Substrates for ceramic thin films and thin film devices

Abstract

The present invention relates to a substrate (2) for depositing a thin film (5), the substrate (2) comprising a base layer (3) comprising titanium and an intermediate (4) layer comprising titanium oxide. The substrate (2) is configured so that a thin film ceramic layer (5) can be deposited on the intermediate layer. The present invention also relates to a thin film device (2) comprising the substrate (2) and the ceramic thin film layer (5), and a method of manufacturing the same.

Description

[Technical Field]

[0001] The present invention relates to a substrate for depositing a ceramic thin film, a thin film device including the substrate and the ceramic thin film, and a method for manufacturing the substrate and the thin film device.

[0002] Ceramic thin film devices, which include a metal substrate and a dielectric ceramic thin film layer, are typically fabricated by chemical solution deposition.

[0003] Substitution of ceramic materials with foreign atoms is commonly used to tailor the properties of the ceramic material, such as the dielectric constant or piezoelectric coefficient, and to tailor the ceramic material for different applications.

[0004] Ceramic thin films can be fabricated on metal substrates, but the typical process involves many application steps to achieve the final film thickness, which promotes atomic and ionic interdiffusion between the substrate and the thin film, increasing residual stress.

[0005] Additionally, the multiple coating steps increase costs and overall process time, and can also damage the final laminate.

[0006] Typically, the metal substrate of choice for such devices is stainless steel due to its low cost and availability. An example of the state of the art is disclosed in WO 2021 / 249844. Other metals suitable for the metal substrate are described, for example, in U.S. Patent Application Publication No. 2004 / 0175585 and in JF Ihlefeld et al.: Journal of Materials Research, Volume 20, Issue 10, October 2005, pp. 2838-2844. Suitable ceramic material compositions are described, for example, in WO 2021 / 064036 and WO 2019 / 174719. WO 2022 / 122445 describes ceramic thick films comprising such suitable ceramic material compositions deposited on ceramic substrates.

[0007] In many cases, an intermediate layer such as lanthanum nickel oxide (LNO) is deposited to avoid interdiffusion between the stainless steel substrate and the ceramic thin film.

[0008] However, the LNO layer does not contribute to reducing defects that occur during the crystallization of thin films on stainless steel at high temperatures, such as atomic and ionic interdiffusion and the formation of unwanted mixed oxide layers on the substrate surface.

[0009] In view of the shortcomings of state of the art products and methods, it is an object of the present invention to disclose improved substrates, thin film devices and manufacturing methods.

[0010] In particular, the present invention relates to a substrate, which includes a base layer and an intermediate layer, configured so that a thin-film ceramic layer can be deposited onto the intermediate layer.

[0011] The base layer is a metal layer comprising titanium. According to one embodiment, titanium is the main component of the base layer. The base layer may be made of a composition having 100 atomic percent titanium (Ti). According to one embodiment, the base layer is made of titanium.

[0012] Other possible, but not according to the invention, metal layer materials may comprise or consist of copper, nickel or steel.

[0013] A base layer containing titanium has several advantages.

[0014] Because titanium is electrically conductive, the base layer can function as a base electrode to which the thin film can be electrically contacted.

[0015] Furthermore, the base layer exhibits flexible or elastic mechanical behavior.

[0016] Additionally, titanium may be handled and processed in an air atmosphere without the need to exclude atmospheric oxygen.

[0017] The intermediate layer comprises titanium oxide, which is preferably thermally grown titanium oxide, or alternatively, the titanium oxide is anodically grown titanium oxide.

[0018] Other possible interlayer materials, but not according to the invention, may comprise or consist of copper oxide, nickel oxide or an oxidized steel surface.

[0019] According to one embodiment, titanium oxide (TiO2) is the main component of the intermediate layer. The intermediate layer may consist of a composition having 100 atomic % titanium oxide. Preferably, the intermediate layer consists of titanium oxide.

[0020] The described intermediate layers exhibit a high degree of homogeneity, in particular a homogeneous structure and composition, and therefore homogeneous electrical and mechanical properties, which can be precisely set.

[0021] The oxide layer formed by natural oxidation contains different heteroatoms and is not made of pure titanium oxide.

[0022] In one embodiment, the substrate is configured for the deposition of ceramic thin films.

[0023] In particular, the intermediate layer may be configured such that a thin film ceramic layer can be deposited onto the intermediate layer.

[0024] The intermediate layer has a structure, density and thickness suitable to prevent interdiffusion between the base layer and the thin film.

[0025] Furthermore, the intermediate layer allows for stable and permanent deposition of a thin film onto the substrate.

[0026] The intermediate layer preferably has a structure and a minimum thickness suitable for exhibiting self-healing oxidation properties.

[0027] In particular, the intermediate layer can be made to self-repair by applying an electric field to the substrate to induce the formation of new titanium oxide.

[0028] In one embodiment, the intermediate layer and the base layer are immediately adjacent layers, with no layer deposited between these two layers, and no other structures disposed between the intermediate layer and the base layer.

[0029] The intermediate layer prevents the formation of a mixed oxide layer between the base layer and the thin ceramic layer.

[0030] In one embodiment, the substrate comprises a base layer and an intermediate layer.

[0031] No further functional layers are required: the base layer may function as the base electrode.

[0032] In other embodiments, the substrate may include a separate electrode layer or additional structural or protective layers.

[0033] The electrode layer or layers may consist of a conductive metal, such as gold, chromium, silver, platinum, copper, titanium, combinations thereof, or metal oxides, and may be up to 1 μm thick.

[0034] Examples of metal oxides are nickel lanthanum oxide (LNO), indium tin oxide (ITO), and aluminum zinc oxide (AZO).

[0035] Furthermore, the electrodes may comprise a stack of several stacked metal layers, for example a Cr / Ni / Ag stack or a Cr / Ni / Au stack.

[0036] The electrode layer may be deposited by chemical solution deposition, sputtering, lithography, screen printing, inkjet printing, or another suitable technique.

[0037] In one embodiment, the base layer has a thickness of between 5 μm and 1000 μm. Preferably, the base layer has a thickness of between 5 μm and 200 μm, more preferably between 5 μm and 100 μm. Therefore, the base layer is highly flexible. This reduces the material consumption required to produce the substrate.

[0038] In one embodiment, the base layer has a surface roughness Ra of less than 0.5 μm, preferably less than 0.3 μm, such that the surface of the base layer is suitable for forming a smooth intermediate layer thereon, thereby enabling precise adaptation of the geometric and structural characteristics of the intermediate layer.

[0039] In one embodiment, the intermediate layer has a thickness of 0.1 μm to 2 μm, preferably 0.8 μm to 1 μm.

[0040] The thickness of the intermediate layer is preferably significantly greater than the thickness of the native oxide layer on the titanium-based layer. Intermediate layers having the described thickness exhibit desirable mechanical and electrical properties. In particular, the intermediate layer exhibits self-healing properties.

[0041] Due to the selected thickness, the intermediate layer is highly flexible, reducing the material consumption required to produce the substrate, while being thick enough to prevent interdiffusion between the base layer and the thin ceramic layer.

[0042] The present invention further relates to a thin film device comprising the aforementioned substrate and a thin film ceramic layer.

[0043] By combining the described substrate with a titanium-containing base layer, a titanium oxide-containing intermediate layer, and a ceramic thin film, interdiffusion, particularly atomic and ionic interdiffusion, between the base layer and the thin film can be suppressed during the manufacturing or deposition process of the thin ceramic layer on the substrate. Thus, the substrate and the thin film contain a homogeneous material phase with only a small amount of impurities, or preferably no impurities at all. Therefore, the mechanical and electrical properties of the substrate can be precisely adjusted.

[0044] A thin ceramic layer is applied or deposited onto the intermediate layer.

[0045] In one embodiment, the intermediate layer and the thin ceramic layer are immediately adjacent layers. The intermediate layer is suitable for housing the thin ceramic layer.

[0046] In other embodiments, further functional or structural layers, such as internal electrode layers, may be disposed between the intermediate layer and the thin-film ceramic layer.

[0047] In one embodiment, the thin film device consists of a substrate and a thin film ceramic layer, with no additional layers required.

[0048] In one embodiment, the thin film ceramic layer may include a polycrystalline, oligocrystalline, or single crystalline structure.

[0049] In this embodiment, the device may be used as a dielectric electrode structure for applying an electric field to a selected object. A dielectric electrode may be understood as a device that provides conductive and insulating characteristics. For example, the dielectric electrode may have at least one conductive layer and one insulating layer. In particular, the dielectric electrode preferably includes a substrate that provides electrical conductivity and a high-dielectric-constant material, such as a ceramic material described below, on the substrate.

[0050] In one embodiment, the thin film device includes internal electrode layers for electrical connections.

[0051] In one embodiment, the thin-film device includes several internal electrode layers. In this embodiment, the device may be used as a multilayer electrode capacitor or a multilayer ceramic capacitor. An electric field may be applied to the thin-film layer between two or several internal electrode layers.

[0052] In one embodiment, the device may include several, for example, two or more, thin-film ceramic layers. The thin-film ceramic layers may be disposed between single electrode layers. The ceramic thin-film layers and electrode layers may form a stack.

[0053] The thin film device may be completed by a top electrode, on which no additional ceramic thin film layers are deposited, the top electrode completing the thin film device on the side of the thin film device opposite the side completed by the substrate.

[0054] The top electrode may or may not cover the entire area of ​​the ceramic thin film layer and may exhibit different shapes.

[0055] An electric field may be applied in the stacking direction of the layers, and the stack may thus form a multi-electrode capacitor structure with several capacitor elements connected in series.

[0056] An electric field may also be applied in a direction perpendicular to the stacking direction. The internal electrodes may contact external electrodes on both sides of the stack perpendicular to the stacking direction. In this way, a multilayer ceramic capacitor (MLCC) may be formed.

[0057] In one embodiment, the thin film ceramic layer comprises a ceramic material that is a perovskite ceramic having the general structure ABO3.

[0058] In one embodiment, the thin ceramic layer is made of the ceramic composition Ba(Zr x Ti 1-x )O3, preferably 0.05≦x≦0.6 is satisfied.

[0059] In one embodiment, the thin ceramic layer may be made of a ceramic material.

[0060] Additionally, the ceramic material may include dopants to modify the properties of the ceramic.

[0061] In one embodiment, the ceramic material comprises y% by weight of a rare earth metal dopant, in particular yttrium, preferably with 0.2≦y≦2. The proportion y is determined by the ratio of 100% by weight of Ba(Zr x Ti 1-x )O3.

[0062] In one embodiment, the ceramic material comprises z% by weight of a transition metal dopant, in particular manganese, preferably such that 0.11≦z≦1. The proportion z is 100% by weight of Ba(Zr x Ti 1-x )O3.

[0063] Ceramic materials have good electrical and mechanical properties, especially when used in thin films. Furthermore, the materials are lead-free and therefore environmentally friendly.

[0064] In an alternative embodiment, Pb has a preferred x value of 0.4 to 0.6 (0.4≦x≦0.6), which also has good electrical and mechanical properties when used in thin films. x Zr 1-x )TiO3, or Pb(Mn x Nb 1-x A lead-containing ceramic material such as )O3+PbTiO3 is selected.

[0065] In one embodiment, the thin film device is configured as a circular plate.

[0066] A circular shape offers advantages in manufacturing, handling and application, for example with regard to mechanical stability.

[0067] In one embodiment, the thin film device is configured as a three-dimensionally folded foil.

[0068] The folded foil may be adapted to the shape of different applications in a flexible manner, in particular the foil may be elastic and suitable to be folded into various shapes and then refolded back to the original shape.

[0069] In particular, the foil may include several cuts or perforations according to the Japanese kirigami technique to achieve the desired flexible properties for folding.

[0070] In one embodiment, the ceramic thin film has a thickness of 0.3 μm to 5 μm, preferably 0.3 μm to 1.5 μm.

[0071] These dimensions are sufficient to achieve the desired mechanical properties, thereby reducing the consumption of ceramic material. The thin film layer preferably has homogeneous mechanical and electrical properties.

[0072] In accordance with the present invention, the thin film devices described above may be used as dielectric electrode structures, or as capacitor structures, or as multilayer capacitor structures as detailed above.

[0073] Furthermore, the present invention relates to dielectric electrode structures, capacitor structures, multilayer capacitor structures, particularly multilayer electrode capacitor structures or multilayer ceramic capacitor (MLCC) structures, including the thin film devices detailed above.

[0074] Furthermore, the present invention relates to a thin film device or medical device, particularly for medical, diagnostic or therapeutic treatment, such as electrical cancer treatment, comprising a dielectric electrode structure.

[0075] Furthermore, the invention relates to a method for preparing a substrate for the deposition of thin films, comprising several steps.

[0076] The substrate and the ceramic thin film may be constructed as described above. In particular, the substrate and the ceramic thin film may be manufactured by the following method.

[0077] In the first step, a titanium foil is prepared to form a base layer.

[0078] In another step, the base layer is heat treated or anodized to form an intermediate layer immediately adjacent the base layer, the intermediate layer comprising or consisting of titanium oxide.

[0079] By forming a titanium oxide layer directly on the base layer, the formation of a natural mixed metal oxide layer is prevented.

[0080] In one embodiment, the base layer is heated during the heat treatment to a first holding temperature, preferably 550°C to 620°C, in a first step and to a second holding temperature, preferably 640°C to 700°C, in a second step.

[0081] The described stepwise thermal process can produce a dense intermediate layer without open porosity, which can be understood such that the membrane produced accordingly can be dense, or the membrane can have no open porosity.

[0082] The described heat treatment results in an intermediate layer having the desired properties.

[0083] Furthermore, the present invention relates to a method for manufacturing a thin film device comprising a substrate for the deposition of a thin film, the method may comprise the steps mentioned above. Furthermore, the method may comprise several additional steps.

[0084] In one step, a ceramic material for the ceramic thin film layer is prepared in a tacky state, which may be a viscous paste containing organic substances and / or solvents.

[0085] In another step, a ceramic material is adhesively applied to a surface of the intermediate layer facing away from the base layer to form a thin film ceramic layer.

[0086] After deposition, the deposited thin ceramic layer is preferably dried on a hot plate. Preferably, the drying of the ceramic thin film is carried out at a temperature of 150° C. to 250° C. In this step, residual solvent may be removed.

[0087] After drying, the dried thin ceramic layer is fired or pyrolyzed. Preferably, firing of the thin film is carried out in two steps at a temperature between 300°C and 600°C, preferably in a furnace. The first firing step may be carried out at a temperature between 300°C and 400°C. The second firing step may be carried out at a temperature between 500°C and 600°C. In this step, residual organic materials may be removed.

[0088] In a separate step, the fired thin ceramic layer is crystallized, preferably in a furnace, at a temperature of preferably 600°C to 700°C.

[0089] In one embodiment, the deposition of the ceramic material is by slot die coating.

[0090] By slot die coating, ceramic thin film layers may be deposited in desired thicknesses and configurations.

[0091] Alternative methods for depositing thin film layers are spin or dip coating, spray pyrolysis, and inkjet printing. Alternatively, thin film layers can be deposited by physical methods such as sputtering, physical vapor deposition (PLD), or aerosol deposition. In this case, solid ceramic targets and / or ceramic powders having the desired composition are used.

[0092] In one embodiment, the ceramic material is deposited by stacking several sublayers, each having a thickness of 0.1 μm to 0.5 μm. Preferably, each sublayer has a thickness of 0.2 μm to 0.3 μm. The required thickness of the sublayers is achieved by selecting a suitable viscous ceramic material, for example, a suitable ceramic paste having a suitable composition. Preferably, the ceramic paste includes an organic polymer material.

[0093] By applying sublayers having the thicknesses described, the entire ceramic thin film layer can be formed by applying only a few sublayers, preferably 1 to 5 sublayers.

[0094] The entire process of deposition, drying, firing / pyrolysis and crystallization may be carried out 1 to 5 times until the final thickness of the ceramic thin film layer is reached.

[0095] By reducing the number of sublayers, a more uniform structure of the ceramic thin film layer can be obtained, which reduces the susceptibility to defects or damage during manufacturing.

[0096] In one embodiment, the step of providing the ceramic material in a tacky state comprises several steps, preferably comprising a chemical solution deposition procedure.

[0097] In one step, a first solution is prepared by dissolving a barium salt, such as barium acetate, in glacial acetic acid, water, and ethanolamine.

[0098] Optionally, an yttrium salt, such as yttrium acetate, and a manganese salt, such as manganese acetate, can be dissolved in the first solution to provide a doped ceramic material.

[0099] In another step, a second solution is prepared by dissolving an organic polymer in a suitable solvent, such as ethanol and acetic acid. The organic polymer may be polyvinylpyrrolidone (PVP).

[0100] In a separate step, titanium tetraethoxide and zirconium propoxide are dissolved in a second solution, which may be stirred at the same time.

[0101] The first and second solutions are then mixed, preferably with stirring, to form a sol-gel.

[0102] In a preferred embodiment, a first solution is prepared by dissolving stoichiometric amounts of barium acetate, and optionally yttrium acetate and manganese acetate, in 5-15 moles of glacial acetic acid, 2-8 moles of water, and ethanolamine. A second solution is prepared by dissolving 0.1-0.8 moles of polyvinylpyrrolidone in 3-10 moles of ethanol and 15-30 moles of acetic acid. Titanium tetraethoxide and zirconium propoxide are added stoichiometrically to the second solution with stirring. The first solution is then added to the second solution. Both solutions are mixed together by stirring.

[0103] Preferably, the resulting solution has a viscosity of 10 to 100 cP (1 cP = 10 -3A ceramic paste having a viscosity of 1000 psi (1000 psi) is formed.

[0104] In one embodiment, the geometry of the thin film device is configured by cutting, for example mechanical or laser cutting, or punching.

[0105] In one embodiment, the thin film device is three-dimensionally shaped by cutting or punching the thin film device and folding it. In particular, the thin film device may be three-dimensionally shaped by using kirigami techniques, which are a combination of cutting and origami folding techniques. The cut or punched portions may make the thin film device more flexible. The thin film device may be adapted to the contours of various objects to which the device is applied.

[0106] The applied kirigami technique allows the flat device structure to become a three-dimensional structure upon application of force, and then return to the original flat structure upon removal of the force without leaving the device deformed.

[0107] Kirigami cutting devices are superior to other ceramic thin film devices due to their ability to conform to and optimize contact with moving or expanding elements, especially when the contact area is larger. Illustratively, the elements are moving mechanical elements or human or animal bodies.

[0108] Various design motifs can be cut or punched into the device.

[0109] The invention will now be described in more detail with reference to the accompanying drawings. [Brief explanation of the drawings]

[0110] [Figure 1] FIG. 1 is a cross-sectional view of a first embodiment of a thin-film device. [Figure 2] 1 is a diagram showing an SEM (scanning electron microscope) photograph of a cross section of a thin film device according to a first embodiment. [Figure 3]FIG. 2 is a cross-sectional view of a second embodiment of a thin-film device. [Figure 4] FIG. 10 is a cross-sectional view of a third embodiment of a thin-film device. [Figure 5] FIG. 10 is a cross-sectional view showing a fourth embodiment of the thin-film device. [Figure 6] FIG. 1 shows a process scheme of key manufacturing steps. [Figure 7] 1A and 1B show possible circular shapes for the completed thin film device. [Figure 8] 1A-1C illustrate possible three-dimensional folded shapes of the completed thin film device. [Figure 9] 1 shows two SEM photographs: on the right, a cross section of a first embodiment of a thin film device is shown, and on the left, a cross section through a thin film device fabricated by a different method is shown for comparison. [Figure 10] 10 is a graph showing the dependence of power loss on electrical frequency for two different thin-film devices shown in FIG. 9. [Figure 11] 4 is a graph showing the dependence of capacitance density and power loss on electrical frequency for a first embodiment of a thin-film device. [Figure 12] 1 is a graph showing the temperature dependence of capacitance and power loss for a first embodiment of a thin-film device, the temperature range being chosen to be around body temperature (37° C.); [Figure 13] 10 is a graph showing the temperature dependence of capacitance and power loss of ceramic devices fabricated by different methods, shown for comparison on the left side of Figure 9. Again, a temperature range around body temperature (37°C) is chosen. [Figure 14] 1 is a graph showing the breakdown strength of a first embodiment of a thin-film device, where the dependence of the current on the electric field is measured. The breakdown point is about 33 kV / mm.

[0111] Similar or apparently identical elements in the figures are given the same reference numerals. The figures and proportions in the figures are not to scale.

[0112] 1 shows an embodiment of a thin film device 1. The thin film device 1 comprises a substrate 2 including a base layer 3 and an intermediate layer 4, and further comprises a ceramic thin film layer 5.

[0113] The mentioned layers are stacked in a stack to form the multilayer device 1.

[0114] The base layer 3 comprises titanium metal. Preferably, the layer 3 consists of titanium (Ti).

[0115] The base layer 3 may be made of Ti foil. The thickness of the Ti foil may be 5 μm to 1000 μm, preferably 5 μm to 100 μm.

[0116] An intermediate layer 4 is disposed directly on the surface of the base layer 3. No further layers or structures are disposed between the base layer 3 and the intermediate layer 4.

[0117] The intermediate layer 4 comprises or preferably consists of titanium oxide TiO2, which preferably has a rutile structure.

[0118] The thickness of the intermediate layer may be 0.1 μm to 2 μm, preferably 0.8 μm to 1 μm.

[0119] The substrate 2 can function as an electrode in contact with the ceramic thin film, or in other embodiments, a separate electrode layer may be provided configured as a bottom electrode between the substrate 2 and the ceramic thin film layer 5, or as a top electrode with the ceramic thin film layer 5 sandwiched between the substrate and the top electrode.

[0120] A ceramic thin film layer 5 is deposited on the surface of the intermediate layer 4 opposite the surface in contact with the base layer 3 .

[0121] The ceramic thin film may have a thickness of 0.3 μm to 5 μm, preferably 1.5 μm to 5 μm.

[0122] In the illustrated embodiment, the ceramic thin film layer 5 is directly adjacent to the intermediate layer 4. No further layers or structures are disposed therebetween.

[0123] The ceramic thin film layer 5 has the composition Ba(Zr x Ti 1-x )O3, preferably 0.05≦x≦0.6 is satisfied.

[0124] Table 1 shows the results of EDX (energy dispersive X-ray spectroscopy) measurements of the compositions of the base layer, intermediate layer, and ceramic thin film of an exemplary ceramic thin film device, with the proportions of different elements listed in atomic %.

[0125] [Table 1]

[0126] Furthermore, the ceramic material preferably comprises a dopant for modifying the properties of the ceramic. In particular, the ceramic material comprises, for example, y% by weight of a rare earth metal dopant, in particular yttrium, where 0.2≦y≦2 is satisfied. The proportion y is 100% by weight of Ba(Zr x Ti 1-x )O3. Furthermore, the ceramic material contains, for example, z% by weight of a transition metal dopant, in particular manganese, where 0.11≦z≦1. The proportion z is the sum of 100% by weight of Ba(Zr x Ti 1-x )O3.

[0127] Figure 2 shows an SEM photograph of a cross section through the thin film device 1 according to the first embodiment. Shown are the base layer 3, the intermediate layer 4 and the ceramic thin film layer 5. The shown surface of the base layer 3 has a preferably low surface roughness Ra of less than 0.3 µm.

[0128] FIG. 3 shows another embodiment of the device 1.

[0129] Unlike the first embodiment, the second embodiment of device 1 includes several additional layers.

[0130] Between the intermediate layer 4 and the thin film layer 5, a metal internal electrode layer 6 is arranged for electrical contact.

[0131] On the opposite surface of the thin film layer 5 a second electrode 7 is deposited.

[0132] The second embodiment of the thin film device 1 may be used as an electrical capacitor, while the first embodiment may be used as a dielectric electrode structure for applying an electric field to a selected object, in particular the human body, for example for medical, diagnostic or therapeutic applications.

[0133] Due to its electrical properties, the thin film device 1 may be suitable for use at generally body temperature.

[0134] Figure 4 shows a device 1 configured as a multi-layer electrode capacitor. The capacitor device 1 is constructed by stacking several ceramic thin film layers 5 and electrode layers 7, thus forming a series of single capacitor elements.

[0135] 5 shows a device 1 configured as a multilayer ceramic capacitor (MLCC). The capacitor device 1 includes several ceramic thin film layers 5 and electrode layers 7, which alternately contact two different external electrodes on opposite sides of the device 1.

[0136] FIG. 6 diagrammatically summarizes selected steps of the manufacturing process of a first embodiment of the thin film device 1.

[0137] The first solution is prepared by dissolving barium acetate, yttrium acetate, and manganese acetate in glacial acetic acid, water, and ethanolamine. In the second solution, polyvinylpyrrolidone is dissolved in ethanol and acetic acid. Titanium tetraethoxide and zirconium propoxide are added to the second solution with stirring. The first and second solutions are mixed to form a sol-gel.

[0138] Further, in the diagrammatically shown step S1, a titanium foil for the substrate 2 is prepared and heat-treated in a furnace in an air atmosphere by heating it to a temperature of 550°C-620°C in a first step, and then to a temperature of 640°C-700°C in a second step. Through the described heat treatment process, an intermediate layer 4 is formed on the surface of the titanium-based layer 3.

[0139] In step S2, a pre-prepared sol-gel is deposited onto the substrate 2 to a thickness of up to 0.05 mm, for example via spin coating, dip coating, or slot die coating. In step S3, the thin film 5 is dried, for example on a hot plate at a temperature of 150°C to 250°C. Then, in step S4, the ceramic thin film layer is pyrolyzed twice by heating the device 1 in an oven in air at a temperature of 300°C to 400°C, and then at a temperature of 500°C to 600°C.

[0140] Furthermore, the ceramic thin film layer 5 is crystallized in a furnace at 600°C to 700°C in an air atmosphere.

[0141] The process of deposition, drying, firing / pyrolysis and crystallization is carried out 3-5 times until the final thickness of the ceramic thin film layer 5 is reached in step S5.

[0142] The desired geometric shape can then be punched or cut from the prepared layer structure to obtain the desired shape of device 1 .

[0143] FIG. 7 shows an exemplary circular punchout shape for a completed thin film device with a through hole in the center.

[0144] The circular element may have a diameter of 10 mm to 25 mm and may have concentric through holes with a diameter of 3 mm to 4 mm.

[0145] In general, the ceramic thin film layer 5 may cover the entire surface of the substrate 2, or only a defined area. For example, portions of the substrate near the edges of the substrate may remain uncovered, as shown, for example, in FIG.

[0146] Figure 8 shows another embodiment of device 1, which is an alternative to that of Figure 7. Device 1 is manufactured using the kirigami technique.

[0147] The embodiment of Figure 8 is just one example of a kirigami pattern: further different patterns can be created by cutting or punching different motifs into a given multi-layer structure.

[0148] Figure 9 again shows, on the right, an SEM photograph of a cross section through a first embodiment of the thin film device 1 according to the invention. Additionally, for comparison, Figure 9 shows, on the left, an SEM photograph of another thin film layer device manufactured by a different method than that described above.

[0149] The device on the left, which is not part of this invention, includes a stainless steel substrate 8 on which an unwanted mixed metal oxide layer 9 is formed. There are no smooth surfaces between the monolayers. An intermediate layer 10 between the metal oxide layer and the ceramic thin film layer 11 is made of lanthanum nickelate (nickel lanthanum oxide, LNO). The ceramic thin film layer contains barium zirconium titanate ceramic and unwanted metal impurities resulting from interdiffusion between the metal and metal oxide layers and the ceramic thin film.

[0150] Impurities have a significant and undesirable effect on the mechanical properties, and especially the electrical properties, of the ceramic thin film 5 .

[0151] Table 2 shows the EDX measurements of the composition of the base layer, intermediate layer and ceramic thin film of a device not according to the invention. The above-mentioned impurities due to interdiffusion effects can be recognized. The proportions of the different elements are given in atomic %.

[0152] [Table 2]

[0153] FIG. 10 shows the power loss at different applied electrical frequencies in a comparison of a first embodiment of the device 1 according to the invention (solid line) with a non-inventive embodiment of the thin film device (dashed line).

[0154] Electrical losses are stated in tan(delta). Frequency is stated in Hertz (Hz). Measurements were made at room temperature.

[0155] 10, it can be clearly observed that the electrical losses are smaller and less frequency dependent in the embodiment of the present invention. In particular, the losses can be significantly reduced with increasing frequency.

[0156] FIG. 11 shows the nF / cm 2 The unit capacitance density (solid line) and again the electrical losses (dashed line) are shown. As can be observed from Figure 11, the capacitance density and electrical losses are independent or almost independent of the applied electrical frequency.

[0157] The measurements were again carried out at room temperature.

[0158] 12 shows the temperature dependence of the capacitance and electrical loss of the first embodiment of the thin-film device 1. In the temperature range of 19.5°C to 42°C, both values ​​experience a variation of less than 10%. Therefore, the thin-film device 1 is suitable for application at body temperature, for example, on the human body.

[0159] In particular, the thin film device 1 may be used as a dielectric electrode structure for applying an electric field to the human body for cancer treatment with tumor treating electric fields.

[0160] For comparison, Figure 13 shows the temperature dependence of capacitance and electrical loss for a non-inventive embodiment of the device: in the temperature range 19.5°C to 42°C, both values ​​experience large fluctuations.

[0161] As a result, the device 1 of the present invention exhibits a lower temperature dependence of the capacitance and electrical losses.

[0162] Additionally, thin film devices have a desirably high dielectric breakdown strength.

[0163] Figure 14 shows the breakdown strength of the first embodiment of the thin film device. The dependence of the current on the electric field is measured. The breakdown point is about 33 kV / mm. [Explanation of symbols]

[0164] 1 Thin-film devices 2 boards 3 Base Layer 4. Middle class 5 Ceramic thin film layer 6, 7 Electrode layer 8. Stainless steel substrate 9 Mixed metal oxide layer 10 LNO layers 11 Ceramic thin film layer containing impurities

Claims

1. A substrate (2) comprising a base layer (3) comprising titanium and an intermediate (4) layer comprising titanium oxide.

2. 2. The substrate (2) of claim 1, which is a substrate for the deposition of a thin ceramic layer (5), configured so that said thin ceramic layer (5) can be deposited on an intermediate layer.

3. 3. The substrate (2) according to claim 1 or 2, wherein the intermediate layer (4) and the base layer (3) are directly adjacent layers.

4. The substrate (2) according to any one of claims 1 to 3, wherein the substrate (2) consists of the base layer (3) and the intermediate layer (4).

5. The substrate (2) according to any one of claims 1 to 4, wherein the base layer (3) has a thickness of 5 μm to 1000 μm, preferably 5 μm to 100 μm.

6. The substrate (2) according to any one of the preceding claims, wherein the base layer (3) has a surface roughness Ra of less than 0.3 μm.

7. The substrate (2) according to any one of the preceding claims, wherein said intermediate layer (4) has a thickness of between 0.1 μm and 2 μm, preferably between 0.8 μm and 1 μm.

8. The substrate (2) according to any one of claims 1 to 7, wherein the base layer (3) consists of titanium and the intermediate layer (4) consists of titanium oxide.

9. The substrate (2) according to any one of the preceding claims, wherein the intermediate layer has a thickness greater than the thickness of the native oxide layer on the titanium.

10. The substrate (2) according to any one of the preceding claims, wherein the intermediate layer (4) exhibits self-healing properties.

11. 10. The substrate (2) according to claim 9, wherein the intermediate layer (4) has a structure and a minimum layer thickness suitable for exhibiting self-healing oxidation properties.

12. The substrate (2) according to any one of claims 1 to 11, wherein the intermediate layer (4) does not have open porosity.

13. A thin film device (1) comprising a substrate (2) according to any one of claims 1 to 12 and the thin film ceramic layer (5) arranged on the intermediate layer.

14. 14. The thin film device (1) according to claim 13, wherein the intermediate layer (4) and the thin film ceramic layer (5) are directly adjacent layers.

15. 15. A thin film device (1) according to claim 13 or 14, consisting of said substrate (2) and said thin film ceramic layer (5).

16. Thin film device (1) according to claim 13 or 14, comprising just one internal electrode (6, 7) layer or several internal electrode layers (6, 7).

17. Thin film device (1) according to claim 16, comprising several thin film ceramic layers (5).

18. The ceramic thin film ceramic layer (5) has a composition Ba(Zr ｘ Ti １－ｘ ) O ３ wherein 0.05≦x≦0.6 is satisfied, or a ceramic material (Pb ｘ Zr １－ｘ ) TiO ３ (wherein 0.4≦x≦0.6 is satisfied), or the ceramic material Pb(Mn ｘ Nb １－ｘ ) O ３ + PbTiO ３ 18. A thin film device (1) according to any one of claims 13 to 17, comprising: (wherein 0.2≦x≦0.4 is satisfied).

19. 19. The thin-film device (1) according to claim 18, wherein the ceramic material further comprises y% by weight of a rare earth metal dopant, in particular yttrium, and z% by weight of a transition metal dopant, in particular manganese, where 0.2≦y≦2 and 0.1≦z≦1 are satisfied.

20. Thin film device (1) according to any one of claims 13 to 19, configured as a circular plate.

21. Thin film device (1) according to any one of claims 13 to 19, configured as a three-dimensionally folded foil.

22. Thin film device (1) according to any one of claims 13 to 21, wherein the ceramic thin film layer (5) has a thickness of 0.3 μm to 5 μm, preferably 0.3 μm to 1.5 μm.

23. A dielectric electrode structure comprising a thin film device (1) according to any one of claims 13 to 22.

24. A capacitor structure comprising a thin film device (1) according to any one of claims 13 to 22.

25. A multilayer ceramic capacitor structure comprising a thin film device (1) according to any one of claims 13 to 22.

26. A medical device for medical, diagnostic or therapeutic procedures comprising a thin film device (1) according to any one of claims 13 to 22 or a dielectric electrode structure according to claim 23.

27. A method for producing a substrate (2) for the deposition of a ceramic thin film (5), comprising the steps of: providing a titanium foil to form a base layer (3); heat treating or anodizing the base layer (3) to form an intermediate layer (4) directly adjacent to the base layer (3) comprising titanium oxide; A method comprising:

28. 28. The method according to claim 27, wherein during the heat treatment, the base layer (3) is heated in a first step to a first holding temperature and in a second step to a second holding temperature higher than the first holding temperature.

29. 29. The method of claim 28, wherein during the heat treatment of the base layer (3), the first holding temperature is between 550°C and 620°C and the second holding temperature is between 640°C and 700°C.

30. A method according to any one of claims 27 to 29, wherein the intermediate layer is self-repaired by applying an electric field to the substrate to induce the formation of new titanium oxide.

31. A method for manufacturing a thin film device (1), comprising: For manufacturing a substrate (2) according to any one of claims 27 to 30, the steps include: preparing a ceramic material for the ceramic thin film layer (5) in a tacky state; depositing the ceramic material in the tacky state on a surface of the intermediate layer (4) facing away from the base layer (3) to form a thin ceramic layer (5); drying the deposited thin ceramic layer (5); firing the dried thin ceramic layer (5); Crystallizing the fired thin-film ceramic layer (5); The method further comprises:

32. providing the ceramic material in the viscous state, Dissolving a barium salt in a first solution; Dissolving an organic polymer in a second solution; dissolving titanium tetraethoxide and zirconium propoxide in the second solution; mixing the first solution and the second solution to form a sol-gel; 32. The method of claim 31 , comprising:

33. 33. The method of claim 32, wherein the organic polymer of the second solution is polyvinylpyrrolidone.

34. A method according to any one of claims 31 to 33, wherein the deposition of the ceramic material is carried out by slot die coating.

35. 35. The method of claim 34, wherein the ceramic material is deposited by stacking several sub-layers, each sub-layer having a thickness of 0.1 μm to 0.5 μm, preferably 0.2 μm to 0.3 μm.

36. 36. The method according to any one of claims 31 to 35, wherein the drying of the ceramic thin film layer (5) is carried out at a temperature of 150°C to 250°C, the firing of the thin film layer (5) is carried out in two steps at a temperature of 300°C to 600°C, and the crystallization of the thin film layer (5) is carried out at a temperature of 600°C to 700°C.

37. The method according to any one of claims 31 to 36, wherein the geometric shape of the thin film device (1) is configured by cutting or punching.

38. A method according to any one of claims 31 to 37, wherein the thin film device (1) is three-dimensionally shaped by cutting and folding the thin film device, in particular by using the kirigami technique.

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