Patent Publication Number: US-2011062114-A1

Title: Substrate liquid-processing method, substrate liquid-processing apparatus, and storage medium

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2009-215438 filed on Sep. 17, 2009, the entire contents of which are incorporated herein by reference. 
     FIELD OF THE INVENTION 
     The present invention relates to a substrate liquid-processing method, a substrate liquid-processing apparatus and a storage medium for removing a polysilicon film along the circumferential edge of a substrate, such as a semiconductor wafer, provided with the polysilicon film by etching. 
     BACKGROUND OF THE INVENTION 
     In a manufacturing process of a semiconductor device, there is a process for providing a polysilicon film in order to form a gate electrode or the like with respect to a semiconductor wafer (hereinafter, also simply called a wafer) as a processed substrate. However, there is a possibility that cracks and film separation can occur along the circumferential edge, such as the edge and bevel, of the wafer. When such cracks and film separation occur, the polysilicon film may become particles and contaminate the semiconductor device. 
     For this reason, the polysilicon film along the circumferential edge of the wafer has conventionally been removed. When the polysilicon film is removed, an etching method using, as an etching solution, hydrofluoric-nitric acid which is a mixing solution of hydrofluoric acid and nitric acid has hitherto been adopted. Specifically, a portion not to be removed is protected by a protective film (resist and hard mask), and only the circumferential edge (edge and bevel) of the wafer is exposed and the entire wafer into hydrofluoric-nitric acid is immersed. 
     However, such method is required to provide the protective film according to a portion to be etched, with the result that the process becomes troublesome and the number of processes is increased. In addition, the adjustment of the cut width of the polysilicon film is not easy. 
     On the contrary, although it is not the technique of removing a polysilicon film, JP2001-319850A proposes a technique in which after a film is provided over a wafer, a chemical solution is supplied to a bevel portion while the wafer is rotated, to remove the bevel portion by etching. It can be considered to be applied to the etching of the polysilicon film provided along the circumferential edge of the wafer. 
     DISCLOSURE OF THE INVENTION 
     However, if a hydrophobic polysilicon film is provided over a wafer and a hydrophilic natural oxide film is stacked over the polysilicon film, when hydrofluoric-nitric acid is supplied to the circumferential, edge of the wafer using the method disclosed in JP2001-319850A, it is found that the occurrence of etching failure of the polysilicon film cannot be sufficiently prevented and that the accuracy of an etching width is low. 
     An object of the present invention is to provide a substrate liquid-processing method, a substrate liquid-processing apparatus and a storage medium which, when a hydrophobic polysilicon film is provided over a wafer and a hydrophilic natural oxide film is stacked over the polysilicon film, can prevent the occurrence of etching failure along the circumferential edge of the wafer and improve the accuracy of an etching width. 
     The substrate liquid-processing apparatus of the present invention includes: a holding unit configured to hold a substrate; a rotational driving unit configured to rotate the holding unit; a hydrofluoric acid supplying unit configured to supply hydrofluoric acid to the circumferential edge of the substrate held by the holding unit; a hydrofluoric-nitric acid supplying unit configured to supply hydrofluoric-nitric acid to the circumferential edge of the substrate held by the holding unit; and a control unit configured to control the rotational driving unit, the hydrofluoric acid supplying unit, and the hydrofluoric-nitric acid supplying unit, the control unit performing control such that the hydrofluoric acid is supplied to the circumferential edge of the substrate by the hydrofluoric acid supplying unit while the substrate provided with a polysilicon film is rotated, to remove a natural oxide film provided along the circumferential edge of the substrate by etching so as to expose the polysilicon film, and then the hydrofluoric-nitric acid is supplied to the circumferential edge of the substrate by the hydrofluoric-nitric acid supplying unit while the substrate from which the polysilicon film is exposed is rotated, to remove the polysilicon film by etching. 
     In the substrate liquid-processing apparatus of the present invention, the control unit may perform the control of the rotational driving unit so as to rotate the substrate, when the hydrofluoric-nitric acid is supplied to the circumferential edge of the substrate, at a rotation speed lower than that when the hydrofluoric acid is supplied to the circumferential edge of the substrate. 
     In the substrate liquid-processing apparatus of the present invention, the hydrofluoric-nitric acid supplying unit may supply the hydrofluoric-nitric acid to the position outward in the diameter direction of the substrate from the position in which the hydrofluoric acid is supplied to the substrate when the hydrofluoric acid is supplied to the circumferential edge of the substrate by the hydrofluoric acid supplying unit. 
     In this case, the hydrofluoric-nitric acid supplying unit may be positioned outward in the diameter direction of the substrate held by the holding unit from the hydrofluoric acid supplying unit. 
     The substrate liquid-processing method of the present invention uses the substrate liquid-processing apparatus described above and includes: supplying hydrofluoric acid to the circumferential edge of a substrate while the substrate provided with a polysilicon film is rotated, to remove a natural oxide film provided along the circumferential edge of the substrate by etching so as to expose the polysilicon film; and supplying hydrofluoric-nitric acid to the circumferential edge of the substrate while the substrate from which the polysilicon film is exposed is rotated, to remove the polysilicon film by etching. 
     In the substrate liquid-processing method of the present invention, when the hydrofluoric-nitric acid is supplied to the circumferential edge of the substrate, the substrate may be rotated at a rotation speed lower than that when the hydrofluoric acid is supplied to the circumferential edge of the substrate. 
     In the substrate liquid-processing method of the present invention, when the hydrofluoric-nitric acid is supplied to the circumferential edge of the substrate, the hydrofluoric-nitric acid may be supplied to the position outward in the diameter direction of the substrate from the position in which the hydrofluoric acid is supplied to the substrate when the hydrofluoric acid is supplied to the circumferential edge of the substrate. 
     The storage medium of the present invention stores a program capable of being executed by a control computer of the substrate liquid-processing apparatus described above, in which the program is executed so that the control computer controls the substrate liquid-processing apparatus to execute the substrate liquid-processing method, and includes: supplying hydrofluoric acid to the circumferential edge of a substrate while the substrate provided with a polysilicon film is rotated, to remove a natural oxide film provided along the circumferential edge of the substrate by etching so as to expose the polysilicon film; and supplying hydrofluoric-nitric acid to the circumferential edge of the substrate while the substrate from which the polysilicon film is exposed is rotated, to remove the polysilicon film by etching. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic longitudinal sectional view of a substrate liquid-processing apparatus according to an embodiment of the present invention; 
         FIG. 2  is a control block diagram of the substrate liquid-processing apparatus shown in  FIG. 1 ; 
         FIG. 3  is a flowchart showing a wafer processing method by the substrate liquid-processing apparatus shown in  FIG. 1 ; and 
         FIGS. 4A ,  4 B, and  4 C are explanatory views each showing a region on the surface of a wafer, to which each chemical solution or a rinse solution is supplied, by the wafer processing method shown in  FIG. 3 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Hereinafter, an embodiment of the present invention will be described with reference to the drawings.  FIGS. 1 to 4C  are diagrams showing a substrate liquid-processing apparatus and a substrate liquid-processing method according to this embodiment. More specifically,  FIG. 1  is a schematic longitudinal sectional view of the substrate liquid-processing apparatus according to this embodiment, and  FIG. 2  is a control block diagram of the substrate liquid-processing apparatus shown in  FIG. 1 . In addition,  FIG. 3  is a flowchart showing a wafer processing method by the substrate liquid-processing apparatus shown in  FIG. 1 . Further,  FIGS. 4A to 4C  are explanatory views each showing a region on the surface of a wafer, to which each chemical solution or a rinse solution is supplied, by the wafer processing method shown in  FIG. 3 . 
     As shown in  FIG. 1 , a substrate liquid-processing apparatus  1  has a holding unit  10  which holds a substrate W (hereinafter, also called a wafer W), such as a semiconductor wafer, into a substantially horizontal state, a rotational shaft  12  extending downward from the holding unit  10 , and a rotational driving unit  20  which rotates the holding unit  10  via the rotational shaft  12 . The holding unit  10  holds the wafer W placed on the holding unit  10  by, e.g., vacuum absorption. 
     As shown in  FIG. 1 , the rotational shaft  12  extends in the vertical direction. The rotational driving unit  20  has a pulley  24  arranged outward of the circumferential edge of the lower end of the rotational shaft  12 , a driving belt  26  entrained on the pulley  24 , and a motor  22  which rotates the rotational shaft  12  via the pulley  24  by applying a driving force to the driving belt  26 . In addition, a bearing  14  is arranged outward of the circumferential edge of the rotational shaft  12  in the position above the pulley  24 . 
     A chamber  2  covering the wafer W is provided around the wafer W held by the holding unit  10 . An upper opening  4  which sends a gas, such as an N2 gas (nitrogen gas) or the like, to the wafer W by downflow is formed in the upper portion (ceiling portion) of the chamber  2 . In addition, lower openings  5  for exhausting the gas sent from the upper opening  4  by downflow from the inside of the chamber  2  are formed in the lower portion (bottom portion) of the chamber  2 . Further, a side opening  3  for passing a transferring arm which transfers the wafer W into the chamber  2  or transfers out the wafer W from the inside of the chamber  2  is formed in the side portion of the chamber  2 . The side opening  3  can be opened and closed by a shutter  3   a  provided to the side opening  3 . 
     As shown in  FIG. 1 , nozzles  30 ,  33 , and  36  for supplying each chemical solution and a rinse solution to the circumferential edge of the wafer W held by the holding unit  10  are integrally provided in parallel. More specifically, of the three nozzles  30 ,  33 , and  36 , the hydrofluoric-nitric acid supplying nozzle  30  located on the outermost side (the furthest side from the center of the wafer W) in the diameter direction of the wafer W supplies hydrofluoric-nitric acid to the circumferential edge of the wafer W held by the holding unit  10 . Of the three nozzles  30 ,  33 , and  36 , the hydrofluoric acid supplying nozzle  33  located on the inner side from the hydrofluoric-nitric acid supplying nozzle  30  in the diameter direction of the wafer W supplies hydrofluoric acid to the circumferential edge of the wafer W held by the holding unit  10 . Of the three nozzles  30 ,  33 , and  36 , the rinse solution supplying nozzle  36  located on the innermost side (the nearest side from the center of the wafer W) in the diameter direction of the wafer W supplies a rinse solution, such as pure water, to the circumferential edge of the wafer W held by the holding unit  10 . 
     A hydrofluoric-nitric acid supplying source  32  is connected via a hydrofluoric-nitric acid supplying pipe  31  to the hydrofluoric-nitric acid supplying nozzle  30 , thereby supplying the hydrofluoric-nitric acid from the hydrofluoric-nitric acid supplying source  32  via the hydrofluoric-nitric acid supplying pipe  31  to the hydrofluoric-nitric acid supplying nozzle  30 . In addition, a valve  31   a  which controls the presence or absence of supplying and the supplying amount of the hydrofluoric-nitric acid to the hydrofluoric-nitric acid supplying nozzle  30  is provided to the hydrofluoric-nitric acid supplying pipe  31 . The hydrofluoric-nitric acid supplying nozzle  30 , the hydrofluoric-nitric acid supplying pipe  31 , the valve  31   a , and the hydrofluoric-nitric acid supplying source  32  configure a hydrofluoric-nitric acid supplying unit  52  which supplies the hydrofluoric-nitric acid to the circumferential edge of the wafer W held by the holding unit  10 . 
     A hydrofluoric acid supplying source  35  is connected via a hydrofluoric acid supplying pipe  34  to the hydrofluoric acid supplying nozzle  33 , thereby supplying the hydrofluoric acid from the hydrofluoric acid supplying source  35  via the hydrofluoric acid supplying pipe  34  to the hydrofluoric acid supplying nozzle  33 . In addition, a valve  34   a  which controls the presence or absence of supplying and the supplying amount of the hydrofluoric acid to the hydrofluoric acid supplying nozzle  33  is provided to the hydrofluoric acid supplying pipe  34 . The hydrofluoric acid supplying nozzle  33 , the hydrofluoric acid supplying pipe  34 , the valve  34   a , and the hydrofluoric acid supplying source  35  configure a hydrofluoric acid supplying unit  54  which supplies the hydrofluoric acid to the circumferential edge of the wafer W held by the holding unit  10 . 
     A rinse solution supplying source  38  is connected via a rinse solution supplying pipe  37  to the rinse solution supplying nozzle  36 , thereby supplying the rinse solution, such as pure water, from the rinse solution supplying source  38  via the rinse solution supplying pipe  37  to the rinse solution supplying nozzle  36 . In addition, a valve  37   a  which controls the presence or absence of supplying and the supplying amount of the rinse solution to the rinse solution supplying nozzle  36  is provided to the rinse solution supplying pipe  37 . The rinse solution supplying nozzle  36 , the rinse solution supplying pipe  37 , the valve  37   a , and the rinse solution supplying source  38  configure a rinse solution supplying unit  56  which supplies the rinse solution, such as pure water, to the circumferential edge of the wafer W held by the holding unit  10 . 
     A nozzle driving mechanism  39  is provided on the three nozzles  30 ,  33 , and  36  integrally provided in parallel. The three nozzles  30 ,  33 , and  36  are integrally moved by the nozzle driving mechanism  39 . 
     As shown in  FIG. 2 , a control unit  50  which controls each component of the substrate liquid-processing apparatus  1  is provided in the substrate liquid-processing apparatus  1 . Specifically, the control unit  50  is connected to the holding unit  10 , the rotational driving unit  20 , the hydrofluoric-nitric acid supplying unit  52 , the hydrofluoric acid supplying unit  54 , the rinse solution supplying unit  56 , and the nozzle driving mechanism  39 . The control unit  50  transmits a control signal to each component connected to the control unit  50  to control each component. The specific contents of the control of each component by the control unit  50  will be described below. 
     In this embodiment, the control unit  50  is connected to a storage medium  60  which stores a control program for realizing each process executed by the substrate liquid-processing apparatus  1  by the control of the control unit  50 , and a program (or a recipe) for allowing each component of the substrate liquid-processing apparatus  1  to execute a process according to the processing conditions. The storage medium  60  can have a memory such as a ROM or a RAM, a hard disk, a disc-like storage medium such as a CD-ROM or a DVD-ROM, and other known storage medium. The arbitrary recipe is called from the storage medium  60  so as to be executed by the control unit  50 , if necessary, so that a desired process in the substrate liquid-processing apparatus  1  is performed under the control of the control unit  50 . 
     An operation (the processing method of the wafer W) of the substrate liquid-processing apparatus  1  described above will be described with reference to the flowchart shown in  FIG. 3  and the explanatory views shown in  FIGS. 4A to 4C . It should be noted that the operation of the substrate liquid-processing apparatus  1  is performed by controlling each component of the substrate liquid-processing apparatus  1  by the control unit  50  according to the program (recipe) stored in the storage medium  60 . 
     First, the wafer W is transferred from the outside of the substrate liquid-processing apparatus  1  via the side opening  3  of the chamber  2  into the chamber  2  by the transferring arm, not shown. Specifically, the wafer W is placed on the holding unit  10  in the chamber  2  by the transferring arm (see STEP  1  of  FIG. 3 ). Here, a polysilicon film and a natural oxide film are provided in the stacked state over the surface of the wafer W placed on the holding unit  10  by the transferring arm (more specifically, the polysilicon film is provided over the surface of the wafer W, and the natural oxide film is stacked over the polysilicon film). It should be noted that the polysilicon film is hydrophobic and the natural oxide film is hydrophilic. 
     Next, the rotational shaft  12  is rotated about an axis extending in the vertical direction by the rotational driving unit  20 . As a result, the wafer W held by the holding unit  10  is rotated. At this time, the rotational shaft  12  is rotated by applying a driving force from the motor  22  via the driving belt  26  to the pulley  24 . 
     In the state that the wafer W held by the holding unit  10  is rotated, the hydrofluoric acid is supplied to the circumferential edge of the wafer W by the hydrofluoric acid supplying unit  54 . Specifically, the hydrofluoric acid is supplied from the hydrofluoric acid supplying source  35  via the hydrofluoric acid supplying pipe  34  to the hydrofluoric acid supplying nozzle  33  to discharge the hydrofluoric acid from the hydrofluoric acid supplying nozzle  33  to the circumferential edge of the wafer W. At this time, the wafer W is rotated at a high speed (e.g., 1000 rpm). As a result, the natural oxide film provided along the circumferential edge of the wafer W is removed by etching (see STEP  2  of  FIG. 3 ). In this manner, the polysilicon film provided over the wafer W is exposed. As the advantage of rotating the wafer W at a high speed, the control of an etching width with respect to the natural oxide film can be easily performed at high accuracy. The hydrofluoric acid supplied to the surface of the wafer W is flowed outward in the circumferential direction from the wafer W by a centrifugal force of the rotation of the wafer W. 
     In the process for supplying the hydrofluoric acid to the circumferential edge of the wafer W by the hydrofluoric acid supplying unit  54 , the region on the wafer W, to which the hydrofluoric acid is supplied, is a region indicated by the reference numeral  40  of  FIG. 4A . 
     The concentration of the hydrofluoric acid supplied from the hydrofluoric acid supplying unit  54  to the circumferential edge of the wafer W is set to a concentration at which the natural oxide film can be etched for a short time and the polysilicon film can be exposed completely. Specifically, the concentration of the hydrofluoric acid is set to a magnitude within the range of, e.g., 1 to 50%. Therefore, when the hydrofluoric acid is supplied from the hydrofluoric acid supplying unit  54  to the circumferential edge of the wafer W, only the natural oxide film is removed without removing the polysilicon film. 
     Next, in the state that the wafer W held by the holding unit  10  is rotated, the hydrofluoric-nitric acid is supplied to the circumferential edge of the wafer W by the hydrofluoric-nitric acid supplying unit  52 . Specifically, the hydrofluoric-nitric acid is supplied from the hydrofluoric-nitric acid supplying source  32  via the hydrofluoric-nitric acid supplying pipe  31  to the hydrofluoric-nitric acid supplying nozzle  30  to discharge the hydrofluoric-nitric acid from the hydrofluoric-nitric acid supplying nozzle  30  to the circumferential edge of the wafer W. As a result, the polysilicon film provided along the circumferential edge of the wafer W is removed by etching (see STEP  3  of  FIG. 3 ). The hydrofluoric-nitric acid supplied to the surface of the wafer W is flowed outward in the circumferential direction from the wafer W by the centrifugal force of the rotation of the wafer W. 
     It should be noted that the hydrofluoric-nitric acid supplying nozzle  30  is arranged outward of the hydrofluoric acid supplying nozzle  33  in the diameter direction of the wafer W held by the holding unit  10 . For this reason, when the hydrofluoric-nitric acid is supplied to the circumferential edge of the wafer W, the hydrofluoric-nitric acid is supplied to the position outward in the diameter direction of the wafer W from the position in which the hydrofluoric acid is supplied to the wafer W when the hydrofluoric acid is supplied to the circumferential edge of the wafer W. Therefore, when the hydrofluoric-nitric acid is supplied to the circumferential edge of the wafer W, the hydrofluoric-nitric acid is supplied into the region  40  along the circumferential edge of the wafer W, to which the hydrofluoric acid is supplied (see  FIG. 4A ), that is, into the hydrophobic plane of the polysilicon film.  FIG. 4B  shows a region on the wafer W, to which the hydrofluoric-nitric acid is supplied, indicated by the reference numeral  41 . As shown in  FIG. 4B , the region  41  on the wafer W, to which the hydrofluoric-nitric acid is supplied, is included in the region  40  on the wafer W, to which the hydrofluoric acid is supplied. 
     When the hydrofluoric-nitric acid is supplied to the circumferential edge of the wafer W, the wafer W is rotated at a rotation speed lower than that when the hydrofluoric acid is supplied to the circumferential edge of the wafer W, as shown in STEP  2  of  FIG. 3 . More specifically, the wafer W is rotated at e.g., 300 rpm. As the wafer W is rotated at a low speed in this manner, the time during which the polysilicon film provided along the circumferential edge of the wafer W is contacted becomes longer, whereby the occurrence of partial etching failure along the circumferential edge of the wafer W can be prevented. For this reason, the partial remaining of the polysilicon film along the circumferential edge of the wafer W after the etching process is performed can be prevented. In addition, as the advantage of rotating the wafer W at a low speed, as the polysilicon film is hydrophobic, the hydrofluoric-nitric acid cannot enter into the center side of the wafer W at the time of the supply of the hydrofluoric-nitric acid to the circumferential edge of the wafer W and the hydrofluoric-nitric acid can be contacted for a long time owing to a low speed. According to an experiment of the present inventors, when the rotation speed of the wafer W is relatively high (specifically, when the rotation speed of the wafer W is e.g., 500 rpm or more), the time during which the hydrofluoric-nitric acid is contacted with the polysilicon film provided along the circumferential edge of the wafer W becomes shorter. Therefore, it is found that etching failure partially occurs along the circumferential edge of the wafer W and that the polysilicon film partially remains along the circumferential edge of the wafer W even after the etching process is performed. 
     Next, in the state that the wafer W held by the holding unit  10  is rotated, the rinse solution, such as pure water, is supplied to the circumferential edge of the wafer W by the rinse solution supplying unit  56 . Specifically, the rinse solution is supplied from the rinse solution supplying source  38  via the rinse solution supplying pipe  37  to the rinse solution supplying nozzle  36  to discharge the rinse solution from the rinse solution supplying nozzle  36  to the circumferential edge of the wafer W. At this time, the wafer W is rotated at a high speed (e.g., 1000 rpm). Therefore, the rinse process of the circumferential edge of the wafer W (see STEP  4  of  FIG. 3 ) is performed. The rinse solution supplied to the surface of the wafer W is flowed outward in the circumferential direction from the wafer W by the centrifugal force of the rotation of the wafer W. 
     It should be noted that the rinse solution supplying nozzle  36  is arranged inward of the hydrofluoric-nitric acid supplying nozzle  30  and the hydrofluoric acid supplying nozzle  33  in the diameter direction of the wafer W held by the holding unit  10 . Therefore, when the rinse solution is supplied to the circumferential edge of the wafer W, the rinse solution is supplied to the position inward in the diameter direction of the wafer W from the position in which the hydrofluoric-nitric acid or the hydrofluoric acid is supplied to the wafer W. As a result, all the hydrofluoric-nitric acid and the hydrofluoric acid adhering to the circumferential edge of the wafer W are washed away by the rinse solution so that the rinse process of the wafer W can be reliably performed. It should be noted that in the process for supplying the rinse solution to the circumferential edge of the wafer W by the rinse solution supplying unit  56  to perform the rinse process of the wafer W, the region on the wafer W, to which the rinse solution is supplied, is a region, indicated by the reference numeral  42  of  FIG. 4C . 
     Thereafter, the wafer W held by the holding unit  10  is continued to be rotated at a high speed to perform the drying process of the wafer W (see STEP  5  of  FIG. 3 ). 
     Finally, the transferring arm is put into the chamber  2  via the side opening  3  of the chamber  2 , the wafer W is taken out from the holding unit  10  by the transferring arm, and the taken-out wafer W is transferred to the outside of the substrate liquid-processing apparatus  1  (see STEP  6  of  FIG. 3 ). In this manner, a series of processes of the wafer W are completed. 
     As described above, according to the substrate liquid-processing apparatus  1  and the substrate liquid-processing method of this embodiment, the hydrofluoric acid is supplied to the circumferential edge of the wafer W while the wafer W provided with the polysilicon film is rotated, to remove the natural oxide film provided along the circumferential edge of the wafer W by etching so as to expose the polysilicon film (see STEP  2  of  FIG. 3 ), and then the hydrofluoric-nitric acid is supplied to the circumferential edge of the wafer W while the wafer W from which the polysilicon film is exposed is rotated, to remove the polysilicon film by etching (see STEP  3  of  FIG. 3 ). It should be noted that the above operation is performed by controlling the rotational driving unit  20 , the hydrofluoric acid supplying unit  54 , and the hydrofluoric-nitric acid supplying unit  52  by the control unit  50  of the substrate liquid-processing apparatus  1 . According to the substrate liquid-processing apparatus  1  and the substrate liquid-processing method, the hydrofluoric acid is first supplied to the circumferential edge of the wafer W so that the hydrophilic natural oxide film provided along the circumferential edge of the wafer W can be removed by etching so as to expose the hydrophobic polysilicon film along the circumferential edge of the wafer W. Therefore, when hydrofluoric-nitric acid is supplied to the circumferential edge of the wafer W, the erosion of the hydrofluoric-nitric acid toward the center of the wafer W can be prevented. As a result, the accuracy of the etching width can be improved. In addition, when the erosion of the hydrofluoric-nitric acid toward the center of the wafer W can be prevented, the wafer W can be rotated at a low speed at the time of the supply of the hydrofluoric-nitric acid to the circumferential edge of the wafer W. Then, the occurrence of partial etching failure along the circumferential edge of the wafer W can be prevented. 
     According to the substrate liquid-processing apparatus  1  and the substrate liquid-processing method of this embodiment, when the hydrofluoric-nitric acid is supplied to the circumferential edge of the wafer W, the wafer W is rotated at a rotation speed lower than that when the hydrofluoric acid is supplied to the circumferential edge of the wafer W. Specifically, the rotation speed when the hydrofluoric acid is supplied to the circumferential edge of the wafer W is 500 rpm or more, more specifically, e.g., 1000 rpm, whereas the rotation speed of the wafer W when the hydrofluoric-nitric acid is supplied to the circumferential edge of the wafer W is e.g., 300 rpm. As the wafer W is rotated at a low speed when the hydrofluoric-nitric acid is supplied to the circumferential edge of the wafer W in this manner, the time during which the hydrofluoric-nitric acid is contacted with the polysilicon film provided along the circumferential edge of the wafer W can be longer. Therefore, the occurrence of partial etching failure along the circumferential edge of the wafer W can be prevented. For this reason, the partial remaining of the polysilicon film along the circumferential edge of the wafer W after the etching process is performed can be prevented. 
     In addition, according to the substrate liquid-processing apparatus  1  and the substrate liquid-processing method of this embodiment, when the hydrofluoric-nitric acid is supplied to the circumferential edge of the wafer W, the hydrofluoric-nitric acid is supplied to the region along the circumferential edge of the wafer W, to which the hydrofluoric acid is already supplied (see  FIGS. 4A and 4B ). More specifically, the hydrofluoric-nitric acid supplying nozzle  30  of the hydrofluoric-nitric acid supplying unit  52  is arranged outward in the diameter direction of the wafer W held by the holding unit  10  from the hydrofluoric acid supplying nozzle  33  of the hydrofluoric acid supplying unit  54 . For this reason, when the hydrofluoric-nitric acid is supplied to the circumferential edge of the wafer W, the hydrofluoric-nitric acid is supplied to the position outward in the diameter direction of the wafer W from the position in which the hydrofluoric acid is supplied to the wafer W (the position in which the hydrofluoric acid is supplied from the hydrofluoric acid supplying nozzle  33  to the wafer W) when the hydrofluoric acid is supplied to the circumferential edge of the wafer W. As a result, the hydrofluoric-nitric acid can be reliably supplied to the position on the surface of the wafer W, in which the natural oxide film is removed to expose the polysilicon film. In addition, at this time, the hydrofluoric-nitric acid is reliably supplied into the hydrophobic plane on the surface of the wafer W. Therefore, the erosion of the hydrofluoric-nitric acid toward the center of the wafer W can be prevented more reliably. 
     Further, the concentration of the hydrofluoric acid supplied to the circumferential edge of the wafer W is set to a concentration at which the natural oxide film can be etched for a short time and the polysilicon film can be completely exposed. For this reason, when the hydrofluoric acid is supplied to the circumferential edge of the wafer W, only the natural oxide film provided over the surface of the wafer W can be removed. Then, the surface of the wafer W can be reliably brought into the hydrophobic state. 
     The substrate liquid-processing apparatus and the substrate liquid-processing method of this embodiment are not limited to the above embodiment and various changes can be added. For instance, the hydrofluoric-nitric acid supplying nozzle  30 , the hydrofluoric acid supplying nozzle  33 , and the rinse solution supplying nozzle  36  are not required to be integrally provided. In other words, the nozzles  30 ,  33 , and  36  may also be driven independently.