Multilayer structure and process of forming a multilayer structure

Abstract

In this application a multilayer structure is provided. This multilayer structure comprises a semiconductor or insulator substrate. Said substrate has a main surface. An electrode comprising a noble metal or a conductive oxide is arranged above this main surface. Above the electrode, an electroceramic layer is arranged. In the multilayer structure, an adhesion layer is arranged between the main surface of the substrate and the electrode.

Description

[0001] P2024,0579 WO N April16,2025 -1 - DescriptionMultilayer structure and process of forming a multi layerstructureThe present application relates to multilayer struc ture and aprocessofforming such a multilayerstructure.Multilayer structures or thin film structures in ge neral arewidely applied in several technical fields. Often t heycomprise electroceramic thin films. Such multilayerstructures are applied, for example in the field of high-energy capacitors, ferroelectric memories, piezoele ctricactuators such as micromirrors or inkjet printing h eads,microfluidicpumps,and piezoelectricsensorssuch as pressure sensorsare accelerometers,piezoelectric energyharvesters or electrocaloric solid-state cooling de vices,thermistors or applications where a material with h ighdielectricpermittivityisneeded.In such devices theelectroceramic thin film within the multilayer stru ctures canprovide the functionalunit.According to the state of the art such multilayer s tructuresare typically formed on or above silicon-wafer-base dsubstrates. Such wafers may comprise an oxide layer .For example, the formation of PZT films above silic on-basedsubstrates is known from Schwartz et al. ( C. R. Chimie 7,433–461, 2004). Furthermore, the following document s addressthe formation of adhesion layers above silicon-wafe r-basedsubstrates which moderate adhesion between an elect rode andthe silicon-wafer-based substrate: Shelton etal., Adv. Funct. Mater. 22,2295–2302,2012 P2024,0579 WO N April16,2025 -2 - Maederetal., Jpn. J. Appl. Phys. 37 (4A),2007–2012,1998 Halderetal.,Appl.Phys.A 87,705–708,2007However, these or similar approaches have shown thedisadvantage that the adhesion of electrodes in fun ctionalmultilayer devices including ceramic layers may sti ll beinsufficient. For example, in some cases delaminati on islikelyundercertain conditions.Accordingly, it is an object of the present inventi on toprovide an improved multilayerstructure.Accordingly, at least some of the disadvantages des cribedabove are at least partially overcome or compensate d by thesubject-matter of claim 1. Furthermore, other prefe rredembodiments or alternative embodiments are describe d in thefurtherclaims.According to a first embodiment, a multilayer struc ture isprovided. This multilayer structure comprises a sem iconductoror insulator substrate. Said substrate has a main s urface. Anelectrode comprising a noble metalora conductive oxide isarranged above this main surface. Above the electro de, anelectroceramic layer is arranged that provides a fu nction tothe multilayer structure. In the multilayer structu re, anadhesion layer is arranged between the main surface of thesubstrate and the electrode. The adhesion layer can be indirect contact with both the main surface of the su bstrateand the electrode. The adhesion layer comprises a t ransitionmetal or a transition metal oxide. The term “transi tionmetal” also includes alloys of transition metals. T he term“transition metal oxide” also includes mixed transi tion metalmixed oxides. P2024,0579 WO N April16,2025 -3 -Within this application the term "transition metal" can meanwhat is generally understood as such in the technic al field.In particular, it can at least include any transiti on metalbelonging to period 4, 5 and 6 of the periodic tabl e.Preferably here and in the following the transition metal canbe titanium, tantalum or tungsten or alloys of thes e metals.Ofthese,in particulartantalum hasbeen found by theinventors to be advantageous in several cases. In p articular,tantalum has proven to be particularly preferred to getherwith a platinum electrode asdescribed below.The inventors of the present invention have found t hattransition metal or transition-metal-oxide-based ad hesionlayers are capable of providing good adhesion betwe en asemiconductor or insulator substrate and an electro de whichcomprisesa noble metalora conductive oxide.Furthermore, the inventors have found that by using suchadhesion layers, delamination can be reduced or eve n fullyeliminated. Also, thermal stability may be improved . This canbe important, for example during the formation proc ess, asthe adhesion layer may help to prevent dewetting of theelectrode from the substrate surface during formati on of theelectroceramic layer. Also, surprisingly, the quali ty of theelectroceramiclayermaybe improved.Any type of substrate that shows semiconducting beh avior canbe understood as a semiconductor substrate. Similar ly, anytype of substrate that would be regarded as an elec tricalinsulator in the field can be regarded as an insula torsubstrate. P2024,0579 WO N April16,2025 -4 -According to an embodiment, a further electrode, wh ich may beaddressed as a top electrode, can be arranged on or above theelectroceramic layer. Accordingly, the electroceram ic layercan be arranged between the above-described electro de, whichmay be a bottom electrode,and the top electrode. According to an embodiment,the substrate can be a silicon-wafer-based substrate. As a silicon-wafer-based sub strate anysubstrate thatcan be formed from orthatincludes a siliconwafer is meant. The silicon in the silicon-wafer-ba sedsubstrate may have crystalline form or amorphous fo rm. It mayalso be doped or undoped. The silicon-wafer-based s ubstratecan be or can be made from a single crystalline sil icon waferor a polycrystalline silicon wafer. The silicon-waf er-basedsubstrate may be or may be formed from a bare silic on wafer.Also, the silicon-wafer-based substrate may compris e aportion of mainly elemental silicon and a portion w hich is,or which comprises, silicon oxide. Also, the term " silicon-wafer-based substrate" includes silicon-on-insulato r (SOI)wafers. Such SOI wafers can have several layers. Fo r example,theycan have a so-called silicon handle layerand a silicondevice layer separated by a silicon oxide buried la yer.According to an embodiment, the semiconductor or in sulatorsubstrate can be a sapphire substrate. As “sapphiresubstrate” is understood what the person ordinarily skilledin the art understands as such. A sapphire substrat e can bean aluminum-oxide-based material crystallized in th ehexagonalcrystalstructure.According to another embodiment, a semiconductor or insulatorsubstrate can be a glass substrate. Here any type o f silicon-oxide-based glass can be understood as a glass subs trate. P2024,0579 WO N April16,2025 -5 - With the above-described examplesofsemiconductor orinsulator substrates, multilayer structures can eas ily beformed in industrially available high quantities. H owever,adhesion of electrodes selected from noble metals o rconductive oxidescan be pooron such substrates.Accordingly, an adhesion layer comprising a transit ion metalor transition metal oxide can provide or improve ad hesionhere.In particular, the inventors found that electrode m aterialsoften cannot be placed on pure silicon, for example , aschemical exchange, such as diffusion may take place andaffect the properties of the substrate or the elect rode. Incase that the electrode material is placed on an ox idizedwafer, i.e. on silicon oxide, the adhesion often is very poorand delamination is likely. The adhesion layer acco rding tothe invention can help to improve the adhesion and mayreducediffusion of substances or atoms, as is explained b elow inmore detail. According to an embodiment,the adhesion layercan comprise afirst adhesion sublayer and a second adhesion subla yer. Thestacking orderofthese sublayersisgenerallynot limited.According to an embodiment, the first adhesion subl ayercomprises a transition metal and the second adhesio n sublayercomprises a transition metal oxide. The inventors a ssume thathaving both a transition metal and a transition met al oxidecan not only improve the adhesion or help to reducedelamination, but also may help to reduce the diffu sion ormigration ofchemicalelementsbetween the layers.Furthermore, the inventors believe that the thermal stability P2024,0579 WO N April16,2025 -6 -of the noble metal electrode can be improved. Accor dingly,the electroceramic layer can be protected from elem entsdiffusing out of the substrate into the electrocera mic layer.Likewise and vice versa, the properties of the subs trate, inparticular in the case of a semiconductor substrate , remainmainlyunaffected asno materialdiffusesfrom the electroceramiclayerinto the substrate.In the above-described embodiment, where there is a firstadhesion sublayer and a second adhesion sublayer, t hetransition metal of the first adhesion sublayer can be thesame as or different from the transition metal whic hconstitutes the transition metal oxide of the secon d adhesionsublayer, i.e. in this case the transition metal of thetransition-metal-oxide-based second adhesion sublay er may bea different transition metal to that comprised in t he firstadhesion sublayer.Alternatively, according to an embodiment, both the firstadhesion sublayerand the second adhesion sublayer can bemetallic. In this case, the transition metal of the firstadhesion sublayer is different to the one of the se condadhesion sublayer.Also alternatively, according to an embodiment, bot h thefirst adhesion sublayer and the second adhesion sub layer cancomprise a transition metal oxide. In this case, th etransition metalofthe firstadhesion sublayeris different to the one ofthe second adhesion sublayer.According to an even more generalized embodiment, t headhesion layermayhave n sublayerswith n ≥ 2.Each ofthesublayers comprises a transition metal. layer may b e either P2024,0579 WO N April16,2025 -7 -metallic or comprise the transition metal as a tran sitionmetal oxide. The above features discussed for a fir st and asecond sublayer also apply to an adhesion layer wit h morethan two sublayers.According to an embodiment, the first adhesion subl ayercomprising the transition metal in metallic form ca n be indirectcontactwith the substrate.Above oron top ofit,the second adhesion sublayercomprising the transition metaloxide can be arranged. According to another embodim ent, areverse stacking can be realised, in which the seco ndadhesion sublayer having the transition metal oxide isarranged directly on the substrate and the first ad hesionsublayer having a transition metal is arranged abov e it. Alsoembodiments with similar construction that have mor e than onemetallicsublayerwith differenttransition metals instead ofthe first sublayer can be formed. Also, embodiments withsimilar construction that have more than one transi tion-metal-oxide-based sublayer with different transitio n metalsinstead ofthe second sublayercan be formed.According to another embodiment, the first adhesion sublayercomprising the transition metal is arranged directl y on thesubstrate as described before. Above it a second ad hesionsublayer comprising the transition metal oxide is a rranged.In addition, a third adhesion sublayer again compri sing atransition metal can be arranged above the second a dhesionsublayer.Therebya three-layered structure can be found inwhich the oxide containing second adhesion sublayer issandwiched by the first and the third sublayer comp rising thetransition metal. In some cases, a structure having thesethree adhesion sublayers can be particularly advant ageous.The inventors found that possibly the first and thi rd P2024,0579 WO N April16,2025 -8 -adhesion sublayers may provide improved adhesion an d / orimproved thermal stability. The second adhesion sub layercomprising the oxide may help to provide improved s uppressionof diffusion of elements between the layers. Accord ing toanotherembodiment,the reverse structure can also be formed,in which a transition-metal-based metallic adhesion sublayeris sandwiched by two transition-metal-oxide-based a dhesionsublayers. Again, embodiments with similar construc tion thathave more than one metallic sublayer with differenttransition metals instead of the first sublayer can beformed. Also, embodiments with similar construction that havemore than one transition-metal-oxide-based sublayer withdifferent transition metals instead of the second s ublayercan be formed. Also, embodiments with similar const ructionthat have more than one metallic sublayer with diff erenttransition metals instead of the third sublayer can beformed.According to an embodiment, the thickness of the ad hesionlayercan be between 1 and 100 nm.More preferably itcan bebetween 10 and 50 nm. Even more preferably it can b e between15 and 100 nm, such as between 15 and 50 nm or betw een 15 and30 nm.The inventorsofthe presentinvention have found thatin the case that the adhesion layer is too thin, de laminationmay be more likely and diffusion-inhibiting propert ies mayalso be reduced. In particular for thicknesses abov e 10 nm,the above-described adhesion properties and the dif fusionreduction properties are particularly preferable. I n casethat sublayers are realized, each sublayer may have athickness of 1 to 50 nm or preferably of 1 to 25 nm .As described above, the electrode comprises or cons ists of anoble metalora conductive oxide.A "noble metal" can be P2024,0579 WO N April16,2025 -9 -understood in the sense of what is understood in th e field.Within this application the term noble metal also i ncludesalloys of noble metals. Noble metals may at least b eunderstood as ruthenium, rhodium, palladium, silver , osmium,iridium,platinum and gold,forexample.Ofthese, iridiumand platinum have been found to be particularly adv antageousaselectrodes.In particular,the combination with tantalum- comprising adhesion layershasbeen found to workparticularly well. In particular for Ir and even mo re for Ptas material for the electrodes the above said conce rning theexchange ofsubstanceson bare Si-surfacesand the verypooradhesion to silicon oxide surfaces holds true. Thus theadhesion layer and in particular one using Ta is pr eferred.According to anotherembodiment,the electrode can comprise aconductive oxide. In principle any conductive oxide may beused. It may be an oxide of a metal. Examples for p referredconductive oxides are iridium oxide, rhodium oxide, rheniumoxide,ruthenium oxide,lanthanum nickeloxide,or strontiumruthenium oxide. Chemical formulars for these oxide s may beIrO 2, RhO 2, ReO 2, RuO 2, SrRuO 3, yet generally the elementalratios are not limited to the ones in the formulas. It hasbeen found thatthe above-described adhesion layer can provide particularlygood adhesion to insulatoror semiconductor-based substrates.According to an embodiment, the thickness of the el ectrodecan be between 50 nm and 500 nm.In particular,in the caseof more expensive noble metals a lower thickness ma y bepreferred, such as between 100 nm and 300 nm or suc h asbetween 150 to 250 nm. In addition, electrode layer s that aretoo thick tend to delaminate due to internal stress es. P2024,0579 WO N April16,2025 -10 - In thisapplication an electroceramiclayercan be understoodin the general technical meaning. It is preferred t hat theelectroceramic provides a functionality to the mult ilayerstructure.Such a functionalitymaybe:• High dielectric permittivity, which may be used i ncapacitorsforexample;• Pyroelectricity, which may be used in infrared se nsorsforexample;• Ferroelectricity which may be used in memories fo rexample;• Piezoelectricity, which may, for example, be used in thedevices described at other points in the applicatio n;• Temperature-dependent resistance; this may be pro videdvia thermistor ceramic materials, such as materials withpositive temperature coefficient (PTC) or materials withnegative temperature coefficient(NTC).According to an embodiment, the electroceramic mate rial inthe multilayer structure can comprise a piezoelectr ic ceramicmaterial or consist of such. The inventors of the p resentinvention have found that the above setup, having a noblemetalorconductive-oxide-based electrode which is adhered to a semiconductororinsulator-based substrate byan adhesionlayer, can be used to produce high quality piezoele ctric thinfilmsin these multilayerstructures. The following piezoelectricceramicmaterialshave been foundto be preferred: Pb[Zr xTi 1−x]O3 (abbreviated PZT), (1− x)Pb[Mg1 / 3 Nb2 / 3 O3] – x PbTiO 3 (abbreviated PMN-PT), [K xNa1−x]NbO3(abbreviated KNN), (1− x) BiFeO 3 – x BaTiO 3 (abbreviated BFO-BT), Ba[Zr xTi 1−x]O3 (abbreviated BZT) (1- x)[Bi 1 / 2 Na1 / 2 ]TiO 3 - x[Bi 1 / 2 K1 / 2 ]TiO 3 (abbreviated BNT-BKT), (1- x) BiFeO 3 – x P2024,0579 WO N April16,2025 -11 -Ba[Ti yZr 1-y ]O3 (abbreviated BFO-BZT), AlMgZrN, or [Al xSc1-x ]N.In all of these examples, x and y are a number betw een zeroand one,i.e.0 ≤ x ≤ 1 and 0 ≤ y ≤ 1.The above-listedelectroceramic materials can be modified by doping. Doping isunderstood as the intentional addition of impuritie s to tunethe electric and / or piezoelectric properties of theelectroceramiclayer.According to an embodiment, the electroceramic laye r maycomprise or consist of two or more electroceramic s ublayers.The electroceramic sublayers may correspond with th esublayers or the partial layers described with resp ect to thedeposition processand maybe the directresultof suchdeposition, however the electroceramic sublayers he re are notlimited to that. One electroceramic sublayer is str ucturallyor chemically different from a neighboring sublayer . Forexample, two sublayers may have a different functio nality,for example by comprising a different electrocerami cmaterial. However, more preferably two sublayers ar e based onor comprise the same electroceramic material, but h ave adifferent structure or different chemical compositi on. Forexample, both materials can be a PZT-based material , but havedifferent composition. For example, components such asdopants or main ions such as La, Pb, Zr or Ti may h avedifferent concentrations in both sublayers. The sam e holdstrue foranyofthe above-described materials.According to an embodiment, the piezoelectric ceram icmaterial can be directly in contact with the electr ode.According to an alternative embodiment, a support l ayer canbe applied between the electrode and the electrocer amiclayer.The supportlayercan provide a supporting P2024,0579 WO N April16,2025 -12 -functionality. For example, it may be layer of or t hatcomprises a conductive material. It may thus facili tatecharge transport or application of voltage form the electrodeto the electroceramic layer. Alternatively or addit ionally itmay provide a buffer-function, which may reduce che micalexchange between the electrode and the electroceram ic layer.Also, the support layer may have a functionality th at aids incrystal growth or aids in oriented crystal growth o f theelectroceramic layer. In particular in this case th e supportlayer can be addressed as a seed layer that is arra ngedbetween the electroceramic layer, and the electrode . Supportlayer materials in general and seed layer materials inparticularcan,forexample,be selected from lead titanate(PbTiO 3), lanthanum nickel oxide (LaNiO 3), lead oxide (PbO)or titanium oxide (TiO 2).According to an embodiment, an electroceramic layer cancomprise a ceramic material to realize one of the a bovelisted functionalities. The inventors of the presen tinvention have first observed the advantages of the inventiveconstruction using an adhesion layer for piezoelect ricmaterials as described above. The inventors have fo und totheir surprise that generally any electroceramic la yer mayprofit from such a construction. In particular, the inventorshave found that thermistor materials also show impr ovedproperties when the above-described construction ha ving anadhesion layer between a bottom electrode and the s ubstratebelow isused.Accordingly, according to an embodiment the electro ceramiclayer can consist of or comprise a thermistor mater ial. Ofthe materials having temperature-dependent resistiv ity inparticular, the following have been found to be adv antageous: P2024,0579 WO N April16,2025 -13 -Ni-Mn-Cu oxides, Ni-Mn-Co oxides, Co-Fe oxides, Cr- Co-Ba-Fe-Bi oxides, barium titanate (BaTiO 3). According to anembodiment, the thermistor materials can have a spi nel-basedstructure orperovskite structure.Generally, the thickness of the electroceramic laye r is notlimited and can be chosen depending on the applicat ion.According to an embodiment, the electroceramic laye r can havea thicknessof10 nm to 20 µm.Preferably,a lower range forthe thickness can be 20 nm, 50 nm or 100 nm. Prefer ably, anupperrange ofthe thicknesscan be 10 µm,5 µm,2 µm or1µm. For example, a thickness may be 100 nm to 5 µm, such as 1µm to 3 µm or 1.7 - 2.5 µm. The above mentioned val ues forthe lowerand the higherrange can each substitute the lower and the highervalue in allthese given examples.According to an embodiment, the thickness of the su pportlayer is considerably thinner than that of the elec troceramiclayer.The inventors have found that having the above-desc ribedstructure, and in particular having an adhesion lay er, canimprove the quality of the electroceramic layer. Inparticular, according to an embodiment the electroc eramiclayercan have crystalgrainsin the size range of 10 to 1000 nm.Also, according to a further embodiment, the adhesi on layermay help to form high quality electroceramic layers inparticular with crystalline columns that extend ove r theentire thicknessofthe electroceramiclayer. P2024,0579 WO N April16,2025 -14 - According to anotherembodimentthe electroceramic layercanhave a granular structure. For example, grains of 1 0 nm to 1µm can be present.Such granularstructure mayfor example berealized by electroceramic layers formed with bariu m titanateorMn-Co-Nioxide. According to an embodiment,a multilayerstructure isdescribed which may have the above-described arrang ement. Inaddition it may have a second electrode that is arr anged on asecond main surface of the substrate. The second ma in surfacemay be a surface opposite to the first main surface describedabove.A second adhesion layerisarranged between the secondmain surface and the second electrode. The second a dhesionlayer can have the above-described properties for t he firstadhesion layer. Accordingly, in its layering a symm etricalmultilayerstructure can be formed.Preferably, the first and the second adhesion layer can havethe same material, as this can simplify manufacturi ng.However,the materialsmayalso differ.Similarly, theelectrodes can comprise the same material on both s ides,which can be preferred due to simplified manufactur ing. Alsoin this case the materials of the electrodes may di ffer.According to an embodiment, also in this case a sec ondelectroceramic layer can be positioned above the se condelectrode. The electroceramic layer may have the ab ove-described properties. It may be the same or also di fferentthan the firstelectroceramiclayer.The present invention is particularly suited for fo rming suchsymmetrical structures, as this further helps to in crease the P2024,0579 WO N April16,2025 -15 -yield. Also some advantages due to simplified handl ing can beachieved for rougher surfaces, that are described b elow.According to another embodiment, which may be combi ned withany of the above embodiments, the multilayer struct ure canhave a further electrode arranged on the electrocer amiclayer. This electroceramic layer can be addressed h ere asfirst electroceramic layer. The further electrode d escribedhere can be addressed asa firsttop electrode.According to a modification of the previous embodim ent afurther electroceramic layer, which may be describe d oraddressed here as a second electroceramic layer, ca n bearranged on or above the first top electrode. The a bove-described properties can apply here for the further electrodeand for the further electroceramic layer. The mater ial of thefurther electroceramic layer can be the same as tha t of thelower or first electroceramic layer. It may also be differentdepending on the application.In a similarmanner, also theelectrode may have the same material as the other e lectrode,but it may also differ. On top of the stacking, a f urther topelectrode can be arranged. Accordingly, a setup wit h thesubstrate, the adhesion layer, the bottom electrode the firstelectroceramiclayer,the firsttop electrode,the secondelectroceramic layer and the second top electrode i sprovided. In a similar manner, several layers of el ectrodesand electroceramic layers can be stacked one upon a nother. Itis preferred that such stacks are terminated by a t opelectrode.According to an embodiment, the multilayer structur eaccording to the presentinvention can be used in micromirrors.In thiscase itisadvantageousthat the P2024,0579 WO N April16,2025 -16 -electroceramic layer comprises a piezoelectric mate rial. Inthis case the deflection of the mirror can be drive n with thepiezoelectric multilayer structures. Alternatively, theinvention can be used in high energycapacitors,ferroelectric memories, piezoelectric actuators suc h asmicromirrors, microfluidic pumps or inkjet printing heads. Itcan be used in piezoelectric sensors such as pressu re sensorsoraccelerometers.Furthermore,itcan be used inpiezoelectric energy harvesters or electrocaloric s olid statecooling devices.In principle,itcan also be used in any type ofotherpiezoelectricdevice.According to an embodiment, the main surface of the substratecan be polished or even mirror polished. A mirror p olishedsurface can have a surface roughness (R a) of below 20 nm.Having a mirror polished surface can increase the y ield ofthe functional devices formed with the multilayer s ubstrate.These mirror polished substrates are most preferabl y siliconsubstrateswith a mirrorpolished surface.However, the inventors found that due to the adhesi on layerhighly polished surfaces are not necessary in all c ases. Theinventors found that substrates with a roughness (R a) of upto 2 µm maybe used.The inventorshave found that therebytime-intensive polishing can be avoided by using an adhesionlayer. More preferably, the surface roughness is ma ximum 1µm. Any roughness below this 2 µm, or more preferab ly below 1µm, is technically accessible by the invention. Unp olished oronly partially smoothed can have a surface roughnes s of above10 nm or above 20 nm or even above 50 nm or 100 nm.Accordingly a surface roughness of between 10 nm to 2 µm suchas for example 20 nm to 1 µm works well with the in vention.The above other values can replace the upper and lo wer value, P2024,0579 WO N April16,2025 -17 -respectively. Also for rough surfaces, the inventor s havefound that by using an adhesion layer the quality o f theelectroceramic film can be exceptionally high. In g eneral,polishing is a complicated and expensive process. I naddition, it can also introduce impurities that maydeteriorate the performance as well as yield of the devices.Accordingly this aspect may help to overcome such i ssues.According to a further embodiment, a process of for ming amultilayer structure is described. For the process, theabove-described advantages apply mutatis mutandis a s far asapplicable.In an embodiment of the process of forming a multil ayerstructure, first an adhesion layer is arranged on a mainsurface of a semiconductor-based or insulator-basedsubstrate. The adhesion layer can be deposited on t hesubstrate. Preferably, the adhesion layer is formed via aphysical vapor deposition such as for example magne tronsputtering or evaporation. A bottom electrode containing anoble metal or a conductive oxide is arranged on th e adhesionlayer. The bottom electrode can be arranged or depo sited byany means. Preferably, chemical vapor deposition or physicalvapor deposition such as, for example, magnetron sp utteringor evaporation can be used. An electroceramic mater ial issubsequently deposited on top of the bottom electro de. Theelectroceramic materials can, for example, be the a bove-defined electroceramic materials. In order to depos it theelectroceramic material, for example chemical solut iondeposition magnetron sputtering, atomic layer depos ition orpulsed laserdeposition maybe applied. P2024,0579 WO N April16,2025 -18 -The electroceramic layer may, for example, be depos itedsubsequently in thin layers. For example, layers wi th athickness of 10 to 200 nm per deposition step may b e stackedupon another.Forexample,in the case ofchemical solutiondeposition, first a precursor solution comprising a nelectroceramic material precursor can be deposited. Thedeposition method can be, for example, spin coating .Subsequently the solvents from the precursor soluti on can beremoved by drying at elevated temperature. Subseque ntly, anyorganic residues can be removed by a pyrolysis step . Thedrying and pyrolysis may be performed in succession to eachother at different temperatures or during one heati ng sweep.Subsequently,an annealing step,which leadstocrystallization of the previously amorphous metal o xide, canbe performed. In order to achieve an electroceramic layer inthe orderofseveralmicrometerssuch a deposition can be repeated.According to an embodiment, a high quality PZT film can beformed by depositing and spin coating a solution of PZT onthe substrate.The PZT film can be formed from one solution creating one partiallayerofthe PZT film.Itcan be createdalso from two or more solutions of different PZT-co mponentconcentrations, from which sublayers of a partial l ayer areformed. One solution can be Zr-rich and a second so lution canbe Ti-rich. The principles of the embodiment explai ned nextmay applyto the casesoftwo ormore solutions. According to an embodimenta processwith atleast three deposition stepscan be applied.Therein,atleast a firstsublayer is produced using a first solution. A seco ndsublayer is deposited or arranged above the first s ublayerusing a second solution and a third sublayer is pro duced P2024,0579 WO N April16,2025 -19 - using a third solution thatisdeposited above the secondsublayer. The electroceramic material for this appr oach ispreferably PZT or it comprises PZT. The first solut ioncomprises a high zirconium to titanium ratio in thi s case.The first solution is deposited above the bottom el ectrode,forming the first sublayer. The formation of the fi rstsublayer can be via one or several deposition steps .Subsequently, the first sublayer is annealed. If mo re thanone deposition is performed, intermediate annealing can beperformed. Likewise, from the second solution, whic hcomprises a medium zirconium to titanium ratio, a s econdsublayer is formed. The medium zirconium to titaniu m ratio isa ratio which has a lower zirconium to titanium rat io thanthat of the first solution. After deposition, annea ling canbe performed. Above the second sublayer, a third su blayer isformed again possibly having one or several layers. The thirdsublayer is formed using a third solution comprisin g a smallzirconium to titanium ratio which means that the am ount ofzirconium in relation to the titanium islowestin comparisonto the other solutions. In other words, the first s olutioncan be addressed as zirconium-rich. The second solu tion canbe addressed as morphotropic phase boundary solutio n and thelast solution can be addressed as a titanium-rich s olution.The formed sublayers can be addressed as zirconium- richsublayer, as morphotropic phase boundary sublayer a nd astitanium-rich sublayer.This approach has the advantage that during anneali ng orcrystallization chemical gradients can be reduced o r avoided.This principle can be adopted to more than three so lutions.Forexample fourorfive oreven more differently concentrated solutionscan be applied with varying P2024,0579 WO N April16,2025 -20 -concentrations of Zr and Ti, wherein the concentrat ion isgradually changed from Zr-rich to Ti-rich. As discu ssedabove- also a two-solution based approach can be us ed inwhich also there is a switch from Zr-rich to Ti-ric h.In the following the invention is described with re spect toexemplary embodiments and figures. The figures also compriseschematic drawings. Such schematic drawings are not true toscale and dimensions or dimension ratios may be dis torted.Accordingly, no lengths or ratios can be taken dire ctly fromthe schematic figures, except when indicated otherw ise.Figure 1 shows a schematic cross-section of a first exemplaryembodimentofa multilayerstructure.Figure 2 shows a schematic cross-section of a secon dexemplaryembodimentofa multilayerstructure.Figure 3 shows a schematic cross-section of a third exemplaryembodimentofa multilayerstructure.Figure 4 shows a schematic cross-section of a porti on of afourth exemplary embodiment of a multilayer structu re.Figure 5 shows a schematic cross-section of a porti on of afifth exemplary embodiment of a multilayer structur e.Figure 6 shows a schematic cross-section of a porti on of asixth exemplary embodiment of a multilayer structur e.Figure 7 shows a schematic cross-section of a porti on of aseventh exemplary embodiment of a multilayer struct ure. P2024,0579 WO N April16,2025 -21 -Figure 8 shows a polarization-electric field loop o f anexemplary embodiment of a PZT thin film within a mu ltilayerstructure.Figure 9 shows a relative permittivity-electric fie ld loop ofan exemplary embodiment of a PZT thin film within amultilayerstructure. Figure 10 showsa bipolardisplacementcurve ofan exemplaryembodiment of a PZT thin film within a multilayer s tructure.Figure 11 shows a unipolar displacement curve of an exemplaryembodiment of a PZT thin film within a multilayer s tructure.Figure 12 shows a photo of a first exemplary embodi ment of aMEMS mirrordevice.Figure 13 shows an optical microscope picture of th eexemplaryembodimentofa MEMS mirrordevice.Figure 14 shows an optical field-of-view measuremen t as afunction of drive frequency for the fast axis of th e MEMSmirrordevice.Figure 15 shows an optical field-of-view measuremen t as afunction of drive frequency for the slow axis of th e MEMSmirrordevice.Figure 16 shows a false color plot graph as a funct ion ofaxis drive frequency for both axes for the horizont almovementofthe mirror. P2024,0579 WO N April16,2025 -22 -Figure 17 shows a false color plot graph as a funct ion ofaxis drive frequency for both axes for the vertical movementofthe mirror. Figure 18 showsan opticalmicroscope picture ofa device with a delaminated bottom electrode.Figure 19 shows an optical microscope picture of th e deviceofFigure 18.Figure 20 shows an optical microscope image of an e xemplaryembodiment of a MEMS device according to the invent ion.Figure 21 shows a zoom-in optical microscope pictur e of theexemplary embodiment shown in Figure 20 without del amination.Figure 22 shows a scanning electron microscopy cros s-sectionimage of an exemplary embodiment of a NTC thin filmmultilayerdevice. Figure 23 showsa chartflow representation ofamanufacturing process of an exemplary embodiment of amultilayerstructure.Figure 24 shows a schematic cross-section of an eig hthexemplaryembodimentofa multilayerstructure.Figure 25 shows a schematic cross-section of a port ion of aninth exemplary embodiment of a multilayer structur e.Figure 26 shows a schematic cross-section of a port ion of atenth exemplary embodiment of a multilayer structur e. P2024,0579 WO N April16,2025 -23 -Figure 27 shows a schematic cross-section of a port ion of aneleventh exemplary embodiment of a multilayer struc ture.Figure 28 shows a schematic cross-section of a port ion of atwelfth exemplary embodiment of a multilayer struct ure.Figure 29 shows a schematic cross-section of a port ion of athirteenth exemplary embodiment of a multilayer str ucture.Figure 30 shows a schematic cross-section of a four teenthexemplaryembodimentofa multilayerstructure.Figure 31 shows a scanning transmission electron mi croscopeimage of a PZT thin film of an exemplary embodiment of amultilayerstructure.In Figure 1 a first exemplary embodiment of a multi layerstructure 1 is shown in schematic cross-section. In thisexemplary embodiment an adhesion layer 3 is positio ned on asilicon-wafer-based substrate 2. The adhesion layer 3comprisesa transition metalora transition metal oxide.Atransition metal can be any transition metal from t he fourth,fifth or sixth period of the periodic table. An ele ctrodelayer4 ispositioned on top ofthe adhesion layer 3.Theelectrode 4 can comprise or consist of a noble meta l or aconducting oxide. In this stack, the electrode laye r 4 can beaddressed asa bottom electrode.An electroceramic layer5 ispositioned above the bottom electrode 4. The electr oceramiclayer 5 can be a dielectric, a pyroelectric, a ferr oelectric,piezoelectric layer, or a layer containing a thermi storceramic. A top electrode 6 is arranged on top of th eelectroceramiclayer5.The top electrode 6 can be anyconducting electrode. For example, the top electrod e 6 can be P2024,0579 WO N April16,2025 -24 -a noble metal electrode or a conducting oxide elect rode. Itcan be of the same or a different material to the b ottomelectrode 4. The materialsdescribed forthese differentlayers can bethose named in the introduction. A particularly pre ferredexample for the substrate 2 is an SOI wafer (silico n-on-insulator wafer). As an adhesion layer 3 a tantalum -containing adhesion layer is particularly preferred . It cancomprise metallic tantalum and / or comprise tantalum oxide. Ontop of this it is preferred that a platinum electro de 4 isarranged. The electroceramic layer 5 can preferably comprisea PZT materialora thermistormaterialsuch asan NTCmaterial. A chromium / gold electrode is preferred as topelectrode 6.The SOI wafer substrate can have the following inte rnallayering structure from bottom to top: On a silicon oxidelayer of 1.5 µm thickness a silicon handle layer of 450 µm ispositioned. A silicon oxide buried oxide layer of 1 µmthickness is arranged above the silicon handle laye r. On topof the buried oxide layer, a silicon device layer o f 150 µmthickness is arranged. On top of the silicon device layer, asilicon oxide layerof1 µm isarranged.According to a preferred embodiment with the SOI la yer, theadhesion layer of tantalum has a thickness of 20 nm . Thebottom electrode 4 of platinum can have a thickness of 200nm. The PZT electroceramic layer 5 can have a thick ness of1.7 µm. The top electrode can be formed from a chro me andgold electrode. These may be realized as subsequent layers. Achrome layer in this can be 20 nm and can be arrang ed between P2024,0579 WO N April16,2025 -25 -the PZT layer and the gold layer. The gold layer ca n have athicknessof200 nm.Not depicted explicitly but in many cases preferred , a seedlayercan be positioned between the electroceramic layerandthe electrode. The seed layer can additionally faci litatecrystalline and / or oriented growth of the electroce ramiclayer. The presentsetup hasthe advantage offorming anelectroceramic film 5 such as said PZT electroceram ic film orsaid NTC electroceramicfilm with a high degree oforientation and good adhesion towards the substrate . Further,the multilayer structure can be prepared without ha ving topolish the substrate 2 or otherwise control the sur faceroughness. As shown below, outstanding performances can beachieved forsuch multilayerstructures.Figure 2 shows a schematic cross-section of a secon dexemplary embodiment of a multilayer structure 1. T hemultilayerstructure 1 ofFigure 2 isidenticalto themultilayer structure of Figure 1 in the upper porti on, i.e.in the layers with the reference numbers 2, 3, 4, 5 and 6which are identical to those described for the firs texemplary embodiment. However, also on the other ma in surfaceof the substrate 2, a second adhesion layer 3', a s econdelectrode 4',a second electroceramiclayer5'and a secondtop electrode 6' are arranged. The materials of the se layerscan correspond to those of the first adhesion layer 3, thefirstbottom electrode 4,the firstelectroceramic 5 and thefirst top electrode 6. Accordingly, this results in a mainlysymmetrical layer arrangement with respect to the l ayers withreference numbers2 to 6. P2024,0579 WO N April16,2025 -26 -In Figure 3 a schematic cross-section of a third ex emplaryembodiment of a multilayer structure 1 is shown. Th is thirdembodiment of a multilayer structure 1 is a modific ation ofthe first exemplary embodiment shown in Figure 1. H ere on thesubstrate 2 the first adhesion layer 3, the first b ottomelectrode 4, the first electroceramic layer 5 and t he firsttop electrode 6 are arranged. A second electroceram ic layer5'' is arranged above the first top electrode 6. Th e secondtop electrode 6''isarranged on top ofthe secondelectroceramic layer 5''. For this setup, the first topelectrode 6 acts as a bottom electrode for the seco ndelectroceramic layer 5''. The materials of the seco ndelectroceramic layer 5'' can be selected from the s amematerials from which the material of the first elec troceramiclayer 5 is selected. Also, the materials of the sec ond topelectrode 6'' can be selected from the same materia ls fromwhich the material of the first electrode 6 is sele cted.In a similarmannerasshown in Figure 3,multiple furtherelectroceramic layers and top electrodes can be sta ckedalternatingly. It is preferred that such a stack isterminated bya top electrode.The third exemplary embodiment can of course be com bined withthe second exemplary embodiment, i.e. the two-sidedarrangement used as shown in Figure 2. This may res ult in asymmetrical stacking with both sides having the sam e numberof stacks. It can also result in a stacking in whic h bothsides have a different number of electroceramic lay ers andtop electrodes. P2024,0579 WO N April16,2025 -27 -Figure 4 shows a schematic cross-section of a porti on of afourth exemplary embodiment of a multilayer structu re 1.Figure 4 can represent an arrangement of an adhesio n layer 3on a substrate 2 in the first, second or third exem plaryembodiment of a multilayer structure as depicted in Figures1, 2 or 3 respectively. In this fourth exemplary em bodiment,the adhesion layerisarranged on the substrate 2. The adhesion layer3 comprisesorconsistsofone type ofmaterial and has no internal material layer boundar ies. Inthe present case the adhesion layer consists only o f atransition metaloran alloyoftransition metals.Figure 5 shows a schematic cross-section of a porti on of afifth exemplary embodiment of a multilayer structur e 1.Figure 5 can represent an arrangement of an adhesio n layer 3on a substrate 2 in the first, second and third exe mplaryembodiments of a multilayer structure 1 as depicted inFigures1,2 or3,respectively.In thiscase,the adhesionlayer 3 comprises a first adhesion sublayer 3a whic hcomprises or consists of a transition metal or an a lloy oftransition metals. On top of this, a second adhesio n sublayer3b that comprises or consists of a transition metal oxide isarranged. This means that the transition metal oxid e layercan also be a mixed oxide comprising a transition m etaloxide. The transition metal of the transition metal oxide maybe the same or may be different from the transition metal ofthe firstadhesion sublayer3a.Figure 6 shows, in principle, a similar setup as th at ofFigure 5 as a sixth exemplary embodiment of a multi layerstructure 1, with a reverse stacking of the first a dhesionsublayer 3a and the second adhesion sublayer 3b. He re for thesixth exemplary embodiment the second adhesion subl ayer 3b P2024,0579 WO N April16,2025 -28 -comprising or consisting of a transition metal oxid e isarranged directly on the substrate 2. The first adh esionsublayer 3a comprising or consisting of the transit ion metalis arranged on top of it. Also the stacking in this exemplaryembodiment of Figure 6 can represent an arrangement of anadhesion layer 3 on a substrate 2 in the first, sec ond orthird exemplary embodiment of a multilayer structur e 1 asdepicted in Figures1,2 or3 respectively.Figure 7 shows a schematic cross-section of a porti on of aseventh exemplary embodiment of a multilayer struct ure 1,which is a modification of the stacking as shown in Figure 5,i.e. of the fifth exemplary embodiment. On top of t he firstadhesion sublayer3a,the second adhesion sublayer 3b ispositioned in the same manner as in Figure 5. On th e secondadhesion sublayer 3b, a third adhesion sublayer 3a' isarranged that comprises or consists of a transition metal.The transition metal in the first and the third adh esionsublayer 3a and 3a' can be identical and may also b edifferent. Otherwise, the above-described propertie s mayapply.Not depicted, but also possible is a reverse arrang ement ofthe adhesion sublayers For example, a transition me talcontaining adhesion sublayer can be sandwiched by t wotransition metal oxide containing adhesion sublayer s.Forthe adhesion layersdepicted in Figures4 to 7 theinventors have found out that by using a transition metal,adhesion can be improved between a silicon-wafer-ba sedsubstrate and more generally between a semiconducto rsubstrate or an insulator substrate and an electrod e such asa platinum or other noble metal electrode. Furtherm ore, the P2024,0579 WO N April16,2025 -29 -inventors found that the transition metal can at le astpartially prevent migration of elements or substanc es betweenthe layers. In particular if an oxide layer is pres ent, thediffusion or migration of ions seems to be even bet tersuppressed.In the context of the previous exemplary embodiment s, theinventors developed some further exemplary embodime nts whichrelate to properties of the previous exemplary embo diments orwhich are more generalized versions of these exempl aryembodiments.In Figure 24, an eighth exemplary embodiment of a m ultilayerstructure is shown. Principally, it has the same la yerstacking as the first exemplary embodiment of a mul tilayerstructure which is depicted in Figure 1. However, i nstead ofthe electroceramic layer 5 being directly positione d on theelectrode 4, a support layer SL is arranged between theelectrode 4 and the electroceramiclayer5.In the presentcase, the support layer SL is a lanthanum nickel ox idesupport layer (LNO; LaNiO 3) that acts as a conducting layerand also hasa seed-layer-functionalitythathelps tofacilitate crystal growth and oriented crystal grow th.Alternatively, the support layer SL can also be lea d titanate(PbTiO 3), lead oxide (PbO) or titanium oxide (TiO 2).Despite the impression given by the figure, the sup port layerSL is preferably considerably thinner than the elec troceramiclayer.In in the present exemplary embodiment, also the ad hesionlayer 3 is modified in comparison to the adhesion l ayerdescribed forthe firstexemplaryembodimentshown in Figure P2024,0579 WO N April16,2025 -30 - 1.Instead ofa single layer,the adhesion layer3 comprisesmore than one adhesion sublayer. The adhesion layer 3comprisesthe adhesion sublayer3a and in addition further adhesion sublayerswhich are indicated to countup to nlayers, with n representing an arbitrary counting v ariable.The layers are numbered 3a to 3n. Each of the adhes ionsublayersiseithera metalliclayercomprising or consistingof a transition metal or an oxidic layer comprising orconsisting of a transition metal oxide. Each of the adhesionsublayers in Figure 24 is either structurally or ch emicallydifferent to at least a neighbouring sublayer. This may meanforan arbitrarysublayer3i(one ofthe sublayers in 3a to 3n)a neighbouring sublayer3i+1 ischemicallyor structurallydifferent.Forexample,the arbitrary sublayer 3icould be metallicand the neighbouring sublayer 3i+1 isalso metallic, but both comprise a different transi tionmetal. Also, in another example, the arbitrary subl ayer 3icould comprise transition metal oxide and the neigh bouringsublayer 3i+1 comprises a different transition meta l oxide.Also, in another example, the arbitrary sublayer 3i couldcomprise transition metal oxide and the neighbourin g sublayer3i+1 ismetallic,and eithercomprisesthe same or adifferent transition metal than the transition meta l of theoxide of the arbitrary sublayer 3i. Of course the s amerelation could also be present the other way round. Ofcourse, independent from the relation of the sublay ers 3i and3i+1, the same relations may apply for the neighbou ringsublayers3iand 3i-1.A specific example that may be represented by the e ighthexemplary embodiment of Figure 24 but with only one sublayerhas a silicon oxide terminated silicon substrate 2. Anadhesion layer 3 comprising or consisting of metall ic Ta is P2024,0579 WO N April16,2025 -31 -arranged on the titanium oxide (first adhesion subl ayer). Theelectrode 4 is made of Pt. On the electrode 4 a lan thanumnickel oxide supporting layer SL is arranged. Above anelectroceramiclayer5 comprising orconsisting of PZT isarranged. In particular for this arrangement a high filmqualitywasfound.Further examples of adhesion which would fall under thegeneral description of the adhesion layer 3 describ ed forFigure 24 are given in the following.Furthermore, it is noted that the sublayer arrangem ent ofFigure 24 and also of the other adhesion layers cou ld beapplied to any of the other examples and is not lim ited to anexample having a supportlayerSL.In Figure 25 a schematic cross-section of a portion of aninth exemplary embodiment of a multilayer structur e 1 isshown. In its general setup this exemplary embodime nt issimilar to the exemplary embodiments shown for Figu re 5 andFigure 6, i.e. it has an adhesion layer that compri ses afirst sublayer and a second sublayer. The first sub layer 3acomprises a first transition metal and is metallic. Thesecond adhesion sublayer3b in thiscase comprises a secondtransition metal and is also metallic, but the seco ndtransition metal is different from the first transi tionmetal.Forexample,the firsttransition metalmay betantalum and the second transition metal may be tit anium.Alternatively, the first adhesion sublayer may be c hromiumand the second adhesion sublayer3b maybe nickel. In asimilar manner also a third adhesion sublayer might berealized (not depicted) that is metallic having a t hird P2024,0579 WO N April16,2025 -32 -transition metal, different to the second transitio n metal.For example, the third transition metal could be si lver.A similarsetup (notshown)mayalso be formed for adhesion sublayersthatallcomprise an oxide.Forexample, a firstadhesion sublayer may comprise a first transition m etaloxide, while a second transition metal sublayer com prises asecond transition metal oxide. The first transition metaloxide could be, for example, titanium oxide and the secondtransition metal oxide could be tantalum oxide. Sim ilarly,also a third adhesion sublayer (not depicted) compr ising athird transition metal oxide top. The third transit ion metaloxide is different than the second transition metal oxide.Forexample,itmaybe aluminium oxide.Figure 26 shows a schematic cross-section of a port ion of atenth exemplary embodiment of a multilayer structur e 1. Thistenth exemplary embodiment is structurally based on the fifthexemplary embodiment. However, instead of the first adhesionsublayer 3a, a first adhesion sublayer 3a1 and a se condadhesion sublayer3a2 are realized.Both the first adhesionsublayer 3a1 and the second adhesion sublayer 3a2 a remetallic. The transition metal comprised in the fir stadhesion sublayer 3a1 is different to the transitio n metalcomprised in the second adhesion sublayer 3a2. In a similarmanner,instead ofthe second adhesion sublayer3b shown inthe exemplary embodiment of Figure 5, a third adhes ionsublayer 3b1 and a fourth adhesion sublayer 3b2 are realized.The third adhesion sublayer 3b1 comprises a first t ransitionmetal oxide. The transition metal of the first tran sitionmetaloxide ofthe third adhesion sublayer3b1 can be thesame or different to the transition metal that is c omprisedin the first adhesion sublayer 3a1 or the second ad hesion P2024,0579 WO N April16,2025 -33 -sublayer 3a2. Also, the fourth adhesion sublayer 3b 2comprises a transition metal oxide (second transiti on metaloxide). The transition metal of the second transiti on metaloxide is different to the transition metal of the f irsttransition metal oxide. Otherwise, there is no limi tation tothe transition metalofthe transition metaloxide ofthefourth adhesion sublayer 3b2. It can be the same or differentto any of the transition metal of the first and the secondadhesion sublayers3a1 and 3a2.Figure 27 shows a schematic cross-section of a port ion of aneleventh exemplary embodiment of multilayer structu re 1. Thiseleventh exemplaryembodimentisa modification of the sixthexemplary embodiment in the same manner as the tent hexemplary embodiment is a modification of the fifth exemplaryembodiment. The stacking order shown for the eleven thexemplary embodiment is different to the stacking o rder shownin the tenth exemplary embodiment. However, otherwi se theexplanations regarding the individual adhesion subl ayersexplained for the tenth exemplary embodiment apply.Figure 28 shows a schematic cross-section of a port ion of atwelfth exemplary embodiment of a multilayer struct ure 1. Thetwelfth exemplary embodiment is a modification of t hestacking shown for the eleventh exemplary embodimen t shown inin Figure 27. This means that regarding the third a dhesionsublayer 3b1, the fourth adhesion sublayer 3b2, the firstadhesion sublayer 3a1 and the second adhesion subla yer 3a2,the features explained for the eleventh exemplary e mbodimentdepicted in Figure 27 apply. In addition, a fifth a dhesionsublayer3c1 and a sixth adhesion sublayer3c2 are arrangedabove the second adhesion sublayer 3a2. The fifth a dhesionsublayer 3c1 comprises a transition metal oxide. Si milarly, P2024,0579 WO N April16,2025 -34 -the sixth adhesion sublayer 3c2 also comprises a tr ansitionmetal oxide which, however, has a different transit ion metalthan the transition metal of the fifth adhesion sub layer 3c1.Otherwise, there is no limitation regarding the tra nsitionmetalofthe fifth and sixth adhesion sublayer3c1 and 3c2.For example, the transition metal oxide of the fift h adhesionsublayer 3c1 may be the same as either of the third or thefourth adhesion sublayer 3b1 and 3b2. The same hold s true forthe sixth adhesion sublayer3c2.Figure 29 shows a more generalized exemplary embodi ment basedon the fifth exemplary embodiment. It shows that th ere may beseveral adhesion metal sublayers 3a1, which are all metallicand each ofwhich hasa differenttransition metal oxide tothe neighbouring metallic adhesion sublayers. The p rinciplesexplained for the eighth exemplary embodiment shown in Figure24 applyhere.Transition metal oxide-based sublayers 3b1 to 3bm a rearranged above the metallic adhesion sublayers. The ir numbermay be the same or may be different than the number ofmetallic adhesion sublayers. For each of the transi tion metaloxide-based adhesion sublayers in principle the sam e appliesas was discussed for the metallic adhesion sublayer s, i.e.the transition metal in each of them is different t o theneighbouring oxidic sublayers. The last metallic ad hesionsublayer 3an and the first transition metal oxide-b asedadhesion sublayer3b1,which neighboureach other, maysharethe same transition metal oxide, but this is not re quired.The principles explained for the eighth exemplary e mbodimentshown in Figure 24 applyhere. P2024,0579 WO N April16,2025 -35 -In Figure 30 a fourteenth exemplary embodiment of amultilayer structure is shown in schematic cross se ction. Itis based on the first exemplary embodiment shown in Figure 1.However, instead of one mainly uniform electrocerma ic layer5, here the electrocermic layer 5 has a first elect rocermaicsublayer 5a and a second electrocermaic sublayer 5b . Thefirstelectrocermaicsublayer5a and the second electrocermaicsublayer5b are based on the sameelectrocermic material, as for example PZT. However , thecomposition ofthe two sublayersisdifferent.For example,components such as dopants or main ions such as La, Pb, Zr orTi may have different concentrations in both sublay ers.In Figures 8 to 11, results of electrical and piezo electriccharacterization measurements are depicted. The mea surementswere performed on a multilayer structure as depicte d inFigure 1,which wasformed on a SOIwaferwith the above-described properties with the piezoelectric layer h aving athicknessof1.7 µm.The thicknessesofthe layers were asdescribed above. As a top electrode a 25 nm chromiu m layerand a 200 nm gold layer were sputtered above the PZ Telectroceramic layer. From this cantilever-shaped d eviceswith a large area top electrode of 19.45 mm 2 were diced andused for the characterization. All of the measureme nts weretaken on the same sample.Figure 8 shows a graph of polarization versus elect ric fieldrecorded at 10 Hz. The curve represented by a dashe d line,which is the one having a larger extent in the y-di rectionand which has an associated left-pointing arrow, isassociated with the left y-axis indicated as "polar ization".The curve represented by the continuously drawn lin e whichalso has a smaller extent in the y-direction is ass ociated P2024,0579 WO N April16,2025 -36 -with the current density measured, as is also indic ated bythe associated arrow pointing right. The polarizati onelectric field loop clearly indicates ferroelectric switchingwith a remanent polarization P r of around 20 µC cm -2 and acoercive field E c of around 30 kV cm -1.Figure 9 shows the relative permittivity and the lo ss tangentversus the DC bias electric field, measured at a sm all signalfrequency of 225 Hz and a small signal amplitude of5 kV cm -1. The graph represented by the dashed line and thedashed circular data points shown further up in the figure isthe relative permittivity measurement associated wi th theleft y-axis as indicated by the arrow pointing left . Thecurve, which is lower in the figure and which is dr awn as acontinuous line and represented by the continuous c irculardata points, is associated with the loss tangent of the righty-axis, as also indicated by the small red arrow po intingright. The measurements clearly show that at zero D C biasfield the relative permittivity is about 1700 while the lossremainsbelow 10%.The high qualityofthe film is also shown in thatno leakage athigh DC fieldswasobserved.Figure 10 shows a bipolar displacement curve record ed at 10Hz. The bipolar displacement curve is symmetrical a ndexhibits the typical butterfly shape of high-qualit y PZTfilms.Figure 11 shows an unipolar displacement curve. Fro m thiscurve, the values summarized in Table 1 were conclu ded.Table 1: -e 31,f + -e 31,f - Average ofΔe31,f |e31,f | P2024,0579 WO N April16,2025 -37 - Sample of22.43 C m −2 17.60 C m −2 20.02 C m −2 4.84 C m −2Figure 11As can be seen in Table 1, the effective transverse piezo-electric coefficient │e31,f │ was evaluated to be 20 C m -2. Forthis measurement no hot poling of this thin film un der DCelectric field was applied. Within the invention, i t would bepossible to additionally apply hot poling to even f urtherimprove the piezoelectric thin film. Also doping ma y furtherimprove the piezoelectricthin film further. In Figures12 and 13,an exemplaryembodimentofa high-frequency 2D bi-resonant MEMS micromirror 10 is dep icted.Figure 12 showsa photograph ofthe device.Figure 13 showsamicroscope image of the micromirror. The micromirro r 10 has amirror platelet or mirror surface 13 with a diamete r of 1.5mm. The mirror can be tilted or brought into vibrat ion alongthe so-called fast axis 12 and the slow axis 11. Un deroperation, the actuator ring 14 is put under voltag e.The actuator ring 14 comprises a multilayer structu reaccording to the invention. Its construction is mai nlyidentical to the stacking shown in Figure 1. In par ticular,on a SOI substrate with the properties as described forFigure 1, a tantalum layer of 20 nm thickness as an adhesionlayerisdeposited.The bottom electrode isformed from a 200 nm platinum electrode.The electroceramiclayeris a 1700 nmthick PZT layer which, for example, can be formed a ccordingto the process described below. The top electrode i s formedfrom a 20 nm thick chromium layer and a 200 nm thic k goldlayer. P2024,0579 WO N April16,2025 -38 -In Figures 14 to 17, optical field-of-view (FoV) me asurementsare shown. Figure 14 shows optical field of view me asurementsfor the drive frequency of the fast axis at differe ntvoltages. The data points are always shown together with afit curve. In a similar manner, the optical field o f viewmeasurement for the slow axis at different voltages is shownin Figure 15. These graphs in Figure 14 and 15 repr esent 1Doperationsatdifferentactuation voltages. Ascan be seen,the achieved maximum opticalfield ofviewvalues prove the stability and adhesion strength ac hievedusing an adhesion layer. The adhesion is so good th at thelimiting factor achievable for maximum optical fiel d of viewis not the layer stack, but the mechanical strength of theunderlying silicon-based substrate. In addition, th emeasurements of Figures 14 and 15 reveal that the l ayer stackgenerates even enough force and energy to actuate a highfrequency mechanical mode close to 40 kHz without c racking.Figures 16 and 17 show false color plot images, rep resentinga 2D measurement in which both sets of torsion bars areactuated simultaneously. Figures 16 and 17 show opt ical fieldof view measurements as a function of both axes dri vefrequenciesforthe horizontal(Figure 16)and the vertical(Figure 17) optical field of view of the implemente d MEMSmirror device in the case of this 2D operation. The se resultsconfirm that the layer stack is even able to actuat e bothaxes of the mirror with a relatively high optical f ield ofview of31°×42°simultaneouslywithoutanydamage.Accordingly, the depictions of Figures 16 and 17 pr ove a highquality of the multilayer structure according to th einvention. P2024,0579 WO N April16,2025 -39 -In Figures 18 and 19 a case is shown in which, unde r similarstress as concluded from Figures 14 to 17, a microm irrorshows failure and in particular delamination. Figur e 18 showsan opticalmicroscopicpicture in which the bottom electrodewas damaged under fabrication during the wire-bondi ngprocess. In Figure 19 delamination between the SiO 2 andadhesion layer can be seen. These effects are often observedin cases in which titanium oxide is used as an adhe sionlayer.In particular,ashasbeen described above, tantalum showsfarsuperioradhesion.The observation that tantalum shows far better adhe sion thantitanium oxide can also be seen in Figures 20 and 2 1. Figure20 showsan opticalmicroscope picture ofa device wheretantalum was used as a material for the adhesion la yer. Thewire-bonding here is easily performed without damag ing thebottom electrode stack. Even over large areas, ther e are nosigns of delamination at any interface, as can be s een inFigure 21.In Figure 22, a cross-sectional scanning electron m icroscopyimage of a multilayer structure including an NTC la yer isshown. Here as a silicon substrate, a silicon wafer having asilicon oxide layer of 1 µm thickness on a first si defollowed by a silicon layer of 675 µm and with a se condsilicon oxide layerof1 µm thicknesswasused.As can beseen in the cross-section image, only the upper por tion ofthe substrate can be seen, which is the silicon lay er 2a andthe upper silicon oxide 2b. On top of the silicon o xide layer2b, a 20 nm thick adhesion layer 3 is deposited. It s positionis roughly indicated by the brighter line in the pi cture.Above, a platinum electrode 4 of 200 nm is arranged . Abovethe platinum electrode 4 an electroceramiclayer5 is P2024,0579 WO N April16,2025 -40 -arranged. The electroceramic layer 5 consists of an NTC filmof Mn-Co-Ni oxide. The NTC layer had a thickness of 125 nm.The arrangement was prepared such that first the si liconwafer was treated under UV light and ozone for 10 m inutes.Subsequently, the tantalum and the platinum were su ccessivelydeposited on the silicon wafer using room temperatu re DCmagnetron sputtering at 200 W. Subsequently, the NT C layerwas formed. Therefore, first an NTC precursor solut ion wasprepared. This solution was filtered before deposit ion. TheNTC precursor solution was dispensed on the substra te andspin coated.A firstsublayerofthe NTC precursor solutionwas deposited on the accordingly prepared bare subs trate andsubsequentlydried and pyrolyzed on a hotplate at 350-450°C. To achieve the desired thickness, coating, dryi ng andpyrolysiswere repeated five times.Afterthatthe amorphousfilm was crystalized in an RTA furnace at 650-770 ° C.As can be seen in Figure 22, the NTC film was crack -free anddefect-free. Furthermore, the scanning electron mic roscopyimage confirmed a dense NTC thin film and no sign o fdelamination ofthe NTC film orbottom electrode.Figure 31 shows a scanning transmission electron mi croscopy(STEM) image of a PZT thin film deposited above a s ilicon-wafer-based-substrate 2. Of the silicon-wafer-based only theterminating silicon oxide layer can be seen. As can be seenin the picture, the electroceramic film 5 consistin g of PZTisarranged above the platinum bottom electrode 4. In thiscross-sectional image, crystalline columns 7 (as in dicated inthe Figure) can be identified which extend across t he entirethickness of the electroceramic film 5. This very g oodcolumnar grain growth is preferred as it leads to h igh P2024,0579 WO N April16,2025 -41 - electromechanicalresponse.The STEM confirmed the absence ofsecondary phases, such as pyrochlore, which is know n todecrease the performance of the electroceramic elem entsignificantly.The adhesion layer3,which in this case isaTa-layer that is arranged between substrate 2 and e lectrode 4is so thin that it is hardly visible at the interfa ce betweensubstrate 2 and electrode 4. Despite its small thic kness atleast part of the high-quality columnar growth of t heelectroceramic film 5 is attributed to the presence of anadhesion layer.Figure 23 shows a flowchart of a process of forming a PZTthin film on a SOI substrate. The accordingly prepa red filmcan be,forexample,the one asdepicted in Figure 1 ortheone as used in the micromirror shown in Figure 12 a nd Figure13.As a substrate, a SOI wafer was used which has, fro m bottomto top, a silicon oxide layer of around 1.5 µm thic kness, asilicon handle layer of 450 µm thickness, a silicon oxideburied oxide layer of 1 µm thickness, a silicon dev ice layerof 150 µm thickness and a silicon oxide top layer o f 1 µmthickness. This upper silicon oxide layer was first treatedin a UV ozone cleaner for 10 minutes. After this cl eaning, anadhesion layer of tantalum with a thickness of 20 n m wasdeposited via room temperature DC magnetron sputter ing at 500W. On top ofsaid tantalum layer,a platinum layerof 200 nm isdeposited, again with room temperature DC magnetronsputtering at 500 W. The sputtering was carried out in anargon working gasatmosphere with n argon pressure ofbetween1×10-3 mbar and 8×10 -2 mbar. The distance between target and P2024,0579 WO N April16,2025 -42 - substrate was12 to 18 cm.Thusa stackcomprising thesilicon wafer with the tantalum layer and the plati num layerisformed.After that a lead titanate seed layer (PbTiO 3) is depositedon the platinum electrode. For this, first a seed l ayersolution comprising PbTiO 3 was formed. The solution had aconcentration of 0.0625 mol / l of PbTiO 3 and a 10% molarexcess of lead in order to compensate for evaporati on duringcrystallization. Before a deposition, the seed laye r wasfiltered through a 0.2 µm PTFE syringe filter. Subs equently,the seed layer solution was dispensed on the bare p latinumsurface and spin-coated at a rotation speed of 2000 rotationsper minute for 30 seconds. The thus deposited amorp hous seedlayer was dried and pyrolyzed at a temperature of 1 50 °C on ahotplate and subsequently crystallized in a rapid t hermalannealing furnace at 520 °C. Thereby a seed layer o fapproximately 10 nm was formed. Thus, a stacking of a SOIsubstrate,an adhesive layeroftantalum,platinum electrode layerand a seed layerisformed.Subsequently, the PZT electroceramic film is formed bydepositing several partial layers of which each com prisethree sublayers.First a zirconium-enriched sublayer is formed. Ther efore, afirst zirconium-enriched first precursor solution i s preparedby dissolving lead(II) acetate in a solution of zir conium(IV)propoxide and titanium(IV) isopropoxide in acetic a cid and 2-methoxyethanol. Upon dissolution of the lead precur sor at60 °C the resulting solution was refluxed for 2 hou rs in anitrogen atmosphere. After distillation of the by-p roducts,the mixture wasdiluted to achieve a concentration of0.5 P2024,0579 WO N April16,2025 -43 -mol / l. The composition of the first prepared soluti oncorresponds to the composition of Pb(Zr 0.63 Ti 0.37 )O3 for thesublayer to be formed. The solution is prepared suc h that italso has 15% molar excess of lead. Before depositio n, thezirconium-enriched first precursor solution was fil teredthrough an 0.2 µm PTFE syringe filter. Subsequently , thezirconium-enriched first precursor solution was dis pensed onthe seed layer and spin-coated at a rotation of 200 0rotations per minute for 30 seconds. The thus depos itedzirconium-enriched sublayer was dried and pyrolyzed attemperaturesof150 °C and 350 °C,respectively. Subsequently,to form a medium concentrated second sublayer,first a medium concentrated second precursor soluti on isprepared by dissolving lead(II) acetate in a soluti on ofzirconium(IV) propoxide and titanium(IV) isopropoxi de inaceticacid and 2-methoxyethanol.Upon dissolution ofthe lead precursorat60 °C the resulting solution was refluxedfor 2 hours in a nitrogen atmosphere. After distill ation ofthe byproducts,the mixture wasdiluted to achieve a concentration of0.5 mol / l.The composition ofthe asprepared solution corresponds to the composition ofPb(Zr 0.53 Ti 0.47 )O3 for the sublayer to be formed. The solutionisprepared such thatitalso has15% molarexcess oflead.Before deposition, the medium concentrated second p recursorsolution was filtered through an 0.2 µm PTFE syring e filter.Subsequently, the medium concentrated second precur sorsolution was dispensed on the dried and pyrolyzed z irconium-enriched sublayer and spin-coated at a rotation spe ed of 2000rotations per minute for 30 seconds. The thus depos itedmedium concentrated second sublayer was dried and p yrolyzedat temperatures of 150 °C and 350 °C, respectively. P2024,0579 WO N April16,2025 -44 -Subsequently, to form a titanium-enriched third sub layer,firsta titanium-enriched third precursorsolution isprepared by dissolving lead(II) acetate in a soluti on ofzirconium(IV) propoxide and titanium(IV) isopropoxi de inaceticacid and 2-methoxyethanol.Upon dissolution ofthe lead precursorat60 °C the resulting solution was refluxedfor 2 hours in a nitrogen atmosphere. After distill ation ofthe byproducts,the mixture wasdiluted to achieve a concentration of0.5 mol / l.The composition ofthe asprepared solution corresponds to the composition ofPb(Zr 0.43 Ti 0.57 )O3 for the sublayer to be formed. The solutionisprepared such thatitalso has15% molarexcess oflead.Before deposition, the titanium-enriched third prec ursorsolution was filtered through an 0.2 µm PTFE syring e filter.Subsequently, the titanium-enriched third precursor solutionwas dispensed on the dried and pyrolyzed was dispen sed on thedried and pyrolyzed medium-concentrated second subl ayer andspin-coated at a rotation speed of 2000 rotations p er minutefor 30 seconds. The thus deposited titanium-enriche d thirdsublayer was dried and pyrolyzed at temperatures of 150 °Cand 350 °C, respectively.The partial layer that is formed from the three sub layers sofarisamorphous.Ithasa thicknessofbetween 50 to 200 nm.After forming of this amorphous partial layer it is subjectedto a crystallization step in a rapid thermal anneal ingfurnace at650°CIn order to form a PZT electroceramic layer of a th ickness ofbetween 1.7 to 2.5 µm, the above-described formatio n ofpartial layers was repeated 24 times. In the presen t example,a thickness of 1.7 corresponds to 24 partial layers , P2024,0579 WO N April16,2025 -45 -respectively. Thus, stacking of an SOI substrate, a tantalumadhesion layer,a platinum electrode layer,a seed layeranda PZT electroceramic functional layer can be formed . Finally,butnotdepicted,in Figure 23 a top electrode can bedeposited for example by DC magnetron sputtering. T he topelectrode may comprise, for example, gold or platin um and / orhave a chromium partiallayerin the presentcase.The above process can be adapted for other material s or otherthicknessesoflayers.

[0002] P2024,0579 WO N April16,2025 -46 - Reference sign list 1 multilayerstructure 2 substrate 3 adhesion layer 3a firstadhesion sublayer 3b second adhesion sublayer 3a’third adhesion sublayer 3a1 fistadhesion sublayer 3a2 second adhesion sublayer 3b1 third adhesion sublayer 3b2 fourth adhesion sublayer 3c1 fifth adhesion sublayer 3c2 sixth adhesion sublayer 3’second adhesion layer 4 electrode 4’second bottom electrode 5 electroceramicfilm 5’,5’’second electroceramiclayer 6 top electrode 6’,6’’second top electrode 7 column 10 micro mirror 11 slow axis 12 fastaxis 13 mirrorsurface 14 actuatorring

Claims

P2024,0579 WO N April16,2025 -47 - Claims 1.A multilayerstructure comprising a semiconductororinsulatorsubstrate,an electrode containing a noble metal or a conducti ve oxidearranged above the semiconductor or insulator subst rate, andan electroceramic layer arranged above or on the el ectrode,wherein an adhesion layercomprising a transition metalor transitionmetal oxide is arranged between and in direct conta ct with amain surface ofthe substrate and the electrode.

2. The multilayer structure according to claim 1, w herein thesubstrate is a silicon-wafer-based substrate, a sap phirebased substrate ora glasssubstrate.

3. The multilayer structure according to claim 1 or 2,wherein the substrate has on its main surface a sur faceroughnessRa of10 nm to 2 µm,preferably20 nm to 1 µm.

4. The multilayer structure according to any of cla ims 1 to3, wherein the adhesion layer comprises a first adh esionsublayer comprising a transition metal and a second adhesionsublayercomprising a transition metaloxide.

5. The multilayer structure according to any of the precedingclaims, wherein the adhesion layer comprises n adhe sionsublayers each comprising a transition metal in met allic formora transition metaloxide with n ≥ 2,wherein an individualadhesion sublayer is chemically or structurally dif ferentfrom a directlyneighboring adhesion sublayer.P2024,0579 WO N April16,2025 -48 -6. The multilayer structure according to claim 5, w herein theone of the adhesion sublayers and is directly neigh boringadhesion sublayerare chemicallydifferentin thatboth are metallic and comprise a different transiti on metal,orboth comprise differing transition metal oxides, orone is metallic and one has a transition metal oxid e.

7. The multilayer structure according to any of cla ims 1 to6, wherein the transition metal is selected from Ti , Ta or Woralloysofthese.

8. The multilayer structure according to any of cla ims 1 to7,wherein the adhesion layerhasa thicknessof1 nm to 100 nm,such aspreferably10 to 50 nm.

9. The multilayer structure according to any of cla ims 1 to8, wherein the electrode comprises or consists of P t or Ir.

10. The multilayer structure according to any of cl aims 1 to9, wherein the electrode comprises or consist of an iridiumoxide, a rhodium oxide, a rhenium oxide, a rutheniu m oxide ora strontium ruthenium oxide.

11. The multilayer structure according to any of cl aims 1 to8, wherein the electroceramic layer comprises or co nsists ofa dielectric, piezoelectric, pyroelectric, ferroele ctricceramicmaterialora thermistorceramicmaterial.

12. The multilayer structure according to any of cl aims 1 to9, wherein a second electrode is arranged on a seco nd mainsurface of said substrate, wherein a second adhesio n layer isarranged between said second main surface and the s econdP2024,0579 WO N April16,2025 -49 -electrode, and wherein a second electroceramic laye r ispositioned above oron the second electrode.

13. The multilayer structure according to any of cl aims 1 to12,wherein a furtherelectrode isarranged on the adhesionlayer and a further electroceramic layer is arrange d on orabove the furtherelectrode.

14. The multilayer structure according to any of th epreceding claims, wherein the electrocermic layer c omprises afirstand a second electrocermicsublayer.

15. The multilayer structure according to according to any ofthe preceding claims, wherein a supporting layer is arrangedbetween the electrode and the electroceramic layer.

16. The multilayer structure according to claim 15, thesupporting layerhaving an electricallyconducting propertyand / or facilitates crystal growth of the electrocer amic layerand / or facilitates uniform crystal orientation of t heelectroceramiclayer. 17.The multilayerstructure according to claim 15 or16, wherein the supportlayercomprisesorconsistsof leadtitanate, lanthanum nickel oxide, lead oxide, or ti taniumoxide.

18. Micro-mirror comprising the multilayer structur eaccording to anyofclaims1 to 17.

19. High-energy capacitor comprising the multilayer structureaccording to anyofclaims1 to 17.P2024,0579 WO N April16,2025 -50 - 20.Piezoelectricdevice comprising the multilayer structure according to anyofclaims1 to 17.

21. Electrocaloric solid-state cooling device compr ising amultilayer structure according to any of claims 1 t o 17.

22. Ferroelectric memory device comprising the mult ilayerstructure according to anyofclaims1 to 17.

23. Thermistor device comprising the multilayer str uctureaccording to anyofclaims1 to 17.

24. Pyroelectric device comprising the multilayer s tructureaccording to anyofclaims1 to 17.

25. Microfluidic pump comprising the multilayer str uctureaccording to anyofclaims1 to 17.

26. Process of forming a multilayer structure, wher einon a main surface of a semiconductor or insulator s ubstratean adhesion layerisarranged, above the adhesion layeran electrode containing a noble metalora conductive oxide isarranged,above the electrode an electroceramic material is d eposited.

27. Process according to claim 26, wherein the elec troceramiclayer is a PZT ceramic layer that is formed includi ng atleasttwo steps,wherein a firstsolution comprising a firstZr / Tiratio is deposited above the electrode and a firstsublayeroftheelectroceramic layer is formed by drying and / or ann ealing,P2024,0579 WO N April16,2025 -51 -a second solution comprising a second Zr / Ti ratio i sdeposited above the first sublayer of the electroce ramiclayer,wherebya second sublayerisformed, wherein the second Zr / Tiratio issmallerthan the first Zr / Tiratio. 28.Processaccording to claim 27,wherein a third solutioncomprising a third Zr / Ti ratio is deposited above t he secondsublayer of the electroceramic layer, whereby a thi rdsublayerisformed,wherein the third Zr / Ti ratio is smaller than the f irst andthe second Zr / Tiratio.

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