TECHNICAL FIELD

[0001] Embodiments of the present disclosure relate to the deposition of materials on a substrate and to apparatuses for depositing materials on a substrate, e.g. organic materials. Embodiments of the present disclosure particularly relate to evaporation sources for depositing an evaporated source material, e.g. an organic material, on a substrate. Further embodiments relate to shielding devices for an evaporation source as well as to methods of depositing material, e.g. organic material, on a substrate.

BACKGROUND

[0002] Organic evaporators are a tool for the production of organic light-emitting diodes (OLED). OLEDs are a special type of light-emitting diode in which the emissive layer comprises a thin-film of certain organic compounds. Organic light emitting diodes (OLEDs) are used in the manufacture of television screens, computer monitors, mobile phones and other hand-held devices for displaying information. OLEDs can also be used for general space illumination. The range of colors, brightness, and viewing angles possible with OLED displays are 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. A typical OLED display, for example, may include layers of organic material situated between two electrodes that are all deposited on a substrate in a manner to form a matrix display panel having individually energizable pixels. The OLED is generally placed between two glass panels, and the edges of the glass panels are sealed to encapsulate the OLED therein.

[0003] There are many challenges encountered in the manufacture of such display devices. OLED displays or OLED lighting applications include a stack of several organic materials, which are for example evaporated in a vacuum. The organic materials are deposited in a subsequent manner through shadow masks. For the fabrication of OLED stacks 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.

[0004] For depositing the material on a substrate, the material is heated until the material evaporates. Distribution pipes guide the evaporated material to the substrates through nozzles. In recent years, the precision of the deposition process has been increased, e.g. allowing for being able to provide smaller and smaller pixel sizes. In some processes, masks are used for defining the pixels when the evaporated material passes through the mask openings. However, shadowing effects of a mask, the spread of the evaporated material and the like make it difficult to further increase the precision and the predictability of the evaporation process.

[0005] In view of the above, an increased precision and predictability of evaporation processes for manufacturing devices having a high quality and precision is beneficial.

SUMMARY

[0006] In light of the above, evaporation sources, shielding devices for evaporation sources as well as methods for depositing an evaporated source material on a substrate are provided.

[0007] According to an aspect of the present disclosure, an evaporation source for depositing an evaporated source material on a substrate is provided. The evaporation source comprises one or more distribution pipes with a plurality of nozzles, wherein each nozzle of the plurality of nozzles is configured for directing a plume of evaporated source material toward the substrate; and a shielding device comprising a plurality of apertures, wherein at least one aperture of the plurality of apertures is configured to shape the plume of evaporated source material emitted from a single associated nozzle.

[0008] In some embodiments, each aperture of the plurality of apertures is configured to individually shape a plume of evaporated source material emitted from a single associated nozzle of the plurality of nozzles.

[0009] According to a further aspect of the present disclosure, a shielding device for an evaporation source for depositing an evaporated source material on a substrate is provided. The shielding device comprises a plurality of separate shielding units, wherein each shielding unit of the plurality of separate shielding units comprises one or more apertures configured as a passage surrounded by a circumferential wall, respectively, wherein each aperture of the one or more apertures is configured to individually shape a plume of evaporated source material emitted from a single associated nozzle of the evaporation source.

[0010] According to a further aspect of the present disclosure, a method for depositing an evaporated source material on a substrate in a vacuum chamber is provided. The method comprises guiding an evaporated source material through a plurality of nozzles of an evaporation source, wherein each of the plurality of nozzles generates a plume of evaporated source material propagating toward the substrate; and individually shaping the plumes of evaporated source material by a plurality of apertures of a shielding device. [0011] Further aspects, advantages and features of the present disclosure are apparent from the description and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] 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 present disclosure, briefly summarized above, may be had by reference to embodiments. The accompanying drawings relate to embodiments of the present disclosure and are described in the following:

[0013] FIG. 1 shows a schematic top view of a deposition apparatus including an evaporation source according to embodiments described herein;

[0014] FIG. 2A, FIG. 2B, and FIG. 2C show schematic views of portions of an evaporation source according to embodiments described herein;

[0015] FIG. 3 shows a schematic top view of an evaporation source according to embodiments described herein;

[0016] FIG. 4 shows a schematic top view of an evaporation source with three distribution pipes according to embodiments described herein; [0017] FIG. 5 shows a schematic sectional view of an evaporation source according to embodiments described herein;

[0018] FIG. 6 is a perspective view of a shielding device according to embodiments described herein; [0019] FIG. 7 is a perspective view of a shielding device according to embodiments described herein;

[0020] FIG. 8A and FIG. 8B are schematic views of two subsequent phases during operation of a deposition apparatus with an evaporation source according to embodiments described herein; and

[0021] FIG. 9 is a flow diagram illustrating a method for depositing an evaporated source material on a substrate according to embodiments described herein.

DETAILED DESCRIPTION OF EMBODIMENTS

[0022] Reference will now be made in detail to the various embodiments of the present 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 the same components. Generally, only the differences with respect to individual embodiments are described. Each example is provided by way of explanation and is not meant as a limitation of present disclosure. 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.

[0023] As used herein, the term "source material" may be apprehended as a material that is evaporated and deposited on a surface of a substrate. For example, in embodiments described herein, an evaporated organic material that is deposited on a surface of a substrate may be a source material. Non-limiting examples of organic materials include one or more of the following: ITO, NPD, Alq ₃ , Quinacridone, Mg/AG, starburst materials, and the like.

[0024] As used herein, the term "evaporation source" may be understood as an arrangement providing an evaporated source material to be deposited on a substrate. In particular, the evaporation source may be configured to direct an evaporated source material to be deposited on a substrate into a deposition area in a vacuum chamber, such as a vacuum deposition chamber of a deposition apparatus. The evaporated source material may be directed toward the substrate via a plurality of nozzles of the evaporation source. The nozzles may have nozzle outlets, respectively, which may be directed toward the deposition area, particularly toward the substrate to be coated. [0025] The evaporation source may include an evaporator or a crucible which evaporates the source material to be deposited on the substrate, and a distribution pipe, which is in fluid connection with the crucible and which is configured to transport the evaporated source material to the plurality of nozzles for emitting the evaporated source material into the deposition area.

[0026] In some embodiments, the evaporation source includes two or more distribution pipes, wherein each distribution pipe has a single nozzle. In some embodiments, the evaporation source includes two or more distribution pipes, wherein each distribution pipe includes a plurality of nozzles. In some embodiments, a distribution pipe includes two or more nozzles, particularly ten or more nozzles. In some embodiments, the evaporation source includes two or more distribution pipes arranged next to each other, wherein each of the two or more distribution pipes includes ten or more nozzles.

[0027] As used herein, the term "crucible" may be understood as a device or a reservoir providing or containing the source material to be deposited. Typically, the crucible may be heated for evaporating the source material to be deposited on the substrate. According to embodiments herein, the crucible may be in fluid communication with the distribution pipe to which the evaporated source material may be delivered.

[0028] As used herein, the term "distribution pipe" may be understood as a pipe for guiding and distributing the evaporated source material. In particular, the distribution pipe may guide the evaporated source material from a crucible to the plurality of nozzles in the distribution pipe. As used herein, the term "a plurality of nozzles" typically includes at least two or more nozzles, each nozzle including a nozzle outlet for emitting an evaporation source material toward the substrate along a main emission direction. According to embodiments described herein, the distribution pipe may be a linear distribution pipe extending in a first, especially longitudinal, direction, particularly in a vertical direction. In some embodiments, the distribution pipe may include a pipe having the shape of a cylinder. The cylinder may have a circular bottom shape or any other suitable bottom shape. Examples of distribution pipes will be described in more detail below. In some embodiments, the evaporation source may include two or three distribution pipes. In some embodiments, each distribution pipe is in fluid connection with a crucible such that different materials can be deposited on the substrate. [0029] FIG. 1 shows a schematic top view of a deposition apparatus 100 including an evaporation source 20 according to embodiments described herein. The deposition apparatus 100 includes a vacuum chamber 110 in which the evaporation source 20 is positioned. According to some embodiments, which can be combined with other embodiments described 5 herein, the evaporation source 20 is configured for a translational movement along a surface of the substrate to be coated. Further, the evaporation source 20 may be configured for rotation around a rotation axis.

[0030] According to embodiments, the evaporation source 20 may have one or more evaporation crucibles and one or more distribution pipes. For instance, the evaporation source 10 20 shown in FIG. 1 includes two evaporation crucibles 104 and two distribution pipes 106. As is shown in FIG. 1, a substrate 10 and a further substrate 11 are provided in the vacuum chamber 110 for receiving the evaporated source material.

[0031] According to some embodiments herein, a mask assembly for masking a substrate can be provided between the substrate and the evaporation source. The mask assembly may

15 include a mask and a mask frame to hold the mask in a predetermined position. In embodiments herein, one or more additional tracks may be provided for supporting and displacing the mask assembly. For instance, the embodiment shown in FIG. 1 has a first mask 133 supported by a first mask frame 131 arranged between the evaporation source 20 and the substrate 10 and a second mask 134 supported by a second mask frame 132 arranged between 0 the evaporation source 20 and the further substrate 11. The substrate 10 and the further substrate 11 may be supported on respective transportation tracks (not shown in FIG. 1) within the vacuum chamber 110.

[0032] FIG. 1 further shows a shielding device 30, which is provided to guide the evaporated source material from the distribution pipes 106 to the substrate 10 and/or to the 5 further substrate 11, respectively, as will be explained below in more detail. The shielding device 30 may be provided downstream from the nozzles, i.e. between the distribution pipes and the substrate. In some embodiments, the shielding device 30 may be detachably fixed to at least one distribution pipe, e.g. via screws.

[0033] In embodiments herein, if masks are used for depositing material on a substrate, such 30 as in an OLED production system, the mask may be a pixel mask with pixel openings having the size of about 50 μιη x 50 μιη, or even below, such as a pixel opening with a dimension of the cross section (e.g. the minimum dimension of a cross section) of about 30 μιη or less, or about 20 μιη. In one example, the pixel mask may have a thickness of about 40 μιη. Considering the thickness of the mask and the size of the pixel openings, a shadowing effect may appear, where the walls of the pixel openings in the mask shadow the pixel opening. The 5 shielding device 30 described herein may limit the maximum angle of impact of the evaporated source material on the masks and on the substrates and reduce the shadowing effect.

[0034] According to embodiments described herein, the material of the shielding device 30 may be adapted for evaporated source material having a temperature of about 100°C to about 10 600°C. In some embodiments, the shielding device may include a material having a thermal conductivity larger than 21 W / (m-K) and/or a material being chemically inert to, for instance, evaporated organic material. According to some embodiments, the shielding device may include at least one of Cu, Ta, Ti, Nb, DLC, and graphite or may include a coating with at least one of the named materials.

15 [0035] According to embodiments described herein, the substrate may be coated with a source material in an essentially vertical position. Typically, the distribution pipe 106 is configured as a line source extending essentially vertically. In embodiments described herein, which can be combined with other embodiments described herein, the term "vertically" is understood, particularly when referring to the substrate orientation, to allow for a deviation 0 from the vertical direction of 20° or below, e.g. of 10° or below. For example, this deviation can be provided because a substrate support with some deviation from the vertical orientation might result in a more stable substrate position. Yet, an essentially vertical substrate orientation during deposition of the source material is considered different from a horizontal substrate orientation. The surface of the substrate is coated by a line source extending in one 5 direction corresponding to one substrate dimension and a translational movement along the other direction corresponding to the other substrate dimension.

[0036] In some embodiments, the evaporation source 20 may be provided in the vacuum chamber 110 of the deposition apparatus 100 on a track, e.g. a looped track (not shown in the figures) or linear guide 120. The track or linear guide 120 is configured for the translational 30 movement of the evaporation source 20. According to different embodiments, which can be combined with other embodiments described herein, a drive for the translational movement can be provided in the evaporation source 20, at the track or linear guide 120, within the vacuum chamber 110 or a combination thereof. Accordingly, the evaporation source can be moved along the surface of the substrate to be coated during deposition, particularly along a linear path. Uniformity of the deposited material on the substrate can be improved.

[0037] FIG. 1 further shows a valve 105, for example, a gate valve. The valve 105 allows for a vacuum seal to an adjacent vacuum chamber (not shown in FIG. 1). According to embodiments described herein, the valve 105 can be opened for the transport of a substrate or a mask into and/or out of the vacuum chamber 110.

[0038] According to some embodiments, which can be combined with other embodiments described herein, a further vacuum chamber, such as maintenance vacuum chamber 111 is provided adjacent to the vacuum chamber 110. The vacuum chamber 110 and the maintenance vacuum chamber 111 may be connected by a valve 109. The valve 109 is configured for opening and closing a vacuum seal between the vacuum chamber 110 and the maintenance vacuum chamber 111. According to embodiments herein, the evaporation source 20 can be transferred to the maintenance vacuum chamber 111 while the valve 109 is in an open state. Thereafter, the valve can be closed to provide a vacuum seal between the vacuum chamber 110 and the maintenance vacuum chamber 111. If the valve 109 is closed, the maintenance vacuum chamber 111 can be vented and opened for maintenance of the evaporation source 20 without breaking the vacuum in the vacuum chamber 110.

[0039] The deposition apparatus may be used for various applications, including applications for OLED device manufacturing including processing methods, wherein two or more source materials such as, for instance, two or more organic materials are evaporated simultaneously. In the example shown in FIG. 1, two or more distribution pipes 106 and corresponding evaporation crucibles are provided next to each other. For example, in some embodiments, three distribution pipes may be provided next to each other, each distribution pipe including a plurality of nozzles with respective nozzle outlets for introducing the evaporated source material from the interior of the respective distribution pipe into the deposition area of the vacuum chamber. The nozzles may be provided along the linear extension direction of the respective distribution pipe, e.g. at an equal spacing. Each distribution pipe may be configured for introducing a different evaporated source material into the deposition area of the vacuum chamber. [0040] Although the embodiment shown in FIG. 1 provides a deposition apparatus 100 with an evaporation source 20 that is movable, the skilled person may understand that the above described embodiments may also be applied to deposition systems in which the substrate is moved during processing. For instance, the substrates to be coated may be guided and driven along stationary material deposition arrangements.

[0041] Embodiments described herein particularly relate to deposition of organic materials, e.g. for OLED display manufacturing on large area substrates. According to some embodiments, large area substrates or carriers supporting one or more substrates may have a size of at least 0.174 m ² . For instance, the deposition system may be adapted for processing large area substrates, such as substrates of GEN 5, which corresponds to about 1.4 m ² substrates (1.1 m x 1.3 m), GEN 7.5, which corresponds to about 4.29 m ² substrates (1.95 m x 2.2 m), GEN 8.5, which corresponds to about 5.7 m ² substrates (2.2 m x 2.5 m), or even GEN 10, which corresponds to about 8.7 m ² substrates (2.85 m x 3.05 m). Even larger generations such as GEN 11 and GEN 12 and corresponding substrate areas can similarly be implemented.

[0042] According to embodiments herein, which can be combined with other embodiments described herein, the substrate thickness can be from 0.1 to 1.8 mm and the holding arrangement for the substrate, can be adapted for such substrate thicknesses. The substrate thickness can be about 0.9 mm or below, such as 0.5 mm or 0.3 mm, and the holding arrangements are adapted for such substrate thicknesses. Typically, the substrate may be made from any material suitable for material deposition. For instance, the substrate may be made from a material selected from the group consisting of glass (for instance soda-lime glass, borosilicate glass etc.), metal, polymer, ceramic, compound materials, carbon fiber materials or any other material or combination of materials which can be coated by a deposition process.

[0043] According to some embodiments, which may be combined with other embodiments described herein, the deposition apparatus 100 may further include a material collection unit 40 which can be configured as a shielding wall. The material collection unit 40 may be arranged to collect evaporated source material emitted from the evaporation source and/or from the shielding device 30, when the evaporation source is in a rotated position, particularly during rotation of the evaporation source 20 around the rotation axis. [0044] In some embodiments, a heating device 50 may be provided for cleaning the shielding device in a service position of the deposition apparatus 100. The service position may be a position of the deposition apparatus in which the evaporation source is in a rotated position as compared to a deposition position of the deposition apparatus in which the nozzles of the evaporation source are directed toward a substrate to be coated.

[0045] FIG. 2A to FIG. 2C show parts of an evaporation source 20 according to embodiments described herein. As is shown in FIG. 2A, the evaporation source 20 can include a distribution pipe 106 and an evaporation crucible 104. For example, the distribution pipe can be an elongated cube with a heating unit 225. The evaporation crucible can be a reservoir for a source material, such as an organic material to be evaporated with a heating unit 225.

[0046] According to embodiments, which can be combined with other embodiments described herein, a plurality of nozzles 22 may be arranged along a length direction of the evaporation source 20. In particular, the plurality of nozzles may be arranged along a length direction of the distribution pipe.

[0047] According to some embodiments, which can be combined with other embodiments described herein, the distribution pipe 106 extends essentially vertically in a length direction. For example, the length of the distribution pipe 106 corresponds at least to the height of the substrate to be deposited in the deposition apparatus. In many cases, the length of the distribution pipe 106 will be longer than the height of the substrate to be deposited, at least by 10% or even 20%, which allows for a uniform deposition at the upper end of the substrate and/or the lower end of the substrate.

[0048] According to some embodiments, which can be combined with other embodiments described herein, the length of the distribution pipe can be 1.3 m or above, for example 2.5 m or above. According to one configuration, as shown in FIG. 2A, the evaporation crucible 104 is provided at the lower end of the distribution pipe 106. Typically, the source material is evaporated in the evaporation crucible 104. The evaporated source material enters at the bottom of the distribution pipe 106 and is guided essentially sideways through the plurality of outlets in the distribution pipe, e.g. toward an essentially vertically oriented substrate. [0049] According to some embodiments, which can be combined with other embodiments described herein, the plurality of nozzles is arranged such that the nozzle outlets define a main emission direction X that is essentially horizontal (+/- 20°). According to some specific embodiments, the main emission direction X can be oriented slightly upward, e.g. to be in a range from horizontal to 15° upward, such as 3° to 7° upward. Similarly, the substrate can be slightly inclined to be substantially perpendicular to the evaporation direction, which may reduce the generation of particles. For illustrative purposes, the evaporation crucible 104 and the distribution pipe 106 are shown without heat shields in FIG. 2A. The heating unit 215 and the heating unit 225 can be seen in the schematic perspective view shown in FIG. 2B. [0050] FIG. 2B shows an enlarged schematic view of a portion of the evaporation source, in particular, of the distribution pipe 106 connected to the evaporation crucible 104. A flange unit 203 is provided, which is configured to provide a connection between the evaporation crucible 104 and the distribution pipe 106. For example, the evaporation crucible and the distribution pipe are provided as separate units, which can be separated and connected or assembled at the flange unit, e.g. for operation of the evaporation source.

[0051] The distribution pipe 106 has an inner hollow space 210. A heating unit 215 is provided to heat the distribution pipe. The distribution pipe 106 can be heated to a temperature such that the evaporated source material provided by the evaporation crucible 104 does not condense at an inner portion of the wall of the distribution pipe 106. Two or more heat shields 217 are provided around the tube of the distribution pipe 106. The heat shields are configured to reflect heat energy provided by the heating unit 215 back toward the inner hollow space 210. The energy to heat the distribution pipe 106, i.e. the energy provided to the heating unit 215, can be reduced because the heat shields 217 reduce heat losses. Heat transfer to other distribution pipes and/or to the mask or substrate can be reduced. According to some embodiments, which can be combined with other embodiments described herein, the heat shields 217 can include two or more heat shield layers, e.g. five or more heat shield layers, such as ten heat shield layers.

[0052] Typically, as shown in FIG. 2B, the heat shields 217 include openings at positions of the nozzles in the distribution pipe 106. The enlarged view of the evaporation source shown in FIG. 2B shows four nozzles (schematically depicted as outlets). The nozzles can be provided along a length direction of the distribution pipe 106. As described herein, the distribution pipe 106 can be provided as a linear distribution pipe, for example, having a plurality of nozzles. For instance, the distribution pipe may have more than 30 nozzles, such as 40, 50 or 54 nozzles arranged along a length direction of the distribution pipe. According to embodiments herein, the nozzles may be spaced apart from each other. For instance, the nozzles may be spaced apart by a distance of 1 cm or more, for example, by a distance from 1 cm to 3 cm, for example, by a distance of 2 cm.

[0053] During operation, the distribution pipe 106 is connected to the evaporation crucible 104 at the flange unit 203. The evaporation crucible 104 is configured to receive the source material to be evaporated and to evaporate the source material. FIG. 2B shows a cross-section through the housing of the evaporation crucible 104. A refill opening is provided, for example, at an upper portion of the evaporation crucible, which can be closed using a plug 222, a lid, a cover or the like for closing the enclosure of evaporation crucible 104.

[0054] An outer heating unit 225 is provided within the enclosure of the evaporation crucible 104. The outer heating unit 225 can extend at least along a portion of the wall of the evaporation crucible 104. According to some embodiments, which can be combined with other embodiments described herein, additionally or alternatively one or more central heating elements can be provided. FIG. 2B shows two central heating elements 226, 228. The first central heating element 226 and the second central heating element 228 can respectively include a first conductor 229 and a second conductor 230 for providing electrical power to the central heating elements 226, 228. [0055] To improve the heating efficiency of the source material within the evaporation crucible, the evaporation crucible 104 can further include a heat shield 227 configured to reflect heat energy provided by the outer heating unit 225 and, if present, by the central heating elements 226, 228, back into the enclosure of the evaporation crucible 104.

[0056] According to some embodiments, heat shields such as heat shield 217 and heat shield 227 can be provided for the evaporation source. The heat shields can reduce energy loss from the evaporation source, which also reduces the overall energy consumed by the evaporation source to evaporate a source material. As a further aspect, particularly for deposition of organic materials, heat radiation originating from the evaporation source, especially heat radiation toward the mask and the substrate during deposition, can be reduced. Particularly for the deposition of organic materials on masked substrates, and even more for display manufacturing, the temperature of the substrate and the mask needs to be precisely controlled. Heat radiation originating from the evaporation source can be reduced or avoided by heat shields such as, for instance, heat shield 217 and heat shield 227.

[0057] These shields can include several shielding layers to reduce the heat radiation to the outside of the evaporation source 20. As a further option, the heat shields may include shielding layers, which are actively cooled by a fluid, such as air, nitrogen, water or other appropriate cooling fluids. According to yet further embodiments described herein, the one or more heat shields can include sheet metals surrounding respective portions of the evaporation source, for instance, surrounding the distribution pipe 106 and/or the evaporation crucible 104. According to embodiments herein, the sheet metals can have thicknesses of 0.1 mm to 3 mm, can be selected from at least one material selected from the group consisting of ferrous metals (SS) and non-ferrous metals (Cu, Ti, Al), and/or can be spaced with respect to each other, for example, by a gap of 0.1 mm or more.

[0058] According to some embodiments described herein and as exemplarily shown with respect to FIG. 2A and FIG. 2B, the evaporation crucible 104 is provided at a lower side of the distribution pipe 106. According to yet further embodiments, which can be combined with other embodiments described herein, a vapor conduit 242 may be provided at the central portion of the distribution pipe 106 or at another position between the lower end of the distribution pipe and the upper end of the distribution pipe.

[0059] FIG. 2C illustrates an example of the evaporation source 20 having a distribution pipe 106 and a vapor conduit 242 provided at a central portion of the distribution pipe. Evaporated source material generated in the evaporation crucible 104 is guided through the vapor conduit 242 to the central portion of the distribution pipes 106. The evaporated source material exits the distribution pipe 106 through a plurality of nozzles 22. The distribution pipe 106 may be supported by a support 102. According to yet further embodiments herein, two or more vapor conduits 242 may be provided at different positions along the length of the distribution pipe 106. The vapor conduits 242 can either be connected to one evaporation crucible or to several evaporation crucibles. For example, each vapor conduit 242 can have a corresponding evaporation crucible. Alternatively, the evaporation crucible 104 can be in fluid communication with two or more vapor conduits 242, which are connected to the distribution pipe 106. [0060] As described herein, the distribution pipe can be a hollow cylinder. The term cylinder can be understood as commonly accepted as having a circular bottom shape and a circular upper shape and a curved surface area or shell connecting the upper circle and the lower circle. According to further additional or alternative embodiments, which can be combined with other embodiments described herein, the term cylinder can further be understood in the mathematical sense as having an arbitrary bottom shape and an identical upper shape and a curved surface area or shell connecting the upper shape and the lower shape. The cylinder does not necessarily need to have a circular cross-section.

[0061] FIG. 3 shows a schematic sectional view of an evaporation source 20 according to embodiments described herein. The evaporation source 20 shown in FIG. 3 includes a distribution pipe 106. According to embodiments described herein, the distribution pipe 106 may extend in a length direction which may be perpendicular to the drawing plane of FIG. 3, particularly in an essentially vertical direction. A plurality of nozzles 22 may be arranged along the length direction of the distribution pipe 106. One nozzle 23 of the plurality of nozzles 22 is schematically illustrated in FIG. 3 as an outlet of the distribution pipe 106. The sectional plane of FIG. 3 intersects through the outlet of the nozzle 23. As is indicated in FIG. 3, evaporated source material may stream from the interior of the distribution pipe 106 through the outlet of the nozzle 23 toward the substrate 10. The nozzle 23 is configured for directing a plume 318 of evaporated source material toward the substrate 10. Further, also the remaining nozzles of the plurality of nozzles 22 (not shown in FIG. 3) are configured to direct a respective plume of evaporated source material toward the substrate 10.

[0062] The evaporation source 20 further includes a shielding device 30 which may be arranged downstream from the plurality of nozzles 22. The shielding device 30 may be configured for guiding the evaporated source material toward the substrate 10 and for individually shaping the plumes of evaporated source material. Accordingly, the shielding device 30 may also be referred to herein as a "shaper shield". The shielding device may be detachably fixed to the distribution pipe 106, e.g. via fixing elements such as screws (not shown in FIG. 3).

[0063] The shielding device 30 includes a plurality of apertures 32 wherein at least one aperture of the plurality of apertures 32 is configured to individually shape the plume of evaporated source material emitted from a single associated nozzle. For example, in FIG. 3, an aperture 33 is configured to individually shape the plume 318 emitted from the nozzle 23, wherein no other plume emitted from a second nozzle propagates through and is shaped by the aperture 33. In other words, the nozzle 23 is the single associated nozzle of the aperture 33.

[0064] In some embodiments, each aperture of the plurality of apertures 32 of the shielding device may be configured to individually shape a single plume of evaporated source material that is emitted from a single associated nozzle. In other words, a separate aperture may be arranged in front of every nozzle of the plurality of nozzles. Accordingly, each plume of evaporated source material emitted from the plurality of nozzles 22 may be individually shaped by an associated aperture of the plurality of apertures. [0065] Individually shaping the plumes of evaporated source material may be beneficial as compared to a shielding device with apertures configured to shape more than one plume at the same time. In particular, individual shaping of the plumes of evaporated source material may lead to increased deposition accuracy and may reduce the shadowing effect provided by a mask. For example, individually shaping the plumes of evaporated source material may lead to smaller plume opening angles with more clearly defined plume flanks. Large impact angles of the plumes on the mask and/or on the substrate can be avoided. Further, the individual plumes can be directed as appropriate.

[0066] In some embodiments, the number of nozzles of the evaporation source may correspond to the number of apertures of the shielding device. For example, a shielding device with ten or more apertures may be arranged in front of a distribution pipe with ten or more nozzles. For example, a shielding device with thirty or more apertures may be arranged in front of three distribution pipes, wherein each distribution pipe includes ten or more nozzles. Whereas in the following description reference is made to the aperture 33 and to the nozzle 23, i.e. the single associated nozzle of the aperture 33, as shown in FIG. 3, the remaining apertures of the plurality of apertures 32 may be correspondingly shaped and arranged with respect to the respective associated nozzles in some embodiments.

[0067] In some embodiments, the aperture may be arranged in front of the associated nozzle, as is shown in FIG. 3. For example, the main emission direction X of the nozzle 23 may correspond to a connection line between the center of the outlet of the nozzle 23 and the center of the aperture 33. The aperture 33 may be configured as a passage 43 for the plume 318 that is surrounded by a circumferential wall 34, wherein the circumferential wall 34 may be configured to block at least a portion of the plume 318 of evaporated source material emitted from the nozzle 23. In some embodiments, the circumferential wall 34 may be configured to block an outer angular portion of the plume 318 of evaporated source material.

[0068] An "aperture" as used herein may refer to an opening or a passage at least partially surrounded by a wall which is configured to shape a single plume of evaporated source material which is guided therethrough, particularly for limiting the maximum opening angle of the plume and for blocking outer angular portions of the plume. In some embodiments, the passage may be entirely surrounded by a circumferential wall such as to shape the plume in every sectional plane which includes the main emission direction X of the associated nozzle. [0069] As is schematically indicated in FIG. 3, the aperture 33 may be configured as the passage for the plume 318 which is surrounded by the circumferential wall 34. The circumferential wall 34 may extend around the main emission direction X of the plume 318 such as to circumferentially shape said plume. In some embodiments, the circumferential wall 34 may extend parallel to the main emission direction X from a base wall 41 of the shielding device 30, wherein the base wall 41 may extend essentially perpendicular to the main emission direction X. The base wall 41 may have an opening 42 for the plume 318 or for an outlet of the nozzle 23 to enter the aperture 33.

[0070] In some embodiments, which may be combined with other embodiments herein, the shielding device may be arranged at a close distance to the distribution pipe 106, e.g. at a distance of 5 cm or less or 1 cm or less in the main emission direction X. Arranging the apertures at a close distance downstream from the nozzles may be beneficial because an individual shaping of the plumes may be possible even if adjacent nozzles of the plurality of nozzles are arranged at a close distance with respect to each other.

[0071] In some embodiments, the nozzle 23 may at least partially protrude into the shielding device 30. In other words, there may be a sectional plane perpendicular to the main emission direction X which intersects both the nozzle and the shielding device. For example, as is shown in FIG. 3, the outlet of the nozzle 23 protrudes into the aperture 33. The nozzle outlet may protrude into the opening 42 in the base wall 41 or into the passage 43 which is surrounded by the circumferential wall 34. This allows for shaping the plume 318 emitted from the nozzle 23 directly downstream from the nozzle outlet such that an adjacent nozzle can be positioned close to the nozzle 23 (see FIG. 4). [0072] In some embodiments, which may be combined with other embodiments described herein, the nozzle 23 is not in direct mechanical contact with the shielding device 30. For example, the nozzles may protrude into the apertures at a distance from the aperture walls, as is indicated in FIG. 3. Avoiding direct contact between the nozzles and the shielding device may have the effect of a thermal decoupling between the nozzles and the shielding device. A direct thermal conduction between the typically hot nozzles and the shielding device can be avoided such that a thermal radiation toward the substrate from the shielding device can be reduced.

[0073] The minimum distance between the nozzle 23 and the shielding device 30 may be less than 3 mm or less than 1 mm and/or more than 0.1 mm in some embodiments. As the evaporation source may be arranged in sub-atmospheric pressure, a heat flow between the nozzles and the shielding device may be substantially reduced.

[0074] In some embodiments, the shielding device 30 may be actively or passively cooled. A heat flow between the cooled shielding device 30 and the nozzles can be reduced by thermally decoupling the plurality of apertures from the plurality of nozzles.

[0075] In some embodiments, which may be combined with other embodiments described herein, the circumferential wall 34 may be configured to block the evaporated source material of the plume 318 of evaporated source material having an emission angle greater than a first maximum emission angle Θ with respect to the main emission direction X in a first sectional plane.

[0076] The drawing plane of FIG. 3 illustrates the first sectional plane. The first sectional plane may include the main emission direction X. In some embodiments, the first sectional plane is a horizontal plane and/or a plane that extends perpendicularly to the length direction of the distribution pipe 106. As is depicted in FIG. 3, the circumferential wall 34 of the aperture 33 is configured to block an outer angular portion of the plume 318 of evaporated source material in the first sectional plane such that the opening angle of the emission cone is limited to an angle of 2Θ. In other words, the circumferential wall 34 blocks the portion of the evaporated source material emitted by the nozzle 23 at an emission angle greater than the first maximum emission angle Θ. [0077] In some embodiments, the first maximum emission angle Θ is an angle from 10° to 45°, particularly from 20° to 30°, more particularly about 25°. Accordingly, the opening angle 2Θ of the emission cone in the first sectional plane may be 20° or more and 90° or less, particularly about 50°. As is indicated in FIG. 3, the shadowing effect due to the mask 340 can be reduced by reducing the first maximum emission angle Θ.

[0078] In some embodiments, which may be combined with other embodiments described herein, the circumferential wall 34 may be configured to block the evaporated source material of the plume 318 of evaporated source material having an emission angle greater than a second maximum emission angle with respect to the main emission direction X in a second sectional plane perpendicular to the first sectional plane.

[0079] The second sectional plane may be a plane perpendicular to the drawing plane of FIG. 3. The second sectional plane may include the main emission direction X. In some embodiments, the second sectional plane is a vertical plane and/or a plane that extends parallel to the length direction of the distribution pipe 106. The circumferential wall 34 of the aperture 33 may be configured to block an outer angular portion of the plume 318 of evaporated source material in the second sectional plane such that the opening angle of the emission cone is limited to an angle of 2β. In other words, the circumferential wall 34 may block the portion of the evaporated source material emitted by the nozzle 23 at an emission angle greater than the second maximum emission angle in the second sectional plane. [0080] In some embodiments, the second maximum emission angle is an angle from 10° to 60°, particularly from 30° to 40°, more particularly about 45°. Accordingly, the opening angle of the emission cone in the second sectional plane may be 20° or more and 120° or less, particularly about 90°. The shadowing effect due to the mask 340 in a plane perpendicular to the drawing plane of FIG. 3 can be reduced by reducing the second maximum emission angle Θ.

[0081] In some embodiments, the second maximum emission angle is an angle different from the first maximum emission angle, particularly an angle larger than the first maximum emission angle. This is because a larger maximum emission angle may be possible in the length direction of the distribution pipe 106. In particular, in the length direction of the distribution pipe adjacent nozzles are typically configured to emit the same evaporation material, and the spacing of adjacent nozzles along the distribution pipe can be adjusted more easily. On the other hand, nozzles which are adjacent to each other in a direction perpendicular to the length direction of the distribution pipe may be configured to emit different materials such that accurately setting the overlap of the plumes of adjacent nozzles may be beneficial. [0082] The first sectional plane may be a horizontal plane, the first maximum emission angle may be from 20° to 30°, the second sectional plane may be a vertical plane, and the second maximum emission angle may be from 40° to 50°.

[0083] In some embodiments, a distance between two adjacent nozzles in the length direction of the distribution pipe 106 may be from 1 cm to 5 cm, particularly from 2 cm to 4 cm. Accordingly, the distance between two adjacent apertures of the plurality of apertures, i.e. the distance between the respective aperture centers, may be from 1 cm to 5 cm, particularly from 2 cm to 4 cm. For example, the distance between two adjacent apertures may correspond to the distance between the two adjacent associated nozzles, respectively.

[0084] In some embodiments, which may be combined with other embodiments described herein, the aperture 33 is configured as a round passage 43 for the plume 318 surrounded by a circumferential wall 34. A "round passage" may be understood as a passage with a rounded contour, e.g. a curved contour, a circular contour, or an oval contour, in a sectional plane perpendicular to the main emission direction X. For example, the circumferential wall 34 may have a circular or an oval shape in a sectional plane perpendicular to the main emission direction X.

[0085] A circular passage may shape the plume 318 such as to be rotationally symmetric with respect the main emission direction. An oval passage may shape the plume 318 such as to have a large opening angle in a first sectional plane corresponding to the major axis of the oval passage and to have a small opening angle in a second sectional plane corresponding to the minor axis of the oval passage. The major axis of the oval passage may be arranged in the vertical direction, and the minor axis of the oval passage may be arranged in the horizontal direction.

[0086] The circumferential wall 34 may form a circle in a sectional plane perpendicular to the main emission direction X. The diameter of the circle, i.e. the inner diameter of the passage, may be 3 mm or more and 25 mm or less, particularly 5 mm or more and 15 mm or less. The diameter of the passage may be measured at a downstream end of the passage which defines the maximum opening angle of the plume 318.

[0087] In some embodiments, the length of the circumferential wall 34 in the main emission direction X may be constant. In other embodiments, which may be combined with other embodiments described herein, the aperture 33 may be configured as a passage 43 for the plume 318 surrounded by a circumferential wall 34, wherein a length of the circumferential wall in a main emission direction X varies in a circumferential direction. More particularly, the front end 35 of the circumferential wall 34 which is directed toward the substrate may have a distance from the nozzle outlet that varies in the circumferential direction. By providing a varying length of the circumferential wall in the circumferential direction, the opening angle of the plume 318 may be configured to be different in various sectional planes.

[0088] As is illustrated in FIG. 3, the circumferential wall 34 may have a first length Tl in a first sectional plane which includes the main emission direction X, and the circumferential wall may have a second length T2 smaller than the first length Tl in a second sectional plane which includes the main emission direction X and extends perpendicular to the first sectional plane. The first sectional plane may be perpendicular to the length direction of the distribution pipe, e.g. a horizontal plane. The second sectional plane may be parallel to the length direction of the distribution pipe, e.g. a vertical plane.

[0089] The length of the circumferential wall may vary continuously from the first length Tl in the first sectional plane to the second length T2 in the second sectional plane. In other words, the front end 35 of the circumferential wall 34 may include no step and no discontinuity in the circumferential direction. Accordingly, the opening angle of the plume 318 may vary gradually in the circumferential direction. Deposition accuracy may be improved. [0090] In some embodiments, the first length Tl may be a length between 8 mm and 20 mm, particularly about 12 mm, and/or the second length T2 may be a length between 3 mm and 15 mm, particularly about 6.5 mm. The "length" of the circumferential wall may correspond to the length of a projection of a vector connecting the nozzle outlet and the front end of the circumferential wall in a respective sectional plane on the main emission direction X. [0091] Pixels with sharp edges may be deposited on the substrate, when the front end 35 of the circumferential wall has a wave-like or undulating shape in a circumferential direction. Wave crests may be positioned in the first sectional plane, i.e. the drawing plane of FIG. 3, and wave bases may be arranged in the second sectional plane, i.e. a plane perpendicular to the first sectional plane. The front end 35 of the circumferential wall 34 may include two wave crests and two wave bases, as is indicated in FIG. 3.

[0092] In some embodiments, the at least one aperture may have a diameter of 3 mm or more and 25 mm or less, particularly 5 mm or more and 15 mm or less. Therein, the diameter of the aperture may be measured at the front end 35 of the aperture which defines the maximum emission angle of the plume 318 propagating toward the substrate 10.

[0093] The walls of the distribution pipe may be heated by heating elements, which are mounted or attached to the walls of the distribution pipe. For reducing the heat radiation toward the substrate, an outer shield which surrounds the heated inner wall of the distribution pipe may be cooled. An additional second outer shield may be provided to further reduce the heat load directed toward the deposition area or the substrate, respectively. According to some embodiments, which can be combined with other embodiments described herein, the shields can be provided as metal plates having conduits for cooling fluid, such as water, attached to the metal shields or provided within the metal shields. Additionally, or alternatively, thermoelectric cooling devices or other cooling devices can be provided to cool the shields. Accordingly, the interior of the distribution pipe can be kept at a high temperature, e.g. higher than the evaporation temperature of the source material, whereas the heat radiation toward the deposition area and toward the substrate can be reduced.

[0094] FIG. 4 shows an evaporation source 20 according to embodiments described herein including a distribution pipe 106, a second distribution pipe 107, and a third distribution pipe 108 which extend next to each other in a length direction, respectively, wherein the length direction is perpendicular to the drawing plane of FIG. 4. The evaporation source 20 includes a plurality of nozzles 22 wherein one nozzle of each of the distribution pipes is schematically depicted as an outlet of the respective distribution pipe in FIG. 4. Further, the evaporation source 20 includes a shielding device 30 including a plurality of aperture 32, wherein each aperture of the plurality of apertures 32 is arranged in front of a single associated nozzle and is configured to shape the plume of evaporated source material emitted from the respective single associated nozzle. [0095] The apertures may be configured and arranged in analogy to the aperture 33 shown in FIG. 3 so that reference can be made to the above explanations which are not repeated here.

[0096] In particular, in some embodiments, the nozzles may protrude into an aperture, respectively, without contacting the aperture. Thus, the shielding device 30 may be thermally decoupled from the plurality of nozzles 22 and/or from the distribution pipes. Heat radiation toward the substrate can be reduced.

[0097] In some embodiments, which may be combined with other embodiments described herein, the shielding device may include a plurality of separate shielding units 60 arranged next to each other, wherein each shielding unit of the plurality of separate shielding units 60 comprises one or more apertures of the plurality of apertures 32.

[0098] "Separate" shielding units as used herein may refer to two or more shielding units which are not in direct contact with each other and which are provided as separate components without a direct mechanical connection. As is indicated in FIG. 4, the shielding units of the plurality of separate shielding units 60 are not in direct contact with each other. For example, the separate shielding units may be separately fixed to a respective distribution pipe with one or more respective fixing elements.

[0099] In some embodiments, each shielding unit of the plurality of separate shielding units 60 may include a single aperture of the plurality of apertures 32. Each aperture may be configured as a passage surrounded by a shielding wall configured for shaping a single plume of evaporated source material.

[00100] In other embodiments, at least one shielding unit of the plurality of separate shielding units 60 includes two, three, four, five or more apertures of the plurality of apertures 32, which may be connected to each other by a support structure, for example in a linear arrangement. A distance between two adjacent apertures of the at least one shielding unit may be 1 cm or more and 5 cm or less, respectively.

[00101] In some embodiments, each shielding unit of the plurality of shielding units may include two or more apertures of the plurality of apertures. Mounting of the shielding device 30 to the distribution pipes can be facilitated when the number of shielding units of the shielding device is reduced. Accordingly, increasing the number of apertures per shielding unit may be beneficial. [00102] In some embodiments, the number of apertures per shielding unit is 10 or less, particularly 5 or less. The shielding units may follow a local thermal expansion and contraction of one of the distribution pipes more easily, when the shielding units do not extend over a substantial length. In particular, adjacent shielding units may move relative to one another when one of the distribution pipe expands or contracts.

[00103] It is indicated in FIG. 4 that the shielding unit connected to the distribution pipe 106 is mechanically decoupled from the remaining shielding units such as to be movable relative to the remaining shielding units. For example, the temperature of the distribution pipe 106 may vary differently from the temperature of the second distribution pipe 107 and from the temperature of the third distribution pipe 108 such that the distribution pipes may slightly move relative to each other during deposition. The shielding units may follow the movement of the respective distribution pipe, because the shielding units are mechanically decoupled from the remaining shielding units, respectively. Accordingly, the plumes of evaporated source material may be shaped in a stable way even when the distribution pipes move relative to each other or when one of the distribution pipes thermally expands or contracts. The one or more apertures of a shielding unit may follow the movement of the one or more associated nozzles, respectively.

[00104] In some embodiments, each shielding unit of the plurality of separate shielding units 60 may be mechanically decoupled from the remaining shielding units of the plurality of separate shielding units such as to not follow a thermally caused movement of the remaining shielding units.

[00105] In some embodiments, which may be combined with other embodiments described herein, at least one shielding unit of the plurality of separate shielding units 60 may be connected to a single distribution pipe such as to follow a thermal expansion and contraction of the single distribution pipe in a length direction of the single distribution pipe, particularly such as to move with respect to a further shielding unit connected to the single distribution pipe when the single distribution pipe thermally contracts or expands.

[00106] The main emission direction of the nozzles of the distribution pipe 106 may be inclined with respect the main emission direction of the nozzles of the second distribution pipe 107 and/or of the third distribution pipe 108. For example, the main emission directions may be inclined such that the plumes of evaporated source material emitted from the distribution pipe 106 may overlap with the plumes of evaporated source material emitted from the second distribution pipe 107 and/or from the third distribution pipe 108. In some embodiments, the distribution pipes are arranged such that main emission directions of the distribution pipes may intersect essentially on the surface of the substrate. The plumes emitted from different distribution pipes in a sectional plane may be directed to essentially the same area on the substrate.

[00107] In some embodiments, one of the distribution pipes, e.g. distribution pipe 106, may be configured to deposit a main material, and at least one further distribution pipe, e.g. the second distribution pipe 107, may be configured to deposit a secondary material, e.g. a dopant.

[00108] FIG. 5 shows an evaporation source 20 according to embodiments described herein in a sectional view, wherein the sectional plane extends in the length direction of the distribution pipe 106. The length direction of the distribution pipe may be a vertical direction.

[00109] In some embodiments, a second distribution pipe 107 and/or a third distribution pipe 108 may run essentially parallel to the distribution pipe 106 on both sides of the distribution pipe 106, as is shown in FIG. 4.

[00110] The distribution pipe 106 includes a plurality of nozzles 22 which are arranged next to each other in the length direction of the distribution pipe. A first nozzle 402 and a second nozzle 404 of the plurality of nozzles are shown in FIG. 5. A first plume 403 of evaporated source material is emitted by the first nozzle 402, and a second plume 405 of evaporated source material is emitted by the second nozzle 404.

[00111] A shielding device 30 is arranged downstream from the plurality of nozzles to shape the plumes of evaporated source material emitted from the plurality of nozzles. The shielding device 30 may include a plurality of individual shielding units, wherein one shielding unit 61 of the plurality of shielding units is depicted in FIG. 5.

[00112] The shielding unit 61 includes a first aperture 406 and a second aperture 408 which may be configured according to any of the above described embodiments. The first aperture 406 is configured to individually shape the first plume 403 emitted from the first nozzle 402, and the second aperture 408 is configured to individually shape the second plume 405 emitted from the second nozzle 404. [00113] The shielding unit 61 may include more than two apertures of the plurality of apertures, e.g. three, four, or five apertures, in a linear arrangement. The apertures may be connected by a support structure, e.g. a plate element. The apertures of the shielding unit 61 may be configured for individually shaping the plumes of evaporated source material of three, four or five adjacent nozzles which are provided next to each other along the length direction of the distribution pipe 106.

[00114] The distribution pipe may include 10 or more nozzles provided in a linear arrangement. Accordingly, more than one shielding unit, e.g. two, three or more shielding units may be fixed to the distribution pipe in a linear arrangement. [00115] Each shielding unit of the plurality of separate shielding units may be mechanically fixed to a single distribution pipe of the two or more distribution pipes of the evaporation source. The shielding units may be mechanically and/or thermally decoupled from one another such that a relative movement between the individual shielding units may be possible. Accordingly, the shielding units may move relative to one another when the distribution pipe the shielding units are fixed to extends or contracts.

[00116] The shielding unit 61 may be fixed to the distribution pipe 106 such as to be thermally decoupled from the distribution pipe 106. For example, the shielding unit 61 may be held at a distance from the distribution pipe 106 by one or more spacer elements 411 which may be arranged between the shielding unit and the distribution pipe. The spacer elements 411 may be configured as support sections arranged between the nozzles of the distribution pipe. The spacer elements 411 may provide a small contact area, in order to reduce a heat flow from the distribution pipe 106 toward the shielding unit 61. For example, the contact area of a spacer element 411 may be 1 mm ² or less, particularly 0.25 mm ² or less. The shielding unit 61 may be fixed to the distribution pipe 106 via one or more fixing elements, e.g. screws, which may be made of a material with low heat conductivity.

[00117] The length of the shielding unit 61 in the length direction of the distribution pipe may be 20 cm or less, particularly 10 cm or less. Due to the small length of the shielding units, the shielding units may follow a thermally caused local movement, e.g. an expansion or contraction movement, of the distribution pipe 106. For example, a first shielding unit fixed to the distribution pipe may move away from a second shielding unit fixed to the same distribution pipe, when the distribution pipe expands. The first shielding unit fixed to the distribution pipe may move toward the second shielding unit fixed to the same distribution pipe, when the distribution pipe contracts.

[00118] In some embodiments, which may be combined with other embodiments described herein, the shielding unit 61 is rigidly fastened to the distribution pipe at a single fixing portion along the length direction of the shielding unit, e.g. at a center portion of the shielding unit. At further positions, the shielding unit 61 may be fixed to the distribution pipe 106 such as to allow a relative movement between the shielding unit and the distribution pipe. For example, in the embodiment shown in FIG. 5, the first end portion 412 of the shielding unit 61 and the second end portion 413 of the shielding unit 61 may be movably fixed to the distribution pipe, e.g. via a fixing element such as a screw penetrating through a slotted hole that may be provided in the shielding device. In some embodiments, the slotted hole may provide a clearance between the distribution pipe and the shielding unit in the length direction of the shielding unit of more than 0.01 mm and less than 0.5 mm, for example about 0.1 mm.

[00119] FIG. 6 shows a shielding device 500 for an evaporation source according to embodiments described herein in a perspective view. The shielding device is configured as a single component and does not include a plurality of separate shielding units. The shielding device 500 includes a plurality of apertures, wherein each aperture of the plurality of apertures is configured as a passage surrounded by a shielding wall, wherein each aperture of the plurality of apertures is configured to individually shape a plume of evaporated source material emitted from a single associated nozzle of the evaporation source.

[00120] The shielding device 500 is configured to be attached to an evaporation source with three distribution pipes. Accordingly, the shielding device 500 includes three vertically arranged columns of apertures provided next to each other in a support structure, e.g. a plate element. The apertures of the central column of apertures may be offset with respect to the apertures of the outer columns. This allows for a more compact arrangement of the three distribution pipes next to each other.

[00121] The apertures are provided as oval passages, respectively. Accordingly, the first maximum emission angle of the plumes of evaporated source material exiting the apertures in the vertical direction is larger than the second maximum emission angle of the plumes of evaporated source material exiting the apertures in the horizontal direction. [00122] FIG. 7 shows a shielding unit 600 of a shielding device for an evaporation source according to embodiments described herein in a perspective view. A shielding device according to embodiments described herein may include a plurality of separate shielding units 600, for example three or more, particularly 12 or more shielding units 600. [00123] The shielding unit 600 may include two or more apertures and/or ten or less apertures, particularly five apertures. Each aperture may be configured as a passage surrounded by a shielding wall, e.g. a circumferential wall. Round passages, particularly circular passages may be space-saving and easy to manufacture. Round passages may have the further advantage that the evaporated source material may impact on the shielding wall at the same impact angles in the circumferential direction due to the rotational symmetry. Evaporated source material may uniformly accumulate on the shielding wall in the circumferential direction during deposition. Cleaning of the shielding unit may become easier.

[00124] The apertures of the shielding unit 600 may be arranged in a linear arrangement with a distance of 1 cm or more and 5 cm or less, particularly about 2 cm, between adjacent apertures. The shielding unit 600 may be configured as a one-piece component, wherein the apertures may be connected by a support structure 612, e.g. an elongate plate element. The shielding unit 600 may have a width of 3 cm or less, 2 cm or less, or even 1 cm or less.

[00125] The support structure 612 may include one or more holes at a first end 613 and one or more holes at a second end 614 opposite to the first end 613 for fixing the shielding unit to a distribution pipe, e.g. via screws of bolts. In some embodiments, further holes may be provided between the apertures, respectively.

[00126] Each aperture of the shielding unit 600 may be configured to individually shape a plume of evaporated source material emitted from a single associated nozzle of the evaporation source. [00127] In some embodiments described herein, the apertures of the shielding unit 600 may have a diameter between 3 mm and 25 mm, particularly between 5 mm and 15 mm, respectively. A small diameter of the apertures of the shielding unit may improve the deposition accuracy. However, a small aperture diameter tends to clog more easily, which may deteriorate the deposition efficiency and deposition uniformity. [00128] Embodiments of operating an evaporation source described herein are provided for maintaining high deposition accuracy over a long time period, while at the same time preventing clogging of the apertures can be.

[00129] A method of operating an evaporation source 20 is described with reference to FIG. 5 8 A and FIG. 8B.

[00130] The method described herein includes depositing an evaporated source material on a substrate 10, as is illustrated in FIG. 8 A. Deposition of the evaporated source material includes guiding the evaporated source material toward the substrate 10 in a main emission direction X, wherein part of the evaporated source material is blocked by the shielding device 10 30 arranged between the plurality of nozzles and the substrate 10 for individually shaping the plumes of evaporated source material.

[00131] During deposition, the shielding device 30 may be kept at a first temperature, which may be a low temperature, e.g. a temperature below 150°C, particularly a temperature of 100°C or less, or 50°C or less. For example, the surface of the shielding device which faces 15 toward the substrate may be kept at a temperature of 100°C or less during deposition, in order to reduce a radiation of heat toward the mask and/or toward the substrate. In some embodiments, the shielding device 30 may be actively or passively cooled during deposition, e.g. via cooling channels or via a thermoelectric cooling device attached to the shielding device. 0 [00132] As the surface of the shielding device 30 may be kept at a low temperature, the evaporated source material which is blocked by the shielding device may condensate on the shielding device and attach thereto. The aperture diameter may become smaller, and there may be a risk of clogging.

[00133] According to methods described herein, the deposition phase illustrated in FIG. 8A 5 may be followed by a cleaning phase illustrated in FIG. 8B, wherein at least part of the source material accumulated on the shielding device 30 is removed from the shielding device by heating the shielding device to a second temperature, which is above the first temperature. The shielding device may be heated at least locally, particularly at surface sections of the shielding device with accumulated source material. For example, the shielding walls 30 surrounding the plurality of apertures 32 of the shielding device may be heated because some of the evaporated source material is typically blocked by the shielding walls surrounding the apertures.

[00134] In some embodiments, the shielding device may be at least locally heated to a temperature above an evaporation temperature of the source material during cleaning, e.g. to a temperature above 100°, or above 200°, particularly to a temperature of 300°C or more. The attached source material can be released from the shielding device and re-evaporate. Accordingly, the shielding device can be cleaned.

[00135] In some embodiments, the shielding device 30 faces toward the substrate 10 during deposition, whereas the shielding device 30 does not face toward the substrate 10 during heating. Accordingly, deposition of the re-evaporated source material from the shielding device on the substrate can be avoided. Further, thermal expansion of the mask and/or of the substrate due to heat radiation from the heated shielding device can be avoided.

[00136] In some embodiments, which may be combined with other embodiments described herein, the emission of evaporated source material through the nozzles can be stopped during cleaning. For example, the nozzles may be closed or evaporation may be stopped during the cleaning phase II. The consumption of source material can be reduced.

[00137] In some embodiments, which can be combined with other embodiments described herein, the deposition apparatus may be set into a service position II for cleaning. In particular, after deposition, the deposition apparatus may be brought from a deposition position I, in which the apertures of the shielding device are directed toward the substrate 10, into the service position II, in which the apertures of the shielding device are not directed toward the substrate.

[00138] A "deposition position" as used herein may be a state of the deposition apparatus in which the deposition apparatus is ready for guiding evaporated source material toward a substrate. For example, the nozzles of the evaporation source and the apertures of the shielding device may face toward the substrate or toward the deposition area of the deposition apparatus.

[00139] A "service position" as used herein may be a state of the deposition apparatus which is not suitable for guiding evaporated source material toward the substrate. For example, the nozzles of the evaporation source and the apertures of the shielding device may not face toward the substrate or toward the deposition area of the deposition apparatus. Setting the deposition apparatus from the deposition position into the service position may include a movement of the evaporation source, e.g. a rotational movement. In some embodiments, setting the deposition apparatus into the service position may include moving the evaporation source into a position, in which a heating device 50 is provided to heat the shielding device and/or in which the shielding device faces toward a material collection unit 40 such as a shielding wall.

[00140] In some embodiments, setting the deposition apparatus into the service position II may include a relative movement between the evaporation source 20 and the material collection unit 40. For example, in the embodiment shown in FIG. 8A and FIG. 8B, the evaporation source 20 is moved from the deposition position I shown in FIG. 8A to the service position II shown in FIG. 8B, wherein the shielding device 30 is directed toward the material collection unit 40 in the service position II.

[00141] Moving the evaporation source to the service position II may include rotating the evaporation source 20 by a rotation angle, particularly by a rotation angle a of 20° or more, more particularly by a rotation angle from 60° to 120°. In the embodiment shown in FIG. 8B, the evaporation source is rotated by a rotation angle of approximately 90° from the deposition position I to the service position II.

[00142] The shielding device 30 may be heated in the service position II, in which the shielding device 30 faces toward the material collection unit 40. The material collection unit 40 may be provided as a wall element, e.g. a condensation wall or a shielding wall. As is indicated in FIG. 8B, the wall element may by curved. A distance between the wall element and the shielding device can be kept essentially constant during the rotation movement of the evaporation source. Further, due to the curved shape of the wall element, the wall element may act as a shield that blocks evaporated source material emitted from the evaporation source 20 essentially during the entire rotational movement of the evaporation source 20. For example, the wall element may extend over an angle of 45° or more, particularly 90° or more, with respect to the rotation axis of the evaporation source.

[00143] In some embodiments, cleaning may comprise heating the shielding device for a time period of 1 second or more, particularly 10 seconds or more. A longer heating period may lead to a better cleaning result but may slow down the evaporation process. Good cleaning results can be achieved by heating over a time period between 1 second and 60 seconds.

[00144] After cleaning, deposition of the evaporated source material on the substrate or on a further substrate may continue. Before continuing with the deposition, in some embodiments, the evaporation source may be brought from the service position II back to the deposition position I or to a further deposition position. For example, the evaporation source may be rotated by the angle (-a) back to the deposition position I, or alternatively, the evaporation may be brought to a further deposition position by further rotating the evaporation source in the same rotation direction, e.g. by another angle a. [00145] In some embodiments, which may be combined with other embodiments described herein, deposition and cleaning may be alternately performed. For example, the shielding device may be cleaned after a predetermined deposition period, respectively, and, after cleaning, deposition may continue, respectively. In some embodiments, cleaning of the shielding device may be performed after deposition of evaporated source material on every substrate, or after having coating a predetermined number of substrates, e.g. after having coated 2 substrates, 4 substrates or more substrates. In some embodiments, cleaning of the shielding device may be performed after several minutes, hours or days of deposition operation, respectively. The time period, after which cleaning is performed, may depend on the size and shape of the apertures of the shielding device, on the distance between the outlets of the evaporation source and the shielding device, as well as on the temperature of the surface of the shielding device during deposition. For example, cleaning may be performed after deposition of evaporated material on each substrate or after a deposition period of up to several hours, respectively.

[00146] In some embodiments, the accumulation of source material on the shielding device may be measured, and cleaning may be performed after having reached a predetermined accumulation. Clogging of the apertures of the shielding device can be prevented and a constant plume of evaporated source material impacting on the substrate can be obtained.

[00147] In order to reduce a heat load on the substrate by the heated shielding device, the shielding device may be allowed to cool down after the cleaning. For example, the shielding device may be cooled down to the first temperature, e.g. a temperature of 150°C or less, or 100° or less, after cleaning and before continuing deposition. In some embodiments, a heating device 50 which is configured for heating the shielding device during cleaning is switched off for a predetermined period before continuing deposition. In some embodiments, the shielding device is passively or actively cooled after the cleaning and/or before continuing deposition. Further, the shielding device may additionally or alternatively be passively or actively cooled during deposition. Passive cooling may comprise cooling via a cooling fluid. Active cooling may comprise cooling via an active cooling element, e.g. a thermoelectric cooling element, a Peltier element or a piezoelectric cooling element.

[00148] FIG. 10 is a flow diagram which illustrates a method for depositing an evaporated source material on a substrate 10 in a vacuum chamber. In box 1010, an evaporated source material is guided through a plurality of nozzles of one or more distribution pipes of an evaporation source, wherein each of the plurality of nozzles generates a plume of evaporated source material propagating toward the substrate. In box 1020, the plumes of evaporated source material are individually shaped by a plurality of apertures of a shielding device.

[00149] Shaping the plumes may include blocking at least a portion of the plumes using the apertures. Over time, evaporated source material may attach to the apertures, which may lead to a reduction of a diameter of the apertures.

[00150] In optional box 1030, the shielding device is cleaned by at least locally heating the shielding device in a service position of the deposition apparatus. Heating may lead to a re- evaporation of the accumulated source material from the shielding device. After cleaning, deposition may continue.

[00151] In some embodiments, cleaning is performed at regular intervals.

[00152] 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 they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.