JP2016181610A - Substrate cleaning method and substrate cleaning device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To excellently clean one principal plane by supplying the one principal plane of a substrate held by the substrate holding part facing a substrate holding part with an ultrasonic wave application liquid having sufficient energy.SOLUTION: The substrate cleaning method for cleaning one principal plane of a substrate held by a substrate holding part provided by facing the one principal plane of the substrate includes: an ultrasonic wave application liquid supply step of generating an ultrasonic wave application liquid by applying an ultrasonic wave to a deaerated liquid, which is a deaerated liquid, at an ultrasonic wave application position on the opposite side of the substrate with respect to the substrate holding part and supplying the ultrasonic wave application liquid toward one principal plane; and a cleaning step of cleaning the one principal plane with the ultrasonic wave application liquid after increasing dissolved gas concentration of the ultrasonic wave application liquid at a position closer to the one principal plane than the ultrasonic wave application position.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a substrate cleaning method and apparatus for cleaning one main surface of a substrate. The substrate includes a semiconductor wafer, a glass substrate for photomask, a glass substrate for liquid crystal display, a glass substrate for plasma display, a substrate for FED (Field Emission Display), an optical disk substrate, a magnetic disk substrate, and a magneto-optical disk. Various substrates such as a substrate are included.

  The manufacturing process of an electronic component such as a semiconductor device or a liquid crystal display device includes a process of forming a fine pattern by repeatedly performing processes such as film formation and etching on the surface of a substrate. Here, if particles adhere to the back surface of the substrate, this becomes a defocus factor in the photolithography process, and it becomes difficult to form a desired fine pattern. Further, cross contamination may occur due to the substrate having particles attached to the back surface. Furthermore, when the substrate is transported, the back surface of the substrate is often vacuum-sucked, and in the process, particles may adhere to the back surface of the substrate. Therefore, many techniques for cleaning the back surface of the substrate have been proposed. For example, the apparatus described in Patent Document 1 performs ultrasonic cleaning on the back surface of the substrate by supplying an ultrasonic application liquid in which ultrasonic waves are applied to the liquid toward the center of the back surface of the substrate.

JP 2010-27816 A

  By the way, in the apparatus described in Patent Document 1, the ultrasonic nozzle is positioned in the vicinity of the outside in the radial direction of the spin base, which is the main configuration of the substrate holding unit that holds the substrate, and at a position lower than the back surface Wb of the substrate. . For this reason, the distance from the ultrasonic nozzle to the center of the back surface of the substrate is relatively long, and when the cavitation occurs in the liquid and reaches the center of the back surface, In some cases, the energy was significantly attenuated. In this case, a sufficient cleaning effect cannot be obtained.

  Therefore, it is desirable to dispose the ultrasonic nozzle near the back surface of the substrate to solve the above problem. However, in the apparatus described in Patent Document 1, since the substrate is held by a spin chuck, the nozzle arrangement is practically impossible. That is, in order to clean the back surface of the substrate, the substrate is held so that the back surface of the substrate faces the spin base at a minute distance from the spin base of the spin chuck. For this reason, it is practically difficult to dispose the ultrasonic nozzle in the vicinity of the back surface of the substrate, and it is necessary to dispose the ultrasonic nozzle on the opposite side of the substrate with respect to the substrate holding portion. There is a problem that ultrasonic energy is attenuated between the time when the ultrasonic application liquid is supplied to the back surface and sufficient cavitation cannot be obtained on the back surface of the substrate.

  The present invention has been made in view of the above-described problems, and an ultrasonic application liquid having sufficient energy is supplied to one main surface facing the substrate holding portion of the substrate held by the substrate holding portion, and the one main surface is formed. It is an object of the present invention to provide a substrate cleaning method and a substrate cleaning apparatus that can clean well.

  One aspect of the present invention is a substrate cleaning method for cleaning one main surface of a substrate held by a substrate holding portion provided opposite to the one main surface of the substrate, the opposite side of the substrate with respect to the substrate holding portion An ultrasonic application liquid supply process for generating ultrasonic application liquid by applying ultrasonic waves to a degassed liquid that has been degassed at the ultrasonic application position, and supplying the ultrasonic application liquid toward the main surface, and ultrasonic application And a cleaning step of cleaning the one main surface with the ultrasonic application liquid after increasing the dissolved gas concentration of the ultrasonic application liquid at a position closer to the one main surface than the position.

  According to another aspect of the present invention, there is provided a substrate cleaning apparatus, a substrate holding unit that is provided opposite to one main surface of the substrate and holds the substrate, and a substrate holding unit that is opposite to the substrate with respect to the substrate holding unit. From the ultrasonic application position, an ultrasonic application liquid supply unit that generates ultrasonic application liquid by applying ultrasonic waves to the degassed liquid that has been degassed at the sound wave application position, and is supplied from the ultrasonic application position. And a concentration adjusting unit that adjusts so that the dissolved gas concentration of the ultrasonic wave application liquid increases at a position close to the one main surface, and the ultrasonic wave application liquid whose dissolved gas concentration is adjusted by the concentration adjusting unit It is characterized by washing.

  According to the present invention, the ultrasonic wave application liquid is generated by applying ultrasonic waves to the degassed liquid at the ultrasonic wave application position, but the ultrasonic wave application liquid is not directly supplied to one main surface of the substrate. Rather, the dissolved gas concentration is increased at a position closer to the one main surface than the ultrasonic wave application position (hereinafter referred to as “substrate proximity position”) and then supplied to the one main surface of the substrate. Therefore, during the period from the generation of the ultrasonic application liquid to the position close to the substrate, the ultrasonic application liquid (= deaeration liquid + ultrasonic wave) suppresses the occurrence of cavitation, thereby suppressing the ultrasonic energy attenuation. On the other hand, at the position close to the substrate, the ultrasonic wave application liquid has ultrasonic waves that have escaped energy attenuation and many dissolved gases, and the ultrasonic wave application liquid in such a state is supplied to one main surface of the substrate. . Therefore, many cavitations occur on or near the main surface. As a result, it is possible to satisfactorily clean the one main surface of the substrate, even though the ultrasonic application liquid is generated at the ultrasonic wave application position away from the one main surface of the substrate.

It is a figure which shows 1st Embodiment of the board | substrate cleaning apparatus concerning this invention. It is a partial top view of the apparatus shown in FIG. It is a block diagram which shows the electric constitution of the apparatus shown in FIG. It is a flowchart which shows operation | movement of the board | substrate cleaning apparatus shown in FIG. It is a figure which shows typically operation | movement of the board | substrate cleaning apparatus shown in FIG. It is a figure which shows 2nd Embodiment of the board | substrate cleaning apparatus concerning this invention. It is a figure which shows 3rd Embodiment of the board | substrate cleaning apparatus concerning this invention. It is a figure which shows 4th Embodiment of the board | substrate cleaning apparatus concerning this invention. It is a figure which shows 5th Embodiment of the board | substrate cleaning apparatus concerning this invention. It is a figure which shows 6th Embodiment of the board | substrate cleaning apparatus concerning this invention.

  FIG. 1 is a view showing a first embodiment of a substrate cleaning apparatus according to the present invention. FIG. 2 is a partial plan view of the apparatus shown in FIG. FIG. 3 is a block diagram showing an electrical configuration of the apparatus shown in FIG. The substrate cleaning apparatus 1 adheres to the back surface Wb of a substrate W such as a semiconductor wafer by an ultrasonic wave application liquid in which ultrasonic waves are applied to the liquid while holding the substrate W with the front surface Wf of the substrate W facing up. This is an apparatus for removing unnecessary substances such as particles (reference numeral PT in FIG. 5). More specifically, DIW (deionized water) is used as the liquid, and an ultrasonic application liquid in which an ultrasonic wave is applied to DIW is supplied to the back surface Wb of the substrate W to clean the back surface. It is an apparatus that spin-drys the substrate W wet with DIW after the treatment. Although not shown in the drawings, a device pattern made of poly-Si or the like is formed on the surface Wf of the substrate W.

  The substrate cleaning apparatus 1 includes a spin chuck 10 that rotates the substrate W while holding the substrate W in a substantially horizontal posture with the surface Wf of the substrate W facing upward. The spin chuck 10 has a rotation support shaft 11 connected to a rotation support shaft of a chuck rotation mechanism 31 including a motor, and can rotate around a rotation axis J (vertical axis) by driving the chuck rotation mechanism 31. A disc-shaped spin base 12 is integrally connected to the upper end portion of the rotary spindle 11 by a fastening component such as a screw. Accordingly, the spin base 12 rotates around the rotation axis J when the chuck rotation mechanism 31 operates in accordance with an operation command from the control unit 30 that controls the entire apparatus. Further, the control unit 30 controls the chuck rotating mechanism 31 to adjust the rotation speed.

  Near the periphery of the spin base 12, a plurality of chuck pins 13 for holding the periphery of the substrate W are provided upright. A plurality of chuck pins 13 may be provided in order to securely hold the circular substrate W, and are equiangularly spaced with respect to the rotation center (rotation axis J) of the substrate W along the peripheral edge of the spin base 12. Has been placed. In this embodiment, three chuck pins 13 are provided as shown in FIG.

  Each of the chuck pins 13 includes a substrate support portion that supports the peripheral portion of the substrate W from below, and a substrate holding portion that holds the substrate W by pressing the outer peripheral end surface of the substrate W supported by the substrate support portion. Yes. Each chuck pin 13 is configured to be switchable between a pressing state in which the substrate holding portion presses the outer peripheral end surface of the substrate W and a released state in which the substrate holding portion is separated from the outer peripheral end surface of the substrate W.

  When the substrate W is delivered to the spin base 12, the plurality of chuck pins 13 are released, and when the substrate W is subjected to the cleaning process, the plurality of chuck pins 13 are pressed. To do. By setting the pressed state, the plurality of chuck pins 13 can grip the peripheral portion of the substrate W and hold the substrate W in a substantially horizontal position at an upper position spaced apart from the spin base 12. Thus, the substrate W is supported in a state where the front surface (pattern forming surface) Wf faces upward and the back surface Wb faces downward, that is, in a face-up state. As described above, in this embodiment, the back surface Wb of the substrate W is held by the spin chuck 10 in a state of being opposed to the spin base 12 of the spin chuck 10 while being separated by a predetermined distance in the vertical direction.

  The spin chuck 10 holding the substrate W is rotated by the chuck rotating mechanism 31 to rotate the substrate W at a predetermined number of rotations, and from the lower side of the substrate W to the central portion of the back surface Wb of the substrate W, the substrate DIW is supplied from the outside of W to the peripheral portion of the back surface Wb of the substrate W and from the upper side of the substrate W to the center portion of the front surface Wf of the substrate W to perform a cleaning process.

  In this embodiment, the rotating spindle 11 is finished in a hollow shape, and a supply pipe 14 for supplying the ultrasonic application liquid toward the back surface Wb is inserted into the hollow portion 11 a of the rotating spindle 11. The supply tube 14 extends to the upper surface of the spin base 12, and its end surface faces the center of the back surface Wb of the substrate W. That is, the upper end portion of the supply pipe 14 functions as the nozzle port 141. On the other hand, the lower end portion of the supply pipe 14 is connected to an ultrasonic nozzle 50 d that generates an ultrasonic wave application liquid to be supplied to the center of the back surface of the substrate W.

  As shown in FIG. 1, the ultrasonic nozzle 50 d is disposed at the ultrasonic wave application position P <b> 1 on the opposite side of the substrate W with respect to the spin chuck 10 that holds the substrate W, that is, vertically below, and the valve 41 and the degassing mechanism 42. Is connected to a DIW supply source via a pipe. As this DIW supply source, the utility provided in the factory where the apparatus 1 is installed may be used. Of course, a DIW storage tank may be provided in the apparatus 1 and used as a DIW supply source.

  When the degassing mechanism 42 removes dissolved gas from the DIW sent from the DIW supply source, that is, when degassing treatment is performed to lower the concentration of dissolved gas in the DIW, an ultrasonic wave is applied to the DIW as described below. Even so, the occurrence of cavitation in the DIW can be suppressed. Here, the DIW that has been degassed to reduce the cavitation strength is referred to as a “cavitation suppressing liquid”, and its technical significance will be described in detail later.

  When the valve control mechanism 32 gives an opening command to the valve 41, the valve 41 is opened, and the cavitation suppression liquid (degassed liquid) pumped from the degassing mechanism 42 is sent into the nozzle through the inlet 51d. Further, the cavitation suppression liquid is applied with ultrasonic waves to become an ultrasonic wave application liquid, and is discharged from the discharge port 52 d toward the center of the back surface of the substrate W through the supply pipe 14. More specifically, in the ultrasonic nozzle 50d, the vibrator 53d is disposed on the opposite side of the discharge port 52d in the discharge direction of the cavitation suppression liquid discharged from the discharge port 52d as shown in FIG. Then, when an oscillation signal is output from the oscillator 60 to the vibrator 53d in the ultrasonic nozzle 50d based on the control signal from the control unit 30, the vibrator 53d vibrates and generates an ultrasonic wave. On the other hand, when the valve 41 is closed in response to a closing command from the valve control mechanism 32, the pumping of the cavitation suppression liquid to the ultrasonic nozzle 50d is stopped, and the supply of the ultrasonic application liquid is also stopped.

  In this embodiment, an ultrasonic nozzle 50s is provided in addition to the ultrasonic nozzle 50d. The ultrasonic nozzle 50s is greatly different from the ultrasonic nozzle 50d in the arrangement position and the type of the target liquid to which the ultrasonic wave is applied, and the basic structure is the same. That is, the ultrasonic nozzle 50 s is fixedly disposed in the vicinity of the radially outer side (the left-hand side in the figure) of the chuck pin 13 as shown in FIGS. 1 and 2, and is connected via the valve 43 and the gas concentration adjusting mechanism 44. Pipe connected to DIW supply.

  The gas concentration adjusting mechanism 44 has a function of dissolving a gas such as nitrogen gas in DIW supplied from a DIW supply source to increase the gas concentration in the DIW to a saturation level, thereby creating a gas-rich DIW. ing. As a specific configuration, for example, the one described in JP-A-2004-79990 can be used. When the dissolved gas concentration in DIW is increased in this way, the generation and disappearance of bubbles, that is, cavitation is promoted by application of ultrasonic waves to DIW, and an excellent cleaning effect is obtained. Therefore, in the present embodiment, in order to obtain the above cleaning effect, a gas rich DIW (hereinafter referred to as “cavitation promoting liquid”) is generated. When the valve control mechanism 32 gives an opening command to the valve 43, the valve 43 is opened and the cavitation promoting liquid pumped from the gas concentration adjusting mechanism 44 is sent into the nozzle through the inlet 51s of the ultrasonic nozzle 50s. In response to the application of ultrasonic waves, the liquid becomes an ultrasonic wave application liquid, and is discharged from the discharge port 52s toward the peripheral edge of the back surface of the substrate W, and applied to the entire back surface Wb of the substrate W (= cavitation promoting liquid + ultrasonic wave). The liquid film can be formed. In the ultrasonic nozzle 50s, the vibrator 53s is arranged on the opposite side of the discharge port 52s in the discharge direction of the cavitation promoting liquid discharged from the discharge port 52s as shown in FIG. When the oscillation signal is output from the oscillator 60 to the vibrator 53s based on the control signal from the control unit 30, the vibrator 53s vibrates to generate an ultrasonic wave. On the other hand, when the valve 41 is closed in response to a closing command from the valve control mechanism 32, the pumping of the cavitation suppression liquid to the ultrasonic nozzle 50s is stopped, and the supply of the ultrasonic application liquid is also stopped.

  As described above, in the present embodiment, two types of ultrasonic nozzles 50d and 50s are provided, and two types of ultrasonic application liquids, that is, the ultrasonic waves supplied to the central portion of the back surface Wb are provided on the back surface Wb of the substrate W. A sonication application liquid (= cavitation suppression liquid + ultrasonic wave) and an ultrasonic application liquid (= cavitation promoting liquid + ultrasonic wave) supplied to the peripheral portion of the back surface Wb are supplied. To do. In order to distinguish these, hereinafter, the ultrasonic nozzle 50d is referred to as a “lower ultrasonic nozzle 50d”, and the ultrasonic application liquid supplied from the lower ultrasonic nozzle 50d is referred to as a “lower ultrasonic application liquid DL”. On the other hand, the ultrasonic nozzle 50 s is referred to as “side ultrasonic nozzle 50 s”, and the ultrasonic application liquid supplied from the side ultrasonic nozzle 50 s is referred to as “side ultrasonic application liquid SL”.

  Furthermore, in order to achieve the function of supplying DIW from the upper side of the substrate W to the center of the surface Wf of the substrate W and the function of supplying gas to the surface side of the substrate W, the present embodiment is as follows. It is configured. That is, the fluid ejecting head 70 is provided above the substantially central portion of the substrate surface. Two fluid introducing portions 711 and 721 are erected from the upper part of the fluid ejecting head 70. Among these, the fluid introduction unit 711 has a function of taking in nitrogen gas fed from an external nitrogen gas supply source and DIW fed from a DIW supply source. On the other hand, the fluid introduction part 721 has only a function of taking in nitrogen gas fed from an external nitrogen gas supply source. More specifically, a pipe 713 connected to an external nitrogen gas supply source and inserted through a valve 712 is connected to the fluid introducing portion 711, and connected to the above-described degassing mechanism 42 and inserted through the valve 45. A pipe 714 is connected.

  In addition, two supply paths 715 and 716 extend in the vertical direction inside the fluid introduction portion 711, and the lower end of each supply path 715 and 716 is the lower surface of the fluid ejection head 70 (the surface of the substrate W). And opens toward the substantially center of the substrate W, and functions as a gas discharge port 717 and a DIW discharge port 718, respectively. The upper ends of the supply paths 715 and 716 are connected to pipes 713 and 714, respectively. For this reason, when the valve control mechanism 32 gives an opening command to the valve 712, the valve 712 is opened and nitrogen gas supplied from the nitrogen gas supply source is sent to the fluid ejecting head 70. Further, when the valve control mechanism 32 gives an opening command to the valve 45, the cavitation suppression liquid (that is, DIW from which the dissolved gas has been removed) pumped from the degassing mechanism 42 by opening the valve 45 is supplied to the fluid ejecting head 70. Send it in. On the other hand, when the valves 712 and 45 are closed in response to a closing command from the valve control mechanism 32, the supply of nitrogen gas and DIW is stopped.

  A pipe 723 connected to a nitrogen gas supply source and inserted through a valve 722 is connected to the other fluid introduction part 721 provided in the fluid ejecting head 70. The valve 722 is controlled to be opened and closed by a valve control mechanism 32 controlled by the control unit 30. When the valve 722 is opened as necessary, nitrogen gas supplied from a nitrogen gas supply source passes through the gas supply path 724. Guided to a buffer space BF formed inside the fluid ejecting head 70. Further, a gas ejection port 725 communicating with the buffer space BF is provided on the outer peripheral portion of the side surface of the fluid ejection head 70.

  As described above, the present embodiment has two types of nitrogen gas supply systems. In one of them, that is, a supply system including a nitrogen gas supply source, a valve 712, a pipe 713, and a supply path 715, nitrogen gas pumped from the nitrogen gas supply source passes through the supply path 715 and flows through the fluid ejection head 70. The gas is discharged from the gas discharge port 717 provided on the lower surface toward the center of the surface of the substrate W.

  On the other hand, in the supply system including the nitrogen gas supply source, the valve 722, the pipe 723, and the gas supply path 724, the nitrogen gas pumped from the nitrogen gas supply source is a buffer formed in the fluid ejecting head 70. After being sent into the space BF, it is injected outward through the gas injection port 725. At this time, since the nitrogen gas is pushed out through a slit-like gas injection port 725 extending in a substantially horizontal direction, the range of the spread of the injected nitrogen gas is restricted in the vertical direction, while in the horizontal direction (circumferential direction). Is almost isotropic. That is, by jetting nitrogen gas from the gas injection port 725, a thin-layered airflow is formed on the upper portion of the substrate W from the substantially central portion to the peripheral portion. In particular, in this embodiment, since the pressure-fed gas is once guided to the buffer space BF and then injected from there through the gas injection port 725, a uniform injection amount in the circumferential direction can be obtained. Further, the pressurized nitrogen gas is ejected through a small gap, thereby increasing the flow velocity, and the nitrogen gas is vigorously injected toward the surroundings. As a result, a nitrogen gas flow is ejected from the periphery of the fluid ejecting head 70 to block dust, mist, and the like and the external atmosphere falling from the surface Wf of the substrate W from the surface Wf of the substrate W.

  The fluid ejecting head 70 configured as described above is held above the spin base 12 by an arm (not shown), and the arm is connected to a head lifting mechanism 33 controlled by the control unit 30 and can be lifted and lowered. Has been. With this configuration, the fluid ejecting head 70 is positioned to face the surface Wf of the substrate W held on the spin chuck 10 at a predetermined interval (for example, about 2 to 10 mm). The fluid ejecting head 70, the spin chuck 10, the head lifting mechanism 33, and the chuck rotating mechanism 31 are accommodated in a processing chamber (not shown).

  Note that reference numeral 34 in FIG. 3 denotes a display operation unit configured by a touch panel or the like, which functions as a display unit for displaying image information given from the control unit 30, and keys and buttons displayed on the display unit by the user. It receives the information inputted by operating and the like, and also has a function as an operation input unit that the control unit 30 transmits. Of course, it goes without saying that the display unit and the operation input unit may be provided separately. 3 is a storage unit provided in the control unit 30 and has a function of storing various conditions set in advance when performing the cleaning process, that is, processing conditions, a cleaning program, and the like. .

  Next, the operation of the apparatus configured as described above will be described with reference to FIGS. FIG. 4 is a flowchart showing the operation of the substrate cleaning apparatus shown in FIG. FIG. 5 is a diagram schematically showing the operation of the substrate cleaning apparatus shown in FIG.

  Prior to the start of processing, all the valves 41, 43, 45, 712, and 722 are closed, and the spin chuck 10 is stationary. Then, the control unit 30 controls each part of the apparatus as follows according to a program stored in the storage unit 301 in advance to perform the back surface cleaning process and the drying process of the substrate W. That is, one substrate W is placed on the spin chuck 10 by a substrate transport robot (not shown) and held by the chuck pins 13 (step S1). At this time, if the head lifting mechanism 33 is operated as necessary to move the fluid ejecting head 70 from the spin chuck 10 to the upper separation position, the substrate can be carried in more smoothly. If a sufficient distance is secured between the head 70 and the head 70, the fluid ejecting head 70 does not need to be moved. The same applies to the substrate unloading described later.

  In the next step S2, rotation of the spin chuck 10 is started. Also, the DIW supply to the substrate W is started (step S3). More specifically, the valve 41 is opened, the cavitation suppressing liquid is pumped to the lower ultrasonic nozzle 50d, and discharged from the discharge port 52d toward the center of the back surface of the substrate W. Further, the valve 43 is opened, the cavitation promoting liquid is pumped to the side ultrasonic nozzle 50 s, and discharged from the discharge port 52 s toward the peripheral edge of the back surface of the substrate W. As a result, a DIW liquid film Lb is formed on the back surface Wb of the substrate W as shown in FIG. In this embodiment, since the cavitation suppressing liquid and the cavitation promoting liquid are respectively supplied to the back surface Wb, they are mixed at the merging position (mixing position) P2 between them, and the dissolved gas concentration in the liquid film Lb is in the cavitation suppressing liquid. It's higher than that.

  On the other hand, the liquid film Lf is also formed on the surface Wf of the substrate W. That is, the valve 45 is opened, and the cavitation suppressing liquid is discharged from the DIW discharge port 718 toward the surface Wf of the substrate W. As a result, a liquid film Lf of the cavitation suppression liquid is formed on the surface Wf of the substrate W as shown in FIG. 5 (liquid film forming step).

  When the rotation speed of the spin chuck 10 reaches the set rotation speed set in the program (“YES” in step S4), an oscillation signal is output from the oscillator 60 to the vibrators 53d and 53s (step S5). ). In the side ultrasonic nozzle 50s, an ultrasonic wave is applied to the cavitation promoting liquid by the vibrator 53s that vibrates in response to the oscillation signal, thereby generating a side ultrasonic wave application liquid SL. Then, the side ultrasonic wave application liquid SL is supplied from the side ultrasonic nozzle 50s to the back surface peripheral portion of the substrate W, and further spreads along the back surface Wb to the center of the back surface. The side ultrasonic wave application liquid SL contains a large number of dissolved gases DG, and particles PT are generated from the back surface Wb by cavitation generated in the vicinity of the back surface Wb of the substrate W as shown in the enlarged schematic diagram of the region Rs in FIG. The back surface Wb is removed by cleaning. Cleaning with the side ultrasonic wave application liquid SL proceeds from the back surface peripheral portion side toward the back surface central portion. Since the side ultrasonic nozzle 50s is arranged in the vicinity of the radially outer side of the spin chuck 10, the distance from the discharge port 52s to the landing position of the side ultrasonic wave application liquid SL is short, and the side ultrasonic wave is short. There is little energy attenuation of the ultrasonic wave in the applied liquid SL, and efficient back surface cleaning can be performed.

  On the other hand, in the lower ultrasonic nozzle 50d, an ultrasonic wave is applied to the cavitation suppression liquid by the vibrator 53d that vibrates in response to the oscillation signal, thereby generating a lower ultrasonic application liquid DL. Then, the lower ultrasonic wave application liquid DL is supplied to the center of the back surface of the substrate W through the supply pipe 14. Accordingly, the liquid feeding distance of the lower ultrasonic wave application liquid DL becomes longer than that of the side ultrasonic wave application liquid SL, but the lower ultrasonic wave application liquid DL is low because the dissolved gas concentration in the lower ultrasonic wave application liquid DL is low. The energy attenuation of the ultrasonic wave is small, and even when it reaches the center of the back surface of the substrate W, there is sufficient energy for cleaning the back surface. Further, at the center of the rear surface of the substrate W, as shown in the enlarged schematic diagram of the region Rc in FIG. 5, the lower ultrasonic wave application liquid DL merges with the side ultrasonic wave application liquid SL at the position P2, and the liquid film Lb The dissolved gas concentration increases. As described above, in the present embodiment, since the environment suitable for the substrate cleaning, that is, the sufficient dissolved gas concentration and the sufficient energy of the ultrasonic wave exists also in the central portion on the back surface of the substrate W, the central portion on the back surface of the substrate W. The particles PT can be removed from the back surface Wb by the cavitation generated in the above, and efficient back surface cleaning can be performed. As a result, the entire back surface Wb of the substrate W can be cleaned well (cleaning process).

  The cleaning process using the lower ultrasonic wave application liquid DL and the side ultrasonic wave application liquid SL described above is continuously performed for the set time set in the program, and the passage of the set time is confirmed in step S6. Then, the oscillator 60 stops outputting the oscillation signal (step S7), and then the valves 41, 43, 45 are closed to stop the supply of the cavitation promoting liquid (DIW) and the cavitation suppressing liquid (DIW) ( Step S8).

  When the cleaning process is completed in this way, a drying process for removing DIW remaining on the front surface Wf and the back surface Wb of the substrate W is performed. That is, while the substrate W is rotated, the valve 722 is opened, and the injection of nitrogen gas is started from the gas injection port 725 provided around the fluid ejection head 70 (step S9). Subsequently, the valve 712 is opened, and supply of nitrogen gas from the gas discharge port 717 provided on the lower surface of the fluid ejecting head 70 toward the surface Wf of the substrate W is started (step S10).

  The flow rate of the nitrogen gas supplied from the gas injection port 725 is high, and the vertical injection direction is narrowed, and a curtain of nitrogen gas that flows radially from the center to the periphery is formed at the upper part of the substrate W. Yes. On the other hand, the flow rate of the nitrogen gas supplied from the gas discharge port 717 is slower than this, and the flow rate is limited so as not to flow strongly toward the surface Wf of the substrate W. For this reason, the nitrogen gas supplied from the gas discharge port 717 purges the air remaining in the space surrounded by the curtain-like gas layer injected from the gas injection port 725 and the surface Wf of the substrate W, thereby Acts to keep the atmosphere. Therefore, here, the nitrogen gas supplied from the gas injection port 725 is referred to as “curtain gas”, and the nitrogen gas discharged from the gas discharge port 717 is referred to as “purging gas”.

  In this way, a gas curtain is formed above the substrate W and the surface Wf of the substrate W is maintained in a nitrogen atmosphere, and the rotation speed of the spin chuck 10 is increased to rotate the substrate W at a high speed (step S11). The substrate W is dried by shaking off the pure water on the front surface Wf and the back surface Wb. By continuing to supply the curtain gas and the purge gas during the drying process, adhesion of mist and the like to the surface Wf of the dried substrate W and oxidation are prevented. When the drying process is completed, the rotation of the spin chuck 10 is stopped (step S12), and the supply of the purge gas and the curtain gas is sequentially stopped (steps S13 and S14). Then, the substrate transfer robot removes the dried substrate W from the spin chuck 10 and carries it out to another apparatus (step S15), whereby the back surface cleaning process for one substrate W is completed. Further, by repeating the above processing, a plurality of substrates can be processed sequentially.

  As described above, in this embodiment, the ultrasonic wave is applied to the cavitation suppression liquid (deaeration liquid) at the ultrasonic wave application position P1 to generate the lower ultrasonic wave application liquid DL, and the substrate side from the ultrasonic wave application position P1. The dissolved gas concentration is increased by mixing with the side ultrasonic wave application liquid SL on the back surface Wb at the substrate proximity position P2. For this reason, it is possible to suppress the occurrence of cavitation in the lower ultrasonic wave application liquid DL between the ultrasonic wave application position P1 and the substrate proximity position P2, thereby the energy of ultrasonic waves in the lower ultrasonic wave application liquid DL. Attenuation is suppressed. Then, at the substrate proximity position P2, the lower ultrasonic wave application liquid DL generates a large number of cavitations on or near the back surface Wb due to the increase of the dissolved gas concentration as described above while having the ultrasonic waves that have avoided energy attenuation. As a result, the back surface Wb of the substrate W can be satisfactorily cleaned even though the lower ultrasonic wave application liquid DL is generated at the ultrasonic wave application position P1 away from the back surface Wb of the substrate W.

  In addition, cavitation is generated mainly by the ultrasonic wave applied to the lower ultrasonic wave application liquid DL in the center of the back surface of the substrate W, and cavitation is generated mainly by the ultrasonic wave applied to the side ultrasonic wave application liquid SL in the peripheral part of the back surface. Then, the substrate is cleaned. Therefore, the particles PT can be effectively removed from the entire back surface of the substrate W, and the back surface Wb of the substrate W can be cleaned well. In addition, the removal efficiency has high in-plane uniformity.

Further, since the ultrasonic wave application liquids DL and SL to which ultrasonic waves are applied are applied to the back surface Wb, the sound waves are also transmitted to the front surface Wf side, which may damage the pattern. However, in the present embodiment, the liquid film Lf is formed on the surface Wf of the substrate W using a cavitation suppressing liquid (a degassing liquid) having a low cavitation strength. That is, before supply to the surface Wf, DIW is degassed to lower the dissolved gas concentration from that of the cavitation promoting liquid, whereby the liquid supplied to the surface Wf of the substrate W, that is, the cavitation suppressing liquid The cavitation strength is reduced. Here, “cavitation strength” means the stress per unit area acting on the substrate W due to cavitation generated in the liquid by ultrasonic waves, and this cavitation strength is determined by the cavitation coefficient α and the bubble collapse energy U. Determined. That is, the following equation is cavitation α α = (Pe-Pv) / (ρV 2/2) ... ( Equation 1)
Where Pe: static pressure, Pv: vapor pressure, ρ: density, V: flow velocity,
The cavitation strength increases as the cavitation coefficient α decreases. The bubble collapse energy U is expressed by the following equation: U = 4πr ² σ = 16πσ ³ / (Pe−Pv) ² (Formula 2)
Where r: bubble radius before collapse, σ: surface tension,
The cavitation intensity increases as the bubble collapse energy U increases.

  In the present embodiment, the gas pressure dissolved in the cavitation suppressing liquid is kept low by the degassing process by the degassing mechanism 42, and therefore the vapor pressure Pv is greatly reduced. Therefore, while the cavitation coefficient α increases, the bubble collapse energy U decreases, and the cavitation strength of the cavitation suppression liquid decreases. As a result, although the sound wave is transmitted to the front surface Wf side during the back surface cleaning process, the cavitation strength can be suppressed low, and the pattern damage on the substrate front surface side can be effectively suppressed.

  FIG. 6 is a view showing a second embodiment of the substrate cleaning apparatus according to the present invention. The second embodiment is greatly different from the first embodiment in the configuration and position for increasing the dissolved gas concentration of the lower ultrasonic wave application liquid DL, and other configurations are basically different from those in the first embodiment. Are the same. Accordingly, the following description will focus on the differences, and the same components will be denoted by the same reference numerals, and the description of the components will be omitted.

  In the second embodiment, as shown in FIG. 6, in the hollow portion 11 a of the rotation support shaft 11, another supply pipe 15 branches from the supply pipe 14 and extends to the side opposite to the substrate (the lower side in the figure). Has been. The supply pipe 15 is connected to a gas concentration adjusting mechanism 44 through a valve 46. Then, when the valve control mechanism 32 gives an opening command to the valve 46, the valve 46 opens and the cavitation promoting liquid pumped from the gas concentration adjusting mechanism 44 is sent through the supply pipe 15 to join the supply pipe 14. Mixed at position P3. In the second embodiment, as shown in FIG. 6, the merging position P3 is set to a substrate proximity position closest to the substrate W in the hollow portion 11a. For this reason, it is possible to suppress the occurrence of cavitation in the lower ultrasonic wave application liquid DL between the ultrasonic wave application position P1 and the merging position (substrate proximity position) P3. Ultrasonic energy attenuation is suppressed. Then, at the joining position P3, the lower ultrasonic wave application liquid DL increases the dissolved gas concentration of the lower ultrasonic wave application liquid DL as described above while having the ultrasonic waves that have avoided energy attenuation, and the side ultrasonic wave application liquid SL. In this state (that is, a state in which ultrasonic waves are applied to the cavitation promoting liquid), the state is supplied to the center of the back surface of the substrate W. Moreover, since the joining position P3 is set at a position close to the substrate W, the distance from the joining position P3 to the center of the back surface of the substrate W is larger than the distance from the ultrasonic wave application position P1 to the center of the back surface of the substrate W. It is much shorter and the ultrasonic energy attenuation is small. As a result, many cavitations occur on or near the back surface Wb, and the back surface of the substrate W is generated despite the generation of the lower ultrasonic wave application liquid DL at the ultrasonic wave application position P1 away from the back surface Wb of the substrate W. Wb can be washed well.

  In the second embodiment, not only the lower ultrasonic wave application liquid DL but also the side ultrasonic wave application liquid SL is supplied to the peripheral edge of the back surface of the substrate W, as in the first embodiment. The particles PT can be efficiently removed from the entire back surface. Further, as in the first embodiment, the liquid film Lf of the cavitation suppression liquid (deaeration liquid) is formed on the surface Wf of the substrate W during the back surface cleaning, so that the pattern damage on the substrate surface side is effective. Can be suppressed.

  The present invention is not limited to the above-described embodiment, and various modifications other than those described above can be made without departing from the spirit of the present invention. For example, in the second embodiment, the supply pipe 15 is branched from the supply pipe 14, but a composite pipe 16 may be used instead of the supply pipes 14 and 15 as shown in FIG. 7 (third embodiment). ). That is, the pipe main body 16 a of the composite pipe 16 has a shape that can be inserted through the hollow portion 11 a of the rotary support shaft 11. A pipe line 16b corresponding to the supply pipe 14 and a pipe line 16c corresponding to the supply pipe 15 are provided inside the pipe body 16a. The pipe line 16b guides the lower ultrasonic wave application liquid DL discharged from the lower ultrasonic nozzle 50d toward the center of the back surface of the substrate W, while the pipe line 16c receives the cavitation promoting liquid pumped from the gas concentration adjusting mechanism 44. Guide and merge with the lower ultrasonic wave application liquid DL at the merge position P4 with the pipe line 16c to increase the dissolved gas concentration. In the third embodiment as well, as in the second embodiment, the merge position P4 is set to the board proximity position closest to the board W in the pipe body 16a.

  In the first to third embodiments, the side ultrasonic wave application liquid SL is supplied to the peripheral edge of the back surface of the substrate W. However, the side ultrasonic wave application liquid SL (= cavitation promoting liquid + ultrasonic wave is used. For example, as shown in FIG. 8, the cavitation promoting liquid AL may be supplied from the nozzle 80 (fourth embodiment). In the fourth embodiment, at the peripheral edge of the back surface of the substrate W, the ultrasonic wave sent to the liquid film Lb on the back surface Wb via the lower ultrasonic wave application liquid DL is propagated along the back surface Wb to generate cavitation. To do. Thus, the entire back surface of the substrate W is cleaned.

  In the second and third embodiments, the lower ultrasonic wave application liquid DL (= cavitation promoting liquid + ultrasound) is supplied to the back surface Wb of the substrate W. For this reason, it is possible to form the liquid film Lb composed of the cavitation promoting liquid on the entire back surface of the substrate W only by supplying the lower ultrasonic wave application liquid DL. Therefore, for example, as shown in FIG. 9, the supply of the lateral ultrasonic wave application liquid SL to the peripheral edge of the back surface of the substrate W may be omitted (fifth embodiment). In the fifth embodiment, at the peripheral edge of the back surface of the substrate W, the lower ultrasonic wave application liquid DL spreads along the back surface Wb to the peripheral edge of the back surface, and cavitation occurs in the entire back surface. Thus, the entire back surface of the substrate W is cleaned.

  In the second embodiment, the cavitation promoting liquid is joined to the lower ultrasonic wave application liquid DL at the joining position P3 to increase the dissolved gas concentration. However, instead of the cavitation promoting liquid, a gas such as nitrogen gas is used in the downward direction. The ultrasonic application liquid DL may be mixed (sixth embodiment). For example, as shown in FIG. 10, the diffuser pipe 17 is arranged at the merging position P3, and the nitrogen gas NG fed from the nitrogen gas supply source through the valve 47 and the supply pipe 15 is sent to the diffuser pipe 17 to reduce the dissolved gas concentration. It may be raised.

  In the first embodiment, the discharge of the cavitation suppressing liquid from the lower ultrasonic nozzle 50d and the discharge of the cavitation promoting liquid from the side ultrasonic nozzle 50s are simultaneously performed (step S3), and the vibrator 53d, The oscillation signal is simultaneously applied to 53s (step S5). Of course, these timings are arbitrary, and the discharge of the cavitation promoting liquid may be started earlier than the discharge of the cavitation suppressing liquid.

  Further, in the above embodiment, the DIW is degassed to generate a cavitation suppressing liquid, and a gas such as nitrogen gas is dissolved in DIW to generate a cavitation promoting liquid. The type of the substrate is not limited to DIW, but a substrate such as a liquid mainly composed of isopropyl alcohol (IPA), ethanol, hydrofluoroether (HFE), SC1 (mixed aqueous solution of ammonia water and hydrogen peroxide solution), etc. The same applies to general cleaning liquids used for cleaning. In addition, liquids having different compositions may be used as the cavitation suppressing liquid and the cavitation promoting liquid. Further, instead of using a liquid in which a gas such as nitrogen gas is dissolved in DIW as a cavitation promoting liquid, any liquid that dissolves a gas suitable for cleaning may be used as it is as a cavitation promoting liquid.

  Thus, in the above embodiment, the back surface Wb and the front surface Wf of the substrate W correspond to the “one main surface” and the “other main surface” of the present invention, respectively. Further, the spin chuck 10 corresponds to an example of the “substrate holding part” of the present invention. Further, in the above embodiment, an oscillation signal is given to the vibrator 53d and an ultrasonic wave is applied to the cavitation suppressing liquid in the lower ultrasonic nozzle 50d to generate the lower ultrasonic application liquid DL, and the substrate is formed from the lower ultrasonic nozzle 50d. The process of supplying toward the center of the back surface of W corresponds to an example of the “ultrasonic application liquid supply process” of the present invention, and the lower ultrasonic nozzle 50d corresponds to an example of the “ultrasonic application liquid supply part” of the present invention. doing. The positions P2 to P4 correspond to an example of “a position closer to one main surface than the ultrasonic wave application position” of the present invention. Further, the lateral ultrasonic wave application liquid SL in the first embodiment and the cavitation promoting liquid AL in the fourth embodiment correspond to an example of the “first gas dissolved liquid” of the present invention, and these are provided on the peripheral edge of the back surface of the substrate W. The supplying process corresponds to an example of the “gas dissolved liquid supplying process” of the present invention. Further, the cavitation promoting liquid flowing through the supply pipe 15 in the second embodiment and the cavitation promoting liquid flowing through the pipe line 16c in the third embodiment correspond to an example of the “second gas dissolved liquid” of the present invention. Yes. Moreover, the process of forming the liquid film Lf on the front surface Wf of the substrate W during the cleaning process is an example of the “liquid film forming process” of the present invention, and the liquid film Lf is constituted by cleaning the back surface Wb with the ultrasonic application liquid. The cavitation suppressing liquid (degassing liquid) to be performed corresponds to an example of the “protective liquid” of the present invention. Further, the side ultrasonic nozzle 50s in the first embodiment shown in FIG. 5, the supply pipe 15 in the second embodiment shown in FIG. 6 and the fifth embodiment shown in FIG. 9, and the composite in the third embodiment shown in FIG. The pipe 16c of the pipe 16, the nozzle 80 in the fourth embodiment shown in FIG. 8, and the supply pipe 15 and the diffuser pipe 17 in the sixth embodiment shown in FIG. 10 correspond to an example of the “concentration adjusting unit” of the present invention. doing.

  As described above, the present invention has been described by exemplifying specific embodiments. For example, the present invention provides a gas-dissolved liquid supply step of supplying a first gas-dissolved liquid having a dissolved gas concentration higher than that of a degassed liquid to one main surface. In the cleaning step, the first gas dissolved liquid supplied to the one main surface and the ultrasonic application liquid before being supplied to the one main surface are mixed to increase the dissolved gas concentration of the ultrasonic application liquid. You may comprise as follows. Accordingly, the dissolved gas concentration of the ultrasonic application liquid is increased immediately before the ultrasonic application liquid is supplied to the one main surface, and the energy attenuation of the ultrasonic wave in the ultrasonic application liquid can be minimized.

  Further, the position to supply the ultrasonic application liquid is arbitrary, but in the gas dissolved liquid supplying step, the first gas dissolved liquid is supplied from the outer side in the radial direction of the substrate to the peripheral edge of the one main surface, and the entire one main surface is supplied. In the cleaning process, mixing may be performed in the vicinity of the central portion of the one main surface. Further, in the gas dissolved liquid supply step, ultrasonic waves may be applied to the first gas dissolved liquid and supplied to the one main surface, whereby the entire one main surface can be cleaned uniformly.

  In the cleaning step, the second gas dissolved liquid having a higher dissolved gas concentration than the degassed liquid is mixed with the ultrasonic applied liquid between the mixing position where the mixing is performed and the ultrasonic applied position, and the ultrasonic applied liquid is mixed. You may comprise so that a dissolved gas concentration may be raised. Moreover, you may mix gas instead of a 2nd gas solution. That is, in the cleaning process, the gas is mixed with the ultrasonic application liquid by supplying the gas to the air diffusion pipe provided between the mixing position where the mixing is performed and the ultrasonic application position, and the ultrasonic application liquid is dissolved. You may comprise so that gas concentration may be raised.

  Also, in the cleaning process, the dissolved gas concentration of the dissolved gas concentration than the degassed liquid is mixed with the ultrasonic wave application liquid at a position closer to one main surface than the ultrasonic wave application position, so that the dissolved gas concentration of the ultrasonic wave application liquid is increased. You may comprise so that it may raise. In the cleaning process, gas is supplied to the diffuser tube at a position closer to the one main surface than the ultrasonic application position to mix the gas with the ultrasonic application liquid before supply to the one main surface. You may comprise so that the dissolved gas concentration of an ultrasonic application liquid may be raised.

  Further, the liquid film forming step of forming a liquid film of the protective liquid on the other main surface of the substrate while the one main surface is cleaned with the ultrasonic application liquid is further provided. When ultrasonic waves are transmitted to the liquid existing in the liquid, the cavitation strength, which is the stress per unit area acting on the substrate, is protected by the cavitation generated in the liquid, which is lower than the ultrasonic application liquid supplied to the main surface. You may comprise so that it may be used as a liquid. Thus, by forming the liquid film of the protective liquid on the other main surface of the substrate, it is possible to effectively suppress the influence of sound waves transmitted to the other main surface during the cleaning process.

  The present invention is suitable for a substrate cleaning technique for cleaning one main surface of a substrate with an ultrasonic wave application liquid to which ultrasonic waves are applied.

DESCRIPTION OF SYMBOLS 1 ... Substrate cleaning apparatus 10 ... Spin chuck (substrate holding part)
15 ... Supply pipe (concentration adjustment unit)
16 ... Composite piping (concentration adjuster)
16c ... Pipe line (concentration adjustment unit)
17 ... Diffuser (concentration adjustment unit)
50d: lower ultrasonic nozzle (ultrasonic application liquid supply unit)
80 ... Nozzle (density adjustment unit)
AL ... Cavitation promotion liquid (first gas dissolved liquid)
DL ... Lower ultrasonic wave application liquid DG ... Dissolved gas NG ... Nitrogen gas (gas)
P1 ... Ultrasonic application position P2, P3, P4 ... Merge position SL ... Side ultrasonic application liquid (first gas dissolved liquid)
W ... Substrate Wb ... Back side (one main surface of the substrate)
Wf ... surface (the other main surface of the substrate)

Claims (10)

A substrate cleaning method for cleaning the one main surface of the substrate held by a substrate holder provided opposite to the one main surface of the substrate,
An ultrasonic application liquid is generated by applying an ultrasonic wave to a degassed liquid that is a degassed liquid at an ultrasonic wave application position on the opposite side of the substrate with respect to the substrate holding unit, and directed toward the one main surface. An ultrasonic application liquid supply step to supply;
A cleaning step of cleaning the one main surface with the ultrasonic application liquid after increasing the dissolved gas concentration of the ultrasonic application liquid at a position closer to the one main surface than the ultrasonic application position. A substrate cleaning method. The substrate cleaning method according to claim 1,
A gas dissolved liquid supply step of supplying a first gas dissolved liquid having a higher dissolved gas concentration than the degassed liquid to the one main surface;
In the cleaning step, the first gas dissolved liquid supplied to the one main surface and the ultrasonic application liquid before being supplied to the one main surface are mixed to increase the dissolved gas concentration of the ultrasonic application liquid. Substrate cleaning method. The substrate cleaning method according to claim 2,
In the gas-dissolved liquid supplying step, the first gas-dissolved liquid is supplied from the outside in the radial direction of the substrate to the peripheral portion of the one main surface and spread over the entire one main surface,
The substrate cleaning method, wherein, in the cleaning step, the mixing is performed at a position near a central portion of the one main surface. The substrate cleaning method according to claim 3,
In the gas dissolved liquid supply step, a substrate cleaning method in which an ultrasonic wave is applied to the first gas dissolved liquid and supplied to the one main surface. A substrate cleaning method according to any one of claims 2 to 4,
In the cleaning step, between the mixing position where the mixing is performed and the ultrasonic wave application position, a second gas dissolved liquid having a dissolved gas concentration higher than that of the degassed liquid is mixed with the ultrasonic wave applied liquid, and the ultrasonic wave is mixed. A substrate cleaning method for increasing the dissolved gas concentration of a sound wave application liquid. A substrate cleaning method according to any one of claims 2 to 4,
In the cleaning step, gas is supplied to an air diffuser provided between the mixing position where the mixing is performed and the ultrasonic wave application position, whereby the gas is mixed with the ultrasonic wave application liquid by the air diffuser, and the ultrasonic wave is mixed. A substrate cleaning method for increasing the dissolved gas concentration of a sound wave application liquid. The substrate cleaning method according to claim 1,
In the cleaning step, a gas dissolved liquid having a dissolved gas concentration higher than that of the degassed liquid is mixed with the ultrasonic applied liquid at a position closer to the one main surface than the ultrasonic applied position, and the ultrasonic applied liquid. Substrate cleaning method for increasing the dissolved gas concentration. The substrate cleaning method according to claim 1,
In the cleaning step, the gas is supplied to the air diffuser provided at a position closer to the one main surface than the ultrasonic application position, whereby the gas is supplied to the one main surface before the gas is supplied to the one main surface. A substrate cleaning method in which the dissolved gas concentration of the ultrasonic application liquid is increased by mixing with the ultrasonic application liquid. A substrate cleaning method according to any one of claims 1 to 8,
A liquid film forming step of forming a liquid film of a protective liquid on the other main surface of the substrate while cleaning the one main surface with the ultrasonic wave application liquid;
In the liquid film forming step, the cavitation strength, which is a stress per unit area acting on the substrate due to cavitation generated in the liquid when an ultrasonic wave is transmitted to the liquid existing on the main surface of the substrate, is the one main surface. A substrate cleaning method in which a liquid lower than the ultrasonic application liquid supplied to a surface is used as the protective liquid. A substrate holding part that is provided opposite to one main surface of the substrate and holds the substrate;
An ultrasonic application liquid is generated by applying an ultrasonic wave to a degassed liquid that is a degassed liquid at an ultrasonic wave application position on the opposite side of the substrate with respect to the substrate holding unit, and directed toward the one main surface. An ultrasonic application liquid supply section for supplying;
A concentration adjusting unit that adjusts so that the dissolved gas concentration of the ultrasonic wave application liquid increases at a position closer to the one main surface than the ultrasonic wave application position;
The substrate cleaning apparatus, wherein the one main surface is cleaned with the ultrasonic wave application liquid whose dissolved gas concentration is adjusted by the concentration adjusting unit.

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