Patent Publication Number: US-2011073563-A1

Title: Patterning Method for Carbon-Based Substrate

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates in general to a patterning method for a substrate, and more particularly to a patterning method for a carbon-based substrate. 
     2. Description of the Related Art 
     The carbon-based substrate, having the features of high conductive, high strength and high bendability, has attracted great attention in recent years. The multi-touch effect can be achieved if a circuit pattern like a transistor array is marked on the carbon-based substrate so as to form a transparent carbon nanostructure-based thin film. The transparent carbon nanostructure-based thin film, having achieved the standards of 85% transmittance and 200 Ω/sq impedance, can be used in the touch panel of various electronic products. 
     The traditional IC processes use a photo resistor in a lithography step and a wet etching step to form the circuit pattern. However, the strong anti-corrosion of the carbon-based substrate makes the manufacturing process thereof complicated and time-consuming. Thus, the manufacturing cost of the carbon-based substrate is hard to be reduced and the carbon-based substrate cannot be widely used in various electronic products. 
     SUMMARY OF THE INVENTION 
     The invention is directed to a patterning method for a carbon-based substrate. The carbon-based substrate is etched by an oxygen-contained plasma at an atmospheric pressure, so that the process of patterning the carbon-based substrate is more efficient and more convenient. 
     According to a first aspect of the present invention, a patterning method for a carbon-based substrate is provided. The patterning method for the carbon-based substrate includes the following steps. The carbon-based substrate is provided. Under an open air environment, an atmospheric pressure plasma is produced from a plasma gas that includes mostly usually gas like oxygen, nitrogen, argon, clean dry air or mixed gas of them. The carbon-based substrate is etched by the atmospheric pressure plasma. 
     The invention will become apparent from the following detailed description of the preferred but non-limiting embodiments. The following description is made with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a flowchart of a patterning method for a carbon-based substrate; and 
         FIGS. 2-7  respectively show the steps of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The invention is exemplified by an embodiment below. However, the embodiment is for exemplification only, not for limiting the scope of protection of the invention. Besides, secondary elements are omitted in the embodiment for highlighting the technical features of the invention. 
     Referring to  FIG. 1  and  FIGS. 2-7 .  FIG. 1  shows a flowchart of a patterning method for a carbon-based substrate  100 .  FIGS. 2-7  show the respective steps of  FIG. 1 . 
     Firstly, the method begins at step S 102 , as indicated in  FIG. 2 , a carbon-based substrate  100  is provided. In the present embodiment of the invention, the carbon-based substrate  100  is exemplified by a transparent carbon nanostructure-based thin film like carbon nanotube or nano-graphite. The optical properties of the transparent carbon nanostructure-based thin film are similar to that of the indium tin oxide film (ITO film). The transparent carbon nanostructure-based thin film having high electron conductivity can be used to form a conductive film with high transparency. Therefore, the transparent carbon nanostructure-based thin film can be used in electronic devices such as displays and solar batteries, which require a transparent electrode, or used in photo-electrical elements such as transistors and sensors. 
     Next, the method proceeds to step S 104 , as indicated in  FIG. 3 , a hard mask  300  is provided. The hard mask  300  has a hollowed pattern  310 . The hard mask  300  is made from metal, ceramic or glass. The hollowed pattern  310  is a predetermined etching pattern of the carbon-based substrate  100 , wherein, the hollowed pattern  310  penetrates an upper surface  300   a  and a lower surface  300   b  of the hard mask  300 , and an inner-sidewall  310   a  of the hollowed pattern  310  is a steep sidewall so that the atmospheric pressure plasma  500  (illustrated in  FIG. 5 ) of the subsequent step can conveniently penetrate through. 
     In step S 104 , the inner-sidewall  310   a  of the hollowed pattern  310  is a steep sidewall; therefore, the hollowed pattern  310  of the hard mask  300  can be formed by ways of mechanical or chemical process, such as mechanical cutting, laser cutting, knife cutting, electric discharge machining or photo-etching. 
     Then, the method proceeds to step S 106 , as indicated in  FIG. 4 , the hard mask  300  is attached to the carbon-based substrate  100 , wherein the hollowed pattern  310  exposes a portion of the carbon-based substrate  100 . Whether the hard mask  300  contacts the carbon-based substrate  100  depends on the accuracy of the subsequent etching process. When the hard mask  300  contacts the carbon-based substrate  100 , the hard mask  300  can be fixed by a detachable adhesive (or a tape) or by a mechanical fixing element. 
     As disclosed in steps S 104  and S 106 , the material of the hard mask  300  is not the patterned photoresist or the patterned silicon nitride adopted in the semiconductor process. Moreover, the hard mask  300  already forms the hollowed pattern  310  before, not after, being attached to the carbon-based substrate  100 . 
     Thus, after the etching process of the hollowed pattern  310  of the hard mask  300  is completed, the same hard mask  300  can be repeated used in several carbon-based substrates  100 . 
     Afterwards, the method proceeds to step S 108 , as indicated in  FIG. 5 , an atmospheric pressure plasma  500  is produced from a plasma gas under an open air environment such as an atmospheric pressure or close to an atmospheric pressure. 
     The atmospheric pressure plasma  500  has cost advantage. In terms of equipment cost, the atmospheric pressure plasma  500  can do without the use of expensive and clumsy vacuum equipment. During the manufacturing process, the to-be-processed object is not subjected to the vacuum cavity, and is thus applicable to continual process. These features all contribute to reducing the manufacturing cost. 
     In terms of the components of the plasma gas for producing the atmospheric pressure plasma  500 , the plasma gas at least includes oxygen, such as pure oxygen, mixed gas of nitrogen and oxygen, mixed gas of argon and oxygen and clean dry air (CDA). 
     In terms of the device for producing the atmospheric pressure plasma  500 , the atmospheric pressure plasma  500  is produced from an arc jet plasma generator or a nonthermal dielectric barrier discharges (DBD) plasma generator for example. 
     In terms of the form of the atmospheric pressure plasma  500 , the atmospheric pressure plasma  500  is a dotted atmospheric pressure plasma or a linear atmospheric pressure plasma for example. 
     Then, the method proceeds to step S 110 , as indicated in  FIG. 6 , the carbon-based substrate is etched by the atmospheric pressure plasma  500 . The etching process uses the hard mask  300  as a shield, and only the portion of the carbon-based substrate  100  exposed on the hollowed pattern  310  is etched. 
     As disclosed above, the atmospheric pressure plasma  500  of the present embodiment of the invention is dotted or linear atmospheric pressure plasma. Thus, during the etching process, the carbon-based substrate  100  is etched by the atmospheric pressure plasma  500  through scanning. 
     As the atmospheric pressure plasma  500  of the present embodiment of the invention is produced from oxygen-based plasma gas, the atmospheric pressure plasma  500  contains oxygen plasma ions. When the oxygen plasma ions contact the carbon-based substrate  100 , a chemical reaction is generated by oxygen ions and the carbon-based substrate  100  to form a vaporizable air (such as carbon dioxide). The carbon-based substrate  100  is etched by the chemical reaction. Thus, in the present embodiment of the invention, the etching between the atmospheric pressure plasma  500  and the carbon-based substrate  100  is mainly done through a dry chemical reaction rather than through a wet chemical reaction or an ion bombardment. Therefore, the etching method of the present embodiment of the invention has very high etching selectivity and very high etching rate as well. 
     Then, the method proceeds to step S 112 , as indicated in  FIG. 7 , the hard mask  300  is removed form the carbon-based substrate  100 . As the hard mask  300  is not removed by destructive methods, and the atmospheric pressure plasma  500  will not destroy the hard mask  300  either, the hard mask  300  can be repeatedly used in several steps of etching the carbon-based substrate  100 . 
     While the invention has been described by way of example and in terms of a preferred embodiment, it is to be understood that the invention is not limited thereto. On the contrary, it is intended to cover various modifications and similar arrangements and procedures, and the scope of the appended claims therefore should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements and procedures.