Abstract:
The present invention provides a liquid storage device relates to the field of semiconductor manufacturing technology comprising: a liquid storage tank, a liquid intake tube, a liquid discharge tube and a gas discharge tube; the liquid intake tube, the liquid discharge tube and the gas discharge tube are all connected with the liquid storage tank; the liquid storage device also comprises a gas compensating tube connected with the liquid storage tank; the gas compensating tube comprises a differential pressure mechanism and a gas storage tank; one end of the differential pressure mechanism is connected with the liquid storage tank, and the other end is connected with the gas storage tank; the differential pressure mechanism is used for controlling the connection or disconnection between the liquid storage tank and the gas storage tank according to the pressure difference therebetween.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the priority benefit of China application serial no. 201110303518.9, filed Oct. 9, 2011. All disclosure of the China application is incorporated herein by reference. 
       FIELD OF THE INVENTION 
       [0002]    The present invention relates to the field of semiconductor manufacturing technology, more particularly to a liquid storage device. 
       BACKGROUND OF THE INVENTION 
       [0003]    Conventionally in the IC manufacturing process, different cleaning processes are required for the silicon wafers and during the cleaning processes, different chemical liquids may be used. For example, the chemical liquid ST250 is generally used in a cleaning apparatus for cleaning copper interconnections; the chemical liquids such as ammonia, oxyful, hydrofluoric acid, etc are generally used in a cleaning apparatus for cleaning polished wafers. In addition, the purity of the chemical liquids is highly required. In the cleaning processes, the different chemical liquids are usually transported to each machine of the equipment through chemical liquid storage devices. 
         [0004]    The Chinese patent No.201857044U discloses a conventional chemical liquid storage device. As shown in  FIG. 1 , the conventional liquid storage device generally comprises a liquid storage tank  110 , a liquid intake tube  120 , a liquid discharge tube  130 , a gas intake tube  140 , a pressure relief tube  150 , a pressure relief valve  151  disposed on the pressure relief tube  150 , a vacuum breaking tube  160 , and a vacuum breaking valve  161  disposed on the vacuum breaking tube  160 ; the liquid intake tube  120 , the liquid discharge tube  130  and the gas intake tube  140  are all connected with the liquid storage tank  110 . 
         [0005]    Referring to  FIG. 2 , the patent mentioned above also describes an improved liquid storage device  200  comprising a liquid storage tank  210 , a liquid intake tube  220 , a liquid discharge tube  230 , a gas intake tube  240  and a liquid pressure maintaining device; the liquid intake tube  220 , the liquid discharge tube  230 , and the gas intake tube  240  are all connected with the liquid storage tank  210 ; the liquid pressure maintaining device comprises an overflow tube  250  and a liquid seal container  260  with liquid stored therein; one end of the overflow tube  250  is connected with the liquid storage tank  210 , and the other end extends into the liquid in the liquid seal container  260 . The liquid seal container  260  is an opening container comprising a side wall  261  and a bottom wall  262  connected with the side wall  261 . The liquid pressure maintaining device also comprises a liquid infusion tube  270  and a liquid drain tube  280 , the liquid infusion tube  270  and the liquid drain tube  280  are both connected with the side wall  261  of the liquid seal container  260 . A first valve  221  is arranged on the liquid intake tube  220  for controlling the on-off of the liquid intake tube  220 ; a second valve  231  is arranged on the liquid discharge tube  230 ; and a third valve  241  is arranged on the gas intake tube  240 . 
         [0006]    The main difference between the two liquid storage devices mentioned above is the operation way of the device under a gas overpressure condition and a gas underpressure condition. The liquid storage device illustrated in  FIG. 1  utilizes the pressure relief valve and the vacuum breaking valve to control the pressure in the liquid storage tank. However, since the pressure relief valve and the vacuum breaking valve are interlock mechanisms and easy to lose mechanical sensitivity after being used for a certain time, the pressure in the storage tank may become unstable which may result in the damage of the tank and affect the whole manufacturing process. The liquid storage device illustrated in  FIG. 2  utilizes the overflow tube and the liquid seal container to maintain a stable pressure in the liquid storage tank. However, the depth of the overflow tube extending into the liquid seal container is required to be adjusted to prevent the liquid in the liquid seal container flowing back into the liquid storage tank. Moreover, since the liquid in the liquid seal container is generally de-ionized water which encourages the growth of bacterial, the control of the quality of the de-ionized water in the liquid seal container is required and has to be taken into consideration during the application of the de-ionized water. 
       SUMMARY OF THE INVENTION 
       [0007]    Accordingly, at least one objective of the present invention is to provide a liquid storage device to prevent the chemical liquids being damaged and enable a fluent discharge of the chemical liquids. 
         [0008]    To achieve these and other advantages and in accordance with the objective of the invention, as embodied and broadly described herein. The invention provides a liquid storage device comprising a liquid storage tank, a liquid intake tube, a liquid discharge tube and a gas discharge tube; the liquid intake tube, the liquid discharge tube and the gas discharge tube are all connected with the liquid storage tank; the liquid storage device further comprises a gas compensating tube connected with the liquid storage tank; wherein the gas compensating tube comprises a gas storage tank; and a differential pressure mechanism having one end connected with the liquid storage tank and the other end connected with the gas storage tank for controlling the connection or disconnection between the liquid storage tank and the gas storage tank according to the pressure difference therebetween. 
         [0009]    In the device mentioned above, the differential pressure mechanism comprises an outer wall, a seal, a sealing plate, and an elastic element; one end of the outer wall is connected with the liquid storage tank, and the other end is connected with the gas storage tank; the seal is fixed on the inside surface of the outer wall; the sealing plate is fixed to one end of the elastic element to open or close the tube between the liquid storage tank and the gas storage tank in conjunction with the elastic element, the other end of the elastic component is fixed to the outer wall. 
         [0010]    In the device mentioned above, the elastic element is a spring. 
         [0011]    In the device mentioned above, the liquid intake tube, the gas discharge tube, and the gas compensating tube are all connected to the top wall of the liquid storage tank; the liquid discharge tube is connected to the bottom wall of the liquid storage tank. 
         [0012]    In the device mentioned above, the liquid intake tube is provided with a first valve, the liquid discharge tube is provided with a second valve, and the gas discharge tube is provided with a check valve. 
         [0013]    In the device mentioned above, the liquid storage further comprises a gas intake tube connected with the liquid storage tank. 
         [0014]    In the device mentioned above, the gas intake tube is connected to the top wall of the liquid storage tank. 
         [0015]    In the device mentioned above, the gas intake tube is provided with a third valve. 
         [0016]    In the device mentioned above, the shape of the liquid storage tank is cylinder, cone, cuboid, or a combination of cylinder and cone. 
         [0017]    According to the present invention, a gas compensating tube is provided to replace the liquid seal container in the prior art, which can supply protective gas into the liquid storage tank rapidly, prevent the chemical liquids in the liquid storage tank being damaged and enable a smooth discharge of the chemical liquids. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]    The liquid storage device of the present invention will be elucidated by reference to the following embodiments and the accompanying drawings, in which: 
           [0019]      FIG. 1  is a schematic diagram of a conventional liquid storage device; 
           [0020]      FIG. 2  is a schematic diagram of another conventional liquid storage device; 
           [0021]      FIG. 3  is a schematic diagram of the liquid storage device according to an embodiment of the present invention; 
           [0022]      FIG. 4  is a schematic diagram of the liquid storage device according to another embodiment of the present invention; and 
           [0023]      FIG. 5  is a schematic diagram of the differential pressure mechanism in the liquid storage device illustrated in  FIG. 3  or  FIG. 4 . 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0024]    The liquid storage device of the presently preferred embodiments are discussed in further details hereinafter with respect the embodiments and the accompanying drawings. However, the embodiments described herein are not the only applications or uses contemplated for the invention. The specific embodiments discussed are merely illustrative of specific ways to make and use the invention, and do not limit the scope of the invention or the appended claims. 
         [0025]    In the liquid storage device according to the present invention, a gas storage tank and a differential pressure mechanism are utilized to supply gas to the liquid storage tank quickly. In addition, when the pressure difference between the gas storage tank and the liquid storage tank reaches a preset value, the differential pressure mechanism will open or close automatically. 
       First Embodiment 
       [0026]    As shown in  FIG. 3 , which is a schematic diagram of the liquid storage device according to the present invention, the liquid storage device  300  comprises a liquid storage tank  310 , a liquid intake tube  320 , a liquid discharge tube  330 , a gas discharge tube  350 , and a gas compensating tube  360 ; the liquid intake tube  320 , the liquid discharge tube  330 , the gas discharge tube  350  and the gas compensating tube  360  are all connected with the liquid storage tank  310 . The shape of the liquid storage tank  310  can be cylinder, cone, cuboid, or another shape. In the present embodiment, the shape of the liquid storage tank  310  is a combination of cylinder and cone. The liquid intake tube  320 , the gas discharge tube  350 , and the gas compensating tube  360  are all connected to the top wall of the liquid storage tank  310 ; the liquid discharge tube  330  is connected to the bottom wall of the liquid storage tank  310 . 
         [0027]    A valve  321  is arranged on the liquid intake tube  320  for controlling the on-off of the liquid intake tube  320 ; a valve  331  is arranged on the liquid discharge tube  330  for controlling the on-off of the liquid discharge tube  330 ; and a check valve  351  is arranged on the gas discharge tube  350 . 
         [0028]    Referring to  FIG. 3 , the gas compensating tube  360  comprises a differential pressure mechanism  361  and a gas storage tank  362 . One end of the differential pressure mechanism  361  is connected with the liquid storage tank  310 , and the other end is connected with the gas storage tank  362 . Referring to  FIG. 5 , which is a schematic diagram of the differential pressure mechanism  361 , the differential pressure mechanism  361  comprises an outer wall  1 , a seal  2 , a sealing plate  3 , and a spring  4 . The two ends of the outer wall  1  are connected with the liquid storage tank  310  and the gas storage tank  362 , respectively. The seal  2  is fixed on the inside surface of the outer wall  1 , the sealing plate  3  is fixed to one end of the spring  4 , and the other end of the spring  4  is fixed to the outer wall  1 . The sealing plate  3  will move up and down with the deformation of the spring  4 . When the pressure difference between the pressure in the gas storage tank  362  and that in the liquid storage tank  310  is higher than a preset value, the spring  4  will be compressed and the sealing plate  3  will move down with the spring  4 , thus the gas in the gas storage tank  362  can flow into the liquid storage tank  310 . 
         [0029]    The selection of the type of the spring used in the differential pressure mechanism  361  is related to the gas pressure in the gas storage tank  362 , the inner diameter of the gas compensating tube  360  and the gas pressure above the liquid in the liquid storage tank  310 . 
       Second Embodiment 
       [0030]    As shown in  FIG. 4 , the liquid storage device  400  according to the present invention comprises a liquid storage tank  410 , a liquid intake tube  420 , a liquid discharge tube  430 , a gas intake tube  440 , a gas discharge tube  450 , and a gas compensating tube  460 ; the liquid intake tube  420 , the liquid discharge tube  430 , the gas intake tube  440 , the gas discharge tube  450  and the gas compensating tube  460  are all connected with the liquid storage tank  410 . The shape of the liquid storage tank  410  can be cylinder, cone, cuboid, or another shape. In the present embodiment, the shape of the liquid storage tank  410  is a combination of cylinder and cone. The liquid intake tube  420 , the gas intake tube  440 , the gas discharge tube  450 , and the gas compensating tube  460  are all connected to the top wall of the liquid storage tank  410 , and the liquid discharge tube  430  is connected to the bottom wall of the liquid storage tank  410 . 
         [0031]    A valve  421  is arranged on the liquid intake tube  420  for controlling the on-off of the liquid intake tube  420 ; a valve  431  is arranged on the liquid discharge tube  430  for controlling the on-off of the liquid discharge tube  430 ; a valve  441  is arranged on the gas intake tube  440  for controlling the on-off of the gas intake tube  440 ; a check valve  351  is arranged on the gas discharge tube  450 . 
         [0032]    Referring to  FIG. 4 , the gas compensating tube  460  comprises a differential pressure mechanism  461  and a gas storage tank  462 . One end of the differential pressure mechanism  461  is connected with the liquid storage tank  410 , and the other end is connected with the gas storage tank  462 . Referring to  FIG. 5 , which is a schematic diagram of the differential pressure mechanism  461 , the differential pressure mechanism  461  comprises an outer wall  1 , a seal  2 , a sealing plate  3 , and a spring  4 . The two ends of the outer wall  1  are connected with the liquid storage tank  410  and the gas storage tank  462 , respectively. The seal  2  is fixed on the inside surface of the outer wall  1 , the sealing plate  3  is fixed to one end of the spring  4 , and the other end of the spring  4  is fixed to the outer wall  1 . The sealing plate  3  will move up and down corresponding to the deformation of the spring  4 . When the pressure difference between the pressure in the gas storage tank  462  and that in the liquid storage tank  410  is higher than a preset value, the spring  4  will be compressed and the sealing plate  3  will move down with the spring  4 , thus the gas in the gas storage tank  462  can flow into the liquid storage tank  410 . 
         [0033]    The liquid storage devices according to the two embodiments mentioned above are basically the same, the operating principle of the liquid storage device presented in the second embodiment will be described as follows: 
         [0034]    The gas intake tube  440  is used for supplying high purity N 2  into the liquid storage tank  410  (In the liquid storage device according to the first embodiment, the high purity N 2  can be supplied into the liquid storage tank  410  directly through the gas compensating tube  360 ). When liquid such as different chemical reagent is supplied into the liquid storage tank  410  at a high flow rate through the liquid intake tube  420 , the liquid level in the liquid storage tank  410  will rise remarkably, which may result in the compression of the high purity N 2  and the increase of the gas pressure in the liquid storage tank  410 . When the gas pressure in the liquid storage tank  410  exceeds the opening pressure of the check valve  451  on the gas discharge tube  450 , the check valve  451  will open and the high purity N 2  will flow out from the liquid storage tank  410  through the gas discharge tube  450 . 
         [0035]    When the liquid in the liquid storage tank  410  is discharged rapidly through the liquid discharge tube  430  and the pressure difference between the pressure in the gas storage tank  462  and that in the liquid storage tank  410  exceeds a first preset value, the spring  4  will be compressed (as shown in  FIG. 5 ) and the differential pressure mechanism  461  will open automatically, thus the high purity gas in the gas storage tank  462  will flow fast into the liquid storage tank  410 . When the pressure difference between the pressure in the gas storage tank  462  and that in the liquid storage tank  410  is below a second preset value, the pressure difference will not overcome the elastic force of the spring  4 , and the spring  4  will bounce and push the sealing plate  3  to the seal  2  tightly, thus the differential pressure mechanism  461  will close automatically. Wherein, the first preset valve and the second preset value are related to the initial pressure in the gas storage tank, the type of the chemical liquid in the gas storage tank and the gas volume above the chemical liquid in the gas storage tank, respectively; and both the preset values can be measured according to the actual conditions. When the gas pressure in the gas storage tank  462  decreases, gas will be supplied into the gas storage tank  462  so as to increase the gas pressure to the initial pressure, namely, the pressure of the high purity N 2  initially supplied into the gas storage tank  462 . 
         [0036]    The liquid storage device according to the present invention can be applied widely in the field of integrated circuit manufacturing technology to store the chemical liquids such as the liquid for cleaning the process machine. 
         [0037]    In summary, the gas compensating tube is provided to replace the conventional liquid seal container, which can supply protective gas into the liquid storage tank quickly, prevent the chemical liquids in the liquid storage tank being damaged and enable a smooth discharge of the chemical liquids. 
         [0038]    Although the present invention has been disclosed as above with respect to the preferred embodiments, they should not be construed as limitations to the present invention. Various modifications and variations can be made by the ordinary skilled in the art without departing the spirit and scope of the present invention. Therefore, the protection scope of the present invention should be defined by the appended claims.