Patent Publication Number: US-2006011466-A1

Title: Method of fabricting indium tin oxide film with well thermal stabilization and low resistivity

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates generally to an electronic device, and more particularly to a method of fabricating an indium tin oxide (ITO) film, which the film has a well thermal stabilization and a low resistivity.  
      2. Description of the Related Art  
      In a touch panel, the indium tin oxide film (ITO film) is the most import element that affects the quality of the product.  
      In prior art for enhancement of light transmission of the ITO film, the sputtering process is applied to deposit a titanium dioxide film (TiO 2  film), a silicon dioxide film (SiO 2  film) and the ITO film on a plastic substrate in sequence. The TiO 2  film and the SiO 2  film form an oxide dielectric layer for anti-reflection. The ITO film has a high refractive index and the SiO 2  film has a low refractive index, which the difference of phases of reflected light of the ITO film and the SiO 2  film causes destructive interference. As a result, the light transmission the ITO film is increased.  
      In the process of fabrication of the panel, such as annealing, curing and reliability, heat will cause oxygen in the dielectric oxides diffusing into the ITO film that changes the surface resistance of the ITO film, such as the thermal stabilization is decreased and the resistivity is increase, and that makes the ITO film having a poor quality.  
     SUMMARY OF THE INVENTION  
      The primary objective of the present invention is to provide a method of fabricating an ITO film, which processes the oxide dielectric layer with oxygen ion beam to fill the empty portion thereof. Therefore, the ITO film has the stable and fine oxide dielectric layer to make ITO film having a well thermal stabilization and a low resistivity.  
      According to the objectives of the present invention, a method of fabricating an indium tin oxide film (ITO film) with well thermal stabilization and low resistivity comprises the steps of:  
      a) Provide an oxide dielectric layer, which is an oxide film, on a substrate.  
      b) Provide an ion beam, which is generated by introducing oxygen to an ion source, to a surface of the oxide dielectric layer.  
      c) Provide an indium tin oxide film on the surface of the oxide dielectric layer. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a flow chart of a first preferred embodiment of the present invention;  
       FIG. 2 ( a ) to  FIG. 2 ( e ) are sectional views according to the steps of the method of the first preferred embodiment of the present invention, and  
       FIG. 3  is a sectional view of a second preferred embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      As shown in  FIG. 1  and  FIG. 2 , a method of the first preferred embodiment of the present invention comprises the steps of:  
      a) Fabrication of an oxide dielectric layer.  
      Put a substrate  10  in a vacuum chamber of a sputtering machine (not shown). In the present preferred embodiment, the substrate  10  has a transparent plastic film  11  and a hard coating layer  12  on a side of the transparent plastic film  11 , as shown in  FIG. 2 ( a ). The transparent plastic film  11  is made of polymer film, such as polyethylene terephthalate (PET). In practice, the transparent plastic film can be coated with two hard coating layers on opposite sides thereof.  
      Next, a titanium material and a silicon material are applied as a target in the sputtering process and oxygen is provided in the chamber to deposit a titanium dioxide film (TiO 2  film)  21  on a surface  10   a,  which is a side of the transparent plastic film  11  without the hard coating layer  12 , of the substrate  10 , as shown in  FIG. 2 ( b ), and to deposit a silicon dioxide film (SiO 2  film)  22  on the TiO 2  film  21 , as shown in  FIG. 2 ( c ). The TiO 2  film  21  and the SiO 2  film  22  form an oxide dielectric layer  20 . It is a well-known skill to fabricate the oxide dielectric layer in this step, so I would not describe the detail.  
      b) Surface treatment process of the oxide dielectric layer.  
      After Step a), the substrate  10  and the oxide dielectric layer  20  is treated by ion source(not shown), and then introduce oxygen to an ion source to generate an ion beam, the arrow in  FIG. 2 ( d ) shows the ion beam and emit a surface of the oxide dielectric layer  20 . The ion beam fills empty portions of the oxide dielectric layer  20  to make the oxide dielectric layer  20  having a more stable and fine structure.  
      In the present preferred embodiment, in the process of generating ion beam, the ion source is a linear ion source, of course, it also can be a round ion source.  
      c) Fabrication of a transparent conductive film.  
      An Indium Tin Oxide film (ITO film)  30  is deposited on the surface of oxide dielectric layer  20 , as shown in  FIG. 2 ( e ), and the ITO film  30  is the transparent conductive film. In the present preferred embodiment, the ITO film  30  is made by the sputtering process.  
      The present invention provides the oxide dielectric layer  20 , which is designated to be anti-reflection, processed by oxygen ion beam to increase the stability and fin structure of the oxide dielectric layer  20 . Therefore, while the panel is processed under a high-temperature environment, the oxygen in the oxide dielectric layer  20  will not diffuse to the ITO film  30 . As a result, the thermal stabilization and the surface resistance of the ITO film  30  are kept stable to make the ITO film  30  having a high light transmission.  
      Table 1 is the values of surface resistance and resistivity of the ITO films, one of which the oxide dielectric layer thereon is processed by oxygen ion beam and the other is not. The Table 1 shows the surface resistance and the resistivity of the ITO films with the oxide dielectric layer processed by oxygen ion beam are significantly less.  
                           TABLE 1                                   With oxygen ion process   Without oxygen ion process                                                            Before   Surface resistance   392.5   Ω/□   280.1   Ω/□       annealing   Resistivity   8.635 × 10 −4     Ω/□ × cm   6.1622 × 10 −4     Ω/□ × cm       After   Surface resistance   500.8   Ω/□   253.6   Ω/□       annealing   Resistivity   1.10176 × 10 −3     Ω/□ × cm   5.5792 × 10 −4     Ω/□ × cm                  
 
      In addition, the gas provided in the ion surface process could be the mixed gas of argon (Ar) and oxygen.  
      The oxide dielectric layer could have a plurality of the TiO 2  films and the SiO 2  films stacked to increase the efficiency of anti-reflection. Although, the resistivity is increased because of increasing of the stacked films of the oxide dielectric layer, the ion process will reduce the resistivity of ITO film.  
       FIG. 3  shows the second preferred embodiment of the present invention, which is similar to the first preferred embodiment, except that it provides plural TiO 2  films  21  and SiO 2  films  22  stacked on a substrate  10 , which the TiO 2  films  21  and the SiO 2  films  22  form an oxide dielectric layer  20 . After the ion process (the arrow shows the ion beam), an ITO film  30  is deposited on the oxide dielectric layer  20 .  
      Table 2 shows the surface resistances and the resistivity of the ITO films deposited on the oxide dielectric layer consisted of plural TiO 2  films and the SiO 2  films with and without oxygen ion beam process. The results show the surface resistances and the resistivity of the ITO films with oxygen ion beam process are significantly less.  
                           TABLE 2                                   With oxygen ion process   Without oxygen ion process                                                            Before   Surface resistance   415.3   Ω/□   288.8   Ω/□       annealing   Resistivity   9.1366 × 10 −4     Ω/□ × cm   6.3536 × 10 −4     Ω/□ × cm       After   Surface resistance   799.2   Ω/□   303.7   Ω/□       annealing   Resistivity   1.75824 × 10 −3     Ω/□ × cm   6.6814 × 10 −4     Ω/□ × cm                  
 
      The scope of the present invention is not restricted in the preferred embodiments only. Any equivalent structure should be in the claim of the present invention.