CN102823007B - Piezoelectric thin-film element, process for producing same, and piezoelectric thin-film device - Google Patents
Piezoelectric thin-film element, process for producing same, and piezoelectric thin-film device Download PDFInfo
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- CN102823007B CN102823007B CN201080065779.5A CN201080065779A CN102823007B CN 102823007 B CN102823007 B CN 102823007B CN 201080065779 A CN201080065779 A CN 201080065779A CN 102823007 B CN102823007 B CN 102823007B
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- RKTYLMNFRDHKIL-UHFFFAOYSA-N copper;5,10,15,20-tetraphenylporphyrin-22,24-diide Chemical compound [Cu+2].C1=CC(C(=C2C=CC([N-]2)=C(C=2C=CC=CC=2)C=2C=CC(N=2)=C(C=2C=CC=CC=2)C2=CC=C3[N-]2)C=2C=CC=CC=2)=NC1=C3C1=CC=CC=C1 RKTYLMNFRDHKIL-UHFFFAOYSA-N 0.000 claims abstract 2
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
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- C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
- C23C14/06—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the coating material
- C23C14/08—Oxides
- C23C14/088—Oxides of the type ABO3 with A representing alkali, alkaline earth metal or Pb and B representing a refractory or rare earth metal
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- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B23/00—Single-crystal growth by condensing evaporated or sublimed materials
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- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
- C30B29/10—Inorganic compounds or compositions
- C30B29/16—Oxides
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- C30B29/30—Niobates; Vanadates; Tantalates
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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 elements; Electromechanical resonators
- H03H9/02—Details
- H03H9/02007—Details of bulk acoustic wave devices
- H03H9/02015—Characteristics of piezoelectric layers, e.g. cutting angles
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- H03H9/02543—Characteristics of substrate, e.g. cutting angles
- H03H9/02574—Characteristics of substrate, e.g. cutting angles of combined substrates, multilayered substrates, piezoelectrical layers on not-piezoelectrical substrate
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- H10N30/074—Forming of piezoelectric or electrostrictive parts or bodies on an electrical element or another base by depositing piezoelectric or electrostrictive layers, e.g. aerosol or screen printing
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- H03H9/15—Constructional features of resonators consisting of piezoelectric or electrostrictive material
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- H03H9/171—Constructional features of resonators consisting of piezoelectric or electrostrictive material having a single resonator implemented with thin-film techniques, i.e. of the film bulk acoustic resonator [FBAR] type
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Abstract
Disclosed is a piezoelectric thin-film element which comprises a substrate and, disposed thereon, at least a lower electrode, a piezoelectric thin film represented by the general formula (NaxKyLiz)NbO3 (0=x=1, 0=y=1, 0=z=0.2, and x+y+z=1), and an upper electrode, characterized in that the piezoelectric thin film has a crystal structure constituted of a quasi-cubic, tetragonal, or orthorhombic system or has a state in which at least one of those crystal systems is coexistent, that the crystal grains have been oriented preferentially along up to two specific crystallographic axes among those axes, and that with respect to the ratio between (001) components and (111) components, as the oriented crystallographic components, the proportion by volume of the (001) components is 60-100% and the proportion by volume of the (111) components is 0-40%, when the sum of both is taken as 100%.
Description
Technical field
The present invention relates to use piezoelectric thin film device and the piezoelectric membrane device of lithium potassium niobate sodium film etc.
Background technology
According to various objects, piezoelectrics are processed into various piezoelectric devices, are especially widely used as the functional electric subassembly that produces the driver of strain or produced the sensor of voltage by the strain of device by applying voltage.As the piezoelectrics for driver or transducer, being widely used so far the lead with excellent piezoelectric properties is dielectric, especially uses the Pb (Zr that is called as PZT
1-xti
x) O
3the Ferroelectrics of system, piezoelectrics are normally by forming the oxidesintering that contains various elements.In addition, in recent years because of the misgivings to environment, wish the lead-free piezoelectrics of exploitation, developing lithium potassium niobate sodium (general formula: (Na
xk
yli
z) NbO
3(0 < x < 1,0 < y < 1,0 < z < 1, x+y+z=1) (hereinafter referred to as LKNN) etc.Because this LKNN has the piezoelectric property matching in excellence or beauty in PZT, be therefore expected to the strong candidate as non-plumbous piezoelectric.In addition, LKNN comprises potassium-sodium niobate (KNN) film.
On the other hand,, along with the small-sized and high performance development of various electronic components, also require consumingly piezoelectric device miniaturization and high performance now.Yet it is following when thick that piezoelectric, especially its thickness of making by the manufacture method centered by the sintering process by method for making in the past reaches 10 μ m, close to the size of the crystal grain of constituent material, cannot ignore the impact of size.Thereby deviation or the deteriorated significant problem that becomes of characteristic have been there is.For fear of this problem, Recent study applied film technology etc. replace sintering process to form the method for piezoelectric membrane.
Recently, actual by the pzt thin film that uses RF sputtering method to form the gyro sensor (for example, with reference to patent documentation 1, non-patent literature 1) as driver or small-sized low price for fine high speed ink jet-print head.In addition, also propose to have the use piezoelectric thin film device of plumbous LKNN piezoelectric membrane (for example, with reference to patent documentation 2).
Prior art document
Patent documentation
Patent documentation 1: Japanese kokai publication hei 10-286953 communique
Patent documentation 2: TOHKEMY 2007-19302 communique
Non-patent literature
Non-patent literature 1: the high performance of the good chief editor's piezoelectric of middle village happy and forward position application technology (pressing Electricity material high performance と tip ying Ji Intraoperative) (Science & technology(サ イ エ Application ス & テ Network ノ ロ ジ ー) publication 2007)
Summary of the invention
the problem that invention will solve
By forming non-plumbous piezoelectric membrane as piezoelectric membrane, can bear the gyro sensor of shower nozzle or small-sized low price for little fine high speed ink-jet printer by production environment.As concrete candidate, carry out the basic research of the filming of LKNN.
Yet for example, in prior art (patent documentation 2), orientation of piezoelectric membrane etc. is not at length studied, cannot stably be realized the piezoelectric thin film device that can show high piezoelectric constant.
The object of the present invention is to provide piezoelectric thin film device and the piezoelectric membrane device of seeking to improve piezoelectric property.
for the scheme of dealing with problems
According to a kind of mode of the present invention, a kind of piezoelectric thin film device is provided, it at least disposing lower electrode, using general formula (Na on substrate
xk
yli
z) NbO
3(0≤x≤1, 0≤y≤1, 0≤z≤0.2, x+y+z=1) piezoelectric membrane representing, and the stacked body of the piezoelectric membrane of upper electrode, wherein, described piezoelectric membrane has accurate cubic crystal, regular crystal or orthorhombic crystal structure, or be at least one state coexisting in crystal structure described in these, some specific axis preferred orientation in their crystallographic axis below 2 axles, and the composition as the crystallographic axis of described orientation, in the ratio of (001) composition and (111) composition, with the two add up to 100% time, (001) volume fraction of composition is in the scope more than 60% and below 100%, (111) volume fraction of composition is in the scope more than 0% and below 40%.
Now, especially preferably the volume fraction of (001) composition is in the higher scope more than 70% and below 100% of degree of crystallinity, and the volume fraction of (111) composition is in the scope more than 0% and below 30%.
In addition, the state that described in described piezoelectric membrane is preferably, (001) composition and described (111) composition coexist, the volume fraction of (111) composition is more preferably greater than 1%.
In addition, preferred described piezoelectric membrane has the aggregate structure that the particle by column structure forms.
In addition, a part for described piezoelectric membrane also can contain ABO
3crystal layer, ABO
3amorphous layer or be mixed with ABO
3crystal and any in non-crystal mixed layer.
Wherein, A is the a kind of above element being selected from Li, Na, K, La, Sr, Nd, Ba and Bi, and B is the a kind of above element being selected from Zr, Ti, Mn, Mg, Nb, Sn, Sb, Ta and In, and O is oxygen.
In addition, described piezoelectric membrane can have strain in the direction parallel with real estate.
In addition, described strain can be the strain of tensile stress state in the direction parallel with real estate or the strain of compressing stress state.In addition, described piezoelectric membrane also can for do not have internal stress without strain regime.
In addition, described piezoelectric membrane also can have inhomogeneous strain in the direction vertical with real estate or parallel direction or two directions.
In addition, lower electrode layer is preferably Pt or take alloy that Pt is main component or comprise these and take the electrode layer of stepped construction of the electrode layer that Pt is main component.
In addition, as lower electrode layer, can be also comprise Ru, Ir, Sn, In and oxide thereof, with piezoelectric membrane in the electrode layer of stepped construction of layer of the compound that forms of contained element.
In addition, top electrode layer is Pt or the Pt of the take alloy that is main component or comprises these and take the electrode layer of stepped construction of the electrode layer that Pt is main component.
In addition, as top electrode layer, can be also comprise Ru, Ir, Sn, In and oxide thereof, with piezoelectric membrane in the electrode layer of stepped construction of electrode layer of the compound that forms of contained element.
In addition, as described lower electrode layer, relevant with its crystal orientation, be preferably at the individual layer of the orientation preferentially orientation vertical with substrate surface or the electrode layer of stepped construction.
In addition, described substrate can be for being selected from Si substrate, MgO substrate, zno-based plate, SrTiO
3substrate, SrRuO
31 kind of substrate in substrate, glass substrate, quartz glass substrate, GaAs substrate, GaN substrate, sapphire substrate, Ge substrate and stainless steel substrate.Particularly preferably described substrate is Si substrate.
According to alternate manner of the present invention, a kind of piezoelectric thin film device is provided, it for disposing with general formula (Na on substrate
xk
yli
z) NbO
3the stacked body of piezoelectric membrane of the piezoelectric membrane that (0≤x≤1,0≤y≤1,0≤z≤0.2, x+y+z=1) represents,
Wherein, described piezoelectric membrane has accurate cubic crystal, regular crystal or orthorhombic crystal structure, or be at least one state coexisting in crystal structure described in these, some specific axis preferred orientation in their crystallographic axis below 2 axles, (001) composition and (111) composition as the composition of the crystallographic axis of described preferred orientation are coexisting state, and in the ratio of (001) composition and (111) composition, with the two add up to 100% time, (001) volume fraction of composition is being greater than 60% and be less than in 100% scope, (111) volume fraction of composition is in being less than 40% scope.
In addition, between described substrate and described piezoelectric membrane, can there is basalis.Basalis can be used LaNiO
3, NaNbO
3, also can use the Pt film at (111) preferred orientation.
In addition, according to alternate manner of the present invention, provide the piezoelectric membrane device that possesses above-mentioned piezoelectric thin film device and voltage applying unit or voltage detection unit.
the effect of invention
Adopt the present invention, piezoelectric thin film device and the piezoelectric membrane device of piezoelectric property excellence can be provided.
Accompanying drawing explanation
Fig. 1 is the sectional view of the piezoelectric thin film device of the piezoelectric membrane of use embodiments of the invention 1.
Fig. 2 is for showing the figure of an example of the X-ray diffractogram that 2 θ/θ of the piezoelectric thin film device of embodiments of the invention 1 scans.
Fig. 3 is the figure of the crystal structure of the KNN piezoelectric membrane of demonstration embodiments of the invention 1.
Fig. 4 is the experimental configuration figure of the utmost point figure of the KNN piezoelectric membrane of mensuration embodiments of the invention 1.
Fig. 5 is the performance plot of the KNN piezoelectric membrane of embodiments of the invention 1, (a) for the measurement result of wide-angle reciprocal lattice mapping is routine, (b) for the simulation of wide-angle reciprocal lattice mapping is routine.
Fig. 6 is the performance plot of the KNN piezoelectric membrane (KNN-1) of embodiments of the invention 1, for using measurement result example, (b) of two-dimensional x-ray detector, is (a) the X ray reflection curve being caused by (111) and (001) of obtaining along χ direction of principal axis integral and calculating in (110) diffraction.
Fig. 7 is the performance plot of the KNN piezoelectric membrane (KNN-2) of embodiments of the invention 1, (a) for using the measurement result example of two-dimensional x-ray detector, (b) be the X ray reflection curve being caused by (111) and (001) of obtaining along χ direction of principal axis integral and calculating in (110) diffraction.
Fig. 8 is the performance plot of embodiments of the invention 1, (a) is the axonmetric chart of utmost point figure, (b) for the axonmetric chart of utmost point figure being transformed to the figure of orthogonal coordinates.
Fig. 9 is the utmost point figure of embodiments of the invention 2, (a) usings (001) orientation as the model of the utmost point (110) utmost point figure, (b) usings the model of (111) orientation as the utmost point (110) utmost point figure.
Figure 10 is for showing the figure of the X-ray diffraction curve characteristic of embodiments of the invention 2, (a) be the measurement result of the X-ray diffraction curve shown in Fig. 6 and Fig. 7 to be carried out to the example of Fitting Analysis, (b) be the integrated intensity obtaining for the Fitting Analysis by Figure 10 (a), considered the analysis result example of the volume fraction of (001) and (111) after correction coefficient.
Figure 11 is the sectional view of the KNN piezoelectric thin film device of embodiments of the invention 3, is (a) schematic diagram that forms the high alignment films of KNN piezoelectric membrane, (b) shows that the crystal grain of the high KNN piezoelectric membrane being orientated is with respect to the schematic diagram of real estate inclination.
Figure 12 be embodiments of the invention 4 KNN piezoelectric membrane spatter film forming film-forming temperature be derived from the graph of a relation of the integrated intensity of (111) and (001) preferred orientation.
Figure 13 shows in the spatter film forming of KNN piezoelectric membrane of embodiments of the invention 4 with respect to (001) orientation component of film-forming temperature and the variation diagram of (111) orientation component.
Figure 14 shows in the spatter film forming of KNN piezoelectric membrane of embodiments of the invention 4 variation diagram with respect to the internal stress of film-forming temperature.
Figure 15 shows that the real estate of KNN piezoelectric membrane that (001) and (111) preferred orientation with respect to embodiments of the invention 4 coexists is, the crystal grain of each preferred orientation has the sectional view at certain inclination angle.
Figure 16 in the piezoelectric thin film device of piezoelectric membrane that uses embodiments of the invention 5, be derived from the integrated intensity of (111) preferred orientation of piezoelectric membrane and the graph of a relation of piezoelectric constant.
Figure 17 be in the piezoelectric thin film device of piezoelectric membrane that uses embodiments of the invention 5, the volume fraction of (111) orientation component of piezoelectric membrane and the graph of a relation of piezoelectric constant.
Figure 18 be in the piezoelectric thin film device of the piezoelectric membrane of the present invention that uses embodiments of the invention 5 to form, the volume fraction of (001) orientation component of piezoelectric membrane and the graph of a relation of piezoelectric constant.
Figure 19 is for for making the concise and to the point pie graph of RF sputter equipment of the piezoelectric thin film device of the piezoelectric membrane that uses embodiments of the invention 3.
Figure 20 be in the substrate with piezoelectric membrane (wafer) of piezoelectric membrane that uses embodiments of the invention 5, the volume fraction of (111) orientation component and the graph of a relation of the piezoelectric constant deviation (%) in wafer face of piezoelectric membrane.
Figure 21 is the concise and to the point pie graph of the piezoelectric membrane device of one embodiment of the present invention.
Figure 22 is for being used the schematic cross-section of the filter of piezoelectric membrane of the present invention.
Embodiment
The execution mode of the piezoelectric thin film device that below explanation the present invention relates to.
[summary of execution mode]
The present inventor is piezoelectric membrane for the non-lead that is positioned at the key position of piezoelectric device, by quantitatively and accurately controlling the crystal orientation that prior art was not studied, recognizing, can realize piezoelectric thin film device and the piezo-electric device that shows high piezoelectric constant.
When not managing and controlling the crystal orientation of piezoelectric membrane, cannot obtain high piezoelectric constant, and because crystal orientation is complied with into film location difference and difference, thereby piezoelectric constant heterogeneity in device.
Adopt embodiments of the present invention, by the suitable selected electrode as constituent material, piezoelectric membrane etc., control the membrance casting conditions such as film-forming temperature of piezoelectric membrane simultaneously, by the volume fraction of (001) of the crystallographic axis of the preferred orientation of piezoelectric membrane and (111) composition (the composition ratio of crystal orientation) separate provision in prescribed limit, thereby can realize piezoelectric thin film device and the manufacture method thereof that piezoelectric property is high.
[a kind of basic structure of piezoelectric thin film device]
The piezoelectric thin film device of present embodiment has the stepped construction consisting of following: substrate; Be formed at the surperficial oxide-film of described substrate; Be formed at the lower electrode layer on described oxide-film; Be formed at the piezoelectric membrane on described lower electrode layer; Be formed at the top electrode layer on described piezoelectric membrane.
This piezoelectric membrane is the ABO with perovskite structure
3type oxide, it consists of: A position is the a kind of above element being selected from Li, Na, K, La, Sr, Nd, Ba and Bi, and B position is the a kind of above element being selected from Zr, Ti, Mn, Mg, Nb, Sn, Sb, Ta and In, and O is oxygen.
Described substrate can be enumerated and be selected from Si substrate, MgO substrate, zno-based plate, SrTiO
3substrate, SrRuO
3any a kind of substrate in substrate, glass substrate, quartz glass substrate, GaAs substrate, GaN substrate, sapphire substrate, Ge substrate, stainless steel substrate etc.Especially expectation is for price is low and the industrial Si substrate that has practical achievement.
The described oxide-film forming on the surface of substrate can enumerate the heat oxide film that forms by thermal oxidation, by CVD(chemical vapour deposition (CVD), Chemical Vapor Deposition) the Si oxide-film that forms of method etc.In addition, also can not form described oxide-film, and at quartz glass (SiO
2), MgO, SrTiO
3, SrRuO
3on the oxide substrates such as substrate, directly form the lower electrode layers such as Pt electrode.
The electrode layer that the alloy that it is main component that described lower electrode layer is preferably by Pt or the Pt of take forms or the electrode layer that comprises the electrode layer forming that they are laminated.In addition, preferred described lower electrode layer forms at (111) planar orientation, between the electrode layer forming, can be provided for improving the adhesive linkage with the adaptation of substrate at substrate and the alloy that is main component by Pt or the Pt of take.(111) the Pt film of planar orientation plays the effect of basalis for piezoelectric membrane.
Also can be the ABO as described piezoelectric membrane
3type oxide is with potassium-sodium niobate, lithium potassium niobate sodium (hereinafter referred to as LKNN), use general formula (Na
xk
yli
z) NbO
3the piezoelectric membrane that the perofskite type oxide that (0≤x≤1,0≤y≤1,0≤z≤0.2, x+y+z=1) represents is principal phase.Also the Ta of ormal weight or V etc. can adulterate in LKNN film.Described piezoelectric membrane can be used the formation such as RF sputtering method, ion beam sputtering or CVD method.In present embodiment, adopt RF sputtering method.
[crystal orientation according to execution mode is controlled]
About the crystal orientation of LKNN film, not it at length do not analyzed in the past and not take that it is controlled accurately as benchmark.That is, still indefinite about the crystal orientation of this piezoelectric membrane so far: whether to be random state of orientation; Or only whether certain 1 axle is in the orientation preferentially orientation vertical with Si real estate; Or specific 2 axles or axles more than 2 axles are with ratio preferred orientation of which kind of degree etc.In other words, about determining the crystal orientation of one of factor of the characteristic of this piezoelectric membrane, owing to not carrying out for finding out the accurate quantitative analysis of minor variations, and only based on evaluation result qualitatively, make this piezoelectric membrane, so high piezoelectric constant that cannot well reproduced expectation.
Actual in presenting the LKNN film of this (001) preferred orientation sexual state, its piezoelectric property complies with into film location or every production batch is different and different.Its reason is: owing to can not finding the slight change of (001) orientation of this piezoelectric membrane, for comprising that (001) (110) orientation, (111) orientation and (210) orientation in being oriented in waits, do not carry out detailed analysis in addition, be therefore difficult to strictly control the orientation of above-mentioned each crystal face and crystal is grown.
For example, input power (Power) during by increase spatter film forming, due to the impact of Ar ion homenergic particle, a large amount of sputtering particles is driven on substrate forcibly in a certain direction, its result has formed the piezoelectric membrane that has the polycrystalline particle of larger inclination with the normal direction of substrate surface.Now, adopt the known easy X-ray diffraction method that is called as 2 θ/θ scanning, can confirm that crystal orientation is roughly (001) preferred orientation, in this mensuration, because the position of sample except the axle (θ) of the angle of diffraction is all fixed, thereby cannot evaluate actual crystal orientation.Its result, due to the coexisting state of indefinite other crystal orientation composition or do not obtain the measurement result of tight embodiment orientation, so cannot hold the deteriorated of the piezoelectric property that caused by structure, result is recognized and cannot be realized the further raising of piezoelectric constant or the steady production of piezoelectric membrane.
According to above-mentioned opinion, control the crystal orientation of Pt film and piezoelectric membrane.
[crystal orientation of lower electrode layer]
(crystal orientation of Pt film)
Thereby first, in order strictly to manage and control the crystal orientation of LKNN film, carry out the optimization as crystalline film-forming temperature, film forming gas and the vacuum degree etc. of the Pt film of the lower electrode of the initial crystal aufwuchsplate of this piezoelectric membrane for stable realization.As membrance casting condition, first carry out the research of film-forming temperature, as the condition that forms (111) preferred orientation, find that the film forming scope of 100 ~ 500 ℃ is optimum temperature range.As film forming gas, can use Ar gas, Ar and O
2mist or be mixed with He, Ne, Kr and N
2deng in the gas of at least one above non-active gas.
In addition in order to improve the flatness on Pt surface, be formed for improving conduct and extremely count the Ti of the surface smoothing of nm with the inhomogeneity 0.1nm of the Ti layer of the close binder of substrate, by the top at Ti layer, form Pt electrode, the surface roughness of Pt lower electrode can be reduced and is controlled at the size of several nm.
And then accurately control the thickness of Pt lower electrode layer, and reduce the concave-convex surface of Pt lower electrode layer, also can form by controlling the crystal grain size homogenization of Pt lower electrode layer the Pt lower electrode layer of polycrystalline.
Lower electrode layer, relevant with its crystal orientation, be the individual layer of the orientation preferentially orientation vertical with substrate surface or the electrode layer of stepped construction.Lower electrode layer not only can for Pt, also can be for take alloy that Pt is main component or be Pt or the Pt of the take film (Pt film) that is main component.In addition, can also comprise Au, Ru, Ir, Sn, In and oxide thereof, with piezoelectric membrane in the layer of the compound that forms of contained element.In these situations, by the situation with Pt film, similarly carry out the optimization of film-forming temperature, film forming gas, can stablize the crystallinity of the lower electrode film of realizing the substrate that is positioned at LKNN film.Manufacturing conditions causes the state of the crystal orientation of piezoelectric membrane to change.In addition, the internal stress of described piezoelectric membrane (strain) is changed to compression stress or tensile stress.Sometimes be stressless state, i.e. strainless state.
In addition, as the candidate who is used to form the substrate of these lower electrode films, expect for Si, MgO, ZnO, SrTiO
3, SrRuO
3, glass, quartz glass, GaAs, GaN, sapphire, Ge, stainless steel etc. crystal or noncrystal or their complex etc., for being formed with close binder, lower electrode layer on these substrates, on the top of close binder, lower electrode layer, be formed with the device of LKNN film, at length compare the crystal orientation of LKNN film, in reality, recommend to choose the substrate that can strictly control preferred orientation.
[crystal orientation of piezoelectric membrane]
In addition, in order to realize more reliably the preferred orientation of LKNN film, in the above-described embodiment, by seeking that the heat treatment after the kind of the film-forming temperature of LKNN film self, sputtering operation gas, operating gas pressure, vacuum degree, input power and film forming is carried out to optimization, thereby found the manufacturing conditions of this piezoelectric membrane with the crystal orientation that improves piezoelectric property, reached object.By making these conditions adapt to each device or various environment, and discuss in detail and strictly manufacturing conditions, evaluation and management method etc., can reproduce the LKNN film that forms well the accurate cubic crystal of (001) preferred orientation, (111) preferred orientation or the preferred orientation that both coexist.
In order strictly to control the preferred orientation of the LKNN film self of polycrystalline or epitaxially grown monocrystalline, for example, accurately set and make film-forming temperature remain constant, thereby (001) orientation component or (111) orientation component are fallen in certain proportion.Heater during as actual film forming, uses thermal radiation or the use that infrared lamp produces to utilize Jie to be conducted by the heat of the heater heating of heat-conducting plate, falls into the setting in the temperature range that forms most suitable crystal orientation composition ratio.
In addition, coordinate described condition, by the pressure of gas or the size of flow in sputter input power, importing film formation device are defined as to most suitable value, and select suitable gaseous species, can expect following effect: can obtain comprise (001) orientation and (111) strictly controlled as crystal structure and be oriented in interior various orientation components, stablize and reproduce the LKNN film that obtains well showing high piezoelectric constant.
Specifically, use by Ar and O
2mist or be mixed with Ar gas, He, Ne, Kr and N
2deng in the plasma of γ-ray emission of at least one above non-active gas carry out spatter film forming.In the film forming of LKNN piezoelectric membrane, can use (Na
xk
yli
z) NbO
3the ceramic target of (0≤x≤1.0,0≤y≤1.0,0≤z≤0.2).
In addition, according to above-mentioned situation, also can pass through to change the density of sputter target material, and expect same effect.
In addition, after film forming, can in oxygen or in non-active gas or in both mists or in air or in vacuum, carry out heat treated, thereby carry out the control of the internal stress etc. of piezoelectric membrane.
The LKNN film so obtaining has the aggregate structure that the crystal grain by column structure forms.In addition, when described lower electrode layer forms at (111) planar orientation, preferred orientation in the prescribed direction with respect to described lower electrode layer and form described piezoelectric thin film layer.
In addition, preferred described piezoelectric thin film layer is at least one state coexisting in (001) preferred orientation crystal grain, (110) preferred orientation crystal grain and (111) preferred orientation crystal grain.By realizing the state of this kind of crystal orientation, can control internal stress and improve piezoelectric property.
The piezoelectric membrane that forms the piezoelectric thin film device of embodiment 1 has accurate cubic crystal, regular crystal or orthorhombic crystal structure, or is at least one state coexisting in these crystal structures.In addition, piezoelectric membrane some specific axis preferred orientation below 2 axles in their crystallographic axis.And, piezoelectric membrane forms: as the composition of the crystallographic axis of described orientation, in the ratio of (001) composition and (111) composition, with the two add up to 100% time, (001) volume fraction of composition is in 60 to 100% scope, and the volume fraction of (111) composition is in 0 to 40% scope.By forming this kind of formation, can prevent from increasing and reducing piezoelectric constant because crystal orientation presents random or internal strain.(Figure 16 ~ Figure 18 of embodiment 5)
For the volume fraction of (001) composition of the piezoelectric membrane with above-mentioned in 60 to 100% scope or the mode film forming of the volume fraction of (111) composition in 0 to 40% scope, can realize by controlling the membrance casting condition of piezoelectric membrane, for example, be controlled to film temperature.(Figure 13 of embodiment 4)
[strain of piezoelectric membrane]
The composition of crystal orientation by controlling described piezoelectric membrane is than (volume fraction), can make to have the strain of tensile stress state in the direction parallel with real estate, or can make to have the strain of compressing stress state in the direction parallel with real estate.In addition, by controlling volume fraction, can make described piezoelectric membrane be do not have internal stress without strain regime.In addition, by controlling volume fraction, can make described piezoelectric membrane with the perpendicular or parallel direction of real estate or there is inhomogeneous strain in two directions.By so controlling the volume fraction of piezoelectric membrane, can control the internal stress of piezoelectric membrane, can obtain having the piezoelectric membrane of the internal stress of expectation.(Figure 13 of embodiment 4, Figure 14)
[piezoelectric membrane device]
The substrate with piezoelectric membrane for above-mentioned execution mode, by the top at described piezoelectric thin film layer, form top electrode layer 15, can make the piezoelectric thin film device that shows high piezoelectric constant, again by this piezoelectric thin film device being processed as to regulation shape and voltage applying unit (voltage detection unit) 16 being set, thereby can make various drivers or sensor piezoelectric membrane device.(Figure 21)
In addition, for the substrate with piezoelectric membrane of above-mentioned execution mode, by the top at described piezoelectric membrane, form the pattern electrode 51 with predetermined pattern, can make the filter that utilizes surface acoustic wave.(Figure 22)
In addition, utilize in the filter of surface acoustic wave, described lower electrode (Pt film) mainly plays the effect of basalis.
Be formed at above-mentioned piezoelectric membrane top top electrode layer or there is the pattern electrode of predetermined pattern, be similarly preferably Pt with lower electrode layer or take alloy that Pt is main component or comprise these and take the electrode layer of stepped construction of the electrode layer that Pt is main component.In addition, can be also comprise Ru, Ir, Sn, In and oxide thereof, with piezoelectric membrane in the electrode layer of stepped construction of electrode layer of the compound that forms of contained element.
[effect of execution mode]
The present invention has following more than one the effect of enumerating.
(1) if adopt more than one execution mode of the present invention, LKNN piezoelectric membrane has accurate cubic crystal, regular crystal or orthorhombic crystal structure, or be at least one state coexisting in these crystal structures, some specific axis preferred orientation in their crystallographic axis below 2 axles, and the composition as the crystallographic axis of described orientation, in the ratio of (001) composition and (111) composition, with the two add up to 100% time, by making the volume fraction of (001) composition in 60 to 100% scope, (111) volume fraction of composition is in 0 to 40% scope, can prevent from presenting random because of crystal orientation, internal strain increases and reduction piezoelectric constant.
(2) in addition, if adopt more than one execution mode of the present invention, can be by suitably choosing piezoelectricity film, electrode, substrate, the adhesive linkage as constituent material, attempt the manufacturing conditions of this material of optimization simultaneously, accurately measure the crystal orientation degree of the piezoelectric membrane obtain thus and quantitative exactly, the strict atomic level structure of controlling piezoelectric membrane, improves piezoelectric property.Its result, when realizing high performance piezoelectric membrane device, can improve the fabrication yield of this device.
(3) in addition,, if adopt more than one execution mode of the present invention, by the state coexisting for the crystal grain of (001) preferred orientation and the crystal grain of (111) preferred orientation, can control internal stress and improve piezoelectric property.And then by relaxing stress, can suppress film and peel off, therefore the mechanical strength raising of piezoelectric membrane, the piezoelectric membrane of ease of processing excellence can be provided.
(4) in addition, if adopt more than one execution mode of the present invention, lower electrode as above-mentioned piezoelectric thin film device, by use, controlled the compound that in the Pt electrode of crystal orientation or Pt alloy or Ru, Ir and oxide, Pt and piezoelectric film, contained element forms, can high accuracy control the piezoelectric film that top forms crystal orientation, improve environment resistant as device.
(5) in addition, if adopt more than one execution mode of the present invention, about substrate, by using Si and MgO substrate, zno-based plate, SrTiO
3substrate, SrRuO
3substrate, glass substrate, quartz glass substrate, GaAs substrate, GaN substrate, sapphire substrate, Ge substrate, stainless steel substrate etc., can control on it crystal orientation of the piezoelectric film forming.
(6) in addition,, if adopt more than one execution mode of the present invention, by present embodiment, can realize the good piezoelectric membrane of piezoelectric property, and can obtain to high finished product rate high-quality piezoelectric thin film device.
(7) in addition, if adopt more than one execution mode of the present invention, because being possesses the piezoelectric thin film device that does not use plumbous film, by carrying this piezoelectric thin film device, can realize mini-system devices such as reducing environmental pressure and high performance miniature motor, transducer and driver, MEMS(MEMS (micro electro mechanical system) for example, Micro Electro Mechanical System) etc.Can realize the filter that utilizes surface acoustic wave and there is good filtering characteristic.
(8) in addition, if adopt more than one execution mode of the present invention, when using Si substrate manufacture driver or transducer, for the non-lead that is positioned at the key position of piezoelectric device, it is piezoelectric membrane, due to its crystal orientation of control and management quantitatively and accurately, therefore stably Production Life is long and show that the non-lead of high piezoelectric constant is device.In device, different with the difference at position due to its crystal orientation in addition, thus the piezoelectric constant homogenization of the piezoelectric membrane forming on substrate, thus the rate of finished products of raising manufacture view.
(9) in addition,, if adopt more than one execution mode of the present invention, can control and use the orientation of LKNN etc. and seek to improve piezoelectric property.
(10) in addition, if adopt more than one execution mode of the present invention, by stably controlling the crystal orientation of these piezoelectric membranes, the piezoelectric property that can realize piezoelectric thin film device, piezoelectric membrane device improves or stabilisation, thereby high performance micro device can be provided at an easy rate.
(11) in addition,, if adopt more than one execution mode of the present invention, according to the present invention, can access piezoelectric thin film device or the piezoelectric membrane device of the piezoelectric property excellence of the atomic level structure of having controlled accurately the piezoelectric membranes such as LKNN.
The following describes embodiments of the invention.
(embodiment 1)
Use Fig. 1 ~ Fig. 8 explanation.
Fig. 1 shows the sectional view with the overview of the substrate of piezoelectric membrane.In the present embodiment, form adhesive linkage 2 having on the Si substrate 1 of oxide-film, on the top of this adhesive linkage 2, form successively the piezoelectric thin film layer 4 of the KNN of lower electrode layer 3 and perovskite structure, make piezoelectric thin film device.
Now, the crystallographic system of described piezoelectric thin film layer 4 be as the criterion cubic crystal or regular crystal or orthorhombic, at least a portion of piezoelectric thin film layer 4 can be ABO
3crystal or noncrystal or both mix composition.At this, A is the a kind of above element being selected from Li, Na, K, La, Sr, Nd, Ba and Bi, and B is the a kind of above element being selected from Zr, Ti, Mn, Mg, Nb, Sn, Sb, Ta and In, and O is oxygen.Although the piezoelectric as A position can, for containing the formation of Pb, still require not contain the piezoelectric membrane of Pb from the viewpoint of environment.
As lower electrode layer 3, can use Pt film or Au film.Or can be Pt alloy, the alloy that contains Ir, Ru, can be also their stepped construction.
Below describe the manufacture method of piezoelectric thin film device.First, on the surface of the Si of the toroidals of 4 inches substrate 1, form heat oxide film, on heat oxide film, form lower electrode layer 3.Wherein, heat oxide film be take the mode that thickness is 150nm and is arranged.
Then, on this lower electrode layer, form KNN film as piezoelectric thin film layer 4.For the film forming of KNN film, also use sputtering method and form.At substrate temperature, be 700 ℃ ~ 730 ℃, Ar and O
2the condition of plasma that produces of the mist of 5:5 under implement spatter film forming and form KNN film.In addition, target is used (Na
xk
yli
z) NbO
3the ceramic target of (x=0.5, y=0.5, z=0).Carry out film forming until thickness is 3 μ m.In addition, after film forming, in air, carry out heat treated.Wherein, sputter is used from revolving round the sun stove, and distance during sputter between substrate and target (following, TS spacing) is made as 50mm.
For the KNN film of such making, use the observation cross sectional shapes such as scanning electron microscopy, its tissue consists of column structure.Use conventional X-ray diffraction device investigation crystal structure, results verification: as shown in the X-ray diffractogram of Fig. 2 (2 θ/θ sweep measuring), carry out base plate heating and the Pt film of the embodiment 1 that forms has formed the film of (111) planar orientation vertical with substrate surface.
On the Pt film of this (111) preferred orientation, form KNN film, results verification: the KNN film of making is the polycrystal film with the perovskite type crystal structure of accurate cubic crystal as shown in Figure 3.In addition, from the X-ray diffractogram of Fig. 2, owing to only confirming, have (001), a diffraction maximum of (002), (003), thereby measurable KNN piezoelectric membrane is (001) preferred orientation substantially.
In the present embodiment 1, for the KNN piezoelectric membrane of having a mind to control crystal orientation, in order to evaluate in detail and accurately the orientation of this KNN film, carried out the mensuration of utmost point figure (Pole figure).Utmost point figure is the figure of expansion of the utmost point of stereoprojection specific lattice face, is the analytical method of state of orientation that can detailed assessment polycrystalline.Detailed content please refer to and quotes that routine 1(Electric Co., Ltd of science compiles, X-ray diffraction introduction (X-ray diffraction hand draws I), revision the 4th edition, (Electric Co., Ltd of science 1986)), quote that routine 2(カ リ テ ィ work, new edition X-ray diffraction will be discussed, (ア グ ネ, 1980)).
Mensuration by described utmost point figure can clear and definite preferred orientation definition.For the material being formed by polycrystalline (comprising film), when each crystal grain is the state of certain certain orientation " preferred orientation ", in the utmost point figure of this material measures, one finds the local distribution of the X ray reflections such as debye ring of hot spot shape or ring-type surely in specific angle position.
On the other hand, each crystal grain of described material during for direction arbitrarily, while being " random orientation " in other words, cannot find the reflection of the X ray of hot spot shape or ring-type in utmost point figure.According to having or not of these X ray reflections, can judge whether preferred orientation of this piezoelectric membrane, and the definition existing as preferred orientation.
In the structural analysis of the piezoelectric thin film device of the present embodiment 1, use is equipped with " D8 DISCOVER with Hi Star, the VANTEC2000(registered trade mark) " of the high-output power X-ray diffraction device Bruker AXS company system of the two-dimensional detector that possesses large area x-ray detection range.In the present embodiment, measure the utmost point figure using (110) of KNN film as the utmost point.
Fig. 4 shows the schematic diagram of the mensuration configuration of the utmost point figure carrying out in the present embodiment.This is the method that is called as Shu Erci (Schultz) bounce technique.In utmost point figure in the past measures, because the X-ray detector using is zero dimension mostly, therefore need simultaneously χ (α) axle shown in scintigram 4 and
(β) axle needs long-time mensuration thereupon.Yet, owing to having used large-area two-dimensional detector (D8 DISCOVER with Hi Star in the present embodiment, VANTEC2000(registered trade mark)), thereby need hardly to follow the action of zero dimension detector of the scanning of described 2 axles, so can measure in short time.Therefore, can be in a large number and promptly obtain under various conditions the analysis result of the crystal orientation of the KNN film of making, thus realize the KNN piezoelectric membrane with crystal structure of the present embodiment.
Fig. 5 shows the analysis result of wide-angle reciprocal lattice point diagram in the piezoelectric membrane of embodiment 1.Transverse axis is the x-ray diffraction angle of 2 θ/θ, and the longitudinal axis is the χ axle in axle (2 θ/θ) vertical direction with the angle of diffraction shown in Fig. 4.In addition, the bar chart on right side embodies the intensity of X ray reflection by black and white gray scale, as the benchmark of X ray reflection intensity on same figure.
Fig. 5 (a) shows the actual analysis result of KNN, and Fig. 5 (b) shows the result of the KNN film reciprocal lattice point simulation being orientated for (001)/(111) relatively.Zero represents the diffraction X ray from (001) orientation KNN, ● represent the diffraction X ray from (111) orientation KNN.The simulation program now using is the SMAP/for Cross Sectional XRD-RSM that Bruker AXS provides.
Two figure are more known, at the 2 θ/θ that is equivalent to 110 diffraction, be about under 32 °, in the scope of 15 ° to 75 ° centered by χ=45 °, can confirm two 110 diffraction in (001) orientation and (111) orientation.This analysis result implies that in this piezoelectric membrane, (001) orientation coexists with (111) orientation.Owing to only measuring and cannot measure the axial X-ray diffraction curve of χ with the X-ray diffraction of 2 θ of routine/θ scanning, so the analysis result of the present embodiment is to have found an example that relates to the new structural parameters that improve piezoelectric membrane characteristic.
Fig. 6 has shown the X-ray diffraction measurement result of this piezoelectric membrane actual in embodiment 1.Fig. 6 (a) has shown the diffraction X ray from sample KNN-1 with X ray two-dimensional detector record, has the reflection that the black spots point-like pattern that plots arc is equivalent to diffraction X ray.In addition, the direction of painting arc is equivalent to described χ direction of principal axis, and the arrow of the normal direction relative with arc is equivalent to the direction of 2 θ/θ.When paying close attention to 2 θ/θ and being about the diffraction X ray under 32 °, observe the overlapping phenomenon of spot of two X ray reflections.Now the spot in known left side is for by KNN(111) X ray reflection that causes of orientation, the spot on right side is for by KNN(001) X ray reflection that causes of orientation.
Based on these results, by setting limit of integration by fan shape, can show the reflection X-ray spectrum that caused by (001) orientation and (111) orientation intensity separately.The integration of the present embodiment carries out in the scope of 17.5 ° to 72.5 °, χ axle, the axial integration of 2 θ/θ carries out in the scope of 31.4 ° to 32.4 °.
Fig. 6 (b) shows integral result.Transverse axis is χ axle, the X-ray diffraction intensity of the longitudinal axis for obtaining according to described integral condition.Can find out by (001) orientation and the reflection X-ray spectrum that causes of (111) orientation intensity separately.
Fig. 7 shows in embodiment 1 the X-ray diffraction measurement result about this actual piezoelectric membrane of another sample KNN-2 film.Similarly known with Fig. 6, find two spectrums that caused by orientation.Yet known again, the X ray intensity being caused by (001) orientation is different from the result shown in Fig. 6 with the size of the X ray intensity being caused by (111) orientation, and the X ray intensity particularly being caused by (001) orientation is obviously different from the intensity ratio of the X ray intensity being caused by (111) orientation.
In the present embodiment, use fitting function to calculate the curve of Fig. 6 (b), Fig. 7 (b), implement the quantification of X ray reflection intensity and ratio thereof.
Fig. 8 shows the measurement result example of (110) utmost point figure of this piezoelectric membrane of embodiment 1.At this as shown in Figure 8 (a), utmost point footpath direction is made as to χ (α) axle, circumferencial direction is made as
(β) axle.On the χ axle of utmost point footpath direction, near being 45 °, the angle of distance center observes the ring (debye ring) of the diffraction surfaces that is equivalent to (001).On the other hand, near 35.3 °, observe the debye ring of the diffraction surfaces that is equivalent to (111).Especially known, each debye ring departs from concentrically ringed configuration, but slightly eccentric apart from center.Results verification is at circumferencial direction
on axle, 0 ° to approximately 80 ° and approximately 330 °, to the scope of 360 °, the reflection X ray being caused by (001) orientation is overlapping with the reflection X ray being caused by (111) orientation.Now, accurately calculate the intensity of each orientation component very difficult.
Therefore,, in order to eliminate this problem points, for the mensuration configuration shown in Fig. 4, need to consider that the position of the interior direction of rotation of face of sample (is equivalent at this
axle).In addition, most suitable
when axle is indefinite, measurement result that need to be based on utmost point figure, determines that the reflectance spectrum being caused by (001) orientation is clearly separated with the reflectance spectrum being caused by (111) orientation
axle.For this reason, importantly accurately hold the eccentric state of each debye ring, while finding the angle δ being equivalent between (001) direction of orientation and (111) direction of orientation to be maximum
the angle of axle.
In the present embodiment, in order to obtain exactly this δ, by the utmost point footpath direction shown in Fig. 8 (a), be that χ (α) axle, circumferencial direction are made as
(β) figure of the polar coordinates of axle system is converted to that transverse axis is made as χ axle, the longitudinal axis is made as
the figure of the orthogonal coordinate system of axle.Fig. 8 (b) demonstration is converted to after orthogonal coordinate system
figure.Based on Fig. 8 (b), while being maximum for the angle of δ
the integrated intensity that X ray reflection curve on shaft position (dotted line in Fig. 8 (b)) carries out each orientation component calculates.In addition, the integrated intensity herein obtaining is by being used Gauss (Gauss) function, Lorentz (Lorentz) function and obtaining as their raw (Pearson) function of Pesudo Voight function, Pierre of convolution function and the spectrum Fitting Analysis of the distribution functions such as Split Pesudo Voight function.
Known according to embodiment 1 as above, accurately calculate the intensity of orientation component as long as to the angle that is equivalent to the angle δ between (001) direction of orientation and (111) direction of orientation during for maximum
the integrated intensity that X ray reflection curve on shaft position carries out each orientation component calculates.
(embodiment 2)
With Fig. 9 ~ Figure 10 explanation.
Then, the diffracted intensity of accurately obtaining (001) orientation component and (111) orientation component than time, be necessary the corrected value of X-ray diffraction intensity separately to discuss.The utmost point figure that is for this reason directed to (001) and (111) investigates.
Fig. 9 shows the analog result of utmost point figure.Fig. 9 (a) is the analog result of the utmost point figure using (001) as the utmost point.As shown in this figure, (110) diffraction of the KNN of known (001) orientation has been contributed 4 diffraction of equal value.Now think that correction coefficient is 4.On the other hand, by the analog result as the utmost point figure of the utmost point by (111) of Fig. 9 (b), (110) diffraction of the KNN of known (111) orientation has been contributed 3 diffraction of equal value, so correction coefficient is 3.Therefore,, when the volume fraction of calculating (001) orientation of obtaining and (111) orientation when the integrated intensity of recording in embodiment 1 is 1:1, actual diffracted intensity is than being (001): (111)=4:3.
Below, the result that Figure 10 show needle is analyzed (001) and (111) orientation component ratio for the measurement result of piezoelectric membrane, the Fig. 6 shown in use embodiment 1 and Fig. 7 of the different KNN-1 of manufacturing conditions and KNN-2.Figure 10 (a) obtains the curve application fitting function of the X-ray diffraction shown in Fig. 6 (b).Smoothed curve is the Pesudo Voight function using as fitting function in the present embodiment.Known more consistent with the diffraction curve being caused by (111) and (001).Now, obtain peak position (χ axle in the present embodiment), integrated intensity and the half-peak breadth of each curve.At this, because of object, be to calculate diffracted intensity ratio, so pay close attention to integrated intensity.Figure 10 (b) shows the table that analysis result is concluded.The integrated intensity of enumerating in embodiment 1, with regard to KNN-1, the integrated intensity of relevant (111) orientation is 298, the integrated intensity of (001) orientation is 2282.
On the other hand, with regard to KNN-2, the former is 241, the latter is 2386.For these integral and calculating results, by the correction coefficient divided by described, as the integrated intensity corrected value shown in Figure 10 (b), thereby obtain the accurate diffracted intensity of each orientation component.If by (001) orientation component and (111) orientation component and be made as 100% and analyze, the volume fraction that result obtains KNN-1 is (001): the volume fraction of (111)=85%:15%, KNN-2 is (001): (111)=88%:12%, between known sample, orientation component is than different.
(embodiment 3)
With Figure 11, Figure 19 explanation.
The KNN film of the preferred orientation that trial making embodiment 1 relates to.As embodiment 3, Figure 11 shows its schematic cross-section.In addition, Figure 19 shows for making the skeleton diagram of the RF sputter equipment of KNN film.Piezoelectric thin film device is: be formed with adhesive linkage 2 having on the Si substrate 1 of oxide-film, be formed with the piezoelectric thin film layer 4 of the KNN of lower electrode layer 3 and perovskite structure on the top of adhesive linkage 2.At this, the piezoelectric membrane of polycrystalline has by the crystal grain of each column structure (columnar crystal grains) roughly arranges by certain fixed-direction the aggregate structure forming.
In the present embodiment 3, input power being set as to 100W, make the sputtering target 12 center shown in Figure 19 consistent with substrate 1 center and while carrying out the film forming of KNN piezoelectric membrane 4, can make the piezoelectric membrane of the basically identical polycrystalline of the normal of (001) crystal face as shown in Figure 11 (a) shows and the normal direction of real estate.At this, columnar crystal grains 5 is crystalline growth in the direction perpendicular to substrate.Now, in the mensuration of axonmetric chart that adopts utmost point figure, bias is not found with the debye ring of (111) in (001) drawing, and with concentric circles, configures.In addition, by the χ axle of described axonmetric chart and
when axle changes the figure of the orthogonal thereto axle of x-y axle into, do not see wavy curve, and be linearity.
Below, in the present embodiment, when input power being set as to 100W, being configured and implementing film forming according to the position that makes the substrate 1 centre-to-centre spacing sputtering target 12 center deviation shift 10mm shown in Figure 19, the normal direction of crystal face that can confirm the crystal grain of preferred orientation depart from a little real estate normal direction and at a slant.Now, columnar crystal grains 6 is with respect to the normal direction of real estate crystalline growth (Figure 11 (b)) obliquely.In addition, side-play amount is suitably determined according to the inclination angle of the substrate size using, expectation.In using the present embodiment of 4 inches of Si substrates, side-play amount is made as 10mm.
In the axonmetric chart of utmost point figure of the present embodiment that side-play amount is made as to 10mm, similarly observe two debye rings of (001) and (111) with Fig. 8 (a), different from the same known amplitude separately of Fig. 8 (b).That is, each crystal face of expression (001) and (111) is different from the deflecting angle of real estate.Now, the assay value of the amplitude of (001) is 9.9 °.On the other hand, the assay value of the amplitude of (111) is 0.52 °.Result is known, and in piezoelectric membrane of the present invention, with respect to the normal direction of real estate, the angle of the crystal orientation direction of (001) tilts approximately 5 °, and the angle of the crystal orientation direction of (111) tilts approximately 0.3 °.
(embodiment 4)
With Figure 12 ~ Figure 15 explanation.
The present embodiment shows and to change wittingly the result that the volume fraction of the orientation component of (001) and the orientation component of (111) is made.
Figure 12 shows in spatter film forming method the variation with respect to the integrated intensity of the diffraction that is caused and caused by (001) by (111) of film-forming temperature.The known diffracted intensity being caused by (001) reduces with the rising of film-forming temperature.On the other hand, about the diffracted intensity being caused by (111), the known rising with film-forming temperature increases.Below, use these results, the film-forming temperature dependence of considering the volume fraction after correction coefficient shown in embodiment 2 is discussed.
Figure 13 shows in spatter film forming method the variation with respect to the volume fraction of (111) and (001) orientation component of the film-forming temperature of KNN piezoelectric membrane.As shown in this figure, known within the scope of the film-forming temperature of 550 ℃ to 650 ℃, the volume fraction of (111) orientation component is 0 substantially, and while surpassing 650 ℃, the volume fraction of (111) orientation component increases along with the increase of film-forming temperature.
On the other hand, the variation of the volume fraction of relevant (001) orientation component with respect to film-forming temperature, known in the scope of 550 ℃ to 650 ℃, (001) orientation component is 100% substantially, is only almost the autoorientation state of (001) face.In addition we know,, if surpass 650 ℃, the volume fraction of (001) orientation component reduces gradually along with the rising of film-forming temperature.In the present embodiment, demonstration can, by changing over film temperature, be controlled the ratio of (111) orientation component and (001) orientation component.
In addition, Figure 14 shows in spatter film forming method the variation with respect to the internal stress (strain) of the film-forming temperature of KNN piezoelectric membrane.Known along with film-forming temperature raises, compression stress reduces, to unstressed strainless state-transition.Known when film-forming temperature is increased to 700 ℃ ~ 750 ℃, by the state to micro-tensile stress without transformation for strain substantially.In addition, as the unit example of internal stress in the present embodiment, can enumerate Pa.
As long as more known with Figure 13, because manifesting compression stress, the increase of the volume fraction of (111) reduces.Demonstrate, by increasing (111) orientation component ratio of KNN piezoelectric membrane, the internal stress that can realize this piezoelectric membrane relaxes.The composition that result can be passed through accurately to control crystal orientation is than (volume fraction), and the internal stress of control piezoelectric membrane.
Because piezoelectric membrane has the volume fraction of (111) composition, so can relax the stress of piezoelectric membrane, can suppress film and peel off.The mechanical strength raising of piezoelectric membrane, the piezoelectric membrane of ease of processing excellence can be provided thus.
As one of above-mentioned execution mode, Figure 15 shows schematic cross-section.For the crystal grain ([001] axle orientation) 9 of (001) preferred orientation and crystal grain ([111] axle orientation) 10 states that coexist of (111) preferred orientation.By realizing the state of crystal orientation as shown in figure 15, can control internal stress and improve piezoelectric property.And then by relaxing stress, and can suppress film, peel off, so can provide, the mechanical strength of piezoelectric membrane improves, the piezoelectric membrane of ease of processing excellence.
The rate of finished products of the device that can be obtained by 4 inches of big or small substrates of polylith by confirmation, result obtains: the rate of finished products less than 70% of the device being obtained by the substrate that is less than 1% piezoelectric membrane with (111) composition, and the rate of finished products of the device being obtained by the substrate that is greater than 1% piezoelectric membrane with (111) composition surpasses 90%.
According to inventor's result of study, think that this is to cause because of the inclined to one side extent of the piezoelectric constant in wafer face.What the relation of the volume fraction of (111) orientation component and the piezoelectric constant deviation (%) in wafer face was confirmed the results are shown in table 1 and Figure 20.As shown in figure 20, known about the piezoelectric constant deviation in wafer face, even if when the volume fraction of (111) orientation component is roughly 1%, deviation does not also increase but is substantially fixing.Piezoelectric constant deviation shown here is the standard deviation of the piezoelectric constant measured in the 4 inches of wafer face relative standard deviation after divided by its mean value.Now its value is about 23%.Yet when (111) volume fraction is about 0.2%, deviation is in 15.3% ~ 27.1% fluctuation, even if (111) volume fraction is identical, in each wafer, the difference of piezoelectric constant deviate is also larger, becomes the reason that rate of finished products reduces.
[table 1]
| Sample | (111) volume fraction (%) | Piezoelectric constant deviation (%) |
| |
3.6 | 21.4 |
| |
3.3 | 24.5 |
| |
9.9 | 9.3 |
| |
12.6 | 9.4 |
| |
0.1 | 27.1 |
| |
0.1 | 25.6 |
| |
0.1 | 23.9 |
| |
0.2 | 15.3 |
| Sample 9 | 0.2 | 22.7 |
| |
9.8 | 16.3 |
(embodiment 5)
With Figure 16 ~ Figure 18 explanation.
As the present embodiment, Figure 16 shows that the piezoelectric property of KNN piezoelectric membrane is with respect to the variation of (111) integrated intensity.Transverse axis is (111) integrated intensity, and the longitudinal axis is piezoelectric constant.At this, the piezoelectric constant while showing the electric field that applies 6.7MV/m or 0.67MV/m as an example.Wherein, the unit of piezoelectric constant is arbitrary unit, and as the concrete example of actual piezoelectric constant, is the telescopic variation amount d perpendicular to electrode surface (thickness direction)
33, or be the telescopic variation amount d along electrode surface direction
31.
Because of below former thereby piezoelectric constant is made as to arbitrary unit.In order to obtain piezoelectric constant, need the numerical value such as Young's modulus, Poisson's ratio of piezoelectric body layer, and obtain the Young's modulus of piezoelectric body layer (piezoelectric membrane), the numerical value of Poisson's ratio being not easy.Especially the situation of film is different from blocks, the impact of the substrate using owing to being subject to self film (constraint etc.), and be not easy to obtain the Young's modulus of film self, the absolute value (true value) of Poisson's ratio (constant) from principle.Thereby use the current known Young's modulus of KNN film, the presumed value of Poisson's ratio is calculated piezoelectric constant.The piezoelectric constant that cause obtains is presumed value, in order to embody objectivity, so be made as relative arbitrary unit.Yet, though calculate the piezoelectric constant Young's modulus of KNN film used and the value of Poisson's ratio is presumed value, be also the value of reliability in a way, the approximately 80[arbitrary unit of piezoelectric constant] roughly can say piezoelectric constant d
31for 80[-pm/V].This situation is equally applicable to Figure 17 and Figure 18.
As shown in figure 16, when the X ray intensity being caused by (111) orientation increases slightly, can be observed the trend that piezoelectric constant has rising.Yet the integrated intensity being caused by (111) of analyzing in the present embodiment surpasses at 100 o'clock, can confirm the increase along with integrated intensity, piezoelectric constant dullness reduces.
Then, in order to carry out the comparison with (001) orientation component, table 2 and Figure 17 of table 2 drawing is shown to the piezoelectric property of KNN piezoelectric membrane is for the dependence of (111) orientation component ratio.Transverse axis is the volume fraction of (111) orientation component, and the longitudinal axis is piezoelectric constant.Known in the present embodiment, the composition of (111) orientation is in 0 to 20% scope, and piezoelectric constant increases along with the increase of (111) volume fraction, and it doesn't matter with the size that applies electric field.
Yet when (111) volume fraction surpasses 20%, known along with this volume fraction increases, piezoelectric constant will reduce.While especially surpassing 40%, known piezoelectric constant is about peaked half the value obtaining in the present embodiment.In other words, as the piezoelectric membrane of the present embodiment, in order to ensure being the more than 5 one-tenth of its maximum piezoelectric constant, wish that the volume fraction of (111) is below 40%.In addition, conventionally, for the piezoelectric property of piezoelectric is improved, improve degree of crystallinity also very important, confirm that the integrated intensity of X-ray diffraction will increase.In the present embodiment, the volume fraction of (111) is 30% when following, and degree of crystallinity is high, if stipulate most suitable volume fraction just can realize more high performance piezoelectric membrane realizing on the basis of high-crystallinity.
[table 2]
Below, table 3 and Figure 18 that table 3 is charted show that the piezoelectric property of KNN piezoelectric membrane is for the dependence of (001) orientation component ratio.The dependence of (001) volume fraction of known piezoelectric constant and the dependence of the volume fraction of (111) are negative relation.That is, known piezoelectric constant increases along with the increase of (001) orientation component.Yet (001) volume fraction is 80% when above, known piezoelectric constant has the trend reducing.In addition, as the piezoelectric membrane of the present embodiment, in order to be embodied as 5 one-tenth above values of its maximum piezoelectric constant, represent to wish that the volume fraction of (001) is more than 60%.In addition, in the present embodiment, the total of (001) and (111) volume fraction is assumed to 100%.
[table 3]
Known above, on substrate, at least dispose lower electrode, in the piezoelectric thin film device of piezoelectric membrane and upper electrode, its piezoelectric membrane has accurate cubic crystal, regular crystal or orthorhombic crystal structure, or be at least one state coexisting in these crystal structures, some specific axis preferred orientation in their crystallographic axis below 2 axles, and the composition as the crystallographic axis of described orientation, in the ratio of (001) composition and (111) composition, with the two add up to 100% time, by making the volume fraction of (001) composition in 60 to 100% scope, or make the volume fraction of (111) composition in 0 to 40% scope, accurately control crystal orientation, thereby can manufacture novel high performance piezoelectric thin film device.
As shown in Figure 17,18, when the piezoelectric thin film device that the substrate of the piezoelectric membrane that the volume fraction by with (111) composition is 21%, the volume fraction of (001) composition is 79% is obtained applies voltage 6.7MV/m, piezoelectric constant is 87.The deflecting angle of (001) of the piezoelectric thin film device obtaining and each crystal face of (111) and real estate is: with respect to the normal direction of substrate, (001) angle of crystal orientation direction tilts 3.0 °, and the angle of the crystal orientation direction of (111) tilts 0.5 °.
Now create conditions for: prepare the Si substrate of thickness 0.525mm as substrate, by effects on surface, impose thermal oxidation, and on the surface of Si substrate, form the oxide-film of 200nm.Then, under the condition of 350 ℃ of substrate temperatures, input power 100W, Ar gas 100% atmosphere, pressure 2.5Pa, 1 ~ 3 minute (Ti close binder) of film formation time, 10 minutes (Pt lower electrode), make Ti close binder film forming on heat oxide film of 2nm, and make (111) preferred orientation and Pt lower electrode film forming on Ti close binder of the 100nm that forms.
Target is used (Na
xk
yli
z) NbO
3(x=0.5, y=0.5, z=0), target density 4.6g/cm
3ceramic target, the mode that the thickness of take is 3 μ m is carried out the film forming of KNN piezoelectric film on Pt lower electrode.Substrate temperature during film forming is 700 ℃, input power 100W, use Ar and O
2the mist of 5:5, pressure is made as 1.3Pa.In addition, the side-play amount at the center of pinwheel and substrate is made as 10mm.In addition, after film forming, in air atmosphere, carry out 700 ℃, the annealing in process of 2.0hr.Wherein, sputter equipment is used from revolving round the sun stove, and TS spacing is made as 50mm.
So, by the suitable selected electrode as constituent material, piezoelectric membrane etc., control the membrance casting conditions such as film-forming temperature of piezoelectric membrane simultaneously, and the volume fraction of (001) and (111) composition of the preferred orientation of control piezoelectric membrane, can realize good piezoelectric property.In addition, enough good result that also to have obtained the rate of finished products of the device that obtained by the substrate with piezoelectric membrane be 96%.
Above, although the embodiment based on limited quantity describes the present invention, scope of the present invention is not limited to these embodiment.For example, as the factor except film-forming temperature, by changing, sputtering target forms, input power, the kind of operating gas, the kind of the flow of this gas, pressure or substrate, substrate or structure etc. during its film forming, can control crystal orientation and obtains having the piezoelectric membrane of the internal stress of expectation.Scope of the present invention should be defined by the claims, and comprises the various changes in claim and equivalency range thereof.
description of reference numerals
1 Si substrate
2 adhesive linkages
3 lower electrode layers
4 piezoelectric membranes
5 preferred orientation crystal grains
6 with the crystal grain of the equidirectional upper preferred orientation of normal direction of real estate
7 (001) preferred orientation crystal grains
8 (111) preferred orientation crystal grains
The angle of 9 (001) orientation orientation and substrate surface normal
The angle of 10 (111) orientation orientation and substrate surface normal
Claims (9)
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