Patent Publication Number: US-11396083-B2

Title: Polishing liquid supply device

Description:
TECHNICAL FIELD 
     The present disclosure relates to a polishing liquid supply device that supplies a diluted polishing liquid to a CMP (Chemical Mechanical Polishing) polishing device. 
     BACKGROUND 
     In a semiconductor manufacturing process, there is a process of performing mechanical chemical polishing on an etched wafer  88 , which is called polishing.  FIG. 8  is a diagram showing a schematic configuration of a CMP system used in this process. As shown in  FIG. 8 , the CMP system is composed of a polishing device  8  and a polishing liquid supply device  9 . The wafer  88  to be polished is stuck on a sticking plate  82  on the lower surface of a head  81  of the polishing device  8 . The wafer  88  is pressed against a polishing pad  84  on a surface plate  3  by this head  81 . A polishing liquid obtained by diluting the slurry with ultra-pure water or a chemical is stored in a tank  91  of the polishing liquid supply device  9 . When the polishing liquid in the tank  91  of the polishing liquid supply device  9  is sucked out by a pump  92  and the head  81  and the surface plate  83  are rotated while dripping the polishing liquid from the tip of the nozzle  85  onto the polishing pad  84 , the surface of the wafer  88  is polished by a mechanical action in which the wafer  88  slides on the polishing pad  84  while being pressed against the polishing pad  84  and a chemical reaction action in which the wafer  88  is in contact with the slurry of the polishing agent. For details of the configuration of the CMP system, see Patent Document 1. 
     It is known that the polishing shape of the wafer  88  in the CMP system depends on the rotation speed of the polishing pad  84  and the supply performance of the polishing liquid. In order to improve the polishing shape of the wafer  88 , it is essential to keep the rotation speed of the polishing pad  84  and the supply amount of the polishing liquid per unit time constant. In general, the amount of polishing removal increases in proportion to the relative speed between the wafer  88  and the polishing pad  84 , and the processing pressure. 
     PRIOR ART REFERENCE 
     Patent Documents 
     Patent Document 1: Japanese Patent Application Laid-Open No. 2017-13196 
     SUMMARY 
     Problems to be Solved 
     The conventional CMP device is configured as following: a stirring device is provided in the tank of the polishing liquid supply device; an undiluted slurry solution, ultra-pure water, and an agent called chemical are poured in the blending tank; and a liquid obtained by blending these liquids with a stirring device is supplied to the polishing device as a polishing liquid. However, in such a configuration, there are problems that most of the liquid in the tank stays in the tank for a long time after blending, causing aggregation/precipitation or oxidation, and it is difficult to supply a polishing liquid with a uniform slurry concentration. 
     The present disclosure has been made in view of such problems, and an object thereof is to provide technical means capable of supplying a polishing liquid with a uniform slurry concentration to a CMP polishing device. 
     Means for Solving the Problems 
     In order to solve the above problems, the present disclosure provides a polishing liquid supply device that provides a polishing liquid to a CMP polishing device. The polishing liquid supply device includes: a first flow channel transferring slurry; a second flow channel transferring pure water; and a blending flow channel communicating with the first flow channel and the second flow channel. The blending flow channel is arranged immediately before a liquid outlet that reaches the CMP polishing device, and in the blending flow channel, a plurality of types of liquids including the slurry and the pure water are blended, and the blended liquid is supplied to the CMP polishing device as a polishing liquid. 
     In this disclosure, the blending flow channel is provided with a mixing unit mixing the slurry and the pure water. The mixing unit is provided with a first inflow port at one end of a hollow cylindrical body, an outflow port at the other end of the cylindrical body, a second inflow port on a side surface of the cylindrical body, and a stirring screw in the cylindrical body. It may be configured to mix while stirring the liquids flowing in from the first inflow port and the second inflow port by passing through the stirring screw. 
     Further, the blending flow channel is provided with a mixing unit mixing the slurry and the pure water. The mixing unit may be a unit in which a plurality of meshes are arranged side by side in a hollow cylindrical body so that mesh orientation of meshes that follow each other is shifted by a predetermined angle. 
     Further, a drum storing the slurry, and a pump pumping out the slurry in the drum and supplying the slurry to the first flow channel are included. The first flow channel may be a circulation flow channel that returns to the drum via a branching point from the first flow channel toward the blending flow channel. 
     Further, one or a plurality of pressurizing tanks provided between the drum in the first flow channel and the branching point, and a gas pressurizing part that sends out inert gas to the pressurizing tank and pushes out the liquid in the pressurizing tank may be included. 
     Further, the number of the pressurizing tanks is plural. Control means, an open/close valve that is provided in at least one of a liquid inflow port and a liquid outflow port of each of the pressurizing tanks and opens or closes according to a given signal, and a filling amount sensor detecting a filling amount of the liquid in each of the pressurizing tanks and outputting a signal indicating the detected filling amount are included. The control means may recursively repeat the control of closing the open/close valve of the pressurizing tank in which the filling amount becomes less than a predetermined amount and opening the open/close valve of another pressurizing tank. 
     Effects 
     According to the present disclosure, the liquid does not stay in the blending tank and aggregation/precipitation does not occur, and a polishing liquid with a uniform concentration can be stably supplied to the CMP polishing device. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIG. 1  is a diagram showing an overall structure of a CMP system including a polishing liquid supply device of the first embodiment of the present disclosure. 
         FIG. 2  is a diagram showing details of the configuration of the mixing unit in  FIG. 1 . 
         FIG. 3  is a diagram for explaining an action related to stirring and blending of the mixing unit in  FIG. 1 . 
         FIG. 4  is a diagram showing an overall structure of a CMP system including a polishing liquid supply device of the second embodiment of the present disclosure. 
         FIG. 5  is a diagram showing details of the configuration of a mixing unit of a modified example of the present disclosure. 
         FIG. 6  is a diagram showing details of configuration of a pressurizing tank of the polishing liquid supply device of the modified example of the present disclosure. 
         FIG. 7  is a diagram showing an overall structure of a CMP system including a polishing liquid supply device of the modified example of the present disclosure. 
         FIG. 8  is a diagram showing a schematic configuration of a conventional CMP system. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, embodiments of the present disclosure are explained with reference to drawings. 
     First Embodiment 
       FIG. 1  is a diagram showing an overall structure of a CMP system  1  including a polishing liquid supply device  2  of the first embodiment of the present disclosure. Solid lines connecting elements in  FIG. 1  indicate pipes, and arrows on the solid lines indicate traveling directions of the liquid in the pipes. The CMP system  1  is used in a polishing process of a semiconductor manufacturing process. The CMP system  1  has a CMP polishing device  8  and a polishing liquid supply device  2 . A liquid inlet  89  of the CMP polishing device  8  is connected to a liquid outlet  79  of the polishing liquid supply device  2 . The CMP polishing device  8  polishes a wafer  88  to be polished. The polishing liquid supply device  2  supplies the polishing liquid to the CMP polishing device  8 . 
     The polishing liquid is a liquid obtained by blending slurry, ultra-pure water, a chemical, and hydrogen peroxide water at a predetermined ratio. Here, the slurry includes slurry including abrasive grain or the like, alkaline slurry including SiO 2 , neutral slurry including CeO 2 , and acidic slurry including Al 2 O 3 , and the like. The chemical includes silica, and citric acid and the like. The effective component of the slurry or the chemical may be determined according to the wafer  88  to be polished, the polishing shape, or the like. 
     The polishing liquid supply device  2  has a PLC (Programmable Logic Controller)  70 , an ultra-pure water inlet  29  connected to an external ultra-pure water supply source, a drum  12   CHM  storing a chemical, a drum  12   SLR  storing slurry, a drum  12   H2O2  storing hydrogen peroxide water, a flow channel  20   DIW  (second flow channel) forming a transfer path of the ultra-pure water, a flow channel  10   CHM  forming a transfer path of the chemical, a flow channel  10   SLR  (first flow channel) forming a transfer path of the slurry, a flow channel  10   H2O2  forming a transfer path of the hydrogen peroxide water, and a blending flow channel  40  in which 4 types of liquids of ultra-pure water, a chemical, slurry, and hydrogen peroxide water are blended. 
     The blending flow channel  40  is arranged immediately before a liquid outlet  79  that reaches the CMP polishing device  8 . The blending flow channel  40  communicates with the flow channel  20   DIW , the flow channel  10   CHM , the flow channel  10   SLR , and the flow channel  10   H2O2 . The blending flow channel  40  is provided with mixing units  50   CHM ,  50   SLR , and  50   H2O2 , and flow rate sensors  61   CHM ,  62   CHM ,  63   CHM ,  61   SLR ,  62   SLR ,  63   SLR ,  61   H2O2 ,  62   H2O2 , and  63   H2O2 . 
     The flow channel  20   DIW  is provided with a low-pressure value 21 (precise regulator). The flow rate of the ultra-pure water in the flow channel  20   DIW  is kept constant (for example, 1 L/min) by the working of the low-pressure value 21. The end of the pipe forming the flow channel  20   DIW  is connected to the inflow port F 1  of the mixing unit  50   CHM . The ultra-pure water transferred in the flow channel  20   DIW  flow into the mixing unit  50   CHM  from the inflow port F 1 . 
     The flow channel  10   CHM  is provided with a pump  11   CHM , a pressurizing tank  13   mm , a filling amount sensor  16   CHM , a flow-controller  15   CHM , and a gas pressurizing part  14   CHM . The pump  11   CHM  is a rotary pump such as a diaphragm pump or a bellows pump. The pump  11   CHM  pumps out the chemical in the drum  12   CHM  and supplies the chemical to the side where the pressurizing tank  13   CHM  is located in the flow channel  10   CHM . The chemical pumped out by the pump  11   CHM  flows into the pressurizing tank  13   CHM  and is filled in the pressurizing tank  13   CHM . The liquid inflow port of the pressurizing tank  13   CHM  is provided with an open/close valve VLU and the liquid outflow port is provided with an open/close valve VLL, respectively. The open/close valves VLU and VLL of the pressurizing tank  13   CHM  open when an open signal SV OP  is given, and close when a close signal SV CL  is given. 
     The filling amount sensor  16   CHM  detects the filling amount of the chemical in the pressurizing tank  13   CHM  and outputs a signal indicating the detected filling amount. Specifically, when the filling amount of the chemical in the pressurizing tank  13   CHM  becomes less than a predetermined value, the filling amount sensor  16   CHM  outputs a detection signal ST CHM  indicating that fact. 
     Under the control of the flow-controller  15   CHM , the gas pressurizing part  14   CHM  sends out nitrogen, which is an inert gas, from the gas inflow port at the upper portion of the pressurizing tank  13   CHM  into the pressurizing tank  13   CHM . The chemical in the pressurizing tank  13   CHM  is pushed out from the outflow port at the lower portion of the pressurizing tank  13   CHM  by the pressure of nitrogen. 
     The pipe of the flow channel  10   CHM  is connected to the inflow port F 2  of the mixing unit  50   CHM . The chemical transferred in the flow channel  10   CHM  flows into the mixing unit  50   CHM  from the inflow port F 2 . 
       FIG. 2(A)  is a front view of the mixing unit  50   CHM .  FIG. 2(B)  is a diagram of  FIG. 2  (A) viewed from the direction of arrow B.  FIG. 2(C)  is a diagram showing the inside of  FIG. 2(B) . The mixing unit  50   CHM  has a housing HZ with two inflow ports F 1  and F 2  and one outflow port, and a stirring screw SCR accommodated in the housing HZ. The main body of the housing HZ is a hollow cylindrical body having a diameter substantially the same as or slightly thicker than the pipes of the flow channel  10   CHM  or the flow channel  20   DIW . There is an inflow port F 1  at one end in the extending direction of the main body of the housing HZ, and an outflow port F 3  at the other end. There is an inflow port F 2  in the vicinity of the inflow port F 1  on the side surface of the main body of the housing HZ. The inflow port F 2  communicates with the inside of the main body of the housing HZ. 
     The inflow port F 1  communicates with the pipe HK 1  in the housing HZ. The tip end of the pipe HK 1  is connected to the stirring screw SCR. The inflow port F 2  communicates with the pipe HK 2  in the housing HZ. There is a nozzle NZ at the tip end of the pipe HK 2 . The nozzle NZ is inserted into the pipe HK 1  from the side surface of the pipe HK 1 . In the pipe HK 1 , the liquid discharge port of the nozzle NZ faces the stirring screw SCR. 
     The stirring screw SCR is a stirring screw in which N (N is a natural number of 2 or more, and in the example of  FIG. 2 , N=4) twist blades VL-k (k=1 to N) are arranged at intervals on a shaft rod AXS. The shaft rod AXS is supported in the inflow port F 1  and the outflow port F 3  of the housing HZ. The twist blades VL-k has a shape twisted half turn (180 degrees) along the outer peripheral surface of the shaft rod AXS. A plurality of twist blades VL-k (k=1 to N) are arranged with a phase shift of 90 degrees, and the twist blades VL-k that follow each other are perpendicular to each other with a shift of 90 degrees. The intervals between the twist blades VL-k that follow each other become equal. The intervals between the twist blades VL-k that follow each other become shorter than the size (the width in the front-rear direction) of the twist blades VL-k themselves. 
     Two types of liquids (ultra-pure water and chemical) that flow into the mixing unit  50   CHM  from the inflow port F 1  and the inflow port F 2  of the mixing unit  50   CHM  are mixed while being stirred in the mixing unit  50   CHM , and a liquid obtained by blending the two types of liquids is sent out from the outflow port F 3  of the mixing unit  50   CHM . 
     The flow rate sensor  61   CHM  detects the flow rate per unit time of the liquid (ultra-pure water) at a position immediately before the inflow port F 1  of the mixing unit  50   CHM  in the blending flow channel  40 , and outputs a signal SF 1   CHM  indicating the detected flow rate. The flow rate sensor  62   CHM  detects the flow rate per unit time of the liquid (chemical) at a position immediately before the inflow port F 2  of the mixing unit  50   CHM  in the blending flow channel  40 , and outputs a signal SF 2   CHM  indicating the detected flow rate. The flow rate sensor  63   CHM  detects the flow rate per unit time of a liquid (a liquid obtained by blending ultra-pure water and chemical) at a position immediately after the outflow port F 3  of the mixing unit  50   CHM  in the blending flow channel  40 , and outputs a signal SF 3   CHM  indicating the detected flow rate. 
     The flow channel  10   SLR  becomes a circulation flow channel that returns to the drum  12   SLR  from the flow channel  10   SLR  through a branching point  17   SLR  toward the blending flow channel  40 . The flow channel  10   SLR  is provided with a pump  11   SLR , a pressurizing tank  13   SLR , a filling amount sensor  16   SLR , a flow-controller  15   SLR , and a gas pressurizing part  14   SLR . The pump  11   SLR  pumps out the slurry in the drum  12   SLR  and supplies the slurry to the side where the pressurizing tank  13   SLR  is located in the flow channel  10   SLR . The slurry pumped out by the pump  11   SLR  flows into the pressurizing tank  13   SLR  and is filled in the pressurizing tank  13   SLR . The liquid inflow port at the upper portion of the pressurizing tank  13   SLR  is provided with an open/close valve VLU and the liquid outflow port at the lower portion is provided with an open/close valve VLL, respectively. The open/close valves VLU and VLL of the pressurizing tank  13   SLR  open when an open signal SV OP  is given, and close when a close signal SV CL  is given. 
     The filling amount sensor  16   SLR  detects the filling amount of the slurry in the pressurizing tank  13   SLR  and outputs a signal indicating the detected filling amount. Specifically, when the filling amount of the slurry in the pressurizing tank  13   SLR  becomes less than a predetermined value, the filling amount sensor  16   SLR  outputs a detection signal ST SLR  indicating that fact. 
     Under the control of the flow-controller  15   SLR , the gas pressurizing part  14   SLR  sends out nitrogen, which is an inert gas, from the gas inflow port at the upper portion of the pressurizing tank  13   SLR  into the pressurizing tank  13   SLR . The slurry in the pressurizing tank  13   SLR  is pushed out from the outflow port at the lower portion of the pressurizing tank  13   SLR  by the pressure of nitrogen. 
     The end portion branched from the branching point  17   SLR  in the pipe of the flow channel  10   SLR  is connected to the inflow port F 2  of the mixing unit  50   SLR . The slurry transferred in the flow channel  10   SLR  is branched at the branching point  17   SLR  and then flows into the mixing unit  50   SLR  from the inflow port F 2 . The remaining slurry that has not advanced to the side of the mixing unit  50   SLR  returns to the drum  12   SLR  through the pipe between the branching point  17   SLR  and the drum  12   SLR . 
     The two types of liquids (ultra-pure water including chemical, and slurry) flowing into the mixing unit  50   SLR  from the inflow ports F 1  and F 2  of the mixing unit  50   SLR  are mixed while being stirred by passing through the stirring screw SCR in the mixing unit  50   SLR , and the liquid obtained by blending the chemical, the ultra-pure water, and the slurry is sent out from the outflow port F 3  of the mixing unit  50   SLR . 
     The structure of the mixing unit  50   SLR  is the same as that of the mixing unit  50   CHM . As shown in  FIG. 2(A) ,  FIG. 2(B) , and  FIG. 2(C) , the mixing unit  50   SLR  has a housing HZ with two inflow ports F 1  and F 2  and one outflow port F 3 , and a stirring screw SCR accommodated in the housing HZ. 
     Here, the liquid (ultra-pure water including chemical) flowing into the mixing unit  50   SLR  from the inflow port F 1  and the liquid (slurry) flowing into the mixing unit  50   SLR  from the inflow port F 2  merge at a position where the nozzle NZ protrudes in the pipe HK 1 . After this merging, the two types of liquids pass through the twist blade VL- 1 →twist blade VL- 2 →twist blade VL- 3 →twist blade VL- 4  successively. As shown in  FIG. 3(A) , each time they pass through one twist blade VL-k, the two types of liquids are approximately equally divided into one twist surface side of the twist blade VL-k and the other twist surface side on the back side thereof. Further, as shown in  FIG. 3(B) , the two types of liquids recirculate from the shaft rod AXS side to the inner wall surface side or from the inner wall surface side to the shaft rod AXS side on the twist surface of the twist blade VL-k. Furthermore, as shown in  FIG. 3(C) , between the two twist blades VL-k that follow each other, the rotation direction of the two types liquids are reversed. A liquid formed by diluting the slurry at a uniform concentration is obtained by the three actions of the dividing action, the recirculating action and the reversing action. 
     In  FIG. 1 , the flow rate sensor  61   SLR  detects the flow rate per unit time of the liquid (ultra-pure water including chemical) at a position immediately before the inflow port F 1  of the mixing unit  50   SLR  in the blending flow channel  40 , and outputs a signal SF 1   SLR  indicating the detected flow rate. The flow rate sensor  62   SLR  detects the flow rate per unit time of the liquid (slurry) at a position immediately before the inflow port F 2  of the mixing unit  50   SLR  in the blending flow channel  40 , and outputs a signal SF 2   SLR  indicating the detected flow rate. The flow rate sensor  63   SLR  detects the flow rate per unit time of a liquid (a liquid obtained by blending ultra-pure water, a chemical, and slurry) at a position immediately after the outflow port F 3  of the mixing unit  50   SLR  in the blending flow channel  40 , and outputs a signal SF 3   SLR  indicating the detected flow rate. 
     The flow channel  10   H2O2  is provided with a pump  11   H2O2 , a pressurizing tank  13   H2O2 , a filling amount sensor  16   H2O2 , a flow-controller  15   H2O2 , and a gas pressurizing part  14   H2O2 . The pump  11   H2O2  pumps out the hydrogen peroxide water in the drum  12   H2O2  and supplies the hydrogen peroxide water to the side where the pressurizing tank  13   H2O2  is located in the flow channel  10   H2O2 . The hydrogen peroxide water pumped out by the pump  11   H2O2  flows into the pressurizing tank  13   H2O2  and is filled in the pressurizing tank  13   H2O2 . The liquid inflow port at the upper portion of the pressurizing tank  13   H2O2  is provided with an open/close valve VLU and the liquid outflow port at the lower portion is provided with an open/close valve VLL, respectively. The open/close valves VLU and VLL of the pressurizing tank  13   H2O2  open when an open signal SV OP  is given, and close when a close signal SV CL  is given. 
     The filling amount sensor  16   H2O2  detects the filling amount of the hydrogen peroxide water in the pressurizing tank  13   H2O2  and outputs a signal indicating the detected filling amount. Specifically, when the filling amount of the hydrogen peroxide water in the pressurizing tank  13   H2O2  becomes less than a predetermined value, the filling amount sensor  16   H2O2  outputs a detection signal ST H2O2  indicating that fact. 
     Under the control of the flow-controller  15   H2O2 , the gas pressurizing part  14   H2O2  sends out nitrogen, which is an inert gas, from the gas inflow port at the upper portion of the pressurizing tank  13   H2O2  into the pressurizing tank  13   H2O2 . The hydrogen peroxide water in the pressurizing tank  13   H2O2  is pushed out from the outflow port at the lower portion of the pressurizing tank  13   H2O2  by the pressure of nitrogen. 
     The pipe of the flow channel  10   H2O2  is connected to the inflow port F 2  of the mixing unit  50   H2O2 . The hydrogen peroxide water transferred in the flow channel  10   H2O2  flows into the mixing unit  50   H2O2  from the inflow port F 2 . The structure of the mixing unit  50   H2O2  is the same as the structure of the mixing unit  50   CHM . 
     Two types of liquids that flow into the mixing unit  50   H2O2  from the inflow port F 1  and the inflow port F 2  of the mixing unit  50   H2O2  are mixed while being stirred in the mixing unit  50   H2O2 , and a liquid obtained by blending the two types of liquids is sent out from the outflow port F 3  of the mixing unit  50   H2O2 . 
     The flow rate sensor  61   H2O2  detects the flow rate per unit time of a liquid (a liquid obtained by blending ultra-pure water, a chemical, and a slurry) at a position immediately before the inflow port F 1  of the mixing unit  50   H2O2  in the blending flow channel  40 , and outputs a signal SF 1   H2O2  indicating the detected flow rate. The flow rate sensor  62   H2O2  detects the flow rate per unit time of the liquid (hydrogen peroxide water) at a position immediately before the inflow port F 2  of the mixing unit  50   H2O2  in the blending flow channel  40 , and outputs a signal SF 2   H2O2  indicating the detected flow rate. The flow rate sensor  63   H2O2  detects the flow rate per unit time of the liquid (a liquid obtained by blending ultra-pure water, a chemical, slurry, and hydrogen peroxide water) at a position immediately after the outflow port F 3  of the mixing unit  50   H2O2  in the blending flow channel  40 , and outputs a signal SF 3   H2O2  indicating the detected flow rate. 
     The PLC 70  is a device that serves as control means of the polishing liquid supply device  2 . The PLC 70  performs a first control, a second control and a third control. In the first control, the operation of the flow-controllers  15   CHM ,  15   SLR , and  15   H2O2  is controlled to adjust the gas pressure of the gas pressurizing parts  14   CHM ,  14   SLR , and  14   H2O2 , so that a magnitude relation among a liquid pressure Pa of the inflow port F 1  of the mixing unit  50   CHM , a liquid pressure Pb of the inflow port F 2  of the mixing unit  50   CHM , a liquid pressure Pc of the inflow port F 1  of the mixing unit  50   SLR , a liquid pressure Pd of the inflow port F 2  of the mixing unit  50   SLR , a liquid pressure Pe of the inflow port F 1  of the mixing unit  50   H2O2 , and a liquid pressure Pf of the inflow port F 2  of the mixing unit  50   H2O2  is Pa&lt;Pb&lt;Pc&lt;Pd&lt;Pe&lt;Pf. In the second control, based on the relationship between the flow rate of the liquid in the blending flow channel  40  and the target value of dilution, the flow-controllers  14   CHM ,  15   SLR , and  15   H2O2  are controlled to adjust the nitrogen pressure of the gas pressurizing parts  14   CHM ,  14   SLR , and  14   H2O2 . In the third control, the pressurizing tank  13  that communicates with the blending flow channel  40  is switched. 
     More specifically, the PLC 70  monitors the pressures Pa, Pb, Pc, Pd, Pe, Pd, and Pf from the output signals SF 1   CHM , SF 1   SLR , and SF 1   H2O2  of the flow rate sensors  61   CHM ,  61   SLR , and  61   H2O2 , and the output signals SF 2   CHM , SF 2   SLR , and SF 2   H2O2  of the flow rate sensors  62   CHM ,  62   SLR , and  62   H2O2 . The PLC 70  supplies a signal SG instructing the flow-controller  15   CHM  to increase the nitrogen pressure when Pa≥Pb. The PLC 70  supplies a signal SG instructing the flow-controller  61   SLR  to increase the nitrogen pressure when Pc≥Pd. The PLC 70  supplies a signal SG instructing the flow-controller  15   H2O2  to increase the nitrogen pressure when Pe≥Pf. 
     The PLC 70  sets a value obtained by dividing the output signal SF 2   SLR  of the flow rate sensor  62   SLR  by the output signal SF 1   SLR  of the flow rate sensor  61   SLR  as the current dilution of the slurry, and when the dilution of the slurry is lower than the target value of the dilution, it supplies the signal SG instructing the flow-controller  15   SLR  to increase the nitrogen pressure. The flow-controller  15   SLR  controls the gas pressurizing part  14   SLR  according to the given signal SG; and adjusts the flow rate of the liquid in the flow channel  10   SLR . 
     The PLC  70  monitors whether or not the signals ST CHM , ST SLR , and ST H2O2  in the filling amount sensors  16   CHM ,  16   SLR , and  16   H2O2  are output. For the four pressurizing tanks  13   CHM , the PLC 70  recursively repeats control of closing the open/close valves VLU and VLL of the pressurizing tank  13   CHM  in which the filling amount becomes less than a predetermined amount, and opening the open/close valves VLU and VLL of other pressurizing tanks  13   CHM . The PLC 70  repeats the same control for the pressurizing tanks  13   SLR , and  13   H2O2 . 
     The above is the details of the configuration of the present embodiment. According to the present embodiment, the following effects can be obtained. 
     First, in the present embodiment, there is a blending flow channel  40  communicating with the flow channel in which ultra-pure water, a chemical, slurry, and hydrogen peroxide water are transferred. In this blending flow channel  40 , a plurality of types of liquids are blended, and the blended liquid is supplied to the CMP polishing device  8  as a polishing liquid. For this reason, in the present embodiment, it is not necessary to provide a blending tank that blends a plurality of types of liquids. Therefore, the liquid does not stay in the blending tank and aggregation/precipitation does not occur, and a polishing liquid with a uniform concentration can be stably supplied to the CMP polishing device  8 . 
     Second, in the present embodiment, since there is no blending tank, it is not necessary to provide a drying prevention mechanism and a solidification prevention mechanism in the blending tank. Accordingly, since it is not necessary to replace consumption articles that play a part of the drying prevention mechanism and the solidification prevention mechanism, the number of maintenance processes of the polishing liquid supply device  2  can be greatly reduced. 
     Third, in the embodiment, the blending flow channel  40  is arranged immediately before a liquid outlet  79  that reaches the CMP polishing device  8 . For this reason, after a polishing liquid is obtained by blending a plurality of types of liquids, the polishing liquid can be used for polishing a wafer  88  by the CMP polishing device  8  in a fresh state. Therefore, chemical attack is less likely to occur, and coarse particles that cause scratches can be reduced. In addition, the polishing liquid does not change with time from blending to use. Thereby, a stable polishing property can be obtained. 
     Fourth, in the present embodiment, the blending flow channel  40  is provided with mixing units  50   CHM ,  50   SLR , and  50   H2O2 , and the mixing units  50   CHM ,  50   SLR , and  50   H2O2  are provided with stirring screws SCR. The liquid flowed in from the inflow port is mixed while being stirred by passing through the stirring screw SCR. Therefore, the time required for stirring can be greatly reduced as compared with the conventional method in which the liquid is stored in the blending tank and stirred by the stirring device. Further, the mixing units  50   CHM ,  50   SLR , and  50   H2O2  are less bulky than the blending tank, and the configuration itself of the mixing units  50   CHM ,  50   SLR , and  50   H2O2  is simpler than that of the blending tank. Therefore, the device design of the CMP system  1  is simplified and the delivery time of the system can be shortened. 
     Fifth, in the present embodiment, the blending flow channel  40  is provided with flow rate sensors  61   CHM ,  62   CHM ,  63   CHM ,  61   SLR ,  62   SLR ,  63   SLR ,  61   H2O2 ,  62   H2O2 , and  63   H2O2  that detect the liquid flow rate per unit time in the blending flow channel  40  and output signals SF 1   CHM , SF 1   SLR , SF 1   H2O2 , SF 2   CHM , SF 2   SLR , and SF 2   H2O2  indicating the detected flow rate, and the flow channels in which a chemical, slurry, and hydrogen peroxide water are transferred are provided with flow-controllers  15   CHM ,  15   SLR , and  15   H2O2  adjusting the flow rate of the liquid in the flow channel according to the given signals SG Then, the PLC 70 , which is the control means, controls the operations of the flow-controllers  15   CHM ,  15   SLR , and  15   H2O2  based on the relationship between the liquid flow rate in the blending flow channel  40  and the target value. Therefore, the slurry concentration can be adjusted efficiently by setting the flow rate target value with the operation element. Further, it is also possible to flexibly deal with circumstantial changes such as a change in the dilution ratio of the polishing liquid, a change in the wafer  88 , a change in the polishing removal amount on the CMP polishing device  8  side. 
     Sixth, in the present embodiment, the number of the pressurizing tanks  13   CHM ,  13   SLR , and  13   H2O2  is plural (four each in the example of the present embodiment), and the PLC 70  as the control means recursively repeats the control of closing the open/close valves VLU and VLL of the pressurizing tanks  13   CHM ,  13   SLR , and  13   H2O2  in which the filling amount becomes less than a predetermined amount, and opening the open/close valves VLU and VLL of other pressurizing tanks  13   CHM ,  13   SLR , and  13   H2O2 . Therefore, according to the present embodiment, it is possible to reliably prevent the occurrence of a situation where the liquid in the pressurizing tanks  13   CHM ,  13   SLR , and  13   H2O2  is exhausted and the supply of the liquid to the mixing units  50   CHM ,  50   SLR , and  50   H2O2  comes to an end. 
     Second Embodiment 
       FIG. 4  is a diagram showing an overall structure of a CMP system  1  including a polishing liquid supply device  2  of the second embodiment of the present disclosure. In  FIG. 4 , the same reference numerals are given to the same elements as those of the polishing liquid supply device  2  of the above first embodiment. The mixing units  50   CHM ,  50   SLR , and  50   H2O2  of the polishing liquid supply device  2  of the above first embodiment are formed in a structure having a cylindrical body with a diameter that is substantially the same as or slightly larger than that of the flow channel, and a plurality of liquids were blended in-line in the mixing units  50   CHM ,  50   SLR , and  50   H2O2 . On the other hand, the mixing unit  50 A of the polishing liquid supply device  2  of the present embodiment is configured to have a blending tank  52 A and a stirring device  59 A, and a plurality of liquids are stirred and blended in the tank  52 A. 
     The polishing liquid supply device  2  of the CMP system  1  has a PLC 70 A, an ultra-pure water inlet  29  connected to an external ultra-pure water supply source, a drum  12   CHM  storing a chemical, a drum  12   SLR  storing slurry, a drum  12   H2O2  storing hydrogen peroxide water, a flow channel  20   DIW  (second flow channel) forming a transfer path of the ultra-pure water, a flow channel  10 A CHM  forming a transfer path of the chemical, a flow channel  10 A SLR  (first flow channel) forming a transfer path of the slurry, a flow channel  10 A H2O2  forming a transfer path of the hydrogen peroxide water, a mixing unit  50 A connected to the pipes of these flow channels  10 A CHM ,  10 A SLR , and  10 A H2O2 , and a flow channel  40 A from the mixing unit  50 A to the CMP polishing device  8 . 
     The flow channel  10 A CHM  is provided with a pump  11   CHM . The pump  11   CHM  pumps out the chemical in the drum  12   CHM  and supplies the chemical to the side where the mixing unit  50 A is located in the flow channel  10 A CHM . The flow channel A 10   SLR  is provided with a pump  11   SLR . The pump  11   SLR  pumps out the slurry in the drum  12   SLR  and supplies the slurry to the side where the mixing unit  50 A is located in the flow channel  10 A SLR . The flow channel  10 A H2O2  is provided with a pump  11   H2O2 . The pump  11   H2O2  pumps out the hydrogen peroxide water in the drum  12   H2O2  and supplies the hydrogen peroxide water to the side where the mixing unit  50 A is located in the flow channel  10 A H2O2 . 
     The flow channel  40 A is a circulation flow channel that returns to the blending tank  52 A of the mixing unit  50 A through a branching point  17 A toward the CMP polishing device  8 . 
     The mixing unit  50 A obtains the polishing liquid used in the polishing of the CMP polishing device  8  by blending four types of liquids of a chemical, ultra-pure water, slurry, and hydrogen peroxide water. The mixing unit  50 A has a case body  51 A, a blending tank  52 A, a stirring device  59 A, a pressurizing tank  13 A, a filling amount sensor  16 A, a flow-controller  15 A, and a gas pressurizing part  14 A. 
     The case body  51 A has a hollow rectangular parallelopiped shape. There is a blending tank  52 A in the upper portion in the case body  51 A, and a plurality of (three in the example of  FIG. 2 ) pressurizing tanks  13 A in the lower portion in the case body  51 A. 
     The blending tank  52 A has a hollow cylindrical shape. The ultra-pure water transferred in the flow channel  20   DIW , the chemical transferred in the flow channel  10 A CHM , the slurry transferred in the flow channel  10 A SLR , and the hydrogen peroxide water transferred in the flow channel  10 A H2O2  flow into the blending tank  52 A. The stirring device  59 A stirs and mixes the four types of liquids that have flowed into the blending tank  52 A. 
     There is a pipe extending downward at the bottom of the blending tank  52 A. This pipe is branched into a plurality of pipes, and the branched pipes are connected to the inflow ports of the plurality of pressurizing tanks  13 A. The pressurizing tank  13 A has a cylindrical shape. The pressurizing tank  13 A is arranged at a position directly below the blending tank  52 A in the case body  51 A so that the inflow port is directed upward and the outflow port is directed downward. 
     In the blending tank  52 A, the polishing liquid obtained by stirring the four types of liquids flow to the pressurizing tank  13 A through the lower pipe by its own weight, and filled in the pressurizing tank  13 A. The liquid inflow port of the pressurizing tank  13 A is provided with an open/close valve VLU and the liquid outflow port is provided with an open/close valve VLL, respectively. The open/close valves VLU and VLL of the pressurizing tank  13 A open when an open signal SV OP  is given, and close when a close signal SV CL  is given. 
     The filling amount sensor  16 A detects the filling amount of the liquid in the pressurizing tank  13 A and outputs a signal indicating the detected filling amount. Specifically, when the filling amount of the liquid in the pressurizing tank  13 A becomes less than a predetermined value, the filling amount sensor  16 A outputs a detection signal ST indicating that fact. 
     Under the control of the flow-controller  15 A, the gas pressurizing part  14 A sends out nitrogen, which is an inert gas, from the gas inflow port at the upper portion of the pressurizing tank  13 A into the pressurizing tank  13 A. The liquid in the pressurizing tank  13 A is pushed out from the outflow port at the lower portion of the pressurizing tank  13 A by the pressure of nitrogen. 
     The PLC 70 A is a device that serves as control means of the polishing liquid supply device  2 . The PLC 70 A performs control of switching the pressurizing tank  13 A that communicates with the blending flow channel  40 . 
     More specifically, whether there is a signal ST in the filling amount sensor  16 A is monitored. For the three pressurizing tanks  13 A, the PLC 70 A recursively repeats control of closing the open/close valves VLU and VLL of the pressurizing tank  13 A in which the filling amount becomes less than a predetermined amount, and opening the open/close valves VLU and VLL of other pressurizing tanks  13 A. 
     The above is the details of the configuration of the present embodiment. According to the present embodiment, the following effects can be obtained. 
     First, in the present embodiment, the polishing liquid obtained by blending the liquids in the blending tank  52 A of the mixing unit  50 A is filled in the pressurizing tank  13 A, and the gas pressurizing part  14 A sends out an inert gas into the pressurizing tank  13 A to push out the polishing liquid in the pressurizing tank  13 A to the CMP polishing device  8 . Therefore, it is possible to stably supply an ultrahigh precise polishing liquid to the CMP polishing device  8 . 
     Second, in the present embodiment, a blending tank  52 A storing the polishing liquid obtained by blending the liquids is included. A flow channel reaching the CMP polishing device  8  is a circulation flow channel that returns to the blending tank  52 A via a branching point  17 A from the blending tank  52 A toward the CMP polishing device  8 . Therefore, the liquid does not stay in the blending tank  52 A and aggregation/precipitation does not occur, and a polishing liquid with a uniform concentration can be stably supplied to the CMP polishing device  8 . 
     Third, in the present embodiment, the pressurizing tank  13 A is arranged below the blending tank  52 A so that the liquid in the blending tank  52 A flows from the blending tank  52 A into the pressurizing tank  13 A by its weight. Therefore, it is not necessary to provide a special device such as a pump in the blending tank  52 A, and the liquid can be transferred from the blending tank  52 A to the pressurizing tank  13 A without risk of oxidation of the polishing liquid or change in the components. 
     Fourth, in the present embodiment, the pressurizing tank  13 A has a cylindrical shape. The pressurizing tank  13 A is arranged so that the inflow port of the liquid from the blending tank  52 A to the pressurizing tank  13 A is on the upper side, and the outflow port of the liquid from the pressurizing tank  13 A to the CMP polishing device  8  is on the lower side. Therefore, the liquid flow of the blending tank  52 A→the pressurizing tank  13 A→the CMP polishing device  8  can be made even smoother. 
     Fifth, in the present embodiment, the number of pressurizing tanks  13 A is plural. The PLC  70  as the control means recursively repeats control of closing the open/close valves VLU and VLL of the pressurizing tank  13 A in which the filling amount becomes less than a predetermined amount and opening the open/close valves VLU and VLL of the other pressurizing tanks  13 A. Therefore, according to the present embodiment, it is possible to reliably prevent the occurrence of a situation where the liquid in the pressurizing tank  13 A is exhausted and the supply of the liquid to the CMP polishing device  8  comes to an end. 
     MODIFIED EXAMPLE 
     Although the first and second embodiments of the present disclosure have been described above, the following modifications may be added to these embodiments.
     (1) The above first embodiment has been formed in a manner where the flow rate sensors  61   CHM ,  61   SLR ,  61   H2O2 ,  62   CHM ,  62   SLR , and  62   H2O2  detect the flow rate per unit time of the liquid in the blending flow channel  40 , and the flow-controllers  15   CHM ,  15   SLR , and  15   H2O2  adjust the flow rate of the liquid in the flow channels  10   CHM ,  10   SLR ,  10   H2O2  according to the given signal. However, it may be formed in a manner where the flow rate sensors  61   CHM ,  61   SLR ,  61   H2O2 ,  62   CHM ,  62   SLR , and  6214202  detect the pressure of the liquid in the blending flow channel  40 , and the flow-controllers  15   CHM ,  15   SLR , and  15   H2O2  adjust the pressure of the liquid in the flow channels  10   CHM ,  10   SLR ,  10   H2O2  according to the given signal.   (2) The order of blending the plurality of types of liquids in the blending flow channel  40  of the above first embodiment is not limited to that of the first embodiment. For example, the order may be such that the slurry and the chemical are first blended, the hydrogen peroxide water is then blended, and the ultra-pure water is finally blended and diluted.   (3) The number of each of the pressurizing tanks  13   CHM ,  13   SLR , and  13   H2O2  in the above first embodiment may be 2 to 3, or may be 5 or more. Further, the number of the pressurizing tanks  13 A in the above second embodiment may be 2, or may be 4 or more.   (4) The above first embodiment has been formed in a manner where nitrogen is sent to the pressurizing tanks  13   CHM ,  13   SLR , and  13   H2O2 , and the liquid in the pressurizing tanks  13   CHM ,  13   SLR , and  13   H2O2  is pushed out from the pressurizing tanks  13   CHM ,  13   SLR , and  13   H2O2  by the pressure of the nitrogen. However, another inert gas (for example, argon) may be sent to the pressurizing tanks  13   CHM ,  13   SLR , and  13   H2O2 .   (5) The second embodiment has been formed in a manner where nitrogen is sent to the pressurizing tanks  13 A, and the liquid in the pressurizing tank  13 A is pushed out from the pressurizing tank  13 A by the pressure of the nitrogen. However, another inert gas (for example, argon) may be sent to the pressurizing tank  13 A.   (6) In the above first embodiment, it is not necessary to provide an open/close valve in both the inflow port and the outflow port of the pressurizing tanks  13   CHM ,  13   SLR , and  13   H2O2 . It is sufficient that an open/close valve is provided in at least one of the inflow port and the outflow port of the pressurizing tanks  13   CHM ,  13   SLR , and  13   H2O2 , and the PLC 70  as the control means may recursively repeat the control of opening/closing the open/close valve.   (6) In the above second embodiment, it is not necessary to provide an open/close valve in both the inflow port and the outflow port of the pressurizing tanks  13 A. It is sufficient that an open/close valve is provided in at least one of the inflow port and the outflow port of the pressurizing tank  13 A, and the PLC 70  as the control means may recursively repeat the control of opening/closing the open/close valve.   (8) In the above first embodiment, the mixing units  50   CHM ,  50   SLR , and  50   H2O2  were mixing units having a stirring screw SCR accommodated in a cylindrical body, and the stirring screw SCR was a stirring screw having N twist blades VL-k (k=1 to N) arranged at intervals on a shaft rod AXS. However, as the mixing units  50 ′ CHM ,  50 ′ CSLR , and  50 ′ H2O2  shown in  FIG. 5(A)  and  FIG. 5(B) , the stirring screw SCR may be replaced with a mixer in which N (N is a natural number of 2 or more, and in the example of  FIG. 5 , N=4) meshes VL′-k (k=1 to N) are arranged side by side in the hollow cylindrical body extending between the inflow port F 1  and the outflow port F 3  so that mesh orientation of meshes that follow each other is shifted by a predetermined angle (45 degrees in the example of  FIG. 5(B) ).   (9) In the above first and second embodiments, there are liquid inflow ports at the upper portions of the pressurizing tanks  13   CHM ,  13   SLR ,  13   H2O2 , and  13 A, and there are liquid outflow ports at the lower portions of the pressurizing tanks  13   CHM ,  13   SLR ,  13   H2O2 , and  13 A. However, both the liquid inflow ports and the liquid outflow ports may be provided at the lower portions of the pressurizing tanks  13   CHM ,  13   SLR ,  13   H2O2 , and  13 A. For example, as shown in  FIG. 6 , a pipe is provided at the lower portion (bottom portion) of  13   CHM ,  13   SLR ,  13   H2O2 , and  13 A, and the lower portion of this pipe is branched into a T-shape on the liquid inflow side and the liquid outflow side. A first valve VAL 1  may be provided in the pipe on the inflow side and a second valve VAL 2  may be provided in the pipe on the outflow side. Then, the PLC may recursively repeat the control of opening the first valve VAL 1  and closing the second valve VAL 1  to fill the liquid in the pressurizing tanks  13   CHM ,  13   SLR ,  13   H2O2 , and  13 A until the filling amount of the liquid in the pressurizing tanks  13   CHM ,  13   SLR ,  13   H2O2 , and  13 A reaches a predetermined amount (for example, 90%), and closing the first valve VAL 1  and opening the second valve VAL 1  to push out the liquid in the pressurizing tanks  13   CHM ,  13   SLR ,  13   H2O2 , and  13 A by the pressure of nitrogen when the filling amount of the liquid in the pressurizing tanks  13   CHM ,  13   SLR ,  13   H2O2 , and  13 A has reached a predetermined amount.   (10) In the above first embodiment, the configuration is as follows: the flow channel  10   CHM  is connected to the inflow port F 2  of the mixing unit  50   CHM , the flow channel  10   SLR  is connected to the inflow port F 2  of the mixing unit  50   SLR , and the flow channel  10   H2O2  is connected to the inflow port F 2  of the mixing unit  50   H2O2 . However, as shown in  FIG. 7 , it may be configured that the flow channel  10   CHM  is connected to the inflow port F 1  of the mixing unit  50   CHM , the flow channel  10   SLR  is connected to the inflow port F 1  of the mixing unit  50   SLR , and the flow channel  10   H2O2  is connected to the inflow port F 1  of the mixing unit  50   H2O2 .   

     EXPLANATION OF REFERENCE SYMBOLS 
     
         
           14 A gas pressurizing part 
           15 A flow-controller 
           16 A filling amount sensor 
           17 A branching point 
           21  low-pressure value 
           29  ultra-pure water inlet 
           40  blending flow channel 
           40 A flow channel 
           50 A mixing unit 
           51 A case body 
           52 A blending tank 
           59 A stirring device 
           70  PLC 
           79  liquid outlet 
           81  head 
           82  plate 
           83  surface plate 
           84  polishing pad 
           85  nozzle 
           88  wafer 
           89  liquid inlet 
           91  tank 
           92  pump