Abstract:
An ion beam extractor controls a direction and an intensity of ion beams by adjusting a voltage applied to a grid having slits formed therein, thereby enhancing uniformity of an etching rate of a wafer, leading to an increase of productivity of semiconductor diodes. The ion beam extractor comprises an ion source to produce an ion beam and at least one grid located at a rear end of the ion source in a progressing path of the ion beam produced by the ion source to adjust a direction of the ion beam by controlling a voltage applied to the at least one grid.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of Korean Patent Application No. 2005-1719, filed on Jan. 7, 2005 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 general inventive concept relates to generation of ion beams of a semiconductor neutral beam etcher, and more particularly, to an ion beam extractor that controls a direction and an intensity of ion beams by adjusting a voltage applied to a grid having slits formed therein. 
     2. Description of the Related Art 
     Recently, according to increasing requirements for integration of semiconductor diodes, a design rule for semiconductor integration circuits has been reduced, requiring a critical dimension of 0.25 um (micrometers) or less. Etchers for ion reinforcement, such as a high-density plasma etcher, a reactive ion etcher, and the like, are typically used to realize this critical dimension of the semiconductor diodes. 
     In a semiconductor fabrication process, a grid for generation of high ion flux is used to process a wafer with ion beams or neutral beams. 
       FIGS. 1 and 2  illustrate a neutral beam chamber having a conventional grid  3 . As illustrated in  FIGS. 1 and 2 , the grid  3  used for neutral beam etching has a plurality of circular holes  5  through which ion beams produced by an ion source  1  (plasma) pass to cover an entire surface of a wafer  9 . The diameter of each hole is about 3˜6 mm (millimeters). 
     The grid  3  is located at a rear end of an ion source  1  on a path of the ion beams to accelerate the ion beams using an electric field generated by application of a voltage thereto. At the same time, the grid  3  adjusts energy of the ion beams by focusing the ion beams using the plurality of holes  5  through which the ion beams pass. 
     A reflector  7  is spaced slightly apart from the rear end of the grid  3  and reflects the ion beams incident thereto and transforms the reflected ion beams into neutral beams. The reflector  7  is slightly slanted with respect to the wafer  9  (at an angle of about 5˜9°) in order to allow efficient etching for a wall of the wafer  9 . 
     When the ion beams generated by the ion source  1  pass through the grid  3 , the conventional grid  3  extracts the ion beams passing through the grid  3  and focuses the extracted ion beams to generate the neutral beams, which are used for etching an object film on the wafer  9  of a semiconductor substrate. 
     An ion flux is influenced by a density of plasma, a shape of the grid  3 , a thickness of the grid  3 , a size of the grid  3 , and the electric field created by applying the voltage to the grid  3 . Furthermore, since the grid  3  has the plurality of holes  5 , the wafer  9  is typically rotated in order to enhance a uniformity of an etching rate for the wafer  9 . 
     As described above, since the plurality of holes  5  for generating the neutral beams are arranged on an area of the grid  3  corresponding to an area of the wafer  9 , and allow the ion beams to pass therethrough, resulting in an ion beam extraction area below 20˜30% of the entire area of a plate on which the wafer  9  is positioned, it becomes necessary to increase the density of the plasma or the electric field. 
     When increasing the density of the plasma, there is a problem in that a direction of the ion beams is difficult to control by adjusting the electric field due to the fact that the neutral beam chamber typically comprises two or three electrodes in the grid  3 . 
     Additionally, since the wafer  9  is rotated to enhance the uniformity of the etching rate, there is a problem in that an angle of the ion source  1  must be changed in order to change an angle of the ion beams. 
     SUMMARY OF THE INVENTION 
     The present general inventive concept provides an ion beam extractor to extract a rectangular ion beam using a grid having slits formed therein, thereby increasing an ion beam extraction area and producing a high ion flux. 
     The present general inventive concept also provides the ion beam extractor having a plurality of stacked grids, each having slits formed therein, such that a direction of the ion beam is adjusted by controlling a voltage applied to each of the plurality of stacked grids. 
     The present general inventive concept also provides the ion beam extractor to control the direction of the ion beam by application of the voltage thereto, thereby allowing application of the ion beam extractor to various processes without modification of hardware components. 
     The present general inventive concept also provides the ion beam extractor to control the direction and an intensity of the ion beam, thereby securing uniformity of a film while enhancing uniformity of an etching rate of a wafer, thereby increasing productivity of semiconductor diodes. 
     Additional aspects and/or advantages of the general inventive concept will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the general inventive concept. 
     The foregoing and/or other aspects and advantages of the present general inventive concept are achieved by providing an ion beam extractor, comprising an ion source to produce an ion beam from a plasma, and at least one grid located at a rear end of the ion source in a progressing path of the ion beam produced by the ion source to adjust a direction of the ion beam by controlling a voltage applied to the at least one grid. 
     The at least one grid may comprise a plurality of plates to which different voltages are applied, respectively. 
     The plurality of plates may be arranged to correspond with respect to each other such that at least one slit through which the ion beam passes is formed between each pair of corresponding plates. 
     The at least one grid may be formed with at least one slit through which the ion beam passes. 
     The at least one slit may comprise a plurality of slits to extract a rectangular ion beam. 
     The at least one grid may comprise a plurality of grids stacked below the rear end of the ion source, each of the plurality of grids having the at least one slit formed therein, thereby allowing voltages that are applied to the respective grids to be controlled to adjust the direction of the ion beam. The at least one slit in each of the plurality of grids may have respective centers offset with respect to one another. 
     The ion beam extractor may further comprise a reflector located in parallel with a wafer at the same angle with respect to the wafer as that of the ion source to reflect the ion beam that passes through the grid toward the wafer and to transform the reflected ion beam into a neutral beam. 
     The foregoing and/or other aspects and advantages of the present general inventive concept are also achieved by providing an ion beam extractor, comprising an ion source to produce an ion beam from a plasma, and a plurality of grids located at a rear end of the ion source in a progressing path of the ion beam produced by the ion source to adjust a direction of the ion beam by controlling one or more voltages applied to the plurality of grids. 
     The plurality of grids may be a plurality of grids stacked below the rear end of the ion source, each of the plurality of grids having a slit formed therein to allow the ion beam to pass therethrough. 
     Each of the plurality of grids may comprise a plurality of plates, and different voltages may be applied to the respective grids to adjust the direction of the ion beam. 
     Different voltages are applied to the plurality of grids, respectively, such that the direction of the ion beam is adjusted according to a magnitude of the different applied voltages. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and/or other aspects and advantages of the general inventive concept will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings, of which: 
         FIG. 1  is a schematic structural view illustrating a conventional neutral beam chamber; 
         FIG. 2  is a plan view illustrating a conventional grid of the neutral beam chamber of  FIG. 1 ; 
         FIG. 3  is a schematic structural view illustrating a neutral beam chamber according to the present general inventive concept; 
         FIG. 4  is a plan view illustrating a grid according to an embodiment of the present general inventive concept; 
         FIG. 5  is a plan view illustrating a grid according to another embodiment of the present general inventive concept; 
         FIG. 6A  is a view illustrating a shape of a slit formed in the grid of  FIG. 5  according to an embodiment of the present general inventive concept; 
         FIG. 6B  is a view illustrating another shape of a slit formed in the grid of  FIG. 5  according to another embodiment of the present general inventive concept; 
         FIG. 7  is a schematic structural view illustrating an ion beam extractor according to an embodiment of the present general inventive concept; 
         FIG. 8  is a schematic structural view illustrating an ion beam extractor according to another embodiment of the present general inventive concept; and 
         FIG. 9  is a view illustrating a schematic structure of an ion beam extractor according to another embodiment of the present general inventive concept, and a result of a simulation of the ion beam extractor. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Reference will now be made in detail to the embodiments of the present general inventive concept, examples of which are illustrated in the accompanying drawings. The embodiments are described below to explain the present general inventive concept by referring to the figures. 
       FIG. 3  is a schematic structural view illustrating a neutral beam chamber according to an embodiment of the present general inventive concept. 
     Referring to  FIG. 3 , the neutral beam chamber includes an ion source  10  to produce ion beams, a grid  20  located at a rear end of the ion source  10 , a reflector  30  located at a rear end of the grid  20 , and a wafer  40  located at a rear end of the reflector  30 . After the ion beams produced by the ion source  10  pass through a plurality of slits  20   a  ( FIG. 4 ) formed in the grid  20 , the ion beams are reflected by the reflector  30  and are transformed into neutral beams. The neutral beams are then incident on the wafer  40  to etch an object film on the wafer  40 . 
     The ion source  10  generates the ion beams from various reactant gases. The ion source  10  may comprise a plasma generating apparatus that generates plasma by application of high frequency energy. Alternatively, other types of ion sources may also be used. 
     The grid  20  is coupled to the rear end of the ion source  10  to accelerate the ion beams by application of a voltage while the ion beams pass through the plurality of slits  20   a  formed in the grid  20 . The grid  20  may have various shapes, which will be described hereinafter with reference to  FIGS. 4 to 6 . 
     The reflector  30  is located slightly apart from the grid  20  to reflect the ion beams incident thereto and to transform the reflected ion beams into the neutral beams. The reflector  30  is arranged parallel with the wafer  40 , and may be slanted at the same angle as that of the ion source  10 . 
       FIG. 4  is a plan view illustrating a grid according to an embodiment of the general inventive concept. 
     Referring to  FIGS. 3 and 4 , the grid  20  of the general inventive concept has the plurality of slits  20   a , each having a predetermined diameter. The grid  20  increases an ion beam extraction area to 50% or more of an entire area of a plate on which the wafer  40  is positioned by extracting rectangular ion beams from the ion beams passing through the plurality of slits  20   a , thereby increasing an ion density in comparison to the conventional grid of  FIGS. 1 and 2 , which has an ion beam extraction area of 20˜30% of the entire area of the plate. 
     Accordingly, since the ion density can be increased to generate a high ion flux without by increasing an output of the ion source  10  (e.g., by increasing the plasma density), the flux of the ion beams can be easily controlled. 
       FIG. 5  is a plan view illustrating a grid according to another embodiment of the general inventive concept. 
     Referring to  FIGS. 3 and 5 , the grid consists of two grids including a first grid  21  and a second grid  22  arranged to correspond to each other in an engaging state such that a plurality of slits  21   a  are formed therebetween. The first and second grids  21  and  22  comprise a first electrode member  21   b  and a second electrode  22   b , respectively. The first and second electrode members  21   b  and  22   b  have a semi-circular arc shape. The first and second grids  21  and  22  further comprise a first plurality of bars  21   c  and a second plurality of bars  22   c , respectively, which define a circle with the entire outer peripheral ends of the first and second plurality of bars  21   c  and  22   c . Accordingly, the first and second plurality of bars  21   c  and  22   c  are matched with each other, thereby forming the plurality of slits  21   a  having a rectangular shape. 
     Isolators  50  are located at both sides between the semi-circular arc-shaped first and second electrode members  21   b  and  22   b . A first voltage V (not shown) and a second voltage V′ (not shown) are applied to the first grid  21  and the second grid  22 , respectively. The first and second voltages V and V′ may be different from each other or the first and second voltages V and V′ may be equal. 
     As a result, a direction of the ion beams can be controlled by applying the first voltage V to the first grid  21  while applying the second voltage V′ to the second grid  22 , thereby enhancing an etching rate uniformity and a wafer etching depth uniformity. 
       FIG. 6A  is a view illustrating a shape of a slit formed in the grid of  FIG. 5  according to an embodiment of the present general inventive concept, and  FIG. 6B  is a view illustrating another shape of a slit formed in the grid of  FIG. 5  according to another embodiment of the present general inventive concept. 
       FIGS. 6A and 6B  illustrate the shapes of the slit  21   a  formed between the first and second grids  21  and  22  of  FIG. 5 , in which various modifications of the first and second plurality of bars  21   c  and  22   c  are formed between the first and second electrode members  21   b  and  22   b , respectively. 
       FIG. 7  is a schematic structural view illustrating an ion beam extractor according to an embodiment of the present general inventive concept. 
     In  FIG. 7 , the ion beam extractor comprises a first grid  61  located at a rear end of an ion source  10  to which a first voltage V 1  is applied, a second grid  62  located at a rear end of the first grid  61  to which a second voltage V 2  is applied, a third grid  63  located at a rear end of one side of the second grid  62  to which a third voltage V 3  is applied, and a fourth grid  64  located at a rear end of the other side of the second grid  62  to which a fourth voltage V 4  is applied, and a fifth grid  65  located at a rear end of the third and fourth grids  63  and  64  to which a fifth voltage V 5  is applied, and the third and fourth grids  63  and  64  face each other. The number of stacked grids  61  to  65  may be increased or decreased. For example, a sixth grid  66  may be added to the grids  61  to  65 , and may be located at a rear end of the fifth grid  65 . 
     Each of the plurality of grids  61  to  65  is formed with a plurality of slits  61   a ,  62   a ,  63   a  and  65   a , through which the ion beams are transmitted to the reflector  30  and the wafer  40  of  FIG. 3 . 
     After stacking a plurality of various grids, such as the plurality of grids  61  to  65  of  FIG. 7 , different voltages can be applied to the plurality of grids, respectively, to control the direction of the ion beams passing through the plurality of slits  61   a ,  62   a ,  63   a  and  65   a.    
       FIG. 8  is a schematic structural view illustrating an ion beam extractor according to another embodiment of the present general inventive concept. 
     In  FIG. 8 , the ion beam extractor comprises a first grid  71  located at a rear end of an ion source  10  to which a first voltage V 1  is applied, a second grid  72  located at a rear end of the first grid  71  to which a second voltage V 2  is applied, a third grid  73  located at a rear end of one side of the second grid  72  to which a third voltage V 3  is applied, and a fourth grid  74  located at a rear end of the other side of the second grid  72  to which a fourth voltage V 4  is applied, and a fifth grid  75  located at a rear end of the third and fourth grids  73  and  74  to which a fifth voltage V 5  is applied, and the third grid  73  is diagonally symmetrical to the fourth grid  74 . 
     As such, in a structure having a plurality of various grids, such as the plurality of grids  71  to  75  illustrated in  FIG. 8 , the plurality of slits  71   a  to  75   a  can have respective centers offset with respect to one another. Additionally, the plurality of slits  71   a  to  75   a  can have diameters that vary with respect to each other. 
     In this structure, voltages applied to the respective grids  71  to  75  can be different from each other, and a direction of the ion beams can be adjusted by controlling the voltages applied to the respective grids  71  to  75 . 
       FIG. 9  is a view illustrating an ion beam extractor according to another embodiment of the present general inventive concept, and a result of a simulation using the ion beam extractor. 
     Similar to the ion beam extractor illustrated in  FIG. 8 , the ion beam extractor according to the present embodiment of the general inventive concept also includes the plurality of grids  71  to  75 , stacked in numerical order from top to bottom, and having the plurality of slits  71   a  to  75   a  illustrated in  FIG. 8 , respectively. The ion beam extractor according to the present embodiment has an arrangement of the slits  71   a  of the first grid  71  to which the first voltage V 1  is applied that is different from that of the embodiment of  FIG. 8 . Thus, the arrangement of the plurality of slits  71   a  to  75   a  may be varied. 
     As with the plurality of slits illustrated in  FIG. 8 , the plurality of slits  71   a  to  75   a  of the plurality of grids  71  to  75  of  FIG. 9  have centers that are offset with respect to one another, and diameters that vary with respect to each other. 
     The offset type grids  71  to  75  are easily manufactured, and have a simple structure. 
     As apparent from the above description, an ion beam extractor of the general inventive concept allows rectangular ion beams to be extracted through a plurality of stacked grids, each having a plurality of slits, thereby increasing an ion beam extraction area and producing a high ion flux without increasing an output of the ion source (e.g., density of a plasma source). 
     Since a direction of the ion beam can be adjusted by controlling voltages applied to the plurality of stacked grids, each having the plurality of slits, there is no need to change an angle of the ion source and a reflector in order to change the direction of the ion beams, thereby allowing application of the ion beam extractor to various processes without modifications of hardware components. 
     The ion beam extractor can control the direction and an intensity of the ion beams, thereby securing a uniformity of a film to be etched while enhancing a uniformity of an etching rate for a wafer, thereby increasing a productivity of semiconductor diodes. 
     Although a few embodiments of the present general inventive concept have been shown and described, it would be appreciated by those skilled in the art that changes may be made in this embodiment without departing from the principles and spirit of the general inventive concept, the scope of which is defined in the claims and their equivalents.