Abstract:
A microwave-excited plasma device is proposed. The device comprises of a plurality of microwave plasma reaction units which are capable of generating plasma independently such that a large-area plasma is able to be generated by all of the units. Besides, the high cost of the large-area microwave coupling window and its deformation together with possible breakage caused by atmospheric pressure can be prevented. Moreover, when a plurality of permanent magnets is assembled upon each of the plasma reaction units, the microwave-excited plasma device is improved to be a large-area electron cyclotron resonance (ECR) plasma device.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the priority benefit of Taiwan application Ser. No. 100101138, filed Jan. 12, 2011. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification. 
     BACKGROUND 
     1. Field 
     The disclosure relates to a microwave-excited plasma device having capable of implementing large area plasma fabrication. 
     2. Description of Related Art 
     Microwave-excited plasmas are some kinds of plasma excited by microwave power and making neutral gases to be ionized, which have been applied to many fields of plasma processing manufactures such as semiconductor fabrications, solar-cell antireflection coating and carbon nanostructures synthesis. 
     Escalating the area of the microwave-excited plasmas is an important way to satisfy the aforesaid manufactures which are in demand of large-area plasma processes. Therefore, the areas of the microwave-excited plasma devices have to be extended in two dimensions. Thus, the concept of multiple microwave sources has been researched, such as U.S. Pat. No. 6,177,148B1. However, said patent merely accomplishes a one-dimensional microwave-excited plasma device. 
     In addition, Taiwan Patent Certification No. 215250 also proposed the concept of multiple microwave sources to actualize the large-area microwave-excited plasma device. However, the area of the microwave coupling window increases as the area of the plasma device escalates. Nevertheless, the microwave coupling window is generally fabricated with large-area flat quartz glass or ceramic. When the area of the microwave coupling window escalates, an atmospheric pressure tolerance thereof is challenged. Thus the large-area microwave coupling window usually deforms or breaks, thereby creating difficulties for escalating the area of the plasma device. 
     SUMMARY 
     A microwave-excited plasma device capable of escalating the area of the plasma is introduced herein. The microwave-excited plasma device includes a plasma reaction chamber, a metal sash, a plurality of panes, a plurality of microwave transmitters, and a plurality of waveguides (including impedance matching devices). The metal sash is assembled on the top of the plasma reaction chamber and has a plurality of small-area microwave coupling window openings. The panes are paned in the microwave coupling window openings of the metal sash. The microwave transmitters are disposed outside of the plasma reaction chamber and the waveguides are connected to each of the microwave transmitters and each of the panes respectively to form a plurality of plasma excitation units. 
     From the foregoing point of view, in order to actualize the large-area (electron cyclotron resonance) microwave-excited plasma device in the disclosure, the multiple plasma excitation units formed by small-area panes (such as quartz glass) together with metal sash are assembled to escalating the area of the device. Consequently, each of the plasma excitation units can generate plasma independently such that a large-area plasma can be generated by all of the units. Besides, the high cost of the large-area microwave coupling window (made of quartz glass or ceramic) and its deformation together with breakage caused by atmospheric pressure can be prevented by using multiple small-area microwave coupling windows instead of a large-area one. 
     Several exemplary embodiments accompanied with figures are described in detail below to further describe the disclosure in details. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings are included to provide further understanding, and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments and, together with the description, serve to explain the principles of the disclosure. 
         FIG. 1A  is a schematic cross-sectional diagram illustrating a microwave-excited plasma device according to a first exemplary embodiment. 
         FIG. 1B  is a top view of the microwave-excited plasma device in  FIG. 1A . 
         FIG. 2  is a top view of a microwave-excited plasma device in another example of the first exemplary embodiment. 
         FIG. 3  is a schematic cross-sectional diagram illustrating a microwave-excited plasma device according to a second exemplary embodiment. 
         FIG. 4  is a schematic cross-sectional diagram illustrating a microwave-excited plasma device according to a third exemplary embodiment. 
         FIG. 5  is a top view of an electron cyclotron resonance (ECR) plasma excitation device constituted by  36  plasma excitation units. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     To understand the disclosure more thoroughly, please refer to the exemplary embodiment below and the drawings attached. It should be noted that the disclosure can be implemented through various manners and is not limited to the exemplary embodiments described herein. In the drawings, the components and the relative dimensions thereof may not be drawn according to the actual ratio. 
       FIG. 1A  is a schematic cross-sectional diagram illustrating a microwave-excited plasma device according to a first exemplary embodiment. 
     Referring to  FIG. 1A , a microwave-excited plasma device  100  in a first exemplary embodiment at least includes a plasma reaction chamber  102 , a metal sash  104  having a plurality of small-area microwave coupling window openings  106 , a plurality of panes  108 , a plurality of microwave transmitters  110 , and a plurality of waveguides  112 . The metal sash  104  is assembled on the top of the plasma reaction chamber  102  and fabricated using a metal alloy such as aluminum alloy and so on. The panes  108  are, for example, fabricated with quartz, ceramics or other refractory dielectric materials. 
       FIG. 1B  is a top view of the microwave-excited plasma device in  FIG. 1A . Moreover,  FIG. 1A  is a cross-section taken along line I-I in  FIG. 1B . 
     Referring to  FIGS. 1A and 1B  simultaneously, the panes  108  are paned in the small-area microwave coupling window openings  106  of the metal sash  104 . The shadow region in  FIG. 1B  represents the metal sash  104 . The microwave transmitters  110  are disposed outside of the plasma reaction chamber  102 . Each of the waveguides  112  is connected to each of the microwave transmitters  110  and each of the panes  108  respectively to form an independent plasma excitation unit  114  capable of generating microwave plasma independently (in a suitable pressure range of 10 −2  Torr-10 −1  Torr). In order to make the excited plasma diffuse down to the plasma reaction chamber  102  smoothly, an outer margin of each of the window openings  106  is shaped by an incline  116 . In addition, the plasma excitation units  114  can be disposed alternately as depicted in  FIG. 2 . In addition, 12 panes  108  are depicted in  FIG. 1B , which means the microwave-excited plasma device  100  has 12 plasma excitation units  114 . However, the disclosure is not limited thereto and the dimension of the microwave-excited plasma device  100  and the number of the plasma excitation units  114  disposed therein need to be designed according to the area required by some sort of plasma processes. In other words, the entire area of the microwave-excited plasma device  100  can be escalated as the number of the plasma excitation units  114  is increased. On the other hand, the power output of the microwave transmitter of each set of the plasma excitation units can be monitored individually so as to adjust the plasma density by region. As a consequence, the overall plasma uniformity of the microwave-excited plasma device can be enhanced. 
       FIG. 3  is a schematic cross-sectional diagram illustrating a microwave-excited plasma device according to a second exemplary embodiment. Herein, the elements identical or similar to those in  FIG. 1A  are denoted with the same notations; however, the locations and the ratios of each of the elements are not shown in their actual conditions. 
     Referring to  FIG. 3 , in a microwave-excited plasma device  300  in the second exemplary embodiment, other than the structure noted in the first exemplary embodiment, an impedance matching device  302  such as a tapered dielectric material or a tapered waveguide (not shown in the diagram) can be inserted between each of the microwave transmitters  110  and the plasma reaction chamber  102  to reduce microwave reflected powers. Moreover, a plurality of reaction gas tunnels  304  can be drilled in the metal sash  104  for passing reaction gases to each of the plasma excitation units  114  through the aligned gas inlets  306  which align on the inclines  116  of the microwave coupling window openings  106 . A plurality of cooling pipe tunnels  308  is drilled in the metal sash  104  to cool down the permanent magnets  402  and the O rings  404  as shown in following  FIG. 4 . 
       FIG. 4  is a schematic cross-sectional diagram illustrating a microwave-excited plasma device according to a third exemplary embodiment. Herein, the elements identical or similar to those in  FIG. 3  are denoted with the same notations. 
     Referring to  FIG. 4 , in a microwave-excited plasma device  400  of the second exemplary embodiment, a plurality of permanent magnets  402  capable of generating an electron cyclotron resonance (ECR) plasma is disposed on the metal sash  104 , and thus this is an ECR plasma excitation device capable of generating an ECR plasma (in a suitable pressure range of 10 −4  Torr-10 −2  Torr). The permanent magnets  402  can be disposed above the cooling pipe tunnels  308 . In the microwave-excited plasma device  400 , the O-rings  404  can be disposed in a plurality of pre-set trenches between the metal sash  104  and the panes  108  to implement vacuum environment of the plasma reaction chamber  102 . 
       FIG. 5  is a top view illustrating an ECR plasma excitation device  500  constituted by  36  plasma excitation units. Herein, only a metal sash  502 , positions of cross-sections of a plurality of waveguides  504 , positions of a plurality of permanent magnets  506 , and a plurality of window openings  508  in the plasma excitation device  500  are illustrated. The disposition of the permanent magnets  506  is configured for providing the magnetic field required by ECR plasma. Herein, the disclosure is not limited to pillar-shaped magnets and magnets of other shapes can also be adopted. 
     In summary, the disclosure adopts the multiple plasma excitation device constituted by a plurality of panes together with the metal sash. Thus, each of the plasma excitation units can not only independently generate large-area uniform plasma but also the high cost of the large-area quartz glass and its deformation together with breakage caused by the conventional use of large-area microwave coupling windows can be prevented. 
     It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the disclosed embodiments without departing from the scope or spirit of the disclosure. In view of the foregoing, it is intended that the disclosure cover modifications and variations of this disclosure provided they fall within the scope of the following claims and their equivalents.