Patent Application
20180190908
The present invention relates to the field of organic electronics. More specifically, it relates to methods for high-resolution patterning of organic layers, such as organic semiconductor layers, by means of photolithography, and to methods for fabricating organic electronic devices comprising an organic semiconductor layer patterned by photolithography.
Organic electronics research is steadily growing, with developments in materials, processes and system integration. Applications such as organic photovoltaic cells (OPV), organic photodetectors (OPD), organic thin-film transistors (OTFT) and especially organic light-emitting diodes (OLED) for lighting and displays are leading the way to industrialization.
One of the bottlenecks of known methods for the fabrication of organic electronic devices may be related to the limitations of currently available patterning techniques.
A particularly promising technique to achieve a pattern resolution below 10 micrometer in a reproducible way and on large wafer sizes may be photolithography. However, using a photolithographic process in combination with organic semiconductors is not straightforward, because most of the solvents used within standard photoresists, as well as the solvents used for resist development and/or resist stripping may dissolve the organic layers. A few solutions to this problem have been proposed, such as for example dry lithography using frozen CO2 photoresists, orthogonal processing using fluorinated photoresists, or using a barrier layer to protect the organic semiconductor layer and to avoid direct contact between the organic semiconductor layer and the photolithographic chemicals. One such approach is for example described in WO 2015/028407A1. A method for photolithographic patterning of an organic layer deposited on a substrate is disclosed, wherein a shielding layer is provided on the organic layer before applying a photoresist layer and before performing the photolithographic patterning steps. The shielding layer is a water soluble layer that can easily be removed after photolithographic patterning by exposing the shielding layer to water or to a solution comprising water.
However, applying such an approach may involve a risk that water penetrates into the organic layer and causes damage to or degradation of the organic semiconductor layer, such as for example a reduction of the carrier mobility, morphological changes, or interface contamination. For example, in the field of organic light emitting diodes (OLEDs) most organic semiconductor materials used, such as the emission layer and the electron transport layer, are water sensitive. When patterning such layers using photolithography in combination with a water soluble or water based shielding layer, water may penetrate into the OLED stack, resulting in degradation of the device, e.g. a reduction of the operational lifetime, a reduction of the emission quantum efficiency, a reduction of power efficiency and/or changes in the colour emitted by the OLEDs. For other organic semiconductor devices similar degradation mechanisms may occur, leading for example to a reduction of the efficiency of organic photodetectors or organic photovoltaic cells.
It is an object of embodiments of the present invention to provide methods for photolithographic patterning of organic layers such as organic semiconductor layers, wherein the methods overcome the disadvantages of the prior art.
The above objective is accomplished by a method according to the present invention.
The present invention relates to a method for photolithographic patterning of an organic layer on a substrate. The method comprises the steps of, e.g. the sequence of steps of, providing a water soluble shielding layer over the organic layer, providing a photoresist layer on the shielding layer, photolithographic patterning of the photoresist layer to thereby form a patterned photoresist layer, etching the shielding layer and the organic layer using the patterned photoresist layer as a mask to thereby form a patterned shielding layer and a patterned organic layer, and afterwards removing the patterned shielding layer. Furthermore, the method comprises, before providing the water soluble shielding layer, providing on the organic layer a hydrophobic protection layer having a hydrophobic upper surface. In the context of the present disclosure, the upper surface of the hydrophobic protection layer refers to the surface facing away from the organic layer on which it is provided.
In embodiments of the present invention, providing the water soluble shielding layer may comprise providing the water soluble shielding layer in direct contact with the hydrophobic protection layer, i.e. without another layer in between.
In embodiments of the present invention, removing the patterned shielding layer may comprise exposing the patterned shielding layer to water or to a solution comprising water.
In embodiments of the present invention, the organic layer may be an organic semiconductor layer or may comprise an organic semiconductor layer. The organic layer may be a single layer or a multilayer stack comprising at least two layers. The organic layer or organic layer stack may for example comprise an electroluminescent layer or a photosensitive layer, embodiments of the present invention not being limited thereto. For example, the organic layer may be a multilayer stack e.g. comprising a hole injection layer, an electron blocking layer, a hole transport layer, an electroluminescent organic layer, an electron transport layer, a hole blocking layer and/or an electron injection layer, embodiments of the present invention not being limited thereto.
In preferred embodiments of the present invention, the hydrophobic protection layer may be a hydrophobic organic layer, e.g. a hydrophobic organic semiconductor layer. It is an advantage of using an organic layer, e.g. an organic semiconductor layer, for forming the hydrophobic protection layer that it has a good process compatibility with a fabrication process of organic devices such as OLEDs, OPDs, OPVs or OTFTs. In embodiments of the present invention the hydrophobic protection layer may be a charge transport layer.
In embodiments of the present invention, the hydrophobic protection layer, e.g. the hydrophobic organic semiconductor layer, may be a single layer.
In embodiments of the present invention, the hydrophobic protection layer, e.g. the hydrophobic organic semiconductor layer, may be a multilayer stack comprising at least two layers, wherein an upper layer of the multilayer stack has a hydrophobic upper surface.
The hydrophobic protection layer, e.g. the hydrophobic organic semiconductor layer, may be provided in direct contact with the organic layer, i.e. without another layer between the organic layer and the hydrophobic layer. However, embodiments of the present invention are not limited thereto.
The present invention is further related to a method for fabricating an electronic device comprising an organic layer, wherein the method comprises photolithographic patterning the organic layer using a method as described above. Examples of electronic devices that may be fabricated using a method according to embodiments of the present invention are: organic light emitting diodes, organic photodetectors, organic photovoltaic cells, organic thin film transistors and/or arrays comprising such devices, embodiments of the present invention not being limited thereto.
In a method for fabricating an electronic device according to embodiments of the present invention, the organic layer may be an active organic semiconductor layer of the device, and the hydrophobic protection layer may be a hydrophobic organic semiconductor charge transport layer of the device (electron transport layer or hole transport layer). The hydrophobic protection layer may thus remain in the device. The active organic semiconductor layer may have a first HOMO (Highest Occupied Molecular Orbital) energy level and a first LUMO (Lowest Unoccupied Molecular Orbital) energy level, and the hydrophobic organic semiconductor charge transport layer may have a second HOMO energy level and a second LUMO energy level at a surface in contact with the active organic semiconductor layer, wherein the first and second HOMO energy levels and the first and second LUMO energy levels are selected to enable good carrier injection into the active organic semiconductor layer. In preferred embodiments of the present invention, the second HOMO energy level may be selected to be lower than the first HOMO energy level and the second LUMO energy level may be selected to be higher than the first LUMO energy level, thus enabling efficient charge injection, more in particular electron injection or hole injection, into the active organic semiconductor layer.
The hydrophobic organic semiconductor charge transport layer may be a multilayer stack comprising a first charge transport layer in contact with the active organic semiconductor layer and a second charge transport layer at an upper side of the multilayer stack, i.e. at a side facing away from the active organic semiconductor layer, the first charge transport layer having suitable HOMO and LUMO energy levels to enable efficient carrier injection into the active organic semiconductor layer as described above, and the second charge transport layer having a hydrophobic upper surface. The second charge transport layer may be doped. The first charge transport layer may be non-doped or at least an upper portion of the first charge transport layer may be doped. It is an advantage of doping the second charge transport layer and an upper portion of the first charge transport layer that the energy barrier for charge injection at the interface between the first charge transport layer and the second charge transport layer may be reduced.
The electronic device may for example be an organic light emitting device and the active organic semiconductor layer may be an electroluminescent layer. The electronic device may for example be an array of organic light emitting devices.
The electronic device may for example be an organic photodetecting device or an organic photovoltaic device, and the active organic semiconductor layer may be a photosensitive or light absorbing layer. The electronic device may for example be an array of photodetecting devices or an array of photovoltaic devices.
A method in accordance with embodiments of the present invention may be used in a fabrication process of an electronic device comprising a first organic layer at a first location, e.g. at first locations, on a substrate and comprising a second organic layer at a second location, e.g. at second locations, on the substrate, in which the second location, e.g. second locations, is non-overlapping with the first location, e.g. first locations. The first organic layer and the second organic layer may be patterned using a method as described above. The device may further comprise a third (further) organic layer at a third (further) location, e.g. third (further) locations, on the substrate, in which the third (further) location, e.g. third (further) locations, is non-overlapping with the first and second locations. The third (further) organic layer may be patterned using a method as described above.
The electronic device may for example be a multicolour organic light emitting device, wherein the first organic layer comprises a first electroluminescent layer for emitting a first colour or first colour spectrum and wherein the a second organic layer comprises a second electroluminescent layer for emitting a second colour or second colour spectrum and wherein the third (further) organic layer comprises a third (further) electroluminescent layer for emitting a third (further) colour or colour spectrum.
In a method for fabrication of such devices, e.g. multicolour devices, in accordance with embodiments of the present invention, a first hydrophobic protection layer may be provided on the first organic layer, a second hydrophobic protection layer may be provided on the second organic layer, and a third (further) hydrophobic protection layer may be provided on the third (further) organic layer. The first, second, third (further) hydrophobic protection layers may have the same composition or they may have a different composition, e.g. comprise a different material, with respect to each other.
In a method in accordance with embodiments of the present invention, the water soluble shielding layer may comprise or contain a water based polymer material that is not cross linkable. It is an advantage of using a material that is not cross linkable that it can be removed easily and completely with water or a water based solution. In a method according to embodiments of the present invention, the shielding layer may comprise any of or any combination of polyvinyl pyrrolidone, polyvinyl alcohol, water-soluble cellulose, polyethylene glycol, polyglycerin or pullullan, embodiments of the present invention not being limited thereto. The shielding layer may further comprise water and/or an alcohol, e.g. a water soluble alcohol.
In a method in accordance with embodiments of the present invention, providing the shielding layer may comprise providing the shielding layer by solution processing, e.g. by spin coating, followed by soft baking at e.g. about 100° C. It is an advantage of such solution based methods that they are cost effective and that they do not require a vacuum. The shielding layer may for example have a thickness in the range between 300 nm and 1000 nm, embodiments of the present invention not being limited thereto.
In a method in accordance with embodiments of the present invention, removing the shielding layer may comprise coating a water layer or a water based solution on top of the shielding layer. The water based solution used for removing the shielding layer may comprise water and may further comprise for example Isopropyl alcohol (IPA) and/or Glycerin, embodiments of the present invention not being limited thereto.
In a method in accordance with embodiments of the present invention, providing the photoresist layer may comprise providing a photoresist layer that is solvent developable. It is an advantage of using a solvent developable photoresist that it is compatible with the water based shielding layer.
In a method in accordance with embodiments of the present invention, etching the shielding layer and the organic layer may comprise performing one or more dry etching steps, such as for example reactive ion etching (RIE) steps, for example using an oxygen plasma or any other suitable plasma such as for example an Ar plasma, an SF6 plasma or a CF4 plasma, embodiments of the present invention not being limited thereto. Etching the shielding layer and the organic layer may also comprise etching the hydrophobic protection layer (which is stacked between the organic layer and the shielding layer), thereby forming a patterned hydrophobic protection layer.
A method in accordance with embodiments of the present invention may advantageously be used in a process for fabricating organic semiconductor based devices and circuits, such as for example organic photodetectors (OPD), e.g. multicolour OPDs, organic thin-film transistors (OTFT) or organic light-emitting diodes (OLED), e.g. multicolour OLEDs. A method in accordance with embodiments of the present invention may for example be used in a fabrication process for OLED displays, e.g. multicolour OLED displays, allowing obtaining higher resolutions than with the currently used shadow masking technology. For example, a method in accordance with embodiments of the present invention may also be used for patterning of micron sized or sub-micron sized pixel arrays of organic CMOS imagers. A method in accordance with embodiments of the present invention may advantageously be used for fabricating organic smart pixels, e.g. comprising at least one OLED sub-pixel element and at least one OPD sub-pixel element, including arrays of such devices.
A method in accordance with embodiments of the present invention may advantageously be used in fabrication processes for organic electronic devices requiring high resolution, such as for example high definition full colour OLED displays (e.g. for application in mobile electronics, television or viewfinder), high definition full colour organic photodetectors and photodetector arrays (e.g. for imager applications), or smart pixels or pixel arrays with multiple integrated organic photodetector and organic light emitting diode sub-pixel elements. A method in accordance with embodiments of the present invention may for example be used in a fabrication process for high resolution organic ultrasonic emitting arrays (e.g. for ultrasonic image applications).
It is an advantage of a method in accordance with embodiments of the present invention that it allows using conventional photolithographic products (photoresists, developers) already used in the microelectronics industry. It is an advantage that there is no need for using expensive products such as fluorinated photoresists.
It is an advantage of a method in accordance with embodiments of the present invention that the hydrophobic protection layer reduces water intake in the underlying organic layers and protects the underlying organic layers during the photolithographic process. It is an advantage that this may result in a substantially longer operational lifetime of a patterned organic device such as a patterned OLED as compared to an organic device that is patterned without using a hydrophobic protection layer.
It is an advantage of a method in accordance with embodiments of the present invention that it is up-scalable and that it is compatible with existing semiconductor process lines.
It is an advantage of a method in accordance with embodiments of the present invention that the highest processing temperature used for patterning of the organic layer may be below 150° C., or even below 110° C. Therefore the method may be used on flexible foil substrates such as for example a polyethylene naphthalate (PEN) foil or a polyethylene terephthalate (PET) foil, thus enabling the fabrication of flexible organic devices and circuits with high resolution.
It is an advantage of a method in accordance with embodiments of the present invention that it may be cost effective and well controllable.
It is an advantage of a method in accordance with embodiments of the present invention that it may be used for patterning organic layers that degrade when exposed to water, the method avoiding or strongly reducing the risk of such degradation.
Certain objects and advantages of various inventive aspects have been described herein above. Of course, it is to be understood that not necessarily all such objects or advantages may be achieved in accordance with any particular embodiment of the invention. Thus, for example, those skilled in the art will recognize that the invention may be embodied or carried out in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other objects or advantages as may be taught or suggested herein. Further, it is understood that this summary is merely an example and is not intended to limit the scope of the disclosure. The disclosure, both as to organization and method of operation, together with features and advantages thereof, may best be understood by reference to the following detailed description when read in conjunction with the accompanying drawings.
Particular and preferred aspects of the invention are set out in the accompanying independent and dependent claims. Features from the dependent claims may be combined with features of the independent claims and with features of other dependent claims as appropriate and not merely as explicitly set out in the claims.
These and other aspects of the invention will be apparent from and elucidated with reference to the embodiment(s) described hereinafter.
Any reference signs in the claims shall not be construed as limiting the scope of the present invention.
In the different drawings, the same reference signs refer to the same or analogous elements.
The drawings are only schematic and are non-limiting. In the drawings, the size of some of the elements may be exaggerated and not drawn on scale for illustrative purposes.
The present invention will be described with respect to particular embodiments and with reference to certain drawings but the invention is not limited thereto but only by the claims. The drawings described are only schematic and are non-limiting. In the drawings, the size of some of the elements may be exaggerated and not drawn on scale for illustrative purposes. The dimensions and the relative dimensions do not correspond to actual reductions to practice of the invention.
Furthermore, the terms first, second and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequence, either temporally, spatially, in ranking or in any other manner. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein.
It is to be noticed that the term “comprising”, used in the claims, should not be interpreted as being restricted to the means listed thereafter; it does not exclude other elements or steps. It is thus to be interpreted as specifying the presence of the stated features, integers, steps or components as referred to, but does not preclude the presence or addition of one or more other features, integers, steps or components, or groups thereof. Thus, the scope of the expression “a device comprising means A and B” should not be limited to devices consisting only of components A and B. It means that with respect to the present invention, the only relevant components of the device are A and B.
Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment, but may. Furthermore, the particular features, structures or characteristics may be combined in any suitable manner, as would be apparent to one of ordinary skill in the art from this disclosure, in one or more embodiments.
Similarly it should be appreciated that in the description of exemplary embodiments of the invention, various features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of one or more of the various inventive aspects. This method of disclosure, however, is not to be interpreted as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all features of a single foregoing disclosed embodiment. Thus, the claims following the detailed description are hereby expressly incorporated into this detailed description, with each claim standing on its own as a separate embodiment of this invention.
Furthermore, while some embodiments described herein include some but not other features included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the invention, and form different embodiments, as would be understood by those in the art. For example, in the following claims, any of the claimed embodiments can be used in any combination.
In the description provided herein, numerous specific details are set forth in order to provide a thorough understanding of the invention and how it may be practiced in particular embodiments. However, it is understood that embodiments of the invention may be practiced without these specific details. In other instances, well-known methods, structures and techniques have not been shown in detail in order not to obscure an understanding of this description.
In the context of the present disclosure, hydrophobic means water repellent. A hydrophobic surface is a water repelling surface, characterized by a water contact angle exceeding 90°. The water contact angle is the angle at which a surface of a water droplet provided on a solid surface meets the solid surface. In the context of the present disclosure, a hydrophobic layer is a layer having a hydrophobic surface.
In the context of the present disclosure, a shielding layer or a water soluble shielding layer is a water soluble layer that can be removed by exposure to water or to a solution comprising water. The shielding layer may comprise or contain a water based polymer material that is not cross linkable. For example, the shielding layer may comprise any of or any combination of polyvinyl pyrrolidone, polyvinyl alcohol, water-soluble cellulose, polyethylene glycol, polyglycerin or pullullan, embodiments of the present invention not being limited thereto. The shielding layer material may further comprise a solvent comprising water and/or a water soluble alcohol.
In the context of the present disclosure, a pixel refers to a single image point in an imager or a display. In an imager or a display a plurality of pixels is typically arranged in rows and columns. Each pixel may be composed of sub-pixels, each sub-pixel for example corresponding to a different colour. Each sub-pixel comprises a pixel element, for example a light emitting element such as an OLED or a photo-detecting element such as an organic photodetector.
In the context of the present disclosure, a charge transport layer is a layer, e.g. an organic semiconductor layer, having a charge mobility higher than 10−6 cm−2/Vs.
The present invention provides a method for photolithographic patterning of an organic layer on a substrate. The method comprises: providing a water soluble shielding layer over the organic layer, providing a photoresist layer on the shielding layer, photolithographic patterning of the photoresist layer to thereby form a patterned photoresist layer, etching the shielding layer and the organic layer, using the patterned photoresist layer as a mask, to thereby form a patterned shielding layer and a patterned organic layer, and afterwards removing the shielding layer by exposure to water or to a solution comprising water. A method of the present invention further comprises, before providing the water soluble shielding layer, providing on the organic layer a hydrophobic protection layer, e.g. hydrophobic organic semiconductor layer, having a hydrophobic upper surface. As a result of photolithographic patterning according to a method of the present invention, a patterned layer stack comprising a patterned organic layer and a patterned hydrophobic protection layer, e.g. hydrophobic organic semiconductor layer, is obtained. The organic layer may be a single layer or a multilayer stack comprising at least two layers. The hydrophobic protection layer may be a single layer or a multilayer stack comprising at least two layers.
Next, a hydrophobic protection layer 12, i.e. a protection layer 12 having a hydrophobic upper surface 121, is provided, e.g. evaporated, on the organic layer 11, as illustrated in
When fabricating an organic electronic device wherein an organic layer, e.g. an active organic semiconductor layer, is patterned according to embodiments of the present invention, the hydrophobic protection layer 12 may remain in the device. In such embodiments the hydrophobic protection layer 12 is preferably a hydrophobic organic semiconductor layer. In an organic electronic device, such as a light emitting device or a light detecting device, the hydrophobic organic semiconductor layer (protection layer 12) may for example have the function of a charge transport layer, i.e. a hole transport layer or an electron transport layer. In such embodiments, the hydrophobic organic semiconductor protection layer 12 may preferably have appropriate HOMO and LUMO energy levels to enable good carrier injection into the active organic semiconductor layer. In such embodiments, the hydrophobic organic semiconductor protection layer 12 may preferably have good charge transport properties, e.g. a charge carrier mobility larger than 10−6 cm2/Vs, preferably larger than 10−4 cm2/Vs, preferably larger than 10−3 cm2/Vs, preferably larger than 10−2 cm2/Vs, such that it can function as an electron transport layer or as a hole transport layer in the final organic electronic device.
The hydrophobic protection layer 12 may consist of a single layer or it may be a multilayer stack, i.e. a stack comprising two or more layers. The hydrophobic protection layer 12 may be a doped layer or a non-doped layer or a partially doped layer. In embodiments in which the protection layer is present at a light emitting side of the device, e.g. for a light emitting device such as an OLED, or at a light receiving side of the device, e.g. for a light detecting device such as an OPD or OPV device, the protection layer 12 may preferably have a good transparency, such as e.g. a transparency higher than 95%, preferably higher than 98%, e.g. at least 99%, at the wavelength or in the range of wavelengths emitted, respectively absorbed, by the device.
For example, the hydrophobic protection layer 12 may be a stack comprising a NET18 first electron transport layer 128 and a doped DFH-4T second electron transport layer 129, in which the protection layer 12 may be provided on an organic emission layer (organic layer 11) of an organic light emitting device. The DFH-4T layer can function as an electron transport layer and as a hydrophobic layer. It has good electron transport properties (electron mobility about 0.64 cm2/Vs) and good hydrophobic properties (contact angle with water of 122 degrees). It can repel water and reduce water intake of the layers underneath. The first electron transport layer 128 may be provided for establishing a good contact to the emission layer (active organic semiconductor layer 11) of the OLED and may preferably have a good energy level matching with the emission layer to enable efficient charge injection from the first electron transport layer 128 into the emission layer. The LUMO level of (undoped) DFH-4T is too low for electron injection from the DFH-4T layer into an (undoped) NET18 layer. Therefore the DFH-4T layer 129 may be n-doped, for example with a conductive dopant such as for example NDN26, which can reduce the energy barrier at the interface between the NET18 layer 128 and the DFH-4T layer 129. An upper part or upper portion 127 of the first electron transport layer 128 may be n-doped too (e.g. with the same dopant, e.g. NDN26) to further improve electron injection from the DFH-4T layer 129 into the first electron transport layer 128. In this example, the stack of the DFH-4T layer 129 and the (partially doped) first electron transport layer 128 may form the protection layer 12. The thickness of the DFH-4T layer may for example be in the range between 10 nm and 50 nm, embodiments of the present invention not being limited thereto. This combination of materials can be used in OLEDs of different colours, such as in red, green and blue OLEDs, for example. Other suitable materials may be used for forming the electron transport layer, the hydrophobic protection layer and the dopant.
Some examples of organic materials that may be used as a material for the hydrophobic charge transport layer, more in particular hydrophobic electron transport layer, are: 5,5′-Bis((5-perfluorohexyl)thiophen-2-yl)-2,2′-bithiophene (DFH-4T), Copper(II) 1,2,3,4,8,9,10,11,15,16,17,18,22,23,24,25-hexadecafluoro-29H,31H-phthalocyanine (F16CuPC), and N,N′-Bis(2,2,3,3,4,4,4-heptafluorobutyl)-3,4,9,10-perylene dicarboximide (PTCPI-CH2C3F7), embodiments of the present invention not being limited thereto.
Some examples of organic materials that may be used as a material for the hydrophobic charge transport layer, more in particular hydrophobic hole transport layer, are: 5,5′-Bis(3-hexyl-2-thienyl)-2,2′-bithiophene (DH-4T), diphenyl-dinaphtho[2,3-b:2′,3′-f]thieno[3,2-b]thiophene (DphDNTT), dinaphtho[2,3-b:2′,3′-f]thieno[3,2-b]thiophene (DNTT), N2,N7-Di(naphthalen-1-yl)-9,9-dioctyl-N2,N7-diphenyl-9H-fluorene-2,7-diamine (DOFL-NPB), N,N′-Bis(3-methylphenyl)-N,N′-bis(phenyl)-9,9-dioctylfluorene (DOFL-TPD), 2,3,8,9,14,15-Hexafluorodiquinoxalino[2,3-a:2′,3′-c]phenazine (HATNA-F6), 2,7-Bis[9,9-di(4-methylphenyl)-fluoren-2-yl]-9,9-di(4-methylphenyl)fluorene (TDAF), N,N′-Dioctyl-3,4,9,10-perylenedicarboximide (PTCDI-C8), and N,N′-Ditridecyl-3,4,9,10-perylenedicarboximide (PTCDI-C13), embodiments of the present invention not being limited thereto.
A layer of a material listed above may be provided in combination with a charge transport layer to form the protection layer (multilayer stack) 12, for example as illustrated in
After having provided the protection layer 12, a water soluble shielding layer 13 is provided on the protection layer 12, as illustrated in
The shielding layer 13 may be provided by a solution based process such as for example spin coating, slot die coating or blade coating. Subsequently a soft bake, e.g. a hot plate soft bake, for example at a temperature in the range between 90° C. and 110° C. may be done. However, such soft bake step may be omitted and drying of the shielding layer 13 may be done at ambient temperature. It was surprisingly found that a water containing shielding layer can be spin coated with a good uniformity on the hydrophobic surface of the protection layer 12. As an alternative to solution based processing, the shielding layer 13 may be provided by evaporation.
Next, a photoresist layer 14 may be spin coated on the shielding layer 13, followed by a soft bake step, such as for example a hot plate soft bake step for 1 minute at 100° C. The photoresist layer 14 comprises a photoresist that may be developed in a solvent based developer. The photoresist is preferably a negative tone resist. However, embodiments of the present invention are not limited thereto and the photoresist may be a positive tone resist. A cross section of the resulting structure is shown in
The photoresist layer 14 may then be exposed to light, e.g. UV light, through a shadow mask and developed. After development of the photoresist, the structure shown in
The shielding layer 13, the protection layer 12 and the organic layer 11 are then etched, thereby using the patterned photoresist layer 141 as a mask. As illustrated in the example shown in
Finally, the patterned shielding layer 131 may be removed, e.g. by exposure to water or a water based solution, for instance a solution of water (90%) and IPA (10%) or a mixture of water (90%), IPA (5%) and Glycerin (5%), for example by spin-coating a water layer or a water based solution on the device. The patterned photoresist layer 141 may be removed before exposure of the shielding layer to water. Alternatively, the patterned photoresist layer 141 may be removed together with the patterned shielding layer 131 when it is exposed to water. This results in a stack of a photolithographically patterned organic layer 111 and a photolithographically patterned protection layer 121 on the substrate 10, as illustrated in
In embodiments of the present invention, the etching process for patterning the shielding layer 13, the protection layer 12 and the organic layer 11 may be a single etching step or it may comprise a sequence of at least two etching steps. An example of such a process comprising a sequence of etching steps is schematically illustrated in
After complete removal of the shielding layer 12 at the exposed locations (i.e. at locations where no photoresist layer 141 was present anymore), a second dry etching step may be done. In advantageous embodiments of the present invention, the second dry etching step may be a continuation of the first dry etching step. The second dry etching step may for example comprise reactive ion etching using an oxygen plasma. The second dry etching step thus may result in a complete removal of the protection layer 12 and the organic layer 11 at the exposed locations (i.e. at the locations where no shielding layer is present any more). Simultaneously, the thinned photoresist layer 142 (if present) may be completely removed, as well as an upper portion of the patterned shielding layer 131, resulting in a thinned shielding layer 132. By properly selecting the thickness of the shielding layer in view of the thickness of the protection layer 12 and of the organic material layer 11 (and taking into account the corresponding etch rates), after complete removal of the protection layer 12 and the organic layer 11 at the locations not covered by the patterned shielding layer 131, there may still remain a thinned layer 132 of the shielding material. This is schematically illustrated in
Finally, the remaining shielding material layer 132 may be removed in water or a water based solution, for instance a solution of water (90%) and IPA (10%) or a mixture of water (90%), IPA (5%) and Glycerin (5%), for example by spin-coating a water layer or a water based solution on the device. This results in a stack of a photolithographically patterned organic layer 111 and a photolithographically patterned protection layer 121 on the substrate 10, as illustrated in
An example of a method for fabricating an OLED, in which the active organic semiconductor layer (electroluminescent layer) is patterned according to embodiments of the present invention, is schematically illustrated in
Experiments were done wherein the operational lifetime of OLEDs that were patterned using a method according to embodiments of the present invention was compared to the operational lifetime of OLEDs that were patterned using a water based shielding layer but without a protection layer. The OLEDs had a 20 nm thick TATP light emission layer doped with Ir(MDQ)2 (5%). For the OLEDs fabricated using a method according to embodiments of the present invention, a multilayer protection layer 12 was used, more in particular a stack consisting of a 30 nm thick NET18 layer (first electron transport layer 128) and a 15 nm thick DFH-4T hydrophobic layer (second electron transport layer 129) doped with NDN26 (5%). A lower portion 126 of the NET18 layer (i.e. the portion in contact with the emission layer) was undoped and had a thickness of 20 nm and an upper portion 127 of the NET18 layer (i.e. the portion in contact with the doped DFH4T layer) was doped with NDN26 (5%) and had a thickness of 10 nm.
For measuring the operational lifetime, the OLEDs were driven by a current with a current density up to 50 mA/cm2. The initial light intensity emitted by the OLEDs was recorded and the light degradation was monitored continuously until the emitted light intensity dropped to 50% of the initial light intensity. The operational lifetime corresponds to the time period T50 after which the emitted light intensity is reduced to 50% of the initial light intensity, at a constant bias current (50 mA/cm2 in the example shown). The measured results are shown in
Embodiments of the present invention may advantageously be used in a method for fabricating a device comprising a first patterned organic device layer at a first location, e.g. at first locations, and a second patterned organic device layer at a second location, e.g. at second locations, on a substrate, e.g. on a single substrate. The first location, e.g. first locations, and the second location, e.g. second locations may be non-overlapping.
An example of a method for fabricating an organic device comprising a first patterned organic layer at a first location, e.g. at first locations, a second patterned organic layer at a second location, e.g. second locations, and a third patterned organic layer at a third location, e.g. third locations, in accordance with embodiments of the present invention is schematically illustrated in
As an example, process steps for the fabrication of a device, e.g. a three-colour OLED device, comprising a first patterned device layer at a first location on a substrate, e.g. for providing a first colour (first sub-pixel), and a second patterned device layer at a second location on the substrate, e.g. for providing a second colour (second sub-pixel), are shown. This exemplary process further comprises a third patterned device layer, e.g. at a third location on the substrate, e.g. for providing a third colour (third sub-pixel). Thus the exemplary process particularly may form part of a manufacture process for fabricating a three-colour OLED. The figures show cross sections corresponding to a single OLED pixel comprising three sub-pixels.
However, it shall be understood that an OLED device may comprise a large number of such pixels, each comprising three such sub-pixels, the pixels being for example arranged in a pixel grid or array. A process according to embodiments of the present invention may thus be used for fabricating a plurality of three-colour OLEDs, corresponding to a plurality of pixels, on a single substrate, such as for example an array of three-colour OLEDs, e.g. arranged in a plurality of rows and a plurality of columns. More in general, a process according to embodiments of the present invention may be used for the formation of patterned layer stacks with different properties side by side, e.g. for providing different colours in an OLED or in an OPD or for providing various functionalities in a circuit, and for the fabrication of arrays of such patterned multilayer stacks.
The exemplary method according to embodiments of the present disclosure, illustrated in the drawings, comprises depositing an initial shielding layer 60 on the substrate 10 (
The exemplary method according to embodiments of the present invention comprises patterning the initial shielding layer 60, thereby removing the initial shielding layer at the first location. As illustrated in
In a next step, illustrated in
In embodiments according to the present invention, e.g. in the example described here relating to a three-colour OLED, the first device layer 71 may for example be a layer stack, e.g. comprising a hole injection layer, an electron blocking layer, a hole transport layer and an electroluminescent organic layer, the present disclosure not being limited thereto. The first device layer 71 may comprise at least a first electroluminescent organic layer. The first device layer 71 may be deposited by solution processing (e.g. spin-coating, printing, spray-coating, slot die coating and/or blade coating), gas phase deposition (e.g. CVD or OVPD) or vacuum deposition (e.g. evaporation).
After deposition of the first device layer 71, a first hydrophobic protection layer 81 is deposited on the first device layer 71 and a first shielding layer 61 is deposited on the first hydrophobic protection layer 81, as illustrated in
Next, as illustrated in
Using the patterned photoresist layer 141 as a mask, an etching step is done, thereby locally removing the first shielding layer 61 and the underlying layers, e.g. the first hydrophobic protection layer 81, the first device layer 71 and the initial shielding layer 60. The first shielding layer 61 and the underlying layers are thereby removed at the second location, e.g. forming a second opening 2 through these layers only at the location of the second bottom electrode 52, thereby exposing the second bottom electrode 52. This is schematically illustrated in
Next a second organic device layer 72 is deposited, e.g. over substantially the entire substrate (as illustrated in
After deposition of the second organic device layer 72, in the example shown in
Using the patterned photoresist layer 141 as a mask, an etching step is done, thereby locally removing the second shielding layer 62 and the underlying layers, e.g. the second hydrophobic protection layer 82, the second device layer 72, the first shielding layer 61, the first hydrophobic protection layer 81, the first device layer 71 and the initial shielding layer 60. The second shielding layer 62 and the underlying layers are thereby removed at the third location, thereby forming a third opening 3 through these layers at the location of the third bottom electrode 53, thereby exposing the third bottom electrode 53. This is schematically illustrated in
In a next step, illustrated in
After deposition of the third organic device layer 73, in the example shown in
Next the different layers may be removed at respective locations where they are not needed in the final device. To that extent, as illustrated in
Using the patterned photoresist layer 141 as a mask, an etching step is done, thereby locally removing the third shielding layer 63 and the underlying layers, as illustrated in
Next the photoresist layer 141 may be removed and all superfluous layers may be removed by applying a water based solution that dissolves the shielding layers 60, 61, 62 and 63. After treating the sample with the dissolving solution, a structure as shown in
Next, additional layers are deposited to from a three-colour OLED device. For example, in embodiments wherein the first patterned device layer 711, the second patterned device layer 721 and the third patterned device layer 731 comprise a stack of e.g. a hole injection layer, a hole transport layer and an electroluminescent layer, depositing the additional layers may comprise depositing, e.g. evaporating, an electron transport layer, an electron injection layer and a cathode layer. For example, in embodiments wherein the first patterned device layer 711, the second patterned device layer 721 and the third patterned device layer 731 comprise a stack of e.g. a electron injection layer, an electron transport layer and an electroluminescent layer, depositing the additional layers may comprise depositing, e.g. evaporating, a hole transport layer, a hole injection layer and an anode layer.
The foregoing description details certain embodiments of the invention. It will be appreciated, however, that no matter how detailed the foregoing appears in text, the present invention may be practiced in many ways. It should be noted that the use of particular terminology when describing certain features or aspects of the invention should not be taken to imply that the terminology is being re-defined herein to be restricted to including any specific characteristics of the features or aspects of the invention with which that terminology is associated.
Whereas the above detailed description as well as the summary of the invention has been focused on a method for fabricating a device, the present disclosure also relates to a device comprising patterned layers obtained using a method according to any of the embodiments as described above.
While the above detailed description has shown, described, and pointed out novel features of the invention as applied to various embodiments, it will be understood that various omissions, substitutions, and changes in the form and details of the device or process illustrated may be made by those skilled in the technology without departing from the disclosure.
| Number | Date | Country | Kind |
|---|---|---|---|
| 15174309.3 | Jun 2015 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2016/064898 | 6/27/2016 | WO | 00 |
