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Patterning of electrodes in oled devicesRelated Patent Categories: Semiconductor Device Manufacturing: Process, Making Device Or Circuit Responsive To Nonelectrical Signal, Responsive To Electromagnetic Radiation, Having Organic Semiconductor ComponentPatterning of electrodes in oled devices description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20070190682, Patterning of electrodes in oled devices. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS-REFERENCE TO RELATED APPLICATION [0001] This application is a divisional application of and claims benefit of priority to U.S. application Ser. No. 10/166,829, filed Jun. 10, 2002, which is incorporated herein by reference in its entirety. FIELD OF THE INVENTION [0002] The present invention relates to an improved patterning of electrodes, such as those in organic light emitting diode (OLED) devices. BACKGROUND OF THE INVENTION [0003] FIG. 1 shows a pixelated OLED device 100 which serves, for example, as a display in various types of consumer electronic products, including cellular phones, cellular smart phones, personal organizers, pagers, advertising panels, touch screen displays, teleconferencing and multimedia products, virtual reality products, and display kiosks. [0004] The OLED device comprises a functional stack formed on a substrate 102. The functional stack comprises of one or more organic functional layers 104 between two conductive functional layers (106 and 108) which serve as electrodes (anode and cathode). The conductive layers are patterned as desired. For example, the conductive layers can be patterned to form rows of anodes in a first direction and columns of cathodes in a second direction. OLED cells or pixels are located where the cathodes and anodes overlap. Charge carriers are injected through the cathodes and anodes via bond pads 112 for recombination in the organic layers. The recombination of the charge carriers causes the organic layer of the pixels to emit visible radiation. The device is encapsulated with a cap 110, hermetically sealing the cells. [0005] As shown in FIG. 1, t-shaped pillars 114 are used to facilitate patterning of the upper conductive layer. The pillars can also be tapered with the top being wider than the bottom. Tapered or t-shaped pillars are described in, for example, Ext. Abstr. 44.sup.thSpring Meeting Japan Society of applied Physics and related Societies, 1997, and U.S. Pat. Nos. 5,962,970, 5,952,037, 5,742,129, or 5,701,055, which are all herein incorporated by reference for all purposes. The pillars are formed on the substrate after the formation of the lower conductive layer 106. Thereafter, the organic layer and conductive layer are deposited. Due to the profile of the pillars, the continuity of the upper conductive layer is disrupted, leaving segments of the conductive layer 108a over the organic layer 104 and segments 108b on top of the pillars. However, the functional stack is susceptible to damage resulting from exposure to atmospheric constituents like oxygen and moisture that penetrated into the interior of the device. The cathode layer comprises, for example, magnesium (Mg), calcium (Ca), barium (Ba), silver (Ag), aluminium (Al) or a mixture or alloy thereof, which are susceptible to damage caused by exposure to any potentially deleterious substance such as water vapor and oxygen. [0006] Referring to FIG. 1, the edges of the functional stack layers are exposed due to the profile of the pillars 114. Open edges such as 120 of the upper conductive layer and organic layer are especially susceptible to damage caused by water and oxygen and are typically areas which are affected first. The result may be shrinking pixels or dark, non-emitting spots due to the lack of current flow, leading to a reduction in the useful life of the OLED device. Known methods typically employed to protect the functional stack include hermetically sealing the device and providing a desiccant inside the device to absorb oxygen and moisture that permeates through the sealant. However, residual oxygen and moisture still remaining within the encapsulated device will cause the shrinkage of pixels over time, due to the reaction with oxygen and water, typically starting at the exposed edges of the functional layers. [0007] Alternatively, the upper conductive layer comprises an electron-emitting cathode layer and a protective conductive layer. The electron-emitting layer comprises, for example, Ca, Mg and/or Ba, or a mixture or alloy thereof, which is highly reactive to air and water. The protective layer comprises, for example, more stable materials such as silver (Ag,) platinum (Pt), chromium (Cr), gold (Au) and/or aluminum (Al) or a mixture or alloy thereof. The protective conductive layer covers a surface of the electron-emitting layer to protect it from exposure, but does not cover the edges of the cathode layer due to the profile of the pillars. Hence, the edges of the cathode layer are still exposed to residual oxygen and water. As evidenced from the foregoing discussion, it is desirable to provide a method to effectively pattern electrodes in the fabrication of OLED devices and protect the edges of the functional stack from damage caused by exposure to potentially deleterious substances. SUMMARY OF THE INVENTION [0008] The invention relates generally to the fabrication of devices such as OLED devices. In one embodiment of the invention, pillars are provided to pattern a conductive layer. The profile of the pillar serves to cover the edges of organic and conductive layers. In one embodiment, a pillar comprises a cap formed on a base, the base having a width at the top or upper portion that is narrower than a width at the bottom or lower portion. BRIEF DESCRIPTION OF THE DRAWINGS [0009] FIG. 1 shows a conventional OLED device employing t-shaped pillars; [0010] FIG. 2 shows one embodiment of the invention; and [0011] FIGS. 3-7 show a process for fabricating an OLED device in accordance with one embodiment of the invention. [0012] FIG. 8 shows one embodiment of the invention. PREFERRED EMBODIMENTS OF THE INVENTION [0013] FIG. 2 shows an OLED device 200 in accordance with one embodiment of the invention. The device comprises a substrate 202 on which OLED cells are formed. In one embodiment, the substrate comprises a transparent substrate, such as glass for viewing the cells through the substrate. Other types of transparent materials that can serve as a substrate to support the OLED pixels are also useful. Non-transparent substrates can also be used with, for example, applications in which the cells are visible through a cap 210. [0014] The OLED cells comprise a functional stack formed by one or more organic functional layers 204 formed between first and second conductive functional layers 206 and 208, the first and second functional conductive layers serving as first and second electrodes. In one embodiment, the first electrodes 206 are anodes and the second electrodes 208a are cathodes. Forming the first electrodes that are cathodes and second electrodes that are anodes is also useful. The first and second electrodes, for example, are formed as strips in respective first and second directions to create an array of OLED cells. Typically, the first and second directions are orthogonal to each other. Bond pads 212 are electrically coupled to the cathodes and anodes. The cap 210 is provided to encapsulate the OLED cells. [0015] Pillars 214 which extend above the OLED cells are provided on the substrate surface to facilitate the patterning of the second conductive layer. The pillars can also extend the height of the cavity to support the cap (as shown in FIG. 8). This is particularly useful for flexible OLED devices since the cap is prevented from contacting and damaging the cells. The pillars are used to pattern the conductive layer as desired to create separate OLED cells. For example, the pillars create rows of second electrodes 208a to form an array of OLED cells. Pillars which create other patterns for the second electrodes are also useful. OLED cells are located between the pillars where the second electrodes overlap the first electrodes. The gap between the pillars defines the pixel size, which is for example, about 20-500 .mu.m. [0016] In accordance with the invention, the profile of the pillar is selected to have the edges 220 of the functional layer or layers (204 or 208) covered. By covering the edges of the functional layers, the edges are protected from exposure to potentially deleterious substances like water and oxygen, which can adversely impact the reliability and lifetime of the OLED device. The height of the pillar is, for example, about 1-10 .mu.m, and preferably about 2-5 .mu.m. The width of the pillar should preferably be as small as possible to provide a large emissive area. [0017] In one embodiment, a pillar comprises a pillar cap 214a formed on a pillar base 214b. The pillar cap overhangs the base of the pillar. The width of the pillar cap should be sufficient to disrupt the continuity of the second conductive layer 208 during deposition. In one embodiment, the width of the pillar cap is about 10-100 .mu.m. The profile of the pillar base is selected to have the edges of the functional layer or layers (204 or 208) covered by the base sidewalls. Preferably, the profile of the base is selected to maximize the surface area of the organic and conductive functional layers while protecting their edges. The pillar base comprises an upper and lower portion. A width at the top or upper portion of the pillar base is narrower than a width at the bottom or lower portion. The width of the upper portion of the pillar base should be sufficient to ensure mechanical stability, and the width of the lower portion of the pillar base should be wide enough to provide the desired protection. The width of the upper portion is, for example, about 5-50 .mu.m, and the width of the lower portion is, for example, about 10-100 .mu.m wider than the upper width. In a preferred embodiment, the pillar base comprises a tapered or inverted v-shaped profile formed from, for example, a single device layer. In one embodiment, the sidewalls of the pillar base are about 45-65 (from the vertical). Other angles can also be useful. The sidewalls may be flat, convex or concave. [0018] Preferably, the pillars comprise a material which is stable during the fabrication process. In one embodiment, the pillars are formed by patterning a photosensitive material such as resist. Other methods of forming the pillars, such as etching, are also useful. The resist, when necessary, is treated to render it inert to solvents 15 used to deposit the functional organic layers. Other types of photosensitive materials, such as photosensitive polyamide or photosensitive polybenzoxazole, are also useful. In addition, electron cure resist systems, such as those manufactured by Allied Signal, can also be used to form pillars having the desired cross-sectional shape. Non-photosensitive insulating materials such as resins can also be used to form the pillars. Continue reading about Patterning of electrodes in oled devices... Full patent description for Patterning of electrodes in oled devices Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Patterning of electrodes in oled devices patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. Start now! - Receive info on patent apps like Patterning of electrodes in oled devices or other areas of interest. ### Previous Patent Application: Silicon-on-insulator near infrared active pixel sensor array Next Patent Application: Precursors for deposition of metal oxide layers or films Industry Class: Semiconductor device manufacturing: process ### FreshPatents.com Support Thank you for viewing the Patterning of electrodes in oled devices patent info. 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