Abstract:
A method of manufacturing a nano antenna is provided. The method includes forming a material layer on a substrate, defining a portion of the material layer, forming an adhesion layer on the defined portion of the material layer, forming a nano antenna material layer on the adhesion layer, and removing the adhesion layer to thereby manufacture the nano antenna.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority from Korean Patent Application No. 10-2015-0161056, filed on Nov. 17, 2015, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference in its entirety. 
       BACKGROUND 
       [0002]    1. Field 
         [0003]    The exemplary embodiments disclosed herein relate to methods of manufacturing a nano antenna. 
         [0004]    2. Description of the Related Art 
         [0005]    A nano antenna is used to receive and transmit light. Light having a wavelength that resonates with a nano antenna is transmitted and/or received by the nano antenna. According to the change of the refractive index of a transparent conductive layer adjacent to the nano antenna, the phase of the light emitted from the nano antenna may be changed. 
         [0006]    A gold layer may be used as a material for the nano antenna. The gold layer may be patterned by using a lift-off process. However, since the gold layer has a poor adhesion force, the performance of a complete patterning of the gold layer may be difficult during the lift-off process and a portion of the gold layer may exfoliate. 
       SUMMARY 
       [0007]    Exemplary embodiments provide methods of manufacturing a nano antenna, wherein the methods may prevent an adverse effect (for example, exfoliation of nano antenna material) that may occur in a process of patterning the nano antenna and may completely ensure operation characteristics of the nano antenna. 
         [0008]    According to an aspect of an exemplary embodiment, there is provided a method of manufacturing a nano antenna, the method including: forming a material layer on a substrate; defining a portion of the material layer; forming an adhesion layer on the defined portion of the material layer; forming a nano antenna material layer on the adhesion layer; and removing the adhesion layer. 
         [0009]    The defining of the portion of the material layer may include forming a mask that exposes the portion of the material layer on the material layer. 
         [0010]    The forming of the material layer may include: forming a mirror layer on the substrate; forming a transparent conductive layer on the mirror layer; and forming an insulating layer on the transparent conductive layer. 
         [0011]    The adhesion layer may include one of a chrome layer and a titanium layer. 
         [0012]    The removing of the adhesion layer may include removing the adhesion layer using an ashing process. 
         [0013]    The forming of the adhesion layer and the forming of the nano antenna material layer may include sequentially forming the adhesion layer and the nano antenna material after the forming of the mask, and the method may further include removing the mask before removing the adhesion layer. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    The above and/or other aspects will become apparent and more readily appreciated from the following description of exemplary embodiments, taken in conjunction with the accompanying drawings in which: 
           [0015]      FIGS. 1, 2, 3, 4 and 5  are cross-sectional views illustrating a method of manufacturing a nano antenna, according to an exemplary embodiment; 
           [0016]      FIG. 6  is a graph showing the change of a resonance dip before and after performing an ashing process in a method of manufacturing a nano antenna, according to an exemplary embodiment; 
           [0017]      FIGS. 7A and 7B  are plan views showing no size change of a nano antenna before and after performing an ashing process in a method of manufacturing a nano antenna, according to an exemplary embodiment; 
           [0018]      FIGS. 8A and 8B  are transmission electron microscope (TEM) images showing a nano antenna is in contact with an insulating layer after removing an adhesion layer by using an ashing process in a method of manufacturing a nano antenna, according to an exemplary embodiment; and 
           [0019]      FIGS. 9A and 9B  are composition analysis images showing a nano antenna is in contact with an insulating layer after removing an adhesion layer by using an ashing process in a method of manufacturing a nano antenna, according to an exemplary embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0020]    Gold Au may be used as a material for forming a nano antenna. However, since a gold layer has poor adhesiveness, an exfoliation may occur during patterning. To prevent the exfoliation, an adhesion layer that has high adhesiveness is used, and the gold layer is patterned on the adhesion layer. 
         [0021]    According to some currently developed nano antenna structures, a resonance phenomenon is needed at an interface between the gold layer and an insulating layer. However, since the adhesion layer is inserted between the gold layer and the insulating layer, the adhesion layer may have an adverse effect on the operation of the nano antenna and a normal operation of the nano antenna may therefore be limited. 
         [0022]    In the method of manufacturing a nano antenna according to an exemplary embodiment, the adhesion layer is removed from the interface between the gold layer (also referred to as a nano antenna material layer) and the insulating layer to remove the adverse effect caused by the adhesion layer. 
         [0023]    Hereinafter, a method of manufacturing a nano antenna according to an exemplary embodiment will be described in detail with reference to the accompanying drawings. In the drawings, the thicknesses of layers or regions may be exaggerated for clarity. 
         [0024]      FIGS. 1 through 5  are cross-sectional views illustrating a method of manufacturing a nano antenna, according to an exemplary embodiment; 
         [0025]    Referring to  FIG. 1 , a mirror layer  20  is formed on a substrate  10 . The substrate  10  may be a surface of an apparatus on which a nano antenna is mounted. The mirror layer  20  is a reflection layer, for example, a gold layer. A transparent conductive layer  22  and an insulating layer  24  are sequentially formed on the mirror layer  20 . The transparent conductive layer  22  may be, for example, a transparent conductive oxide (TCO) layer. The TCO layer may be, for example, one of an indium tin oxide (ITO) layer, an indium zinc oxide (IZO) layer, a gallium indium zinc oxide (GIZO) layer, an indium gallium zinc oxide (IGZO) layer, and a hafnium oxide (HfOx) layer. The insulating layer  24  may be, for example, an oxide layer. In this case, the oxide layer may be, for example, an aluminum oxide (Al 2 O 3 ) layer. The mirror layer  20 , the transparent conductive layer  22 , and the insulating layer  24  that are sequentially formed on the substrate  10  may be collectively referred to as a “lower material layer”. 
         [0026]    Next, as depicted in  FIG. 2 , a mask  28  is formed on the insulating layer  24 . The mask  28  may be formed on only a region (e.g., less than an entire surface) of the insulating layer  24 . Accordingly, after forming the mask  28 , a portion of an upper surface of the insulating layer  24  is exposed. The mask  28  may be, for example, a photoresist film. 
         [0027]    Next, after the mask  28  is formed, as depicted in  FIG. 3 , an adhesion layer  26  and a nano antenna material layer  30  are sequentially formed on the exposed portion of the insulating layer  24 . The adhesion layer  26  may cover the entire exposed upper surface of the insulating layer  24  between the masks  28 . The nano antenna material layer  30  may cover the entire upper surface of the adhesion layer  26 . The nano antenna material layer  30  may have a thickness smaller than a thickness of the mask  28 . The nano antenna material layer  30  may include, for example, a gold layer. When the adhesion layer  26  and the nano antenna material layer  30  are formed, the adhesion layer  26  and the nano antenna material layer  30  are also sequentially deposited on the mask  28 . The adhesion layer  26  and the nano antenna material layer  30  that are deposited on the mask  28  are removed together with the mask  28  when the mask  28  is removed. The adhesion layer  26  may be formed to have a thickness that is less than a thickness of other layers. The adhesion layer  26  may prevent exfoliation of the nano antenna material layer  30  during a process for removing the mask  28 , that is, during a lift-off process after forming the mask  28  and forming the nano antenna material layer  30  on a selected region by the mask  28 . In other words, the adhesion layer  26  may prevent an adverse effect, for example, the exfoliation of the nano antenna pattern that may occur while forming a nano antenna pattern. 
         [0028]    The adhesion layer  26  may be formed of many different materials that may attach the nano antenna material layer  30  to the insulating layer  24 . The adhesion layer  26  may be, for example, one of a chrome layer and a titanium layer. Since the adhesion layer  26  is removed in a subsequent process, the adhesion layer  26  may be formed to have an appropriate thickness, for example, in a range from about 1 nm to about 10 nm, although is not limited thereto. 
         [0029]    After sequentially forming the adhesion layer  26  and the nano antenna material layer  30 , the mask  28  is removed. After the mask  28  is removed, as depicted in  FIG. 4 , the nano antenna material layer  30  remains only on the insulating layer  24 . The nano antenna material layer  30  on the insulating layer  24  may not be exfoliated in the process of removing the mask  28  due to the adhesion layer  26  and may maintain a complete shape. After the mask  28  is removed, the nano antenna material layer  30  that remains on the insulating layer  24  may be substantially used as a nano antenna. The adhesion layer  26  between the nano antenna material layer  30  and the insulating layer  24  may be removed by using an appropriate process that may remove only the adhesion layer  26  by taking into account a material used for forming the adhesion layer  26 . As an example, the adhesion layer  26  between the nano antenna material layer  30  and the insulating layer  24  may be removed by using an ashing process. In this case, the ashing process may be the same as an ashing process that is used for manufacturing semiconductor devices. The ashing process may act only on the adhesion layer  26  between the nano antenna material layer  30  and the insulating layer  24 . The ashing process may not act on the other material layers or may only insignificantly act on the other material layers, and thus, may be negligible. 
         [0030]    The adhesion layer  26  between the nano antenna material layer  30  and the insulating layer  24  may be removed by the ashing process. As a result, as depicted in  FIG. 5 , the nano antenna material layer  30  directly contacts the insulating layer  24 . Since the adhesion layer  26  formed between the nano antenna material layer  30  and the insulating layer  24  is removed by the ashing process and the nano antenna material layer  30  is directly in contact with the insulating layer  24 , a resonance phenomenon may occur in a normal fashion at an interface between the nano antenna material layer  30  and the insulating layer  24 . Accordingly, an optical action (for example, a phase change of light, a change of a moving direction of light, etc.) of the nano antenna material layer  30  with respect to incident light may normally occur. 
         [0031]      FIG. 6  is a graph showing the change in a resonance dip before and after performing an ashing process for removing the adhesion layer  26  between the nano antenna material layer  30  and the insulating layer  24  in a method of manufacturing a nano antenna, according to an exemplary embodiment. 
         [0032]    In  FIG. 6 , the horizontal axis indicates a wavelength of light incident to the nano antenna material layer  30  and the vertical axis indicates reflectance. 
         [0033]    In  FIG. 6 , a first graph G 1  shows a resonance dip before performing an ashing process and a second graph G 2  shows a resonance dip after performing an ashing process. 
         [0034]    When the first graph G 1  is compared with the second graph G 2  of  FIG. 6 , it is seen that, after performing the ashing process, the resonance dip is shifted to the right side and the reflectance is further reduced at the position of the resonance dip. The change which occurs before and after performing an ashing process in the method described above is that the adhesion layer  26  is removed from the interface between the nano antenna material layer  30  and the insulating layer  24 . Accordingly, the result shown in  FIG. 6  illustrates the benefits achieved when the adhesion layer  26  between the nano antenna material layer  30  and the insulating layer  24  is removed by the ashing process. 
         [0035]      FIGS. 7A and 7B  are plan views showing that a width of a nano antenna in a method of manufacturing a nano antenna, according to an exemplary embodiment, is not changed by an ashing process. 
         [0036]      FIG. 7A  is a plan view of the nano antenna material layer  30  before performing an ashing process, and  FIG. 7B  is a plan view of a nano antenna to which a series of processes are further performed after performing the ashing process. 
         [0037]    When  FIG. 7A  is compared with  FIG. 7B , the shape of the nano antenna material layer  30  is the same and a width and a length thereof are unchanged. 
         [0038]    The result shown in  FIGS. 7A and 7B  illustrates that the ashing process may not affect the dimensions (shape, length, width, etc.) of the nano antenna material layer  30 . In other words, the result shown in  FIGS. 7A and 7B  indicates that the dimensions of the nano antenna material layer  30  are not affected by the ashing process. 
         [0039]      FIGS. 8A and 8B  are transmission electron microscope (TEM) images of the nano antenna material layer  30  and a material layer structure below the nano antenna material layer  30  before and after performing an ashing process in a method of manufacturing a nano antenna described above, respectively. 
         [0040]      FIG. 8A  shows a TEM image of the nano antenna material layer  30  and the material layer structure below the nano antenna material layer  30  before performing an ashing process, and  FIG. 8B  shows a TEM image of the nano antenna material layer  30  and the material layer structure below the nano antenna material layer  30  to which a series of processes are further performed after performing an ashing process. 
         [0041]    The size of the nano antenna material layer  30  of  FIG. 8B  is smaller than that of the nano antenna material layer  30  of  FIG. 8A . This size decrease is the effect of subsequent processes after the ashing process, and not an effect of the ashing process. 
         [0042]    When  FIG. 8A  is compared with  FIG. 8B , after the adhesion layer  26  is removed from the interface between the nano antenna material layer  30  and the insulating layer  24 , it is seen that the nano antenna material layer  30  is on the insulating layer and in contact with the insulating layer  24 . In particular,  FIG. 8B  shows that the nano antenna material layer  30  is still in contact with the insulating layer  24  although a series of processes are further performed after the ashing process. 
         [0043]    The result of  FIG. 8  denotes that the nano antenna material layer  30  is safely on the insulating layer  24  and in contact with the insulating layer  24  without being exfoliated from the insulating layer  24  although the adhesion layer  26  is removed from an interface between the nano antenna material layer  30  and the insulating layer  24  by the ashing process. 
         [0044]      FIGS. 9A and 9B  are images of a composition analysis of the nano antenna material layer  30  and the material layer structure below the nano antenna material layer  30  before and after performing an ashing process in a method of manufacturing a nano antenna, according to an exemplary embodiment. 
         [0045]      FIG. 9A  is an image of a composition analysis with respect to the nano antenna material layer  30  and the material layer structure below the nano antenna material layer  30  before performing an ashing process, and  FIG. 9B  is an image of a composition analysis of the nano antenna material layer  30  and the material layer structure below the nano antenna material layer  30  after further performing a series of processes after the ashing process. The size of the nano antenna material layer  30  of  FIG. 9B  is smaller than a size of the nano antenna material layer  30  of  FIG. 9A . This size decrease is the result of subsequent processes after the ashing process, and not the result of the ashing process. 
         [0046]    Images of  FIGS. 9A and 9B  show that the nano antenna material layer  30  is in contact with the insulating layer  24  after the adhesion layer  26  is removed from the interface between the nano antenna material layer  30  and the insulating layer  24  by the ashing process. In particular,  FIG. 9B  shows that the nano antenna material layer  30  is still in contact with the insulating layer  24  although various processes are further performed after the ashing process. The result of  FIGS. 9A and 9B , similar to the result of  FIGS. 8A and 8B , indicates that the nano antenna material layer  30  is safely on the insulating layer  24  and in contact with the insulating layer  24  without being exfoliated from the insulating layer  24  although the adhesion layer  26  is removed from an interface between the nano antenna material layer  30  and the insulating layer  24  by the ashing process. 
         [0047]    While one or more exemplary embodiments have been described with reference to the figures, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope as defined by the following claims.