR parallel resonance frequency；
S35: the electromechanical coupling factor of piezoelectric layer material therefor is obtained, by the electromechanics of the piezoelectric layer material therefor acquired
The coefficient of coup and FBAR parallel resonance frequency substitute into the correlation model of electromechanical coupling factor and FBAR resonance frequency, obtain FBAR string
Join resonance frequency.
Each thickness degree of known FBAR oscillating membrane provided in an embodiment of the present invention, the foundation side of respective resonant frequencies relationship
Method predicts the resonance frequency of FBAR by the thickness of each layer of FBAR in measurement FBAR filter, and then calculates FBAR filter
Working frequency.It is good to detecting by being compared the FBAR resonance frequency of prediction with actual resonance frequency to realize
FBAR filter research, for further design FBAR filter comparison of design parameter is provided, thus guidance to FBAR filter
Device designs and manufactures.
According to FBAR ideal piezoelectric layer condition of resonance, the ideal piezoelectric layer of foundation is associated with mould with FBAR parallel resonance frequency
Type specifically includes:
By ideal piezoelectric layer condition of resonance formula:
Obtain ideal piezoelectric layer thickness:
It, θ is phase deviation angle, and k is wave number, 2HaFor ideal piezoelectric layer thickness, vaFor piezoelectric material longitudinal wave velocity, fpFor
FBAR parallel resonance frequency.
According to the corresponding relationship of electromechanical coupling factor and FBAR parallel resonance frequency and series resonance frequency, electromechanical coupling is established
The correlation model of collaboration number and FBAR resonance frequency, specifically:
kt 2For electromechanical coupling factor, fsFor FBAR series resonance frequency.
The thickness for the every layer of structure that will acquire is converted into ideal piezoelectric layer thickness, specifically: set up resonance frequency and each
The relationship of layer material thickness:
Or
Wherein
2Ha=2ha+2h1+2h2+......+2hn (6)
Wherein, 2hn(n=1,2,3 ...) is the thickness of the layers of material in addition to piezoelectric layer, vn(n=1,2,3 ...) is institute
Represent the longitudinal wave velocity of material, 2haFor piezoelectric layer actual (real) thickness.
Come below with a specific embodiment to each thickness degree of known FBAR oscillating membrane of the invention, respective resonant frequencies
The method for building up of relationship is specifically described.
In FBAR structure as shown in Figure 1,21 material of silicon substrate is monocrystalline silicon, and supporting layer 23 is Si3N4, upper electrode layer 26
Upper and lower electrode layer 24 is Mo, and piezoelectric layer 25 is AlN, and obtaining supporting layer 23 by measuring instrument is Si3N4With a thickness of 160nm,
Lower electrode layer 24Mo with a thickness of 230nm, piezoelectric layer 25AlN with a thickness of 1200nm, upper electrode layer Mo with a thickness of 188nm.
By consulting handbook it is found that it is 6213m/s that longitudinal wave velocity, which is respectively as follows: Mo, AlN is 11350m/s, Si3N4's
For 11000m/s.
Known layers of material thickness can go out the resonance frequency of FBAR with recursion, further, i.e., filter work frequency
Rate.According to formula (4) or formula (5), parallel resonance frequency is calculated, followed by number between each parameter in formula (6)
Relationship between expression formula is learned, series resonance frequency is calculated.In this way, the resonance frequency of FBAR has obtained, then, thus FBAR is constituted
Filter passband bandwidth be 2 (fp-fs), frequency range fp±(fp-fs) or fs±(fp-fs), it is just derived by each thickness degree of FBAR
Frequency out.
Layers of material thickness and sound wave are substituted into formula (3) in the longitudinal wave velocity data that material is propagated, fp is calculated,
It is 2.67GHz that fp, which is calculated, in this embodiment.
Further, it is known that piezoelectric material electromechanical coupling factor is 0.058 in embodiment, according to formula (3), is calculated
Fs is 2.61GHz, and then it is found that if cascading filter, filter maximum pass-band is about 120MHz, then, operating frequency range
For 2.55GHz~2.79GHz or 2.49GHz~2.73GHz.
Embodiment 2:
As shown in figure 3, known FBAR resonance frequency provided by the invention, the foundation of corresponding each layer thickness relationship of oscillating membrane
Method includes the following steps:
S41: according to FBAR ideal piezoelectric layer condition of resonance, the ideal piezoelectric layer of foundation is associated with FBAR parallel resonance frequency
Model；
S42: according to the corresponding relationship of electromechanical coupling factor and FBAR resonance frequency, it is humorous with FBAR to establish electromechanical coupling factor
The correlation model of vibration frequency；
S43: the working frequency of FBAR filter is obtained, FBAR filter is determined according to the working frequency of FBAR filter
Working frequency range, and according to the working frequency range and FBAR cascade construction principle, determine that each FBAR parallel connection is humorous in FBAR filter
Vibration frequency and FBAR series resonance frequency；
S44: the FBAR parallel resonance frequency and FBAR series resonance frequency that will acquire substitute into ideal piezoelectric layer and FBAR simultaneously
Join the correlation model of resonance frequency, obtains ideal piezoelectric layer thickness；
S45: according to practical piezoelectric layer thickness ratio, compacting border electric layer thickness is determined；
S46: the FBAR parallel resonance frequency and FBAR series resonance frequency that will acquire substitute into electromechanical coupling factor and FBAR
The correlation model of resonance frequency obtains the electromechanical coupling factor of piezoelectric material, and according to the electromechanical coupling factor, determines piezoelectricity
Material；
S47: by ideal piezoelectric layer thickness and the practical piezoelectric layer thickness determined, equivalent piezoelectric layer thickness is obtained；
S48: it obtains in conjunction with the material of other each layer choosings in addition to piezoelectric layer by equivalent piezoelectric layer thickness and removes piezoelectric layer
Other outer layers of material thickness, described other each layers in addition to piezoelectric layer include at least upper electrode layer and lower electrode layer.
Known FBAR resonance frequency provided in an embodiment of the present invention, the foundation side of corresponding each layer thickness relationship of oscillating membrane
Method obtains the working frequency of FBAR filter, and pass through work frequency by detecting to FBAR filter of good performance
Rate calculates parallel resonance frequency and series resonance frequency that FBAR filter respectively cascades FBAR, from the prediction FBAR filter
The thickness of each FBAR layers of material.The thickness of the FBAR layers of material got can for substitute into FBAR simulation softwares in into
Row simulation study finds out optimization and design FBAR better method, or tool to compare with the FBAR filter
Body is related to FBAR and provides design parameter.
Preferably, according to FBAR ideal piezoelectric layer condition of resonance, ideal piezoelectric layer and FBAR parallel resonance frequency are established
Correlation model specifically includes:
By ideal piezoelectric layer condition of resonance formula:
Obtain ideal piezoelectric layer thickness:
It, θ is phase deviation angle, and k is wave number, 2HaFor ideal piezoelectric layer thickness, vaFor piezoelectric material longitudinal wave velocity, fpFor
FBAR parallel resonance frequency.
Ideal piezoelectric layer refers to the piezoelectricity nuclear structure constituted for basic electrode layer-piezoelectric layer-electrode layer, sound
Wave contacts one side with piezoelectric layer from electrode layer and reaches another surface by electrode layer and all reflect, and electrode layer is set as
It is unlimited thin, that is, there is electrode layer, but electrode layers thickness is ignored, such sound-wave path is limited in piezoelectric layer entirely.
Layers of material thickness, which can be regarded as, to be dispensed from ideal piezoelectric material thickness, the piezoelectric layer of same material,
It can directly subtract, but the thickness of different materials, be needed by setting up resonance frequency and layers of material thickness from this thickness
Relational expression, in this way, being equivalent to the thickness for carrying out different materials and corresponding calculating the piezoelectric material thickness conversion distributed.
Preferably, it according to the corresponding relationship of electromechanical coupling factor and FBAR parallel resonance frequency and series resonance frequency, builds
The correlation model of vertical electromechanical coupling factor and FBAR resonance frequency, specifically:
kt 2For electromechanical coupling factor, fsFor FBAR series resonance frequency.
Preferably, ideal piezoelectric layer thickness is converted into the thickness of every layer of structure, specifically: set up resonance frequency and each layer
The relationship of material thickness:
Or
Wherein
2Ha=2ha+2h1+2h2+......+2hn (6)
Wherein, 2hn(n=1,2,3 ...) is the thickness of the layers of material in addition to piezoelectric layer, vn(n=1,2,3 ...) is institute
Represent the longitudinal wave velocity of material, 2haFor piezoelectric layer actual (real) thickness.
Formula (4) and (5) are the applications to formula (2), wherein formula (4) is basisSound wave in each material
The time weight propagated in material is replaced in formula (2) by acquiring the equivalent rate propagated in entire oscillating membrane
va, and overall thickness can about be fallen in molecule and denominator, obtain formula (4).Formula (5) is to each material layer, it is assumed that wherein sound
Velocity of wave propagation is all va, then, equivalent, there are proportionate relationships for the speed ratio of the thickness of layers of material and material, and are building
In vertical relationship, there is effect spread distance that should regard layers of material actual (real) thickness as multiplied by scale factor.
Preferably, each FBAR parallel resonance frequency and FBAR series resonance frequency are determined according to following methods:
According to the working frequency of the FBAR filter, by the working frequency range of FBAR filter, maximum twice FBAR's
The difference of resonance frequency determines the difference of the resonance frequency of FBAR；
For the FBAR, parallel resonance frequency f of connectingpFor FBAR filter passband most high frequency, series resonance frequency fsFor FBAR
Filter passband intermediate frequency；For FBAR in parallel, parallel resonance frequency fpFor FBAR filter passband intermediate frequency, series resonance frequency fs
For FBAR filter passband lowest frequency, so that it is determined that FBAR parallel resonance frequency fpWith series resonance frequency fs。
Preferably, equivalent piezoelectric layer thickness is that ideal piezoelectric layer thickness subtracts piezoelectric layer original depth；
Preferably for cascade FBAR filter, band bandwidth is 2 (fp-fs), frequency range fp±(fp-fs) or fs±
(fp-fs), frequency range is mainly selected in parallel or series by FBAR.As the parallel resonance frequency f for predicting FBARpAnd string
Join resonance frequency fs, the working frequency range and and working frequency of FBAR filter can be predicted.
It is concerned about frequency requirement, general indicator requires to be and to reflect to cascade construction filter FBAR filter
On FBAR, the considerations of being corresponding FBAR resonance frequency.According to most basic FBAR cascade (by the series connection parallel connection of a FBAR and one FBAR structure
At) principle of filter function is realized it is found that FBAR filter passband, the difference of two resonance frequencies of maximum twice FBAR (take
Just), then, for connect FBAR, fpFor filter passband most high frequency, fsFor filter passband intermediate frequency, and parallel connection FBAR, fpFor
Filter passband intermediate frequency, fsFor filter passband lowest frequency.In this way, by resonance frequency, it can be with the passband of predictive filter.
Come below with a specific embodiment to known FBAR resonance frequency of the invention, corresponding each thickness degree of oscillating membrane
The method for building up of relationship is specifically described.
Measure operating frequency range 2300MHz~2400MHz of FBAR filter, Insertion Loss≤3dB, Out-of-band rejection >=
The principle of 30dB and FBAR cascade construction FBAR filter, determines the fundamental frequency f of resonatorp.It is first according to operating frequency range
First available, connect FBAR, parallel resonance frequency fps=2400MHz, series resonance frequency fss=2350MHz, it is in parallel
FBAR, parallel resonance frequency fpp=2350MHz, series resonance frequency fsp=2300MHz.
It is calculated according to formula (3)Here,According to the condition of ideal piezoelectric layer resonance, managed
Think the thickness of situation lower piezoelectric layer.By formula (3), ideal piezoelectric layer thickness is calculated, connect FBAR:2Hap=2.36um,
FBAR:2Haps=2.41um in parallel.
According to the considerations of structure and the considerations of thickness ratio, the thickness of piezoelectric layer is determined.Here, series connection FBAR piezoelectricity thickness
Spend 2hapFor 1.2um, FBAR piezoelectric layer thickness 2h in parallelasFor 1.2um.
Ideal piezoelectric layer thickness subtracts determining piezoelectric layer thickness, and remaining thickness is that electrode and other materials layer are equivalent
Piezoelectric layer thickness, it is therefore desirable to this thickness be converted into the thickness of electrode and other materials layer.Simplified processing is done to embodiment,
Layer structure only retains " sandwich " structure of core work, therefore in addition to AlN layers, remaining is exactly Mo layers of electrode.
And the equivalent AlN thickness degree of the FBAR that connects is 1.21um and 1.16um respectively, by formula (4) or (5), equivalent
AlN thickness degree is converted into electrode overall thickness, then has, shunt electrodes overall thickness 2h1s=659.56nm, electrode overall thickness of connecting
2h1p=659.39nm.
The above embodiment is only the preferred embodiment of the present invention, and the scope of protection of the present invention is not limited thereto,
The variation and replacement for any unsubstantiality that those skilled in the art is done on the basis of the present invention belong to institute of the present invention
Claimed range.
Claims (7)
1. a kind of FBAR resonance frequency and each thickness degree corresponding relationship method for building up of oscillating membrane, which is characterized in that known FBAR
Each thickness degree of oscillating membrane, the foundation of respective resonant frequencies relationship, comprising the following steps:
According to FBAR ideal piezoelectric layer condition of resonance, the correlation model of ideal piezoelectric layer and FBAR parallel resonance frequency is established；
According to the corresponding relationship of electromechanical coupling factor and FBAR resonance frequency, electromechanical coupling factor and FBAR resonance frequency are established
Correlation model；
For each of FBAR filter FBAR, the thickness of every layer of structure is obtained, every layer of structure includes at least piezoelectricity
Layer, upper electrode layer and lower electrode layer；
The thickness for the every layer of structure that will acquire is converted into ideal piezoelectric layer thickness, substitutes into ideal piezoelectric layer and FBAR parallel resonance frequency
The correlation model of rate obtains FBAR parallel resonance frequency；
The electromechanical coupling factor for obtaining piezoelectric layer material therefor, by the electromechanical coupling factor of the piezoelectric layer material therefor acquired
The correlation model of electromechanical coupling factor and FBAR resonance frequency is substituted into FBAR parallel resonance frequency, obtains FBAR series resonance frequency
Rate.
2. the method as described in claim 1, which is characterized in that getting FBAR parallel resonance frequency and series resonance frequency
Afterwards, the working frequency for obtaining the FBAR filter is further comprised the steps of:.
3. a kind of FBAR resonance frequency and each thickness degree corresponding relationship method for building up of oscillating membrane, which is characterized in that known FBAR
Resonance frequency, the foundation of corresponding each layer thickness relationship of oscillating membrane, comprising the following steps:
According to FBAR ideal piezoelectric layer condition of resonance, the correlation model of ideal piezoelectric layer and FBAR parallel resonance frequency is established；
According to the corresponding relationship of electromechanical coupling factor and FBAR resonance frequency, electromechanical coupling factor and FBAR resonance frequency are established
Correlation model；
The working frequency for obtaining FBAR filter determines the work frequency of FBAR filter according to the working frequency of FBAR filter
Section, and according to the working frequency range and FBAR cascade construction principle, determine each FBAR parallel resonance frequency in FBAR filter
With FBAR series resonance frequency；
The FBAR parallel resonance frequency and FBAR series resonance frequency that will acquire substitute into ideal piezoelectric layer and FBAR parallel resonance frequency
The correlation model of rate obtains ideal piezoelectric layer thickness；
According to practical piezoelectric layer thickness ratio, practical piezoelectric layer thickness is determined；
The FBAR parallel resonance frequency and FBAR series resonance frequency that will acquire substitute into electromechanical coupling factor and FBAR resonance frequency
Correlation model, obtain the electromechanical coupling factor of piezoelectric material, and according to the electromechanical coupling factor, determine piezoelectric material；
By ideal piezoelectric layer thickness and the practical piezoelectric layer thickness determined, equivalent piezoelectric layer thickness is obtained；
By equivalent piezoelectric layer thickness, in conjunction with the material of other each layer choosings in addition to piezoelectric layer, it is each to obtain in addition to piezoelectric layer other
Layer material thickness, described other each layers in addition to piezoelectric layer include at least upper electrode layer and lower electrode layer.
4. method as described in any one of claims 1 or 3, which is characterized in that according to FBAR ideal piezoelectric layer condition of resonance, establish
The correlation model of ideal piezoelectric layer and FBAR parallel resonance frequency, specifically includes:
By ideal piezoelectric layer condition of resonance formula:
Obtain ideal piezoelectric layer thickness:
Wherein, θ is phase deviation angle, and k is wave number, 2HaFor ideal piezoelectric layer thickness, vaFor piezoelectric material longitudinal wave velocity, fpFor FBAR
Parallel resonance frequency.
5. method as described in any one of claims 1 or 3, which is characterized in that according to electromechanical coupling factor and FBAR parallel resonance
The corresponding relationship of frequency and series resonance frequency establishes the correlation model of electromechanical coupling factor Yu FBAR resonance frequency, specifically:
kt 2For electromechanical coupling factor, fsFor FBAR series resonance frequency.
6. method as claimed in claim 1 or 3, which is characterized in that thickness and ideal piezoelectric layer thickness by every layer of structure
Relationship, it is established that the relationship of resonance frequency and layers of material thickness:
Or
Wherein
2Ha=2ha+2h1+2h2+......+2hn (6)
Wherein, 2hn(n=1,2,3 ...) is the thickness of the layers of material in addition to piezoelectric layer, vn(n=1,2,3 ...) is representative
The longitudinal wave velocity of material, 2haFor piezoelectric layer actual (real) thickness.
7. method as claimed in claim 3, which is characterized in that according to following methods determine each FBAR parallel resonance frequency and
FBAR series resonance frequency:
According to the working frequency of the FBAR filter, by the working frequency range of FBAR filter, the resonance of maximum twice FBAR
The difference of frequency determines the difference of the resonance frequency of FBAR；
For the FBAR, parallel resonance frequency f of connectingpFor FBAR filter passband most high frequency, series resonance frequency fsFor FBAR filtering
Device passband intermediate frequency；For FBAR in parallel, parallel resonance frequency fpFor FBAR filter passband intermediate frequency, series resonance frequency fsFor
FBAR filter passband lowest frequency, so that it is determined that FBAR parallel resonance frequency fpWith series resonance frequency fs。
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