Abstract:
A chemical mixing device includes a first supply line adapted to supply a first chemical solution, a second supply line adapted to supply a second chemical solution, a mixing vessel adapted to receive the first and second chemical solutions and to hold a mixing vessel chemical solution, a floating body disposed within the mixing vessel and adapted to rise to a level corresponding to a volume of the mixing vessel chemical solution; and a plurality of switches each adapted to provide a corresponding chemical solution supply measuring signal in response to the level of the floating body being equal to a corresponding fixed level, each of the fixed levels corresponding to a fixed volume of the mixing vessel chemical solution within the mixing vessel.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims priority under 35 U.S.C. §119 from Korean Patent Application 2003-78958, filed on Nov. 10, 2003, the contents of which are hereby incorporated by reference in their entirety for all purposes as if fully set forth herein. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Technical Field  
         [0003]     The present invention relates to the manufacturing of semiconductor devices, and more particularly, to a chemical mixing system for mixing chemical solutions used in the manufacturing the semiconductor devices.  
         [0004]     2. Description  
         [0005]     A semiconductor device manufacturing process generally contains a step of mixing H 2 O 2  or deionized water with two or more different kinds of chemical solutions in a predetermined ratio in a chemical supply device. The semiconductor device manufacturing process has become more complicated with higher integration causing changes in the process conditions, which means the mixing ratio of chemicals are continuously changed.  
         [0006]      FIG. 1  is a block diagram of a chemical mixing system for use in a semiconductor device manufacturing process according to the conventional art.  
         [0007]     Referring to  FIG. 1 , the configuration of the chemical mixing system is as follows.  
         [0008]     A measurement tank  10  stores a predetermined amount of first chemical solution A. A first level sensor  28  installed within measurement tank  10  measures a volume amount of a first chemical solution A. A first supply line  30  supplies measurement tank  10  with first chemical solution A. A first valve  14  installed in first supply line  30  opens or closes to supply or cut off, respectively, first chemical solution A. A first gas line  32  connected to measurement tank  10  supplies N2 gas to measurement tank  10 . A second valve  16  installed in first gas line  32  supplies or cuts off the N2 gas. A third valve  18 , installed in a first exhaust line  34 , discharges first chemical solution A stored in measurement tank  10 . A third supply line  38  supplies first chemical solution A stored in measurement tank  10  to a mixing vessel  12  when N2 gas is supplied.  
         [0009]     A second supply line  36  supplies a second chemical solution B to mixing vessel  12 . A fourth valve  20 , installed in a second supply line  36  opens or closes to supply or cut off, respectively, second chemical solution B. Mixing vessel  12  receives and mixes first and second chemical solutions A and B. A second gas line  40  is connected to mixing vessel  12  to supply N2 gas. A sixth valve  24 , installed in second gas line  40  supplies or cut offs the N2 gas to mixing vessel  12 . A seventh valve  26 , installed in a second exhaust line  42 , discharges mixed chemical solution from mixing vessel  12 . A fourth supply line  44 , installed below mixing vessel  12 , supplies the mixed chemical solution from mixing vessel  12 . A fifth valve  22 , installed in fourth supply line  44 , controls the supply of the mixed chemical solution from mixing vessel  12 .  
         [0010]     A controller  46  outputs first, second, third, fourth, fifth, sixth, and seventh valve control signals, and ensures that the chemical solution is mixed by a predetermined ratio and the mixed chemical solution is supplied to a process chamber (not shown). Herewith, the first valve control signal is a signal for supplying a fixed quantity (volume) of first chemical solution A to the measurement tank  10 . The fourth valve control signal is a signal for supplying a fixed quantity (volume) of second chemical solution B to mixing vessel  12 . The second valve control signal is a signal for purging first chemical solution A from measurement tank  10 . The third valve control signal is a signal for discharging first chemical solution A from measurement tank  10 . The sixth valve control signal is a signal for purging the mixed chemical solution from mixing vessel  12 . The seventh valve control signal is a signal for discharging the mixed chemical solution from mixing vessel  12 . The fifth valve control signal is a signal for supplying the mixed chemical solution from mixing vessel  12 .  
         [0011]     Beneficially, the first through seventh valves  14 ,  16 ,  18 ,  20 ,  22 ,  24 ,  26  are solenoid valves.  
         [0012]     First and second chemical solutions A and B are supplied through first and second supply lines  30 ,  36 , respectively. Controller  46  outputs the first and fourth valve control signals so as to open first and fourth valves  14 ,  20 , respectively, and to supply first chemical solution A to measurement tank  10  and supply second chemical solution B to mixing vessel  12 . At this time, first level sensor  28  measures a predetermined volume of first chemical solution A in measurement tank  10 , and second level sensor  29  measures a filled state when second chemical solution B supplied to the mixing vessel  12  is filled to a predetermined level therein. The installation position of first and second level sensors  28 ,  29  is varied by the desired mix ratio of the chemical solution. The level measurement signals of the first and second level sensors  28 ,  29  are provided to controller  46 .  
         [0013]     Controller  46  outputs the first valve control signal to close first valve  14  when first level sensor  28  senses a desired measurement tank  10  level. First valve  14  cuts off the supply of first chemical solution A supplied to measurement tank  10 . Accordingly, first chemical solution A is supplied in a predetermined amount by installing first level sensor  28  in measurement tank  10 . Additionally, a level sensor may be installed above first level sensor  28  so that controller  46  can sense whenever first chemical solution A is filled into measurement tank  10  above a predetermined volume. In that case, controller  46  outputs the third valve control signal to open third valve  18  and discharge from measurement tank  10  first chemical solution A, filled above the predetermined volume.  
         [0014]     Controller  46  outputs the fourth valve control signal to close fourth valve  20  when second level sensor  29  senses a desired level in mixing vessel  12 . Fourth valve  20  cuts off the supply of second chemical solution B into mixing vessel  12 . Accordingly, second chemical solution B is supplied in a predetermined volume by installing second level sensor  29  in mixing vessel  12 . Additionally, a level sensor may be installed above the second level sensor  29  so that controller  46  can sense whenever the second chemical solution B is filled into mixing vessel  12  above a predetermined volume. In that case, controller  46  outputs the seventh valve control signal to open seventh valve  26  and discharge from mixing vessel  12  second chemical solution B, filled above the predetermined volume.  
         [0015]     Controller  46  outputs the second valve control signal so as to open second valve  16  and supply N2 gas to first gas line  32 . The N2 gas is provided to measurement tank  10  through gas line  32  so that first chemical solution A in measurement tank  10  is supplied (discharged) to mixing vessel  12  through third supply line  38 .  
         [0016]     Controller  46  cuts off second valve  16  when first chemical solution A is all discharged to mixing vessel  12 . At that point, mixing vessel  12  has a mixed chemical solution of first chemical solution A and second chemical solution B. Subsequently, controller  46  outputs the fifth and sixth valve control signals to open fifth and sixth valves  22 ,  24 . When sixth valve  24  is opened N2 gas is supplied to sixth gas line  40  so that the mixed chemical solution is purged through fourth supply line  44 . The mixed chemical solution output through fourth supply line  44  is supplied to a process chamber (not shown) through fifth valve  22 .  
         [0017]     The chemical supply device or wet station employed in the conventional semiconductor manufacturing process must continuously change the mixed chemical conditions, such as the type of chemicals, concentration, etc. as the process conditions change. It is difficult to meet the constant change in requirements because the chemical supply device, or wet station, mixes chemicals by using a level sensor or metering pump. Thus, the structure and program of the mixing device must be changed according to a change in chemicals and their mixing ratio. Furthermore, a complicated procedure is required in order to check whether or not the mixing operation is performed by an exact ratio whenever the mixing ratio is changed, which requires a lot of time.  
         [0018]     The chemical mixing device according to the conventional art as shown in  FIG. 1  requires a specific measurement tank in order to mix several different kinds of chemicals, which requires large complicated structures taking up a lot installation space.  
         [0019]     Furthermore, the life span of a level sensor for measuring the chemical solution is limited, and an error in the chemical mixture may be caused by a breakdown of the level sensor. The chemical mixing device requires the use of a meter, such as a precise densitometer, to measure the mixing ratio. But this type of meter is not suitable for measuring a mixture of three more different chemicals that are necessary for a highly integrated semiconductor device manufacturing process. That is, it is difficult to accurately measure the mix ratio.  
         [0020]     Accordingly, it would be desirable to provide a chemical mixing system capable of accurately measuring chemicals. It would also be desirable to provide such a system which can prevent mixing errors of chemicals caused by sensor defects. It would further be desirable to provide a system which requires less installation space.  
       SUMMARY OF THE INVENTION  
       [0021]     According to one aspect of the invention, a chemical mixing device includes a first supply line adapted to supply a first chemical solution; a second supply line adapted to supply a second chemical solution; a mixing vessel adapted to receive the first and second chemical solutions from the first and second supply lines and to hold a mixing vessel chemical solution comprising one or more of the first and second chemical solutions; a floating body disposed within the mixing vessel and adapted to rise to a level corresponding to a volume of the mixing vessel chemical solution within the mixing vessel; and a plurality of switches each adapted to provide a corresponding chemical solution supply measuring signal in response to the level of the floating body being equal to a corresponding fixed level, each of the fixed levels corresponding to a fixed volume of the mixing vessel chemical solution within the mixing vessel.  
         [0022]     Beneficially, the device also includes supply valves installed individually in the supply lines which are opened or closed so as to respectively supply or cut off supply of different chemical solutions in response to a valve control signal. The mixing vessel receives and mixes the different type of chemical solutions supplied through supply lines. The mixing vessel supplies mixed chemical solution from the mixing vessel to the process chamber via a mixed-chemical supply line which is beneficially installed below the mixing vessel. Beneficially, a mixed-chemical supply valve is installed in the mixed-chemical supply line and supplies the mixed chemical solution in response to valve control signal. Beneficially, a measurement rod is fixed to floating body, and moves vertically in order to measure a quantity of the chemical solutions supplied to the mixing vessel. The switches are sequentially switched by the vertical movement of measurement rod, to thus output the chemical solution supply measurement signals. Also beneficially, a controller receives the chemical supply measurement signals from the switches in conformity with a predetermined mixing ratio of the chemical solutions, and outputs valve control signals for individually supplying different kinds of chemical solutions by a fixed quantity and a valve control signal for supplying the mixed chemical solution to the process chamber.  
         [0023]     Beneficially, the chemical mixing device further includes a measurement rod fixing part for fixing the measurement rod and simultaneously moving the measurement rod horizontally, and then lowering it so as not to contact with switches, when the solution mixed within the mixing vessel is supplied to the process chamber.  
         [0024]     Beneficially, the chemical mixing device further includes at least two flow meters for respectively indicating a supply quantity of the different kinds of chemical solutions supplied through the at least two supply lines.  
         [0025]     According to another aspect of the invention, A method of mixing chemical solutions comprises: supplying a first chemical solution to a mixing vessel; stopping supplying the first chemical solution to the mixing vessel in response to a floating body within the mixing vessel rising to a first fixed level; supplying a second chemical solution to the mixing vessel in response to the floating body within the mixing vessel rising to the first fixed level; and stopping supplying the second chemical solution to the mixing vessel in response to the floating body within the mixing vessel rising to a second fixed level.  
         [0026]     Another to yet another aspect of the invention, a chemical solution mixing system comprises: a plurality of supply lines each adapted to supply a corresponding supplied chemical solution; a mixing vessel adapted to receive the supplied chemical solutions from the plurality of supply lines and to hold a mixing vessel chemical solution comprising one or more of the supplied chemical solutions; and a plurality of switches each adapted to provide a corresponding chemical solution supply measuring signal in response to a volume of the mixing vessel chemical solution within the mixing vessel reaching a corresponding fixed level. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0027]     The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and wherein:  
         [0028]      FIG. 1  is a block diagram of a chemical mixing system for use in a semiconductor manufacturing process according to the prior art; and  
         [0029]      FIG. 2  is a block diagram of one embodiment of a chemical mixing system according to one or more aspects of the invention. 
     
    
     DETAILED DESCRIPTION  
       [0030]     Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to  FIG. 2 . It will be understood by those skilled in the art that the present invention can be embodied by numerous different ways and is not limited to the following described embodiments. The following various embodiments are exemplary in nature. For purposes of brevity, a detailed description of known functions and systems has been omitted.  
         [0031]      FIG. 2  is a block diagram of chemical mixing system. The chemical mixing system has the following configuration.  
         [0032]     A first supply line  102  supplies a first chemical solution A. A first (supply) valve  106 , installed in first supply line  102 , opens or closes to supply or cut off, respectively, first chemical solution A in response to a first valve control signal.  
         [0033]     A second supply line  104  supplies a second chemical solution B. A second (supply) valve  108 , installed in second supply line  104 , opens or closes to supply or cut off, respectively, second chemical solution B in response to a second valve control signal.  
         [0034]     A mixing vessel  100  receives and mixes first and second chemical solutions A and B supplied through first and second supply lines  102 ,  104 , respectively and holds a mixing vessel chemical solution comprising one or both of the first and second chemical solutions, depending at any given time upon whether one or both of the first and second chemical solutions have already been supplied to the mixing vessel.  
         [0035]     A gas line  128 , connected to mixing vessel  100 , supplies N2 or another gas to mixing vessel  100 . A third valve  110 , installed in gas line  128 , supplies or cut offs the N2 gas in response to a third valve control signal.  
         [0036]     A fourth valve  112 , installed in an exhaust line  130 , exhausts a mixed chemical solution from mixing vessel  100  in response to a fourth valve control signal.  
         [0037]     A fifth valve  126 , installed in a third supply line  124 , supplies mixed chemical solution to a process chamber (not shown) in response to fifth valve control signal.  
         [0038]     A floating body  114  is installed within mixing vessel  100  and is adapted to move correspondingly to a volume of chemical solutions within mixing vessel  100 .  
         [0039]     A measurement rod  116  fixed to floating body  114 , moves up and down in order to measure the quantity of the chemical solution in mixing vessel  100 .  
         [0040]     A switching part  120  is sequentially switched on by the movement of measurement rod  116  based on the volume of the chemical solution, to thus output a measurement signal for the chemical solution.  
         [0041]     A controller  122  receives a chemical quantity measurement signal from switching part  120  in conformity with a predetermined mixing ratio of the mixed chemical solution, and outputs first, second, third, and fourth valve control signals, controls the mixing of the chemical solutions based on a predetermined ratio, and supplies the mixed chemical solution to a process chamber (not shown).  
         [0042]     Herewith, the first valve control signal is a signal for supplying a fixed quantity (volume) of the first chemical solution A. The second valve control signal is a signal for supplying a fixed quantity (volume) of the second chemical solution B. The third valve control signal is a signal for purging the mixed chemical solution from mixing vessel  100 . The fourth valve control signal is a signal for discharging the mixed chemical solution from mixing vessel  100  to the process chamber (not shown).  
         [0043]     A measurement rod fixing part  118  fixes measurement rod  116  and simultaneously moves the measurement rod  116  horizontally and then lowers it so as not to contact switching part  120  when the solution mixed within the mixing vessel  100  is supplied to the process chamber.  
         [0044]     A first flow meter  132  measures a supply quantity of the first chemical solution A supplied through first supply line  102 .  
         [0045]     A second flow meter  134  measures a supply quantity of the second chemical solution B supplied through second supply line  104 .  
         [0046]     Beneficially, first through fifth valves  106 ,  108 ,  110 ,  112 , and  126  may be solenoid valves.  
         [0047]     Switching part  120  is configured to individually measure supply-quantities of several types of chemical solutions by using, for example, numerous limit switches.  
         [0048]     In another embodiment, a chemical mixing device includes at least two supply lines, a mixing vessel, a mixed-chemical supply line, a chemical supply quantity measuring part and a controller.  
         [0049]     Herewith, the at least two supply lines supply different chemical solutions. The mixing vessel receives and mixes the different chemical solutions supplied through the supply lines. The mixed-chemical supply line is installed below the mixing vessel and supplies the mixed chemical solution from the mixing vessel to a process chamber. The chemical supply quantity measuring part moves to an upper side by a supply of the chemical solutions within the mixing vessel, and sequentially measures several kinds of chemical supply quantities supplied sequentially through use of a floating body installed within the mixing vessel. The controller stops the supply of the chemical solution whenever a chemical supply quantity measurement signal is sensed from the chemical supply quantity measuring part in conformity with a predetermined mixing ratio of chemical solutions, and then respectively supplies different kinds of chemical solutions to the mixing vessel by a predetermined quantity.  
         [0050]     The operation of the system shown in  FIG. 2  will be described as follows.  
         [0051]     First and second chemical solutions A and B are supplied through first and second supply lines  102 ,  104 , respectively. Controller  122  outputs the first valve control signal to open first valve  106  to supply first chemical solution A to mixing vessel  100 . Next, first flow meter  132  measures a supplied quantity of first chemical solution A supplied through first supply line  102 .  
         [0052]     At this time, floating body  114  rises as first chemical solution A is filled into mixing vessel  100 . Floating body  114  floats on the surface of the chemical solution. As floating body  114  rises to a predetermined level, measurement rod  116  connected to floating body  114  enables a first switch SW 1  of switching part  120  to trigger. When first switch SW 1  is triggered, controller  122  senses that a predetermined quantity of first chemical solution A is filled into mixing vessel  100 . Then, controller  122  outputs the first valve control signal to shut off first valve  106 ; controller  122  also outputs the second valve control signal to open second valve  108 , so that second chemical solution B can be supplied to mixing vessel  100 . Subsequently, second flow meter  134  measures a supplied quantity of second chemical solution B supplied through second supply line  104 .  
         [0053]     At this time, floating body  114  rises as second chemical solution B is filled into mixing vessel  100 . As floating body  114  once again rises, to a next predetermined level in mixing vessel  100 , measurement rod  116  enables a second switch SW 2  of switching part  120  to trigger. When second switch SW 2  is triggered, controller  122  senses that a predetermined quantity of second chemical solution B is filled into mixing vessel  100 . Then, controller  122  outputs the second valve control signal to shut off second valve  108 . Next, controller  122  outputs the third and fifth valve control signals to open third and fifth valves  110 ,  126 , respectively. The chemical solution mixed in mixing vessel  100  is thus supplied to a process chamber by the opening of third and fifth valves  110 ,  126 .  
         [0054]     As described above, first switch SW 1  of switching part  120  senses a supplied state of first chemical solution A, and second switch SW 2  senses second chemical solution B. However, it is also possible that first switch SW 1  senses a supply state of first chemical solution A, and second switch SW 2  senses whether first chemical solution A is filled above a predetermined volume. In that case, controller  122  can output fourth valve control signal to open fourth valve  112  to exhaust from mixing vessel  100 , first chemical solution A filled over the predetermined volume.  
         [0055]     Accordingly, first chemical solution A and second chemical solution B are mixed in mixing vessel  100  by a predetermined ratio.  
         [0056]     In the specific example described above and specifically illustrated in  FIG. 2 , two different chemical solutions are mixed in the mixing vessel  100 . However, the principles can be easily adapted to mix three, four, or more chemical solutions. In that case, the system of  FIG. 2  is modified as appropriate to add additional supply lines, valves, and flow meters corresponding to the number of chemical solutions to be mixed. In that case, first chemical solution A is first supplied to mixing vessel  100  and then a predetermined quantity of first chemical solution A is sensed by switch SW 1  when floating body  114  has risen to a first predetermined level. Next, second chemical solution B is supplied to mixing vessel  100 , and floating body  114  rises to a second predetermined level to turn on switch SW 2 . Thus a predetermined quantity of second chemical solution B is supplied to mixing vessel  100 . Also, a third chemical solution C can be supplied to mixing vessel  100 , and floating body  114  rises to trigger a switch SW 3 . Thus a predetermined quantity of third chemical solution C is supplied to mixing vessel  100 . Subsequently, a fourth chemical solution D can be supplied to mixing vessel  100 , and floating body  114  rises to trigger switch SW 4 . Thus a predetermined quantity of fourth chemical solution is supplied to mixing vessel  100 . Hence, controller  122  controls the supply of the first through fourth chemical solutions to mixing vessel  100  to mix them. Then controller  122  also controls fifth valve  126  so that it is opened by the fifth valve control signal to supply the mixed chemical solution. Herewith, switches SW 1 ˜SWn of switching part  120  are respectively installed at appropriate positions correspondingly to a desired, or predetermined, mixing ratio of chemical solutions.  
         [0057]     It will be apparent to those skilled in the art that modifications and variations can be made in the present invention without deviating from the spirit or scope of the invention. Thus, it is intended that the present invention cover any such modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents. Accordingly, these and other changes and modifications are seen to be within the true spirit and scope of the invention as defined by the appended claims.