FOR EVAPORATION PURPOSES

TECHNICAL FIELD

[0001] The present disclosure generally relates to evaporators, crucibles, the deposition of source materials and to systems, apparatuses and methods for depositing materials, e.g. organic materials. In particular, the present disclosure relates to evaporation crucibles for organic materials, e.g. for use with evaporation assemblies in deposition systems for manufacturing devices, particularly devices including organic materials therein.

BACKGROUND

[0002] Organic evaporators are tools, e.g. 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, other hand-held devices, etc., for displaying information. OLEDs can also be used for general space illumination. The ranges of colors, brightness, and viewing angle possible with OLED displays are greater than that of traditional LCD displays because OLED pixels directly emit light and do not use a back light. Therefore, the energy consumption of OLED displays is less than that of traditional LCD displays. Further, the fact that OLEDs can be more easily 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 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] One stage in the manufacturing of OLED displays or OLED lighting applications, which brings about various challenges, is the process of depositing organic materials to achieve a high grade of layer uniformity on the substrate. Further, it has to be considered that there are certain conditions for the evaporation of the, e.g., sensitive organic materials, which are for example evaporated in vacuum and deposited on the substrate. [0004] Therefore, there is a continuous need for new and improved systems, apparatuses and methods for forming devices such as high quality OLED display devices.

SUMMARY

[0005] In view of the above, according to an aspect, a crucible is provided. The crucible includes: A wall with an inner surface surrounding an inner volume for receiving the source material and one or more heat transfer elements arranged within the inner volume of the crucible.

[0006] Further, an evaporation assembly for vaporizing a source material is provided. The evaporation assembly includes: A crucible as described above and at least one distribution assembly adapted for guiding vaporized source material from the crucible to a substrate to be coated.

[0007] Furthermore, a method is provided for coating a substrate with a source material evaporated from a crucible having a wall with an inner surface surrounding an inner volume for receiving the source material and including at least one heat transfer element within the inner volume of the crucible. The method includes: Providing a source material within the crucible; heating the source material to an evaporation temperature by providing an indirect heating of the inner volume of the crucible with the at least one heat transfer element; and guiding evaporated source material to a surface of the substrate.

[0008] Further aspects, advantages and features of the present disclosure are apparent from the dependent claims, the description and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Some of the above mentioned embodiments will be described in more detail in the following description of typical embodiments with reference to the following drawings in which: Fig. 1 shows a schematic view of a crucible according to embodiments described herein; Fig. 2 shows a schematic view of a further crucible according to embodiments described herein;

Fig. 3 shows a schematic view of yet a further crucible according to embodiments described herein; Fig. 4 shows a cross-sectional perspective view of the crucible shown in Fig. 2 according to embodiments described herein;

Fig. 5 shows a schematic view of another crucible according to embodiments described herein;

Fig. 6 shows a schematic view of another crucible according to embodiments herein;

Fig. 7 shows a schematic view of an evaporation assembly according to embodiments herein;

Fig. 8 and Fig. 9 show schematic views of portions of an evaporation assembly according to embodiments herein; Fig. 10 shows a schematic view of a deposition system for depositing a source material according to embodiments herein; and

Fig. 11 shows schematically a method for coating a substrate with a source material evaporated from a crucible according to embodiments herein.

DETAILED DESCRIPTION [0010] 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 same components. Generally, 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.

[0011] According to embodiments herein, techniques of OLED production include the deposition of source materials, such as for example organic materials, on a substrate. The deposition process is performed under high vacuum conditions. A crucible containing the organic material is heated to evaporate the organic material and the resulting vapor is deposited on the substrate. It is beneficial to closely monitor and control the evaporation process since non-uniform evaporation may lead to the deposition of evaporated particles detrimental to the uniformity of the film deposited on the substrate. In order to better regulate the deposition rate, it may be beneficial to evaporate the organic material smoothly by slowly increasing the temperature to the evaporation temperature of the organic material in the evaporation crucible.

[0012] In the embodiments described herein, the term "evaporation" as used herein shall refer to both the process of evaporation from liquid to vapor and sublimation from solid to vapor.

[0013] The inventors of the present disclosure have found that non-uniform heat input to the source material may occur in conventional crucibles, which results in unequal mass evaporation of the source material inside of the crucible. Unequal mass evaporation may have a negative impact on the uniformity of the film deposited on the substrate and may degrade the overall quality of a produced device.

[0014] The present disclosure addresses these issues by providing improved systems, apparatuses and methods for uniformly depositing source materials, such as for example organic materials onto a substrate and to improve the efficiency of source material consumption. In particular, the present disclosure provides improved crucibles for use with evaporation assemblies in deposition systems for manufacturing devices. For example, according to embodiments herein, the crucible containing a source material may include one or more heat transfer elements that are configured to homogenously redistribute the heat applied to the crucible within an inner volume of the crucible. A homogenous heating of the inner volume of the crucible improves a homogenous evaporation of the source material within the crucible and may contribute to the overall uniformity of the layer(s) deposited during a coating or device manufacturing process.

[0015] Fig. 1 illustrates an embodiment of a crucible 100, including a wall with an inner surface surrounding an inner volume 150 for receiving a source material according to an embodiment herein. The crucible shown in Fig. 1 is illustrated as two halves, which are mirror symmetrical with respect to a plane of symmetry 101. According to embodiments described herein, the crucible may be part of an evaporation assembly that may further include one or more distribution assemblies. The one or more distribution assemblies may, for instance, include one or more distribution pipes with outlets (e.g. nozzles), which guide the evaporated source material from the crucible to the substrate. According to the embodiment shown in Fig. 1, the crucible 100 and the distribution pipe may be connected to each other via a connector 103, e.g. providing a form-fit connection. In embodiments herein, the connection between the crucible and distribution pipe may additionally or alternatively include a flange unit. According to embodiments herein, the 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 assembly.

[0016] According to embodiments herein, the wall of the crucible 100 may include a bottom wall 167 and a top wall 168. The bottom wall and top wall 167, 168 may be connected to each other via side walls 161-166. The inner volume 150 of the crucible 100 may be enclosed by the bottom wall 167, the top wall 168 and the side walls 161-166, or respective portions of a side wall, respectively. According to embodiments herein, at least the top wall 168 may include an opening 104 which allows evaporated source material to exit from the crucible and enter, for instance, a distribution assembly. In particular, the opening of the crucible may be connected to a distribution pipe, which guides the evaporated source material to a substrate.

[0017] According to the embodiment shown in Fig. 1, an outer heating unit 125 may be provided at or in the wall of the crucible 100. In embodiments described herein, the heating unit may, for example, be one or more heaters. The outer heating unit may extend at least along a portion of the wall of the crucible 100. According to some implementations herein, the crucible 100 may further include a shield 127. The shield 127 may be configured to reflect heat energy, which is provided by the outer heating unit 125 back towards the enclosure of the crucible 100. According to embodiments herein, the shield may support an efficient heating of the organic material within the inner volume 150 of the evaporation crucible 100.

[0018] According to some embodiments described herein, the one or more heating units provided around at least a portion of the crucible are not extending into the inner volume of the crucible. According to the embodiments described herein, a maximum of 3% to 10%, such as for example, 5% of the total heating power provided to evaporate the source material, which is contained within the crucible, is generated within the inner volume of the crucible. Providing a heating unit within the inner volume of the crucible may interfere with the temperature regulation of the heating unit provided on the outside, around at least a portion of the crucible.

[0019] According to some embodiments described herein, the distribution pipe may also include a heating unit, which facilitates a precise temperature control of the evaporated material guided from the crucible to the substrate. One or more heat shields may also be provided around the distribution pipe. The one or more heat shields may reduce the energy loss from the evaporation assembly, which may reduce the overall energy consumption during a coating/manufacturing process. As a further aspect, particularly for deposition of organic materials, heat radiation originating from the evaporation assembly may be reduced, particularly heat radiation towards the substrate during deposition. For display manufacturing, precise control of the temperature of the substrate and mask is particularly beneficial. By employing one or more heat shields, the heat radiation originating from the evaporation assembly can be reduced or avoided. Accordingly, some embodiments described herein include one or more heat shields.

[0020] According to embodiments herein, heat shields can include several shielding layers to reduce the heat radiation to the outside of the crucible and the distribution assembly. As a further option, the heat shield(s) 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, which can be combined with other embodiments described herein, the one or more heat shields provided for the evaporation assembly, may include sheet metals surrounding the respective portions of the evaporation assembly, such as the distribution pipe and/or the evaporation crucible 100. For example, 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 including 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.

[0021] According to embodiments herein, the crucible 100 shown in Fig. 1 may include one or more heat transfer elements 170 arranged within the inner volume 150 of the crucible 100. The heat transfer elements 170 are configured to provide an indirect heating of the inner volume of the crucible. In the embodiments described herein, the heat from the one or more heat transfer elements 170 is directly provided to the source material, which may be in the form of powders, liquids and/or pellets, within the inner volume 150 of crucible 100. In embodiments described herein, the heat transfer elements are configured to receive heat passively and may not need a direct connection to, for instance, a heating unit and/or power supply.

[0022] According to embodiments herein, the heat transfer elements 170 may, for instance, receive heat from the wall and/or from the outside of the crucible. During an OLED deposition process, the heat from the wall and/or from the outside of the crucible is distributed within the inner volume of the crucible by the heat transfer elements 170 to ensure a more homogenous heating and subsequent evaporation of the source material. According to some embodiments described herein, the heat transfer elements are arranged within the inner volume of the crucible such that the temperature measured at any specific location within the inner volume of the crucible compared to a predetermined temperature and/or compared to the temperature at another specific location within the inner volume of the crucible differ by a maximum temperature difference of 10 °C or less, for example, 5 °C or less, such as 0.5 °C to 3 °C. Yet further, additionally or alternatively, the maximum temperature difference can be 4% or less, for example, 2 % or less, such as 0.2 % to 1.1%.

[0023] In the embodiment shown in Fig. 1, the heat transfer elements 170 protrude from the wall into the inner volume 150 of the crucible 100. In particular, the embodiment as shown in Fig. 1 includes a first heat transfer element 171 and a second heat transfer element 172. The first and the second heat transfer elements 171, 172 are cup-like shaped for accommodating liquid in the respective first and second heat transfer elements. According to embodiments herein, the liquid may be the source material. According to embodiments herein, the first and the second heat transfer elements 171, 172 are connected to at least a portion of any one or more of the side walls 161-166 of the crucible 100.

[0024] The heat transfer elements 171, 172 may be provided within the inner volume 150 of the crucible 100 such that the first heat transfer element 171 is arranged above the second heat transfer element 172. In this particular embodiment the term "above" is intended to describe that the first heat transfer element 171 is arranged closer to the opening 104 of the crucible than the second heat transfer element 172.

[0025] The first and the second heat transfer elements 171, 172 may have the same shape or the first and the second heat transfer elements may differ with respect to geometry and/or size. In particular, according to embodiments herein, the heat transfer elements 170 have a plate-like portion 171a, 172a and a tube-like portion 171b, 172b. The plate-like portion 171a, 172a may be connected to the side wall 161-166 at least along a portion of the inner surface of the crucible 100. The tube-like portion 171b, 172b may be arranged at the center of the plate-like portion 171a, 172a. The tube-like portion 171b, 172b may extend towards the opening 104 of the crucible 100, which provides a connection for a fluid exchange between the crucible and a distribution assembly, in particular between the crucible 100 and a distribution pipe. In embodiments herein, the center of the opening of the tube-like portion 171b, 172b of the heat transfer elements 171, 172 and the center of the crucible opening 104 may be arranged to align along a central axis 105 of the crucible 100. [0026] According to embodiments herein, a source material, particularly a liquid source material may be provided in the space between the inner surface of the wall, the plate-like portion 171a, 172a and the tube-like portion 171b, 172b.

[0027] In the embodiment shown in Fig. 1, the first and the second heat transfer elements 171, 172 separate the inner volume 150 of the crucible 100 into three distinct sub-spaces of the inner volume 150, which are interconnected via the tube-like portions 171b, 172b of the respective first and second heat transfer elements 171, 172. According to some embodiments herein, the crucible 100 may only include a single heat transfer element arranged within the inner volume of the crucible, separating the inner volume into two distinct sub-spaces, which are interconnected by a tube-like portion of the heat transfer element. Similarly, according to further embodiments herein, the crucible may include three, four or more heat transfer elements separating the inner volume of the crucible into four, five or more distinct sub-spaces.

[0028] According to some embodiments described herein, the inner surface of the wall of the crucible 100 may have a first area of a first size and the one or more heat transfer elements 170 may provide a second area within the inner volume 150 of a second size. According to embodiments herein, the second area may have the same size as the first area. According to yet further embodiments described herein, the combined size of the first and second area is of at least two times the first size.

[0029] According to some embodiments herein, the one or more heat transfer elements may be made of materials including metals or alloys with a high thermal conductivity. For example, the heat transfer elements may include any one or more elements chosen from the following list: titanium, stainless steel and diamond-like carbon (DLC). In embodiments herein, the material of the one or more heat transfer elements may be inert with respect to the source materials such that the heat transfer elements do not react with the source material during the evaporation process. Depending on the evaporation temperature of the source material used, the materials of the one or more heat transfer elements should be stable and inert at least up to the evaporation temperature of the source material, which may, for example, be anywhere between 150°C and 650°C or more.

[0030] Fig. 2 shows a schematic view of a further crucible according to embodiments described herein. The crucible shown in Fig. 2 is illustrated as two halves, which are mirror symmetrical with respect to a plane of symmetry 201. The crucible 200 may include one or more heat transfer elements 270, which protrude from the wall into the inner volume 250 of the crucible 200. In particular, the one or more heat transfer elements may protrude from a sidewall into the inner volume of the crucible. Similar to the geometry of the crucible shown in Fig. 1, the crucible 200 shown in Fig. 2 may include a bottom wall 267 and a top wall 268 that are connected to each other via the side walls 261-266. The crucible 200 may include an opening 204, which allows evaporated source material to exit from the crucible and enter a distribution assembly.

[0031] Similar to the embodiment shown in Fig. 1, the distribution assembly may, for instance, include one or more distribution pipes (not shown in the Fig. 2) with outlets (e.g. nozzles), which guide the evaporated source material from the crucible to the substrate. The crucible 200 and the distribution pipe may be connected to each other via a form-fit connection 203. According to embodiments herein, the connection between the crucible and distribution pipe may additionally or alternatively include a flange unit. Similar to the embodiment shown in Fig. 1, the crucible 200 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.

[0032] The crucible 200 according to embodiments herein may include one or more heat transfer elements 270 arranged within the inner volume 250 of the crucible. In the embodiment shown in Fig. 2, the one or more heat transfer elements 270 are provided as six plates 271-276. Generally, the six plates are arranged within the inner volume 250 of the crucible to guide the evaporated source materials towards the distribution assembly. Each of the six plates 271-276 protrudes from the wall towards the center of the inner volume 250 of the crucible 200. According to embodiments herein and as is shown in more detail in Fig. 4, which shows a different schematic view of the crucible shown in Fig. 2, each of the six plates 271-276 may be arranged to be perpendicular with respective side walls 261-266 of the crucible 200. In embodiments herein, the crucible 200 may have a hexagonal geometry. However, according to further embodiments herein, the crucible is not limited to a hexagonal geometry but may include further geometrical shapes such as a rectangular, circular, oval or triangular shape.

[0033] Any one or all of the six plates 271-276 may extend into or through the wall of the crucible 200. According to the embodiment shown in Fig. 2, any one or more of the six plates 271-276 may extend through each of the respective side walls 261-266 of the crucible 200. However, in embodiments described herein, any one or more of the six plates 271-276 may extend completely through at least one of the bottom wall 267, a side wall 261- 266 and top wall 268.

[0034] According to embodiments described herein, the wall of the crucible 200 may include a plurality of slits to accommodate the six plates 271-276. The slits may extend completely through the wall of the crucible 200. In the embodiments herein, the slits may simplify the assembly procedure and ensure that heat is effectively conducted from the outside to the inner volume of the crucible. For instance, during assembly of the crucible the plates may be inserted into the slits and also welded from the outside to the crucible.

[0035] According to embodiments herein, any one or more of the six plates 271-276 may extend in a longitudinal direction, parallel to the central axis 205 of the crucible 200 anywhere from about 0% to about 100% of the total length 269 of the inner volume 250 of the crucible 200. For example, any one or more of the six plates 271-276 may extend at least about 90% of the total length of the inner volume of the crucible.

[0036] In embodiments described herein, the plates may be arranged within the crucible such that the smallest absolute angle at the point of intersection between two adjacent planes, each plane extending parallel with one of the plates 271-276, is anywhere between about 5° and about 175°, such as for instance about 30°, about 45° or about 60°.

[0037] Fig. 3 shows a schematic view of a crucible according to a further embodiment described herein. The crucible 300 includes all of the features described with respect to the embodiment shown in Fig. 2. However, as compared to the embodiment shown in Fig. 2, the one or more heat transfer elements 370 of the embodiment shown in Fig. 3 include a plurality of plates 371-388, in this particular example, eighteen plates that are arranged within the inner volume 350 of the crucible 300. Similar to the embodiment shown in Fig. 2, each of the plates 371-388 extends through the wall of the crucible 300. According to embodiments herein, increasing the number of plates may increase the surface area of the one or more heat transfer elements within the inner volume of the crucible. Optionally, according to embodiments herein, having a plurality of heat transfer elements may allow the crucible to be modular in the sense that heat transfer elements can be added and/or taken out from the inner volume of the crucible depending on the particular beneficial implementations regarding heat distribution and space within the inner volume of the crucible. [0038] Fig. 4 shows a cross-sectional perspective view of the crucible 200 shown in Fig. 2 along line A-A. Fig. 4 shows the six heat transfer elements, e.g. plates 271- 276, each protruding at an angle of about 90° with respect to a respective side wall 261-266. Each of the one or more heat transfer elements may extend completely through the wall of the crucible. As is shown in Fig. 4, each of the six plates 271-276 extend to an outer edge 290 of the crucible. In the embodiment shown in Fig. 4, at least four 272-273, 275-276 out of the six plates may protrude the same distance into the inner volume of the crucible. According to some embodiments described herein, all of the six or more plates may protrude the same distance or each a different distance into the inner volume of the crucible. In the embodiments described herein, the particular arrangement of the one or more heat transfer elements may be adapted to the particular use and in particular to a beneficial distribution of heat within the inner volume of the crucible.

[0039] According to embodiments described herein, one or more heaters may be arranged around at least a portion of the wall. A shield, which reflects the heat from the one or more heaters towards the inner volume of the crucible, may be arranged around the one or more heaters .

[0040] Fig. 5 shows a schematic view of the crucible according to further embodiments described herein. The crucible 500 has circular geometry, which is defined by its wall 560. The crucible 500 may include a plurality of heat transfer elements, e.g. plates 571-578, which may be arranged within the inner volume 550 of the crucible 500. The heat transfer elements, which according to the embodiment shown in Fig. 5 may be in the form of eight plates, are arranged within the inner volume 550 of the crucible 500 such that the smallest absolute angle at the point of intersection between two adjacent planes, each plane extending parallel with one of the plates 571-578, is about 45°. A symmetrical arrangement of the plurality of heat transfer elements may ensure a homogenous distribution of heat within the inner volume of the crucible. According to the embodiment shown in Fig. 5, the eight plates 571-578 extend completely through the wall 560 of the crucible 500. According to further embodiments herein, one or more of the plates may be connected to an inner surface of the wall 560 of the crucible 500. According to some embodiments herein, the inner surface of the crucible may include recessed portions to which the one or more heat transfer elements are connected. The recessed portion may not extend completely through the wall of the crucible. For instance, during assembly of the crucible, the one or more heat transfer elements may be arranged into the recessed portion from the top and/or bottom of the crucible.

[0041] According to some embodiments described herein, the one or more heat transfer elements may be arranged within the inner volume of the crucible such that the space in the center of the inner volume measuring at least 10 mm in diameter 580 does not include any portions of the one or more heat transfer elements. According to embodiments herein, the space in the center of the crucible that does not include any portions of a heat transfer element may, for instance, be in the shape of a sphere with a diameter anywhere from 10 mm to 35 mm.

[0042] Fig. 6 shows a schematic view of a crucible according to a further embodiment described herein. The crucible 600 may include one or more heat transfer elements 670, which protrude from the wall into the inner volume 650 of the crucible 600. According to the embodiment shown in Fig. 6, the one or more heat transfer elements 670 are provided as one or more rods 671-675. Each of the rods 671-675 may be arranged to be perpendicular with respective to at least one side wall 661-666 of the crucible 600. The crucible 600 has a hexagonal geometry. However, similar to any of the previous embodiments described herein, the crucible is not limited to a hexagonal geometry but may include further geometrical shapes such as a square, rectangular, triangular, circular or oval shape.

[0043] According to the embodiment shown in Fig. 6, each of the one or more rods 671-675 may extend completely through the inner volume 650 of the crucible 600. Each of the rods may for instance interconnect two opposing side walls 661-664, 662-665, and 663- 666 of the crucible 600. In embodiments herein, the rods are shown as being straight rods extending through at least two side walls of the crucible. According to some embodiments herein, the one or more heat transfer elements, which may be provided in the shape of rods, plates or any other shape may not be straight but may be curved in order to further increase the surface area of the one or more heat transfer elements within the inner volume of the crucible.

[0044] Each of the side walls 661-666 of the crucible 600 may include a plurality of holes 669 to accommodate the five 671-675 rods. The holes 669 extend completely through the wall of the crucible 600. The holes may simplify the assembly procedure and ensure that heat is effectively conducted from the outside to the inner volume of the crucible. For instance, during assembly of the crucible the rods may be inserted into the holes 669 from the outside of the crucible and also welded from the outside to the crucible.

[0045] According to embodiments herein, the crucible may include more than five rods distributed within the inner volume of the crucible. In particular, according to embodiments herein the rods may be arranged in a counter-clockwise direction along the inner surface of the wall of the crucible, one on top of the other. The particular arrangement of the rods within the inner volume of the crucible may be varied for the same or different crucibles in order to meet a beneficial heat distribution within the inner volume of the crucible. [0046] Fig. 7 shows a schematic view of an evaporation assembly according to embodiments herein. The evaporation assembly may include one or more distribution assemblies, such as one or more distribution pipes, and one or more evaporation crucibles. In general, according to embodiments described herein, the distribution pipe may include an inner volume to accommodate and guide the evaporated source material from the crucible. In particular, the evaporation assembly 700 shown in Fig. 7 includes at least one distribution pipe 706 and at least one crucible 100 as, for instance, shown in Fig. 1. However, according to further embodiments herein, the evaporation assembly may include any one or more of the crucibles including any one or more of the heat transfer elements described herein.

[0047] The distribution pipe 706 can be an elongated cube with a heating unit 715. As described with respect to the crucible shown in Fig. 1, the crucible 100 can be a reservoir for an organic material to be evaporated by the heat provided from the heating unit 125 via the one or more heat transfer elements 170. According to embodiments described herein, the heating unit of the distribution pipe may heat the distribution pipe and prevent the vapor of the organic material, which is provided by the crucible 100, from condensing at an inner portion of the wall of the distribution pipe 706.

[0048] According to embodiments 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 little lower circle. According to embodiments described herein, one or more heat shields and/or cooling shield arrangements may be provided for a reduced heat transfer to the substrate to be coated and/or a mask used during a coating process. For example, the heat transfer from the evaporation source to the substrate and/or mask can be reduced by having nozzles penetrating through the heat shields and the cooling shield arrangements surrounding the distribution assembly. According to 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, 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. Instead, the base surface and the upper surface can have a shape different from a circle.

[0049] According to embodiments herein, which can be combined with other embodiments described herein, distribution pipe 706 provides a linear evaporation assembly. The distribution pipe 706 includes a plurality of openings 712 arranged along the length direction of the distribution pipe 706. According to an alternative embodiment, one elongated opening extending along the length direction of the distribution pipe can be provided. For example, the elongated opening can be a slit. According to some embodiments, which can be combined with other embodiments described herein, the distribution pipe extends essentially vertically. For example, the length of the distribution pipe 706 may correspond at least to the height of the substrate to be deposited with the evaporation assembly. In many cases, the length of the distribution pipe 706 will be longer than the height of the substrate to be deposited, at least by 10% or even 20%, which may assist a uniform deposition at the upper end of the substrate and/or the lower end of the substrate.

[0050] 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. 7, the crucible 100 is provided at the lower end of the distribution pipe 706. The organic material is evaporated in the crucible 100. The vapor of organic material enters the distribution pipe 706 at the bottom of the distribution pipe and is guided essentially upwards and then essentially sideways through the plurality of openings 712 in the distribution pipe 706, e.g. towards an essentially vertical substrate.

[0051] According to some embodiments, which can be combined with other embodiments described herein, the outlets (e.g. nozzles) are arranged to have a main evaporation direction slightly upward, e.g. to be in a range from horizontal to 15° upward, such as 3° to 7° upward. The substrate can be slightly inclined to be substantially (e.g. + 10°) perpendicular to the evaporation direction, which may reduce undesired particle generation. For illustrative purposes, in Fig. 7 the crucible 100 and the distribution pipe 706 are shown without heat shields. The heating unit 715 and the heating unit 125 can be seen in the schematic perspective view shown in Fig. 7. However, according to embodiments herein, both the crucible and the distribution pipe can include one or more heat shield layers to reflect heat energy provided by one or more heating units towards the inner volume of the crucible and/or the distribution pipe.

[0052] In embodiments described herein, the heat shields can reduce energy loss from the evaporation assembly and reduce the overall energy consumption. However, as a further aspect, particularly for deposition of organic materials, heat radiation originating from the evaporation assembly can be reduced, particularly heat radiation towards, for instance, a mask used during a deposition/coating process. Particularly for 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. Thus, heat radiation originating from the evaporation assembly can be reduced or avoided.

[0053] Fig. 8 and Fig. 9 show schematic top views of portions of different evaporation assemblies according to embodiments herein. For example, Fig. 8 shows a portion of an evaporation assembly 800 including at least three crucibles 100. The crucibles have a hexagonal geometry. The portion of an evaporation assembly 900 shown in Fig. 9, for example, includes at least two triangular crucibles 901. According to some embodiments herein, the evaporation assembly may include a plurality of crucibles according to any of the embodiments described herein. For instance, the evaporation assembly may include two, three, four or more crucibles, which may be connected to at least one or more distribution assemblies.

[0054] Fig. 10 shows a schematic view of a deposition system for depositing a source material on a substrate according to embodiments herein. The deposition system 1000 may, for instance, include an evaporation assembly 700 similar to the deposition assembly described with respect to Fig. 7. The evaporation assembly 700 includes a crucible 100 as, for instance, described with respect to Fig. 1, and a distribution pipe 706 as, for instance, described with respect to Fig. 7. The distribution pipe 706 shown in Fig. 10 is supported by a support 1020. Further, according to some embodiments, the crucible 100 can also be supported by the support 1020. According to the embodiment shown in Fig. 10, two substrates 1010 are provided in the vacuum chamber 1050. Typically, a mask 1030 for masking of the layer deposition on the substrate can be provided between the substrate 1010 and the evaporation assembly 700. Organic material is evaporated from the crucible 100 and guided via the distribution pipe 706 to the substrate 1010.

[0055] According to embodiments described herein, the evaporation assembly may include one or more crucibles and one or more distribution pipes, wherein a respective one of the one or more distribution pipes can be in fluid communication with the respective one of the one or more crucibles. Various applications for OLED device manufacturing include processing stages wherein two or more organic materials are evaporated simultaneously. Accordingly, two distribution pipes and corresponding evaporation crucibles can be provided next to each other. In such embodiments, more than one kind of organic material may, for instance, be evaporated at the same time.

[0056] According to embodiments described herein, the substrates are coated with organic material in an essentially vertical position. That is, the view shown in Fig. 10 is a top view of a deposition apparatus including the evaporation assembly 700. The distribution pipe 706 provides a linear evaporation assembly extending essentially vertically. According to embodiments described herein, which can be combined with other embodiments described herein, essentially vertically is understood particularly when referring to the substrate orientation, to allow for a deviation from the vertical direction of 20° or below, e.g. of 10° or below. This deviation can be provided for example because a substrate support with some deviation from the vertical orientation might result in a more stable substrate position. Yet, the substrate orientation during deposition of the source material is considered essentially vertical, which is considered different from the horizontal substrate orientation. According to embodiments herein, the surface of the substrates is coated by an evaporation assembly extending in one direction corresponding to one substrate dimension and a translational movement along the other direction corresponding to the other substrate dimension. [0057] The deposition system 1000 shown in Fig. 10, in particular, illustrates an embodiment of a deposition system for depositing organic material in a vacuum chamber 1050. The evaporation assembly 700 is provided in the vacuum chamber 1050 on a track, e.g. a looped track or linear guide 1025. The track or the linear guide 1025 is configured for the translational movement of the evaporation assembly 700. 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 assembly 700, at the track or linear guide 1025, within the vacuum chamber 1050 or a combination thereof. Further, Fig. 10 shows a valve 1060, for example a gate valve. The valve 1060 may, for instance, allow for a vacuum seal to an adjacent vacuum chamber (not shown in Fig. 10). The valve can be opened for transport of a substrate 1010 or a mask 1030 into the vacuum chamber 1050 or out of the vacuum chamber 1050 respectively.

[0058] According to some embodiments, which can be combined with other embodiments described herein, a further vacuum chamber, such as maintenance vacuum chamber 1070 is provided adjacent to the vacuum chamber 1050. The vacuum chamber 1050 and the maintenance vacuum chamber 1070 are connected by a valve 1080. The valve 1080 is configured for opening and closing a vacuum seal between the vacuum chamber 1050 and the maintenance vacuum chamber 1070. The evaporation assembly 700 can be transferred to the maintenance vacuum chamber 1070 while the valve 1080 is in an open state. Thereafter, the valve can be closed to provide a vacuum seal between the vacuum chamber 1050 and the maintenance vacuum chamber 1070. If the valve 1080 is closed, the maintenance vacuum chamber 1070 can be vented and opened for maintenance of the evaporation assembly 700 without breaking the vacuum in the vacuum chamber 1050.

[0059] According to embodiments herein, two substrates 1010 are supported on respective transportation tracks within the vacuum chamber 1050. Further, two tracks for providing masks 1030 thereon are provided. The substrates 1010 can be masked by respective masks 1030 during a coating process. According to typical embodiments, the masks 1030 may be provided in a mask frame 1031 to hold the mask 1030 in a predetermined position.

[0060] According to some embodiments, which can be combined with other embodiments described herein, the substrate 1010 can be supported by a substrate support 1026, which is connected to an alignment unit 1012. An alignment unit 1012 can adjust the position of the substrate 1010 with respect to the mask 1030. Fig. 10 illustrates an embodiment where the substrate support 1026 is connected to an alignment unit 1012. Accordingly, the substrate is moved relative to the mask 1030 in order to provide for a proper alignment between the substrate and the mask during deposition of the organic material. According to a further embodiment, which can be combined with other embodiments described herein, alternatively or additionally the mask 1030 and/or the mask frame 1031 holding the mask 1030 can be connected to the alignment unit 1012. Either the mask can be positioned relative to the substrate 1010 or the mask 1030 and the substrate 1010 can both be positioned relative to each other. The alignment units 1012, which are configured for adjusting the position between a substrate 1010 and a mask 1030 relative to each other, allow for a proper alignment of the masking during the deposition process, which is beneficial for high quality or OLED display manufacturing.

[0061] Examples of an alignment of a mask and a substrate relative to each other include alignment units, which allow for a relative alignment in at least two directions defining a plane, which is essentially parallel to the plane of the substrate and the plane of the mask. For example, an alignment can at least be conducted in an x-direction and a y-direction, i.e. two Cartesian directions defining the above-described parallel plane. Typically, the mask and the substrate can be essentially parallel to each other. Specifically, the alignment can further be conducted in a direction essentially perpendicular to the plane of the substrate and the plane of the mask. Thus, an alignment unit is configured at least for an X-Y- alignment, and specifically for an X-Y-Z-alignment of the mask and the substrate relative to each other. One specific example, which can be combined with other embodiments described herein, is to align the substrate in the x-direction, y-direction and z-direction to a mask, which can be held stationary in the vacuum chamber 1050.

[0062] As shown in Fig. 10, the linear guide 1025 provides a direction of the translational movement of the evaporation assembly 700. A mask 1030 may be provided on either side of the evaporation assembly 700. According to embodiments described herein, the masks 1030 can extend essentially parallel to the direction of the translational movement. Further, the substrates 1010 arranged at the opposing sides of the evaporation source, e.g. evaporation assembly 700, can also extend essentially parallel to the direction of the translational movement. According to typical embodiments, a substrate 1010 can be moved into the vacuum chamber 1050 and out of the vacuum chamber 1050 through valve 1060. The deposition system 1000 can include a respective transportation track for transportation of each of the substrates 1010. For example, the transportation track can extend parallel to the substrate position shown in Fig. 10 and into and out of the vacuum chamber 1050.

[0063] Typically, further tracks are provided for supporting the mask frames 1031 and the masks 1030. Some embodiments, which can be combined with other embodiments described herein, can include four tracks within the vacuum chamber 1050. In order to move one of the masks 1030 out of the chamber, for example for cleaning of the mask, the mask frame 1031 including the mask can be moved onto the transportation track of the substrate 1010. The respective mask frame can then exit or enter the vacuum chamber 1050 on the transportation track of the substrate. Even though it would be possible to provide a separate transportation track into and out of the vacuum chamber 1050 for the mask frames 1031, the costs of ownership of a deposition system 1000 can be reduced if only two tracks, i.e. transportation tracks for a substrate, extend into and out of the vacuum chamber 1050 and, in addition, the mask frames, e.g. together with respective masks 1030, can be moved onto a respective one of the transportation tracks for the substrate by an appropriate actuator or robot.

[0064] According to embodiments herein, a method 1100 for coating a substrate with a source material evaporated from a crucible is provided. The crucible may be any one or more of the crucibles described above and generally includes a wall with an inner surface surrounding an inner volume for receiving the source material and at least one heat transfer element arranged within the inner volume of the crucible. The method includes providing 1110 a source material within the crucible, in particular within the inner volume of the crucible. According to embodiments herein, the source material may be in the form of a powder, liquid and/or pellets. The method further includes heating 1120 the source material to an evaporation temperature by providing an indirect heating of the inner volume of the crucible. In particular, power may be provided to a heater arranged at least along an outer portion of the wall of the crucible. The term "outer portion" as used herein shall refer to any portion of the crucible that is not within the inner volume of the crucible. For instance, the outer portion of the wall may, for instance, be covered by a shield such that the heater is arranged between the outer portion of the wall and the shield. [0065] Heating the source material may be done under vacuum, which helps with desorption of any humidity out of the powder and the temperature may be increased gradually. According to embodiments described herein, the temperature may be elevated to a stand-by temperature at which evaporation of the source material is on the verge of occurring. The stand-by temperature may, for example, be anywhere from 90 % to 95 % of the evaporation temperature. According to embodiments herein, the temperature may be controlled by one or more sensors and a temperature controller acting on the power supply, which is connected to the heater(s). [0066] In embodiments described herein, the temperature may gradually be increased to the evaporation temperature from the stand-by temperature to better regulate the deposition rate.

[0067] According to embodiments herein, providing an indirect heating of the inner volume of the crucible may further include generating 1130 a maximum of 5 % of a total heating power within the inner volume of the crucible. In embodiments described herein, most of the heating power is produced outside of the inner volume of the crucible and indirectly provided to the inner volume of the crucible in order to evaporate the source material. The heat may be provided into the inner volume of the crucible passively by the one or more heat transfer elements. In particular, the heat from the heater may be conducted via the crucible wall and/or the one or more heat transfer elements to the inner volume of the crucible.

[0068] In embodiments herein, the heat from the heater is homogenously distributed within the inner volume of the crucible via the wall and/or the one or more heat transfer elements. Generally, no heaters are provided directly within the inner volume of the crucible as these may cause a disturbance with respect to the control of the heater(s) on the outside of the crucible. According to embodiments herein, the majority of the heating power is applied to a heater on the outside of the crucible and the thermal energy generated from the heater brought into the inner volume of the crucible by conduction via the wall and/or the one or more heat transfer elements.

[0069] According to embodiments herein, the heating of the source material may further include moving the one or more heat transfer elements from at least a first position to a second position in order to more homogenously distribute the heat within the inner volume of the crucible. [0070] The method for coating a substrate with a source material further includes guiding 1140 the evaporated and/or sublimated source material to the substrate, creating a film of source material on the surface of the substrate. According to embodiments herein, guiding the evaporated source material may include providing 1150 thermal energy to the evaporated source material. Further, in embodiments herein, guiding the source material may further include cooling 1160 the evaporated source material in proximity of the substrate to facilitate deposition of the source material on the surface of the substrate.

[0071] While the foregoing is directed to embodiments of the invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof.