Patent Publication Number: US-2005129848-A1

Title: Patterned deposition source unit and method of depositing thin film using the same

Description:
This application claims the priority of Korean Patent Application No. 2003-91947, filed on Dec. 16, 2003 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.  
     BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to a semiconductor device, and more particularly, to a vaporization boat for depositing a thin film and a method of depositing a thin film using the same.  
      2. Description of the Related Art  
      A representative method for forming a thin film on a substrate is a sputtering method since it forms a relatively high density thin film when compared to other methods. However, this method requires an area of an upper surface of the vaporization boat to be almost twice the area of the substrate to maintain uniformity of the thin film at a desired level. Therefore, this method has a drawback in that the overall size of a vacuum chamber is increased due to the large area of the vaporization boat.  
      On the other hand, there is a method of depositing a thin film using a small boat called an electron beam (E-beam) deposition method. However, this method requires a sufficient distance between a deposition source unit and a substrate, which also requires an increase in size of a vacuum chamber, and another disadvantage of this method is that the density of a manufactured thin film is relatively low.  
      Therefore, research on a classic thermal deposition method that uses resistance heating, which is economically superior to the conventional methods of forming a thin film, is actively in process. The thermal deposition method is a general method for coating a metal such as aluminum, copper, or zinc on a variety of substrates composed of semiconductor, glass, or plastic, which are not largely restricted by a deposition material to be coated. Generally, a deposition material, i.e., a metal, is vaporized by electrical resistance heat in a self heat generating vessel called a “vaporization boat.” 
       FIG. 1  is a perspective view of a depositor according to a conventional resistance heat method.  
      Referring to  FIG. 1 , a substrate  14  is disposed in an upper part of a vacuum chamber  10   a  of a depositor  10 . The substrate  14  can be loaded into the vacuum chamber  10   a  individually or continuously. A deposition material loaded on the vaporization boat  20  is evaporated by self heat of the vaporization boat  20  and adhered to a lower surface of the substrate  14 , so that a thin film is formed on the lower surface of the substrate  14 .  
       FIG. 2  is a perspective view for describing a conventional vaporization boat  20  used for the depositor of  FIG. 1 . Referring to  FIG. 2 , the vaporization boat  20  has a bar-shape having both ends  22  connected to a power source. A dimple cavity  26  in which a deposition material  28  is loaded, is formed on the central portion of the vaporization boat  20 , and high resistance regions  24  are formed on both sides of the dimple cavity  26 . The high resistance regions  24  are narrowed cross-sections having notches  24   a.    
      The vaporization boat  20  is formed of a fireproof metal such as W, Ta, or Mo, and generates joule heat via a very high current i of approximately 100 A.  
      However, as in the electron beam deposition method, since the thermal resistance deposition method has a dispersion problem of vaporized deposition material, a sufficient distance between the deposition source unit and the substrate  14  is also required to obtain a uniform thickness of a thin film.  
      Also, there is a problem in that a thin film formed by the thermal deposition method is of a lower film density than a thin film formed by the sputtering method.  
     SUMMARY OF THE INVENTION  
      To solve the above and/or other problems, the present invention provides a vaporization boat that can reduce the size of an evaporator by reducing the distance between a deposition source unit and a substrate and can increase uniformity and density of a thin film, and a method of depositing a thin film using the same.  
      The present invention also provides a vaporization boat that can form a uniform thickness thin film on a substrate and a method of applying the vaporization boat.  
      According to an aspect of the present invention, there is provided a vaporization boat comprising a main body that includes a loading section with a predetermined depth for loading a deposition material; and a cover unit formed of the same material as the main body, wherein the cover unit covers openings of the loading section and a plurality of line shaped openings.  
      The cover unit works as an auxiliary heat source, and a current is applied to the main body and the cover unit to heat the deposition material.  
      According to another aspect of the present invention, there is provided a deposition method for forming a thin film on a substrate using a patterned deposition source unit having a parallel line shaped pattern, the method comprising: loading the patterned deposition source unit in an evaporator; loading the substrate into the evaporator; vaporizing a source material by applying a current to the patterned deposition source unit; performing deposition for a first predetermined number of hours by moving the substrate along a perpendicular direction to the line shaped pattern of patterned deposition source unit; and performing deposition for a second predetermined number of hours by moving again the substrate in a perpendicular direction to the line shaped pattern of patterned deposition source unit after passing over the patterned deposition source unit and after rotating the substrate  900 .  
      According to still another aspect of the present invention, there is provided a deposition method for forming a thin film on a substrate using a patterned deposition source unit having a parallel line shaped pattern, comprising the method comprising: (a) loading the patterned deposition source unit in an evaporator; (b) loading the substrate in the evaporator; (c) vaporizing a source material by applying a current to the patterned deposition source unit; (d) performing deposition for a predetermined hours by moving patterned deposition source unit in a first direction; and (e) performing deposition for a predetermined number of hours by moving the patterned deposition source unit in a second direction which is different from the first direction after rotating the substrate with a predetermined angle after (d). 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The above and other features and advantages of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings in which:  
       FIG. 1  is a perspective view of an evaporator according to a conventional resistance heat method;  
       FIG. 2  is a perspective view of a conventional vaporization boat used for a depositor;  
       FIG. 3  is a perspective view of a vaporization boat according to an embodiment of the present invention;  
       FIG. 4  is a cross-sectional view of a vaporization boat taken at line I-I′ in  FIG. 3 ; and  
       FIG. 5  is a perspective view for describing a deposition method by moving substrate within the depositor using a vaporization boat that includes a patterned cover unit with line shaped openings, according to an embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      Hereinafter, a vaporization boat that includes a patterned cover unit with a plurality of line shaped openings and a deposition method using the vaporization boat according to the present invention will now be described more fully with accompanying drawings.  
       FIG. 3  is a perspective view of a vaporization boat according to an embodiment of the present invention.  FIG. 4  is a cross-sectional view of a vaporization boat taken at line I-I′ in  FIG. 3 .  
      Referring to  FIGS. 3 and 4 , a vaporization boat  100  comprises a main body  102  that includes a loading section  108  having a dimple shape in a central portion in which a deposition material  110  is loaded, and a cover unit  104  that has a plurality of line shaped openings  106 .  
      The plurality of line shaped openings  106  formed on the cover unit  104  each preferably has a width in a range of 1˜500 μm and preferably has a length formed to the same length as the deposition material  110 . It is preferable that the main body  102  of the vaporization boat  100  is formed of a fireproof metal such as W, Ta, or Mo and that the deposition material  110  has a lower melting point than that of the main body  102  and the cover unit  104 .  
      Joule heat is generated by allowing to flow a current of approximately 100 A on both ends of the main body  102  of the vaporization boat  100 . The amount of heat generated thereby is i 2 R, where R is a value of a parallel resistance between the main body  102  and the deposition material  110  at a deposition temperature T.  
      The patterned cover unit  104  formed on the main body  102  also works as an auxiliary heat source for heating the deposition material  110  uniformly. Therefore, there is an advantage of obtaining a higher temperature using the present vaporization boat than using a conventional vaporization boat.  
      The heated deposition material  110  is vaporized, and deposited on a substrate loaded in the evaporator after passing through the plurality of openings  106  that are patterned to be parallel. The vaporized deposition material  110  that has passed through the openings  106  travels in vertical direction without dispersion.  
       FIG. 5  is a perspective view for describing a deposition method by moving a substrate within the evaporator using a vaporization boat that includes a patterned cover unit having line shaped openings, according to an embodiment of the present invention.  
      Referring to  FIG. 5 , a method of depositing a thin film on a substrate using a vaporization boat having a patterned cover unit will be described as below. First, after loading a deposition material in a loading section of a vaporization boat  220 , the loading section is covered with a cover unit  204 . Then, a substrate  214  is loaded into a vacuum chamber  200   a  of an evaporator  200 . At this time, the loaded substrate  214  is located at a distance from the vaporization boat  220 .  
      Next, when applying a current to the main body  202  of the vaporization boat  220  and the patterned cover unit  204 , the deposition material is vaporized. The deposition material vaporized passes through a plurality of line shaped openings  206  of the patterned cover unit  204 . Then, the vaporized deposition material is deposited on the surface of the substrate  214  by moving the substrate  214  in a direction from B 1  to B 2 . A direction from A 1  to A 2  indicates a length direction of the plurality of line shaped openings  206  formed on the patterned cover unit  204 , and the direction from B 1  to B 2  indicates a vertical direction of the plurality of line shaped openings  206  formed on the patterned cover unit  204 .  
      Next, when the substrate  214  has passed the vaporization boat  220  in the direction from B 1  to B 2 , the substrate  214  is turned 90° and then deposition is performed repeatedly for a predetermined period of time by moving the substrate  214 .  
      According to an aspect of the present invention, to form a thin film on a substrate  214 , the deposition is performed repeatedly while moving the substrate  214  in the directions A 1 -A 2  and B 1 -B 2  alternately in the evaporator  200 .  
      Also, the deposition is performed by moving the substrate  214  in the direction from B 1  to B 2  and from B 2  to B 1  back and forth in the evaporator  200 .  
      The depositing time of the substrate  214  in the evaporator  200  by moving the substrate  214  from B 1  to B 2  and from B 2  to B 1  is equal.  
      In the embodiment of the present invention, a patterned cover unit is used to form a patterned deposition source unit, however, it is seen that a patterned deposition source unit can be formed by patterning the deposition material itself.  
      A method of depositing a thin film by rotating a substrate while moving back and forth is mainly described in the present embodiment. However, the deposition method can be modified to move the vaporization boat back and forth in first and second directions perpendicular to the line direction of the patterned deposition source unit, in which the substrate direction of the first direction is 90° difference from the substrate direction of the second direction.  
      The size of the vacuum chamber of the evaporator according to the present invention can be remarkably reduced by decreasing the distance between the deposition source unit and the substrate.  
      The deposition method according to the embodiment of the present invention is a method of depositing a thin film by moving a substrate over a vaporization boat having a patterned cover unit, and directions of the substrate when moving back and forth have 90° difference, thereby improving overall uniformity of a thin film.  
      Also, according to deposition method of the present invention, due to a reduced distance between the deposition source unit and the substrate and due to a directionality of vapor atoms, vapor atom flux per unit area is increases. Therefore, the thin film can be deposited in high density.  
      According to the present invention, since not only the main body of the vaporization boat, but also the patterned cover unit can act as a heating source, this method can easily be applied to deposit a source material having a high melting point.  
      While this invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled 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.