METHOD

TECHNICAL FIELD

[1] The present disclosure relates to the deposition of source materials on a substrate, as well as to systems, arrangements and methods for depositing materials, e.g. organic materials or inorganic materials, on a substrate. Specifically, embodiments of the present disclosure relate to an evaporator arrangement for evaporating a source material to be deposited on a substrate, and to a deposition system including an evaporator arrangement. The evaporator apparatus may be configured for evaporating an organic material for manufacturing OLED devices in a vacuum deposition system. In particular, the present disclosure relates to an evaporator arrangement, a deposition system, and an evaporation method.

BACKGROUND

[2] Techniques for layer deposition on a substrate include, for example, thermal evaporation, physical vapor deposition (PVD), and chemical vapor deposition (CVD). Coated substrates may be used in several applications and in several technical fields. For instance, coated substrates may be used in the field of organic light emitting diode (OLED) devices. OLEDs can be used in the manufacture of television screens, computer monitors, mobile phones, other hand-held devices, and the like for displaying information. Organic evaporators are a tool for the production of organic light-emitting diodes (OLEDs). OLEDs are a special type of light-emitting diode in which the emissive layer comprises a thin film of certain organic compounds. OLEDs can also be used for general space illumination. The range of colors, brightness, and viewing angles possible with OLED displays is greater than that of traditional LCD displays, because OLED pixels directly emit light and do not need a back light. Therefore, the energy consumption of OLED displays is considerably less than that of traditional LCD displays. Further, the fact that OLEDs can be manufactured onto flexible substrates results in further applications.

[3] There are many challenges encountered in the manufacture of OLED devices. OLED displays or OLED lighting applications may include a stack of several materials, which are for example evaporated in a vacuum system. The organic materials are typically deposited in a predetermined pattern that is defined by a mask. For the fabrication of OLEDs with high efficiency, the co-deposition or co-evaporation of two or more materials, e.g. host and dopant, leading to mixed/doped layers is beneficial. Further, it has to be considered that there are several process conditions for the evaporation of the very sensitive organic materials.

[4] For the evaporation of the source materials to be deposited, an evaporator arrangement such as a crucible may be used. The source material that is to be evaporated is placed in the inner volume of the crucible, e.g. in a solid form, and the crucible is heated for evaporating the material. For example, the source material may be placed as a powder or granulate inside the crucible. However, the use of crucibles includes several drawbacks. For example, it is difficult to ensure proper evaporation of the source material, particularly for a long time. Further, maintaining the source material at elevated temperatures over an extended time may lead to degradation of the sensitive source material, particularly when the source material is an organic material.

[5] During processing, the substrate can be supported on a carrier configured to hold the substrate in alignment with a mask. The vapor from the evaporator arrangement is directed toward the substrate through the mask to create a patterned film on the substrate. One or more materials may be deposited onto the substrate through one or more masks to create pixels that can be addressed individually to create functional devices such as full color displays.

[6] The quality of the deposition is typically linked to the deposition parameters and how well they can be monitored and maintained. Running the process with improper deposition parameters may result in a poor quality of the deposited layers.

[7] In light of the above, an improved evaporation of a source material would be beneficial for ensuring a high quality deposition of the evaporated material, particularly in the manufacture of OLED devices. Specifically, an exposure of the sensitive source material to elevated temperatures should be kept as short as possible, and excessive material heating temperatures should be reliably avoided. SUMMARY

[8] In light of the above, an evaporator arrangement, a deposition system, as well as an evaporation method are provided. [9] According to an aspect, an evaporator arrangement is provided. The evaporator arrangement includes a heatable porous structure for evaporating a source material and a temperature monitoring device. The temperature monitoring device includes a wire, the wire being in thermal contact with the heatable porous structure.

[10] In some embodiments, the porous structure may be a foam structure, particularly a foam structure including a carbon foam.

[11] According to an aspect, a deposition system is provided. The deposition system includes a vacuum chamber and an evaporation source. The evaporation source is arranged in the vacuum chamber and includes an evaporator arrangement and a distribution pipe. The distribution pipe is in fluid communication with the evaporator arrangement and is configured to direct the evaporated source material toward a substrate to be coated. The evaporator apparatus is configured in accordance with any of the embodiments described herein.

[12] According to an aspect, an evaporation method is provided. The evaporation method includes evaporating a source material through contact with a heatable porous structure, and determining a temperature of the heatable porous structure with a temperature monitoring device. The temperature monitoring device includes a wire in thermal contact with the heatable porous structure.

[13] Embodiments are also directed at apparatuses for carrying out the disclosed methods and include apparatus parts for performing the described method aspects. These method aspects may be performed by way of hardware components, a computer programmed by appropriate software, by any combination of the two or in any other manner. Furthermore, embodiments according to the disclosure are also directed at methods for operating the described apparatuses. It includes method aspects for carrying out the functions of the apparatuses.

BRIEF DESCRIPTION OF THE DRAWINGS [14] So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to embodiments. The accompanying drawings relate to embodiments of the disclosure and are described in the following: FIG. 1 shows a schematic top view of an evaporator arrangement according to embodiments described herein;

FIG. 2 shows a schematic top view of an evaporator arrangement according to embodiments described herein;

FIG. 3 shows a schematic perspective view of an evaporator arrangement according to embodiments described herein;

FIG. 4 shows a schematic perspective view of an evaporator arrangement according to embodiments described herein;

FIG. 5 shows a schematic perspective view of an evaporator arrangement according to embodiments described herein; FIG. 6 shows a schematic perspective view of an evaporator arrangement according to embodiments described herein;

FIG. 7 shows a schematic sectional view of an evaporator arrangement according to embodiments described herein;

FIG. 8 shows a schematic view of a deposition system according to embodiments described herein; and

FIG. 9 shows a flow diagram for illustrating a method according to embodiments described herein.

DETAILED DESCRIPTION OF EMBODIMENTS [15] Reference will now be made in detail to the various embodiments of the disclosure, one or more examples of which are illustrated in the figures. Within the following description of the drawings, the same reference numbers refer to same components. Only the differences with respect to individual embodiments are described. Each example is provided by way of explanation of the disclosure and is not meant as a limitation of the disclosure. Further, features illustrated or described as part of one embodiment can be used on or in conjunction with other embodiments to yield yet a further embodiment. It is intended that the description includes such modifications and variations.

[16] Embodiments described herein relate to evaporator arrangements configured to evaporate a source material, particularly an organic material that is to be evaporated and deposited on a substrate. Evaporator arrangements may include an evaporation crucible and a heating device for heating an inner volume of the evaporator crucible. The source material may be placed in the inner volume of the crucible for being heated and evaporated. However, it is difficult to maintain the inner volume of the crucible at a temperature that is suitable for providing an appropriate evaporation rate. Further, there may be a risk of material decomposition in the evaporation crucible, because the source material inside the crucible may be exposed to elevated temperatures over an extended time, and only an outer surface layer of the source material that is exposed to the highest temperatures in the evaporation crucible may actually evaporate.

[17] To ensure a high quality and a long lifetime of the coated substrate, it is beneficial that the deposited organic layers are free of contaminants and free of thermal decomposition products. Decomposition products may be generated when the source material to be evaporated is exposed to elevated temperatures over an extended time. If temperatures or temperature profiles are not on point or accurately followed, a thermal decomposition of the source material may be a consequence.

[18] Accordingly, it would be beneficial to provide an evaporator arrangement that reduces the risk of material decomposition and that allows for a temperature monitoring closer to a position where the actual evaporation takes place. In particular, the temperature of the source material should be monitored directly at the evaporation site or at multiple positions where evaporation takes place. Being able to more accurately monitor a temperature in the evaporator arrangement may beneficially increase the efficiency and quality of an evaporation, may prevent excessive temperature exposures of the source material and may lead to a better deposition quality.

[19] According to embodiments described herein, an evaporator arrangement is provided. The evaporator arrangement includes a heatable porous structure for evaporating a material to be evaporated and a temperature monitoring device. The temperature monitoring device includes a wire in thermal contact with the heatable porous structure.

[20] Fig. 1 exemp lardy depicts an evaporator arrangement 100 with a heatable porous structure 102 and a temperature monitoring device 110. The heatable porous structure 102 may be a heatable foam structure. The temperature monitoring device 110 includes the wire 112 that is in thermal contact with the heatable porous structure. The temperature monitoring device 110 can measure a temperature of the heatable porous structure 102 directly at a position at which the source material is heated and evaporated by the heatable porous structure. Beneficially, the temperature of the heatable porous structure 102 at a position where the heatable porous structure 102 is in thermal contact with the wire 112 can be measured.

[21] The heatable porous structure 102 as used herein is utilized in the evaporator arrangement 100 for heating the source material to a temperature at or above the evaporation temperature of the source material. In particular, the source material can be brought in contact with the heatable porous structure while the heatable porous structure 102 is provided at an elevated temperature, such that the portion of the source material that contacts the heatable porous structure 102 is evaporated. In other words, the heatable porous structure 102 may be used as a heating element in the evaporator arrangement. When the source material is heated by a porous structure, particularly an open-cell porous structure, the vapor may pass through the pores or cells of the heatable porous structure toward a vapor distribution arrangement. The evaporated source material can then be directed toward a substrate by the vapor distribution arrangement.

[22] Different from evaporation crucibles with a heated inner volume for placing a large amount of source material at elevated temperatures, according to embodiments described herein, only a portion of the source material that is brought into contact with the heatable porous structure 102 can be evaporated, whereas a remainder of the source material may be maintained at a considerably lower temperature, e.g. in a material reservoir. Material decomposition can be reduced and the deposition quality can be improved.

[23] In some embodiments, the source material is placed on a top side of the heatable porous structure, e.g. in a solid form, such as a powder or granulate. A lower layer of the source material contacting the heatable porous structure may evaporate and pass through and exit the heatable porous structure at a bottom side thereof. In other embodiments, the heatable porous structure may be pressed onto a specific portion of the source material. The contacted portion may evaporate and pass through the heatable porous structure for being directed toward a substrate. In other embodiments, the source material may be guided through the heatable porous structure by a carrier, e.g. a carrier gas. In other embodiments, the heatable porous structure may be coated with the source material, such that the source material evaporates when the heatable form structure is heated. Specifically, only a limited portion of the source material brought in contact with the heatable porous structure may evaporate and pass at least partially through the heatable porous structure, whereas a main portion of the source material may be placed in a material reservoir provided at a temperature well below the evaporation temperature of the source material. Material degradation can be reduced.

[24] The heatable porous structure 102 of embodiments described herein is heatable, particularly to temperatures at or above the evaporation temperature of typical organic materials, particularly to a temperature of 200°C or more, 250°C or more, 300°C or more, or even 400°C or more. For example, the heatable porous structure 102 is directly or indirectly heatable. In embodiments, the heatable porous structure 102 is configured as a resistive heater that is heated by guiding electric current through the heatable porous structure, e.g. from a first side of the heatable porous structure to a second side of the heatable porous structure. Providing a resistive heater may be beneficial because the heatable porous structure can be heated directly at a position at which the source material is to be brought in contact with the heatable porous structure.

[25] The term“porous structure” as used herein may be understood as a foam, mesh, porous material or grid structure with a plurality of openings, particularly open pores or cells, for the evaporated source material to propagate through the porous structure. The term “porous structure” as used herein may be understood as a structure that is permeable for the evaporated source material to propagate through the structure. The porous structure may have a porosity of 50% or more, 80% or more, 90% or more, or even 95% or more, e.g. about 97%. Alternatively or additionally, the porous structure may have a porosity of 99% or less. The porous structure may have 5 or more pores per inch (ppi), 45 ppi or more, or 100 ppi or more. Additionally or alternatively, the porous structure may have 200 ppi or less.

[26] In some embodiments, which can be combined with other embodiments described herein, the heatable porous structure includes an electrically conductive foam. The foam may include a material that is electrically conductive, such as, e.g., carbon or another conductor material, e.g. metal. In particular, the heatable porous structure may include a carbon foam. In some embodiments, the heatable porous structure includes a conductive, open-cell reticulated foam, particularly an open cell carbon foam. Open-cell vitreous carbon foam, also called reticulated vitreous carbon foam, is a vitreous carbon structure of three dimensional interconnected polyhedron cells. The carbon material may be a glassy carbon (as opposed to a graphitic carbon). An“open-cell porous structure” as used herein relates to a structure where no film or solid is connected between the ligaments so that there is free communication into and out of a foam cell, and groups of adjoining cells are typically interconnected and form a 3D interconnected structure. A carbon foam is beneficial in view of the foam properties and porosity, at the same time being conductive, such that the carbon foam can be used as a resistive heating element by guiding electric current therethrough.

[27] In some embodiments, the heatable porous structure further includes an electrically insulating material layer on the electrically conductive foam. The electrically insulating material layer may electrically insulate the electrically conductive foam. In particular, the electrically insulating foam may be electrically insulated from an environment by the electrically insulating material layer. The electrically insulating material layer may form the outer surface layer of the heatable porous structure. In other words, the heatable porous structure may have an electrically insulating surface layer covering an electrically conductive inner porous structure.

[28] The electrically insulating material layer may be a layer with a high thermal conductivity, such that the heat of the electrically conductive foam is conducted to the outer surface of the heatable porous structure where the source material is brought in contact with the heatable porous structure. In other words, the electrically insulating material layer may include an electrically insulating, but thermally conductive material, which may form the outer surface layer of the heatable porous structure. For example, in some embodiments, the electrically insulating material layer may include a thermally conductive ceramic material, e.g. SiC.

[29] The wire 112 may be provided in thermal contact with the heatable porous structure, particularly in thermal contact with the electrically insulating material layer of the heatable form structure. Accordingly, the temperature of the electrically insulating material layer can be measured at specific positions at which the source material is brought in contact with the electrically insulating material layer for evaporating the source material. In some embodiments, the wire 112 is not in electrical contact with the electrically conductive foam, but is in thermal contact with the electrically insulating material layer covering the electrically conductive foam. Accordingly, the temperature of the heatable porous structure can be measured with the wire 112 independent of a current that may be guided through the electrically conductive foam acting as a resistive heating element. Further, by laying the wire along a predetermined path along the electrically insulating material layer, the temperature of the electrically insulating material layer can be determined along the predetermined path, where the temperature may be of particular interest for providing appropriate evaporation conditions. Determining the temperature along a predetermined path may mean that an average temperature of the wire along the path is determined.

[30] According to some embodiments described herein, the electrically conductive foam may be an open-cell reticulated structure. An open-cell reticulated structure as used herein may refer to a solid foam with interconnected open pores that form an interconnected network. The electrically insulating material may cover inner surfaces of the electrically conductive foam, e.g. the pore surfaces in an inner volume of the open-cell reticulated structure. The electrically insulating material may additionally cover outer surfaces of the electrically conductive foam, i.e. exposed foam surfaces that are visible when looking at the foam from an outside position. In particular, the electrically conductive foam may be an open cell reticulated structure that is coated with the electrically insulating material, e.g. via a vapor deposition method in which a vapor of the electrically insulating material is guided through the electrically conductive foam and adheres to outer foam surfaces as well as to pore surfaces in the inner volume of the electrically conductive foam.

[31] The electrically insulating material may be deposited on the surfaces of the electrically conductive foam via, e.g., a vapor infiltration or a CVD method. The surface area of the electrically conductive foam may be covered essentially entirely with the electrically insulating material. The electrically insulating material may be applied to the electrically conductive foam by at least one deposition method or a combination of deposition methods. The electrically insulating material layer may include one or more electrically insulating material layers for electrically insulating the electrically conductive foam from the environment.

[32] According to some embodiments described herein, the electrically insulating material layer may include a polymer or a ceramic, such as silicon carbide (SiC). Specifically, the heatable porous structure may be a carbon foam with an electrically insulating SiC-layer provided thereon. Silicon carbide is beneficial, having a high thermal conductivity, being an electric insulator, and being a material that can be deposited on a conductive foam, such as a carbon foam.

[33] According to some embodiments described herein, the wire may be a wire including an electrically conductive material, particularly a metal wire, such as a tungsten wire. In some embodiments, the wire may be a pure metal wire, particularly a pure tungsten wire, without a dielectric jacket or sheath surrounding the wire. In particular, the wire may be a pure metal core, which can be brought into direct thermal contact with the heatable porous structure, particularly with the electrically insulating material layer of the heatable porous structure. In some embodiments, the wire may be electrically insulated from the electrically conductive foam via the electrically insulating material layer that covers the electrically conductive foam. The wire may be in thermal contact with the heatable porous structure. The wire may be thermally connected to the heatable porous structure. The wire may be thermally connected to the electrically insulating material layer.

[34] According to some embodiments, which can be combined with other embodiments described herein, the temperature monitoring device is configured to measure a resistance change of the wire and to determine a temperature of the heatable porous structure based on the resistance change. The resistivity of typical conductive materials is temperature dependent. Accordingly, the resistance of a wire made of a specific material, such as of a metal wire, changes depending on the temperature of the wire, the resistivity of the material of the wire being temperature dependent. Accordingly, by determining a resistance change of the wire, the temperature of the wire can be determined. The temperature of the wire 112 essentially corresponds to the temperature of the heatable porous structure 102 when the wire is in direct thermal contact with the heatable porous structure. Accordingly, an evaporator arrangement is provided according to embodiments described herein, which is suitable for measuring a temperature directly at a position at which evaporation takes place. A more accurate temperature control is enabled and the risk of material decomposition can be reduced.

[35] Fig. 2 schematically depicts an evaporator arrangement 200 according to embodiments described herein in a top view. The evaporator arrangement 200 may include any of the features of the evaporator arrangement 100, such that reference can be made to the above explanations, which are not repeated here.

[36] The evaporator arrangement 200 includes a heatable porous structure 202 and a temperature monitoring device. The temperature monitoring device includes a wire 212. The wire 212 is in thermal contact with the heatable porous structure 202, such that the temperature of the heatable porous structure 202 can be determined via a resistance measurement of the wire.

[37] In some embodiments, which can be combined with other embodiments described herein, the wire 212 extends in a temperature measurement plane, the temperature measurement plane being transverse to or perpendicular to an evaporation direction along which the evaporated source material passes through the heatable porous structure. Accordingly, the temperature in a specific plane perpendicular to the evaporation direction can be determined with the temperature monitoring device. For example, the temperature can be measured in a plane in which most of the evaporation of the source material actually takes place. The wire may extend in the temperature measurement plane along a predetermined path, e.g. a curved and/or meandering path, such that essentially an average temperature of a predetermined area in the temperature measurement plane can be determined. In implementations, the temperature measurement plane may be parallel to and extend through the heatable porous structure. In implementations, the temperature measurement plane may essentially correspond to one of a top plane and a bottom plane of the heatable porous structure.

[38] In some implementations, the temperature monitoring device may include two or more wires extending through two or more different temperature measurement planes transverse to the evaporation direction. The temperatures in different planes of the heatable porous structure can be determined.

[39] In some embodiments, the wire 212 may have a meandering shape, i.e. may extend along a meander- shaped path in contact with the heatable porous structure 202. The meander shaped path may have a plurality of curves or bends. For example, the wire 212 may have a first connecting end 214 on a first side of the heatable porous structure 202 and a second connecting end 216 on a second side of the heatable porous structure 202 different from the first side. Alternatively, the wire 212 may have a first connecting end and a second connecting end on the same side of the heatable porous structure 202. The heatable porous structure 202 may have electrodes 220 on (opposite) sides of the heatable porous structure 202 for resistively heating the heatable porous structure 202 by guiding an electric current therethrough from a first side to a second side. The wire 212 may have one of a series of regular or irregular curves, bends, loops, turns, or windings. In some embodiments, the wire 212 may have a spiral-like shape, i.e. may extend along a spiral-shaped path in contact with the heatable porous structure (not shown). An essentially average temperature of a specific area in a temperature measurement plane in which the wire extends can be reliably determined.

[40] According to some embodiments, electrodes may be used to contact different sides of the electrically conductive foam for guiding current therethrough. Accordingly, the heatable porous structure can be resistively heated to elevated temperatures. Alternatively, the heatable porous structure may be inductively heated or may be indirectly heated by being contacted with a heating element.

[41] According to some embodiments, the wire may have a geometrical shape that extends in a two-dimensional plane. In particular, the wire may have a spiral- like shape or a meandering shape. Alternatively, the wire may have a three-dimensional shape. According to some embodiments, the wire may extend in two dimensions or in three dimensions. According to some embodiments, the wire may have a (quasi) one-dimensional shape. A temperature at a predetermined position or an (average) temperature of a predetermined two- dimensional area or three-dimensional volume can be determined.

[42] Fig. 3 schematically depicts an evaporator arrangement 300 according to embodiments described herein. The evaporator arrangement 300 may include any of the features of the previously described evaporator arrangements, such that reference can be made to the above explanations, which are not repeated here.

[43] The evaporator arrangement 300 includes two wires 312 and 314 that are embedded in a heatable porous structure of the evaporator arrangement 300. In particular, the two wires 312 and 314 may be embedded in the heatable porous structure such that the two wires 312 and 314 are electrically insulated with respect to an electrically conductive foam of the heatable porous structure. Alternatively or additionally, at least one wire may be in thermal contact with a top surface and/or a bottom surface of the heatable porous structure. The evaporator arrangement may have, according to some embodiments, more than two wires. For example, a plurality of wires may increase the number of measurable temperatures at different locations, different planes or different volumes of the evaporator arrangement and may thus improve an accuracy of the temperature monitoring device. Beneficially, monitoring and/or controlling a temperature of the evaporator arrangement may be improved.

[44] According to some embodiments, the wire may be located between two layers of the heatable porous structure. The wire or an additional wire may, additionally or alternatively, be embedded in one or more layers of the heatable porous structure. For example, the heatable porous structure may include two or more stacked layers, e.g. with the wire arranged therebetween, particularly in a temperature measurement plane that is parallel to the two or more layers of the heatable porous structure.

[45] Fig. 4 schematically depicts an evaporator arrangement 400 according to embodiments described herein. The evaporator arrangement 400 may include any of the features of the previously described evaporator arrangements, such that reference can be made to the above explanations, which are not repeated here.

[46] The evaporator arrangement 400 may include a first layer 430 and a second layer 432 of a heatable porous structure 402. The first layer 430 and/or the second layer 432 may include any of the features of the previously described heatable porous structures, which are not repeated here. A wire 412 may be embedded between the first layer 430 and the second layer 432 of the heatable porous structure 402. The heatable porous structure 402 may include more than two layers with more than one wire embedded between adjacent layers of the heatable porous structure 402. A heatable porous structure 402 with two layers having the wire arranged therebetween can be easily manufactured and provides a reliable temperature measurement in a predetermined temperature measurement plane.

[47] According to some embodiments, which can be combined with other embodiments described herein, the heatable porous structure may have the shape of a flat sheet, such that the evaporated source material can pass therethrough along an evaporation direction perpendicular to the extension of the flat sheet. The heatable porous structure may have a shape that provides a top surface, capable of supporting the source material to be evaporated, such as e.g. a powder.

[48] Fig. 5 schematically depicts an evaporator arrangement 500 according to embodiments described herein. The evaporator arrangement 500 may include any of the features of the previously described evaporator arrangements, such that reference can be made to the above explanations, which are not repeated here.

[49] The evaporator arrangement 500 includes a heatable porous structure 502 that has a top surface 540. The top surface 540 may correspond to a side of the heatable porous structure 502 where the heatable porous structure 502 is contacted by the source material. An evaporation direction, as indicated by arrow 550, may be perpendicular to the top surface 540 and extend along a direction in which the vapor passes through the heatable porous structure.

[50] The evaporator arrangement 500 includes a wire 512, as exemplarily depicted in Fig. 5, that is arranged on the top surface 540 of the heatable porous structure 502. The source material may be brought in contact with the top surface 540 of the heatable porous structure 502 and be evaporated due to the elevated temperature of the top surface 540 of the heatable porous structure 502. It may therefore be beneficial to monitor a temperature at the top surface of the heatable porous structure for improving the deposition quality.

[51] According to some embodiments, the temperature monitoring device may be configured to measure a resistivity change of the wire material or a resistance change of the wire. The temperature monitoring device may determine a temperature of the heatable porous structure based on the resistance change.

[52] Fig. 6 schematically depicts an evaporator arrangement 600 according to embodiments described herein. The evaporator arrangement 600 may include any of the features of the previously described evaporator arrangements, such that reference can be made to the above explanations, which are not repeated here.

[53] The evaporator arrangement 600 includes a wire 612 that is embedded in the heatable porous structure 602. The wire 612 has a three-dimensional shape and is embedded in the heatable porous structure 602. A temperature monitoring in a specific area or volume of the heatable porous structure is enabled.

[54] According to some embodiments, which can be combined with other embodiments described herein, the evaporator arrangement may further include a material reservoir for the source material. The material reservoir for the source material may be located on a first side of the heatable porous structure. The evaporator arrangement may further include a vapor conduit on a second side of the heatable porous structure. Accordingly, the evaporated source material may pass through the heatable porous structure from the first side where the material reservoir is arranged to the second side where the vapor conduit is arranged. The vapor conduit may guide the evaporated source material to a distribution assembly, which may be configured to direct the evaporated source material toward a substrate.

[55] Fig. 7 schematically depicts an evaporator arrangement 700 according to embodiments described herein. The evaporator arrangement 700 may include any of the features of the previously described evaporator arrangements, such that reference can be made to the above explanations, which are not repeated here.

[56] In some implementations, the evaporator arrangement may include a material reservoir 760. The material reservoir 760 accommodates the source material 770, particularly an organic material. A lower portion of the source material 770 may be in contact with a top surface 740 of a heatable porous structure 702 of the evaporator arrangement 700. The portion of the source material 770 that is in contact with the top surface 740 is heated and evaporated by the heatable porous structure 702. The source material 770 in Fig. 7 is exemplarily depicted as a solid material in powder form. The source material 770 may liquefy when being heated by the heatable porous structure 702 to form a liquid phase on top of the heatable porous structure 702. The melted phase may infiltrate the heatable porous structure 702 due to gravity and/or due to an applied force. The melted phase evaporates and passes through the heatable porous structure to be guided by the vapor conduit 780 on a second side 742 of the heatable porous structure into a distribution assembly.

[57] Fig. 8 shows a schematic sectional view of a deposition system 888 according to embodiments described herein. The deposition system includes a vacuum chamber 801 and an evaporation source 889 that is arranged in the vacuum chamber 801. The evaporation source 889 includes an evaporator arrangement 800 according to any of the embodiments described herein. The evaporator arrangement 800 may include any of the features of the previously described evaporator arrangements, such that reference can be made to the above explanations, which are not repeated here.

[58] The evaporation source 889 may further include a distribution pipe 890. The distribution pipe 890 may be in fluid communication with the evaporator arrangement 800, such that the evaporated source material can propagate from the evaporator arrangement 800 into the distribution pipe 890. The distribution pipe 890 may be configured to direct the evaporated source material towards a substrate 10 to be coated. [59] In some embodiments, which can be combined with other embodiments described herein, the distribution pipe 890 may include a plurality of vapor outlets for directing the evaporated source material toward the substrate. The distribution pipe may extend in an essentially vertical direction. For example, the distribution pipe may be an essentially vertical line source.

[60] The evaporator arrangement 800 may include a material reservoir 870 arranged on top of a heatable foam structure. Source material to be evaporated is accommodated in the material reservoir. The evaporated source material that contacts the heated foam structure evaporates, propagates through the heatable foam structure into the distribution pipe 890 and is directed towards the substrate 10. The temperature of the heatable foam structure can be monitored via a wire that is in thermal contact with the heatable foam structure (not depicted in FIG. 8).

[61] In some embodiments, at least one of a first drive for moving the evaporation source along a source path in the vacuum chamber and a second drive for changing an orientation of the distribution pipe of the evaporation source may be provided. For example, the evaporation source can be moved along a linear source path past the substrate via the first drive. For example, the distribution pipe 890 can be rotated together with the evaporator arrangement 800 for changing the direction of a plurality of vapor outlets via the second drive.

[62] According to another aspect, an evaporation method is provided. The method may include evaporating a source material, e.g. an organic material. Evaporating may be achieved through contact of the source material with a heatable porous structure. The method further includes determining a temperature of the heatable porous structure with a temperature monitoring device. The temperature monitoring device may include a wire in thermal contact with the heatable porous structure.

[63] Fig. 9 is a flow diagram illustrating a method according to embodiments described herein.

[64] In box 901, the method includes evaporating the source material through contact with a heatable porous structure.

[65] In box 902, a temperature of the heatable porous structure is determined with a temperature monitoring device including a wire in thermal contact with the heatable porous structure, particularly in direct contact with the heatable porous structure. [66] In optional box 903, a temperature of the heatable porous structure may be adjusted based on the determined temperature. To adjust a temperature of the heatable porous structure, the temperature monitoring device may include a control loop in hardware and/or software for determining a temperature based on a resistance change of the wire and for controlling the heating of the heatable porous structure accordingly.

[67] Determining the temperature of the heatable porous structure in box 902 may include measuring a resistance change of the wire, and determining the temperature of the heatable porous structure based on the measured resistance change. Measuring a resistance change of the wire may be performed by a temperature monitoring device. The temperature monitoring device may include a controller and/or a processor for determining a temperature based on the measured resistance change. The controller and/or the processor may be configured to measure a resistance change of a wire. The wire may be electrically connected to an input of the controller and/or the processor for determining a resistance change of the wire due to a temperature change of the wire.

[68] According to some embodiments described herein, determining a temperature of the heatable porous structure may include determining a temperature in a two-dimensional plane of the heatable porous structure or a temperature in a three dimensional volume of the heatable porous structure in which the wire extends. For example, the resistance of a wire extending in a two-dimensional plane may change according to a temperature or a temperature gradient in the plane. For example, the resistance of a wire extending along a three-dimensional path in a volume of the heatable porous structure may change according to a temperature or a temperature gradient in the volume.

[69] Before evaporating the source material in box 901, the source material may optionally be placed on top of the heatable porous structure, e.g., in a material reservoir, such that a bottom layer of the source material contacts the heatable porous structure.

[70] Evaporating the source material in box 901 may optionally include resistively heating the heatable porous structure to a temperature at or above the evaporation temperature of the source material, e.g. to a temperature of 200°C or more, particularly 250°C or more, more particularly 300°C or more, or even 400°C or more.

[71] The evaporation method may further include guiding evaporated source material through the heatable porous structure into a vapor conduit below the heatable porous structure. The vapor conduit may guide the evaporated source material into a distribution pipe that is configured for directing the evaporated source material toward a substrate to be coated.

[72] Advantageously, the evaporator arrangement allows for an improved determination of a temperature of the heatable porous structure. [73] The term“source material” or“material to be evaporated” or“material to be deposited” as used throughout the disclosure, may be understood as a material that is suitable for being deposited on a substrate in an evaporation process. The material may be provided as a solid material and/or a liquid material. For example, the material may be provided in a powder form or a liquid. The material may directly transition from a solid phase into a gaseous face, for example, the material may sublimate at a certain temperature depending on the material used. Alternatively, the material may be a material that is transitioned from a solid phase to a liquid phase and then to a gaseous phase, for example, the material may liquefy at a certain temperature and may then evaporate at another higher temperature.

[74] While the foregoing is directed to embodiments, other and further embodiments may be devised without departing from the basic scope, and the scope is determined by the claims that follow.

[75] In particular, this written description uses examples to disclose the disclosure, including the best mode, and also to enable any person skilled in the art to practice the described subject-matter, including making and using any devices or systems and performing any incorporated methods. While various specific embodiments have been disclosed in the foregoing, mutually non-exclusive features of the embodiments described above may be combined with each other. The patentable scope is defined by the claims, and other examples are intended to be within the scope of the claims if the claims have structural elements that do not differ from the literal language of the claims, or if the claims include equivalent structural elements with insubstantial differences from the literal language of the claims.