Device for applying a material to a target substrate, method for using such a device and method for producing such a device

Abstract

The device for applying a material to a substrate comprises a source substrate with at least one recess for receiving the material and at least one heating element. The heating element at least partially covers at least a bottom region and / or side surfaces of the recess. The heating element is electrically conductively connected to an electrical power supply. Each recess is assigned exactly one heating element. Using the device, a structure for a micro-LED can be printed.

Description

An apparatus is provided, in particular an apparatus for applying a material to a target substrate. Furthermore, a method for using such a device and a method for producing such a device are specified.One object to be achieved is, inter alia, to specify a device by means of which a multiplicity of different materials can be applied to a target substrate in preferably small structures. Further objects to be achieved are, inter alia, to specify a method for operating such a device and a method for producing such a device.These objects are achieved by a device having the features of independent claim 1 and by methods having the features of claims 12 and 16, respectively. Advantageous embodiments and developments are the subject matter of the respective dependent patent claims.According to at least one embodiment, the device has a source substrate with at least one recess. The recess is in particular configured to receive a material which is to be transferred from the source substrate to a target substrate. The material is, for example, an electrically insulating or an electrically conductive material.The material is, for example, a paste and can be introduced into the recess by means of doctor blades. In this case, the material can be cured in particular. That is to say that after the application to the target substrate, the material can be cured and solidified, for example, by means of thermal or chemical processes.The material can be applied in particular in a structured manner to the target substrate. This means in particular that after application to the target substrate, further structuring of the material is not necessary. For this purpose, a geometric shape and / or a number of the recesses from which the material is removed is preferably predefined accordingly.For example, the material is a solder paste with which structured electrical solder connections can be produced on the target substrate. For example, an optoelectronic semiconductor chip can subsequently be electrically connected to the target substrate by means of the structures produced on the target substrate.Alternatively, the material can be, for example, a dielectric material with which structured passivation layers or other electrically insulating layers can be arranged on the target substrate.The source substrate is preferably formed with electrically insulating materials. The source substrate is preferably formed with a material which is comparatively poorly thermally conductive. For example, the source substrate comprises glass and / or dielectric materials such as silicon oxide.According to at least one embodiment, the device comprises at least one heating element. The heating element is formed in particular with a metal and can be heated by means of an electric current. For this purpose, the heating element preferably has a comparatively high electrical resistance. Preferably, a current density in the heating element is comparatively high. For example, the heating element comprises platinum or is formed therefrom.According to at least one embodiment of the device, the heating element at least partially covers at least one base region and / or side surfaces of the recesses. The base region of the recess is, for example, a surface within the recess which is formed parallel to a main extension plane of the device. Side surfaces of the recess are, for example, surfaces within the recess that run transversely or perpendicularly to the base region. "Covered" here and below means in particular that, in view of the recess, the base surface and / or the side surfaces are at least partially covered by the heating element. It is furthermore possible for further layers or elements to be arranged between the heating element and the base region or the side surfaces of the recess.It is possible that the base region is completely covered by the heating element. Alternatively or additionally, it is possible for the side surfaces to be completely covered by the heating element.During operation of the device, the material in the recess can directly adjoin the heating element. Alternatively, it is possible for at least one further layer to be arranged between the heating element and the material. The further layer is, for example, a protective layer and / or an anti-stick layer. Preferably, at most three or at most two or exactly one further layer is / are arranged between the heating element and the material in the recess. This allows particularly good heat transfer from the heating element to the material.According to at least one embodiment of the device, the heating element is electrically conductively connected to an electrical power supply. The electrical power supply is, for example, an external electrical power supply. The heating element can be energized and heated by means of the electrical power supply. For example, an electrical connection of the heating element to the external power supply is effected by means of one or more conductor tracks which can be located at least partially within the source substrate.According to at least one embodiment of the device, each recess is assigned exactly one heating element. This means in particular that in the case of a plurality of recesses, the device comprises the same number of heating elements. For example, exactly one heating element can be arranged in each recess. Alternatively, it is also possible for the heating elements to be arranged in a composite of heating elements. In this case, the heating elements may be connected to each other. For example, the heating elements can be present integrally in the composite. A heating element is then formed in particular by a region of the combination of heating elements which is arranged in the associated recess.In at least one embodiment, an apparatus for applying a material to a target substrate comprises a source substrate having at least one recess for receiving the material and at least one heating element. The heating element covers at least partially at least one base region and / or side surfaces of the recess. The heating element is electrically conductively connected to an electrical power supply. Each recess is assigned exactly one heating element.The device described here is based on the following technical considerations. Conventional methods for applying pastes to a target substrate are, for example, screen and stencil printing, jetting and spindle metering techniques, inkjetting, electro-hydrodynamic dispensing (EHD) and ultra-precision dispensing (UPD), aerosol jetting, offset printing, lithographic methods.Further, pastes can be transferred to a target substrate using lasers. Known methods are laser-assisted transfer, also known from English as "laser induced forward transfer (LIFT)", or volume-controlled laser printing, also known from English as "volume-controlled laser printing (VCLP)".In these laser-assisted methods, a cavity is typically formed in a substrate, which cavity is coated with a detachment layer. The detachment layer is heated by laser irradiation, whereby a paste arranged in the cavity vaporizes in a boundary region with respect to the detachment layer. Due to the gas formed thereby, the paste is pressed out of the cavity and can be transferred to a target substrate.In the above-mentioned methods, the paste can conventionally be applied to the target substrate only to a limited extent in small structures. In the case of laser-assisted transfer methods, a comparatively expensive laser source is also necessary, which must also be precisely adjusted. This increases the outlay and the costs, in particular in the case of small structures to be transmitted.The device described here makes use of the concept of providing an in particular electrical heating element in the recess, which heating element can be heated by means of electric current. In other words, Joule heat is generated by the heating element. Due to the heating of the heating element, during operation of the device, a material arranged in the recess can be evaporated in a boundary region with the heating element. As a result, the material can be released from the recess and transferred to the target substrate.Advantageously, a laser source or the like can thus be dispensed with. Optical adjustment can thus be dispensed with. Moreover, current sources for heating elements are typically more favorable than laser sources. Overall, the apparatus described here can reduce the outlay and the costs of transferring material to the target substrate. Moreover, the carry-over can take place relatively quickly, which can further reduce the costs.Furthermore, a plurality of recesses can be introduced into the source substrate, each of which recesses can be assigned a heating element. If these heating elements are individually controlled during operation, predeterminable print patterns can be transmitted quickly and cost-effectively. The device described here can thus advantageously be used flexibly.In the source substrate, the recesses can be formed, for example, comparatively small and flat, in particular by means of etching. This allows for small structures of material on the target substrate after transfer. A depth of the recesses, in particular measured perpendicular to a base region of the recess, is, for example, between 1 μm and 1 mm inclusive, preferably between 2 μm and 20 μm inclusive. A width of the recess, in particular measured parallel to the base region, is, for example, between 1 μm and 10 mm inclusive, preferably between 10 μm and 100 μm inclusive.According to at least one embodiment of the device, the latter further comprises at least one column line and at least one row line. The column line and the row line are electrically conductively connected to one another via the heating element. The column line and the row line are preferably each electrically conductively connected to the electrical power supply. During the intended operation of the device, the heating element can be energized via the column line and row line in order to heat the material in the recess.The column line and row line are formed in particular with a metal such as copper.According to at least one embodiment of the device, it has a plurality of heating elements, a plurality of column lines and a plurality of row lines. In particular, the column lines and the row lines can each be supplied with current independently of one another. Preferably, each of the heating elements is electrically conductively connected to exactly one column line and exactly one row line. At the same time, it is possible for each column line and / or each row line to be connected to a plurality of heating elements.Advantageously, it is thus possible to control and operate each heating element individually and independently of the other heating elements during the intended operation. That is, pixelated transfer of the material from the source substrate to the target substrate is possible. If, for example, a specific predefined number of heating elements is to be activated, so that a specific pattern or a specific structure of the material is to be applied to the substrate, the correspondingly assigned column lines and row lines can be energized. This allows a flexible and variably usable operation of the device described here.According to at least one embodiment, it is possible for the plurality of heating elements to be formed as a continuous layer of a plurality of heating elements in a composite structure. In this case, the composite of heating elements can extend over a plurality of or all of the recesses. In such a case, a pixelated transfer of the material is also possible. A heating element is then in particular a region of the composite which is arranged in an associated recess. A resistance of each heating element must be much higher than a resistance of column and row lines. If during operation only one row of column and row lines is energized, the current flows directly via the smallest resistance, even if the heating element is a continuous layer. Thus, advantageously, pixellated transmission can also take place.If a plurality of pixels are to be supplied with current simultaneously during operation or if leakage currents are to be reduced, it may be advantageous to separate the composite of heating elements into a plurality of heating elements. Advantageously, leakage currents can be reduced for this purpose when the heating elements are energized.According to at least one embodiment of the device, the column lines are formed as parallel first strips and the row lines as parallel second strips. A main extension direction of the first strips is perpendicular to a main extension direction of the second strips. The strips have a uniformly small thickness. The thickness is measured, for example, perpendicular to the main extension direction. The thickness of the first and second strips is, for example, less than 60 μm or less than 40 μm or preferably less than 20 μm.In particular, the first and second strips form a grid, in particular a uniform rectangular grid, in projection onto a plane parallel to the main extension plane of the device. The first and second strips can be arranged in particular in different planes of the device.For example, a recess is arranged in superposition regions of the first and second strips. The superposition regions are arranged, for example, at the nodes of the grid. For example, the first and / or second strips have a cutout in the superposition regions. The first and / or second strips can be embodied as multiple contiguous strips. In the recess, a recess with a heating element is preferably arranged. The heating element electrically conductively connects a specific first strip assigned to the superposition region to a specific second strip assigned to the superposition region.By arranging the column lines and row lines as first and second strips which run perpendicular to one another, what is known as cross matrix actuation of the device is possible.According to at least one embodiment of the device, the source substrate comprises a carrier and an electrical insulator. The electrical insulator is arranged on a first main surface of the carrier. In particular, the at least one column line is arranged between the carrier and the electrical insulator. The recess preferably penetrates the electrical insulator completely. The electrical insulator can also be referred to below as an "insulator". This means in particular that an element is referred to below as an "insulator", it is in particular an electrical insulator, unless otherwise stated.The carrier of the source substrate is preferably formed with an electrically insulating and thermally poorly conductive material. The carrier is formed, for example, with a glass. The insulator is preferably formed with an electrically insulating material. The insulator is formed with, for example, a dielectric material such as silicon oxide. Advantageously, such a dielectric material may be patterned to create the recesses in the insulator.The recess preferably penetrates the insulator completely, so that in particular the recess forms a hole or an opening in the insulator. In particular, the base region of the recess is free of the insulator.The carrier has, for example, a thickness, in particular measured perpendicular to a main extension direction of the device or of the carrier, of less than 500 μm or less than 400 μm.According to at least one embodiment of the device, it further comprises a connection region for connecting the external power supply to the column line and / or row line. In the connection region, the source substrate is free of the insulator. In the connection region, in particular the heating element can be connected to the electrical power supply, for example during operation of the device.In the connection region, for example, the column line and / or row line is accessible. For example, the column line and / or row line can be electrically contacted in the connection region by means of a solder connection.It is possible for the connection region to be arranged in a further recess. In this case, the further recess is preferably free of a heating element and serves, for example, merely for the electrical contacting of the column line and / or row line.According to at least one embodiment of the device, the carrier of the source substrate has a smaller thickness in the connection region than outside the connection region. Advantageously, with a reduced thickness in the connection region, the device can be electrically contacted particularly easily. Advantageously, a relatively complicated and expensive through-connection through the carrier can thus be dispensed with. Likewise, in this case, advantageously no side metallization of the carrier is necessary.According to at least one embodiment of the device, the at least one row line is arranged on a side of the insulator facing away from the first main surface of the carrier. In particular, the insulator terminates flush with the row line in a direction away from the carrier. The side of the insulator facing away from the first main surface of the carrier can also be referred to here and below as the front side of the device or the front side of the source substrate.In particular, the row line is attached to the front side. Viewed from the front, the row line may be accessible. It is also possible that the row line is buried in the insulator and is not freely accessible at the front side.Alternatively or additionally, the electrical insulator can terminate at the connection region in a direction parallel to the first main surface. This means in particular that the insulator can extend from the direction of the recess as far as the connection region.According to at least one embodiment of the device, the at least one row line is arranged on a rear side of the source substrate and is electrically conductively connected to the heating element via a plated-through hole through the source substrate. The rear side of the source substrate is situated in particular opposite the front side. For example, the rear side of the source substrate is formed by a second main surface of the carrier, which second main surface is opposite the first main surface.Alternatively or additionally, it is possible for the column line to be arranged on the rear side of the source substrate. In this case, the column line is also connected to the heating element via vias. Furthermore, in this case, the row lines may be electrically separated from the column lines by means of an electrical insulating layer.By arranging the row line and / or the column line on the rear side of the source substrate, the row line and / or the column line can advantageously be electrically contacted particularly easily.The through-connection is formed, for example, with the same material as the row line and / or column line. In particular, the through-connection comprises copper. A width of the through-connection, in particular measured parallel to the main extension plane of the device, is, for example, at least 30 μm or at least 80 μm and / or at most 100 μm.According to at least one embodiment of the device, the heating element has a first layer and a second layer, which are electrically conductively connected to one another. The first layer at least partially covers the base region of the recess, and the second layer at least partially covers side surfaces of the recess.It is possible, for example, for the column line and / or the row line to have a hole in the region of the base region of the recess. In other words: the base region of the recess is free of the column line and / or row line. The first layer of the heating element is then arranged on the base region, preferably bridging over the hole and being electrically conductively connected to the column line or the row line. The first layer is then electrically conductively connected, in particular directly connected, to the second layer, which at least partially covers the side surfaces of the recess.It is alternatively possible for the first layer and the second layer to be in contact with one another in a planar manner in the base region. In this case, the second layer likewise covers the base region of the recess at least partially.In the production of the device, the first layer is preferably applied to the carrier before the insulator. This application can take place before or after the application of the column lines. Because the first layer is applied before the insulator, the first layer can be structured particularly easily, since there is no complicated structuring within the recesses.The first layer and the second layer are each formed with a metal, for example. For example, the first and second layers each comprise platinum.By comparison, it is possible with a layer structure of the heating element to achieve higher current densities and thus a higher heating of the heating element. In particular in the base region, stronger heating and thus better detachment of the material can be achieved with a two-layer heating element during the intended operation of the device.According to an embodiment of the device, the heating element is at least partially covered by a protective layer. The protective layer is arranged, for example, in the recess. However, it is possible for the protective layer to protrude beyond the recess and to completely or partially cover the front side.The protective layer is formed with, for example, molybdenum, tungsten, silicon oxide, silicon nitride, tungsten carbide, Al2O3, or diamond.The protective layer advantageously makes it possible during operation to protect the heating element during the introduction of the material. Material can be introduced, for example, by means of doctor blades. By means of the protective layer, scratching of the heating element during doctoring can thus be reduced or avoided.Preferably, the protective layer also has anti-sticking properties. The protective layer is, for example, an anti-stick layer. Advantageously, the material can thus be transferred particularly easily to the substrate during operation of the device.Further preferably, the protective layer is formed with an electrically insulating material. An electrical connection between an electrically conductive material, which is to be transferred to the target substrate during operation of the device, and the heating element can thus be avoided.According to at least one embodiment of the device, the source substrate is arranged on a roller. The source substrate has at least one functional unit, which in each case has a plurality of recesses and at least one connection region. Each of the recesses is assigned a heating element. In the connection regions, the functional unit and the heating elements can be electrically contacted or energized, for example by means of a contact needle.In this embodiment, the device can be rotated during the intended operation. The at least one functional unit can be rotated. During the rotation, the recesses of the functional unit can be filled with the material which is to be transferred to the target substrate. For example, a doctor blade can be used for this purpose.Furthermore, the roller is configured to rotate the functional unit further. In this case, the functional unit is preferably arranged and aligned over the target substrate. The alignment can be carried out precisely by means of an adjustment camera. In particular, the material is subsequently applied to the target substrate. For this purpose, the heating elements are energized by means of contact needles.After further rotation, the functional unit can optionally be cleaned and material can be taken up again by further rotation of the roller.It is also possible that the device can be planar, in contrast to a rotating device. In this case, it is not on a roll but on a planar plate or the like. It is possible here for the source substrate to have a plurality of functional units.By arranging one or more functional units each having one or preferably more recesses, the material can be applied to the target substrate in a structured manner during operation. For example, a position of the functional units on the plate can be adapted for this purpose. Advantageously, with such a planar device, a plurality of structures of the material on the target substrate can be produced in a method step in which the material is transferred to the target substrate.Furthermore, the at least one functional unit can be cleaned after application of the material. For this purpose, a cleaning device such as a nozzle and a collecting trough can be provided.For precise positioning of the source substrate with respect to the target substrate, whereby a precise application of the material on the target substrate is made possible, an adjustment camera can be used.In the case of a planar device, the heating elements can advantageously be supplied with current via supply lines during normal operation. That is, application of contact needles or the like is not required.A method for using an apparatus described herein is further described. In particular, the method can be used to use a device described here. That is, all of the features disclosed for the method of using the device are also disclosed for the device and vice versa.The method for using the device comprises a method step in which the material is introduced into the recess. Subsequently, an electric current is applied to the heating element, so that the heating element is heated. Subsequently, the material evaporates in a region adjoining the heating element. In particular, a gas is formed in this case. Subsequently, the material is detached from the source substrate and the material is applied to the target substrate.The electric current is applied, for example, as a current pulse. In particular, the current pulse is applied to the at least one column line and the at least one row line. For example, the recesses or the heating element in the recesses can each have a thermal resistance of 1000 K / W. If such a heating element is to be heated by 100 K during operation, 0.1 W is required in particular for this purpose. For example, if an electrical resistance of the heating element is 1 Ω and an applied voltage is 1 V, the current intensity in the heating element is 0.1 A in the example. The thermal resistance and the electrical resistance can be adjusted by a material selection, material thicknesses and geometries.According to at least one embodiment, the material is introduced into the recess by means of doctor blades. In this case, the material is preferably a paste. The paste can be cured, for example, after application to the target substrate.According to at least one embodiment, the electric current or the current pulse is applied to the heating element by means of at least one contact needle. For example, the contact needle is applied to the column line and / or the row line in a connection region.Alternatively, it is possible for the current source to be firmly connected to the column line and / or the row line. For example, the current source is electrically conductively connected to the column line and / or row line via a solder connection in the connection region.According to at least one embodiment of the method for using the device, the recess is cleaned after the material has been detached from the source substrate. Preferably, the entire source substrate is cleaned. After cleaning, the device may be used again to transfer material from the source substrate to a target substrate.According to at least one embodiment of the method for using the device, a structure for a micro-LED is printed by means of the method.As a broad definition, a micro-LED could be seen as any light emitting diode (abbreviated "LED")-generally not a laser-of particularly small size.As a rule, this is also a very important criterion in addition to size, a growth substrate is removed in the case of micro LEDs, so that typical heights of such micro LEDs are, for example, in the range from 1.5 μm to 10 μm.In principle, a micro LED does not necessarily have to have a rectangular radiation emission surface. In general, an LED could have a radiation emission surface, for example, in which, in a plan view of the layers of the layer stack, each lateral extent of the radiation emission surface is less than or equal to 100 μm or less than or equal to 70 μm.For example, in the case of rectangular micro LEDs, an edge length-in particular in a plan view of the layers of the layer stack-of less than or equal to 70 μm or less than or equal to 50 μm is frequently mentioned as a criterion.Usually, such micro-LEDs are provided on wafers with-for the μLED non-destructively detachable holding structures.At present, primarily displays are considered as applications of micro-LEDs. In this case, the micro-LEDs form pixels or subpixels and emit light of a defined color. Due to the small pixel size and a high density with a small spacing, micro-LEDs are suitable, inter alia, for small monolithic displays for AR applications, in particular smart glasses. In addition, further applications are being used, in particular the application in data communication or even pixelated lighting applications.The literature contains various notation for micro-LEDs, for example μLED, μ LED, μLED, μ LED or micro light emitting diode.A method for producing a device described here is also described. In particular, a device described here can be produced with the method. That is, all of the features disclosed for the method of using the device are also disclosed for the device and vice versa.In at least one embodiment, the method includes patterning a carrier. For example, a connection region is formed in the carrier. Furthermore, it is possible for the carrier to be prepared on a first main surface in order to facilitate further processing of the carrier. For example, the carrier may be roughened on the first main surface.Subsequently, at least one column line is applied to the first main surface of the carrier. The column line is deposited, for example. The column line may be patterned to form, for example, first stripes. It is possible for a material of the column line to be deposited first flat on the first main surface of the carrier and subsequently structured to form the at least one column line.Subsequently, an insulator is arranged on a side of the column line facing away from the first main side of the carrier and / or on the first main side of the carrier. The insulator is formed with a dielectric, for example. The insulator is deposited, for example.The insulator is subsequently structured, so that at least one recess is formed. For example, the at least one recess is etched. It is possible that the recess is produced by a lithography method. The recess can be formed particularly flat and / or with a small width. Particularly small structures can thus be transferred from the device to the target substrate.For example, the insulator is completely removed in the region of the recess. In this case, the recess completely penetrates the insulator.Subsequently, at least one heating element is arranged on the base region and / or side surfaces of the recess, so that the heating element is electrically conductively connected to the column line. The heating element is deposited, for example. The heating element can subsequently be structured, for example by means of a lithography method.For example, a material for the heating element is deposited flat on a side of the insulator facing away from the carrier and is subsequently structured. Preferably, after the structuring, each recess is assigned exactly one heating element. In this case, a plurality of column lines are preferably formed. Each of the heating elements is then preferably electrically conductively connected to exactly one column line.Subsequently, at least one row line is applied, so that the heating element is electrically conductively connected to the row line. If a plurality of recesses are formed in the insulator, a plurality of row lines are preferably also formed. In this case, in particular each heating element is electrically conductively connected to exactly one row line.The row line is applied, for example, by means of deposition. For example, a material for the row line is deposited flat and subsequently structured, for example by means of a lithography method.According to at least one embodiment of the method for producing a device, the row line is arranged on a side of the insulator facing away from the first main side of the carrier. For example, a plurality of row lines are applied, which are subsequently structured to form second strips.According to at least one embodiment, the row line is arranged on a second main surface of the carrier opposite the first main surface. Furthermore, a through-connection is formed through the carrier, which connects the row line to the heating element in an electrically conductive manner.Further advantages and advantageous embodiments and refinements of the device described here and the method for using the device and the method for producing the device result from the exemplary embodiments illustrated below in conjunction with schematic drawings. Identical, similar and identically acting elements are provided with the same reference numerals in the figures. The figures and the relative sizes of the elements shown in the figures with respect to one another are not to be regarded as being fundamentally true to scale. Rather, individual elements may be represented with exaggerated size for better representability and / or for better understanding.The following are shown: FIGS. 1 and 2 show schematic views of a device described here according to a first exemplary embodiment, FIGS. 3 to 6 are schematic sectional views of various exemplary embodiments of a device described here, FIGS. 7 to 9 show different method stages of a method for using a device described here according to an exemplary embodiment, FIGS. 10 to 15 show different process stages of a method for producing a device described here according to an exemplary embodiment, FIGS. 16 and 17 show schematic representations of a device described here according to a further exemplary embodiment, FIGS. 18 and 19 show schematic representations of a device described here according to a further exemplary embodiment, FIG. 20 shows a schematic illustration of a device described here according to a further exemplary embodiment.FIG. 1 shows a sectional view of a device 1 described here according to a first exemplary embodiment. The sectional plane is perpendicular to a main extension plane of the device. The device 1 for applying a material to a target substrate according to FIG. 1 comprises a source substrate 2. the source substrate 2 comprises a carrier 21 and an insulator 22. A plurality of recesses 3 are introduced into the insulator 22, which recesses completely penetrate the insulator 22 in a direction perpendicular to the main extension direction of the device 1. The recesses 3 are configured to receive a material 100 to be transferred to a target substrate 200 (FIG. 7 ). In the present exemplary embodiment, the carrier 21 is formed with glass. In the present exemplary embodiment, the insulator 22 is formed with a silicon oxide.A plurality of column lines 5 are arranged between the carrier 21 and the insulator 22. In the sectional view of FIG. 1, the sectional plane runs through one of these column lines 5. In the present exemplary embodiment, the column lines 5 are formed with copper.On a side of the insulator 22 facing away from the carrier 21, which forms a front side 12 of the device 1, row lines 6 are arranged outside the recesses 3. The row lines 6 each have a hole in the region of the recesses 3, in which hole the corresponding recess 3 is exposed. Therefore, in the sectional view of FIG. 1, a row line 6 can be seen on both sides of an associated recess 3. The row lines 6 are preferably formed with the same material as the column lines 5.The column lines 5 and row lines 6 are electrically conductively connected to one another via a plurality of heating elements 4. Each recess 3 is preferably assigned exactly one heating element 4. Each of the heating elements 4 is preferably a metal and in the present exemplary embodiment is formed with platinum. Each heating element 4 preferably connects exactly one column line 5 to a row line 6. The heating elements 4 are in particular designed as a composite, wherein the individual heating elements 4 are connected to one another in a composite.The source substrate 2 further comprises a connection region 7, in which each of the column lines 5 is electrically conductively connected to a power supply 10. For example, each of the column lines 5 is electrically conductively connected to the power supply 10 by a solder 11. In the connection region 7, the carrier 21 has a smaller thickness than outside the connection region 7.It is also possible for the source substrate 2 to comprise a further connection region (not shown) which has substantially the same features as the connection region 7. In the further connection region, the row lines 6 are electrically conductively connected to the power supply 10.FIG. 2 shows the device 1 according to the first exemplary embodiment in a view of the front side 12. Moreover, the device 1 comprises a plurality of row lines 6 arranged in second strips 60. This means in particular that a thickness of the strips 50 / 60, measured perpendicularly to the main direction of extension, is smaller than their length and / or width. The column lines 5 and row lines 6 each have a thickness of 18 μm, for example. The heating elements 4 each have a thickness of 100 nm, for example.The first strips 50 and the second strips 60 form a regular grid in a projection onto the front face 12. The heating elements 4 can therefore be seen in the transition regions 40.Due to the grid-like arrangement of the column lines 5 and row lines 6, exactly one specific heating element 4 or a plurality of specific heating elements 4 can / can be operated in the intended operation by means of the power supply 10 and a targeted actuation of the associated column lines 5 and row lines 6.FIG. 3 shows the device 1 according to a second exemplary embodiment. The second exemplary embodiment differs from the first exemplary embodiment in particular in that the heating element 4 comprises a first layer 41 and a second layer 42. The first layer 41 covers the base region 30 of the recess 3 and the second layer 42 covers the base region 30 and side surfaces 31 of the recess 3 at least partially. The first layer 41 and the second layer 42 are electrically conductively connected to one another in the base region 30. In the present exemplary embodiment, the first layer 41 and the second layer 42 are each formed with platinum.In the region of the recesses 3, the column lines 5 have holes which are bridged by the first layer 41. If a current is applied to the column lines 5 during normal operation, the first layer 41 has a higher current density than the column lines 5.In the production of the device 1, the first layer 41 is preferably applied to the carrier 21 before the insulator 22. This application can take place before or after the application of the column lines 5. Because the first layer 41 is applied in front of the insulator 22, the first layer 41 can be structured particularly easily, since there is no need for complicated structuring within the recesses 3.In further features, the first and second exemplary embodiments substantially correspond.FIG. 4 shows the device 1 according to a third exemplary embodiment. The third embodiment has substantially the same features as the second embodiment, with the difference that the bottom region 30 is substantially free of the second layer 42. The second layer 42 is arranged only at the edge of the base region 30, in order to enable an electrically conductive connection to the first layer 41. In comparison with the second exemplary embodiment, the current density in the base region 30 can thus be further increased; this allows, inter alia, a more homogeneous and more efficient heating of the heating element 4 in the base region 30.FIG. 5 shows the device 1 according to a fourth exemplary embodiment, which differs from the third exemplary embodiment in particular in that the first layer 41 is removed in a central region of the base region 30, such that in this region the base region 30 is substantially covered by the second layer 42. The first layer is arranged only at the edge of the base region 30, in order to enable an electrically conductive connection to the column line 5.An arrangement of the first and second layers 41, 42 of the heating element 4 can be used analogously in all other exemplary embodiments.FIG. 5 further illustrates that, on the front side 12, the insulator 22 terminates flush with the row line 6. That is, outside the recesses 3, the insulator 22 has such a thickness that the row line 6 does not protrude beyond the insulator. The row line 6 can thus be protected from external influences.Furthermore, FIG. 5 illustrates that a heating element 4 is arranged in each recess 3. That is, the heating element 4 is not formed as a continuous composite that extends over a plurality of recesses 3. Each of the heating elements 4 is electrically conductively connected to at least one row line 6 and one column line 5. The device 1 can thus be operated in a pixelated manner, wherein each of the recesses 3 forms a pixel. This means in particular that each recess 3 or each heating element 4 can be controlled and operated individually and independently of the other recesses 3 or heating elements 4. Thus, the material 100 may be selectively deposited on the target substrate 200 in a pattern or the like using the device 1.If a plurality of pixels are to be supplied with current simultaneously during operation or if leakage currents are to be reduced, it may be advantageous to separate a composite of heating elements 4 into a plurality of heating elements 4.A separation of the heating element 4 into a plurality of heating elements 4, wherein a heating element 4 is arranged in each recess 3, so that the heating element 4 does not extend as a continuous element over a plurality or all recesses 3, can be present accordingly in all exemplary embodiments.FIG. 6 shows the device 1 according to a fifth exemplary embodiment. The fifth embodiment has substantially the same features as the fourth embodiment, with the difference that a protective layer 8 is applied to the front side 12. The protective layer 8 is formed, for example, with molybdenum, tungsten, silicon oxide, silicon nitride, tungsten carbide, Al2O3and / or diamond. The protective layer 8 protects the heating element 4 and / or the insulator 22 and / or the line line 6 from damage, for example, such as scratching, when the material 100 is introduced into the recesses 3.The protective layer 8 may also have an anti-sticking effect. That is, the protective layer 8 can reduce adhesion between the material 100 and the source substrate 2 so that it can be more easily released from the recesses 3 and transferred to the target substrate 200.The embodiment of FIG. 6 differs further from the embodiment of FIG. 5 in that the row lines 6 are buried or embedded in the insulator 22. This means in particular that the row lines 6 are not accessible from the outside, in particular from the front side 12.A protective layer 8, as explained in connection with FIG. 6, can also be present in all other exemplary embodiments of the device 1.In the method for using a device 1 described here, in a method step, a material 100 which is to be transferred from the substrate 2 to a target substrate 200 is introduced into recesses 3 of the source substrate 2 (FIG. 7 ). The device 1 is the device 1 of the first exemplary embodiment. In the exemplary embodiment of FIGS. 7 to 9, the material 100 is introduced into the recesses 3 by means of a doctor blade 72.The material 100 is a paste, for example a solder paste. For example, a solder pattern may be applied to the target substrate 200 with the solder paste. For this purpose, the solder paste on the target substrate 200 can be cured or solidified.In a subsequent method step, a current pulse 9, illustrated by the arrows in FIG. 8, is applied via the power supply 10 to the row lines 6 and column lines 5. A resistance of the heating element 4 is preferably much higher than a resistance of the column and row lines 5, 6. If only one pair of column and row lines 5, 6 is energized, the current flows directly via the smallest resistance, even if the heating element 4 is a continuous layer.Due to the current pulse 9 and the resulting current flow through the column lines 5, the row lines 6 and the heating elements 4, the heating elements 4 heat up. During the evaporation, gas forms, which presses the material 100 out of the recesses 3. Thus, the material 100 can be dissolved out of the recesses 3 and transferred to the target substrate 200 (FIG. 9 ).By arranging the column lines 5 and row lines 6 (FIG. 2 ) in the form of a grid, all heating elements 4 can be driven and operated independently of one another and individually. A predefined pattern or a predefined structure of the material 100 can thus be applied on the target substrate 200. For example, an electrical contact structure for a micro LED may be applied to the target substrate 200.In the exemplary embodiment of the method for producing a device 1 described here, a carrier 21 is structured in a first method step (FIG. 10 ). By the method of the exemplary embodiment, in particular a device 1 according to FIG. 1 is produced. The carrier 21 is etched or ground, for example. By structuring the carrier 21, for example, the connection region 7 is defined.In a further method step, the column lines 5 are applied (FIG. 11 ). The material for the column lines 5 is deposited, for example. In particular, the material for the column lines 5 is deposited flat on the carrier 21. After deposition, the material is patterned to the column lines 5, for example, by a lithography method. By structuring the column lines 5, the first strips 50 are produced.In a further method step, the insulator 22 is applied to the carrier 21 (FIG. 12 ). The insulator 22 is preferably applied on the same side as the column lines 5. The material of the insulator 22, which is a dielectric, is deposited and then patterned, for example, by a lithography method. The recesses 3 are produced in the insulator 22 by the structuring.In a further method step, the heating elements 4 are applied to the insulator 22 (FIG. 13 ). The heating elements 4 are applied to a side of the insulator 22 facing away from the carrier 21. The material for the heating elements 4 is preferably deposited flat on this side. Subsequently, the material for the heating elements 4 can be structured, so that the heating elements 4 at least partially cover a base region 30 and side surfaces 31 of a recess 3, respectively. The heating elements 4 are applied in such a way that they are electrically conductively connected to the column lines 5.In a further method step, the row lines 6 are applied to the insulator 22 (FIG. 14 ). The row lines 6 are applied outside the recesses 3 on a side of the insulator 22 facing away from the carrier 21. The row lines 6 are applied in such a way that they are electrically conductively connected to the heating elements 4, with the result that an electrically conductive connection is produced between a respective row line 6 and a column line 5 via each heating element 4.In a further method step, the power supply 10 is electrically connected in the connection region 7. In this case, the power supply 10 is brought into electrical contact with the column lines 5 or the row lines 6 (not shown) via a solder 11. In particular, in this method step, the device 1 according to the first exemplary embodiment (FIGS. 1 and 2 ) is completed.FIG. 16 illustrates an alternative contacting for the row lines 6 in a detailed view; the row lines 6 are arranged on a rear side 13 opposite the front side 12. The row line 6 shown in FIG. 16 is connected to the associated heating element 4 via a through-connection 25. The through-connection 25 is covered by the insulator 22 when viewed from the front side 12. The through-connection 25 connects the rear side 13 to a first main surface 23 of the carrier 21.The carrier 21 has, for example, a thickness, measured between the first main surface 23 and the rear side 13, of 380 μm. The through-connection 25 has, for example, a width of at least 30 μm or 80 μm.At the first main surface 23, the through-connection 25 is electrically connected to the heating element 4. The heating element 4 is guided along the first main surface 23 and extends into the recess 3.Furthermore, the heating element 4 is electrically conductively connected to a column line 5, as illustrated in FIG. 17. FIG. 17 shows a section through the device 1 according to FIG. 16, wherein the sectional plane is the first main surface 23. The column line 5 is arranged, for example, as illustrated in FIGS. 1 to 6.The device according to FIGS. 16 and 17 otherwise has substantially the same features as the device 1 according to the first exemplary embodiment.FIGS. 18 and 19 illustrate a further attractive configuration of the heating elements 4. FIG. 18 shows a sectional view of the device along the first main surface 23 of the carrier 21. In contrast to FIGS. 16 and 17, the recess 3 is not arranged between the column line 5 and the row line 6 along the heating element 4, but rather, viewed on the front side 12, above the column line 5.FIG. 19 is a sectional view taken along the line A-A illustrated in FIG. 18. As can be seen in FIG. 19, the recess 3 extends from the front side 12 as far as the column line 5.FIG. 20 shows a device 1 described here according to a further exemplary embodiment. A source substrate 2 is mounted on a roll 70. The source substrate 2 has a plurality of functional units 77, which are each formed from a plurality of recesses 3, in which heating elements 4 are arranged, and at least two connection regions 7. Each functional unit is configured to apply a current pulse in the connection areas 7, so that at least one of the heating elements 4 can be heated. During normal operation, the recesses 3 can thus be filled with a material 100 which is to be transferred to a target substrate 200. By applying a current pulse 9 to the connection regions 7, the material 100 can be released from the recesses 3 by heating the heating elements 4. That is, an operation of each functional unit is, for example, as explained in connection with FIGS. 1 and 2.During normal operation, the roller 70 rotates along a rotation direction 76 As a result of the rotation of the roller 70, the functional units 77 pass a doctor blade 72, with which the material 100 is introduced into the recesses 3.Subsequently, the roller 70 may be further rotated, and the functional unit 77 filled with the material is positioned over a target substrate 200. By means of an adjustment camera 75, the positioning of the functional unit 77 with respect to the target substrate 200 can be carried out precisely.Subsequently, a current pulse 9 is applied to the functional unit 77 via contact needles 71, whereby the material 100 is transferred to the target substrate 200.The functional unit is subsequently cleaned by means of a cleaning device 74, in particular after a further rotation of the roller 70. The cleaning device 74 comprises, for example, a nozzle with which a cleaning liquid, for example water, can be sprayed onto the source substrate. Residues of the material 100 which are thereby rinsed out of the recesses 3 can be collected in a collecting trough 73.Subsequently, the functional unit 77 may be reused to apply material 100 to the target substrate 200. For this purpose, the functional unit 77 is rotated again to the doctor blade 72.Meanwhile, the target substrate 200 is moved in a feed direction 201 to provide further regions of the target substrate 200 with the material 100.The invention is not limited to the exemplary embodiments by the description on the basis of the exemplary embodiments. Rather, the invention comprises any novel feature and any combination of features, which includes in particular any combination of features in the patent claims, even if this feature or this combination itself is not explicitly stated in the patent claims or exemplary embodiments.List of reference characters1 Device 2 source substrate 3 recess 4 heating element 5 column line 6 row line 7 connection region 8 protective layer 9 current pulse 10 power supply 11 solder 12 front side 13 rear side 20 rear side of the source substrate 21 carrier 22 electrical insulator 23 first main surface of carrier 24 second main surface of carrier 25 through-connection 30 base region of recess 31 side surface of recess 40 superposition region 41 first layer of heating element 42 second layer of heating element 50 first strips 60 second strips 70 roller 71 contact needle 72 doctor blade 73 collecting trough 74 cleaning device 75 alignment camera 76 rotation direction 77 functional unit 100 material 200 target substrate 201 feed direction A-A cut line

Claims

Device (1) for applying a material (100) to a target substrate (200), comprising: - a source substrate (2) having at least one recess (3) for receiving the material (100), and - at least one heating element (4), wherein - the heating element (4) at least partially covers at least one base region (30) and / or side surfaces (31) of the recess (3), - the heating element (4) is electrically conductively connected to an electrical power supply (10), and - exactly one heating element (4) is assigned to each recess (3).Device (1) according to claim 1, further comprising at least one column line (5) and at least one row line (6), wherein - the column line (5) and the row line (6) are electrically conductively connected to one another via the heating element (4), - the column line (5) and the row line (6) are each electrically conductively connected to the electrical power supply (10).Device (1) according to claim 2, comprising a plurality of heating elements (4), a plurality of column lines (5) and a plurality of row lines (6), wherein - the column lines (5) and the row lines (6) can each be supplied with current independently of one another and - each of the heating elements (4) is electrically conductively connected to exactly one of the column lines (5) and exactly one of the row lines (6).Device (1) according to Claim 2 or 3, wherein - the column lines (5) are formed as parallel first strips (50), - the row lines (6) are formed as parallel second strips (60), - a main direction of extent of the first strips (50) is perpendicular to a main direction of extent of the second strips (60).Device (1) according to one of Claims 2 to 4, wherein - the source substrate (2) comprises a carrier (21) and an electrical insulator (22), - the electrical insulator (22) is arranged on a first main surface (23) of the carrier (21), - the at least one column line (5) is arranged between the carrier (21) and the electrical insulator (22), and - the recess (3) completely penetrates the electrical insulator (22).Device (1) according to Claim 5, further comprising a connection region (7) for connecting the electrical power supply (10) to the column line (5) and / or row line (6), wherein the source substrate (2) is free of the electrical insulator (22) in the connection region (7).Device (1) according to one of the preceding claims, wherein a carrier (21) of the source substrate (2) has a smaller thickness in a connection region (7) for connecting the heating element (4) to the electrical power supply (10) than outside the connection region (7).Device (1) according to one of Claims 2 to 7, wherein the at least one row line (6) is arranged on a side of the electrical insulator (22) facing away from the first main surface (23) of the carrier (21), and the electrical insulator (22) terminates flush with the row line (6) in a direction away from the carrier (21).Device (1) according to one of Claims 2 to 7, wherein the at least one row line (6) is arranged on a rear side (20) of the source substrate (2), and the row line (6) is electrically conductively connected to the heating element (4) via a plated-through hole (25) through the source substrate (2).Device (1) according to one of the preceding claims, wherein - the heating element (4) has a first layer (41) and a second layer (42), - the first layer (41) and the second layer (42) are electrically conductively connected to one another, and - the first layer (41) at least partially covers the base region (30) of the recess (3) and the second layer (42) at least partially covers side faces (31) of the recess (3).Device (1) according to any one of the preceding claims, wherein at least the heating element (4) is at least partially covered by a protective layer (8).Device (1) according to one of the preceding claims, wherein - the source substrate (2) is arranged on a roller (70), - the source substrate (2) has at least one functional unit (77), which in each case has a plurality of recesses (3) and at least one connection region (7), - the heating elements (4) which are assigned to the recesses (3) of the functional unit (77) can be electrically contacted in the connection region (7).Method for using a device (1) according to one of the preceding claims for applying a material (100) from a source substrate (2) to a target substrate (200), comprising the following steps: - introducing the material (100) into the recess, - applying an electric current to the heating element (4) such that the heating element (4) is heated, - partially evaporating the material (100) in a region adjoining the heating element (4), - detaching the material (100) from the source substrate (2) and applying the material (100) to the target substrate (200).Method according to claim 13, wherein - the material (100) is introduced into the recesses (3) by means of doctor blades and - the electric current is applied to the heating element (4) by means of at least one contact needle (71).Method according to claim 13 or 14, wherein after the detachment of the material (100) from the source substrate (2) the recess (3) is cleaned.Method according to one of Claims 13 to 15, wherein a structure for a micro-LED is printed by means of the method.Method for producing a device (1) according to one of Claims 2 to 12, comprising the following steps: - structuring a carrier (21), - applying at least one column line (5) on a first main surface (23) of the carrier (21), - applying an electrical insulator (22) on a side of the column line (5) facing away from the first main side (23) of the carrier (21) and / or on the first main side (23) of the carrier (21), - structuring the electrical insulator (22), such that at least one cutout (3) is formed, - arranging at least one heating element (4) on the base region (30) and / or side surfaces (31) of the cutout (3), such that the heating element (4) is electrically conductively connected to the column line (5), - applying at least one row line (6), such that the heating element (4) is electrically conductively connected to the row line (6).Method according to Claim 17, wherein the row line (6) is arranged on a side of the electrical insulator (22) which is remote from the first main side (23) of the carrier (21).Method according to Claim 17, wherein - the row line (6) is arranged on a second main surface (24) of the carrier (21) opposite the first main surface (23), - a plated-through hole (25) is formed through the carrier (21), said plated-through hole electrically conductively connecting the row line (6) to the heating element (4).

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