Semiconductor device manufacturing: process – Chemical etching – Combined with the removal of material by nonchemical means
Reexamination Certificate
2001-11-13
2003-08-05
Tsai, Jey (Department: 2812)
Semiconductor device manufacturing: process
Chemical etching
Combined with the removal of material by nonchemical means
C438S030000, C438S940000, C438S463000
Reexamination Certificate
active
06602790
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to laser ablation of conductive films and, more specifically, to a method for laser patterning a multilayered conductor/plastic substrate structure and to multilayered electrode/plastic substrate structures and display devices incorporating the same.
2. General Background and State of the Art
A liquid crystal display (LCD) is a type of flat panel display used in various electronic devices. Generally, LCDs comprise two sheets of polarizing material with a liquid crystal solution therebetween. Each sheet of polarizing material typically comprises a substrate of glass or transparent plastic; the liquid crystal (LC) is used as optical switches. The substrates are usually manufactured with transparent electrodes, typically made of indium tin oxide (ITO), to which electrical “driving” signals are coupled. The driving signals induce an electric field which can cause a phase change or state change in the LC material; the LC exhibiting different light-reflecting characteristics according to its phase and/or state.
Liquid crystals may be nematic, smectic or cholesteric depending upon the arrangement of the molecules. A twisted nematic cell is made up of: two bounding plates (usually glass slides or plastic plates), each with a transparent conductive coating (such as ITO or another conductor) that acts as an electrode, spacers to control the cell gap, two crossed polarizers (the polarizer and the analyzer), and nematic liquid crystal material. Twisted nematic displays rotate the director of the liquid crystal by 90°. Super-twisted nematic displays employ up to a 270° rotation. This extra rotation gives the crystal a much steeper voltage-brightness response curve and also widens the angle at which the display can be viewed before losing much contrast. Cholesteric liquid crystal (CLC) displays are normally reflective (meaning no backlight is needed) and can function without the use of polarizing films or a color filter. “Cholesteric” means a type of liquid crystal having finer pitch than that of twisted nematic and super twisted nematic. Sometimes it is called “chiral nematic” because cholesteric liquid crystal is normally obtained by adding chiral agents to host nematic liquid crystals. Cholesteric liquid crystals may be used to provide bi-stable and multi-stable displays that, due to their non-volatile “memory” characteristic, do not require a continuous driving circuit to maintain a display image, thereby significantly reducing power consumption. Ferroelectric liquid crystals (FLCs) use liquid crystal substances that have chiral molecules in a smectic C type of arrangement because the spiral nature of these molecules allows the microsecond switching response time that make FLCs particularly suited to advanced displays. Surface-stabilized ferroelectric liquid crystals (SSFLCs) apply controlled pressure through the use of a glass plate, suppressing the spiral of the molecules to make the switching even more rapid.
Some known LCD devices include chemically-etched, transparent, conductive layers overlying a glass substrate. See, e.g., U.S. Pat. No. 5,667,853 to Fukuyoshi et al., incorporated herein by reference. Unfortunately, chemical etching processes are often difficult to control especially for plastic films. As a consequence, electrodes resulting from such processes are often misshaped, with “wells” being formed near the substrate in instances where too much etchant was employed. Moreover, the minimum line gaps obtained in plastic films are typically limited to 15 &mgr;m or more. Additionally, concerns for the environment lessen the desirability of employing chemical etching processes which produce dangerous and/or harmful byproducts.
There are alternative display technologies to LCD's that may be used for example in flat panel displays. A notable example is organic or polymer light emitting devices (OLEDs or PLEDs), which are comprised of several layers in which one of the layers is comprised of an organic material that can be made to electroluminesce by applying a voltage across the device. An OLED device is typically a laminate formed on a substrate such as glass. A light-emitting layer of a luminescent organic solid, as well as adjacent semiconductor layers, are sandwiched between an anode and a cathode. The semiconductor layers can be hole-injecting and electron-injecting layers. PLEDs can be considered a subspecies of OLEDs in which the luminescent organic material is a polymer. The light-emitting layers may be selected from any of a multitude of light emitting organic solids, e.g. polymers or suitably fluorescent or chemiluminescent organic compounds. Such compounds and polymers include metal ion salts of 8-hydroxyquinolate, trivalent metal quinolate complexes, trivalent metal bridged quinolate complexes, Schiff base divalent metal complexes, tin (IV) metal complexes, metal acetylacetonate complexes, metal bidentate ligand complexes incorporating organic ligands such as 2-picolylketones, 2-quinaldylketones, 2-(o-phenoxy) pyridine ketones, bisphosphonates, divalent metal maleonitriledithiolate complexes, molecular charge transfer complexes, rare earth mixed chelates, (5-hydroxy) quinoxaline metal complexes, aluminum tris-quinolates, and polymers such as poly(p-phenylenevinylene), poly(dialkoxyphenylenevinylene), poly(thiophene), poly(fluorene), poly(phenylene), poly(phenylacetylene), poly(aniline), poly(3-alkylthiophene), poly(3-octylthiophene), and poly(N-vinylcarbazole). When a potential difference is applied across the cathode and anode, electrodes from the electrode-injecting layer and holes from the hole-injecting layer are injected into the light-emitting layer. They recombine, emitting light. OLEDs and PLEDs are described in the following United States patents, all of which are incorporated herein by this reference: U.S. Pat. No. 5,707,745 to Forrest et al., U.S. Pat. No. 5,721,160 to Forrest et al., U.S. Pat. No. 5,757,026 to Forrest et al., U.S. Pat. No. 5,834,893 to Bulovic et al., U.S. Pat. No. 5,861,219 to Thompson et al., U.S. Pat. No. 5,904,916 to Tang et al., U.S. Pat. No. 5,986,401 to Thompson et al., U.S. Pat. No. 5,998,803 to Forrest et al., U.S. Pat. No. 6,013,538 to Burrows et al., U.S. Pat. No. 6,046,543 to Bulovic et al., U.S. Pat. No. 6,048,573 to Tang et al., U.S. Pat. No. 6,048,630 to Burrows et al., U.S. Pat. No. 6,066,357 to Tang et al., U.S. Pat. No. 6,125,226 to Forrest et al., U.S. Pat. No. 6,137,223 to Hung et al., U.S. Pat. No. 6,140,763 to Hung et al., U.S. Pat. No. 6,172,459 to Hung et al., U.S. Pat. No. 6,242,115 to Thompson et al., and U.S. Pat. No. 6,274,980 to Burrows et al.
In a typical matrix-addressed light-emitting display device, numerous light emitting devices are formed on a single substrate and arranged in groups in a regular grid pattern. Activation may be by rows and columns, or in an active matrix with individual cathode and anode pads. OLED's are often manufactured by first depositing a transparent electrode on the substrate, and patterning the same into electrode portions. The organic layer(s) is then deposited over the transparent electrodes. A metallic electrode can be formed over the electrode layers. For example, in U.S. Pat. No. 5,703,436 to Forrest et al., incorporated herein by reference, transparent indium tin oxide (ITO) is used as the hole-injecting electrode, and a Mg—Ag—ITO electrode layer is used for electron injection.
An excimer laser has been employed to pattern ITO electrode material overlying a glass or quartz substrate. See, e.g., U.S. Pat. No. 4,970,366 to Imatou et al. and European Patent Specification EP 0 699 375 B1 by Philips Electronics N.V., both incorporated herein by reference. However, electrode/substrate structures formed with glass or quartz substrates lack the flexibility and thickness desired for many display products.
F. E. Doany et al., “Large-field scanning laser ablation system”, IBM Journal of Research and Development, Vol. 41, No. 1/2, 1997, incorporated herein by reference, discloses a l
Heydarpour Ramin
Kian Kouroche
Avery Dennison Corporation
Oppenheimer Wolff & Donnelly LLP
Tsai Jey
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