Abstract:
A vacuum apparatus of an ion implantation system having an ion generator includes a vacuum pump evacuating the interior of the ion generator, a vacuum line connected between the vacuum pump and the ion generator, at least one first type valve connected to the ion generator and the vacuum line for injecting an inert gas into the ion generator and the vacuum line to equalize internal and external pressures of the ion generator and the vacuum line and to remove the air from the interior of the ion generator and the vacuum line, so that oxygen does not react with an inflammable impurity inside the ion generator, and at least one second type valve connected to the ion generator for being closed or opened to maintain a pressure of the ion generator to a predetermined vacuum level.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to an ion implantation system. More particularly, the present invention relates to a vacuum apparatus of an ion implantation system that can safely evacuate an interior of an ion generator.  
           [0003]    2. Description of the Related Art  
           [0004]    An ion implantation system includes an ion generator and a vacuum apparatus. The ion generator includes an ion source and a charge converter. The ion generator generates a cation beam when a high electric field is applied to the ion source and a gas, such as BF 3 , PH 3  and AsH 3 , flows thereinto. The charge converter is filled with a vapor that is produced when magnesium is heated and then sublimated, and converts the cation beam generated by the ion source into an anion beam. While passing through the charge converter, the cation beam interacts with the magnesium vapor and receives electrons to be converted into an anion beam. The ion generator operates in a vacuum atmosphere and thus requires a vacuum apparatus to maintain a vacuum atmosphere inside the ion generator.  
           [0005]    While evacuating the air from the ion generator in order to obtain a low vacuum pressure inside the ion generator, the vacuum line of the vacuum apparatus is contaminated by inflammable impurities such as phosphorous, hydrogen and magnesium. Therefore, a need exists for cleaning the interior of the ion generator and replacing damaged parts.  
           [0006]    In order to clean the interior of the ion generator and replace damaged parts, the ion generator must be opened. After cleaning the interior of the ion generator or replacing the damaged parts, the ion generator is reassembled.  
           [0007]    While the ion generator is opened, however, oxygen flows into the ion generator and the vacuum line. After reassembly, when the vacuum apparatus performs a pumping operation in order to maintain a vacuum atmosphere inside the ion generator, oxygen present in the ion generator and the vacuum line may react with inflammable impurities deposited in the vacuum line and may cause an explosion.  
         SUMMARY OF THE INVENTION  
         [0008]    To overcome the problems described above, preferred embodiments of the present invention provide a vacuum apparatus that may safely evacuate the interior of an ion generator and the vacuum line.  
           [0009]    It is another feature of an embodiment of the present invention to provide a method of safely evacuating an ion generator and vacuum line.  
           [0010]    The preferred embodiments of the present invention provide a vacuum apparatus of an ion implantation system having an ion generator. The vacuum apparatus includes a vacuum pump for evacuating the interior of the ion generator, a vacuum line connected between the vacuum pump and the ion generator, at least one first type valve connected to the ion generator and the vacuum line for injecting an inert gas into the ion generator and the vacuum line to equalize internal and external pressures of the ion generator and the vacuum line and also to remove the air from the interior of the ion generator and the vacuum line, so that oxygen does not react with an inflammable impurity inside the ion generator and the vacuum line, and at least one second type valve connected to the ion generator for being closed or opened to maintain the pressure of the ion generator to a predetermined vacuum level.  
           [0011]    Preferably, the first type valve is a solenoid valve. Also preferably, the inert gas is an argon gas or a nitrogen gas. The inflammable impurity includes phosphorous, hydrogen and magnesium. The vacuum pump preferably includes a turbo pump and a roughing pump. Regarding the at least one first type valve, one valve is directly connected to the ion generator, and others may be arranged at locations adjacent to the vacuum pump. Regarding the at least one second type valve, one valve is directly connected to the ion generator, and others may be arranged at locations adjacent to the vacuum pump.  
           [0012]    A preferred embodiment of the present invention further provides an evacuation method in an ion implantation system including an ion generator and a vacuum apparatus including a vacuum line. The method includes injecting an inert gas into an interior of the ion generator and the vacuum line to equalize internal and external pressures of the ion generator and the vacuum line; opening the ion generator to clean the inside thereof or to replace a damaged part; closing the ion generator; and injecting the inert gas into the interior of the ion generator and the vacuum line to remove the air from the interior of the ion generator and the vacuum line, so that oxygen does not react with an inflammable impurity inside the ion generator and the vacuum line. In this evacuation method the inert gas may be an argon gas or a nitrogen gas and the inflammable impurity may include phosphorus, hydrogen, and magnesium.  
           [0013]    These and other features of the present invention will be readily apparent to those of ordinary skill in the art upon review of the detailed description that follows. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]    For a more complete understanding of the present invention and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which like reference numerals denote like elements throughout, and in which:  
         [0015]    [0015]FIG. 1 is a schematic diagram illustrating a conventional ion implantation system according to the prior art;  
         [0016]    [0016]FIG. 2 is a flow chart illustrating a conventional process of cleaning an ion generator and replacing a damaged part of the ion generator according to the prior art;  
         [0017]    [0017]FIG. 3 is a schematic diagram illustrating an ion implantation system according to a preferred embodiment of the present invention; and  
         [0018]    [0018]FIG. 4 is a flow chart illustrating a method of safely evacuating an ion generator according to a preferred embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0019]    Korean Patent Application No. 2001-8175, filed on Feb. 19, 2001, and entitled: “Vacuum Apparatus of Ion Implantation System and Vacuumizing Method,” is incorporated by reference herein in its entirety.  
         [0020]    Detailed reference will now be made to preferred embodiments of the present invention, an example of which is illustrated in FIGS. 3 and 4 of the accompanying drawings.  
         [0021]    Turning now to FIG. 1, a conventional ion implantation system includes an ion generator  100  and a vacuum apparatus  200 . The ion generator  100  includes an arc chamber  10 , a filament  11 , an arc voltage source  12 , a filament heating source  13 , a suppress electrode  14 , a plug electrode  16 , a charge converter  20 , a vapor container  22 , magnesium  24 , and a heater  26 . The vacuum apparatus  200  includes a turbo pump  40 , a roughing pump  42 , a vent valve  44 , a roughing valve  46 , and a relief valve  48 .  
         [0022]    The charge converter  20  communicates with the vapor container  22 , and the vapor container  22  is filled with vapors that are produced when magnesium is heated by the heater  26  and then sublimated. The vent valve  44  and the roughing valve  46  are solenoid valves that operate in response to control signals C 1  and C 2  generated from a controller (not shown).  
         [0023]    Operation of the ion implantation system of FIG. 1 is as follows. The interior of the ion generator  100  is evacuated by the vacuum apparatus  200 . The arc voltage  12  is applied to the interior of the ion generator  100 , a heater operates, and a gas, such as BF 3 , PH 3  and AsH 3 , is injected into the interior of the arc chamber  10 . The arc chamber  10  and the filament  11  are heated by the filament heating source  13  and activate an injected ion gas to generate a cation beam  18 . The suppress electrode  14  and the plug electrode  16  converge the cation beam  18  to enter the charge converter  20 . The charge converter  20  converts the cation beam  18  into an anion beam  28 . More particularly, the cation beam  18  interacts with the magnesium vapor and receives electrons, and is then converted into an anion beam  28 .  
         [0024]    The vacuum apparatus  200  maintains a vacuum atmosphere inside the ion generator  100  while the ion generator  100  performs an operation to generate the anion beam  28 . That is, during an operation of the ion generator  100  to generate the anion beam  28 , the turbo pump  40  and the roughing pump  42  are turned on, the roughing valve  46  is opened in response to the control signal C 2 , so that a vacuum atmosphere is maintained inside the ion generator  100 . The relief valve  48  is closed when the vacuum line is at a predetermined atmospheric pressure, and is automatically opened to maintain the interior of the ion generator  100  at the predetermined pressure when the pressure of the vacuum line becomes greater than the predetermined pressure.  
         [0025]    [0025]FIG. 2 is a flow chart illustrating a conventional process of cleaning the ion generator and replacing a damaged part of the ion generator according to the prior art.  
         [0026]    The turbo pump  40  and the roughing pump  42  are turned off, and the roughing valve  46  is closed in response to the control signal C 2 . Then, the ion generator is opened to clean the interior of the ion generator  100  and replace any damaged parts. However, to open the ion generator, it is required that the pressure inside the ion generator be equal to atmospheric pressure. Therefore, vent valve  44  is opened in response to the control signal C 1 , and argon (Ar) gas is injected into both the interior of the ion generator  100  and the vacuum line of the vacuum apparatus  200  (step  300 ).  
         [0027]    When the pressure inside the ion generator is equal to atmospheric pressure, vent valve  44  is closed in response to the control signal C 1 .  
         [0028]    Thereafter, the ion generator  100  is opened, and the inside ambient state of the ion generator  100  becomes an atmospheric state. The interior of the ion generator  100  is cleaned and any damaged parts are replaced before the ion generator  100  is reassembled (step  310 ).  
         [0029]    The turbo pump  40  and the roughing pump  42  are then turned on, and the roughing valve  46  is opened in response to the control signal C 2 . Thereafter, an ion generating operation of the ion generator  100  and a vacuum producing operation of the vacuum apparatus  200  are repeatedly performed (step  320 ). It is difficult, however, to completely clean all parts inside the ion generator  100 . Accordingly, some inflammable impurities remain inside the ion generator  100 .  
         [0030]    In addition, as described above, during the cleaning of the interior of the ion generator  100  and the replacing of any damaged parts, oxygen flows into the ion generator and the vacuum line. When the roughing valve  46  is opened and the roughing pump  42  performs the pumping operation at the beginning stage to evacuate the interior of the ion generator, oxygen rapidly flows through the vacuum line, whereby oxygen reacts with the remaining inflammable impurities like phosphorus, hydrogen, and magnesium and may cause an explosion.  
         [0031]    [0031]FIG. 3 shows an ion implantation system according to a preferred embodiment of the present invention. The ion generator  100  of FIG. 3 is similar to that of FIG. 1, and the vacuum apparatus of FIG. 3 is similar to that of FIG. 1 except for the additional vent valves  50  and  52  and a relief valve  54 . Like reference numerals of FIGS. 1 and 3 denote like elements.  
         [0032]    Similar to vent valve  44 , vent valves  50  and  52  are preferably solenoid valves that operate in response to the control signal C 1 . Vent valve  50  and relief valve  54  control the pressure inside the ion generator  100 , and the vent valve  52  controls the pressure inside the vacuum line. Vent valves  44 ,  50  and  52  are opened to inject argon gas into the interior of the ion generator  100  and the vacuum line of the vacuum apparatus  200 ′ to equalize the pressure inside the ion generator to atmospheric pressure and to rapidly remove oxygen from the inside of the ion generator  100  and the vacuum line of the vacuum apparatus  200 ′. This will be explained below in detail.  
         [0033]    [0033]FIG. 4 is a flow chart illustrating a method of safely evacuating the ion generator  100  according to a preferred embodiment of the present invention.  
         [0034]    The turbo pump  40  and the roughing pump  42  are turned off, and the roughing valve  46  is closed in response to the control signal C 2 . Vent valves  44 ,  50  and  52  are then opened in response to the control signal C 1  to inject argon gas into the interior of the ion generator  100  and the vacuum line of the vacuum apparatus  200 ′ to equalize the pressure inside the ion generator to atmospheric pressure. When the pressure inside the ion generator is equal to atmosphere pressure, vent valves  44 ,  50  and  52  are closed in response to the control signal C 1 , and the ion generator is opened, so that the inside ambient state of the ion generator  100  becomes an atmospheric state (step  400 ).  
         [0035]    Thereafter, the ion generator  100  is cleaned, and any damaged parts are replaced before reassembling the ion generator  100  (step  410 ). Argon gas is injected into the interior of the ion generator  100  and the vacuum line of the vacuum apparatus  200 ′ through vent valves  44 ,  50  and  52  to rapidly remove oxygen from the interior of the ion generator and the vacuum line through the relief valves  54  and  48 , respectively (step  420 ).  
         [0036]    Vent valves  44 ,  50  and  52  are then closed in response to the control signal C 1 , and the turbo pump  40  and the roughing pump  42  are turned on to pump the argon gas. The roughing valve  46  is opened, and then an ion generating operation of the ion generator  100  and a vacuum operation of the vacuum apparatus  200 ′ are repeatedly performed (step  430 ).  
         [0037]    In step  430 , even though the roughing valve  46  is opened and the pumping operation is performed by the roughing pump  42 , since the interior of the ion generator  100  and the vacuum line of the vacuum apparatus  200 ′ are filled with an inert gas, i.e., argon gas or nitrogen gas, the inert gas does not react with the inflammable impurities, so that an explosion does not occur, thereby leading to a safe operation.  
         [0038]    In a preferred embodiment of the present invention, in order to prevent an explosion from occurring due to a reaction of oxygen and an inflammable impurity, argon gas is injected through the three vent valves  44 ,  50  and  52 . In the alternative, argon gas may be injected through only vent valve  44 . That is, a method of safely evacuating the ion generator may be performed in the vacuum apparatus of FIG. 1, however, the speed at which oxygen is evacuated in that case is significantly slower than in the present invention.  
         [0039]    As previously described herein, since oxygen present inside the ion generator  100  and the vacuum apparatus  200 ′ is completely evacuated before the pumping operation is performed by the roughing pump  42  an explosion due to a reaction of oxygen and an inflammable gas no longer occurs, thereby resulting in a safe operation. Typical inflammable impurities include phosphorus, hydrogen, and magnesium.  
         [0040]    Preferred embodiments of the present invention have been disclosed herein and, although specific terms are employed, they are used in a generic and descriptive sense only and not for purpose of limitation. Accordingly, it will be understood by those of ordinary skill in the art that various changes in form and details may be made without departing from the spirit and scope of the invention as set forth in the following claims.