Selective pixel design for advanced patterning

Abstract

Embodiments of the present disclosure herein generally relate to sub-pixel circuits and methods of forming sub-pixel circuits that may be utilized in a display such as an organic light-emitting diode (OLED) display. In one embodiment, a device is disclosed. The device includes a pixel-defining layer (PDL) structure disposed over the substrate, defining an anode, and an overhang structure thereover. The PDL structure has a first PDL region, a second PDL region opposing the first PDL region, a third PDL region, and a fourth PDL region opposing the third PDL region. At least one sub-pixel is defined by the overhang structure, and includes a cathode. The cathode contacts at least one of the first sidewall and the second sidewall at a first thickness, and the third sidewall and the fourth sidewall at a second thickness. The first thickness is greater than the second thickness.

Description

PATENTAttorney Docket No.: 44025804W001SELECTIVE PIXEL DESIGN FOR ADVANCED PATTERNING BACKGROUNDField

[0001] Embodiments described herein generally relate to a display. More specifically, embodiments described herein relate to sub-pixel circuits and methods of forming sub-pixel circuits that may be utilized in a display such as an organic lightemitting diode (OLED) display.Description of the Related Art

[0002] Input devices including display devices may be used in a variety of electronic systems. An organic light-emitting diode (OLED) is a light-emitting diode (LED) in which the emissive electroluminescent layer is a film of an organic compound that emits light in response to an electric current. OLED devices are classified as bottom emission devices if light emitted passes through the transparent or semitransparent bottom electrode and substrate on which the panel was manufactured. Top emission devices are classified based on whether or not the light emitted from the OLED device exits through the lid that is added following the fabrication of the device. OLEDs are used to create display devices in many electronics today. Today’s electronics manufacturers are pushing these display devices to shrink in size while providing higher resolution than just a few years ago.

[0003] Accordingly, what is needed in the art are pixel architectures that deliver enhanced resolution while preserving electrical reliability of the device.SUMMARY

[0004] Embodiments described herein generally relate to a display. More specifically, embodiments described herein relate to sub-pixel circuits and methods of forming sub-pixel circuits that may be utilized in a display such as an organic lightemitting diode (OLED) display.

[0005] In one embodiment, a device is disclosed. The device includes a substrate. A pixel-defining layer (PDL) structure is disposed over the substrate. The PDL structure defines an anode. An overhang structure is disposed over the PDL structure. A first PDL region is located between a first intersection point of the anode and thePATENTAttorney Docket No.: 44025804W001PDL structure and a first sidewall of the overhang structure. A second PDL region is located between a second intersection point of the anode and the PDL structure and a second sidewall of the overhang structure. The second PDL region opposes the first PDL region. A third PDL region is located between a third intersection point of the anode and the PDL structure and a third sidewall of the overhang structure. A fourth PDL region is located between a fourth intersection point of the anode and the PDL structure and a fourth sidewall of the overhang structure. The fourth PDL region opposes the third PDL region. At least one sub-pixel is defined by the overhang structure, and includes an organic light emitting (OLE) material and a cathode. The cathode contacts at least one of the first sidewall and the second sidewall at a first cathode endpoint, and the third sidewall and the fourth sidewall at a second cathode endpoint. The cathode has a first thickness along at least one of the first sidewall and the second sidewall, and a second thickness along the third sidewall and the fourth sidewall. The first thickness is greater than the second thickness.

[0006] In another embodiment, a device is disclosed. The device includes a substrate. A pixel-defining layer (PDL) structure is disposed over the substrate. The PDL structure defines an anode. An overhang structure is disposed over the PDL structure. The overhang structure has an overhang profile. A first PDL region is located between a first intersection point of the anode and the PDL structure and a first sidewall of the overhang structure. A second PDL region is located between a second intersection point of the anode and the PDL structure and a second sidewall of the overhang structure. The second PDL region opposes the first PDL region. A third PDL region is located between a third intersection point of the anode and the PDL structure and a third sidewall of the overhang structure. A fourth PDL region is located between a fourth intersection point of the anode and the PDL structure and a fourth sidewall of the overhang structure. The fourth PDL region opposes the third PDL region. The first PDL region, the second PDL region, the third PDL region, and the fourth PDL region define a PDL profile. The PDL profile has a different geometry than the overhang profile. At least one sub-pixel is defined by the overhang structure, and includes an organic light emitting (OLE) material and a cathode.

[0007] In another embodiment, a method of fabricating a device is disclosed. The method includes disposing a first photoresist over a pixel defining layer (PDL) material.PATENTAttorney Docket No.: 44025804W001The first photoresist is patterned to form a plurality of first openings, thereby exposing portions of an upper surface of the PDL material. The PDL material is etched to form PDL structures having anodes exposed therebetween. The PDL structures have a PDL profiled defined by a first PDL region, a second PDL region, a third PDL region, and a fourth PDL region. A lower portion layer is disposed over the PDL structures and the anodes, and an upper portion layer is disposed over the lower portion layer. A second photoresist is disposed over the upper portion layer. The second photoresist is patterned to form a plurality of second openings, thereby exposing regions of the upper portion layer. The upper portion layer and the lower portion layer are etched through the second openings to form overhang structures. Each overhang structure has an overhang profile. Each overhang profile the overhang profile defined by a first sidewall, a second sidewall, a third sidewall, and a fourth sidewall. The overhang profile and the PDL profile have different geometries.BRIEF DESCRIPTION OF THE DRAWINGS

[0008] So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only exemplary embodiments and are therefore not to be considered limiting of its scope, and may admit to other equally effective embodiments.

[0009] Figure 1A is a schematic, cross-sectional view of a sub-pixel circuit having a first configuration, according to embodiments.

[0010] Figure 1B is a schematic, cross-sectional view of a sub-pixel circuit having a second configuration, according to embodiments.

[0011] Figure 1C is a schematic, cross-sectional view of an overhang structure of a sub-pixel circuit according embodiments.

[0012] Figure 2A is a schematic, top plan view of pixel array having a first configuration, according to embodiments.PATENTAttorney Docket No.: 44025804W001

[0013] Figure 2B is a schematic, top plan view of pixel array having a second configuration, according to embodiments.

[0014] Figure 2C is a schematic, top plan view of pixel array having a third configuration, according to embodiments.

[0015] Figure 3A is a cross-sectional view of the sub-pixel circuit at section line SA- SA, according to embodiments.

[0016] Figure 3B is a cross-sectional view of the sub-pixel circuit at section line 3B- 3B, according to embodiments.

[0017] Figure 4 is a flow diagram of a method of forming a sub-pixel circuit, according to embodiments.

[0018] Figures 5A-5E are cross-sectional views of a substrate during a method for forming a sub-pixel circuit according embodiments described herein.

[0019] Figures 6A-6E are cross-sectional views of a substrate during a method for forming a sub-pixel circuit according embodiments described herein.

[0020] To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation.DETAILED DESCRIPTION

[0021] Embodiments described herein generally relate to a display. More specifically, embodiments described herein relate to sub-pixel circuits and methods of forming sub-pixel circuits that may be utilized in a display such as an organic lightemitting diode (OLED) display. In particular, the embodiments disclosed herein provide pixel architectures and fabrication techniques for sub-pixel geometries exhibiting enhanced resolution and improved visual uniformity, while addressing electrical challenges associated with such geometries. Embodiments herein include sub-pixels having pixel defining layer (PDL) profiles and overhang profiles that differPATENTAttorney Docket No.: 44025804W001from each other. The PDL profile may be optimized for resolution, while the overhang profile may be optimized for enhanced cathode connection and reduced cross-talk.

[0022] Each of the embodiments described herein of the sub-pixel circuit include a plurality of sub-pixels with each of the sub-pixels defined by adjacent overhang structures that are permanent to the sub-pixel circuit. While the Figures depict two sub-pixels with each sub-pixel defined by adjacent overhang structures, the sub-pixel circuit of the embodiments described herein include a plurality of sub-pixels, such as two or more sub-pixels. Each sub-pixel has OLE (organic light-emitting) materials configured to emit a white, red, green, blue or other color light when energized. E.g., the OLE materials of a first sub-pixel emits a red light when energized, the OLE materials of a second sub-pixel emits a green light when energized, and the OLE materials of a third sub-pixel emits a blue light when energized.

[0023] The overhangs are permanent to the sub-pixel circuit and include at least an second structure disposed over a first structure. The adjacent overhang structures defining each sub-pixel of the sub-pixel circuit of the display provide for formation of the sub-pixel circuit using deposition techniques, such as evaporation deposition, and provide for the overhang structures to remain in place after the sub-pixel circuit is formed. Evaporation deposition may be utilized for deposition of OLE materials (including a hole injection layer (HIL), a hole transport layer (HTL), an emissive layer (EML), and an electron transport layer (ETL)), and cathode. In one embodiment, the HIL layer has a greater conductivity than the HTL layer. In another embodiment, the HIL layer has a greater energy level than the HTL layer. In some instances, an encapsulation layer may be disposed via evaporation deposition. In embodiments including one or more capping layers, the capping layers are disposed between the cathode and the encapsulation layer. The overhang structures and the deposition angle set by the deposition source provide for a shadowing effect during deposition with the deposition angle set by the deposition source. In order to deposit at a particular angle, the deposition source is configured to emit the deposition material at a particular angle with regard to the overhang structure. The encapsulation layer of a respective sub-pixel is disposed over the cathode with the encapsulation layer extending under at least a portion of each of the adjacent overhang structures and along a sidewall of each of the adjacent overhang structures.PATENTAttorney Docket No.: 44025804W001

[0024] Figure 1A is a schematic, cross-sectional view of a sub-pixel circuit 101 having a first configuration 101 A, according to embodiments. The cross-sectional view of Figure 1A is taken along section line 1A-1A of any one of Figures 2A-2C. Figure 1B is a schematic, cross-sectional view of a sub-pixel circuit 101 having a second configuration 101 B, according to embodiments. The cross-sectional view of Figure 1 B is taken along section line 1B-1B of any one of Figures 2A-2C. Figure 1C is a schematic, cross-sectional view of an overhang structure 110 of the sub-pixel circuit 101 having the first configuration 101 A, according to embodiments. Figure 1C is shown in further detail in Figure 3A.

[0025] The sub-pixel circuit 101 includes a substrate 102. In one or more embodiments, the substrate 102 is a backplane. The backplane includes, but is not limited to, a complementary metal-oxide-sem iconductor (CMOS) array, a thin-film transistor (TFT) array, or a glass backplane. Anodes 104 may be patterned on the substrate 102, and are defined by adjacent pixel-defining layer (PDL) structures 126 disposed on the substrate 102. In one embodiment, which can be combined other embodiments described herein, the anodes 104 are pre-patterned on the substrate 102. E.g., the substrate 102 is a pre-patterned indium tin oxide (ITO) glass substrate. The anodes 104 include a metal-containing material. The metal-containing material of the anodes 104 may be, but is not limited to, chromium, titanium, gold, silver, copper, aluminum, ITO, a combination thereof, or other suitably conductive materials.

[0026] The plurality of PDL structures 126 are disposed over the substrate 102. The PDL structures 126 include one of an organic material, an organic material with an inorganic coating disposed thereover, or an inorganic material. The organic material of the PDL structures 126 includes, but is not limited to, polyimides. The inorganic material of the PDL structures 126 includes, but is not limited to, silicon oxide (SiC>2), silicon nitride (SisN4), silicon oxynitride (Si2N2O), magnesium fluoride (MgF2), or combinations thereof. Adjacent PDL structures 126 define a respective sub-pixel 106 and expose the anode 104 of the respective sub-pixel 106. Each adjacent PDL structure 126 has a PDL profile 180 corresponding to the shape of the exposed portion of the anode 104 therein. Various configurations of the PDL profile 180 formed by adjacent PDL structures 126 will be described in greater detail below with reference to Figures 2A-2C.PATENTAttorney Docket No.: 44025804W001

[0027] The sub-pixel circuit 101 has a plurality of sub-pixels 106, including at least a first sub-pixel 108A and a second sub-pixel 108B. While the Figures illustrate the first sub-pixel 108A and the second sub-pixel 108B, the sub-pixel circuit 101 of the embodiments described herein may include two or more sub-pixels 106, such as a third and a fourth sub-pixel. Each sub-pixel 106 has OLE materials configured to emit a white, red, green, blue or other color light when energized. E.g., the OLE materials of the first sub-pixel 108A emits a red light when energized, the OLE materials of the second sub-pixel 108B emits a green light when energized, the OLE materials of a third sub-pixel emits a blue light when energized, and the OLE materials of a fourth sub-pixel emits another color light when energized.

[0028] Each sub-pixel 106 includes an overhang structure 110. The overhang structures 110 are permanent to the sub-pixel circuit 101. The overhang structures 110 further define each sub-pixel 106 of the sub-pixel circuit 101. Each overhang structure 110 includes adjacent overhangs 109. The adjacent overhangs 109 are defined by an overhang extension 109A of a second structure 110B extending laterally past a first structure 110A. The second structure 110B is disposed over the first structure 110A. In one embodiment, the second structure 110B is disposed on the first structure 110A. Each overhang structure 110 has an overhang profile 182. The overhang profile 182 of each overhang structure 110 is defined by the shape of a well 122 between adjacent overhangs 109. Various configurations of the overhang profile 182 formed by the overhang structures 110 will be described in greater detail below with reference to Figures 2A-2C.

[0029] In one embodiment, the overhang structures 110 includes the second structure 110B of a non-conductive inorganic material and the first structure 110A of a conductive inorganic material. In another embodiment, the overhang structures 110 includes the second structure 110B of a conductive inorganic material and the first structure 110A of a conductive inorganic material. The conductive materials of the first structure 110A include aluminum (Al), aluminum neodymium (AINd), molybdenum (Mo), molybdenum tungsten (MoW), copper (Cu), or combinations thereof. The inorganic materials of the second structure include titanium (Ti), silicon nitride (SisN4), silicon oxide (SiC>2), silicon oxynitride (Si2N2O), or combinations thereof. In one embodiment, the first structure is a metal containing material. In one example, thePATENTAttorney Docket No.: 44025804W001metal-containing material is a transparent conductive oxide (TCO) material. The TCO material includes, but is not limited to, indium zinc oxide (IZO), indium tin oxide (ITO), indium gallium zinc oxide (IGZO), or combinations thereof. The overhang structures 110 are able to remain in place, i.e., are permanent.

[0030] In one embodiment, a HIL material 150 of the OLE materials is disposed over and in contact with the anode 104. In one embodiment, the HIL material 150 is different from the material of the first structure 110A and the second structure 110B. An additional OLE material 112 is disposed over the HIL material 150 and extends past an endpoint of the HIL material 150. In one embodiment, the additional OLE material is disposed on the HIL material 150. In one embodiment, the additional OLE material 112 is different from the material of the first structure 110A and the second structure 110B. The overhang structures 110 and deposition angle define an OLE endpoint 158 and a cathode endpoint 166. The overhang structures 110 provide for a shadowing effect during deposition at an angle. Deposition angles are set by the deposition source. The deposition source may be an evaporation source. The additional OLE material 112 and cathode 114 are deposited via evaporation deposition.

[0031] Adjacent overhangs 109 are defined by the overhang extension 109A of the second structure 110B. At least a bottom surface 107 of the second structure 110B is wider than an upper surface 105 of the first structure 110A to form the overhang extension 109A (as shown in Figure 1C) of the overhang 109. The second structure 110B is disposed over an upper surface 105 of the first structure 110A. The overhang extension 109A of the second structure 110B forms the overhang 109 and allows for the second structure 110B to shadow the first structure 110A. The shadowing of the overhang 109 provides for deposition of each of the HIL material 150, the additional OLE material 112, and a cathode 114. Each of the HIL material 150 and the additional OLE material 112 are disposed under the overhang 109. The cathode 114 is disposed over the additional OLE material 112 and extends under the adjacent overhang 109.

[0032] In one embodiment, the HIL material 150 is disposed over and in contact with the anodes 104 and the upper surface 103 of the PDL structure 126. The additional OLE material 112 is disposed over the HIL material 150. In onePATENTAttorney Docket No.: 44025804W001embodiment, the additional OLE material 112 is disposed on the HIL material 150. The additional OLE material extends under the adjacent overhang 109 and is disposed over a first portion of the first structure 110A.

[0033] The cathode 114 includes a conductive material, such as a metal. E.g., the cathode 114 includes, but is not limited to, silver, magnesium, chromium, titanium, aluminum, ITO, or a combination thereof. In one embodiment, material of the cathode 114 is different from the material of the first structure 110A and the second structure 110B.

[0034] Each sub-pixel 106 includes an encapsulation layer 116. The encapsulation layer 116 may be or may correspond to a local passivation layer. The encapsulation layer 116 of a respective sub-pixel is disposed over the cathode 114 (and additional OLE material 112) with the encapsulation layer 116 extending under at least a portion of each of the overhangs 109 and along a sidewall of each of the first structure 110A and the second structure 110B. The encapsulation layer 116 includes the non-conductive inorganic material, such as the silicon-containing material. The silicon-containing material may include SisN4 containing materials.

[0035] In embodiments including one or more capping layers, the capping layers are disposed between the cathode 114 and the encapsulation layer 116. E.g., a first capping layer and a second capping layer are disposed between the cathode 114 and the encapsulation layer 116. Each of the embodiments described herein may include one or more capping layers disposed between the cathode 114 and the encapsulation layer 116. The first capping layer may include an organic material. The second capping layer may include an inorganic material, such as lithium fluoride. The first capping layer and the second capping layer may be deposited by evaporation deposition. In another embodiment, the sub-pixel circuit 101 further includes at least a global passivation layer 120 disposed over the overhang structure 110 and the encapsulation layer 116. In yet another embodiment, the sub-pixel includes an intermediate passivation layer disposed over the overhang structures 110 of each of the sub-pixels 106, and disposed between the encapsulation layer 116 and the global passivation layer 120.PATENTAttorney Docket No.: 44025804W001

[0036] Figures 2A-2C are schematic, top views of a pixel array 100. Figure 2A is a schematic, top view of a pixel array 100 having a first configuration 100A. Figure 2B is a schematic, top view of a pixel array 100 having a second configuration 100B. Figure 2C is a schematic, top view of a pixel array 100 having a third configuration 100C. The pixel array 100 includes a plurality of sub-pixel circuits 101. As shown in Figures 2A-2C, each sub-pixel circuit 101 includes at least two sub-pixels 106. It should be understood that the pixel array 100 may include any number of sub-pixel circuits 101 , such as thousands, or such as millions of sub-pixel circuits 101. Figures 2A-2C show the pixel array 100 prior to the deposition of the encapsulation layer 116.

[0037] The pixel array 100 includes the plurality of adjacent PDL structures 126 disposed over the substrate 102. Adjacent PDL structures 126 define an anode 104 therebetween. The anodes 104 and the PDL structure 126 intersect at an intersection point 140. Each anode 104 includes, at least, a first intersection point 140A, a second intersection point 1406, a third intersection point 140C, and a fourth intersection point 1400. The first intersection point 140A opposes the second intersection point 1406. The third intersection point 140C opposes the fourth intersection point 1400. The intersection points 140A, 1406, 140C, 140D define the exposed portion of the anode 104 therebetween.

[0038] The overhang structures 110 are disposed over an upper surface 103 of the PDL structures 126. Each overhang structure 110 has the second structure 110B disposed over the first structure 110A. The first structure 110A of each sub-pixel 106 of the pixel array 100 includes a first sidewall 212 opposing a second sidewall 214, and a third sidewall 216 opposing a fourth sidewall 218. The first sidewall 212 has a first length L1, extending from the third sidewall 216 to the fourth sidewall 218. The second sidewall 214 has a second length L2, extending from the third sidewall 216 to the fourth sidewall 218. The third sidewall 216 has a third length L3, extending from the first sidewall 212 to the second sidewall 214. The fourth sidewall 218 has a fourth length L4, extending from the first sidewall 212 to the second sidewall 214.

[0039] The PDL structures 126 have a plurality of PDL regions, including, at least, a first PDL region 126A, a second PDL region 126B, a third PDL region 126C, and a fourth PDL region 126D. Each of the PDL regions 126A, 126B, 126C, 126D arePATENTAttorney Docket No.: 44025804W001located between a respective intersection point 140A, OB, 140C, MOD and sidewall 212, 214, 216, 218. For example, the first PDL region 126A is located between the first intersection point 140A and the first sidewall 212, the second PDL region 126B is located between the second intersection point MOB and the second sidewall 214, the third PDL region 126C is located between the third intersection point 140C and the third sidewall 216, and the fourth PDL region 126D is located between the fourth intersection point MOD and the fourth sidewall 218. In one or more embodiments, at least one of the PDL regions 126A, 126B, 126C, 126D has a varying length therethrough (e.g., the length of the PDL region as between the intersection point and the respective sidewall varies).

[0040] As discussed below in relation to Figure 4, the methods described herein provide for selective patterning of the overhang structure 110 such that each length L1, L2, L3, L4 may be the same, or may be different from each other. For example, as shown in Figures 2A-2C, the first sub-pixel 108A is surrounded by a first sidewall 212A having a first length L1A, a second sidewall 214A having a second length L2A, a third sidewall 216A having a third length L3A, and a fourth sidewall 218A having a length L4A, while the second sub-pixel 108B is surrounded by a first sidewall 212B having a first length L1 B, a second sidewall 214B having a second length L2B, a third sidewall 216B having a third length L3B, and a fourth sidewall 218B having a fourth length L4B. Any combination of the aforementioned lengths may be the same, or different. In one or more embodiments, as illustrated in Figures 2A-2C, L1A and L2A may be substantially the same length, while L3A and L4A may be substantially the same length, and L1B and L2B may be substantially the same length, while L3B and L4B may be substantially the same length.

[0041] In one embodiment, the first sidewall 212 and the second sidewall 214 are oriented parallel to a nozzle direction N, and the third sidewall 216 and the fourth sidewall 218 are oriented perpendicular to the nozzle direction N. The nozzle direction N is perpendicular to (e.g., normal to) a scan direction S. The angle of the sidewalls 212, 214, 216, 218 define an OLE endpoint 158 and a cathode endpoint 166. The overhang structures 110 and the angle of the sidewalls 212, 214, 216, 218 provide for a shadowing effect during deposition at an angle. The second structure 110B has an overhang extension 109A extending laterally past the first sidewall 212, the secondPATENTAttorney Docket No.: 44025804W001sidewall 214, the third sidewall 216 and the fourth sidewall 218 of the first structure 110A to create the overhang 109.

[0042] Each sub-pixel 106 includes the organic light-emitting (OLE) material 112 and the cathode 114 disposed over the additional OLE material 112. The cathode 114 extends under the overhang extension 109A and contacts the first sidewall 212, the second sidewall 214, the third sidewall 216, and the fourth sidewall 218 of the first structure 110A under the overhang extension 109A. The cathode 114 is disposed over the first sidewall 212, the second sidewall 214, the third sidewall 216, and the fourth sidewall 218 to a cathode endpoint 166. In some embodiments, the additional OLE material 112 extends under the overhang extension 109A and contacts the first sidewall 212, the second sidewall 214, the third sidewall 216, and the fourth sidewall 218 of the first structure 110A under the overhang extension 109A. The additional OLE material 112 is disposed over the first sidewall 212, the second sidewall 214, the third sidewall 216 and the fourth sidewall 218 to an OLE endpoint 158.

[0043] In one embodiment, the sub-pixels 106 further include a via hole 220. In one embodiment, the via hole 220 is disposed below the anode 104. A conductive layer is disposed in the via hole 220 to connect the anode 104 to a thin-film transistor (TFT) 222 disposed below the anode 104. The TFT 222 provides a driving current to the plurality of sub-pixels 106. The via hole 220 may be located in a position either underneath the overhang structure 110 (e.g., outside the PDL regions, as shown as via hole 220A in Figure 2), or underneath the PDL structure 126 that does not have an overhang structure 110 thereover (e.g., inside the PDL regions, as shown as via hole 220B in Figure 2).

[0044] Each sub-pixel 106 includes a PDL profile 180 defined by adjacent PDL structures 126. Each PDL profile 180 has a geometry defined by the shape, boundaries, and dimensions of the exposed anode 104. The PDL profile 180 is determined by the patterning of the PDL structure 126 on the substrate 102, as discussed further herein in relation to Figures 4 and 5A-6E. In one embodiment, as illustrated in Figure 2A, the PDL profile 180 is substantially diamond-shaped. The diamond-shaped PDL profile 180 exhibits enhanced resolution and improved visualPATENTAttorney Docket No.: 44025804W001uniformity. However, the PDL profile 180 may be tailored to other shapes, such as square, rectangle, hexagon, or circle, as processing calls for.

[0045] An overhang profile 182 is defined by the overhang structure 110 disposed over the PDL structure 126. As shown in Figures 2A-2C, the overhang profile 182 may have a different geometry than the PDL profile 180, resulting in the overhang structure 110 having a different shape than the PDL profile 180. The first sidewall 212 and the second sidewall 214 have lengths L1 and L2, respectively, that are greater than the either of the lengths L3 and L4 of the third sidewall 216 and the fourth sidewall 218, respectively. Sidewalls that are oriented parallel to the nozzle direction N (e.g., the first sidewall 212 and the second sidewall 214) receive greater deposition coverage of the cathode 114 during the evaporation process, compared to sidewalls normal to the nozzle direction N (e.g., the third sidewall 216 and the fourth sidewall 218). Accordingly, by increasing the first length L1 corresponding to the first sidewall 212, and the second length L2 corresponding to the second sidewall 214, additional surface area is provided for cathode deposition.

[0046] The overhang profile 182, including the first sidewall 212 and the second sidewall 214 having lengths L1 and L2, respectively, is configured to optimize the deposition and contact of the cathode 114 on the first structure 110A. The increased surface area of the sidewalls 212, 214 enhances the electrical contact between the cathode 114 and the first structure 110A. Furthermore, in one or more embodiments, the first length L1 and the second length L2 are greater than either of the third length L3 and the fourth length L4. Minimizing the third length L3 and the fourth length L4 reduces leakage and cross-talk within the pixel array 100, further enhancing image quality and contributing to a clearer display. The volume of the cathode 114 deposited on the sidewalls 212, 214, 216, 218 is described in greater detail with reference to Figures 3A and 3B.

[0047] In one or more embodiments, the PDL profile 180 and the overhang profile 182 of a respective sub-pixel 106 have different geometries (e.g., shapes). By having distinct geometries for the PDL profile 180 and the overhang profile 182, the device may achieve both enhanced viewability and improved electrical characteristics. The PDL profile 180 may be shaped (e.g., diamond-shaped) for enhanced resolution andPATENTAttorney Docket No.: 44025804W001image quality. The overhang profile 182 may be shaped to provide additional area along the first sidewall 212 and the second sidewall 214, providing larger cathode contact for electrical connectivity. Furthermore, by maintaining the third length L3 and the fourth length L4 at smaller dimensions, leakage and cross-talk within the pixel array 100 is reduced. This configuration allows the PDL profile 180 to be optimized for display performance, while the overhang profile 182 is tailored to enhance device reliability.

[0048] Figures 3A and 3B show cross-sectional views of the pixel array 100. FIG.3A is a cross-sectional view of either the first sidewall 212 or the second sidewall 214 of the sub-pixel circuit 101, at section line 3A-3A of any of the Figures 2A-2C. FIG.3A is a cross-sectional view of either the third sidewall 216 or the fourth sidewall 218 of the sub-pixel circuit 101 at section line 3B-3B, at of any of Figures 2A-2C. Figures 3A and 3B show the cross-sections after the deposition of the cathode 114, the additional OLE material 112, and the HIL material 150.

[0049] Referring now to Figure 3A, the first sidewall 212 of the first structure 110A and the second sidewall 214 of the first structure 110A have a cathode thickness ti. The cathode thickness ti is at a midpoint between the cathode endpoint 166 and the OLE endpoint 158 of the first sidewall 212 of the first structure 110A and second sidewall 214 of the first structure 110A. A first cathode volume vi is the total volume of the cathode 114 disposed on the first sidewall 212 and second sidewall 214 from the cathode endpoint 166 to the OLE endpoint 158.

[0050] Referring now to Figure 3B, the third sidewall 216 of the first structure 110A and the fourth sidewall 218 of the first structure 110A have a cathode thickness t2. The cathode thickness t2 is at a midpoint between the cathode endpoint 166 and the OLE endpoint 158 of the third sidewall 216 of the first structure 110A and fourth sidewall 218 of the first structure 110A. A second cathode volume V2 is the total volume of the cathode 114 disposed on the third sidewall 216 and the fourth sidewall 218 from the cathode endpoint 166 to the OLE endpoint 158. In one embodiment, the cathode thickness ti is greater than the cathode thickness t2. In one embodiment, the cathode thickness t2 is about 10% to about 99% of the cathode thickness ti. In one embodiment, the first cathode volume vi of the cathode 114 on the first sidewall 212PATENTAttorney Docket No.: 44025804W001and the second sidewall 214 is greater than the second cathode volume V2 on the third sidewall 216 and the fourth sidewall 218. The second cathode volume V2 on the third sidewall 216 and the fourth sidewall 218 is between about 10% and about 99% of the first cathode volume vi of the cathode 114 on the first sidewall 212 and the second sidewall 214.

[0051] The first sidewall 212 and the second sidewall 214 have an OLE thickness ts. The third sidewall 216 and the fourth sidewall 218 have an OLE thickness t4. The OLE thicknesses t3 and t4 are measured at the OLE endpoint 158.

[0052] The overhang structures 110 provide for cathode endpoints 166 for the first sidewall 212, the second sidewall 214, the third sidewall 216, and the fourth sidewall 218. The cathode endpoints 166 ensure that the cathode 114 is in contact with the first structure 110A of the overhang structure 110, which is conductive to complete the circuit of the pixel array 100. The cathode endpoints 166 on the sidewalls 212, 214, 216, 218 protect the PDL structures 126 from contact to etchant in subsequent processes. The overhang structures 110 provide for OLE endpoints 158 for the first sidewall 212, the second sidewall 214, the third sidewall 216, and the fourth sidewall 218. In some embodiments, the OLE endpoints 158 have an endpoint along the first sidewall 212, second sidewall 214, the third sidewall 216, and the fourth sidewall 218 such that the OLE material 112 does not contact the second structure 110B.

[0053] Figure 4 illustrates a flow diagram of a method 400 for forming a sub-pixel circuit 101. Figures 5A-6E are schematic, cross-sectional views of a substrate 102 during the method 400 for forming the sub-pixel circuit 101. Figures 5A-5E illustrate the formation of the sub-pixel circuit 101 having the first configuration 101 A. Figures 6A-6E illustrate the formation of the sub-pixel circuit 101 having the second configuration 101 B.

[0054] At operation 402, as shown in Figures 5A and 6A, a first photoresist 702 is disposed and patterned through a photolithography operation. The first photoresist 702 is disposed over a PDL material 704. The PDL material 704 includes one of an organic material, an organic material with an inorganic coating disposed thereover, or an inorganic material. The organic material of the PDL material 704 includes, but isPATENTAttorney Docket No.: 44025804W001not limited to, polyimides. The inorganic material of the PDL material 704 includes, but is not limited to, silicon oxide (SiO2), silicon nitride (Si3N4), silicon oxynitride (Si2N2O), magnesium fluoride (MgF2), or combinations thereof.

[0055] The first photoresist 702 is a positive resist or a negative resist. A positive resist includes portions of the resist, which, when exposed to electromagnetic radiation, are respectively soluble to a resist developer applied to the resist after the pattern is written into the resist using the electromagnetic radiation. A negative resist includes portions of the resist, which, when exposed to radiation, will be respectively insoluble to the resist developer applied to the resist after the pattern is written into the resist using the electromagnetic radiation. The chemical composition of the first photoresist 702 determines whether the resist is a positive resist or a negative resist.

[0056] After the first photoresist 702 is deposited over the PDL material 704, the first photoresist 702 is exposed to electromagnetic radiation according to a predetermined pattern. A developer is then applied to the first photoresist 702 to selectively remove the soluble portions, thereby forming a plurality of first openings 703 openings. The plurality of first openings 703 exposes underlying regions of the PDL material 704, corresponding to a position of the PDL material 704 to be etched to form the PDL structures 126.

[0057] At operation 404, as shown in Figures 5B and 6B, the PDL material 704 is etched to form the PDL structures 126. The PDL material 704 is etched through an etching operation. The etching operation may be a dry-etch operation, a wet-etch operation, an isotropic etching operation, or an anisotropic etching operation.

[0058] The patterning of the first photoresist 702, and thereby the etching of the PDL material 704, determines the shape and size of the PDL profile 180 for each subpixel 106. By selectively exposing and etching regions of the PDL structures 126, openings are formed that correspond to the desired PDL profile 180. The openings may produce PDL profiles 180 of various shapes. The various shapes may include, but are not limited to, diamond, square hexagonal, or circular configurations. In one exemplary embodiment, the PDL material 704 is etched to form PDL structures 126 having a diamond-shaped PDL profile 180.PATENTAttorney Docket No.: 44025804W001

[0059] Further, the selective patterning and etching allows for each PDL profile 180 of each sub-pixel 106 to have a different geometric profile and / or dimension from one another, as processing calls for. For example, as shown in Figures 5B and 6B, a first PDL profile 180A of the first sub-pixel 108A is dimensionally different than a fifth PDL profile 180E of the fifth sub-pixel 108E.

[0060] At operation 406, as shown in Figures 5C and 6C, a lower portion layer 706A and an upper portion layer 706B are deposited over the substrate 102. The lower portion layer 706A is disposed over the PDL structures 126 and the metal-containing layer. The upper portion layer 706B is disposed over the lower portion layer 706A. The lower portion layer 706A corresponds to the first structure 110A and the upper portion layer 706B corresponds to the second structural 10B of the inorganic overhang structures 110.

[0061] At operation 408, as shown in Figures 5D and 6D, a second photoresist 710 is disposed and patterned through a photolithography operation. The second photoresist 710 is disposed over the upper portion layer 706B.

[0062] After the second photoresist 710 is deposited over the upper portion layer 706B, the second photoresist 710 is exposed to electromagnetic radiation according to a predetermined pattern. A developer is then applied to the second photoresist 710 to selectively remove the soluble portions, thereby forming a plurality of second openings 711. The plurality of second openings 711 expose underlying regions of the upper portion layer 706B, corresponding to a position of the upper portion layer 706B and the lower portion layer 706A to be etched to form the overhang structures 110. Each overhang structure 110, defining a respective sub-pixel 106, may have a overhang profile 182.

[0063] At operation 410, as shown in Figures 5E and 6E, the upper portion layer 706B and the lower portion layer 706A are etched to form the overhang structures 110. The upper portion layer 706B and the lower portion layer 706A is etched through an etching operation. The etching operation may be a dry-etch operation, a wet-etch operation, an isotropic etching operation, or an anisotropic etching operation.PATENTAttorney Docket No.: 44025804W001

[0064] The patterning of the second photoresist 710, and thereby the etching of the upper portion layer 706B and the lower portion layer 706A, determines the overhang profile 182 of each overhang structure 110. By selectively exposing and etching regions of the upper portion layer 706B and the lower portion layer 706A, the overhang structure 110 is etched to shape the overhang structure 110 to the desired overhang profile 182.

[0065] Further, the selective patterning and etching allows for each overhang profile 182 of each sub-pixel 106 to have a different geometry and / or dimension from one another, as processing calls for. For example, as shown in Figures 5E and 6E, a first overhang profile 182A of the first sub-pixel 108A is dimensionally different than a fifth overhang profile 182E of the fifth sub-pixel 108E.

[0066] The geometry of each overhang structure 110 may be selected such that the first length L1 of the first sidewall 212 and the second length L2 of the second sidewall 214 are chosen to provide sufficient cathode 114 coverage thereon. Providing an overhang profile 182 with sufficient first length L1 and second length L2 provides additional surface area along the first sidewall 212 and the second sidewall 214, facilitating enhanced deposition of the cathode 114 thereon.

[0067] Additionally, the geometry of each overhang structure 110 may be selected such that the third length L3 of the third sidewall 216 and the fourth length L4 of the fourth sidewall 218 may be less than either of the first length L1 and the second length L2. Maintaining smaller dimensions for the third length L3 and the fourth length L4 serves to reduce cross-talk and leakage between adjacent sub-pixels 106 within the pixel array 100. This enhances image quality by minimizing interference between subpixels 106.

[0068] In one or more embodiments, the PDL profile 180 and the overhang profile 182 of a respective sub-pixel 106 have different geometries. The PDL profile 180 is established by the patterning of the PDL structure 126. The PDL profile 180 may be selected for purposes of display performance. In contrast, the overhang profile 182 is shaped by the selective patterning and etching of the overhang structure 110. The overhang profile 182 may be configured to maximize cathode coverage and minimizePATENTAttorney Docket No.: 44025804W001leakage. By allowing the PDL profile 180 to have a different geometry than the overhang profile 182, the pixel array 100 achieves both enhanced visual characteristics and improved electrical properties.

[0069] At optional operation 412, the OLE material 112 and cathode 114 are disposed. The OLE material 112 is deposited within the PDL profile 180 defined by the PDL structures 126. Following deposition of the OLE material 112, the cathode 114 is deposited. The OLE material 112 and the cathode 114 may be deposited by way of evaporation deposition. The cathode 114 is configured to contact at least one of the first sidewall 212 and the second sidewall 214 of the overhang structure 110 at a first cathode endpoint 166, and to contact the third sidewall 216 and the fourth sidewall 218 at a second cathode endpoint 166. The first cathode endpoint 166 is positioned higher up the first sidewall 212 and the second sidewall 214 than the second cathode endpoint 166 is positioned on the third sidewall 216 and the fourth sidewall 218.

[0070] It is to be understood that, although as described herein, every overhang structure 110 is etched to form a respective overhang profile 182 in a single step, each overhang structure 110 may alternatively be etched sequentially. For example, all sub-pixels 106 designated to receive an OLE material 112 having a first color may have their respective overhang profile 182 etched in an initial etching step. The OLE material 112 having the first color may then be deposited within these sub-pixels 106 before proceeding. Subsequently, sub-pixels 106 designated to receive an OLE material 112 having a second color may be etched, followed by deposition of the OLE material 112 having the second color.

[0071] Embodiments disclosed herein provide pixel architectures and fabrication techniques for sub-pixel geometries exhibiting enhanced resolution and improved visual uniformity, while addressing electrical challenges associated with such geometries. Embodiments herein include sub-pixels having PDL profiles and overhang profiles that differ from each other. The PDL profile may be optimized for resolution, while the overhang profile may be optimized for enhanced cathode connection and reduced cross-talk.PATENTAttorney Docket No.: 44025804W001

[0072] While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

Claims

PATENTAttorney Docket No.: 44025804W001What is claimed is:

1. A device, comprising:a substrate;a pixel-defining layer (PDL) structure disposed over the substrate, the PDL structure defining an anode;an overhang structure disposed over the PDL structure;a first PDL region located between a first intersection point of the anode and the PDL structure and a first sidewall of the overhang structure;a second PDL region located between a second intersection point of the anode and the PDL structure and a second sidewall of the overhang structure, wherein the second PDL region opposes the first PDL region;a third PDL region located between a third intersection point of the anode and the PDL structure and a third sidewall of the overhang structure;a fourth PDL region located between a fourth intersection point of the anode and the PDL structure and a fourth sidewall of the overhang structure, wherein the fourth PDL region opposes the third PDL region; andat least one sub-pixel defined by the overhang structure, comprising:an organic light emitting (OLE) material; anda cathode, wherein the cathode contacts:at least one of the first sidewall and the second sidewall at a first cathode endpoint; andthe third sidewall and the fourth sidewall at a second cathode endpoint, wherein the cathode has a first thickness along at least one of the first sidewall and the second sidewall, and a second thickness along the third sidewall and the fourth sidewall, the first thickness being greater than the second thickness.

2. The device of claim 1 , wherein the first PDL region, the second PDL region, the third PDL region, and the fourth PDL region define a PDL profile.

3. The device of claim 2, wherein the PDL profile is substantially diamond shaped.PATENTAttorney Docket No.: 44025804W0014. The device of claim 2, wherein the first sidewall, the second sidewall, the third sidewall, and the fourth sidewall define an overhang profile.

5. The device of claim 4, wherein the PDL profile and the overhang profile have different geometries.

6. The device of claim 1 , wherein the first sidewall has a first length, the second sidewall has as second length, the third sidewall has a third length, and the fourth sidewall has a fourth length, and wherein the first length and the second length are greater than either of the third length and the fourth length.

7. The device of claim 1 , wherein at least a portion of the first sidewall and the second sidewall are oriented parallel to a nozzle direction of a deposition source.

8. The device of claim 1 , further comprising:a via hole disposed below the anode, the via hole configured to receive a conductive layer for electrically connecting the anode to a thin-film transistor (TFT) disposed below the substrate, the via hole positioned outside the first PDL region, the second PDL region, the third PDL region, or the fourth PDL region.

9. The device of claim 1 , wherein:the first thickness is measured at a first midpoint located between the first cathode endpoint and a first OLE material endpoint along at least one of the first sidewall and the second sidewall; andthe second thickness is measured at a second midpoint located between the second cathode endpoint and a second OLE material endpoint along the third sidewall or the fourth sidewall.

10. A device, comprising:a substrate;a pixel-defining layer (PDL) structure disposed over the substrate, the PDL structure defining an anode;PATENTAttorney Docket No.: 44025804W001an overhang structure disposed over the PDL structure, the overhang structure having an overhang profile;a first PDL region located between a first intersection point of the anode and the PDL structure and a first sidewall of the overhang structure;a second PDL region located between a second intersection point of the anode and the PDL structure and a second sidewall of the overhang structure, wherein the second PDL region opposes the first PDL region;a third PDL region located between a third intersection point of the anode and the PDL structure and a third sidewall of the overhang structure;a fourth PDL region located between a fourth intersection point of the anode and the PDL structure and a fourth sidewall of the overhang structure, wherein the fourth PDL region opposes the third PDL region,wherein the first PDL region, the second PDL region, the third PDL region, and the fourth PDL region define a PDL profile, the PDL profile having a different geometry than the overhang profile; andat least one sub-pixel defined by the overhang structure, comprising:an organic light emitting (OLE) material; anda cathode.

11. The device of claim 10, wherein the PDL profile is substantially diamond shaped.

12. The device of claim 10, wherein the first sidewall has a first length, the second sidewall has as second length, the third sidewall has a third length, and the fourth sidewall has a fourth length, and wherein the first length and the second length are greater than either of the third length and the fourth length.

13. The device of claim 10, wherein at least a portion of the first sidewall and the second sidewall are oriented parallel to a nozzle direction of a deposition source.

14. The device of claim 10, wherein the cathode contacts:at least one of the first sidewall and the second sidewall at a first cathode endpoint; andPATENTAttorney Docket No.: 44025804W001the third sidewall and the fourth sidewall at a second cathode endpoint, wherein the cathode has a first thickness along at least one of the first sidewall and the second sidewall, and a second thickness along the third sidewall and the fourth sidewall, the first thickness being greater than the second thickness,wherein the first thickness is measured at a first midpoint located between the first cathode endpoint and a first OLE material endpoint along at least one of the first sidewall and the second sidewall, and the second thickness is measured at a second midpoint located between the second cathode endpoint and a second OLE material endpoint along the third sidewall or the fourth sidewall.

15. The device of claim 10, further comprising:a via hole disposed below the anode, the via hole configured to receive a conductive layer for electrically connecting the anode to a thin-film transistor (TFT) disposed below the substrate, the via hole positioned inside the first PDL region, the second PDL region, the third PDL region, or the fourth PDL region.

16. A method of fabricating a device, comprising:disposing a first photoresist over a pixel defining layer (PDL) material; patterning the first photoresist to form a plurality of first openings, thereby exposing portions of an upper surface of the PDL material;etching the PDL material to form PDL structures having anodes exposed therebetween, the PDL structures having a PDL profiled defined by a first PDL region, a second PDL region, a third PDL region, and a fourth PDL region;disposing a lower portion layer over the PDL structures and the anodes, and disposing an upper portion layer over the lower portion layer;disposing a second photoresist over the upper portion layer;patterning the second photoresist to form a plurality of second openings, thereby exposing regions of the upper portion layer; andetching the upper portion layer and the lower portion layer through the second openings to form overhang structures, each overhang structure having an overhang profile, the overhang profile defined by a first sidewall, a second sidewall, a third sidewall, and a fourth sidewall, wherein the overhang profile and the PDL profile have different geometries.PATENTAttorney Docket No.: 44025804W00117. The method of claim 16, further comprising:depositing an organic light emitting (OLE) material between, at least, the first PDL region, the second PDL region, the third PDL region, and the fourth PDL region; anddepositing a cathode, wherein the cathode contacts:at least one of the first sidewall and the second sidewall at a first cathode endpoint; andthe third sidewall and the fourth sidewall at a second cathode endpoint, wherein the cathode has a first thickness along at least one of the first sidewall and the second sidewall, and a second thickness along the third sidewall and the fourth sidewall, the first thickness being greater than the second thickness.

18. The method of claim 17, wherein:the first thickness is measured at a first midpoint located between the first cathode endpoint and a first OLE material endpoint along at least one of the first sidewall and the second sidewall; andthe second thickness is measured at a second midpoint located between the second cathode endpoint and a second OLE material endpoint along the third sidewall or the fourth sidewall.

19. The method of claim 16, further comprising:etching a via hole below the anodes, the via hole configured to receive a conductive layer for electrically connecting the anodes to a thin-film transistor (TFT) disposed below the anodes, the via hole positioned outside the first PDL region, the second PDL region, the third PDL region, or the fourth PDL region.

20. The method of claim 16, wherein the PDL profile is substantially diamond shaped.

Images