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  • 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
  • C30B25/00—Single-crystal growth by chemical reaction of reactive gases, e.g. chemical vapour-deposition growth
  • C30B25/02—Epitaxial-layer growth
  • C30B25/18—Epitaxial-layer growth characterised by the substrate
  • C30B25/186—Epitaxial-layer growth characterised by the substrate being specially pre-treated by, e.g. chemical or physical means
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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
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  • C30B29/22—Complex oxides
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  • 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
  • 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
  • C30B29/22—Complex oxides
  • C30B29/30—Niobates; Vanadates; Tantalates
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  • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
  • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
  • H01L21/02104—Forming layers
  • H01L21/02365—Forming inorganic semiconducting materials on a substrate
  • H01L21/02518—Deposited layers
  • H01L21/02587—Structure
  • H01L21/0259—Microstructure
  • H01L21/02598—Microstructure monocrystalline
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  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
  • H01L21/70—Manufacture or treatment of devices consisting of a plurality of solid state components formed in or on a common substrate or of parts thereof; Manufacture of integrated circuit devices or of parts thereof
  • H01L21/71—Manufacture of specific parts of devices defined in group H01L21/70
  • H01L21/76—Making of isolation regions between components
  • H01L21/762—Dielectric regions, e.g. EPIC dielectric isolation, LOCOS; Trench refilling techniques, SOI technology, use of channel stoppers
  • H01L21/7624—Dielectric regions, e.g. EPIC dielectric isolation, LOCOS; Trench refilling techniques, SOI technology, use of channel stoppers using semiconductor on insulator [SOI] technology
  • H01L21/76251—Dielectric regions, e.g. EPIC dielectric isolation, LOCOS; Trench refilling techniques, SOI technology, use of channel stoppers using semiconductor on insulator [SOI] technology using bonding techniques
  • H01L21/76254—Dielectric regions, e.g. EPIC dielectric isolation, LOCOS; Trench refilling techniques, SOI technology, use of channel stoppers using semiconductor on insulator [SOI] technology using bonding techniques with separation/delamination along an ion implanted layer, e.g. Smart-cut, Unibond
• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
  • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
  • H03H9/02—Details
  • H03H9/02007—Details of bulk acoustic wave devices
  • H03H9/02015—Characteristics of piezoelectric layers, e.g. cutting angles
  • H03H9/02031—Characteristics of piezoelectric layers, e.g. cutting angles consisting of ceramic
• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
  • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
  • H03H9/02—Details
  • H03H9/02535—Details of surface acoustic wave devices
  • 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
• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
  • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
  • H03H9/46—Filters
  • H03H9/54—Filters comprising resonators of piezoelectric or electrostrictive material
• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
  • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
  • H03H9/46—Filters
  • H03H9/64—Filters using surface acoustic waves
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  • H10N30/00—Piezoelectric or electrostrictive devices
  • H10N30/01—Manufacture or treatment
  • H10N30/07—Forming of piezoelectric or electrostrictive parts or bodies on an electrical element or another base
  • H10N30/072—Forming of piezoelectric or electrostrictive parts or bodies on an electrical element or another base by laminating or bonding of piezoelectric or electrostrictive bodies
• • H—ELECTRICITY
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  • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10N30/00—Piezoelectric or electrostrictive devices
  • H10N30/01—Manufacture or treatment
  • H10N30/07—Forming of piezoelectric or electrostrictive parts or bodies on an electrical element or another base
  • 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
  • H10N30/076—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 by vapour phase deposition
• • H—ELECTRICITY
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  • H10N30/00—Piezoelectric or electrostrictive devices
  • H10N30/01—Manufacture or treatment
  • H10N30/07—Forming of piezoelectric or electrostrictive parts or bodies on an electrical element or another base
  • 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
  • H10N30/079—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 using intermediate layers, e.g. for growth control
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10N30/00—Piezoelectric or electrostrictive devices
  • H10N30/20—Piezoelectric or electrostrictive devices with electrical input and mechanical output, e.g. functioning as actuators or vibrators
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
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  • H10N30/00—Piezoelectric or electrostrictive devices
  • H10N30/80—Constructional details
  • H10N30/85—Piezoelectric or electrostrictive active materials
  • H10N30/853—Ceramic compositions
  • H10N30/8542—Alkali metal based oxides, e.g. lithium, sodium or potassium niobates
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  • H10N30/00—Piezoelectric or electrostrictive devices
  • H10N30/80—Constructional details
  • H10N30/87—Electrodes or interconnections, e.g. leads or terminals
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  • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
  • C01G31/00—Compounds of vanadium
  • C01G31/02—Oxides
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  • C01—INORGANIC CHEMISTRY
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  • C01—INORGANIC CHEMISTRY
  • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
  • C01G35/00—Compounds of tantalum

Definitions

• the present invention relates to a method for manufacturing a monocrystalline layer, in particular a piezoelectric layer, in particular for application to a microelectronic, photonic or optical device.
• said device may be a surface acoustic wave device or a volume acoustic wave device for radiofrequency applications.
• SAW Surface Acoustic Wave
• Surface acoustic wave filters typically comprise a thick piezoelectric layer (that is to say generally of several hundred ⁇ thickness) and two electrodes in the form of two interdigitated metal combs deposited on the surface of said piezoelectric layer .
• An electrical signal typically a voltage variation, applied to an electrode is converted into an elastic wave propagating on the surface of the piezoelectric layer. The propagation of this elastic wave is favored if the frequency of the wave corresponds to the frequency band of the filter. This wave is again converted into an electrical signal by reaching the other electrode.
• Volume acoustic wave filters typically comprise a thin piezoelectric layer (that is to say a thickness generally substantially less than 1 ⁇ ) and two electrodes arranged on each major face of said thin layer.
• An electrical signal typically a voltage variation, applied to an electrode is converted into an elastic wave that propagates through the piezoelectric layer. The propagation of this elastic wave is favored if the frequency of the wave corresponds to the frequency band of the filter. This wave is again converted into an electrical signal by reaching the electrode on the opposite side.
• the piezoelectric layer must have excellent crystalline quality so as not to cause attenuation of the surface wave. In this case, therefore, a monocrystalline layer will be preferred.
• suitable materials used industrially are quartz, LiNb0 3 or LiTa0 3 .
• the piezoelectric layer is obtained by cutting an ingot of one of said materials, the precision required for the thickness of said layer being insignificant insofar as the waves must propagate essentially on its surface.
• the piezoelectric layer In the case of volume acoustic wave filters, the piezoelectric layer must have a determined and uniform thickness over the entire layer in precisely controlled manner. On the other hand, the crystalline quality being secondary to the criteria of importance for the performance of the filter, compromises are currently made on the crystalline quality of said layer and a polycrystalline layer has long been considered acceptable.
• the piezoelectric layer is thus formed by deposition on a support substrate (for example a silicon substrate).
• a support substrate for example a silicon substrate.
• the materials used industrially for such a deposit are AIN, ZnO and Pb (Zr x , Ti 1-x ) 03 (PZT).
• the choice of a material results from a compromise between different properties of the filter, depending on the specifications of the filter manufacturer.
• the electromechanical coupling coefficient of the piezoelectric materials are criteria for choosing the material to be used for a given application and a given component architecture.
• LiNbO 3 and LiTaO 3 are highly anisotropic materials. Since the coupling coefficient depends on the crystalline orientation, the choice of a particular orientation of the material offers a first degree of freedom in the choice of material. This is the reason why one can find substrates according to a multiplicity of crystalline orientations, for example, and according to an Anglo-Saxon terminology: X-cut, Y-cut, Z-cut, YZ-cut, 36 ° rotated Y axis, 42 ° rotated Y axis, ...
• An object of the invention is to overcome the aforementioned drawbacks and in particular to design a method for manufacturing a monocrystalline layer, in particular a piezoelectric layer, in particular for a surface acoustic wave device, other materials than the materials used for this application, in particular by making it possible to obtain thin layers (that is to say thickness less than 20 ⁇ , or even less than 1 ⁇ ) and uniform materials used for surface acoustic wave devices. Moreover, this method must also make it possible to use a greater variety of support substrates than in existing volume acoustic wave devices.
• a method of manufacturing a monocrystalline layer characterized in that it comprises the following successive steps:
• A is at least one of Li, Na, K, H;
• B is at least one of: Nb, Ta, Sb, V;
• seed layer of the donor substrate on the receiving substrate by bonding the donor substrate on the receiving substrate so that the seed layer is at the bonding interface and then thinning of the donor substrate until said seed layer;
• a ' consists of at least one of Li, Na, K, H;
• B ' consists of at least one of the following: Nb, Ta, Sb, V;
• a ' is different from A or B' is different from B.
• layer located at the bonding interface is meant a layer located on the side of the face of a first substrate which is bonded to a second substrate but does not necessarily imply direct contact between said layer and the second substrate .
• said layer can be glued directly to the second substrate or be covered with a bonding layer, for example dielectric, or any other type of layer, through which the bonding takes place.
• A is different from A is meant that A and A 'consist of different elements and / or the same element (s) but in different stoichiometric proportions.
• a ' comprises at least one element in common with A, and / or B' comprises at least one element in common with B.
• A comprises at least one element in common with A ", it is understood that the same element (or several elements) is at the same time in A and in A ', in identical or different stoichiometric proportions.
• a ' is identical to A when B' is different from B
• B ' is identical to B when A is different from A.
• a ' is identical to A is meant that A' and A are made of the same element or elements and in the same stoichiometric proportions.
• A consists of a single element and B consists of a single element.
• the transfer of the seed layer comprises the following steps:
• part of the thickness of the transferred seed layer can be removed on the receiving substrate.
• the thickness of the seed layer is less than 2 ⁇ , preferably less than 1 ⁇ .
• the receiving substrate is advantageously of semiconductor material, and comprises an intermediate charge trapping layer located between the seed layer and the receiving substrate.
• Another subject of the invention relates to a method for manufacturing a monocrystalline layer, characterized in that it comprises the following successive steps:
• a ' consists of one or more of Li, Na, K, H;
• B ' consists of one or more of the following: Nb, Ta, Sb, V;
• A consists of one or more of the following: Li, Na, K, H;
• B "consists of one or more of the following: Nb, Ta, Sb, V;
• epitaxial growth is carried out on said composition material A “B” O 3 , a monocrystalline layer of composition A "'B'"0 3 , where
• a '" consists of one or more of Li, Na, K, H;
• B ' consists of one or more of the following: Nb, Ta, Sb, V.
• a '" is different from A" or B' "is different from B".
• the transfer of said at least a part of the epitaxial layer of composition A "B" O 3 onto the receiving substrate comprises the following steps:
• the weakening zone is formed in the donor substrate and, after the transfer step, the transferred layer is thinned so as to expose the composition material A "B" O 3 .
• a "is different from A 'or B" is different from B'.
• A “comprises at least one element in common with A ', and / or B" comprises at least one element in common with B'.
• A is the same as A 'when B" is different from B'
• B is the same as B 'when A” is different from A'
• a ' consists of a single element and B' consists of a single element.
• the weakening zone is formed by ion implantation in the donor substrate.
• the thickness of the monocrystalline layer of composition A "B" O 3 is between 0.2 and 20 ⁇ .
• At least one electrically insulating layer and / or at least one electrically conductive layer may be formed at the interface between the receiving substrate and the donor substrate.
• said method comprises transferring at least a portion of the monocrystalline layer of the receiving substrate to a final substrate.
• a substrate for a microelectronic, photonic or optical device characterized in that it comprises a support substrate and a monocrystalline layer of composition A "B" O 3 on said support substrate, where
• A consists of one or more of the following: Li, Na, K, H;
• B "consists of one or more of the following: Nb, Ta, Sb, V;
• At least one of A "and B" consists of at least two elements
• composition A'B'0 3 a layer of composition A'B'0 3 , where
• a ' consists of at least one of: Li, Na, K, H, and
• B ' consists of at least one of: Nb, Ta, Sb, V,
• said substrate further comprises, on the composition layer A "B” O 3 , a monocrystalline layer of composition A "B '" O 3 , where
• a '" consists of one or more of Li, Na, K, H;
• B ' consists of one or more of the following: Nb, Ta, Sb, V.
• Another object relates to a method for manufacturing a surface acoustic wave device comprising the deposition of electrodes on the surface of a monocrystalline piezoelectric layer, characterized in that it comprises the manufacture of said piezoelectric layer by a method such as as described above.
• Another object relates to a surface acoustic wave device characterized in that it comprises a monocrystalline piezoelectric layer that can be obtained by a method as described above, and two electrodes appearing on the surface of said monocrystalline piezoelectric layer. .
• Another object relates to a method for manufacturing a volume acoustic wave device comprising depositing electrodes on two opposite faces of a monocrystalline piezoelectric layer, characterized in that it comprises the fabrication of said piezoelectric layer by a method as described above.
• Another object relates to a bulk acoustic wave device, characterized in that it comprises a monocrystalline piezoelectric layer that can be obtained by a method as described above, and two electrodes arranged on two opposite faces of said piezoelectric layer. monocrystalline.
• Another object of the invention relates to a micro-sensor adapted to measure a deformation generated by an external stress, characterized in that it comprises a monocrystalline piezoelectric layer that can be obtained by a method described above.
• Another object of the invention relates to a micro-actuator adapted to generate a deformation of an element or a displacement of a moving part by the application of a continuous or variable electric field, characterized in that it comprises a diaper piezoelectric monocrystalline obtainable by a method described above .
• FIG. 1 is a principle view in section of a surface acoustic wave filter
• FIG. 2 is a basic sectional view of a volume acoustic wave filter
• FIGS. 3A to 3E illustrate successive steps of a method for manufacturing a monocrystalline layer according to a first embodiment of the invention
• FIGS. 4A to 4E illustrate successive steps of a method of manufacturing a monocrystalline layer according to a second embodiment of the invention
• FIG. 4F illustrates an additional step implemented in a variant of the embodiment illustrated in FIGS. 4A to 4E;
• FIGS. 5A to 5C illustrate subsequent optional steps of said method.
• the elements illustrated are not necessarily represented on the scale.
• the elements designated by the same reference signs in different figures are identical.
• Figure 1 is a basic view of a surface acoustic wave filter.
• Said filter comprises a piezoelectric layer 10 and two electrodes 12, 13 in the form of two interdigitated metal combs deposited on the surface of said piezoelectric layer.
• the piezoelectric layer rests on a support substrate 1 1.
• the piezoelectric layer 10 is monocrystalline, an excellent crystalline quality being indeed necessary not to cause attenuation of the surface wave.
• Figure 2 is a basic view of a volume acoustic wave resonator.
• the resonator comprises a thin piezoelectric layer (that is to say a thickness generally less than 1 ⁇ , preferably less than 0.2 ⁇ ) and two electrodes 12, 13 arranged on either side of said piezoelectric layer. 10 which, thanks to the manufacturing method according to the invention, is monocrystalline.
• the piezoelectric layer 10 rests on a support substrate 1 1.
• a Bragg mirror 14 is interposed between the electrode 13 and the substrate 1 1. Alternatively (not shown), this insulation could be achieved by providing a cavity between the substrate and the piezoelectric layer.
• the invention proposes the formation of the monocrystalline layer, in particular piezoelectric layer, by means of an epitaxy on a material of a donor substrate, serving as seed for epitaxy, until obtaining the desired thickness for the monocrystalline layer, and a transfer to a recipient substrate, said transfer being able to be carried out before the epitaxy (in which case a surface layer of the donor substrate, called the seed layer, is transferred to the receiving substrate) or after epitaxy (in which case at least a part of the epitaxial layer is transferred to the receiving substrate).
• the donor substrate may be a solid monocrystalline substrate of the material under consideration.
• the donor substrate may be a composite substrate, that is to say formed of a stack of at least two layers of different materials, a surface layer is made of the monocrystalline material considered.
• the piezoelectric materials of particular interest are the perovskite and assimilated materials of structure AB0 3 .
• the interest that can be brought to these materials is not limited to their piezoelectric character.
• A consists of one or more of the following among: Li, Na, K, H, and B consists of one or more of: Nb, Ta, Sb, V.
• the receiving substrate has a function of mechanical support of the seed layer. It can be of any kind adapted to the implementation of epitaxy (especially in terms of temperature resistance) and, advantageously but not imperatively, adapted to the intended application. It can be massive or composite.
• At least one intermediate layer may be interposed between the receiving substrate and the seed layer.
• such an intermediate layer may be electrically conductive or electrically insulating.
• the skilled person is able to choose the material and the thickness of this layer depending on the properties it wishes to confer on the radiofrequency device intended to understand the piezoelectric layer.
• the receiving substrate may be of semiconductor material. It may be for example a silicon substrate.
• This conductive material comprises a trap-rich intermediate layer (which can be translated into French as a "charge trap” layer), which can be either formed on the receiving substrate or formed on the surface of the substrate. recipient.
• Said trap-rich intermediate layer is thus located between the seed layer and the receiving substrate and improves the electrical insulation performance of the receiving substrate.
• Said trap-rich intermediate layer may be formed by at least one of the polycrystalline, amorphous or porous materials, in particular polycrystalline silicon, amorphous silicon or porous silicon, without being limited to these materials.
• the method comprises a transfer of the seed layer of a donor substrate onto a support substrate, followed by the aforementioned epitaxial step.
• the material of the seed layer is advantageously a material of composition AB0 3 , where A consists of at least one of: Li, Na, K, H, and B consists of at least one of : Nb, Ta, Sb, V.
• each of A and B consists of a single element.
• the epitaxial layer advantageously has a composition different from the composition of the seed layer, of the type A'B'0 3 where A 'consists of one or more of the following elements: Li, Na, K, H; B 'consists of one or more of the following: Nb, Ta, Sb, V; A is different from A or B 'is different from B.
• A'B'0 3 can have the formula Li ⁇ K ⁇ X2 Nb y2 Tai -y2 0 3 , where 0 ⁇ x2 ⁇ 1 and 0 ⁇ y2 ⁇ 1 and where x2 is different from x1 or y2 is different from y1.
• such a composition is called ternary; in the case where the total number of elements constituting A and B 'is equal to 4, such a composition is called quaternary.
• ternary or quaternary materials are not, except exception, obtained by drawing an ingot but must be obtained by epitaxy on a suitable support to be of sufficient quality to the desired dimensions.
• compositions AB0 3 and AB'0 3 above wherein A 'comprises at least one element in common with A, and / or B' comprises at least one element in common with B, this element in common being advantageously predominantly in the composition of A or B. More preferably, the compositions AB0 3 and A'B'0 3 above in which A 'is identical to A when B' is different from B, and B 'is identical to B when A 'is different from A.
• A' may be substantially the same as A, or B 'substantially the same as B, when the content of a major element of A or B varies slightly (for example, when A is Li and A is Li 0 , 9Na 0 , i or when B is Ta 0 , 5Nb 0 , 5 and B 'is Ta 0 , 6Nb 0 , 4) -
• the epitaxial step is performed before the transfer step.
• the material of the seed donor donor substrate for epitaxy is a material of composition A'B'0 3 where A 'consists of one or more of Li, Na, K, H; B 'consists of one or more of the following: Nb, Ta, Sb, V.
• the epitaxial layer has a composition of type A "B" 0 3 where A "consists of one or more of following elements: Li, Na, K, H; B "consists of one or more of the following elements: Nb, Ta, Sb, V ..
• the seed layer has a composition Li x1 K 1-x 1 Nb y where i0 3 , where 0 ⁇ x1 ⁇ 1 and 0 ⁇ y1 ⁇ 1 and the epitaxial layer has a composition Li X2 K 1-x2 Nby 2 Tai-y 2 0 3 , where 0 ⁇ x2 ⁇ 1 and 0 ⁇ y2 ⁇ 1.
• the material of the epitaxial layer is different from that of the seed layer (in other words, A 'is different from A "or B' is different B", i.e. the above example, x1 is different from x2 or y1 is different from y2).
• composition A'B'0 3 binary and a material of composition A "B" 0 3 ternary (or more) will be preferred. More particularly, it will be preferred the compositions A'B'0 3 and A “B" 0 3 above wherein A “comprises at least one element in common with A ', and / or B" comprises at least one element in common with B ', this element in common being advantageously predominant in the composition of A or B. More preferably, one will choose the compositions A'B'0 3 and A "B” 0 3 above wherein A "is identical to A' when B "is different from B ', and B" is identical to B' when A "is different from A '.
• a ' may be substantially identical to A, or B' substantially identical to B, when the content of a major element of A or B varies slightly (for example, when A is Li and A 'is Li 0 , 9Na 0 , i or when B is Ta 0 , 5Nb 0 , 5 and B' is Ta 0 , 6Nb 0 , 4) -
• the method further comprises, after the transfer step, a resumption of epitaxy on the transferred layer, so as to form a monocrystalline layer of composition A "B" 0 3
• a '' consists of one or more of the following: Li, Na, K, H
• B '" consists of one or more of the following: Nb, Ta, Sb, V.
• the composition of said additional epitaxial layer is of Li X 3 K 1- x 3 Nb 3 Ti-y 303 type, where 0 ⁇ x 3 ⁇ 1 and 0 y y 3 1 1.
• x3 is different from x2 or y3 is different from y2 (that is, more generally, A '"is different from A" or B'"is different from B").
• the invention makes it possible in particular to form a thin layer of a compound A'B'0 3 , A "B" O 3 , or A “'B'” O 3 which has an excellent crystalline quality, at least equal to that of the solid substrates of the binary materials of this family, with a thickness controlled in a wide thickness range, and in particular for a thickness of less than 20 ⁇ , and a wide variety of properties adjusted by the composition of the material.
• the epitaxy can be carried out by any appropriate technique, in particular by chemical vapor deposition (CVD), or liquid phase epitaxy (LPE), the acronym for the English term “Liquid Phase”. Epitaxy "), pulsed laser deposition (PLD), and so on.
• CVD chemical vapor deposition
• LPE liquid phase epitaxy
• Epitaxy Epitaxy
• PLD pulsed laser deposition
• composition of the materials of the different layers is adjusted, through the choice of the constituent elements A, A, A “and / or A '" and B, ⁇ ', B “and / or B '” and their stoichiometry with regard to the properties referred to (for example, depending on the application: piezoelectric coupling factor, refractive index, etc.) but also taking into account the need to respect a coherence of the crystalline mesh parameters of the materials of the epitaxial layers and their support. epitaxy.
• the adaptation of the mesh parameters in the field of epitaxy is known to those skilled in the art.
• buffer layer in English terminology
• layers to provide selective etch stop layers may be added, in particular buffer layers ("buffer layer” in English terminology) designed to control the evolution of mesh parameters or stored stresses. or layers to provide selective etch stop layers.
• the transfer of the seed layer typically involves a step of bonding the donor substrate and the receiving substrate, the seed layer (respectively epitaxial) being located at the bonding interface, then a thinning step of the receiving substrate so as to expose the seed layer (respectively epitaxial).
• the transfer is carried out according to the Smart Cut TM process which is well known for the transfer of semiconductor thin films, in particular silicon.
• a donor substrate 100 of a material of ABO 3 binary composition is provided, and, by ion implantation (represented by the arrows), is formed.
• a weakening zone 101 which delimits a monocrystalline layer 102 to be transferred, intended to form the seed layer.
• the donor substrate 100 is represented solid but, as indicated above, it could possibly be composite.
• the implanted species are hydrogen and / or helium.
• the dose and the implantation energy of these species to form the zone of weakness at a determined depth which is typically less than 2 m: typically and always according to the material and the implanted species considered, the dose is in the range of 2 E + 16 to 2 E + 17 ionic species / cm 2 , and the implantation energy is from 30 keV to 500 keV.
• the buried embrittled layer can also be obtained by any other means known to those skilled in the art, for example by porosification of the material, or by laser irradiation.
• the donor substrate 100 thus weakened is bonded to the recipient substrate 1 10, the surface of the donor substrate through which the implantation has been performed being at the bonding interface.
• the donor substrate and / or the receiving substrate may be covered with an electrically insulating or electrically conductive layer (not shown), which will be interposed between the receiving substrate and the seed layer after the transfer.
• detachment of the donor substrate 100 is carried out along the weakening zone 101.
• Such detachment can be obtained by any means known to those skilled in the art, for example thermal, mechanical, chemical, etc.
• the remainder of the donor substrate, which may optionally be recycled, is then recovered, which makes it possible to transfer the layer 102 onto the recipient substrate 1 10.
• the layer transferred layer 102 it is possible, optionally, to remove a superficial portion of the transferred layer 102, for example by mechanical polishing and / or by chemical etching. This removal of material is intended to eliminate any defects related to implantation and detachment in the vicinity of the embrittlement zone.
• a thinned layer 102 is obtained on the receiving substrate 1 10, which will serve as a seed layer for the next epitaxial step.
• the layer transferred 102 of Figure 3C can be directly used as seed layer for epitaxy.
• a monocrystalline layer 103 of composition A'B'0 3 is grown by epitaxy on the seed layer 102, the material of the epitaxial layer 104 being different from that of the seed layer 102.
• the seed layer 102 imposes its mesh parameter and allows the growth of a monocrystalline material of good quality.
• the growth is stopped when the desired thickness for the monocrystalline layer is reached.
• the final layer 10 is formed of the stack of the seed layer 102 and the epitaxial layer 103.
• the composition of the epitaxial layer 103 may vary over its thickness, either gradually or discontinuously.
• a substrate is obtained for a surface acoustic wave device or a volume acoustic wave device, which comprises a receiver substrate 1 And a monocrystalline layer 10 on said receiving substrate 1 10.
• the layer 10 comprises:
• a second portion 103 extending from the first portion 102, corresponding to the epitaxial layer, a material of composition A'B'0 3 , said material can be at least ternary.
• This substrate is advantageously used to manufacture a surface acoustic wave device as illustrated in FIG. 1 or a volume acoustic wave device as illustrated in FIG. 2, or else other devices for microelectronics, photonics or integrated optics.
• the seed layer typically has a thickness of less than 2 ⁇ , preferably less than 1 ⁇ .
• the thickness of the epitaxial layer depends on the specifications of the device for incorporating the monocrystalline layer. In this respect, the thickness of the epitaxial layer is not limited either in terms of minimum value or maximum value. For information only, the table below gives combinations of thickness of the seed layer and the epitaxial layer:
• Figures 4 ⁇ to 4 ⁇ illustrate the main steps of the method according to the second embodiment, wherein the epitaxy is implemented before the transfer.
• a donor substrate 100 comprising a piezoelectric material of composition A'B'0 3 .
• Said donor substrate can be massive (as shown in Figure 4A) or composite; in the latter case, it comprises a surface layer of composition A'B'0 3 . This is particularly the case when said material is at least ternary, insofar as there are no ingots made of such a material.
• a monocrystalline layer 103 of composition A "B" 0 3 is produced, the material of composition A'B'0 3 serving as seed for epitaxy.
• the material of the epitaxial layer 103 may be identical to or different from the material of the donor substrate 100.
• An embrittlement zone is then formed in the donor substrate 100 or in the epitaxial layer 103 of composition A "B" O 3 so as to delimit a layer to be transferred.
• the zone of weakening can be formed by implantation of ionic species (shown schematically by the arrows in FIG. 4B).
• the weakening zone 101 is formed in the donor substrate 100, beneath the epitaxial layer 103.
• the layer to be transferred is in this case composed of the epitaxial layer 103 in its entirety and a 100 'portion of the donor substrate 100.
• the zone of weakness is formed in the layer 103.
• the layer to be transferred is in this case constituted by the portion extending between the free surface of the layer 103 and the zone of weakening. 101.
• the donor substrate is bonded to the receiving substrate 1 10, the epitaxial layer 103 of composition A "B" O 3 being at the bonding interface.
• the donor substrate 100 is detached along the embrittlement zone 101 so as to recover the remainder of the donor substrate and transfer the layer constituted by the stack 103, 100 'onto the receiving substrate 1 10.
• At least one surface portion of the transferred layer is removed. This removal aims to eliminate at least the portion 100 'and possibly a portion of the layer 103, so as to expose the composition material A "B" 0 3 .
• the layer 103 thus obtained can then be used for the manufacture of a surface acoustic wave or volume acoustic wave device.
• an additional step is carried out, illustrated in FIG. 4F, consisting of an epitaxial resumption implemented on the layer 103 of composition A "B" O 3 , so as to form a additional monocrystalline layer 104 of composition A "B '" 0 3 .
• the material of said additional layer 104 may be identical to that of the layer 103, in which case this last stage of epitaxy results in a thickening of the layer 103 (the layer 104 being schematized separately from the layer 103 only for allow to visualize, but not distinguishable in the final layer, if not by its quality).
• the additional layer 104 is of a material different from that of the layer 103.
• the thickness of the layer 103 and, if appropriate, of the layer 104, is chosen according to the specifications of the radiofrequency device intended to incorporate said layer.
• the thickness of the layer 103 is typically between 0.05 and 2 ⁇ .
• the thickness of the layer 104 is typically between 0.5 and 20 ⁇ .
• the transfer can be performed, after bonding of the donor substrate and the receiving substrate, by removal of material, for example by mechanical polishing and / or or etching the donor substrate to expose the seed layer.
• This variant is less advantageous insofar as it involves a consumption of the donor substrate, while the Smart Cut TM process allows a possible recycling of the donor substrate.
• this variant does not require implantation within the donor substrate.
• a substrate for a surface acoustic wave device or a volume acoustic wave device which comprises a substrate, is obtained.
• This substrate is advantageously used to manufacture a surface acoustic wave device as illustrated in FIG. 1 or a volume acoustic wave device as illustrated in FIG. 2, the layer 103 or, if appropriate, the set of layers 103 and 104, corresponding to the layer 10 of Figures 1 and 2, or any other microelectronic device, photonic or optical comprising a layer.
• the recipient substrate on which the epitaxial growth occurred may not be optimal for the final application. Indeed, the receiving substrate to undergo the operating conditions of epitaxy, the choice of suitable materials is limited. In particular, the receiving substrate can not contain layers or elements liable to be damaged by the epitaxial temperature. It may then be advantageous to transfer the layer 10 to a final substrate 1 1 1 whose properties are chosen according to the intended application, by bonding it on said substrate 11 1 via the surface of the epitaxial layer 103 (see Fig. 5A) (or 104 where appropriate), and removing the receiving substrate (see Fig. 5B). This transfer can be achieved by any transfer technique mentioned above.
• the seed layer 102 which was buried in the structure resulting from the epitaxy, is then exposed and can optionally be removed (see FIG. 5C), in particular in the case where it present defects. Only the epitaxial layer 103 (and, where appropriate, the layer 104) (or part of said layer) having the desired characteristics then remains on the final substrate 1 1 1.
• it is deposited on the surface of the layer 10 opposite to the receiving substrate 1 10 or, where appropriate, to the final substrate (whether the receiving substrate 1 10 or the final substrate 1 1 1, said substrate forms the support substrate denoted 1 1 in Figure 1), metal electrodes 12, 13 in the form of two interdigitated combs.
• a first electrode is deposited on the free surface of the layer 102 to be transferred from the donor substrate, this first electrode (referenced 13 in FIG. buried in the final stack.
• a second electrode is deposited on the free surface of the layer 10, opposite to the first electrode.
• Another option is to transfer the layer to a final substrate as mentioned above and to form the electrodes before and after said transfer.
• an isolation means which can be, for example, a Bragg mirror (as shown in Figure 2) or a cavity previously etched in the substrate 1 10 or in the final substrate 1 1 1 where appropriate.
• the method according to the invention makes it possible to form a monocrystalline layer that is not only binary but also ternary or quaternary and thus offers a greater choice of properties for said layer than the materials traditionally used for the devices to be used.
• acoustic wave surface or acoustic wave volume This promotes a satisfactory compromise between coupling coefficient and electromechanical efficiency of the piezoelectric material.
• micro-sensors it will usually be a measure of a deformation generated by external stress.
• micro-actuators we will seek to generate the deformation of an element or the displacement of a moving part through the application of an electric field, continuous or variable.
• the use of the piezoelectric material makes it possible to connect mechanical deformation and electrical signal.
• external stress is a pressure wave that deforms a membrane. It may be in the audible spectrum, and the objects typically referred to are the microphones (in sensor mode) and the speakers (in actuator mode).
• piezo ultrasonic microtransducers in the English terminology PMUT for Piezo Micromachined Ultrasonic Transducers. It can also be pressure sensors statics or inertial sensors (acceleration sensors, gyroscopes, etc.) for which the displacement of a moving mass set in motion by an acceleration undergone is measured thanks to the piezoelectric material.
• the piezoelectric material composes the entirety of the deformed element (membrane, beam, cantilever, etc.) or advantageously only a part of it by stacking it with other materials such as silicon for example, to better ensure the mechanical properties of the deformable part.
• the piezoelectric materials can control a very precise displacement and serve for example to expel ink from print cartridges, or microfluidic systems or to adjust a focal length of an optical microsystem.
• Electro-Optics (Diss., ETH No. 17275)

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