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  Hollow cathode sputtering apparatus and related methodUSPTO Application #: 20070256926Title: Hollow cathode sputtering apparatus and related method Abstract: The present invention provides an improved hollow cathode method for sputter coating a substrate. The method of the invention comprises providing a channel for gas to flow through, the channel defined by a channel defining surface wherein one or more portions of the channel-defining surface include at least one target material. Gas is flowed through the channel wherein at least a portion of the gas is a non-laminarly flowing gas. While the gas is flowing through the channel a plasma is generated causing target material to be sputtered off the channel-defining surface to form a gaseous mixture containing target atoms that is transported to the substrate. In an important application of the present invention, a method for forming oxide films and in particular zinc oxide films is provided. (end of abstract) Agent: Brooks Kushman P.C. - Southfield, MI, US Inventors: Alan E. Delahoy, Sheyu Guo USPTO Applicaton #: 20070256926 - Class: 204192100 (USPTO) Related Patent Categories: Chemistry: Electrical And Wave Energy, Non-distilling Bottoms Treatment, Coating, Forming Or Etching By Sputtering The Patent Description & Claims data below is from USPTO Patent Application 20070256926. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application is a continuation of pending U.S. application Ser. No. 10/635,344 filed Aug. 6, 2003. This application is hereby incorporated by reference. BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The present invention is related to methods and related apparatus for depositing films on a substrate by hollow cathode sputtering. More particularly, the present invention relates to methods and apparatus for depositing oxide and other films by hollow cathode sputtering. [0004] 2. Background Art [0005] Numerous methods are known for depositing thin films on a substrate. Such methods include, for example, sputtering, vacuum evaporation, chemical vapor deposition, and the like. Typical substrates that are coated with thin films are glass, ceramics, and silicon wafers. Vacuum evaporation is a low pressure deposition technique in which a material is vaporized by heating. Vacuum evaporation is a line of sight deposition technique in which the vaporized material is then radiated out in straight lines from the source. Chemical vapor deposition is a thin film deposition technique in which a reactive gaseous mixture is heated over a substrate. The elevated temperature causes a chemical reaction to occur from which a desired film is formed. Chemical vapor deposition can be undesirable because of contamination of the deposited films. [0006] Sputtering is a low pressure deposition process in which a plasma containing gas ions and electrons is created by the action of an electric field on gas that is introduced into a deposition chamber. The electric field may be formed by either a dc or rf voltage bias. These ions are accelerated towards a target from which material is removed. This removed material is ultimately deposited on a nearby substrate. Reactive sputtering is a further refinement of the sputtering process in which a reactive gas such as nitrogen, oxygen, hydrogen, H.sub.2O, H.sub.2Se, CH.sub.4, C.sub.2H.sub.6, C.sub.2H.sub.2, C.sub.2H.sub.4, B.sub.2H.sub.6, PH.sub.3, CCl.sub.4, CF.sub.4, organic monomers like HMDSO, pyrrole and the like are introduced into the deposition chamber. These reactive gases are capable of reacting with the removed target material to form a compound film on the substrate. Accordingly, these reactive gases provide one or more atoms that are incorporated into the film. Reactive sputtering is particularly useful for depositing doped and undoped metal oxides, nitrides, carbides, and the like. However, care must be taken in the reactive sputtering process because such reactive gases may form an insulating layer on the conductive target thereby reducing film growth rate. [0007] The effect of insulating layers on the targets in the sputtering process is generally alleviated by the use of RF power to form the plasma. This type of sputtering is referred to as RF sputtering. It is particularly useful for depositing both insulating and oxide films, but deposition rates tend to be low. In the RF sputtering process, a substrate is placed between two electrodes which are driven by an RF power source. Superimposed on this applied RF field is a DC potential. This DC potential advantageously drives the ions toward the target causing some of the target material to be removed. This removed target material may then react with a reactive gas. Again the removed material ultimately coats the substrate. [0008] A number of sputtering refinements makes this technique even more desirable for the deposition of insulating and oxide films. These refinements include unbalanced magnetron sputtering, the utilization of pulsed dc power, and the use of hollow cathodes. The utilization of hollow cathode sputtering in a gas flow mode is a relatively new technique in which an inert gas such as argon is introduced into a channel in a target cathode. While contained within this channel a plasma is formed that removes atoms from the target. These atoms are eventually swept by the gas flow out of the cathode at which point they may then be reacted with a reactive gas. The continuous flow of the inert gas prevents (or tends to prevent) the reactive gas from entering the cathode and thereby prevents (or tends to prevent) an insulating layer from forming on the target. Although the prior art hollow cathode processes may inhibit the formation of an insulating layer on the target, these processes tend to produce films at unacceptably low growth rates. [0009] Accordingly, there exists a need for improved sputtering methods for depositing thin films and in particular insulating or oxide thin films with high growth rates and reduced formation of insulating layers on the targets used in such sputtering processes. SUMMARY OF THE INVENTION [0010] The present invention overcomes the problems of the prior art by providing in one embodiment an improved method for sputter coating a substrate. The method of the invention is a hollow cathode sputtering process which comprises providing a channel for gas to flow through, the channel defined by a channel defining surface wherein one or more portions of the channel-defining surface includes at least one target material. Gas is flowed through the channel wherein at least a portion of the gas is a non-laminarly flowing gas. While the gas is flowing through the channel a plasma is generated causing target material to be sputtered off the channel-defining surface to form a gaseous mixture containing target atoms that are transported to the substrate. In an important application of the present invention, a method for forming oxide films and in particular zinc oxide films is provided. [0011] In another embodiment of the present invention, a sputter-coating system for coating a substrate is provided. Such a sputter-coating system will include at least one target material, an electrode having a channel-defining surface, and a source of non-laminarly flowing working gas. The channel-defining surface contains the target material. During operation of the sputter-coating system, a plasma is generated causing the at least one target material to be sputtered off the channel-defining surface. This in turn causes a gaseous reactive composition to form which is subsequently transported to the substrate. [0012] The source of non-laminarly flowing gas includes a series of orifices such that at least two gas streams emerging from the series of orifices are substantially flowing in non-parallel directions. The source of non-laminarly flowing gas includes a series of adjacent orifices that direct the gas in non-parallel directions. The channel defining surface will typically be part of the cathode. Moreover, the channel is characterized by a generally rectangular cross section. The sputter-coating system may have a first target material and a second target material. The first target material is preferably opposite the second where the first target material and the second target material are the same or different. In such a configuration, the two target materials will form at least a portion of the side walls of the channel-defining surface, and in particular the side walls that make up the wider sides when the channel has a rectangular cross section. Moreover, the at least one target material optionally includes a third target material and a fourth target material. The third target material being opposite the fourth target material. In this instance, the first target material, the second target material, the third target material, and the fourth target material may be the same or different. The target material, which is typically part of the cathode, is in electrical contact with a DC potential or a DC potential with a superimposed AC potential. Moreover, the at least one target material comprises a metal or metal alloy. Suitable target materials include, but are not limited to, zinc, copper, aluminum, silicon, tin, indium, magnesium, titanium, chromium, molybdenum, nickel, yttrium, zirconium, niobium, cadmium, and mixtures thereof. The sputter-coating system of the present invention further comprises a source of a reactive gas which is located at proximate position to the exit of the channel. BRIEF DESCRIPTION OF THE DRAWINGS [0013] FIG. 1A is a schematic demonstrating laminar gas flow in a hollow cathode with a baffle between the gas nozzle and the channel defined by the target materials; [0014] FIG. 1B is a schematic demonstrating laminar gas flow in a hollow cathode with the gas nozzle between the baffle and the channel defined by the target materials; [0015] FIG. 1C is a schematic demonstrating the utilization of non-laminar gas flow in a hollow cathode by creating a narrow passage between the gas nozzle and the target materials; [0016] FIG. 1D is a schematic demonstrating the utilization of non-laminar gas flow in a hollow cathode by directing the gas flow into non-parallel directions; [0017] FIG. 2 is a perspective view of a gas nozzle which introduces a gas with non-parallel directions into the channel. [0018] FIG. 3 is a plot of a waveform that may be used to drive a sputtering system with an asymmetric bipolar pulsed DC power supply. [0019] FIG. 4A is a perspective view of a target that is capable of holding up two target materials separated by two insulating blocks; [0020] FIG. 4B is a front view of a target that is capable of holding up two target materials separated by two insulating blocks; Continue reading... Full patent description for Hollow cathode sputtering apparatus and related method Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Hollow cathode sputtering apparatus and related method 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. 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