Abstract:
Provided are an evaporation apparatus and a thin film forming method using the same. The evaporation apparatus and the thin film forming method are used to form a uniform thin film, even for a large substrate, and can be easily employed without changing equipment even if a substrate size is changed. The evaporation apparatus includes a first evaporation source, a second evaporation source separated from the first evaporation source, and a compensation member disposed between a target object and the first and second evaporation sources. The compensation member performs a linear movement simultaneously with the first and second evaporation sources. The compensation member includes a first compensation plate disposed in a position corresponding to the first evaporation source, and a second compensation plate disposed in a position corresponding to the second evaporation source.

Description:
CLAIM OF PRIORITY 
       [0001]    This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. §119 from an application for EVAPORATION APPARATUS AND THIN FILM FORMING METHOD USING THE SAME earlier filed in the Korean Intellectual Property Office on the 28 of Feb. 2008 and there duly assigned Serial No. 10-2008-0018529. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to an evaporation apparatus and a thin film forming method using the same, and more particularly, to an evaporation apparatus and a thin film forming method using the same which can increase a thickness uniformity of a thin film even when a target object is large. 
         [0004]    2. Description of the Related Art 
         [0005]    In a flat panel display such as an organic light emitting display (OLED), an organic material or a metal used for an electrode is formed as thin films on a flat panel by evaporating a corresponding material in a vacuum atmosphere. 
         [0006]    In such a thin film formation, a thickness uniformity of the thin film greatly affects the features of the flat panel display, such as effective dispersion and color coordinate dispersion. Thus, research has been conducted in order to increase the thickness uniformity of thin films when evaporation is performed. 
         [0007]    For example, according to an evaporation apparatus disclosed in Korean Patent Laid-Open Publication No. 2004-0007811, entitled “A vacuum evaporation apparatus and design method of shield member for the vacuum evaporation apparatus”, the evaporation apparatus includes a shield member for making the thickness of the thin film uniform and which is located between a substrate and an evaporation source heating and evaporating an evaporation material. However, the disclosed evaporation apparatus is intended for small substrates, and thus, it is difficult to apply the disclosed evaporation apparatus to large substrates. 
         [0008]    Japanese Patent Laid-Open Publication No. 2004-238663, entitled “Evaporation apparatus” discloses an evaporation apparatus which attempts to efficiently control a dispersion angle of an evaporation material and to optimize a film thickness distribution. This evaporation apparatus can easily perform evaporation in a large-area substrate by using a linear evaporation source, and includes a shielding element in the linear evaporation source, wherein the shielding element is for shielding the evaporation material. However, this particular evaporation apparatus can only be applied to a fixed evaporation source and has to match a size of a substrate. 
       SUMMARY OF THE INVENTION 
       [0009]    The present invention provides an evaporation apparatus and a thin film forming method using the same, which can be used to form a uniform thin film for different sizes of substrates. 
         [0010]    According to an aspect of the present invention, there is provided an evaporation apparatus, including a first evaporation source, a second evaporation source being separated from the first evaporation source, a compensation member disposed in a space defined by a target object and the first and second evaporation sources. The first and second evaporation sources simultaneously move in a moving direction, and the compensation member moves in the moving direction simultaneously with the first and second evaporation sources. The compensation member includes a first compensation plate disposed in a position closer to the first evaporation source than the second evaporation source, and a second compensation plate disposed in a position closer to the second evaporation source than the first evaporation source. 
         [0011]    The compensation member may further include a support unit connecting the first compensation plate to the second compensation plate. 
         [0012]    The first compensation plate and the second compensation plate may protrude beyond the support unit toward the first evaporation source and the second evaporation source, respectively. The first compensation plate and the second compensation plate may protrude beyond the support unit so as to be respectively parallel to the first evaporation source and the second evaporation source. 
         [0013]    The compensation member may be located at a side of the moving direction with respect to the first and second evaporation sources. The first evaporation source and the second evaporation source may perform a reciprocating linear movement. The compensation member may be located at a side opposite to the moving direction with respect to the first and second evaporation sources. 
         [0014]    The second evaporation source may be separated from the first evaporation source in a direction substantially perpendicular to the moving direction. 
         [0015]    According to another aspect of the present invention, there is provided a thin film forming method, including the operations arranging at least two evaporation sources which are separated from each other, placing a target object to face the at least two evaporation sources, shielding a first space formed between the target object and one of the at least two evaporation sources, shielding a second space formed between the target object and another of the at least two evaporation sources, and forming a thin film on the target object while simultaneously moving the at least two evaporation sources in a moving direction. The first space is closer to the one of the at least two evaporation sources, and the second space is closer to the another of the at least two evaporation sources. 
         [0016]    An amount of evaporation material shielded in the first and second spaces is greater than an amount of evaporation material shielded in a position corresponding to a distance between each of the at least two evaporation sources. 
         [0017]    The step of shielding the first space may include a step of placing a first compensation plate in the first space, and the step of shielding the second space may include a step of placing a second compensation plate in the second space. The step of forming the thin film may include a step of forming a thin film on the target object while reciprocating the at least two evaporation sources simultaneously with the first and second compensation plates. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]    A more complete appreciation of the invention, and many of the attendant advantages thereof, will be readily apparent as the same becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings in which like reference symbols indicate the same or similar components, wherein: 
           [0019]      FIG. 1  is a perspective view of an evaporation apparatus according to an embodiment of the present invention; 
           [0020]      FIG. 2  is a plan view of evaporations sources and compensation members in the evaporations apparatus of  FIG. 1 , according to an embodiment of the present invention; 
           [0021]      FIG. 3  is a cross-sectional view of the evaporation apparatus of  FIG. 1 , taken along line III-III of  FIG. 2 , according to an embodiment of the present invention; 
           [0022]      FIG. 4  is a drawing for illustrating a design concept of the compensation members in the evaporation apparatus of  FIG. 1 , according to an embodiment of the present invention; and 
           [0023]      FIG. 5  is a diagram of a thin film profile formed without using the compensation members in the evaporation apparatus of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0024]    The present invention will now be described more fully with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. 
         [0025]      FIG. 1  is a perspective view of an evaporation apparatus constructed as an embodiment of the present invention. Although a chamber is not illustrated in  FIG. 1  for convenience of description, all components illustrated in  FIG. 1  may be arranged in a chamber in which an appropriate vacuum is maintained. 
         [0026]    In a chamber, a substrate  12 , on which a thin film is to be formed, is disposed. The substrate  12  may be for a flat panel display. The substrate  12  may be a larger area substrate such as a mother glass used to form a plurality of flat panel displays. 
         [0027]    Referring to  FIG. 1 , a plurality of evaporation sources  20  is disposed on an upper surface of a base  10  facing the substrate  12 . That is, referring to  FIG. 1 , the evaporation sources  20  are disposed on the base  10  which faces the substrate  12  but is separated from the substrate  12  in a Z-axis direction. The base  10  is arranged so as to be installed on guide rails  11  extending in a Y-axis direction in the chamber, and to perform a reciprocating movement in the Y-axis direction along the guide rails  11 . Thus, the base  10  is connected to a separate driving unit (not shown), and is driven. 
         [0028]    The evaporation sources  20  include a first evaporation source  22  and a second evaporation source  23 . As illustrated in  FIG. 1 , the first evaporation source  22  and the second evaporation source  23  are arranged so as to be separated from each other by a predetermined distance, and to simultaneously move in the same direction (the Y-axis direction). Also, each of the first and second evaporation sources  22  and  23  may include a plurality of evaporation crucibles  21 . The evaporation crucibles  21  in each of the first and second evaporation sources  22  and  23  may be rectilinearly aligned in the same direction (the Y-axis direction). However, the present invention is not limited thereto, that is, the evaporation crucibles  21  may be arranged randomly in the first and second evaporation sources  22  and  23 . The evaporation crucibles  21  may be linear crucibles extending in the Y-axis direction. 
         [0029]    In the current embodiment, the evaporation sources  20  have been described as including two evaporation sources, that is, the first evaporation source  22  and the second evaporation source  23 . However, the present invention is not limited thereto, and the evaporation sources  20  may include more than two evaporation sources. In such a case, a shape of a compensation member to be described later has to be arranged so as to correspond to this structure. 
         [0030]    When a thin film is formed via an evaporation using the evaporation sources  20  with the aforementioned structure as illustrated in  FIG. 1 , the formed thin film has a profile as illustrated in  FIG. 5 . 
         [0031]    In this case, as illustrated in  FIG. 5 , non-uniformity of film thickness occurs. That is, portions of the thin film directly facing the evaporation sources  20  are considerably thicker than portions of the thin film located between the first and second evaporation sources  22  and  23 . 
         [0032]    In order to prevent the film non-uniformity, the evaporation apparatus of the current embodiment of the present invention includes a first compensation member  30  and a second compensation member  40 , which have structures illustrated in  FIG. 2 , and which are disposed next to the evaporation sources  20 , partially blocking a space formed between the substrate  12  and the evaporation sources  20 . 
         [0033]      FIG. 2  is a plan view of the evaporations sources  20  and the first and second compensation members  30  and  40  of the evaporations apparatus of  FIG. 1 , constructed as an embodiment of the present invention.  FIG. 3  is a cross-sectional view of the evaporation apparatus of  FIG. 1 , taken along line III-III of  FIG. 2 , according to an embodiment of the present invention. 
         [0034]    Referring to  FIG. 2 , the first compensation member  30  and the second compensation member  40  of the current embodiment of the present invention are separated from each other by a predetermined distance in the Y-axis direction, and the evaporation sources  20  are disposed between the first compensation member  30  and the second compensation member  40 . 
         [0035]    The first compensation member  30  and the second compensation member  40  respectively include first compensation plates  32  and  42  arranged at positions corresponding to (or closer to) the first evaporation source  22 , and second compensation plates  33  and  43  arranged at positions corresponding to (or closer to) the second evaporation source  23 . That is, the first compensation plate  32  of the first compensation member  30  and the first compensation plate  42  of the second compensation member  40  face each other. Also, the second compensation plate  33  of the first compensation member  30  and the second compensation plate  43  of the second compensation member  40  face each other. When viewed from the top as illustrated in  FIG. 2 , the first evaporation source  22  is disposed between the first compensation plate  32  of the first compensation member  30  and the first compensation plate  42  of the second compensation member  40 , and the second evaporation source  23  is disposed between the second compensation plate  33  of the first compensation member  30  and the second compensation plate  43  of the second compensation member  40 . 
         [0036]    The first compensation member  30  and the second compensation member  40  respectively include support units  34  and  44  extending parallel to a direction from the first evaporation source  22  to the second evaporation source  23 , that is, in an X-axis direction of  FIG. 2 . The first compensation plates  32  and  42  and the second compensation plates  33  and  43  respectively protrude beyond the support units  34  and  44  toward the first and second evaporation sources  22  and  23 . Thus, in the first compensation member  30  and the second compensation member  40 , the first compensation plates  32  and  42 , the support units  34  and  44 , and the second compensation plates  33  and  43 , are arranged in a form of a wave. 
         [0037]    As illustrated in  FIG. 3 , the first compensation plates  32  and  42  and the second compensation plates  33  and  43  protrude beyond the support units  34  and  44  in a manner that the plate surfaces of the first compensation plates  32  and  42  and the second compensation plates  33  and  43  are parallel to the first evaporation source  22  and the second evaporation source  23 . In other words, the plate surface of the first compensation plates  32  and  42  are disposed substantially parallel to a top surface of the first evaporation source  22 , and the second compensation plates  33  and  43  are disposed substantially parallel to a top surface of the second evaporation source  23 . 
         [0038]    The first compensation member  30  and the second compensation member  40  with the aforementioned structure are respectively connected to a first shielding wall  31  and a second shielding wall  41  which extend from the base  10 . Referring to  FIG. 3 , the first shielding wall  31  and the second shielding wall  41  reduce an evaporation angle to a direction (the Y-axis direction) that is perpendicular to a direction (the X-axis direction) in which the first and second evaporation sources  22  and  23  are arranged. Thus, in the case where a mask is interposed between the substrate  12  and the evaporation sources  20 , a shadow effect may be reduced. 
         [0039]    Meanwhile, in the present invention, both of the first compensation member  30  and the second compensation member  40  may not be necessarily to achieve the goal of the present invention. In other words, only one compensation member can be included in the evaporation apparatus of the present invention. 
         [0040]    Also, the first compensation plate  32  and the second compensation plate  33  of the first compensation member  30  may be disposed to be closer to each other. Protrusion positions of the first compensation plate  32  and the second compensation plate  33  may be disposed to be closer than positions located immediately above the first and second evaporation sources  22  and  23 . Similarly, the first compensation plate  42  and the second compensation plate  43  of the second compensation member  40  may be disposed to be closer to each other. A distance between the first compensation plate  42  and the second compensation plate  43  is not required to be equal to a distance between the first compensation plate  32  and the second compensation plate  33 . That is, the distance between the first compensation plate  42  and the second compensation plate  43  may be shorter or longer than the distance between the first compensation plate  32  and the second compensation plate  33 . 
         [0041]    The first compensation member  30  and the second compensation member  40  may be disposed to be closer to each other, such that the first compensation member  30  and the second compensation member  40  may be disposed immediately above outermost evaporation crucibles  21  of the first and second evaporation sources  22  and  23  which are linearly arranged, as illustrated in  FIG. 2 . Otherwise, the first compensation member  30  and the second compensation member  40  may be disposed to be further away from each other. 
         [0042]    As described above, a desired dispersion angle of the first and second evaporation sources  22  and  23  may be adjusted by calibrating a distance between the first compensation plates  32  and  42 , and a distance between the second compensation plates  33  and  43 , or by calibrating a distance between the first compensation member  30  and the second compensation member  40 , such that an appropriate design according to a feature of an evaporation material is possible. 
         [0043]    In the evaporation apparatus according to the current embodiment of the present invention, the evaporation material is dispersed from the first and second evaporation sources  22  and  23  while the base  10  moves on the guide rails  11  in the Y-axis direction. 
         [0044]    An evaporation amount according to the moving direction of the evaporation sources  20  is controlled by the first compensation member  30  and the second compensation member  40 , and this control is performed by compensating the profile illustrated in  FIG. 5 , such that a uniform thin film may be formed. 
         [0045]      FIG. 4  is a drawing for illustrating a design concept of the first compensation member  30  and the second compensation member  40 , according to an embodiment of the present invention. An X-axis of the graph of  FIG. 4  represents positions of a first evaporation source and a second evaporation source. A Y-axis of the graph represents a height from the first and second evaporation sources to an evaporation surface of a substrate. 
         [0046]    Referring to  FIG. 4 , the first evaporation source and the second evaporation source emit an evaporation material toward the evaporation surface of the substrate such that the evaporation paths of the evaporation materials emitted by the first and e second evaporation sources overlap each other. The first evaporation source emits the evaporation material toward the evaporation surface of the substrate, covering an area between A 1  and A 2 . The second evaporation source emits the evaporation material toward the evaporation surface of the substrate, covering an area between B 1  and B 2 . 
         [0047]    Meanwhile, referring to  FIG. 4 , the first evaporation source emits the evaporation material toward a half of the evaporation surface of the substrate, in which the first evaporation source is located, via an evaporation profile located between A 1  and A 3 . Also, the second evaporation source emits the evaporation material toward the other half of the evaporation surface of the substrate, in which the second evaporation source is located, via an evaporation profile located between B 1  and B 3 . 
         [0048]    A first compensation plate is designed so as to be disposed within the evaporation profile located between A 1  and A 3  so that a shielding amount illustrated in  FIG. 4  is achieved in the half of the substrate where the first evaporation source is located. A second compensation plate is designed so as to be placed within the evaporation profile located between B 1  and B 3  so that a shielding amount illustrated in  FIG. 4  is achieved in the other half of the substrate where the second evaporation source is located. As illustrated in  FIG. 4 , a shielding amount via a support unit located between the first compensation plate and the second compensation plate is less than the shielding amount of the first compensation plate and the second compensation plate. Therefore, a thickness of a thin film may be formed to be uniform. 
         [0049]    A design for a first compensation member and a second compensation member is not necessarily limited so as to achieve the shielding amount illustrated in  FIG. 4 , but may vary according to the features of the evaporation material, such as dispersion speed, mass, density, film compactness based on such features, film thickness uniformity, and the like. For example, as described above, the distance between the first compensation plate  32  and the second compensation plate  33  of the first compensation member  30 , the distance between the first compensation plate  42  and the second compensation plate  43  of the second compensation member  40 , or the distance between the first compensation member  30  and the second compensation member  40  may vary. Also, an installation height of each of the first compensation member  30  and the second compensation member  40  may vary. 
         [0050]    Accordingly, the evaporation material dispersed from the second evaporation source  23  may be partly shielded by the first compensation plates  32  and  42 , and the evaporation material dispersed from the first evaporation source  22  may be partly shielded by the second compensation plates  33  and  43 . Thus, according to a design condition, the shielding amount of the evaporation material may be variously controlled. 
         [0051]    Meanwhile, the support units  34  and  44 , respectively located between the first compensation plate  32  and the second compensation plate  33 , and between the first compensation plate  42  and the second compensation plate  43 , shield the evaporation material dispersed from the first and second evaporation sources  22  and  23 , with a steep angle greater than a predetermined angle, thereby reducing a shadowing effect. That is, the support units  34  and  44  may also serve as an angle control plate. 
         [0052]    Hereinafter, a thin film forming method using the evaporation apparatus illustrated in  FIGS. 1 to 3  will be described, according to an embodiment of the present invention. 
         [0053]    Referring to  FIGS. 1 through 3 , the first evaporation source  22  and the second evaporation source  23 , which are separated from each other in a chamber, are arranged. 
         [0054]    Then, the substrate  12  is disposed so as to face the first and second evaporation sources  22  and  23 . 
         [0055]    When a predetermined vacuum or an inactive atmosphere is maintained inside the chamber, the first and second evaporation sources  22  and  23  are driven so as to emit an evaporation material toward the substrate  12 , while the base  10  is moving in a moving direction along a Y-axis. 
         [0056]    At this time, a space which corresponds to a position of the first evaporation source  22 , is shielded by the first compensation plates  32  and  42  which are respectively located at the side of and at the opposite side of the moving direction of the first evaporation source  22 . Thus, an amount of the evaporation material dispersed from the first evaporation source  22  is partly shielded, as illustrated in  FIG. 4 . 
         [0057]    Similarly, a space which corresponds to a position of the second evaporation source  23 , is shielded by the second compensation plates  33  and  43  which are respectively located at the side of and at the opposite side of the moving direction of the second evaporation source  23 . Thus, an amount of the evaporation material dispersed from the second evaporation source  23  is also partly shielded, as illustrated in  FIG. 4 . 
         [0058]    The amount of the evaporation material shielded in a position corresponding to the space between the first evaporation source  22  and the second evaporation source  23  is less than that the amount of the evaporation material shielded in positions respectively corresponding to the first and second evaporation sources  22  and  23 , as illustrated in  FIG. 4 . 
         [0059]    Accordingly, a film may be formed to have a uniform thickness. The film may be formed to have a desired thickness by a reciprocating movement of the base  10  in the Y-axis direction. 
         [0060]    According to the present invention, the thickness of an evaporated film can be formed to be uniform even when an evaporation source for a large substrate is employed. Also, the evaporation apparatus of the present invention can be easily employed with different sized substrates. 
         [0061]    While this invention has been particularly shown and described with reference to exemplary embodiments thereof, 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 of the invention as defined by the appended claims. The exemplary embodiments should be considered in a descriptive sense only and not for purposes of limitation. Therefore, the scope of the invention is defined not by the detailed description of the invention but by the appended claims, and all differences within the scope will be construed as being included in the present invention.