Patent Publication Number: US-2007119480-A1

Title: Apparatus and method of supplying chemical solution

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
      This application claims priority from Korean Patent Application No. 10-2005- 0071138, filed Aug. 3, 2005, the disclosure of which is hereby incorporated by reference herein in its entirety.  
     BACKGROUND OF THE INVENTION  
      1. Technical Field  
      The present disclosure relates to an apparatus and method of fabricating a semiconductor device, and more particularly, to an apparatus and method of supplying a chemical solution, capable of supplying a fixed amount of chemical solution used in a semiconductor fabricating process.  
      2. Description of the Related Art  
      Generally, a chemical solution used in a semiconductor fabricating process is supplied after it is changed from a liquid phase to a gaseous phase in a bubbler or a vaporizer.  
      An example of a conventional apparatus for supplying a chemical solution includes two intermediate tanks (e.g. buffering tanks) installed between a chemical supplying tank and a process chamber. This apparatus may supply a chemical solution to the process chamber by pressurizing the tanks with helium and continuously filling a pipe with a chemical solution. Moreover, the above-mentioned conventional chemical-solution supplying apparatus is mainly for general use purposes and typically supplies chemical solutions, such as, for example, tetraethylorthosilicate (TEOS), triethylborate, triethylphosphate (TEPO), or titaniumtetrachloride (TiCl 4 ).  
      Another example of a conventional apparatus for supplying a chemical solution includes a separate container at main equipment. This type of apparatus may be used to directly supply a chemical solution having a high vapor pressure like, for example, a tetrakisdemethylamidotitanium (TDMAT) chemical solution to a process chamber.  
      However, the above-mentioned conventional chemical-solution supplying apparatuses adopt a method of continuously supplying a chemical solution regardless of the amount of chemical solution. Also, the aforementioned chemical solutions supplied by the above conventional apparatuses are generally in a liquid phase with potentially dangerous properties such as, for example, combustibility, corrosiveness, and/or toxicity. For at least the above-mentioned reasons, a buffering device should be considered for use in conjunction with chemical-solution supplying apparatuses. Accordingly, to prevent process accidents due to excessive supply of chemical solutions, there is a need for an improved chemical solution supplying apparatus and method which may stably supply a fixed amount of chemical solution.  
     SUMMARY OF THE INVENTION  
      In accordance with an exemplary embodiment of the present invention, an apparatus for supplying a chemical solution is provided. The apparatus may include a mother tank storing a chemical solution, an intermediate tank disposed in a higher position than the mother tank with a first height difference (h), and a bubbling tank disposed in a higher position than the intermediate tank with a second height difference (h′). The intermediate tank is adapted to receive a fixed amount of chemical solution from the mother tank. Moreover, the bubbling tank is adapted to receive the fixed amount of chemical solution from the intermediate tank.  
      In some exemplary embodiments, the initial pressure (P MT ) of the mother tank (MT) may be set by the following equation P MT =Chemical pressure due to the first height difference (h)+Push pressure of the intermediate tank (IT). Here, the Push pressure of the intermediate tank (IT) is the pressure of a chemical solution, which is applied to the mother tank (MT) from the intermediate tank (MT) when the chemical solution occupies a certain portion of the intermediate tank (IT).  
      In other exemplary embodiments of the present invention, the initial pressure (P IT ) of the intermediate tank (IT) may be set by the following equation P IT =Push pressure of the intermediate tank (IT)×{V IT  (empty space)/VIT}. Here, the V IT  (empty space) is the volume of an empty space of the intermediate tank (IT) which is filled with no chemical solution, and the V IT  is the entire volume of the intermediate tank (IT).  
      In other exemplary embodiments, the initial pressure (P BT ) of the bubbling tank (BT) may be set by the following equation P BT ={Initial pressure (P IT ) of the intermediate tank (IT)−Chemical pressure due to the second height difference (h′)}×{V BT  (empty space)/V (BT+h′pipe) }. Here the V BT  is the volume of an empty space of the bubbling tank (BT) which is filled with no chemical solution, and the V (BT+h′pipe)  is the sum of the entire volume of the bubbling tank (BT) and the volume of a pipe between the bubbling tank (MT) and the intermediate tank (IT).  
      In yet other exemplary embodiments of the present invention, the intermediate tank (IT) may be refilled with a chemical solution remaining in a pipe between the intermediate tank (IT) and the bubbling tank (BT). The mother tank (MT) may be refilled with a chemical solution remaining in a pipe between the mother tank (MT) and the intermediate tank (IT).  
      In further exemplary embodiments of the present invention, a solvent tank storing a solvent for washing a pipe between the mother tank (MT) and the intermediate tank (IT) may be further included. A waste tank storing a solvent to be discarded after washing the pipe may be further included.  
      In other exemplary embodiments of the present invention, the chemical solution may be TMA (trimethylaluminum) or TEMAH (tetrakismethylaminohafnium).  
      In further exemplary embodiments of the present invention, the intermediate tank (IT) may include a pipe through which an inert gas is supplied thereto so that the pressure of the intermediate tank (IT) increases. The pipe through which the inert gas is supplied may include a unit that measures the pressure of the intermediate tank (IT). The intermediate tank (IT) may include an ultrasonic sensor that checks whether or not a chemical solution exists. The intermediate tank (IT) is formed of or surface-treated with a Monel™ alloy.  
      In yet further exemplary embodiments of the present invention, the mother tank (MT) may be formed in plurality. The bubbling tank (BT) may be formed in plurality.  
      In other exemplary embodiments of the present invention, a method of supplying a chemical solution using a mother tank storing a chemical solution, an intermediate tank disposed in a higher position than the mother tank with a first height difference (h), and a bubbling tank disposed in a higher position than the intermediate tank with a second height difference (h′) is provided. The method includes setting the mother, intermediate and bubbling tanks at respective initial pressures. The method further includes providing a specific amount of chemical solution from the mother tank to the intermediate tank by maintaining the mother tank at the initial pressure of the mother tank and changing the pressure of the intermediate tank to a first pressure higher than the initial pressure of the intermediate tank. Additionally, the method further includes providing the specific amount of chemical solution from the intermediate tank to the bubbling tank by changing the pressure of the intermediate tank from the first pressure to the initial pressure of the intermediate tank and changing the pressure of the bubbling tank to a second pressure higher than the initial pressure of the bubbling tank. Moreover, the method further includes refilling the intermediate tank with a chemical solution existing in a pipe between the bubbling tank and the intermediate tank by changing the pressure of the bubbling tank to a third pressure lower than the second pressure and setting the intermediate tank at a vacuum. Also, the method further includes refilling the mother tank with a chemical solution existing in a pipe between the intermediate tank and the mother tank by setting the mother tank at a vacuum.  
      In further exemplary embodiments of the present invention, setting the mother tank at the initial pressure thereof may include setting the initial pressure (P MT ) of the mother tank by the following equation P MT =Chemical pressure due to the first height difference (h)+Push pressure of the intermediate tank. Here, the Push pressure of the intermediate tank is the pressure of a chemical solution, which is applied to the mother tank from the intermediate tank when the chemical solution occupies a certain portion of the intermediate tank.  
      In yet further exemplary embodiments of the present invention, setting the intermediate tank at the initial pressure thereof may include setting the initial pressure (P IT ) of the intermediate tank by the following equation P IT =Push pressure of the intermediate tank (IT)×{V IT  (empty space)/VIT}. Here, the V IT  (empty space) is the volume of an empty space of the intermediate tank which is filled with no chemical solution, and the V IT  is the entire volume of the intermediate tank.  
      In other exemplary embodiments of the present invention, setting the bubbling tank at the initial pressure thereof may include setting the initial pressure (P BT ) of the bubbling tank by the following equation P BT ={Initial pressure (P IT ) of the intermediate tank (IT)−Chemical pressure due to the second height difference (h′)}×{V BT  (empty space)/V (BT+h′pipe) }. Here, the V BT  is the volume of an empty space of the bubbling tank which is filled with no chemical solution, and the V (BT+h′pipe)  is the sum of the entire volume of the bubbling tank and the volume of a pipe between the bubbling tank and the intermediate tank.  
      In further exemplary embodiments of the present invention, the providing of a specific amount of chemical solution from the mother tank to the intermediate tank by maintaining the mother tank at the initial pressure of the mother tank and changing the pressure of the intermediate tank to a first pressure higher than the initial pressure of the intermediate tank may include injecting an inert gas to the mother tank so that the mother tank is maintained at the initial pressure.  
      In yet further exemplary embodiments of the present invention, washing a pipe between the intermediate tank and the mother tank by providing a solvent to the pipe between the intermediate tank and the mother tank may be further included.  
      According to exemplary embodiments of the present invention, a chemical solution may be stably supplied to a process chamber by using an intermediate buffering tank having a fixed volume. Also, because only a fixed amount of chemical solution is be supplied, the excessive supplying of the chemical solution can be prevented.  
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      Exemplary embodiments of the present invention can be understood in more detail from the following description taken in conjunction with the accompanying drawings, in which:  
       FIG. 1  is a construction view illustrating an apparatus of supplying a chemical solution according to an exemplary embodiment of the present invention; and  
       FIG. 2  is a construction view illustrating a method of supplying a chemical solution according to an exemplary embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS  
      Reference will now be made in detail to the exemplary embodiments of the present invention, examples of which are illustrated in the accompanying drawings. However, the present invention is not limited to the exemplary embodiments illustrated herein after.  
     EXEMPLARY EMBODIMENT  
       FIG. 1  is a construction view illustrating an apparatus of supplying a chemical solution according to an exemplary embodiment of the present invention.  
      Referring to  FIG. 1 , a chemical-solution supplying apparatus  200  according to an exemplary embodiment of the present invention includes mother tanks  320  and  330  storing a liquid chemical solution, bubbling tanks  210  and  220  receiving the liquid chemical solution from the mother tanks  320  and  330  and phase-changing the liquid chemical solution into a gaseous one, and one or a plurality of process chambers  230  and  240  receiving the gaseous chemical solution from the bubbling tanks  210  and  220  and in which a predetermined semiconductor process is substantially performed. To stably supply a fixed amount of chemical solution, an intermediate tank  310  serving as a buffering tank is installed between the mother tanks  320  and  330  and the bubbling tanks  210  and  220 .  
      The mother tank  320  is installed in plurality at the same height in case of a change or addition of a chemical solution. The bubbling tanks  210  and  220  are also installed at the same height, and are connected to the process chambers  230  and  240  by pipes  212  and  222  formed of SUS (stainless steel), respectively. The pipes  212  and  222  serve as paths through which a chemical solution phase-changed into a gaseous phase is supplied, for example, a precursor such as trimethylaluminum (TMA) or tetrakismethylaminohafnium (TEMAH). An aluminum oxide layer is deposited onto a wafer loaded in the process chamber  230  by using a precursor such as TMA supplied through the pipes  212  and  222 .  
      The aforementioned precursor of TMA or TEMAH has spontaneous combustion properties and therefore, a liquid precursor can be phase-changed into a gaseous phase more effectively by using, for example, a bubbling method adopting a bubbling. system like bubbling tanks  210  and  220  instead of using a vaporizer. Also, to supply a chemical solution by the bubbling method, an intermediate tank  310  is preferably installed that can supply a fixed amount of chemical solution and perform buffering and which also takes in account supply distance.  
      As precursors like TMA and TEMAH have a high corrosiveness and high reactivity, the intermediate tank  310  is preferably made of or surface-treated with a special alloy. A representative example of the special alloy includes but is not limited to a Monel™ alloy, a nickel (Ni)-copper(Cu) alloy containing small amounts of other elements like, for example, iron, manganese, or silicon thereby reducing the corrosiveness of Ni. Otherwise, if the intermediate tank  310  is neither formed of nor surface-treated with a special alloy such as a Monel™ alloy, metal impurities may thus be generated, thereby degrading the degree of purity of the chemical solution.  
      Pipes  322  and  332  formed of SUS and serving as paths through which a liquid chemical solution flows are installed between the mother tanks  320  and  330  and the intermediate tank  310 . Also, pipes  312 ,  313  and  314  formed of SUS and serving as paths through which a liquid chemical solution flows are installed between the intermediate tank  310  and the bubbling tanks  210  and  220 .  
      A pipe  324  and a vacuum pipe  326  are installed at the mother tank  320 . Here, an inert gas such as, for example, nitrogen, helium, or argon is injected into the pipe  324  (hereinafter, referred to as an inert gas injection pipe), and the vacuum pipe  326  vacuumizes the mother tank  320 . A pressure measuring unit such as a pressure transducer or a pressure gauge is installed at the inert gas injection pipe  324 . Likewise, an inert gas injection pipe  334  and a vacuum pipe  336  are installed at another mother tank  330 , and a pressure measuring unit  337  is installed at the inert gas injection pipe  334 .  
      As in the mother tanks  320  and  330 , an inert gas injection pipe  315  provided with a pressure measuring unit  317 , and a vacuum pipe  316  are installed at the intermediate tank  310 . Likewise, an inert gas injection pipe  214  provided with a pressure measuring unit  217 , and a vacuum pipe  216  are installed at the bubbling tank  210 . Also, an inert gas injection pipe  224  provided with a pressure measuring unit  227 , and a vacuum pipe  226  are installed at the other bubbling tank  220 .  
      The aforementioned process chambers  230  and  240  and the bubbling tanks  210  and  220  are installed at fabrication facility (FAB)  200 . To prevent accidents in supplying a chemical solution, the intermediate tank  310  and the mother tanks  320  and  330  are preferably installed at a plenum  300  under the FAB  200 . Accordingly, the mother tanks  320  and  330  are installed in the lowest position, the bubbling tanks  210  and  220  are installed in the highest position, and the intermediate tank  310  is installed at the medium height. Consequently, the mother tanks  310  and  320  and the intermediate tank  310  have a determined height difference (h), and the intermediate tank  310  and the bubbling tanks  210  and  220  have a predetermined height difference (h′).  
      The chemical solution supplying apparatus  100  further includes a solvent tank  340  storing a solvent, a washer washing so called dead spaces  360  near the supply pipes  322  and  332  of the mother tanks  310  and  320 . The chemical solution supplying apparatus  100  further includes a waste tank  350  storing the used solvent and other wastes.  
      The chemical solution supplying apparatus  100  installed in the aforementioned manner may supply a fixed amount of solution by a principle of pressure equilibrium between the intermediate tank  310  and the bubbling tanks  210  and  220 .  
       FIG. 2  is a construction view illustrating a method of supplying a chemical solution according to an exemplary embodiment of the present invention.  
      Referring to  FIG. 2 , firstly, the mother tank  320 , the intermediate tank  310  and the bubbling tank  210  are set at specific initial pressures, respectively. For example, the mother tank  320  has a volume of about 4 liters (l), the intermediate tank  310  a volume of about 1 liter (l), and the bubbling tank  210  a volume of about 1 to about 2 liters. Secondly, a specific amount of chemical solution is supplied from the mother tank  320  to the intermediate tank  310  by the pressure equilibrium. Thirdly, the same amount of chemical solution as the specific amount is supplied to the bubbling tank  210  from the intermediate tank  310  by the pressure equilibrium. Lastly, the mother tank  320  is refilled with a chemical solution remaining in the pipes  312 ,  313  and  322  between the tanks  210 ,  310  and  320 . The present chemical-solution supplying apparatus  100  of the present exemplary embodiment is a system that supplies a fixed amount of chemical solution by the series of the operations above.  
      In the first operation, the initial pressure of the mother tank  320 , the intermediate tank  310  and the bubbling tank  210  are set by the following equations 1, 2 and 3, respectively.  
      [Equation 1] 
      Initial pressure (P MT ) of the mother tank  320 =Chemical pressure by a height difference (h) between the mother tank  320  and the intermediate tank  310 +Push pressure of the intermediate tank  310   
      The Push pressure of the intermediate tank  310  is the pressure of a chemical solution  400 , which is applied to the mother tank  320  from the intermediate tank  310  when the chemical solution  400  occupies a certain portion of the intermediate tank  310 . The initial pressure (P MT ) of the mother tank  320  is set by injecting an inert gas (e.g., argon) through the pipe  324 . For example, the initial pressure (P MT ) of the mother tank  320  is set at about 405 kPa.  
      [Equation 2] 
      Initial pressure (P IT ) of the intermediate tank  310 =Push pressure of the intermediate tank  310 ×{V IT  (empty space)/V IT } 
      The V IT  (empty space) is the volume of an empty space of the intermediate tank  310  which is not filled with a chemical solution  400 , and the V IT  is the entire volume of the intermediate tank  310 . For example, the initial pressure (P IT ) of the intermediate tank  310  is set at about 85 kPa.  
      [Equation 3] 
      Initial pressure (P BT ) of the bubbling tank (BT)={Initial pressure (P IT ) of the intermediate tank  310 −Chemical pressure by the height difference (h′) between the intermediate tank  310  and the bubbling tank  210 }×{V BT (empty space)/V (BT+h′pipe) } 
      The V BT  (empty space) is the volume of an empty space of the bubbling tank  210  which is not filled with a chemical solution  400 , and V (BT+h′ pipe)  is the sum of the entire volume of the bubbling tank  210  and the volume of the pipe  312  and  313  between the bubbling tank  210  and the intermediate tank  310 . For example, the initial pressure (P BT ) of the bubbling tank  210  is set at about 10 kPa.  
      In the second operation, the pressure of the mother tank  320  is continuously maintained at about 405 kPa, which is the initial pressure of the mother tank  320 , and ‘x’ liters (l) of chemical solution  400  stored in the mother tank  320 , e.g., about 0.4 l of solution, is supplied to the intermediate tank  310 . The pressure of the intermediate tank  310  increases from its initial pressure (e.g., 85 kPa) to about 400 kPa.  
      In the third operation, as the pressure of the intermediate tank  310  is higher than that of the bubbling tank  210 , ‘x’ liters of chemical solution  400 , namely, about 0.4 l of solution, is supplied to the bubbling tank  210  from the intermediate tank  310  by the pressure difference. In this case, the pressure of the intermediate tank  310  decreases from about 400 kPa to about 85 kPa, the initial pressure of the intermediate tank  310 , and the pressure of the bubbling tank  210  increases to about 40 kPa from about 10 kPa, the initial pressure of the bubbling tank  210 . A liquid chemical solution  400  provided to the bubbling tank  210  is phase-changed to a gaseous chemical solution in the bubbling tank  210 , and then the gaseous chemical solution  400  is provided to the process chamber  230 , so that a predetermined semiconductor process is performed.  
      In the fourth operation, even though a chemical solution  400  is provided to the bubbling tank  210  from the intermediate tank  310 , a chemical solution still remains in the pipes  312  and  313  between the intermediate tank  310  and the bubbling tank  210 . As a chemical solution staying in the pipes  312  and  313  may generate particles, the pressure of the intermediate tank  310  is changed from its initial pressure of about 85 kPa to a vacuum level. Then, the chemical solution within the pipes  312  and  313  flows into the intermediate tank  310 , and the pressure of the bubbling tank  210  decreases from about 40 kPa to about 7 kPa. Thereafter, the pressure of the mother tank  320  is lowered to a vacuum level. Then, the mother tank  320  is refilled with the chemical solution introduced to the intermediate tank  310  and thus, the pressure of the mother tank  320  becomes about 7 kPa. Then, the mother tank  320  is refilled with chemical solutions staying in the pipes  312 ,  313  and  322  between the tanks  210 ,  310  and  320 .  
      The pressures of the tanks  210 ,  310  and  320  according to the series of operations above are represented in Table 1 below, respectively. Here, the pressure is expressed in kPa.  
                               TABLE 1                           First operation                       (initial pressure   Second   Third   Fourth       Category   setting)   operation   operation   operation                                                    Pressure of   405   405   —   7       mother tank 320       Pressure of   85   400   85   —       intermediate tank       310       Pressure of   10   —   40   7       bubbling tank 210                  
 
      Through the above series of operations, only a desired amount of chemical solution is supplied based upon a pressure equilibrium condition. With this pressure equilibrium condition, the chemical solution begins to flow due to the pressure differences between the tanks  210 ,  310  and  320  until the flow of the chemical solution is stopped due to the pressure equilibrium.  
      The volume of the intermediate tank  310  may be selected in various manners depending on the amount of chemical solution to be supplied and the working ratio of process equipment. Like the aforementioned example, when the volume of the intermediate tank  310  is set to about 1 liter (l), the intermediate tank  310  functions as an intermediate buffering tank. Accordingly, the intermediate tank  310  having a fixed volume functions as a safety device that can prevent accidents due to an excessive supply of a chemical solution, which is caused when a chemical solution with a volume greater than the fixed volume is conveyed. Also, the intermediate tank  310  serves to reduce a fixed-amount supply error. When a large amount of chemical solution is conveyed, the aforementioned series of operations is repetitively performed, so as to prevent an excess of the chemical solution from being supplied.  
      A process of washing the pipes  322  and  332  using a solvent stored in the solvent tank  340  may be performed before and after the chemical-solution supplying process. In the washing process, a solvent from the solvent tank  340  washes the pipes  322  and  332  within dead spaces  360  through the pipes  342  and  344 . The solvent discarded after the washing process, and other foreign substances are stored in a waste tank  350  and then discarded.  
      According to exemplary embodiments of the present invention, the installation of an intermediate buffering tank may contribute to securing the stability of a chemical-solution supply. Also, because an intermediate buffering tank having a fixed volume is used to supply only a fixed amount of chemical solution, process accidents or accidents due to excessive supply of a chemical solution can be prevented from occurring.  
      Having described the exemplary embodiments of the present invention, it is further noted that it is readily apparent to those of reasonable skill in the art that various modifications may be made without departing from the spirit and scope of the invention which is defined by the metes and bounds of the appended claims.