DE102016225671A1 - Piezoelectric stack actuator and method of making the same - Google Patents

Abstract

A method (100) of manufacturing a piezoelectric stack actuator (200), comprising the steps of: providing (110) a piezoelectric layer (202) having a columnar layer structure, due to the columnar layer structure starting from a surface region (202a) of the piezoelectric layer (202) spaces (206) are formed with channels (206a) and trenches (206b) between adjacent columns (204) in the piezoelectric layer (202); Introducing (120) a conductive electrode structure (208) into the piezoelectric layer (202), the conductive electrode structure (208) starting from the surface region (202a) of the piezoelectric layer (202) into channels (206a) of the piezoelectric layer (202) extends; Inserting (130) an insulating material (210) into spaces (206) in the piezoelectric layer (202) to mechanically couple adjacent columns (204) at least in regions; and arranging (140) a metallization structure (212) on the surface region (202a) of the piezoelectric layer (202) in electrical contact with the conductive electrode structure (208).

Description

The present invention relates to piezoelectric stack actuators and to a process for their preparation. In particular, the present invention relates to multilayer, lateral, piezoelectric stack actuators and to a method for their production.

Piezoelectric ceramic materials allow the construction of fast actuators that can deliver great forces. A very common material with large piezoelectric coefficients is lead zirconate titanate (PZT). However, simple piezoelectric actuators, despite high drive voltages of up to a few 100 V, are limited to small displacement paths (travel paths or strokes). Larger deflections can be achieved, for example, only by a mechanical force-displacement conversion or by a series connection of a large number of individual piezoelectric actuators in a stack. For this purpose, a multiplicity of layers of a piezoelectrically active material and the respective associated electrodes are stacked on top of each other so that the individual deflections of each unit add up when they are activated.

While ceramic "macroscopic" stack actuators with up to 200 individual layers, such as for driving fast injectors in diesel engines, are already being used in practice, stack actuators are well known in the art of microtechnology. Microactuators, not yet in practical use. Processes for the production of bodies and geometric structures with dimensions in the micrometer range (0.1-1000 μm) are to be taken into consideration as manufacturing processes falling under the microtechnology.

The production of a plurality of stacked layers of piezoelectric material in thin-film technology is associated with major technological hurdles. Thus, a high number of lithography and structuring steps for the piezoelectric material and its electrodes is necessary. In addition, the production in thin-film technology requires relatively high process temperatures, which often lead to detachment at the piezomaterial-electrode composite. Therefore, previously produced in thin-film stack actuators are not available in practice or only with very few individual layers, since a very high production cost for corresponding thin-film stack actuators is present, with thin-layer stack actuators can not be reliably realized with more individual layers.

With regard to the realization of piezoelectric microactuators, the following situation thus arises in the field of thin-film technology: Piezoelectric microactuators are used almost exclusively as individual layers of piezoelectric materials for the construction of piezoelectric bending transducers. In such an arrangement as a piezoelectric bending transducer, the small lateral strains of the active piezoelectric layer can be converted into a bend, whereby a significantly increased deflection can be achieved at the tip of the actuator. However, this embodiment is at the expense of the forces that can be generated and the achievable drive speeds. On the other hand, if large deflections (strokes) and also large forces, i. requires a large power supply, this is only possible by drastically increasing the thickness of the piezoelectric layer material. However, since the elongation of the piezoelectric layer is dependent on the driving, applied electric field strength, increasing the layer thickness equally leads to an increase of the necessary drive or working voltages up to a few 100 V. However, such working voltages can not be achieved in many practical applications of microsystem technology provided and therefore not be tolerated.

Thus, the realization of multi-layer stack actuators has been confronted with a whole series of serious technological problems. Thus, the necessary process temperatures of 600 ° C - 700 ° C lead to undesirable reactions of the PZT material with the metal electrodes already prepared and ultimately to a poor adhesion of these metal electrodes on the PZT material. Furthermore, each additional layer plane also means additional process steps in the form of lithographic and etching steps for their structuring, which further increase the production costs and thus the production costs. Because of these problems, multilayer thin-film actuators of this kind have not yet found their way into practical implementation, with realization of multilayer thin film actuators hitherto restricted to a maximum of five individual layers with a total thickness of 5 μm (see also [1] and [6]).

Starting from this prior art, the object underlying the present invention is to provide improved piezoelectric actuators as well as an improved manufacturing method for piezoelectric actuators.

This object is solved by the independent claims. Inventive developments are defined in the dependent claims.

A method for producing a piezoelectric stack actuator comprises the steps of: providing a piezoelectric layer having a columnar layer structure, wherein due to the columnar layer structure, spaces having channels and trenches are formed between adjacent columns in the piezoelectric layer from a surface portion of the piezoelectric layer; Introducing a conductive electrode structure into the piezoelectric layer, the conductive electrode structure extending from the surface region of the piezoelectric layer into channels of the piezoelectric layer; Introducing an insulating material into intermediate spaces in the piezoelectric layer in order to at least partially mechanically couple adjacent columns to one another; and placing a metallization structure on the surface region of the piezoelectric layer in electrical contact with the conductive electrode structure.

A piezoelectric stack actuator includes a piezoelectric layer having a columnar layer structure, and due to the columnar layer structure, spaces having channels and trenches are formed between adjacent columns in the piezoelectric layer from a surface portion of the piezoelectric layer; a conductive electrode structure in the piezoelectric layer, the conductive electrode structure extending vertically from the surface portion of the piezoelectric layer into a plurality of the channels of the piezoelectric layer; an insulation material at least partially in remaining interstices in the piezoelectric layer in order to at least partially mechanically couple / connect adjacent columns with one another; and a metallization structure on the surface region of the piezoelectric layer in electrical contact with the conductive electrode structure in the piezoelectric layer.

The core idea of the present invention is, instead of a vertical layer structure in which many layers of piezoelectric material are stacked on top of each other, to realize a lateral construction of a piezoelectric stack actuator in which many layers, e.g. in a substrate, are arranged side by side. In this case, the plurality of thin, laterally juxtaposed strips (layers) are mechanically or non-positively connected to each other. For this purpose, the pronounced columnar (columnar) structure of piezoelectric, thick PZT layers is used for vertical structuring of both the piezoelectric layer elements and the required (electrically) conductive electrodes, wherein in the integration of the necessary electrodes and in the microtechnical "lateral" structuring the (intermediate) narrow strip of piezoelectric material, the mechanical connection (positive engagement) of the entire composite material can be maintained. The columnar structure of piezoelectric layers made by, for example, a gas flow sputtering process is i.A. also pronounced anisotropic. The vertical structuring of both the piezoelectric layer elements and the required (electrically) conductive electrodes can therefore be perpendicular to the lateral arrangement while maintaining the mechanical connection of the entire composite material to obtain the laterally alternating arrangement of the conductive electrodes and the piezoelectric layer elements.

In the production of the laterally alternating arrangement, therefore, structures such as metal electrodes, a mechanical bonding material, etc., for example, in each case in individual manufacturing steps are introduced vertically into the piezoelectric material to the surface area.

In the manufacturing method, for example, a single (continuous) relatively thick (e.g., 5 - 50 μm or 5 - 35 μm thick) piezoelectric layer (e.g., a PZT layer) having a columnar layer structure may be provided. The columnar layer structure has spaces (pores) with (wide) channels and (narrow) trenches between adjacent columns in the piezoelectric layer starting from a surface area of the piezoelectric layer. A conductive electrode structure is introduced into the columnar layer structure of the piezoelectric layer by periodically introducing a (at a relatively low temperature <350 ° C) liquefiable metal material such as gallium or indium into the piezoelectric layer. The infiltration can be vertical to the surface area, i. perpendicular to the lateral extent of the piezoelectric layer, take place. By the term "liquid or liquefiable metals" is meant at low temperatures liquefiable metals, metal alloys or solders.

The introduction or infiltration of the liquefied metal material can take place under elevated pressure such that the liquefied metal material is introduced or infiltrated into (predetermined) regions of the PZT layer only along the vertical interspaces.

The areas to be provided with the metal material may be defined, for example, by means of a corresponding masking on the surface area of the piezoelectric layer, i. these areas are exposed and not covered by the masking material. By appropriate pressure adjustment on the liquefied metal material, penetration of the liquid (liquefied) metal material onto the (relatively large) vertical channels or pores, for example having a diameter between 20 and 30 nm, can occur between the pillars of the piezoelectric layer be limited. The electrodes are e.g. the vertical metallizations in the columnar layer structure of the piezoelectric layer after solidification or cooling of the metal material.

Subsequently, the piezoelectrically "active" areas between the electrodes can be infiltrated by an additional insulating coating, glued together and thus mechanically coupled to each other non-positively. The additional insulating coating (ALD Atomic layer deposition = ALD) can be introduced, for example by means of a so-called "ALD process", wherein as an insulating material can be used for the coating, among other materials, for example, TiO _2.

Hereinafter, for example, the applied insulating material, i. the ALD layer, in the region of the metal electrodes reaching to the surface, are removed to expose the metal electrodes at least at the surface area of the piezoelectric layer. The removal of the insulating material may take place, for example, starting from the surface region of the piezoelectric layer (for example, in layers or parallel to the surface region) into the columnar layer structure. The exposure can be done for example by means of plasma etching. Thereupon, a further superficial metal structure (metallization structure) may be locally provided on the surface region of the piezoelectric layer in electrical contact with the conductive electrode structure in the piezoelectric layer and interconnected, for example, to form an interdigital structure.

An electrical drive of the entire stack, i. the piezoelectric stack actuator may eventually be made with a relatively low control voltage (e.g., in a range of 10V or 5 - 15V, etc.) across the fabricated interdigital structure. On the one hand, the deflection (expansion) of the piezoelectric stack resulting from an electric drive can now be used, for example, "directly" if the piezoelectric layer is free-standing, ie. is mechanically decoupled from a substrate. On the other hand, the piezoelectric layer, i. the piezoelectric Stapelaktuator, in a so-called "bimorph arrangement" a strong bending are generated. In a so-called "bimorph arrangement", the piezoelectric stack is arranged laterally on a bending beam (cantilever) or a deflectable membrane, so that an electrical activation of the piezoelectric stack actuator as actuator movement causes a deflection of the bending beam or the membrane.

The inventive concept of a piezoelectric stack actuator and its production method is thus based on a piezoelectric layer having a columnar layer structure and an electrode or metallization structure arranged therein and an insulation material arranged therein. The manufacturing method according to the invention thus describes the realization of the integration of metal electrodes vertically to a surface area of the piezoelectric layer, i. in an additional third dimension (3D integration), for contacting a piezoelectric material. While in microsystem technology the electrodes in piezoelectric devices have heretofore been limited to a planar arrangement, according to the present concept an implementation is now also implemented in the third dimension, i.e. into the piezoelectric material. In combination with thick, columnar (columnar) piezoelectric layers, the production of lateral stack actuators can achieve a multiplication of the piezoelectric effect in micromechanical components. Unlike a vertical thin-film stack actuator, with relatively few process steps in the lateral stack actuator, i. in the laterally arranged piezoelectric layer, a large number of "layers", e.g. in the order of 100 layers, in the form of the electrode or Metallisierungsstrukturen be generated within the piezoelectric layer. Although each individual layer is controlled by the controller at a significant low voltage, e.g. in the range of 10V, producing only a relatively small "single" strain (deflection), the overall system, i. the entire lateral piezoelectric stack actuator is extremely stretched over the large number of discrete elements defined by the electrode structure in the piezoelectric layer.

• 1A-F ein prinzipielles Block- bzw. Ablaufdiagramm des Verfahrens zur Herstellung eines piezoelektrischen Stapelaktuators gemäß einem Ausführungsbeispiel;
• 2 eine Prinzipdarstellung eines piezoelektrischen Stapelaktuators gemäß einem Ausführungsbeispiel;
• 3A eine Querschnittsdarstellung (Bruch) einer beispielhaften piezoelektrischen Schicht mit einer säulenförmigen Schichtstruktur gemäß einem Ausführungsbeispiel;
• 3B eine Draufsicht auf eine beispielhafte (schräg angeschliffene) piezoelektrische Schicht mit einer säulenförmigen Schichtstruktur mit interkolumnaren Poren gemäß einem Ausführungsbeispiel; und
• 3C eine beispielhafte Darstellung der Porengrößenverteilung sowie des kumulativen Porenvolumens in Abhängigkeit vom Porendurchmesser (Pore = Zwischenraum).

Preferred embodiments of the present invention will be explained below with reference to the accompanying drawings. Show it:

• 1A-F a schematic block or flow chart of the method for producing a piezoelectric stack actuator according to an embodiment;
• 2 a schematic diagram of a piezoelectric stack actuator according to an embodiment;
• 3A a cross-sectional view (fracture) of an exemplary piezoelectric layer having a columnar layer structure according to an embodiment;
• 3B a plan view of an exemplary (obliquely ground) piezoelectric layer having a columnar layer structure with inter-columnar pores according to an embodiment; and
• 3C an exemplary representation of the pore size distribution and the cumulative pore volume as a function of the pore diameter (pore = gap).

Before embodiments of the method for producing a piezoelectric Stapelaktuators and the construction of a Stapelaktuators themselves are described in detail with reference to the drawings and figures, it is noted that identical, functionally identical or equivalent elements, objects, functional blocks and / or method steps in the different figures are provided with the same reference numerals, so that the description of these elements, objects, functional blocks and / or method steps shown in different embodiments is interchangeable or can be applied to each other.

In the following description, different embodiments will be discussed in detail, however, it should be understood that the various embodiments provide many applicable concepts that may be implemented or implemented with a variety of lateral piezoelectric stack actuators and the corresponding fabrication methods thereof. The following specific embodiments discussed are merely various specific ways of making and using the present concept for lateral piezoelectric stack actuators and their fabrication processes.

In the following, reference will be made to 1A-F a basic flow or flow diagram of the method 100 for producing a piezoelectric stack actuator 200 described.

First, in 1A at step 110 a piezoelectric layer 202 provided, which has a columnar (columnar) layer structure. The piezoelectric layer 202 has a plurality of pillars 204 on. Due to the columnar layer structure of the piezoelectric layer 202 are starting from a surface area 202a the piezoelectric layer 202 interspaces 206 with channels 206a and trenches 206b between adjacent columns 204 in the piezoelectric layer 202 educated. In 1B is at step 110 in addition, in a dashed rimmed area a plan view of a portion of the surface area 202a the piezoelectric layer 202 with the columns 204 and with the gaps 206 with channels 206a and ditches 206b given by way of example in an enlarged view. In the partial top view of 1B is only one pillar at a time 204 and only one channel 206a and a ditch 206b (Of a variety of these elements) exemplified by a reference numeral.

In the provided piezoelectric layer 202 will now be in 1C at step 120 a conductive electrode structure 208 in the piezoelectric layer 202 brought in. The structured introduction of the conductive electrode structure 208 can for example by an optional mask structure 214 through. The conductive electrode structure 208 now extends from the surface region 202a the piezoelectric layer, for example vertically into the channels 206a the piezoelectric layer 200 , As in the sectional view of 1C at step 120 is shown, the conductive electrode structure 208 to a plurality of areas 202 - 1 . 202 - 2 ( 202-n ) of the piezoelectric layer 202 in this piezoelectric layer 202 are introduced, for example, a so-called "interdigital structure" with opposing, spaced-apart electrode elements 208 - 1 . 208 - 2 ( 208-n ) to obtain. An optional implementation of the conductive electrode structure 208 (with the individual electrode elements 208 - 1 . 208 - 2 respectively. 208-n ) is in 1D at step 120 additionally in a dashed rimmed area as a plan view of a portion of the surface portion 202a of the piezoelectric layer 202 exemplified.

At step 130 ( 1E ) is now an insulation material (at least partially) in the (remaining) spaces 206 in the piezoelectric layer 202 introduced to each adjacent columns 206 at least partially mechanically (non-positively) to couple with each other. Like now at step 130 from 1E it can be seen, the insulation material 210 also there in the layer areas 202 - 1 . 202 - 2 ( 202-n ) of the piezoelectric layer 202 be introduced or not, or not completely with the material of the conductive electrode structure 208 are filled.

At one step 140 ( 1F ) now becomes a metallization structure 212 with a plurality of metallization elements 212 - 1 . 212 - 2 ( 212-n ) at the surface area 202a the piezoelectric layer 202 in electrical contact with the conductive, in the piezoelectric layer 202 arranged electrode structure 208 with the electrode elements 208 - 1 . 208 - 2 ( 208-n ) arranged.

As in now in the 1D additionally shown by way of example top view, the electrode structure 208 have a so-called "interdigital structure" in which the finger-like structures 208-n the electrode structure 208 what the tines of two combs look like, which interlock without touching each other. To the electrode structure 208 can now via the metallization structure 212 , for example, between the terminal electrodes of the metallization structure 212 by means of a voltage source (not shown in FIG 1F ), a potential V _{P is} applied whose resulting electric field within the piezoelectric layer 202 a deflection .DELTA.S (elongation or contraction) along the longitudinal direction (see x-direction of the coordinate system at 1F ) causes. Is the piezoelectric layer 202 Now, for example, firmly with the substrate 203 connected, this lateral deflection of the piezoelectric layer 202 (in operation) converted into a curvature in the y direction.

In the following, further exemplary embodiments and implementations of the method will now be described 100 for producing the piezoelectric stack actuator 200 with reference to the in the 1A-F described method steps 110 . 120 . 130 and 140 explained in more detail.

At step 110 First, the piezoelectric layer 202 provided. So can the piezoelectric layer 202 for example, by means of a PVD process (PVD = Physical Vapor Deposition) on a substrate 203 , which, for example, a semiconductor material such as silicon, or glass, etc. may have, are applied or deposited. So can the piezoelectric layer 202 For example, by means of a gas flow sputtering process (GFS process) are deposited, wherein the piezoelectric layer 202 a PZT material (PZT = lead zirconate titanate) or other piezoelectric materials may have. By means of the gas flow sputtering process, for example, the piezoelectric layer 202 Anisotropic and columnar deposition, for example, relatively large layer thicknesses between 5 and 50 microns or between 15 and 35 microns, such as 10, 15, 20, 25, 30, 35, 40, 45 microns, and all intermediate values for the applied piezoelectric layer 202 can be obtained. The formation of a columnar layer structure also results in lateral stress decoupling in the piezoelectric layer 202 reached. Due to a mismatch of the thermal expansion coefficient of the substrate material and the material of the piezoelectric layer 202 Otherwise, in the layer deposition mechanical stress in the piezoelectric layer 202 occur. Thus, the relatively large layer thicknesses of the piezoelectric layer 202 stress-free or at least low-stress realized (isolated).

Regarding the PVD process or GFS process for depositing the piezoelectric layer 202 It is pointed out that by the targeted setting of process parameters, such as process temperature, materials, pressure, bias voltage, etc., the particular desired layer thickness D1 and also the resulting anisotropy of the resulting piezoelectric layer 202 and the desired configuration of the columnar layer structure with the desired mean dimensions for the interspaces 206 with the (wider) channels 206a and the (narrower) trenches 206b can be adjusted. To the desired columnar structure of the piezoelectric layer 202 For example, when sputtering (sputtering) to the parts to be coated, a negative voltage (bias voltage) can be applied. This accelerates the positively charged ions on the growing layer and thus provides a possibility to control the dimension of the spaces between the columns in the layer within certain limits.

Around the piezoelectric layer 202 For example, to obtain a constant thickness D1, the surface area 202a the piezoelectric layer (s) 202 if necessary after application of the piezoelectric layer 202 can also be planarized. The planarized surface area 202a The piezoelectric layer 202 with a very constant layer thickness D1 can contribute to the in 1 illustrated process steps 120 . 130 and 140 easier (ie with less technical effort) to perform more accurately (with higher manufacturing precision) and nacharbeitbarer (with lower process deviations).

At step 110 Thus, the piezoelectric layer can 202 by means of a gas flow sputtering process (GFS process) on a substrate 203 deposited and subsequently planarized and / or structured. The piezoelectric layer 202 can be produced by means of the GFS process in different layer thicknesses, eg between 5 and 50 μm or between 15 and 35 μm, with suitable process variations in the GFS process, for example, the desired layer thickness of the piezoelectric layer 202 , the resulting columnar layer structure, ie the resulting spaces (pore sizes) with the channels and trenches, and their anisotropic structure can be adjusted or varied.

Then at the step 120 the conductive electrode structure 208 in this piezoelectric layer 202 structured introduced to the plurality of individual electrode structures 208-n alternating with intervening piezoelectric material layers in the piezoelectric layer 202 to obtain. To this structured introduction of the conductive electrode structure 208 in the piezoelectric layer 202 For example, the (optional) mask pattern (mask) 214 becomes on the planarized surface area 202a the piezoelectric layer 200 applied, so that for the conductive structure 208 with the individual electrode elements 208-n in the piezoelectric layer 202 intended areas 202-n through the mask structure 214 through are exposed. Thereupon, the conductive electrode structure 208 in the of the mask structure 214 uncovered areas 202-n the piezoelectric layer 202 be introduced. Subsequently, the mask structure 214 again from the surface area 202a the piezoelectric layer 202 be removed so that the (planarized) piezoelectric layer 202 In turn, from the surface region 202a of process engineering is editable.

The application of the mask structure 214 on the piezoelectric layer 202 For example, by a photolithographic application of a resist structure 214 on the piezoelectric layer (PZT layer) 202 done, the paint structure 214 (in a vertical projection into the piezoelectric layer 202 ) the areas in the piezoelectric layer 202 defined by the electrodes, ie the conductive electrode structure 208 to be enforced.

Considering an exemplary layer thickness D1 of 10-20 μm (in a vertical direction to the surface area 202a the piezoelectric layer 202 ) may be an exemplary width b _{n of} the individual electrodes 208-n the conductive electrode structure 208 (parallel to the surface area 202a the piezoelectric layer 202) are 1 to 3 μm (or 0.5 to 5 μm), while exemplary distances a _n (parallel to the surface area 202a ) between adjacent electrodes 208-n the conductive electrode layer 208 2 to 4 μm (or 1 to 8 μm).

As another possibility for applying the mask structure 214 For example, a PET (PET = polyethylene terephthalate) material, ie, a thermoplastic, may be used as the mask structure 214 on the surface area 202a the piezoelectric layer 202 applied or sputtered. PET materials may have less adhesion of metal (when introducing the conductive electrode structure 208 ) provide as a mask structure to a conventional photoresist and thus improve the process flow.

In summary, it can thus be stated that the mask structure (protective mask or protective cover) 214 is provided, for example, by means of lithography as a lacquer material and / or as a polymer material on the surface region 202a the piezoelectric layer 202 can be applied to define the free areas for introducing the liquefied solder material. After introducing the solder material to form the electrode structure 208 This cover layer, ie the paint or polymer layer, again removed to the metallization contacts 212-n at the surface area 202a the piezoelectric layer 202 ie the layer structure 212 in contact with the electrode structures 208 to be able to raise.

It is noted in this regard that the use of a mask structure 214 for introducing the conductive electrode structure 208 only as an example, since further procedures for "structured" introduction of the electrode structure 208 are conceivable.

For example, it is conceivable that the conductive electrode structure with a sufficiently high accuracy directly into the piezoelectric layer 202 can be introduced, so that a masking of the surface area 202a the piezoelectric layer 202 does not need to be needed.

For the conductive electrode structure 208 For example, a metallization by means of pressure in predetermined areas 202-n the piezoelectric layer 202 be introduced, wherein a (at low temperatures of eg below 500 ° C or 350 ° C) liquefied metal material by applying pressure or High pressure in at least a majority of the through the mask structure 214 through exposed channels 206a the piezoelectric layer 202 is introduced. When introducing the metal material under pressure into the piezoelectric layer 202 For example, the metal material used may be the temperature of the (at that temperature) liquefied metal material when placed in the piezoelectric layer 202 and the pressure applied to the liquefied metal material is selected to be a plurality (ie, greater than 50% or greater than 80%) of that through the mask structure 214 to fill exposed channels (or capillary) 206a, and further to form the trenches formed between adjacent columns 206b (iw) do not fill or fill at most up to 10% or 20% to prevent being in the (narrow) trenches 206b over the given ranges 202-n form conductive connections.

By doing so, an (undesired) spreading of the generated conductive regions over the predetermined ranges 202-n the piezoelectric layer 202 Be effectively prevented, so that iW only the default areas 202-n the piezoelectric layer 202 be formed conductive.

As liquefiable metal materials or metal alloy materials for forming the conductive electrode structure 208 For example, solders (made of a metal or metal alloy material) which in the liquefied state can be used with the surface regions of the piezoelectric layer 202 in the uncovered channels 206a "React", ie an oxide layer on the surface of the material of the piezoelectric layer 202 form. Thus, metal materials or metal alloy materials can be used after wetting in the capillaries or channels 206a remain after contacting the liquified metal material with the surface of the piezoelectric layer 202 in the capillaries 206 a reaction takes place in the form of a surface oxidation. Further, the metal material or the metal alloy material is to be chosen so that it can be pressed in the liquefied (heated) state in the capillary under the action of pressure, but due to the capillary action acting on this material, the flow of this material is limited, ie between adjacent columns 204 (Capillaries) formed trenches 206b essentially not be filled.

As exemplary materials for the solders, i. for the metals or alloys which can be liquefied under heat, it is possible, for example, to use solder alloys comprising gold (Au) and tin (Sn), with lutetium (Lu) still being added to these AuSn solder alloys. Another example of an insertable solder alloy may comprise silver (Ag) and tin (Sn) components (AgSn solder alloy), wherein material constituents of the subgroup elements cerium or titanium may also be added. In this context, active solders or active or reactive solders are often spoken of.

Depending on the pore structure sizes, ie the size of the channels or capillaries 206a the piezoelectric layer 202 , and the resulting surface tension of the liquefied solder material, for example, a pressure for the injection of the liquefied solder material in the order of between 500 and 1500 bar and, for example, more than 1000 bar are used.

The "channel or gap filling" can thus be carried out by means of a so-called metal infiltration under pressure. Since the required capillary pressure to be overcome in order to be able to press or inject the liquid metal material into the channel structure depends on the diameter of the channels 206a can depend on a corresponding pressure setting, taking into account the respective present (set) columnar layer structure of the piezoelectric layer 202 is selected, the large pores (channels 206a) are filled without the liquefied metal material in the outgoing, side, narrow trenches or trench structures 206b penetrates.

The pore distribution or pore size distribution can be determined, for example, by means of a so-called "mercury porosimetry" or else by means of an SEM analysis (SEM = scanning electron microscope), both procedures providing essentially the same results.

Thus, according to the present approach, the large pores or channels 206a are filled along the contact points of three columns, ie, along the area of adjacent three columns, while the liquefied metal material enters the "narrow" trenches between the columns (between two adjacent columns). would occur only at a higher pressure level. Thus, the conductive electrode structure 208 can be targeted into the channels 206a in the designated areas 208-n are introduced, ie in the for the conductive electrode structure 208 in the piezoelectric layer 202 intended areas 208-n through the mask structure 214 be introduced through.

In the introduction of the conductive electrode structure 208 For example, by infiltrating metal electrodes by means of high pressure, a low-temperature metal, for example gallium indium, etc., in the channels or pores, which is not by the masking 214 are closed, introduced or pressed. As already stated, instead of a conventional photoresist for the mask structure 214 For example, find a sputtered PET structure application, for example, in the piezoelectric layer 202 Liquefied metal material to be introduced less adhered.

It should also be noted in this connection that, in principle, other liquid metals or solders than gallium or indium can be used if the liquefaction temperatures of these metal materials are below about 500 ° C. or 350 ° C. For example, gallium has a very low melting point of 29.76 ° C.

As suitable materials for the metallization is, for example, at low temperatures liquefiable metal or metal alloy materials, on the one hand as little as possible gap-like, ie there is a negative capillary pressure (back pressure) within the narrow trenches 206b on the other hand, the metal material is reactive so that it remains adhered to the piezoelectric layers (PZT surfaces) after wetting of the oxidic surface. Metal materials such as indium and gallium meet these requirements, although tin solders can be used with additional reactive admixtures.

As an alternative or in addition to the above-described method step of introducing a metallization by means of a liquefied metal material under pressure, the conductive electrode structure may also be used 208 be introduced into the piezoelectric layer by means of an ALD (Atomic Layer Deposition) process. In this case, by means of the ALD process, a thin electrically conductive layer at least into a plurality of the channels, which are exposed through the mask structure, as the conductive electrode structure 208 in the piezoelectric layer 202 be introduced. As an alternative or in addition to the pressing in of metal materials under pressure, an electrically conductive oxide, for example doped ZnO, or a metal, for example ruthenium, can also be introduced into the mask structure by means of an ALD process 214 exposed spaces 206 (Pores), ie channels and / or trenches are introduced.

At step 130 also becomes the insulating material 210 in interspaces 206 in the piezoelectric layer 200 introduced to mechanically couple adjacent columns at least partially with each other. This penetration of the insulation material 210 can be introduced, for example, by means of a (further) ALD process, wherein the insulating material at least partially into the (remaining) spaces 206 in the piezoelectric layer 202 is introduced to (at least in sections) to obtain a lateral coupling of the columnar structure, ie, a lateral mechanical or non-positive coupling of the means of the insulating material 210 mechanically coupled to each other columns of the layer structure 202 , The lateral coupling of the PZT columns can thus take place by means of a (further) ALD process in order to achieve a sufficiently high, lateral cohesion of the columnar layer structure of the piezoelectric layer (of the PCT film) 202.

The columnar structure of the piezoelectric layer (of the PZT film) 202 thus enables not only a low-stress deposition of the thick piezoelectric layer 202 and the infiltration of the individual vertical electrode elements 208-n ie the conductive electrode structure 208 in the piezoelectric layer 202 , also the introduction of the insulation material 210 for mechanically coupling the columns 204 , In order to enable the construction in practice usable lateral actuators (piezoelectric stack actuators), in the above-described step 130 sufficient cohesion or mechanical coupling of the PZT columns by the infiltration of an insulating material, such as ALD layers with a TiO ₂ - or Al ₂ O ₃ material can be effected. This additional introduced insulating material in the columnar layer structure of the piezoelectric layer 202 also increases the (electrical) insulation and thus the electrical breakdown strength of the entire system.

The extreme fissuring of ALD layers, which, for example, allows coating of structures with aspect ratios (height-to-width ratios) of, for example, up to 25,000: 1, leads to intimate (strong) mechanical coupling of the columns and thus to a solid ceramic bond in the piezoelectric layer 202 , This can ensure that the piezoelectric layer 202 can significantly expand with the introduced in the interstices insulation material in an activation (energization) in the layer plane and the deformation of the functional layer (ie, the piezoelectric layer 202 ) to a layer-substrate composite when the piezoelectric layer 202 is arranged on a substrate.

If this happens at step 130 in the interstices of the piezoelectric layer 202 introduced insulation material 210 also on the in the piezoelectric layer 202 introduced conductive electrode structure 208 can, after the step 130 the introduction of the insulation material 210 that insulation material 210 partially from the conductive electrode structure 208 be removed, attached to the surface area 202a the piezoelectric layer 202 on or above the conductive structure 208 located. This removal step can be carried out, for example, by means of plasma etching. Following the introduction 130 of the insulation material 210 For example, by means of an ALD process, that is, in the area that reaches the surface 202a reaching metal electrodes 208 , the applied insulation material 210 ie, the ALD layer removed, for example by plasma etching, around the electrode structure 208 at least on the surface area 202a expose.

Using the ALD process can therefore be done using non-conductive materials 210 , such as alumina (Al ₂ O ₃ ) or titanium oxide (TiO ₂ ), an (improved) mechanical coupling of the columns 204 to be obtained. The introduced by the ALD process, non-conductive material can thus to a "gluing" (mechanical coupling) of the columns 204 in the piezoelectric layer 202 lead by the still exposed spaces or pores 206 filled with the non-conductive material. The non-conductive material introduced by the ALD process 210 Thus, it can be provided in order to avoid the remaining gaps that are still present 206 as far as possible to fill up the intermediate spaces not filled by the resolidified solder material, in order to mechanically couple the columnar piezoelectric layer 202 to obtain. Since the ALD process is extremely "gap-like", the non-conductive material can be very (or extremely) compliant even in very small spaces 206 ie channels 206a and / or trenches 206b , the piezoelectric layer 202 be introduced. The applied or introduced by the ALD process non-conductive material can relatively stress-free, ie without mechanical stresses on the piezoelectric material of the piezoelectric layer 202 be applied. In this regard, it should be noted that the applied, non-conductive material 210 of the ALD process at least in the areas of the piezoelectric material 202 introduced electrode structure 208 with the electrode elements 208-n to remove when applying the metallization structure 212 the electrical contact between the metallization structure 212 and the electrode structure 208 with the electrode elements 208-n to obtain.

As above at step 140 is specified, the metallization structure 212 at the surface area 202a the piezoelectric layer 202 in electrical contact with the conductive electrode structure 208 applied and arranged. The applied metallization structure 212 can have a so-called "interdigital structure".

The control of the entire stack, ie the piezoelectric Stapelaktuators 200 , finally, may be from a signal source having a relatively low control voltage V _P (eg in a range of 10 V or between 5 and 15 V) via this metallization structure or interdigital structure 212 respectively. The resulting strain ΔS can then be used either directly when the piezoelectric layer 202 is released, ie from the substrate 203 mechanically decoupled or removed, or it can be generated in a bimorph arrangement, for example, a strong bend when the piezoelectric layer 202 with the substrate 203 mechanically firmly coupled.

The realization of the lateral stack actuator 200 can thus be done in several forms. So on the one hand, the piezoelectric layer (PZT layer) 202 on a (thinned) substrate 203 be effective or used as a bimorph bending element. On the other hand, the piezoelectric layer 202 also from the substrate 203 be solved and designed as a self-supporting membrane with a very large stroke ΔS and operated. Thus, the piezoelectric layer of the resulting piezoelectric stack actuator 200 be designed for the deflection, for example, a membrane or a sound transducer membrane.

The following will now be based on the 2 a piezoelectric stack actuator 200 described according to an embodiment.

The piezoelectric stack actuator 200 includes a piezoelectric layer 202 having a columnar layer structure, wherein due to the columnar layer structure starting from a surface region 202a the piezoelectric layer 202 interspaces 206 with channels 206a and ditches 206b between adjacent columns 204 in the piezoelectric layer 202 are formed. A conductive electrode structure 208 is in the piezoelectric layer 202 arranged, wherein the conductive electrode structure 208 starting from the surface area 202a the piezoelectric layer 202 vertically (in -y direction) into a plurality of channels 206a the piezoelectric layer 202 extends. An insulation material 210 is at least partially in remaining spaces 206 in the piezoelectric layer 202 arranged to adjacent columns 204 at least partially mechanically coupled or connect to each other. A metallization structure 212 is at the surface area 202a the piezoelectric layer 202 in electrical contact with the conductive electrode structure 208 in the piezoelectric layer 202 arranged.

The piezoelectric layer 202 has a PZT material (PZT = lead zikonate titanate), wherein the piezoelectric layer 202 may be anisotropic and columnar, and has a layer thickness between 5 and 50 microns or between 15 and 35 microns. The gaps 206b between adjacent columns 204 At least 80% or 90% of the liquefied metal material is kept free. The insulation material 210 is at least partially in the interstices 206 in the piezoelectric layer 202 introduced to obtain a lateral coupling of the columnar layer structure. The piezoelectric stack structure is a piezoelectric stack actuator 200 educated.

The stack structure may be on a (thinned) substrate 203 be applied to be effective as a bimorph bending element, as exemplified in 2 is shown.

As in the exemplary perspective view of the piezoelectric stack actuator 200 from 2 is shown has the electrode structure 208 a so-called "interdigital structure" with the finger-like structures 208-n the electrode structure 208 on. To the electrode structure 208 can now via the metallization structure 212 , for example, between the terminal electrodes 212a . 212b the metallization structure 212 by means of a voltage source 214 a potential V _{P be} applied, the resulting electric field within the piezoelectric layer 202 a deflection .DELTA.S (elongation or contraction) along the longitudinal direction (see x-direction of the coordinate system at 2 ) causes. Is the piezoelectric layer 202 Now, for example, firmly with the substrate 203 connected, this lateral deflection of the piezoelectric layer 202 (in operation) converted into a curvature or deflection in the y direction.

In a so-called "bimorph arrangement", the piezoelectric stack is arranged laterally on a bending beam (cantilever) or a deflectable membrane, so that an electrical activation of the piezoelectric stack actuator as actuator movement causes a deflection of the bending beam or the membrane.

Alternatively (not shown in FIG 2 ), the piezoelectric stack structure 200 also from the substrate 203 be solved and as a self-supporting membrane with a large stroke ΔS (parallel / along the x-direction of 2 ) are trained and operated. The piezoelectric stack structure 200 can be designed for the deflection of a membrane or a Schallwandlermembran.

The following is based on the 3A-C the term "columnar" or "columnar" layer structure of the piezoelectric layer (PZT layer) used in the present specification 202 explained in more detail.

3A shows by way of example a cross-sectional view (a fracture) through an eg 25 μm thick piezoelectric layer (PZT-layer) 202 , for example, by means of a GFS process on a substrate 203 was applied. As in 3A it can be seen has the piezoelectric layer 202 a pronounced columnar structure. This is how the individual columns extend 204 from the surface area 202a the piezoelectric layer up to its bottom area 202b , As in 3A As can be seen, a majority, at least 70% of the columns 204 to a depth D2 of the piezoelectric layer 202 which is at least 80% of the total thickness D1 of the piezoelectric layer 202 is. A proportion of the columns 204 can be up to the bottom area 202b ie, to the substrate 203 rich, with at least a portion of the columns 204 also in the ground area 202b Already due to the respective manufacturing process (cohesively) connected to each other or can be formed as a coherent composite material. The columnar layer structure may be, for example, starting from the surface area 202a to a depth of D2 ≥ 0.8 D1 (or between 80% and 90% of the thickness D1) in the layer 202 extend so that it can be ensured that the conductive electrode structure 208 sufficiently deep, ie at least to a depth D2 or completely, in the piezoelectric layer 202 can be introduced. The ratio between the thickness D2 of the columnar layer structure and the total thickness D1 of the piezoelectric layer 202 depends on the process parameters (deposition parameters) of the manufacturing process of the piezoelectric layer 202 and can therefore be adjusted within certain limits as needed.

To as uniform a high and high deflection of the piezoelectric layer 202 possibly over the entire thickness D1, the conductive electrode structure 208 may "ideally" into the entire piezoelectric layer 202 are introduced, ie substantially vertically through the entire thickness D1 (or at least 80%, 85%, 90% or 95%) through the piezoelectric layer 202 extend.

Typical dimensions of the piezoelectric layer 202 may be in the following ranges depending on the selected deposition parameters. For example, the columns 204 the piezoelectric layer 202 have a (mean) diameter of 10 - 30 nm. A typical layer thickness D1 of the piezoelectric layer 202 is in a range of 20 microns ± 10 microns, while the thickness of the columnar layer structure D2 is in a range of 80% to 90% and 80% to 85% of the total thickness D1. Thus, a base layer with a layer thickness D3 in a range of 1 - 2 microns are present. As the base layer, the area of the piezoelectric layer becomes 202 denotes, in the no (usable) spaces 206 with channels 206a and ditches 206b in the piezoelectric layer 202 available.

3B shows an exemplary plan view of a portion of a (eg obliquely ground) piezoelectric layer 202 (PZT layer) with the intercolumnar spaces or pores 206 , with the channels 206a and the trenches 206b between adjacent columns 204 , In the partial top view of 3B is only one column at a time 204 and only one channel 206a and a ditch 206b (Of a variety of these elements) exemplified by a reference numeral.

As seen from the top view of 3B a portion of the piezoelectric layer 202 it can be seen, the individual columns (PZT columns) 204 , ie two laterally adjacent columns 204 through relatively narrow trenches 206b separated from each other. At the locations in the piezoelectric substrate 202 in which three columns (columns) 204 coincide, opens or forms a vertical channel 206a with a significantly larger diameter or a significantly larger width than the narrower trenches 206b between two adjacent columns 204 , The channels 206a extend for example over a depth D2 of up to 80% of the layer thickness D1 in the material of the piezoelectric layer 202 ,

The channels 206a Thus, substantially vertically form in the piezoelectric layer 202 at positions at which three columns 204 are adjacent or meet. As channels 206a In the context of the present description, those areas between adjacent columns are referred to whose cross-sectional area (iW parallel to the surface area 202a ) of the following length (L) -to-width (B) relationship is sufficient: $$\text{L}\approx \text{n}*\text{B}\text{, With}0.3\le \text{n}\le \text{3}\text{,}$$

The channels 206a For example, they may have a diameter or a width of 20 to 30 nm.

The areas 206b form between two adjacent columns 204 out, with the trenches 206b have a smaller width than the channels, with respect to the length (L) -to-width (B) ratio of the trenches 206b the following assumption applies: $$\text{L >> B}\text{, with L> m}*\text{B and m> 3 resp}\text{, m}\ge \text{10}\text{,}$$

An exemplary value for the width B of a trench is in the range of 1 to 5 nm.

Like the diagram in 3C clarified, the example in the 3A and 3B shown piezoelectric layer 202 have a majority pore size of 10 to 50 nm and a cumulative pore volume of 4.5 mm ³ / g. These exemplary values can be determined by a mercury porosimetry measurement. In a mercury porosimetry measurement, liquid mercury is injected into the pore structure. However, mercury, unlike liquid gallium, does not remain in the pores after release of pressure 206 ,

The (thick) columnar piezoelectric layers (PZT layers) 202 can be made with a thickness D1 in a range of 5 microns to 25 microns (or even thicker), for example by means of a GFS process, with GFS processes for PVD (PVD = Physical Vapor Deposition) have a relatively high deposition rate and the pronounced columnar ( columnar) microstructure of the deposited piezoelectric layer 202 result. The tightness and character of the columnar structure can be influenced by the process temperature and the use of a separately controlled ion bombardment.

The present concept further allows the use of these columnar piezoelectric layers for integration in piezoelectric devices, such as lateral piezoelectric stack actuators. Lateral piezoelectric stacking arrangements for the construction of actuators allow the required slender and high piezoelectric structures with aspect ratios (height-to-width ratio) of at least 5: 1, which can not be realized with conventional thin-film methods, eg etching processes, the present concept Furthermore, a (nearly) complete filling with the electrode material allows, further comprising a sufficiently high mechanical coupling between the different layers of the lateral piezoelectric stack actuator 200 is guaranteed.

The introduction of the conductive electrode structure 208 in the columnar layer structure of the piezoelectric layer 202 according to the present concept (vertically) along the layer thickness in the narrow gaps (channels) between the piezoelectric columns (PZT columns), while at the same time avoiding lateral gripping of the liquefied electrode material upon introduction of the same (iW) to an electrical contact between adjacent (electrically separated) electrode structure sections or electrode structure elements. In addition, the inventive concept in addition to the electrical contacting allows the realization of the mechanical coupling within the piezoelectric layer material, so that the execution of the overall system, ie the lateral piezoelectric Stapelaktuators 200 , as a bending element or membrane is possible.

The present concept thus enables the realization of lateral piezoelectric stack actuators 200 with a very high efficiency and relatively low production costs (eg production costs) for loudspeaker applications, an extremely high precision and repeat accuracy for applications in adaptive optics (eg EUV lithography - EUV = extreme ultraviolet), and also allows a very high efficiency and very low Drive voltages, eg for hearing aid applications etc. The advantages of an increased PZT proportion can therefore be used efficiently in the form of multi-layer abutments including their drive electrodes.

The GFS process is a sputtering process which, in principle, is operated at a comparatively high process pressure of 10 to 500 Pa. The high pressure and the associated low mean free path allow columnar (columnar) layers with pronounced porosity. In contrast to evaporation methods, however, column and porosity parameters can be specifically controlled by the acceleration of ions by means of a bias voltage.

The previous description has a new concept for lateral piezoelectric stack actuators 200 and their production process 100 presented.

The illustrated concept for lateral piezoelectric stack actuators 200 and their method of manufacture allows the construction of multilayer lateral piezoelectric stack actuators, which have high performance and efficiency and can be operated with relative piezoelectric voltages of, for example, below 20V. Thus, technical solutions can be considered for a variety of applications that could previously not be considered in the field of piezoelectric actuators.

In the following, some possible fields of application of the present lateral piezoelectric stack actuators are described, wherein the following representation is not to be regarded as conclusive, since the lateral piezoelectric stack actuators according to the invention can be used in a multiplicity of applications.

A possible application of the lateral piezoelectric stack actuators 200 lies in the field of speakers for mobile phones and tablet computers. Today, the market is dominated by loudspeakers, which are built up electromagnetically according to the plunger coil principle. The disadvantage, however, is their extremely low acoustic efficiency, which is below 1 ‰. This makes the loudspeakers but one of the major consumers in the mobile phone. Conventional loudspeakers using conventional piezoelectric ceramics are limited to the high frequency range (piezo tweeter) due to low strokes (deflections) in which the achievable acceleration of the diaphragm is more important than its deflection. A miniaturized mechanical translation can significantly increase the achievable stroke and the shift the usable frequency range significantly towards lower frequencies, but at the expense of the achievable forces or sound levels.

The lateral piezoelectric stack actuators 200 on the other hand, powerful stacked piezoelectric microactuators provide the necessary speaker excursion and forces to operate the diaphragm at drive voltages below 20V. In addition, sound optimization on the mobile telephone can be achieved by using a plurality of these miniaturized loudspeakers through an ultra-compact design.

As further fields of application for the lateral piezoelectric stack actuators 200 According to the present concept, for example, in extremely compact piezoelectric transformers, fiber optic circuits, adaptive mirrors, arrays of high-frequency piezoelectric ultrasonic transducers, eg in frequency ranges greater than 25 MHz, loudspeakers for particularly low drive voltages in implantable hearing aids (eg less than 1.3 V) or at very fast deflection mirrors for laser material processing or laser therapy.

Although some aspects have been described in the context of a device, it will be understood that these aspects also constitute a description of the corresponding method, so that a block or a component of a device is also to be understood as a corresponding method step or as a feature of a method step. Similarly, aspects described in connection with or as a method step also represent a description of a corresponding block or detail or feature of a corresponding device.

The embodiments described above are merely illustrative of the principles of the present invention. It will be understood that modifications and variations of the arrangements and details described herein will be apparent to others of ordinary skill in the art. Therefore, it is intended that the invention be limited only by the scope of the appended claims and not by the specific details presented in the description and explanation of the embodiments herein.

References:

• [1] D. Baima, A. Mazzalai, N. Chidambaram, CS Sandu, A. Neels, A. Dammann, P. Hess, D. Binz, P. Muralt: "High Piezoelectric Longitudinal Coefficients in Sol-gel PZT Thin Film Multilayers", Journal of the American Ceramic Society 97. 7 (2014), 2069
• [2] F. Gao, S. Arpiainen, LR Puurunen: "Microscopic silicon-based lateral high-aspect-ratio structures for thin film conformity analysis", J. Vac. Sci. Technol. A, 33-1 (2015), 010601-1
• [3] D. Kaden, D. Koeßler, J. Sichelschmidt, A. Jakob, B. Wagner, T. Jung, F. Tiefensee: "Production and integration of piezoelectric Pb (Zr _x Ti _1-x ) O ₃ layers of extraordinary thickness for the development of new fields of application", MikroSystemTechnik-Kongress 2015, 26.10. - 28.10.2015, Karlsruhe, Germany, Proceedings: MikroSystemTechnik Congress 2015
• [4] K. Ortner, D. Koessler, T. Jung, H. Jacobsen, H.-J. Quenzer: "Influence of Bias Voltage on the Structure of Lead Zirconate titanate Piezoelectric Films Prepared by Gas Flow Sputtering", Plasma Process. Polym. 4 ( 2007 ), S134
• [5] N. Rosemann, K. Ortner, J. Petersen, T. Schadow, M. Baker, G. Brauer, J. Rosier: "Influence of bias voltage and oxygen flow rate on morphology and crystallographic properties of gas flow sputtered zirconia Coatings ", Surface & Coatings Technology 276 ( 2015 ), 668
• [6] R. Sano, J. Inoue, K. Kanda, T. Fujita, K. Maenaka: "Fabrication of multilayer Pb (Zr, Ti) O ₃ thin film by sputtering deposition for MEMS actuator applications", Japanese Journal of Applied Physics 54.1 OS (2015) , 1 OND03-1
• [8] F. Tiefensee, D. Kaden, A. Jakob, H.-J. Quenzer, Th. Jung: "Gas Flow Sputtered Thick Layers of Columnar Lead Zirconate Titanate on Silicon Wafers for High Frequency Ultrasound Transducers", Physics Procedia, 70 2015 ), 957
• [9] US 2012 091 862 A1
• [10] US 2010 013 359 A1
• [11] DE 10 2006 022 600 B4
• [12] US 5 597 494 A

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 2012091862 A1 [0091]
• US 2010013359 A1 [0091]
• DE 102006022600 B4 [0091]
• US 5597494A [0091]

Cited non-patent literature

• D. Baima, A. Mazzalai, N. Chidambaram, CS Sandu, A. Neels, A. Dammann, P. Hess, D. Binz, P. Muralt: "High Piezoelectric Longitudinal Coefficients in Sol-gel PZT Thin Film Multilayers", Journal of the American Ceramic Society 97. 7 (2014), 2069 [0091]
• F. Gao, S. Arpiainen, L.R. Puurunen: "Microscopic silicon-based lateral high-aspect-ratio structures for thin film conformity analysis", J. Vac. Sci. Technol. A, 33-1 (2015), 010601-1 [0091]
• D. Kaden, D. Koeßler, J. Sichelschmidt, A. Jakob, B. Wagner, T. Jung, F. Tiefensee: "Production and integration of piezoelectric Pb (Zr _x Ti _1-x ) O ₃ layers of extraordinary thickness for the development of new fields of application", MikroSystemTechnik-Kongress 2015, 26.10. - 28.10.2015, Karlsruhe, Germany, Proceedings: MikroSystemTechnik Congress 2015 [0091]
• R. Sano, J. Inoue, K. Kanda, T. Fujita, K. Maenaka: "Fabrication of multilayer Pb (Zr, Ti) O ₃ thin film by sputtering deposition for MEMS actuator applications", Japanese Journal of Applied Physics 54.1 OS (2015) [0091]

Claims (20)

Method (100) for producing a piezoelectric stack actuator (200), comprising the following steps: Providing (110) a piezoelectric layer (202) having a columnar layer structure, wherein, due to the columnar layer structure, starting from a surface region (202a) of the piezoelectric layer (202) interspaces (206) with channels (206a) and trenches (206b) between adjacent columns (204) are formed in the piezoelectric layer (202); Introducing (120) a conductive electrode structure (208) into the piezoelectric layer (202), the conductive electrode structure (208) starting from the surface region (202a) of the piezoelectric layer (202) into channels (206a) of the piezoelectric layer (202) extends; Inserting (130) an insulating material (210) into spaces (206) in the piezoelectric layer (202) to mechanically couple adjacent columns (204) at least in regions; and Arranging (140) a metallization structure (212) on the surface region (202a) of the piezoelectric layer (202) in electrical contact with the conductive electrode structure (208). Method according to Claim 1 further comprising the step of: depositing the piezoelectric layer (202) by a gas flow sputtering process (GFS process), wherein the piezoelectric layer (202) comprises a PZT (PZT = lead zirconate titanate) material, and wherein the piezoelectric layer Layer (202) is formed anisotropic and columnar, and has a layer thickness between 5 and 50 microns. Method according to Claim 1 or 2 further comprising the steps of: planarizing the surface area (202a) of the deposited piezoelectric layer (202); Depositing a mask structure (214) on the planarized surface region (202a) of the piezoelectric layer (202), wherein the regions (202-1, 202-2) provided for the conductive electrode structure (208) in the piezoelectric layer (202) pass through the mask structure (214) are exposed through; Inserting the conductive electrode structure (208) into regions (202-1, 202-2) of the piezoelectric layer (202) not covered by the mask structure (214); and removing the mask pattern (214) from the surface area (202a). Method according to one of the preceding claims, further comprising the following step: Introducing the conductive electrode structure into the piezoelectric layer (202), wherein a liquefied metal material is introduced by applying pressure to at least a majority of the channels (206a) of the piezoelectric layer (202) exposed by the mask structure (214). Method according to Claim 4 wherein the metal material, the temperature of the liquefied metal material upon insertion into the piezoelectric layer (202), and the applied pressure on the liquefied metal material are selected to fill a plurality of the channels exposed through the mask structure (214) and further between adjacent ones Columns (204) formed spaces not or on average not more than 20% to fill. Method according to one of Claims 1 to 3 further comprising the step of: introducing the conductive electrode structure (208) into the piezoelectric layer (202) by means of an ALD (Atomic Layer Deposition) process. Method according to Claim 6 wherein, by the ALD process, an electrically conductive layer is introduced as at least a plurality of the channels (206a) exposed through the mask pattern (214) as the conductive electrode structure (208). Method according to one of the preceding claims, further comprising the following step: Introducing the insulating material (210) by means of an ALD process at least partially into the (remaining) intermediate spaces (206) in the piezoelectric layer (202) in order at least partially to obtain a lateral coupling of the columnar layer structure. Method according to one of the preceding claims, further comprising the following step: Removing the insulating material (210) at least in regions from the conductive electrode structure (208) at the surface region (202a) of the piezoelectric layer (202). A method according to any one of the preceding claims, wherein the piezoelectric layer is deposited on a substrate to be effective as a bimorph bending element. The method of any one of the preceding claims, wherein the piezoelectric layer (202) is formed as a cantilevered membrane. Method according to one of the preceding claims, wherein the piezoelectric layer for the deflection of a membrane or a Schallwandlermembran is formed. Lateral piezoelectric stack actuator (200), having the following features: a piezoelectric layer (202) having a columnar layer structure, wherein, due to the columnar layer structure, starting from a surface region (202a) of the piezoelectric layer (202) there are spaces (206) with channels (206a) and trenches (206b) between adjacent columns (204 ) are formed in the piezoelectric layer (202); a conductive electrode structure (208) in the piezoelectric layer (202), the conductive electrode structure (208) extending vertically from the surface region (202a) of the piezoelectric layer (202) into a plurality of the channels (206a) of the piezoelectric layer (202). extends; an insulating material (210) at least in regions in remaining intermediate spaces (206) in the piezoelectric layer (202) in order to at least partially mechanically connect / connect adjacent columns (204) with each other, a metallization structure (208) on the surface region (202a) of the piezoelectric layer (202) in electrical contact with the conductive electrode structure (208) in the piezoelectric layer (202). Piezoelectric stack structure according to Claim 13 wherein the piezoelectric layer (202) comprises a PZT material (PZT = lead zikonate titanate), and wherein the piezoelectric layer (202) is anisotropic and columnar in shape, and has a layer thickness between 5 and 50 μm. Piezoelectric stack structure according to Claim 13 or 14 wherein the interspaces (206) between adjacent columns (204) are at least 80% free of the liquefied metal material. Piezoelectric stack structure according to one of Claims 13 to 15 in that the insulating material (210) is introduced at least in regions in the intermediate spaces (206) in the piezoelectric layer (202) in order to obtain a lateral coupling of the columnar layer structure. Piezoelectric stack structure according to one of Claims 13 to 16 wherein the piezoelectric stack structure is formed as a piezoelectric stack actuator (200). Piezoelectric stack structure according to one of Claims 13 to 17 wherein the stacking structure (200) is mounted on a (thinned) substrate (203) and acts as a bimorph bending element. Piezoelectric stack structure according to one of Claims 13 to 17 wherein the piezoelectric stack structure (200) is formed as a cantilevered membrane. Piezoelectric stack structure according to one of Claims 13 to 19 , wherein the piezoelectric stack structure is designed for the deflection of a membrane or a Schallwandlermembran.

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