DE102024115938B4 - Multilayer structure and methods for producing a multilayer structure - Google Patents

Abstract

This application provides a multilayer structure. This multilayer structure consists of a semiconductor or insulator substrate. The substrate has a main surface with a surface roughness (Ra) of 2 µm or less. An electrode containing a noble metal or a conductive oxide is positioned over this main surface. An electroceramic layer is positioned above the electrode. An adhesion layer is located between the main surface of the substrate and the electrode in the multilayer structure.

Description

The present application relates to a multilayer structure and a method for producing such a multilayer structure.

In the US 2008 / 0 024 563 A1 A piezoelectric thin-film element and its layer structure are revealed. JP 2021 - 88 773 A It reveals a substrate with a piezoelectric layer over it. US 2018 / 0 123 017 A1 reveals a piezoelectric element with multiple piezoelectric layers. US 2016 / 0 181 507 A1 Among other things, it reveals a manufacturing process for a PZT layer. US 2023 / 0 371 385 A1 and the DE 692 23 096 T2 show further piezo elements or piezo structures.

Multilayer or thin-film structures, in general, are used in many technical fields. These often feature electroceramic thin films. Such multilayer structures are used, for example, in high-energy capacitors, ferroelectric storage devices, piezoelectric actuators such as micromirrors or inkjet printheads, microfluidic pumps, and piezoelectric sensors such as pressure sensors, accelerometers, piezoelectric energy harvesters, or electrocaloric solid-state cooling devices, thermistors, or in applications where a material with a high dielectric constant is required. In such devices, the electroceramic thin film within the multilayer structure can form the functional unit.

According to current technology, such multilayer structures are generally formed on or over silicon wafer-based substrates. Such wafers may contain an oxide layer.

• Shelton et al., Adv. Funct. Mater. 22, 2295-2302, 2012 Maeder et al, Jpn. J. Appl. Phys. 37 (4A), 2007-2012, 1998 Halder et al., Appl. Phys. A 87, 705-708, 2007

The formation of PZT layers over silicon-based substrates is, for example, Schwartz et al. (CR Chimie 7, 433-461, 2004 ). Furthermore, the following documents deal with the formation of adhesion layers over silicon wafer-based substrates, which reduce the adhesion between an electrode and the silicon wafer-based substrate:

• Shelton et al., Adv. Funct. Mater. 22, 2295-2302, 2012 Maeder et al, Jpn. J. Appl. Phys. 37 (4A), 2007-2012, 1998 Halder et al., Appl. Phys. A 87, 705-708, 2007

However, these or similar approaches have the disadvantage that the adhesion of electrodes in functional multilayer devices with ceramic layers may still be insufficient. For example, delamination is likely in some cases under certain conditions.

Accordingly, one objective of the present invention is to provide an improved multilayer structure.

Accordingly, at least some of the disadvantages described above are at least partially overcome or compensated for by the subject matter of claim 1. Furthermore, further preferred embodiments or alternative embodiments are described in the dependent claims.

According to a first embodiment, a multilayer structure is provided. This multilayer structure comprises a semiconductor or insulator substrate. The substrate has a main surface. An electrode containing a noble metal or a conductive oxide is arranged above this main surface. An electroceramic layer, which imparts function to the multilayer structure, is arranged above the electrode. In the multilayer structure, an adhesion layer is arranged between the main surface of the substrate and the electrode. The adhesion layer can be in direct contact with both the main surface of the substrate and the electrode. The adhesion layer contains a transition metal or a transition metal oxide. The term "transition metal" also includes alloys of transition metals. The term "transition metal oxide" also includes mixed transition metal oxides.

The inventors of the present invention have discovered that adhesion layers based on transition metals or transition metal oxides are able to ensure good adhesion between a semiconductor or insulator substrate and an electrode containing a precious metal or a conductive oxide.

Furthermore, the inventors have discovered that the use of such adhesion layers can reduce or even completely eliminate delamination. Thermal stability can also be improved. This can be important, for example, during the manufacturing process, as the adhesion layer can help prevent the electrode from dewetting from the substrate surface during production. to prevent the formation of the electroceramic layer. Surprisingly, the quality of the electroceramic layer can also be improved.

Any type of substrate that exhibits semiconductor behavior can be understood as a semiconductor substrate. Likewise, any type of substrate that would be considered an electrical insulator in practice can be considered an insulator substrate.

According to one embodiment, a further electrode, which can be referred to as the upper electrode, can be arranged on or above the electroceramic layer. Similarly, the electroceramic layer can be arranged between the previously described electrode, which can be a lower electrode, and the upper electrode.

According to one embodiment, the substrate can be a silicon wafer-based substrate. A silicon wafer-based substrate is defined as any substrate that can be formed from or contains a silicon wafer. The silicon in the silicon wafer-based substrate can be in crystalline or amorphous form. It can also be doped or undoped. The silicon wafer-based substrate can consist of or be made from a single-crystal or polycrystalline silicon wafer. The silicon wafer-based substrate can consist of or be formed from a bare silicon wafer. The silicon wafer-based substrate can also have a portion consisting mainly of elemental silicon and a portion consisting of or containing silicon oxide. The term "silicon wafer-based substrate" also includes silicon-on-insulator (SOI) wafers. Such SOI wafers can have multiple layers. For example, they can have a so-called silicon handle layer and a silicon device layer, separated by an embedded silicon oxide layer.

According to one embodiment, the semiconductor or insulator substrate can be a sapphire substrate. "Sapphire substrate" is understood to mean what a person skilled in the art would normally understand by that term. A sapphire substrate can be an aluminum oxide-based material crystallized in a hexagonal crystal structure.

According to another embodiment, a semiconductor or insulator substrate can be a glass substrate. Here, any type of silicon oxide-based glass can be understood as a glass substrate.

The semiconductor or insulator substrates described above allow for the easy production of multilayer structures in industrially accessible high volumes. However, the adhesion of electrodes selected from precious metals or conductive oxides to such substrates can be poor. Therefore, an adhesion layer made of a transition metal or transition metal oxide can improve adhesion in these cases.

In particular, the inventors found that electrode materials often cannot be deposited on pure silicon because chemical exchange, such as diffusion, can occur and impair the properties of the substrate or the electrode. If the electrode material is deposited on an oxidized wafer, i.e., on silicon oxide, adhesion is often very poor and delamination is likely. The adhesion layer according to the invention can help to improve adhesion and reduce the diffusion of substances or atoms, as explained in more detail below.

According to one embodiment, the adhesion layer can comprise a first adhesion sublayer with a transition metal and a second adhesion sublayer with a transition metal oxide. The inventors assume that the presence of both a transition metal and a transition metal oxide can not only improve adhesion or contribute to reducing delamination, but also reduce the diffusion or migration of chemical elements between the layers. Furthermore, the inventors assume that the thermal stability of the noble metal electrode can be improved. Accordingly, the electroceramic layer can be protected from elements that diffuse from the substrate into the electroceramic layer. Likewise, the properties of the substrate, particularly in the case of a semiconductor substrate, remain largely unaffected, since no material diffuses from the electroceramic layer into the substrate.

In the embodiment described above, in which there is a first adhesion sublayer and a second adhesion sublayer, the transition metal of the first adhesion sublayer can be the same or different. separate from the transition metal that forms the transition metal oxide of the second adhesion sublayer.

Within the scope of this application, the term "transition metal" can be understood to mean anything generally understood by that term in the technical field. In particular, it can include at least any transition metal of periods 4, 5, and 6 of the periodic table. Preferably, the transition metal here and in the following may be titanium, tantalum, or tungsten, or alloys of these metals. Of these, tantalum has proven particularly advantageous in several cases. In particular, tantalum in combination with a platinum electrode, as described below, has proven to be especially preferred.

According to one embodiment, the first adhesion sublayer, comprising the transition metal, can be in direct contact with the substrate. The second adhesion sublayer, comprising the transition metal oxide, can then be arranged on top of it. According to another embodiment, a reverse stacking arrangement can be implemented, in which the second adhesion sublayer with the transition metal oxide is arranged directly on the substrate, and the first adhesion sublayer with a transition metal is arranged on top of it.

In another embodiment, the first adhesion sublayer, containing the transition metal, is arranged directly on the substrate as described above. A second adhesion sublayer, containing the transition metal oxide, is arranged above it. Additionally, a third adhesion sublayer, again containing a transition metal, can be arranged above the second adhesion sublayer. This results in a three-layer structure in which the oxide-containing second sublayer is sandwiched between the first and third sublayers containing the transition metal. In some cases, a structure with these three adhesion sublayers can be particularly advantageous. The inventors found that the first and third adhesion sublayers may offer improved adhesion and/or improved thermal stability. The second adhesion sublayer, containing the oxide, can contribute to improved suppression of elemental diffusion between the layers. According to another embodiment, the reverse structure can also be formed, in which a transition metal-based adhesion sublayer is sandwiched between two transition metal oxide-based adhesion sublayers.

According to one embodiment, the thickness of the adhesion layer can be between 1 and 100 nm. Preferably, it can be between 10 and 50 nm. Even more preferably, it can be between 15 and 100 nm, for example, between 15 and 50 nm or between 15 and 30 nm. The inventors of the present invention have found that if the adhesion layer is too thin, delamination is more likely and the diffusion-inhibiting properties may also be reduced. The adhesion and diffusion-inhibiting properties described above are particularly desirable for thicknesses above 10 nm.

As described above, the electrode comprises or consists of a precious metal or a conductive oxide. The term "precious metal" can be understood in its technical sense. Within the context of this application, the term precious metal also includes alloys of precious metals. At a minimum, ruthenium, rhodium, palladium, silver, osmium, iridium, platinum, and gold can be considered precious metals. Of these, iridium and platinum have proven particularly advantageous as electrodes. The combination with tantalum-containing adhesion layers has proven especially effective. The above statements regarding mass transfer on bare silicon surfaces and very poor adhesion to silicon oxide surfaces apply particularly to iridium and even more so to platinum as electrode materials. Therefore, an adhesion layer, and especially one containing tantalum, is preferred.

In another embodiment, the electrode can consist of a conductive oxide. In principle, any conductive oxide can be used. It can be an oxide of a metal. Examples of preferred conductive oxides are iridium oxide, rhodium oxide, rhenium oxide, ruthenium oxide, lanthanum nickel oxide, or strontium ruthenium oxide. The chemical formulas for these oxides can be _IrO₂ , _RhO₂ , _ReO₂ , _RuO₂ , or _SrRuO₃ , but the elemental ratios are generally not limited to those given in the formulas. It has been found that the adhesion layer described above can provide particularly good adhesion to insulating or semiconductor substrates.

According to one embodiment, the electrode thickness can range between 50 nm and 500 nm. A smaller thickness may be preferred, particularly for more expensive precious metals, as is the case, for example, between... The wavelengths are typically between 100 nm and 300 nm, or between 150 and 250 nm. Furthermore, excessively thick electrode layers tend to delaminate due to internal stresses.

• • Hohe Dielektrizitätskonstante, die z. B. in Kondensatoren verwendet werden kann;
• • Pyroelektrizität, die zum Beispiel in Infrarotsensoren verwendet werden kann;
• • Ferroelektrizität, die zum Beispiel in Speichern verwendet werden kann;
• • Piezoelektrizität, die z. B. in den an anderer Stelle in der Anmeldung beschriebenen Geräten verwendet werden kann;
• • Temperaturabhängiger Widerstand; dieser kann durch keramische Thermistormaterialien, wie Materialien mit positivem Temperaturkoeffizienten (PTC) oder Materialien mit negativem Temperaturkoeffizienten (NTC), bereitgestellt werden.

In this application, an electroceramic layer can be understood in the general technical sense. It is preferred that the electroceramic imparts functionality to the multilayer structure. Such functionality can be:

• • High dielectric constant, which can be used, for example, in capacitors;
• • Pyroelectricity, which can be used, for example, in infrared sensors;
• • Ferroelectricity, which can be used, for example, in storage devices;
• • Piezoelectricity, which can be used, for example, in the devices described elsewhere in the application;
• • Temperature-dependent resistance; this can be provided by ceramic thermistor materials, such as positive temperature coefficient (PTC) or negative temperature coefficient (NTC) materials.

According to one embodiment, the electroceramic in the multilayer structure can comprise or consist of a piezoelectric ceramic material. The inventors of the present invention have found that the structure described above, with a precious metal-based electrode or an electrode based on a conductive oxide, which adheres to a semiconductor- or insulator-based substrate by means of an adhesion layer, can be used to produce high-quality piezoelectric thin films in such multilayer structures. The piezoelectric ceramic material can be in direct contact with the electrode. Alternatively, a nucleation layer can be arranged between the electrode and the piezoelectric ceramic material. The following piezoelectric ceramic materials have proven to be preferred: Pb[ _{ZrxTi1 -x} ] ₃ (abbreviated PZT), (1-x) Pb[Mg1 _/ 3Nb2/ _{3O3 ]} -x _PbTiO3 (abbreviated PMN-PT), [ _{KxNa1 -x} ] _NbO3 (abbreviated KNN), (1-x) _BiFeO3 -x _BaTiO3 (abbreviated BFO-BT), Ba[ _{ZrxTi1 -x} ] _O3 (abbreviated BZT), (1-x) [Bi1 _/2Na1 / ₂ ] _TiO3 -x [Bi1 _/2K1 / ₂ ] _TiO3 (abbreviated BNT-BKT), (1-x) _BiFeO3 -x Ba[ _{TiyZr1 -y} ] _O3 (abbreviated BFO-BZT), AlMgZrN, or [Al _x Sc _1-x ]N. In all these examples, x and y are numbers between zero and one, i.e., 0 ≤ x ≤ 1 and 0 ≤ y ≤ 1. The electroceramic materials mentioned above can be modified by doping. Doping is the intentional addition of impurities to alter the electrical and/or piezoelectric properties of the electroceramic layer.

According to one described embodiment, a seed layer can be arranged between the piezoelectric material, which in this case forms the electroceramic layer, and the electrode. Suitable seed layer materials include lead titanate ( _PbTiO₃ ), lanthanum nickelate ( _LaNiO₃ ), lead oxide (PbO), or titanium oxide ( _TiO₂ ).

According to one embodiment, an electroceramic layer can comprise a ceramic material to realize one of the functionalities mentioned above. The inventors of the present invention initially observed the advantages of the inventive design using an adhesive layer for piezoelectric materials as described above. To their surprise, the inventors found that, in general, any electroceramic layer can benefit from such a design. In particular, the inventors found that thermistor materials also exhibit improved properties when the design described above, with an adhesive layer between a lower electrode and the underlying substrate, is used.

Accordingly, the electroceramic layer can, according to one embodiment, consist of or incorporate a thermistor material. Of the materials with temperature-dependent resistance, the following have proven particularly advantageous: Ni-Mn-Cu oxides, Ni-Mn-Co oxides, Co-Fe oxides, Cr-Co-Ba-Fe-Bi oxides, and barium titanate ( _BaTiO₃ ). According to one embodiment, the thermistor materials can have a spinel-based or perovskite structure.

In general, the thickness of the electroceramic layer is not limited and can be selected according to the application. According to one embodiment, the electroceramic layer can have a thickness of 10 nm to 20 µm. Preferably, a lower range for the thickness can be 20 nm, 50 nm, or 100 nm. Preferably, an upper range for the thickness can be 10 µm, 5 µm, 2 µm, or 1 µm. For example, a thickness of 100 nm to 5 µm, such as 1 µm to 3 µm or 1.7–2.5 µm, can be selected. Values for the lower and upper ranges can each replace the lower and upper values in all these examples.

The inventors have found that the quality of the electroceramic layer can be improved by the structure described above, in particular by an adhesion layer. Specifically, according to one embodiment, the electroceramic layer can have crystal grains in the size range of 10 to 1000 nm.

According to another embodiment, the adhesion layer can contribute to the formation of high-quality electroceramic layers, in particular with crystalline columns extending over the entire thickness of the electroceramic layer.

According to another embodiment, the electroceramic layer can have a granular structure. For example, grains ranging in size from 10 nm to 1 µm can be present. Such a granular structure can be achieved, for example, by electroceramic layers made of barium titanate or Mn-Co-Ni oxide.

According to one embodiment, a multilayer structure is described which can have the arrangement described above. Furthermore, it can have a second electrode arranged on a second main surface of the substrate. The second main surface can be a surface opposite the first main surface described above. A second adhesion layer is arranged between the second main surface and the second electrode. The second adhesion layer can have the properties described above for the first adhesion layer. Accordingly, a symmetrical multilayer structure can be formed in its layering.

Preferably, the first and second adhesion layers can be made of the same material, as this can simplify manufacturing. However, the materials can also be different. Similarly, the electrodes on both sides can be made of the same material, which may be preferred due to simplified manufacturing. Again, the electrode materials can differ.

According to one embodiment, a second electroceramic layer can also be arranged above the second electrode in this case. The electroceramic layer can have the properties described above. It can be the same as, or different from, the first electroceramic layer.

The present invention is particularly suitable for the production of such symmetrical structures, as this can contribute to further increasing the yield. Even with rougher surfaces, several advantages can be achieved through simplified handling, which are described below.

According to another embodiment, which can be combined with any of the embodiments described above, the multilayer structure can include a further electrode arranged on the electroceramic layer. This electroceramic layer can be referred to here as the first electroceramic layer. The further electrode described here can be referred to as the first upper electrode.

According to a modification of the previous embodiment, a further electroceramic layer, which may be referred to or addressed here as the second electroceramic layer, can be arranged on or above the first upper electrode. The properties described above can apply to the further electrode and the further electroceramic layer. The material of the further electroceramic layer can be the same as that of the lower or first electroceramic layer. Depending on the application, however, it can also be different. Similarly, the electrode can also have the same material as the other electrode, but it can also be different. A further upper electrode can be arranged on the stack. Accordingly, a structure is provided with the substrate, the adhesion layer, the lower electrode, the first electroceramic layer, the first upper electrode, the second electroceramic layer, and the second upper electrode. Similarly, several layers of electrodes and electroceramic layers can also be stacked on top of each other. Preferably, such stacks are capped by an upper electrode.

According to one embodiment, the multilayer structure according to the present invention can be used in micromirrors. In this case, it is advantageous for the electroceramic layer to comprise a piezoelectric material. The deflection of the mirror can then be driven by the piezoelectric multilayer structures. Alternatively, the invention can be used in high-energy capacitors, ferroelectric storage devices, piezoelectric actuators such as micromirrors, microfluidic pumps, or inkjet printheads. It can be used in piezoelectric sensors such as pressure sensors or accelerometers. Furthermore, it can be used in piezoelectric energy harvesters or electrocaloric solid-state cooling devices. In principle, it can also be used in any other type of piezoelectric device.

According to one embodiment, the main surface of the substrate can be polished or even mirror-polished. A mirror-polished surface can have a surface roughness ( _Ra ) of less than 20 nm. A mirror-polished surface can increase the yield of the functional devices fabricated with the multilayer substrate. These mirror-polished substrates are preferably silicon substrates with a mirror-polished surface.

The inventors discovered, however, that mirror-polished surfaces are not always necessary due to the adhesion layer. They found that substrates with a roughness ( _Ra ) of up to 2 µm can be used. The inventors determined that the use of an adhesion layer eliminates the need for time-consuming polishing. Preferably, the surface roughness is a maximum of 1 µm. Any roughness below 2 µm, and even more preferably below 1 µm, is technically feasible according to the invention. Unpolished or only partially smoothed surfaces can have a surface roughness of over 10 nm, over 20 nm, or even over 50 nm or 100 nm. Accordingly, a surface roughness between 10 nm and 2 µm, such as 20 nm and 1 µm, is well suited according to the invention. The other values mentioned above can replace the upper or lower values. Even on rough surfaces, the inventors have found that using an adhesion layer can result in exceptionally high quality of the electroceramic film. Generally, polishing is a complicated and expensive process. Furthermore, it can introduce impurities that may impair the performance and yield of the components. Therefore, this aspect can help overcome these problems.

According to a further embodiment, a method for producing a multilayer structure is described. The advantages described above apply accordingly to this method, insofar as they are applicable.

According to one embodiment of the method for forming a multilayer structure, an adhesion layer is first arranged on a major surface of a semiconductor-based or insulator-based substrate. The adhesion layer can be deposited on the substrate. Preferably, the adhesion layer is produced by physical deposition from the gas phase, e.g., by magnetron sputtering or evaporation. A lower electrode containing a noble metal or a conductive oxide is arranged on the adhesion layer. The lower electrode can be arranged or deposited in any desired manner. Preferably, chemical or physical deposition from the gas phase, e.g., by magnetron sputtering or evaporation, can be used. Subsequently, an electroceramic material is deposited on the lower electrode. The electroceramic materials can be, for example, those defined above. For the deposition of the electroceramic material, various methods can be used. B. chemical solution deposition, magnetron sputtering, atomic layer deposition or pulsed laser deposition can be used.

The electroceramic layer can be deposited successively in thin layers. For example, layers with a thickness of 10 to 200 nm can be stacked on top of each other in each deposition step. In chemical solution deposition, a precursor solution containing an electroceramic starting material can first be deposited. The deposition method can be, for example, spin coating. Subsequently, the solvents can be removed from the precursor solution by drying at elevated temperature. Any organic residues can then be removed by a pyrolysis step. The drying and pyrolysis can be carried out sequentially at different temperatures or during a single heating process. A heating step (annealing step) can then be performed, leading to the crystallization of the previously amorphous metal oxide. To achieve an electroceramic layer on the order of several micrometers, such a deposition process can be repeated.

According to one embodiment, a high-quality PZT layer can be formed by deposition and spin coating of a PZT solution onto the substrate. The PZT film can be formed from a single solution that creates a sublayer of the PZT film. It can also be produced from two or more solutions with different concentrations of PZT components, each forming sublayers of a sublayer. One solution can be Zr-rich and a second solution can be Ti-rich. The principles of the embodiment described below can be applied to the cases involving two or more solutions.

According to one embodiment, a method with at least three deposition steps can be used. In this method, at least one first sublayer is produced using a first solution. A second sublayer is deposited or arranged over the first sublayer using a second solution, and a third sublayer is produced using a third solution deposited over the second sublayer. The electroceramic material for this approach is preferably PZT or contains PZT. In this case, the first solution has a high zirconium-to-titanium ratio. The first solution is deposited over the lower electrode, forming the first sublayer. The formation of the first sublayer can be carried out in one or more deposition steps. Subsequently, the first sublayer is annealed. If more than one deposition step is performed, intermediate heating can be carried out. Similarly, a second sublayer is formed from the second solution, which has a medium zirconium-to-titanium ratio. The medium zirconium-to-titanium ratio is a lower ratio than that of the first solution. Heating can be performed after deposition. A third sublayer is formed above the second sublayer, which in turn can comprise one or more layers. This third sublayer is formed with a solution containing a low zirconium-to-titanium ratio, meaning that the proportion of zirconium relative to titanium is the lowest compared to the other solutions. In other words, the first solution can be described as zirconium-rich. The second solution can be described as a morphotropic phase boundary solution, and the last solution as a titanium-rich solution. The resulting sublayers can be described as a zirconium-rich sublayer, a morphotropic phase boundary sublayer, and a titanium-rich sublayer.

This approach has the advantage that chemical gradients during annealing or crystallization can be reduced or avoided.

This principle can be applied to more than three solutions. For example, four, five, or even more solutions with different concentrations of Zr and Ti can be used, with the concentration gradually changing from Zr-rich to Ti-rich. As described above, a two-solution approach can also be used, likewise changing from Zr-rich to Ti-rich.

• 1 zeigt einen schematischen Querschnitt eines ersten Ausführungsbeispiels eines Mehrschichtaufbaus.
• 2 zeigt einen schematischen Querschnitt eines zweiten Ausführungsbeispiels eines Mehrschichtaufbaus.
• 3 zeigt einen schematischen Querschnitt eines dritten Ausführungsbeispiels eines Mehrschichtaufbaus.
• 4 zeigt einen schematischen Querschnitt eines Teils eines vierten Ausführungsbeispiels eines Mehrschichtaufbaus.
• 5 zeigt einen schematischen Querschnitt eines Teils eines fünften Ausführungsbeispiels eines Mehrschichtaufbaus.
• 6 zeigt einen schematischen Querschnitt eines Teils eines sechsten Ausführungsbeispiels eines Mehrschichtaufbaus.
• 7 zeigt einen schematischen Querschnitt eines Teils eines siebten Ausführungsbeispiels eines Mehrschichtaufbaus.
• 8 zeigt eine polarisationselektrische Feldschleife (Englisch: polarization-electric field loop) eines Ausführungsbeispiels eines PZT-Dünnfilms innerhalb eines Mehrschichtaufbaus.
• 9 zeigt eine relative Permittivitäts-Elektrizitätsfeld-Schleife (Englisch: relative permittivity-electric field loop) eines Ausführungsbeispiels einer PZT-Dünnschicht innerhalb eines Mehrschichtaufbaus.
• 10 zeigt eine bipolare Verschiebungskurve Englisch: bipolar displacement curve) eines Ausführungsbeispiels einer PZT-Dünnschicht in einem Mehrschichtaufbau.
• 11 zeigt eine unipolare Verschiebungskurve (Englisch: unipolar displacement curve) eines Ausführungsbeispiels einer PZT-Dünnschicht in einem Mehrschichtaufbau.
• 12 zeigt ein Foto eines ersten Ausführungsbeispiels einer MEMS-Spiegelvorrichtung.
• 13 zeigt ein Lichtmikroskopbild der beispielhaften Ausführungsform einer MEMS-Spiegelvorrichtung.
• 14 zeigt eine optische Sichtfeldmessung als Funktion der Antriebsfrequenz für die schnelle Achse der MEMS-Spiegelvorrichtung.
• 15 zeigt eine optische Sichtfeldmessung als Funktion der Antriebsfrequenz für die langsame Achse der MEMS-Spiegelvorrichtung.
• 16 zeigt eine schraffiert wiedergegebene Repräsentation eines Falschfarbgraph (Englisch: false color plot graph) als Funktion der Achsenantriebsfrequenz für beide Achsen bei der horizontalen Bewegung des Spiegels.
• 17 zeigt eine schraffiert wiedergegebene Repräsentation eines Falschfarbgraph als Funktion der Achsenantriebsfrequenz für beide Achsen bei der vertikalen Bewegung des Spiegels.
• 18 zeigt eine lichtmikroskopische Aufnahme einer Vorrichtung mit einer delaminierten unteren Elektrode.
• 19 zeigt eine lichtmikroskopische Aufnahme der Vorrichtung aus 18.
• 20 zeigt ein Lichtmikroskopbild eines Ausführungsbeispiels einer erfindungsgemäßen MEMS-Vorrichtung.
• 21 zeigt eine vergrößerte lichtmikroskopische Aufnahme des in 20 gezeigten Ausführungsbeispiels ohne Delamination.
• 22 zeigt ein rasterelektronenmikroskopisches Querschnittsbild eines Ausführungsbeispiels eines NTC-Dünnschicht-Mehrschichtbauteils.
• 23 zeigt ein Flussdiagramm eines Herstellungsverfahrens für eine Ausführungsform eines Mehrschichtaufbaus.

The invention is described below with reference to exemplary embodiments and figures. The figures also include schematic drawings. Such schematic drawings are not to scale, and dimensions or dimensional ratios may be distorted. Accordingly, lengths or ratios cannot be directly determined from the schematic figures unless otherwise indicated.

• 1 shows a schematic cross-section of a first embodiment of a multilayer structure.
• 2 shows a schematic cross-section of a second embodiment of a multilayer structure.
• 3 shows a schematic cross-section of a third embodiment of a multilayer structure.
• 4 shows a schematic cross-section of part of a fourth embodiment of a multilayer structure.
• 5 shows a schematic cross-section of part of a fifth embodiment of a multilayer structure.
• 6 shows a schematic cross-section of part of a sixth embodiment of a multilayer structure.
• 7 shows a schematic cross-section of part of a seventh embodiment of a multilayer structure.
• 8 shows a polarization-electric field loop of an embodiment of a PZT thin film within a multilayer structure.
• 9 shows a relative permittivity-electric field loop of an embodiment of a PZT thin film within a multilayer structure.
• 10 shows a bipolar displacement curve (English: bipolar displacement curve) of an embodiment of a PZT thin film in a multilayer structure.
• 11 shows a unipolar displacement curve of an embodiment of a PZT thin film in a multilayer structure.
• 12 shows a photograph of a first embodiment of a MEMS mirror device.
• 13 shows a light microscope image of an exemplary embodiment of a MEMS mirror device.
• 14 shows an optical field of view measurement as a function of the drive frequency for the fast axis of the MEMS mirror device.
• 15 shows an optical field of view measurement as a function of the drive frequency for the slow axis of the MEMS mirror device.
• 16 shows a hatched representation of a false color plot graph as a function of the axis drive frequency for both axes during the horizontal movement of the mirror.
• 17 shows a hatched representation of a false color graph as a function of the axis drive frequency for both axes during the vertical movement of the mirror.
• 18 shows a light microscopic image of a device with a delaminated lower electrode.
• 19 shows a light microscopic image of the device from 18 .
• 20 shows a light microscope image of an embodiment of a MEMS device according to the invention.
• 21 shows an enlarged light microscopic image of the in 20 The illustrated embodiment without delamination.
• 22 shows a scanning electron microscope cross-sectional image of an embodiment of an NTC thin-film multilayer component.
• 23 shows a flowchart of a manufacturing process for one embodiment of a multilayer structure.

In 1 Figure 1 shows a schematic cross-sectional view of a first embodiment of a multilayer structure 1. In this exemplary embodiment, an adhesion layer 3 is arranged on a silicon wafer-based substrate 2. The adhesion layer 3 comprises a transition metal or a transition metal oxide. A transition metal can be any transition metal from the fourth, fifth, or sixth period of the periodic table. An electrode layer 4 is located on the adhesion layer 3. The electrode 4 can contain or consist of a noble metal or a conductive oxide. In this stack, the electrode layer 4 can be referred to as the bottom electrode. Above the bottom electrode 4 is an electroceramic layer 5. The electroceramic layer 5 can be a dielectric, pyroelectric, ferroelectric, piezoelectric, or thermistor ceramic layer. An upper electrode 6 is arranged on the electroceramic layer 5. The upper electrode 6 can be any type of conductive electrode. For example, the upper electrode 6 can be a noble metal electrode or a conductive oxide electrode. It can be made of the same or a different material than the lower electrode.

The materials described for these various layers can be those mentioned in the introduction. A particularly preferred example for substrate 2 is a silicon-on-insulator wafer (SOI wafer). A tantalum-containing adhesion layer 3 is particularly preferred. It can comprise metallic tantalum and/or tantalum oxide. A platinum electrode 4 is preferably arranged on this. The electroceramic layer 5 can preferably be The electrode should ideally be a PZT material or a thermistor material such as an NTC material. A chromium/gold electrode is preferred as the upper electrode 6.

The SOI wafer substrate can have the following internal layer structure from bottom to top: A 450 µm thick silicon handle layer is located on a 1.5 µm thick silicon oxide layer. A 1 µm thick silicon oxide buried layer is positioned above the silicon handle layer. A 150 µm thick silicon device layer is positioned on top of the embedded oxide layer. A 1 µm thick silicon oxide layer is positioned on top of the silicon device layer.

In a preferred embodiment with an SOI layer, the tantalum adhesion layer has a thickness of 20 nm. The lower platinum electrode 4 can have a thickness of 200 nm. The PZT electroceramic layer 5 can have a thickness of 1.7 µm. The upper electrode can be formed with a chromium and a gold electrode. These can be implemented as successively applied layers. A chromium layer can be 20 nm thick and can be positioned between the PZT layer and the gold layer. The gold layer can have a thickness of 200 nm.

Although not explicitly shown, a nucleation layer can be positioned between the electroceramic layer and the electrode in many cases. This nucleation layer can further facilitate the crystalline and/or oriented growth of the electroceramic layer.

The present structure has the advantage that an electroceramic layer 5, such as the electroceramic PZT layer or the electroceramic NTC layer, is formed with a high degree of orientation and good adhesion to the substrate. Furthermore, the multilayer structure can be produced without polishing the substrate 2 or otherwise controlling the surface roughness. As will be shown below, excellent performance can be achieved with such multilayer structures.

2 shows a schematic cross-section of a second embodiment of a multilayer structure 1. The multilayer structure 1 of the 2 The upper part is identical to the multi-layer structure of the 1 , i.e., with respect to the layers with reference numerals 2, 3, 4, 5, and 6, which are identical to those described for the first embodiment. However, a second adhesion layer 3', a second electrode 4', a second electroceramic layer 5', and a second upper electrode 6' are also arranged on the other main surface of the substrate 2. The materials of these layers can correspond to those of the first adhesion layer 3, the first lower electrode 4, the first electroceramic layer 5, and the first upper electrode 6. Accordingly, a largely symmetrical layer arrangement results with respect to the layers with reference numerals 2 to 6.

In 3 Figure 1 shows a schematic cross-section of a third embodiment of a multilayer structure 1. This third embodiment of a multilayer structure 1 is a modification of the one described in Figure 1. 1 In the first embodiment shown, the first adhesion layer 3, the first lower electrode 4, the first electroceramic layer 5, and the first upper electrode 6 are arranged on the substrate 2. A second electroceramic layer 5'' is arranged above the first upper electrode 6. The second upper electrode 6'' is arranged above the second electroceramic layer 5''. In this arrangement, the first upper electrode 6 acts as the lower electrode for the second electroceramic layer 5''. The materials of the second electroceramic layer 5'' can be selected from the same materials as the material of the first electroceramic layer 5. Similarly, the materials of the second upper electrode 6'' can be selected from the same materials as the material of the first electrode 6.

In a similar way to in 3 As shown, several further electroceramic layers and top electrodes can be stacked alternately. Preferably, such a stack is terminated by a top electrode.

The third embodiment can of course be combined with the second embodiment, i.e., with the two-sided arrangement as described in 2 This is illustrated. This can lead to a symmetrical stacking, where both sides have the same number of stacks. Alternatively, a stack can be formed where both sides have a different number of electroceramic layers and top electrodes.

4 shows a schematic cross-section through part of a fourth embodiment of a multilayer structure 1. 4 can be an arrangement of an adhesion layer 3 on a substrate 2 in the first, second or third embodiment of a multilayer structure, as described in the 1 , 2 or 3 The fourth exemplary embodiment is represented by the figure. In this fourth exemplary embodiment, the adhesion layer is arranged on the substrate 2. The adhesion layer 3 comprises or consists of a single material type and has no internal material layer boundaries. In the present case, the adhesion layer consists only of a transition metal or an alloy of transition metals.

5 shows a schematic cross-section through part of a fifth embodiment of a multilayer structure 1. 5 An arrangement of an adhesion layer 3 on a substrate 2 in the first, second and third embodiments of a multilayer structure 1, as shown in the 1 , 2 or 3 The diagram illustrates this. In this case, the adhesion layer comprises a first adhesion sublayer 3a, which consists of a transition metal or an alloy of transition metals. A second adhesion sublayer 3b, which comprises or consists of a transition metal oxide, is arranged on top of this. This means that the transition metal oxide layer can also be a mixed oxide containing a transition metal oxide. The transition metal of the transition metal oxide can be the same as or different from the transition metal of the first adhesion sublayer 3a.

6 The sixth embodiment of a multilayer structure 1 shows a structure that is essentially similar to that of the 5 but with a reversed stacking of the first adhesion sublayer 3a and the second adhesion sublayer 3b. Here in the sixth embodiment, the second adhesion sublayer 3b, which comprises or consists of a transition metal oxide, is arranged directly on the substrate 2. The first adhesion sublayer 3a, which comprises or consists of the transition metal, is arranged above it. The stacking in this exemplary embodiment of 6 can an arrangement of an adhesion layer 3 on a substrate 2 in the first, second or third embodiment of a multilayer structure 1, as described in the 1 , 2 or 3 is depicted, represent.

7 shows a schematic cross-section of part of a seventh embodiment of a multilayer structure 1, which is a modification of the one described in 5 The stacking shown represents the fifth embodiment. On the first adhesion sublayer 3a, the second adhesion sublayer 3b is stacked in the same way as in 5 The second adhesion sublayer 3b is arranged as follows: A third adhesion sublayer 3a', which contains or consists of a transition metal, is arranged on the second adhesion sublayer 3b. The transition metal in the first and third adhesion sublayers 3a and 3a' can be identical or different. Otherwise, the properties described above apply.

Not shown, but also possible, is a reversed arrangement of the adhesion sublayers. For example, a transition metal-containing adhesion sublayer can be sandwiched between two transition metal oxide-containing adhesion sublayers.

For those in the 4 , 5 , 6 until 7 In the depicted adhesion layers, the inventors have discovered that the use of a transition metal can improve the adhesion between a silicon wafer-based substrate, and more generally between a semiconductor or insulating substrate, and an electrode such as a platinum or other noble metal electrode. Furthermore, the inventors have found that the transition metal can at least partially prevent the migration of elements or substances between the layers. In particular, when an oxide layer is present, the diffusion or migration of ions appears to be suppressed even more effectively.

In the 8 , 9 , 10 until 11 The results of the electrical and piezoelectric characterization measurements are presented. The measurements were performed on a multilayer structure as described in 1 The process was carried out on an SOI wafer with the properties described above, where the piezoelectric layer had a thickness of 1.7 µm. The layer thicknesses were as described above. A 25 nm thick chromium layer and a 200 nm thick gold layer were sputtered over the electroceramic PZT layer to form the top electrode. Cantilever components with a large-area top electrode of 19.45 ^mm² were cut from these and used for characterization. All measurements were performed on the same sample.

8 This shows a diagram of the polarization with respect to the electric field, recorded at 10 Hz. The curve with the larger y-axis deflection, indicated by a dashed line and the corresponding left-pointing arrow, corresponds to the left y-axis, labeled "Polarization." The curve with the solid line, which also shows a smaller The extent in the y-direction is associated with the measured current density, as indicated by the corresponding right-pointing arrow. The polarization-electric field loop clearly shows ferroelectric switching with a remanent polarization P _{_r} of approximately 20 µC cm ^{^-2} and a coercive field E_{_c} of approximately 30 kV cm ^{^-1}.

9 This figure shows the relative permittivity and the loss factor as a function of the DC electric field, measured at a low signal frequency of 225 Hz and a small signal amplitude of 5 kV ^cm⁻¹ . The curve shown higher up in the figure, represented by the open circles and the dashed line, is the measurement of the relative permittivity associated with the left y-axis, as indicated by the left-pointing arrow. The curve shown lower in the figure, represented by solid circles and a solid line, corresponds to the loss factor on the right y-axis, as also indicated by the small solid arrow pointing to the right. The measurements clearly show that the relative permittivity is approximately 1700 at a bias field of zero, while the loss remains below 10%. The high quality of the film is further demonstrated by the fact that no leakage was observed at high DC fields.

10 The graph shows a bipolar displacement curve recorded at 10 Hz. The bipolar displacement curve is symmetrical and exhibits the typical butterfly shape of high-quality PZT films.

11 The graph shows a unipolar displacement curve. The values summarized in Table 1 were derived from this curve. Table 1: -e _31,f ⁺ -e _31,f ^- Average of |e _31,f | Δe _31,f example of 11 22.43 C m ^-2 17.60 C m ^-2 20.02 C m ^-2 4.84 C m ^-2

As can be seen from Table 1, the effective transverse piezoelectric coefficient |e _31,f | was determined to be 20 C ^m⁻² . No hot galvanizing of this thin film under a DC electric field was performed during this measurement. Within the scope of the invention, it would be possible to further improve the piezoelectric thin film by additional hot galvanizing. Doping can also further improve the piezoelectric thin film.

In the 12 and 13 An embodiment of a bi-resonant 2D-MEMS high-frequency micromirror 10 is shown. 12 shows a photo of the device. 13 Figure 1 shows a microscopic image of the micromirror. The micromirror 10 has a mirror plate or mirror surface 13 with a diameter of 1.5 mm. The mirror can be tilted or set into oscillation along the so-called fast axis 12 and the slow axis 11. During operation, the actuator ring 14 is subjected to voltage.

The actuator ring 14 comprises a multilayer structure according to the invention. Its structure is essentially identical to that described in 1 The stacking shown. In particular, it is applied to an SOI substrate with the properties as shown in 1 A 20 nm thick tantalum layer is deposited as an adhesion layer. The lower electrode is formed from a 200 nm thick platinum electrode. The electroceramic layer is a 1700 nm thick PZT layer, which can be produced, for example, using the method described below. The upper electrode is formed from a 20 nm thick chromium layer and a 200 nm thick gold layer.

In the 14 , 15 , 16 until 17 The measurements of the optical field of view (FoV) are shown. 14 shows measurements of the optical field of view for the drive frequency of the fast axis at different voltages. The data points are always shown together with a fit curve. Similarly, in 15 The optical field of view measurement for the slow axis at different voltages is shown. These diagrams in 14 and 15 represent 1D operations at different drive voltages.

As can be seen, the achieved values for the maximum optical field of view demonstrate the stability and adhesion strength achieved with an adhesive layer. The adhesion is so good that the limiting factor is not the layer stack, but the mechanical strength of the underlying silicon-based substrate. The maximum achievable optical field of view is shown. Furthermore, the measurements in the 14 and 15 , that the layer stack even generates enough force and energy to excite a high-frequency mechanical mode near 40 kHz without cracking.

The 16 and 17 The hatched representations depict a false-color image representing a 2D measurement in which both torsion bars are actuated simultaneously. 16 and 17 Measurements of the optical field of view as a function of the drive frequencies of both axes for the horizontal ( 16 ) and the vertical ( 17 ) optical field of view of the implemented MEMS mirror device in the case of such 2D operation. These results confirm that the layer stack is even capable of simultaneously driving both axes of the mirror with a relatively high optical field of view of 31°×42° without damage occurring. The representations of the 16 and 17 This demonstrates the high quality of the multilayer structure according to the invention.

In the 18 and 19 This is a case in which a micromirror is subjected to similar stresses as in the 14 , 15 , 16 until 17 exhibits a failure and, in particular, delamination. 18 This shows a light microscopic image in which the lower electrode was damaged during the wire bonding process. 19 Delamination between the _SiO₂ and the adhesion layer is evident. These effects are frequently observed when titanium oxide is used as the adhesion layer. As described above, tantalum exhibits significantly better adhesion.

The observation that tantalum exhibits far better adhesion than titanium oxide is documented in the 20 and 21 to see. 20 This is a light microscope image of a device in which tantalum was used as the material for the adhesion layer. Wire bonding can be easily performed here without damaging the lower electrode stack. As shown in 21 As can be seen, even over large areas there are no signs of delamination at any interface.

In 22 This is a scanning electron microscope cross-sectional image of a multilayer structure with an NTC layer. A silicon wafer was used as the silicon substrate, featuring a 1 µm thick silicon oxide layer on one side, followed by a 675 µm thick silicon layer and a second 1 µm thick silicon oxide layer. As can be seen in the cross-sectional image, only the upper part of the substrate is visible, namely the silicon layer 2a and the upper silicon oxide layer 2b. A 20 nm thick adhesion layer 3 is deposited onto the silicon oxide layer 2b. Its position is roughly indicated by the lighter line in the image. A platinum electrode 4 with a thickness of 200 nm is positioned above this. An electroceramic layer 5 is positioned above the platinum electrode 4. The electroceramic layer 5 consists of an NTC film made of Mn-Co-Ni oxide. The NTC layer has a thickness of 125 nm.

The setup was prepared such that the silicon wafer was first treated with UV light and ozone for 10 minutes. Subsequently, the tantalum and platinum were sequentially deposited onto the silicon wafer by DC magnetron sputtering at room temperature using 200 W. For this, an NTC precursor solution was first prepared. This solution was filtered before deposition. The NTC precursor solution was applied to the substrate and coated by spin coating. A first partial layer of the NTC precursor solution was deposited onto the appropriately prepared bare substrate and then dried and pyrolyzed on a hot plate at 350–450 °C. To achieve the desired thickness, the coating, drying, and pyrolysis processes were repeated five times. The amorphous film was then crystallized in an RTA furnace at 650–770 °C.

As in 22 As can be seen, the NTC layer was free of cracks and defects. Furthermore, the scanning electron microscopy image confirmed a dense NTC thin film and showed no signs of delamination of the NTC layer or the lower electrode.

23 Figure 1 shows a flowchart of a process for producing a PZT thin film on an SOI substrate. The resulting layer can, for example, be used in… 1 shown or those in the 12 and 13 The micromirror shown was used.

The substrate used was an SOI wafer, comprising, from bottom to top, an approximately 1.5 µm thick silicon oxide layer, a 450 µm thick silicon handle layer, a 1 µm thick silicon oxide buried layer, a 150 µm thick silicon device layer, and a 1 µm thick top silicon oxide layer. This top silicon oxide layer was first treated with a UV-ozone cleaner for 10 minutes. After this treatment... In nigung, an adhesion layer of tantalum with a thickness of 20 nm was deposited by DC magnetron sputtering at room temperature with 500 W.

A 200 nm thick platinum layer is deposited onto the tantalum layer, again by DC magnetron sputtering at room temperature and 500 W. The sputtering was performed in an argon working gas atmosphere with an argon pressure between 1 × ^10⁻³ mbar and 8 × ^10⁻² mbar. The distance between the target and substrate was 12 to 18 cm. This process creates a stack comprising the silicon wafer with the tantalum layer and the platinum layer.

A lead titanate seed layer ( _PbTiO₃ ) is then deposited on the platinum electrode. For this purpose, a _PbTiO₃ seed layer solution was first prepared. The solution had a concentration of 0.0625 mol/L _PbTiO₃ and a 10% molar excess of lead to compensate for evaporation during crystallization. Before deposition, the seed layer was filtered through a 0.2 µm PTFE syringe filter. The seed layer solution was then applied to the bare platinum surface and deposited by spin coating at a rotation speed of 2000 revolutions per minute for 30 seconds. The resulting amorphous seed layer was dried and pyrolyzed on a hot plate at 150 °C and subsequently crystallized in a rapid thermal furnace at 520 °C. This process formed a seed layer approximately 10 nm thick. This creates a stack consisting of an SOI substrate, a tantalum adhesive layer, a platinum electrode layer, and a nucleation layer.

The PZT electroceramic layer is then formed by depositing several sublayers, each consisting of three sublayers.

First, a zirconium-rich sublayer is formed. For this purpose, a first zirconium-rich precursor solution is prepared by dissolving lead(II) acetate in a solution of zirconium(IV) propoxide and titanium(IV) isopropoxide in acetic acid and 2-methoxyethanol. After dissolving the lead precursor at 60 °C, the resulting solution was refluxed under a nitrogen atmosphere for 2 hours. After distilling off the byproducts, the mixture was diluted to a concentration of 0.5 mol/L. The composition of the first prepared solution corresponds to the composition of Pb(Zr _0.63 Ti _0.37 ) _O3 for the sublayer to be formed. The solution is prepared to also have a 15% molar excess of lead. Before deposition, the zirconium-rich first precursor solution was filtered through a 0.2 µm PTFE syringe filter. The zirconium-rich first precursor solution was then applied to the nucleation layer and coated for 30 seconds using spin coating at a rotation speed of 2000 revolutions per minute. The resulting zirconium-rich sublayer was dried and pyrolyzed at 150 °C and 350 °C, respectively.

To form a medium-concentrated second sublayer, a medium-concentrated second precursor solution is first prepared by dissolving lead(II) acetate in a solution of zirconium(IV) propoxide and titanium(IV) isopropoxide in acetic acid and 2-methoxyethanol. After dissolving the lead precursor at 60 °C, the resulting solution was refluxed under a nitrogen atmosphere for 2 hours. After distilling off the byproducts, the mixture was diluted to a concentration of 0.5 mol/L. The composition of the solution thus prepared corresponds to the composition of Pb(Zr _0.53 Ti _0.47 ) _O3 for the sublayer to be formed. The solution is prepared to also have a 15% molar excess of lead. Before deposition, the medium-concentrated second precursor solution was filtered through a 0.2 µm PTFE syringe filter. The medium-concentrated second precursor solution was then applied to the dried and pyrolyzed, zirconium-rich sublayer and spin-coated for 30 seconds at a rotational speed of 2000 revolutions per minute. The resulting medium-concentrated second sublayer was dried and pyrolyzed at temperatures of 150 °C and 350 °C, respectively.

To form a titanium-rich third sublayer, a titanium-rich third precursor solution is first prepared by dissolving lead(II) acetate in a solution of zirconium(IV) propoxide and titanium(IV) isopropoxide in acetic acid and 2-methoxyethanol. After dissolving the lead precursor at 60 °C, the resulting solution was refluxed under a nitrogen atmosphere for 2 hours. After distilling off the byproducts, the mixture was diluted to a concentration of 0.5 mol/L. The composition of the solution thus prepared corresponds to the composition of Pb (Zr _0.43 Ti _0.57 ) O ₃ for the sublayer to be formed. The solution is prepared to also have a 15% molar excess of lead. Before deposition, the titanium-rich third precursor solution was filtered through a 0.2 µm PTFE syringe filter. The titanium-rich third precursor solution was then applied to the dried and pyrolyzed second sublayer and rotated at a speed of 2000 revolutions per minute. The third sublayer, rich in titanium, was coated by spin coating for 30 seconds. It was then dried and pyrolyzed at temperatures of 150 °C and 350 °C, respectively.

The partial layer formed so far from the three sublayers is amorphous. It has a thickness of 50 to 200 nm. After the formation of this amorphous partial layer, it undergoes a crystallization step in a rapid thermal heating oven at 650°C.

To obtain a PZT electroceramic layer with a thickness of 1.7 to 2.5 µm, the sublayer formation described above was repeated 24 times. In this example, a thickness of 1.7 µm corresponds to 24 sublayers. This allows for the stacking of an SOI substrate, a tantalum adhesion layer, a platinum electrode layer, a seed layer, and a PZT electroceramic layer. Finally, an upper electrode, which is in 23 Not shown, it can be deposited, for example, by DC magnetron sputtering. The upper electrode can, for example, consist of gold or platinum and/or, in this case, have a partial chromium layer.

The above procedure can be adapted for other materials or other layer thicknesses.

Reference character list

1

Multi-layer structure

2

substrate

3

adhesion layer

3'

second adhesion layer

3a

first adhesion layer

3b

second adhesion layer

3a'

third adhesion layer

4

electrode

4'

second electrode

5

electroceramic layer

5', 5''

second electroceramic layer

6

upper electrode

6', 6''

second upper electrode

7

column

10

micromirrors

11

slow axis

12

fast axis

13

Mirror surface

14

drive ring

Claims (27)

comprising a multilayer structure: a semiconductor or insulator substrate with a surface roughness (Ra) of 2 µm or less, an electrode arranged over the substrate which contains a noble metal or a conductive oxide, and an electroceramic layer which is arranged over or on the electrode, wherein an adhesion layer which comprises a transition metal or a transition metal oxide is arranged between and in direct contact with a major surface of the substrate and the electrode. Multilayer structure according to Claim 1 , wherein the substrate is a silicon wafer-based substrate, a sapphire-based substrate, or a glass substrate. Multilayer structure according to Claim 1 or 2 , wherein the substrate has a surface roughness Ra of 10 nm to 2 µm, preferably of 20 nm to 1 µm, on its main surface. Multilayer structure according to Claim 1 or 2 , wherein the substrate is mirror-polished and has a surface roughness (Ra) of less than 20 nm. Multilayer structure according to one of the Claims 1 until 4 , wherein the adhesion layer has a first adhesion sublayer comprising a transition metal and a second adhesion sublayer comprising a transition metal oxide. Multilayer structure according to one of the Claims 1 until 5 , wherein the transition metal is selected from Ti, Ta or W or their alloys. Multilayer structure according to one of the Claims 1 until 6 , wherein the adhesion layer has a thickness of 1 nm to 100 nm, such as preferably 10 to 50 nm. Multilayer structure according to one of the Claims 1 until 7 , wherein the electrode comprises or consists of Pt or Ir. Multilayer structure according to one of the Claims 1 until 8 , wherein the electrode comprises or consists of an iridium oxide, a rhodium oxide, a rhenium oxide, a ruthenium oxide or a strontium ruthenium oxide. Multilayer structure according to one of the Claims 1 until 9 , wherein the electroceramic layer comprises or consists of a dielectric, piezoelectric, pyroelectric, ferroelectric ceramic material or a thermistor ceramic material. Multilayer structure according to one of the Claims 1 until 10 , wherein the electroceramic layer has crystal grains in the size range of 10 to 1000 nm. Multilayer structure according to one of the Claims 1 until 11 , wherein the electroceramic layer has crystalline columns extending over the entire thickness of the electroceramic layer. Multilayer structure according to one of the Claims 1 until 12 , wherein a second electrode is arranged on a second main surface of the metal substrate, wherein a second adhesion layer is arranged between the second main surface and the second electrode, and wherein a second electroceramic layer is arranged above or on the second electrode. Multilayer structure according to one of the Claims 1 until 13 , wherein a further electrode is arranged on the adhesion layer and a further electroceramic layer is arranged on or above the further electrode. comprising a multilayer structure: a semiconductor or insulator substrate, an electrode arranged above the substrate containing a noble metal or a conductive oxide, and an electroceramic layer arranged above or on the electrode and comprising crystal grains in the size range of 10 to 1000 nm, wherein an adhesion layer comprising a transition metal or a transition metal oxide is arranged between and in direct contact with a major surface of the substrate and the electrode. comprising a multilayer structure: a semiconductor or insulator substrate, an electrode arranged above the substrate containing a noble metal or a conductive oxide, and an electroceramic layer arranged above or on the electrode and comprising crystalline columns extending over the entire thickness of the electroceramic layer, wherein an adhesion layer comprising a transition metal or a transition metal oxide is arranged between and in direct contact with a major surface of the substrate and the electrode. Micromirrors having the multilayer structure according to one of the Claims 1 until 16 . High-energy capacitor having a multilayer structure according to one of the Claims 1 until 16 . Piezoelectric device having the multilayer structure according to one of the Claims 1 until 16 . Electrocaloric solid-state cooling device having a multilayer structure according to one of the Claims 1 until 16 . Ferroelectric storage device having the multilayer structure according to one of the Claims 1 until 16 . Thermistor device comprising the multilayer structure according to one of the Claims 1 until 16 . Pyroelectric device comprising the multilayer structure according to one of the Claims 1 until 16 . Microfluidic pump having the multilayer structure according to one of the Claims 1 until 16 . Method for producing a multilayer structure, wherein an adhesion layer is arranged on a main surface of a semiconductor or insulator substrate with a surface roughness (Ra) of 2 µm or less, an electrode containing a noble metal or a conductive oxide is arranged above the adhesion layer, and an electroceramic material is deposited above the electrode. Procedure according to Claim 25 , wherein the electroceramic layer is a PZT ceramic layer formed, including at least two steps, wherein a first solution with a first Zr/Ti ratio is deposited over the electrode and a first sublayer of the electroceramic layer is formed by drying and/or heating, a second solution with a second Zr/Ti ratio is deposited over the first sublayer of the electroceramic layer, forming a second sublayer, wherein the second Zr/Ti ratio is smaller than the first Zr/Ti ratio. Procedure according to Claim 26 , wherein a third solution with a third Zr/Ti ratio is deposited over the second sublayer of the electroceramic layer, forming a third sublayer, wherein the third Zr/Ti ratio is smaller than the first and the second Zr/Ti ratio.