Method for forming substrate comprising titanium layer or foil coverted with titanium oxide layer coverted with high-k ceramic, electrode, capacitor,

Abstract

The invention relates to a substrate (2) for depositing a film (5), comprising a base layer (3) based on a titanium foil and an intermediate layer (4) based on titanium oxide. The titanium oxide layer is constructed on the titanium foil. Further, a thin film ceramic layer (5) (high-k dielectric barium titanate (BZT)) may be deposited on the intermediate layer (4). The invention further relates to a thin-film device (2) comprising the substrate (2) and a ceramic thin-film layer (5), and to a production method. Furthermore, an electrode, a capacitor, a multilayer capacitor and a medical device comprising the base layer (3), the intermediate layer (4) and the ceramic layer are disclosed.

Description

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

[0002] Ceramic film elements comprising a metallic substrate and a dielectric ceramic film layer are typically manufactured via chemical solution deposition.

[0003] Substituting foreign atoms into ceramic materials is commonly used to adjust the properties of ceramic materials, such as the dielectric constant or piezoelectric coefficient, to adapt the ceramic materials to the application.

[0004] A ceramic film can be manufactured on a metallic substrate, but the usual processing involves many application steps to achieve the final film thickness. This processing facilitates atomic and ionic interdiffusion between the substrate and the film and increases residual stress.

[0005] In addition, the presence of many coating steps increases the cost and the total processing time and also damages the final stack.

[0006] Generally, due to the low cost and high availability, the selected metallic substrate for such devices is stainless steel. Prior art examples are disclosed in WO 2021 / 249844 A1. Other metals suitable for metallic substrates are described, for example, in US2004 / 0175585 A1 and the non-patent literature J.F. Ihlefeld et al.: Journal of Materials Research, Vol. 20, No. 10, October 2005, pp. 2838-2844. Suitable ceramic material compositions are described, for example, in WO 2021 / 064036A1 and WO 2019 / 174719 A1. Ceramic thick films comprising such suitable ceramic material compositions deposited on ceramic substrates are described in WO 2022 / 122445 A2.

[0007] Generally, in order to avoid interdiffusion between the stainless steel substrate and the ceramic film, an intermediate layer, such as lanthanum nickelate (LNO), is deposited.

[0008] However, the LNO layer does not help reduce defects that occur when crystallizing the film on stainless steel at high temperatures, such as atomic and ionic interdiffusion and the formation of an unwanted mixed oxide layer on the substrate surface.

[0009] In view of the disadvantages of the prior art products and methods, an object of the present invention is to disclose an improved substrate, film device, and manufacturing method.

[0010] In particular, the present invention relates to a substrate.

[0011] The substrate comprises a base layer and an intermediate layer. The substrate is adapted such that a thin film ceramic layer can be deposited on the intermediate layer.

[0012] The base layer is a metal layer containing titanium. According to one embodiment, titanium is the main component of the base layer. The base layer may consist of a composition having 100 atomic % titanium (Ti). According to one embodiment, the base layer consists of titanium.

[0013] Other possible but non-inventive materials for the metal layer may include or consist of copper, nickel, or steel.

[0014] The base layer containing titanium has several advantages.

[0015] Since titanium is conductive, the base layer can be used as a base electrode through which the thin film can be electrically contacted.

[0016] In addition, the base layer exhibits flexible or elastic mechanical behavior.

[0017] Furthermore, titanium can be processed and treated in an air atmosphere. It is not necessary to exclude air oxygen.

[0018] The intermediate layer contains titanium oxide. The titanium oxide is preferably thermally grown titanium oxide. Alternatively, the titanium oxide is anodically grown titanium oxide.

[0019] Other possible but non-inventive materials for the intermediate layer may include or consist of copper oxide, nickel oxide, or steel oxide on the surface.

[0020] 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.

[0021] The intermediate layer exhibits high uniformity, particularly a uniform structure and composition, and thus exhibits uniform electrical and mechanical properties. The electrical and mechanical properties can be precisely set.

[0022] An oxide layer formed by natural oxidation will contain different foreign atoms and will not consist of pure titanium oxide.

[0023] In one embodiment, the substrate is configured for depositing a ceramic thin film.

[0024] In particular, the intermediate layer can be adapted such that a thin film ceramic layer can be deposited on the intermediate layer.

[0025] The intermediate layer has an appropriate structure, density, and thickness to prevent interdiffusion between the base layer and the thin film.

[0026] In addition, the intermediate layer allows the thin film to be stably and permanently deposited on the substrate.

[0027] The intermediate layer preferably has a suitable structure and a minimum layer thickness to exhibit self-healing oxidation properties.

[0028] In particular, the intermediate layer can be self-repaired by inducing the formation of new titanium oxide by applying an electric field to the substrate.

[0029] In one embodiment, the intermediate layer and the base layer are directly adjacent layers. There is no deposition layer between these two layers. In addition, no other structures are arranged between the intermediate layer and the base layer.

[0030] The intermediate layer prevents the formation of a mixed oxide layer between the base layer and the thin film ceramic layer.

[0031] In one embodiment, the substrate consists of a base layer and an intermediate layer.

[0032] No other functional layers are required. The base layer can be used as a base electrode.

[0033] In other embodiments, the substrate can include a separate electrode layer or additional structural layers or protective layers.

[0034] The electrode layer or electrode layers can be composed of a conductive metal, such as gold, chromium, silver, platinum, copper, titanium, or a combination thereof, or a metal oxide with a thickness of up to 1 μm.

[0035] Examples of metal oxides are lanthanum nickel oxide (LNO), indium tin oxide (ITO), and aluminum zinc oxide (AZO).

[0036] In addition, the electrode can include a stack of several stacked metal layers, such as a Cr / Ni / Ag stack or a Cr / Ni / Au stack.

[0037] The electrode layer can be deposited by chemical solution deposition, sputtering, lithography, screen printing, inkjet printing, or other suitable techniques.

[0038] In one embodiment, the base layer has a thickness between 5 μm and 1000 μm. Preferably, the base layer has a thickness between 5 μm and 200 μm, more preferably between 5 μm and 100 μm. Therefore, the base layer is highly flexible. The material consumption for producing the substrate can be reduced.

[0039] In one embodiment, the base layer has a surface roughness Ra of less than 0.5 μm, preferably less than 0.3 μm. Therefore, the surface of the base layer is suitable for forming a smooth intermediate layer thereon. Therefore, the geometric and structural properties of the intermediate layer can be precisely adjusted.

[0040] In one embodiment, the intermediate layer has a thickness between 0.1 μm and 2 μm, preferably between 0.8 μm and 1 μm.

[0041] The thickness of the intermediate layer is preferably significantly higher than the thickness of the natural oxide layer on the titanium base layer. The intermediate layer having such thickness exhibits desired mechanical and electrical properties. In particular, the intermediate layer exhibits self-healing properties.

[0042] Due to the selected thickness, the intermediate layer is highly flexible. The material consumption for producing the substrate can be reduced. On the other hand, the intermediate layer has sufficient thickness to prevent interdiffusion between the base layer and the thin film ceramic layer.

[0043] Furthermore, the present invention relates to a thin film device comprising a substrate and a thin film ceramic layer as described above.

[0044] By combining the substrate having a base layer containing titanium and an intermediate layer containing titanium oxide and a ceramic thin film, interdiffusion between the base layer and the thin film during the manufacturing process or deposition process of the thin film ceramic layer on the substrate can be suppressed, especially atomic and ionic interdiffusion. Therefore, the substrate and the thin film contain uniform material phases with only a small amount of impurities or preferably no impurities. Thus, the mechanical and electrical properties of the substrate can be precisely adjusted.

[0045] The thin film ceramic layer is applied or deposited on the intermediate layer.

[0046] In one embodiment, the intermediate layer and the thin film ceramic layer are directly adjacent layers. The intermediate layer is adapted to accommodate the thin film ceramic layer.

[0047] In other embodiments, other functional layers or structural layers, such as an inner electrode layer, may be arranged between the intermediate layer and the thin film ceramic layer.

[0048] In one embodiment, the thin film device consists of a substrate and a thin film ceramic layer. No additional layer is required.

[0049] In one embodiment, the thin film ceramic layer may comprise a polycrystalline, oligo-crystalline or single crystal structure.

[0050] In this embodiment, the device can be used as a dielectric electrode structure to apply an electric field to a selected object. A dielectric electrode can be understood as an arrangement providing conductive and insulating characteristics. For example, a dielectric electrode may have at least one conductive layer and an insulating layer. In particular, preferably, the dielectric electrode comprises a substrate providing conductivity and a high dielectric constant material on top of the substrate, such as the ceramic material described below.

[0051] In one embodiment, the thin film device comprises an inner electrode layer for electrical connection.

[0052] In one embodiment, the thin film device comprises a plurality of inner electrode layers. In this embodiment, the device can be used as a multi-layer electrode capacitor or a multi-layer ceramic capacitor. An electric field can be applied to the thin film layer between two or several inner electrode layers.

[0053] In one embodiment, the device can comprise several (e.g., two or more) thin film ceramic layers. The thin film ceramic layers can be arranged between individual electrode layers. The ceramic thin film layers and the electrode layers can form a stack.

[0054] The thin film device can be completed by a top electrode. No additional ceramic thin film layer is stacked on the top electrode. The top electrode completes the thin film device on the side of the thin film device opposite to the side completed by the substrate.

[0055] The top electrode can cover or can not cover the entire area of the ceramic thin film layer and can exhibit different shapes.

[0056] The electric field can be applied in the stacking direction of the layers. Thus, the stack can form a multi-layer electrode capacitor structure in which several capacitor elements are connected in series.

[0057] The electric field can also be applied in a direction perpendicular to the stacking direction. The inner electrodes can contact the outer electrodes on both sides of the stack perpendicular to the stacking direction. In this way, a multi-layer ceramic capacitor (MLCC) can be formed.

[0058] In one embodiment, the thin film ceramic layer comprises a ceramic material which is a perovskite ceramic having a general formula structure ABO3.

[0059] In one embodiment, the thin film ceramic layer comprises a ceramic material having a ceramic composition Ba(Zr x Ti 1-x )O3, wherein preferably 0.05 ≤ x ≤ 0.6 is satisfied.

[0060] In one embodiment, the thin film ceramic layer can be composed of a ceramic material.

[0061] In addition, the ceramic material can contain dopants to change the properties of the ceramic.

[0062] In one embodiment, the ceramic material contains y wt% of a rare earth metal dopant, especially yttrium, wherein preferably 0.2 ≤ y ≤ 2 is satisfied. The ratio y refers to 100 wt% of Ba(Zr x Ti 1-x )O3.

[0063] In one embodiment, the ceramic material contains z wt% of a transition metal dopant, especially manganese, wherein preferably 0.11 ≤ z ≤ 1 is satisfied. The ratio z refers to 100 wt% of Ba(Zr x Ti 1-x)100 wt% of O3.

[0064] The ceramic material has advantageous electrical and mechanical properties, especially when used in thin films. In addition, the material is environmentally compatible as it does not contain lead.

[0065] In an alternative embodiment, a ceramic material containing lead is selected, such as (Pb x Zr 1-x )TiO3 with a preferred x value between 0.4 - 0.6 (0.4 ≤ x ≤ 0.6) or Pb(Mn x Nb 1-x )O3 + PbTiO3 with a preferred x value between 0.2 - 0.4 (0.2 ≤ x ≤ 0.4), which also has advantageous electrical and mechanical properties when used in thin films.

[0066] In one embodiment, the thin - film device is configured as a circular plate.

[0067] The circular shape has advantages in terms of manufacturing, handling, and application, such as in terms of mechanical stability.

[0068] In one embodiment, the thin - film device is configured as a three - dimensionally folded foil.

[0069] The folded foil can adapt to the shape of different application objects in a flexible manner. In particular, the foil can be elastic and can be adapted to be folded into various shapes and then refolded into its original shape.

[0070] In particular, according to the Japanese paper - cutting art technique, the foil can contain several cuts or excisions to achieve the desired flexible properties of the fold.

[0071] In one embodiment, the ceramic thin film has a thickness between 0.3 μm and 5 μm, preferably between 0.3 μm and 1.5 μm.

[0072] Since these dimensions are sufficient to achieve the desired mechanical properties, the consumption of the ceramic material can be reduced. The thin - film layer preferably has uniform mechanical and electrical properties.

[0073] According to the present invention, the thin - film device as described above can be used as the dielectric electrode structure, capacitor structure, or multi - layer capacitor structure as detailed previously.

[0074] In addition, the present invention relates to a dielectric electrode structure, capacitor structure, multi - layer capacitor structure, especially a multi - layer electrode capacitor structure or a multi - layer ceramic capacitor (MLCC) structure, which comprises the thin - film device as detailed previously.

[0075] In addition, the present invention relates to a medical device for medical, diagnostic, or therapeutic treatment (such as electro - cancer treatment), which comprises the thin - film device or especially the dielectric electrode structure.

[0076] In addition, the present invention relates to a method for manufacturing a substrate for depositing a thin film, which includes several steps.

[0077] The substrate and the ceramic thin film can be constructed as described above. In particular, the aforementioned substrate and ceramic thin film can be manufactured by the following method.

[0078] In the first step, a titanium foil is provided to form a base layer.

[0079] In another step, the base layer is heat-treated or anodized to form an intermediate layer that is directly adjacent to the base layer. The intermediate layer contains titanium oxide or consists of titanium oxide.

[0080] By directly forming a titanium oxide layer on the base layer, the formation of a natural mixed metal oxide layer is prevented.

[0081] In one embodiment, during the heat treatment, the base layer is heated to a first holding temperature, preferably between 550 °C and 620 °C, in the first step, and to a second holding temperature, preferably between 640 °C and 700 °C, in the second step.

[0082] Through the described step-by-step thermal processing, a dense intermediate layer without open-pore porosity can be manufactured. This can be understood as enabling the corresponding produced film to be dense. Moreover, it can be without open pores.

[0083] Due to the heat treatment, an intermediate layer with desired properties is formed.

[0084] In addition, the present invention relates to a method for manufacturing a thin film device including a substrate for depositing a thin film. The method can include the steps mentioned above. In addition, the method can include several additional steps.

[0085] In one step, a ceramic material for the ceramic thin film layer in a viscous state is provided. The ceramic material in a viscous state can be a viscous paste containing organic substances and / or solvents.

[0086] In another step, the ceramic material is set on the surface of the intermediate layer facing away from the base layer in a viscous state to form a thin film ceramic layer.

[0087] After deposition, the deposited thin film ceramic layer is preferably dried on a hot plate. Preferably, the drying of the ceramic thin film is carried out at a temperature between 150 °C and 250 °C. In this step, the remaining solvent can be removed.

[0088] After drying, the dried thin film ceramic layer is calcined or pyrolyzed. Preferably, the calcination of the thin film is preferably carried out in two steps in a furnace at a temperature between 300 °C and 600 °C. The first calcination step can be carried out between 300 °C and 400 °C. The second calcination step can be carried out between 500 °C and 600 °C. Residual organic matter can be removed in this step.

[0089] In another step, preferably in a furnace, the calcined thin film ceramic layer is crystallized. The crystallization of the thin film is preferably carried out at a temperature between 600 °C and 700 °C.

[0090] In one embodiment, the deposition of the ceramic material is completed by slot-die coating.

[0091] By slot-die coating, the ceramic thin film layer can be deposited with a desired thickness and structure.

[0092] Alternative methods for depositing the thin film layer would be spin coating or dip coating, spray pyrolysis, and inkjet printing. Alternatively, the thin film layer can also be deposited by physical methods (such as sputtering, pulsed laser deposition (PLD), or aerosol deposition). In this case, a solid ceramic target and / or ceramic powder with a desired composition is used.

[0093] In one embodiment, the ceramic material is deposited by stacking a number of sub-layers, where each sub-layer has a thickness between 0.1 μm and 0.5 μm. Preferably, each sub-layer has a thickness between 0.2 μm and 0.3 μm. The desired thickness of the sub-layers is achieved by selecting a suitable viscous ceramic material (such as a suitable ceramic paste with a suitable composition). Preferably, the ceramic paste contains an organic polymer material.

[0094] By applying sub-layers with the said thickness, the entire ceramic thin film layer can be formed by applying only a few sub-layers (preferably 1 - 5 sub-layers).

[0095] The entire process of deposition, drying, calcination / pyrolysis, and crystallization can be carried out 1 - 5 times until the final thickness of the ceramic thin film layer is reached.

[0096] By reducing the number of sub-layers, a uniform structure of the ceramic thin film layer can be obtained. The sensitivity to defects or damage during manufacturing is reduced.

[0097] In one embodiment, providing the ceramic material in a viscous state includes several steps. Preferably, the steps include a chemical solution deposition procedure.

[0098] In one step, a first solution is prepared by dissolving a barium salt (such as barium acetate). The barium salt can be dissolved in glacial acetic acid, water, and ethanolamine.

[0099] Optionally, a yttrium salt (such as yttrium acetate) and a manganese salt (such as manganese acetate) can be dissolved in the first solution to obtain a doped ceramic material.

[0100] 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 can be polyvinylpyrrolidone (PVP).

[0101] In another step, tetraethoxy titanium and propoxy zirconium are dissolved in the second solution. Meanwhile, the solution can be stirred.

[0102] Then, the first solution and the second solution are mixed and preferably stirred to form a sol-gel.

[0103] In a preferred embodiment, the 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 and 2 - 8 moles of water and ethanolamine. In addition, 0.1 - 0.8 moles of polyvinylpyrrolidone are dissolved in 3 - 10 moles of ethanol and 15 - 30 moles of acetic acid to prepare the second solution. Tetraethoxy titanium and propoxy zirconium are added stoichiometrically to the second solution under stirring. Then, the first solution is added to the second solution. The two solutions are mixed together by stirring.

[0104] Preferably, the resulting solution forms a ceramic paste with a viscosity between 10 - 100 cP (1 cP = 10 -3 kg / ms).

[0105] In one embodiment, the geometry of the thin film device is constructed by cutting (such as by mechanical cutting or laser cutting) or by stamping.

[0106] In one embodiment, the thin film device is three-dimensionally formed by cutting or stamping and folding the thin film device. In particular, by using the paper-cut art technique (which is a combination of cutting and origami folding techniques), the thin film device can be three-dimensionally formed. The cut or punched parts can make the thin film device more flexible. The thin film device can be adapted to the shape of various objects to which the device is applied.

[0107] The application of the paper-cut art technique used allows the flat device structure to become a three-dimensional structure when a force is applied and return to the original flat structure when the force is removed without deforming the device.

[0108] Due to the ability to adapt to moving or expanding elements and optimize the contact with these elements, especially in the case of a larger contact area, the paper-cut art cutting device is superior to other ceramic thin film devices. Exemplary elements are moving machine elements or human or animal bodies.

[0109] Subjects with different designs can be cut or stamped into the device.

[0110] The present invention will be explained in more detail below with reference to the accompanying drawings. The accompanying drawings show:

[0111] Figure 1 A first embodiment of the thin-film device is shown in a sectional view.

[0112] Figure 2 An SEM (scanning electron microscope) photograph showing a cross-section of a first embodiment of the thin-film device.

[0113] Figure 3 A second embodiment of the thin-film device is shown in a sectional view.

[0114] Figure 4 A third embodiment of the thin-film device is shown in a sectional view.

[0115] Figure 5 A fourth embodiment of the thin-film device is shown in a sectional view.

[0116] Figure 6 A process flow chart showing important manufacturing steps.

[0117] Figure 7 A possible circular shape of the finished thin-film device is shown.

[0118] Figure 8 A possible three-dimensional folded shape of the finished thin-film device is shown.

[0119] Figure 9 Two SEM photographs are shown. A cross-section of a first embodiment of the thin-film device is shown on the right. A cross-section of a thin-film device manufactured in a different way is shown on the left for comparison.

[0120] Figure 10 Show Figure 9 The dependence of the electric power loss of the two different thin-film devices shown on the electric frequency.

[0121] Figure 11 The dependence of the capacitance density and the electric power loss of a first embodiment of the thin-film device on the electric frequency is shown.

[0122] Figure 12 The dependence of the capacitance and the electric power loss of a first embodiment of the thin-film device on temperature is shown. A temperature range near body temperature (37 °C) is selected.

[0123] Figure 13 Show Figure 9 The dependence of the capacitance and the electric power loss of the ceramic device manufactured in a different way for comparison shown on the left on temperature. Again, a temperature range near body temperature (37 °C) is selected.

[0124] Figure 14Show the dielectric breakdown strength of the first embodiment of the thin film device. Measure the dependence of the current on the electric field. The breakdown point is about 33 kV / mm.

[0125] Similar or identically marked elements in the figures are denoted with the same reference numerals. The figures and the scales in the figures are not scalable.

[0126] Figure 1 Show an embodiment of the thin film device 1. The thin film device 1 comprises a substrate 2, the substrate 2 comprises a base layer 3 and an intermediate layer 4, and further comprises a ceramic thin film layer 5.

[0127] The layers are stacked in a stacked form to form the multi-layer device 1.

[0128] The base layer 3 comprises titanium metal. Preferably, the layer 3 consists of titanium (Ti).

[0129] The base layer 3 may consist of a Ti foil. The thickness of the Ti foil may be between 5 μm and 1000 μm, preferably between 5 μm and 100 μm.

[0130] The intermediate layer 4 is directly disposed on the surface of the base layer 3. No additional layer or structure is disposed between the base layer 3 and the intermediate layer 4.

[0131] The intermediate layer 4 comprises titanium dioxide TiO2 or preferably consists of titanium dioxide. The titanium dioxide preferably has a rutile structure.

[0132] The thickness of the intermediate layer may be between 0.1 μm and 2 μm, preferably between 0.8 μm and 1 μm.

[0133] The substrate 2 may be used as an electrode to contact the ceramic thin film. Alternatively, in another embodiment, a separate electrode layer may be provided, which is configured as a bottom electrode between the substrate 2 and the ceramic thin film layer 5 or is configured as a top electrode, whereby the ceramic thin film layer 5 is sandwiched between the substrate and the top electrode.

[0134] On the surface of the intermediate layer 4 opposite to the surface contacting the base layer 3, the ceramic thin film layer 5 is deposited.

[0135] The ceramic thin film may have a thickness between 0.3 μm and 5 μm, preferably between 1.5 μm and 5 μm.

[0136] In the shown embodiment, the ceramic thin film layer 5 is directly adjacent to the intermediate layer 4. No additional layer or structure is disposed between them.

[0137] The ceramic thin film layer 5 may comprise or consist of a ceramic material having the composition Ba(Zr x Ti 1-x )O3, wherein preferably 0.05 ≤ x ≤ 0.6 is satisfied.

[0138] Table 1 shows the results of EDX (Energy Dispersive X-ray Spectroscopy) measurements of the composition of the base layer, intermediate layer, and ceramic film of an exemplary ceramic film device. The ratios of the different elements are expressed in atomic %.

[0139] Table 1:

[0140]

[0141]

[0142] In addition, the ceramic material preferably contains a dopant to change the properties of the ceramic. In particular, the ceramic material contains, for example, y wt% of a rare earth metal dopant, especially yttrium, where 0.2 ≤ y ≤ 2. The ratio y refers to 100 wt% of Ba(Zr x Ti 1-x )O3. In addition, the ceramic material contains, for example, z wt% of a transition metal dopant, especially manganese, where 0.11 ≤ z ≤ 1. The ratio z refers to 100 wt% of Ba(Zr x Ti 1-x )O3.

[0143] Figure 2 An SEM photograph of a cross-section of the thin film device 1 according to the first embodiment is shown. The base layer 3, intermediate layer 4, and ceramic film layer 5 are shown. The surface of the shown base layer 3 has a favorable low surface roughness Ra of less than 0.3 μm.

[0144] Figure 3 Another embodiment of the device 1 is shown.

[0145] Different from the first embodiment, the second embodiment of the device 1 includes some additional layers.

[0146] A metal inner electrode layer 6 for electrical contact is arranged between the intermediate layer 4 and the thin film layer 5.

[0147] A second electrode 7 is deposited on the opposite surface of the thin film layer 5.

[0148] The second embodiment of the thin film device 1 can be used as a capacitor, while the first embodiment can be used as a dielectric electrode structure for applying an electric field to a selected object, especially the human body, for example, for medical, diagnostic, or therapeutic applications.

[0149] Due to its electrical properties, the thin film device 1 can generally be adapted to be used at body temperature.

[0150] In Figure 4 , the device 1 configured as a multi-layer electrode capacitor is shown. The capacitor device 1 is constructed by stacking a number of ceramic thin film layers 5 and electrode layers 7. Thus, a series of individual capacitor elements are formed.

[0151] In Figure 5 , a device 1 configured as a multilayer ceramic capacitor (MLCC) is shown. The capacitor device 1 includes a plurality of ceramic film layers 5 and electrode layers 7, where the electrode layers are alternately contacted by two different outer electrodes on opposite side surfaces of the device 1.

[0152] Figure 6 Selected steps of the manufacturing process of a first embodiment of the thin film device 1 are outlined graphically.

[0153] A first solution is prepared by dissolving, for example, barium acetate, yttrium acetate, and manganese acetate in glacial acetic acid, water, and ethanolamine. In a second solution, polyvinylpyrrolidone is dissolved in ethanol and acetic acid. Tetraethoxy titanium and propoxy zirconium are added to the second solution under stirring. The first solution and the second solution are mixed to form a sol-gel.

[0154] Furthermore, in the illustrated step S1, a titanium foil for the substrate 2 is provided and is heat-treated in a furnace in an air atmosphere by heating it to a temperature between 550 °C and 620 °C in a first step and then by heating it to a temperature between 640 °C and 700 °C in a second step. Through the described heat treatment process, an intermediate layer 4 is formed on the surface of the titanium base layer 3.

[0155] In step S2, the pre-prepared sol-gel is deposited on the substrate 2, for example, via spin coating, dip coating, or slot coating, with a thickness up to 0.05 mm. In step S3, the film 5 is then dried, for example, on a hot plate at a temperature between 150 °C and 250 °C. Thereafter, in step S4, the ceramic film layer is pyrolyzed twice by heating the device 1 in an oven in an air atmosphere at a temperature between 300 °C and 400 °C and then at a temperature between 500 °C and 600 °C.

[0156] Furthermore, the ceramic film layer 5 is crystallized in a furnace in an air atmosphere at a temperature between 600 °C and 700 °C.

[0157] In step S5, the processes of deposition, drying, calcination / pyrolysis, and crystallization are carried out 3 - 5 times until the final thickness of the ceramic film layer 5 is reached.

[0158] Then, a preferred geometry can be punched or cut out from the provided layer structure to obtain the desired shape of the device 1.

[0159] Figure 7 An exemplary circular punching shape of the finished thin film device with a through hole in its center is shown.

[0160] The circular element can have a diameter between 10 mm and 25 mm and have a concentric through hole with a diameter between 3 mm and 4 mm.

[0161] Typically, the ceramic thin film layer 5 can cover the entire surface of the substrate 2 or only a defined area. For example, as shown, for example, in Figure 7 the substrate portion near the substrate edge can remain uncovered.

[0162] Instead Figure 7 , Figure 8 Another embodiment of the display device 1. The device 1 is manufactured by using paper-cut art techniques.

[0163] Figure 8 The embodiment in is merely an example of a paper-cut art pattern. By cutting or stamping different themes into the provided multi-layer structure, more different patterns can be produced.

[0164] Figure 9 Again, an SEM photograph of a cross-section of the first embodiment of the thin film device 1 according to the present invention is shown on the right. In addition, for comparison, Figure 9 an SEM photograph of another thin film layer device manufactured by a method different from the above method is shown on the left.

[0165] The device on the left is not part of the present invention and comprises a stainless steel substrate 8 on which an unwanted mixed metal oxide layer 9 is formed. No smooth surface is provided between the single layers. The intermediate layer 10 between the metal oxide layer and the ceramic thin film layer 11 consists of lanthanum nickelate (nickel lanthanum oxide, LNO). The ceramic thin film layer contains barium zirconate titanate ceramics and unwanted metal impurities caused by the interdiffusion between the metal and metal oxide layers and the ceramic thin film.

[0166] The impurities have a significant unwanted effect on the mechanical properties (and especially the electrical properties) of the ceramic thin film 5.

[0167] In Table 2, the EDX measurement results of the composition of the base layer, intermediate layer, and ceramic thin film of the device not of the present invention are shown. The above-mentioned impurities due to the interdiffusion effect can be identified. The ratios of different elements are expressed in atomic %.

[0168] Table 2:

[0169] O Si Ti Cr Fe Ni Zr Ba La Ceramic film 64.7 - 11.8 - 1.12 - 1.9 19.3 1.1 Intermediate layer 49.3 0.3 1.4 2.4 3.8 21.4 0.4 2.6 18.3 Metal oxide layer 41.9 1.6 - 27.4 14.1 4.6 - - 6.4 Base layer - 1.6 - 17.1 73.8 6.1 - - -

[0170] Figure 10 Shows the power loss at different applied electrical frequencies when comparing the first embodiment (solid line) of the device 1 of the present invention and the non-inventive embodiment (dashed line) of the thin film device.

[0171] The electrical loss is expressed as tan(δ). The frequency is expressed in hertz (Hz). The measurement is carried out at room temperature.

[0172] It can be clearly seen that, for the embodiments of the present invention, the electrical loss is small and less dependent on the frequency. In particular, as the frequency increases, the loss can be significantly reduced. Figure 10 It can be clearly seen that, for the embodiments of the present invention, the electrical loss is small and less dependent on the frequency. In particular, as the frequency increases, the loss can be significantly reduced.

[0173] Figure 11 Shows the capacitance density (solid line) in nF / cm for the same embodiments of the present invention for the thin-film device 1 2 and once again shows the electrical loss (dashed line). As can be seen from Figure 11 it, the capacitance density and the electrical loss do not depend on or only very little depend on the applied electrical frequency.

[0174] The measurements were again carried out at room temperature.

[0175] Figure 12 Shows the dependence of the capacitance and electrical loss on temperature for the first embodiment of the present invention for the thin-film device 1. In the temperature range between 19.5 °C and 42 °C, both values undergo a change of less than 10%. Thus, the thin-film device 1 is suitable for applications at body temperature (e.g., in the human body).

[0176] In particular, the thin-film device 1 can be used as a dielectric electrode structure for applying an electric field to the human body for cancer treatment by means of tumor treating fields.

[0177] Figure 13 Shows the dependence of the capacitance and electrical loss on temperature for a non-inventive embodiment of the device for comparison. In the temperature range between 19.5 °C and 42 °C, both values undergo a large change.

[0178] As a result, the device 1 of the present invention exhibits a lower temperature dependence of the capacitance and electrical loss.

[0179] Furthermore, the thin-film device has a favorable high dielectric breakdown strength.

[0180] Figure 14 Shows the dielectric breakdown strength of the first embodiment of the thin-film device. The dependence of the measured current on the electric field is measured. The breakdown point is about 33 kV / mm.

[0181] Reference numerals

[0182] 1 thin-film device

[0183] 2 substrate

[0184] 3 base layer

[0185] 4 intermediate layer

[0186] 5 ceramic thin-film layer

[0187] 6, 7 electrode layers

[0188] 8 Stainless steel substrate

[0189] 9 Mixed metal oxide layer

[0190] 10 LNO layer

[0191] 11 Ceramic thin film layer with impurities

Claims

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

2. The substrate (2) according to claim 1, for depositing a ceramic thin film (5), wherein the substrate is adapted such that a thin film ceramic layer (5) can be deposited on the intermediate layer.

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 - 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 - 4, wherein the base layer (3) has a thickness between 5 μm and 1000 μm, preferably between 5 μm and 100 μm.

6. The substrate (2) according to any one of claims 1 - 5, 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 claims 1 - 6, wherein the intermediate layer (4) has a thickness 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 - 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 claims 1 - 8, wherein the thickness of the intermediate layer is greater than the thickness of the natural oxide layer on the titanium.

10. The substrate (2) according to any one of claims 1 - 8, wherein the intermediate layer (4) exhibits self - healing properties.

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

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

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

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. The thin - film device (1) according to claim 13 or 14, wherein the thin - film device (1) consists of the substrate (2) and the thin - film ceramic layer (5).

16. The thin - film device (1) according to claim 13 or 14, wherein the thin - film device (1) comprises exactly one inner electrode (6, 7) layer or a plurality of inner electrode layers (6, 7).

17. The thin - film device (1) according to claim 16, wherein the thin - film device (1) comprises a plurality of thin - film ceramic layers (5).

18. The thin - film device (1) according to any one of claims 13 - 17, wherein the ceramic film ceramic layer (5) comprises a ceramic material with a composition of Ba(Zr x Ti 1-x )O3 where 0.05 ≤ x ≤ 0.6, or a ceramic material (Pb x Zr 1-x )TiO3 where 0.4 ≤ x ≤ 0.6, or a ceramic material Pb(Mn x Nb 1-x )O3 + PbTiO3 where 0.2 ≤ x ≤ 0.

4.

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

20. The thin film device (1) according to any one of claims 13-19, wherein the thin film device (1) is configured as a circular plate.

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

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

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

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

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

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

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

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

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

31. A method for manufacturing a thin film device (1), comprising the steps for manufacturing the substrate (2) according to any one of claims 27-30, and further comprising the following steps: - providing a ceramic material in a viscous state for the ceramic thin film layer (5), - depositing the ceramic material in the viscous state on the surface of the intermediate layer (4) facing away from the base layer (3) to form a thin film ceramic layer (5), - drying the deposited thin film ceramic layer (5), - calcining the dried thin film ceramic layer (5), - crystallizing the calcined thin film ceramic layer (5).

32. The method according to claim 31, wherein providing the ceramic material in the viscous state comprises the following steps: - dissolving a barium salt in a first solution, - Dissolve the organic polymer in a second solution, - Dissolve tetraethoxy titanium and propoxy zirconium in the second solution, - Mix the first solution and the second solution to form a sol-gel.

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

34. The method according to any one of claims 31-33, wherein the deposition of the ceramic material is completed by slot coating.

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

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

37. The method according to any one of claims 31-36, wherein the geometry of the thin film device (1) is constructed by cutting or stamping.

38. The method according to any one of claims 31-37, wherein the thin film device (1) is three-dimensionally formed by cutting and folding the thin film device, in particular by using paper-cut art techniques.

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