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Methods and compositions for removing group viii metal-containing materials from surfacesRelated Patent Categories: Etching A Substrate: Processes, Nongaseous Phase Etching Of SubstrateMethods and compositions for removing group viii metal-containing materials from surfaces description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20060201913, Methods and compositions for removing group viii metal-containing materials from surfaces. Brief Patent Description - Full Patent Description - Patent Application Claims
FIELD OF THE INVENTION [0001] The present invention relates to methods for removing Group VIII metal-containing materials (preferably, platinum-containing, and more preferably, platinum-rhodium-containing materials) from surfaces, particularly in the fabrication of semiconductor devices. BACKGROUND OF THE INVENTION [0002] Films of metals and metal oxides, particularly the heavier elements of Group VIII, are becoming important for a variety of electronic and electrochemical applications. This is at least because many of the Group VIII metal films are generally unreactive, resistant to diffusion of oxygen and silicon, and are good conductors. Oxides of certain of these metals also possess these properties, although perhaps to a different extent. [0003] Thus, films of Group VIII metals and metal oxides, particularly the second and third row metals (e.g., Ru, Os, Rh, Ir, Pd, and Pt) have suitable properties for a variety of uses in integrated circuits. For example, they can be used in integrated circuits for electrical contacts. They are particularly suitable for use as barrier layers between the dielectric material and the silicon substrate in memory devices, such as ferroelectric memories. Furthermore, they may even be suitable as the plate (i.e., electrode) itself in capacitors. [0004] Platinum is one of the candidates for use as an electrode for high dielectric capacitors. Capacitors are the basic charge storage devices in random access memory devices, such as dynamic random access memory (DRAM) devices, static random access memory (SRAM) devices, and now ferroelectric memory (FE RAM) devices. They consist of two conductors, such as parallel metal or polysilicon plates, which act as the electrodes (i.e., the storage node electrode and the cell plate capacitor electrode), insulated from each other by a dielectric material (a ferroelectric dielectric material for FE RAMs). Thus, there is a continuing need for methods and materials for the deposition of Group VIII metal-containing films, preferably, platinum-containing films. [0005] Many surfaces that result during the formation of Group VIII metal-containing films, particularly in the wafer fabrication of semiconductor devices, do not have uniform height, and therefore, the wafer thickness is also non-uniform. Further, surfaces may have defects such as crystal lattice damage, scratches, roughness, or embedded particles of dirt or dust. For various fabrication processes to be performed, such as lithography and etching, height non-uniformities and defects at the surface of the wafer must be reduced or eliminated. Various planarization techniques are available to provide such reduction and/or elimination. One such planarization technique includes mechanical and/or chemical-mechanical polishing (abbreviated herein as "CMP"). [0006] The process of planarization is used to remove material, and preferably achieve a planar surface, over the entire chip and wafer, sometimes referred to as "global planarity." Conventionally, the process of planarization, and particularly CMP, involves the use of a wafer holder that holds a wafer, a polishing pad, and an abrasive slurry that includes a dispersion of a plurality of abrasive particles in a liquid. The abrasive slurry is applied so that it contacts the interface of the wafer and the polishing pad. A table or platen has a polishing pad thereon. The polishing pad is applied to the wafer at a certain pressure to perform the planarization. At least one of the wafer and a polishing pad are set in motion relative to the other. In some planarization processes, the wafer holder may or may not rotate, the table or platen may or may not rotate and/or the platen may be moved in a linear motion as opposed to rotating. There are numerous types of planarization units available which perform the process in different manners. Alternatively, the polishing pad and abrasive slurry may be replaced by a fixed abrasive article that includes a plurality of abrasive particles dispersed within a binder adhered to at least one surface of a backing material. [0007] The planarization of a surface that includes platinum and other Group VIII metals typically involves mechanical polishing, as opposed to chemical-mechanical polishing, because they are relatively chemically inert and/or have relatively few volatile products. Such mechanical polishing uses alumina and silica particles. Unfortunately, mechanical polishing tends to cause smearing (i.e., undesirable relocation of target material, particularly ductile materials) and the formation of defects (e.g., scratches), both of which can be detected optically, rather than the clean removal of the platinum. Also, many commercially available abrasive slurries do not effectively planarize platinum or other Group VIII metal-containing surfaces either because no material is removed (which results in no change in resistance of the wafer) or the resultant surface has defects therein. [0008] Another process for removing material is etching. Etching is the selective removal of material, either locally by masking an area or over an entire surface without masking, the latter of which is referred to as blanket etching. Typically, wet etching is performed by immersing the substrate in an appropriate solution or by spraying the surface with the etchant solution. Etchants used for platinum include aqua regia (a mixture of nitric acid and hydrochloric acid); however, this does not generally etch alloys of platinum, particularly platinum-rhodium. Compositions that do etch alloys such as platinum-rhodium include compounds that are not compatible with other fabrication processes and/or are difficult to apply. These include KMnO.sub.4 and zinc powder, for example. [0009] Thus, there is still a need for methods for planarizing or etching an exposed surface of a substrate that includes Group VIII metals, particularly in the fabrication of semiconductor devices. SUMMARY OF THE INVENTION [0010] The present invention provides methods that overcome many of the problems associated with the removal of a material from a surface that includes one or more Group VIII metals, preferably platinum and optionally another of the Group VIII metals. Such a surface is referred to herein as a Group VIII metal-containing surface. Preferably, a "Group VIII metal-containing surface" refers to an exposed region having a Group VIII metal (preferably platinum) present in an amount of at least about 50 atomic percent of the composition of the region. More preferably, the surface includes (and most preferably, consists essentially of) platinum in elemental form or an alloy with one or more other Group VIII metals. That is, the surface does not include significant amounts of non-Group VIII metals or nonmetals such as silicon, oxygen, or nitrogen atoms. Most preferably, the surface includes a platinum/rhodium alloy present in an amount of at least about 60 atomic percent platinum and no more than about 40 atomic percent rhodium. [0011] The material may be provided as a layer, film, coating, etc. Preferably, it is removed via planarization (e.g., via chemical-mechanical or mechanical planarization or polishing) or etching, in accordance with the present invention. [0012] The methods of the present invention involve removing the Group VIII metal-containing material using an acidic composition that includes a mixture of phosphoric acid, sulfuric acid, nitric acid, and hydrochloric acid. This mixture can be used in wet etching or planarization processes. The workpiece can be immersed in the acidic composition or the acidic composition can be sprayed on the workpiece. [0013] Preferably, the acidic composition, which can be in the form of an etchant solution or acidic composition, includes a mixture of phosphoric acid, sulfuric acid, nitric acid, and hydrochloric acid. Typically, an amount of each is used in excess of the target material to be removed. [0014] In preferred embodiments, the acidic composition includes phosphoric acid initially in an amount of at least about 10 vol-% and no greater than about 25 vol-%, sulfuric acid initially in an amount of at least about 10 vol-% and no greater than about 50 vol-%, nitric acid initially in an amount of at least about 0.25 vol-% and no greater than about 10 vol-%, and hydrochloric acid initially in an amount of at least about 25 vol-% and no greater than about 50 vol-%. More preferably, the nitric acid is initially present in an amount of at least about 0.25 vol-% and no greater than about 1 vol-%. [0015] The acidic composition can optionally include abrasive particles, thereby resulting in an abrasive slurry, and be used in planarization techniques with conventional polishing pads that do not have abrasive particles embedded therein. Alternatively, the acidic composition without abrasive particles therein can be used with fixed abrasive articles (i.e., abrasive polishing pads) in place of conventional polishing pads. Such fixed abrasive articles include a plurality of abrasive particles dispersed within a binder adhered to at least one surface of a backing material. Whether in a fixed abrasive or in the acidic composition, preferred abrasive particles have a hardness of no greater than about 9 mho. If the acidic composition is not stable in combination with abrasive particles (i.e., an abrasive slurry), they may be provided by separate delivery systems and/or in separate compositions and mixed at the point of use. [0016] Thus, in one aspect of the present invention, a method is provided wherein contacting the Group VIII metal-containing material with an acidic composition involves: positioning the Group VIII metal-containing surface of the substrate to interface with a polishing pad; supplying an acidic composition in proximity to the interface; and planarizing the substrate surface. The acidic composition can include a plurality of abrasive particles and/or the polishing pad can include a plurality of abrasive particles. [0017] As used herein, "semiconductor substrate or substrate assembly" refers to a semiconductor substrate such as a base semiconductor layer or a semiconductor substrate having one or more layers, structures, or regions formed thereon. A base semiconductor layer is typically the lowest layer of silicon material on a wafer or a silicon layer deposited on another material, such as silicon on sapphire. When reference is made to a substrate assembly, various process steps may have been previously used to form or define regions, junctions, various structures or features, and openings such as vias, contact openings, high aspect ratio openings, conductive regions, contact regions, etc. For example, a substrate assembly may refer to a structure upon which a metallization is to be performed, e.g., metal lines are formed for electrical interconnection functionality. [0018] Herein, as is conventionally understood, "wet etching" or simply "etching" refers to the removal of material from a surface, whether it be a large or small amount of material, using chemical dissolution. Typically, wet etching is performed by immersing the substrate in an appropriate solution or by spraying the surface with the etchant solution. [0019] Herein, as is conventionally understood, "planarizing" or "planarization" refers to the removal of material from a surface, whether it be a large or small amount of material, either mechanically, chemically, or both. This also includes removing material by polishing. As used herein, "chemical-mechanical polishing" and "CMP" refer to a dual mechanism having both a chemical component and a mechanical component, wherein corrosion chemistry and fracture mechanics both play a roll in the removal of material, as in wafer polishing. BRIEF DESCRIPTION OF THE FIGURES [0020] FIGS. 1A and 1B are cross-sectional illustrations of one portion of a wafer before and after an etching or planarization process has been performed in accordance with the present invention. Continue reading about Methods and compositions for removing group viii metal-containing materials from surfaces... 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