Substrate processing apparatus and substrate processing method

Abstract

To provide a technique to suppress fluctuations in phosphoric acid concentration of a phosphoric acid aqueous solution.SOLUTION: A substrate processing apparatus includes a substrate processing unit for immersing a substrate in a phosphoric acid aqueous solution, and a control unit for controlling the substrate processing unit. The substrate processing unit includes: a processing tub including an inner tub for storing the phosphoric acid aqueous solution and an outer tub for collecting the phosphoric acid aqueous solution that overflows from the inner tub; a circulation line for sending the phosphoric acid aqueous solution taken out from the outer tub into the inner tub; a liquid level sensor for detecting a liquid level of the phosphoric acid aqueous solution in the outer tub; and a pure water supply section for supplying pure water into the processing tub. The substrate is immersed in the phosphoric acid aqueous solution in the inner tub. The control unit controls a supply flow rate of the pure water based on a detection value of the liquid level.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a substrate processing apparatus and a substrate processing method.

Background Art

[0002] Patent Document 1 describes a method for controlling the boiling state of an aqueous phosphoric acid solution. The method quantitatively evaluates the boiling state of the aqueous phosphoric acid solution based on the back pressure when an inert gas is purged inside the aqueous phosphoric acid solution.

[0003] Patent Document 2 describes correcting the phosphoric acid concentration of an aqueous phosphoric acid solution according to the atmospheric pressure. The higher the atmospheric pressure, the lower the phosphoric acid concentration is set.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] One aspect of the present disclosure provides a technique for suppressing fluctuations in the phosphoric acid concentration of an aqueous phosphoric acid solution.

Means for Solving the Problems

[0006] A substrate processing apparatus according to an aspect of the present disclosure includes a substrate processing unit that immerses a substrate in an aqueous phosphoric acid solution, and a control unit that controls the substrate processing unit. The substrate processing unit includes a processing tank having an inner tank for storing the aqueous phosphoric acid solution and an outer tank for collecting the aqueous phosphoric acid solution that overflows from the inner tank, a circulation line for sending the aqueous phosphoric acid solution taken out from the outer tank to the inner tank, a liquid level sensor for detecting the liquid level height of the aqueous phosphoric acid solution in the outer tank, and a pure water supply unit for supplying pure water to the processing tank, and immerses the substrate in the aqueous phosphoric acid solution inside the inner tank. The control unit controls the supply flow rate of the pure water based on the detected value of the liquid level height.

Advantages of the Invention

[0007] According to one aspect of the present disclosure, fluctuations in the phosphoric acid concentration of the aqueous phosphoric acid solution can be suppressed.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

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Figure 9

Embodiments for Carrying Out the Invention

[0009] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In each drawing, the same or corresponding components are denoted by the same reference numerals, and the description may be omitted. In this specification, the X-axis direction, the Y-axis direction, and the Z-axis direction are perpendicular to each other. The X-axis direction and the Y-axis direction are horizontal directions, and the Z-axis direction is a vertical direction. The X-axis direction includes the positive X-axis direction and the negative X-axis direction, which is opposite to the positive X-axis direction. The Y-axis direction includes the positive Y-axis direction and the negative Y-axis direction, which is opposite to the positive Y-axis direction. The Z-axis direction includes the positive Z-axis direction and the negative Z-axis direction, which is opposite to the positive Z-axis direction. Also, in this specification, the supply flow rate means the supply amount per unit time.

[0010] As shown in FIG. 1, the substrate processing apparatus 1 includes a substrate processing unit 10 that immerses a substrate W in a phosphoric acid aqueous solution L, and a control unit 90 that controls the substrate processing unit 10. The substrate W includes a silicon oxide film and a silicon nitride film, and the phosphoric acid aqueous solution L selectively etches the silicon nitride film among the silicon oxide film and the silicon nitride film. The phosphoric acid aqueous solution L contains phosphoric acid and water.

[0011] The substrate processing unit 10 includes a processing tank 20. The processing tank 20 has an inner tank 21 that stores the phosphoric acid aqueous solution L and an outer tank 22 that recovers the phosphoric acid aqueous solution L that has overflowed from the inner tank 21. The substrate processing unit 10 immerses the substrate W in the phosphoric acid aqueous solution L inside the inner tank 21. The liquid level height of the phosphoric acid aqueous solution L in the inner tank 21 is the same as the height of the upper end of the inner tank 21.

[0012] The substrate processing unit 10 includes a circulation line 30. The circulation line 30 sends the phosphoric acid aqueous solution L taken out from the outer tank 22 to the inner tank 21. The phosphoric acid aqueous solution L that has overflowed from the inner tank 21 is recovered in the outer tank 22. The liquid level height of the phosphoric acid aqueous solution L in the outer tank 22 changes when the substrate W is immersed in the phosphoric acid aqueous solution L and when it is not immersed.

[0013] The substrate processing unit 10 includes a pump 31, a temperature controller 32, and a filter 33 in the middle of the circulation line 30. The pump 31 pumps the phosphoric acid aqueous solution L. The temperature controller 32 adjusts the temperature of the phosphoric acid aqueous solution L. The temperature controller 32 includes a heater. The temperature of the phosphoric acid aqueous solution L is set to, for example, the boiling point of the phosphoric acid aqueous solution L. The filter 33 collects the particles contained in the phosphoric acid aqueous solution L.

[0014] The substrate processing unit 10 includes a horizontal tube 34 at the tip of the circulation line 30. The horizontal tube 34 extends in the X-axis direction, and a plurality of horizontal tubes 34 are provided at intervals in the Y-axis direction. The plurality of horizontal tubes 34 have a plurality of discharge ports at intervals in their longitudinal directions. The plurality of discharge ports discharge the phosphoric acid aqueous solution L upward, respectively, and form a curtain-like upward flow inside the inner tank 21.

[0015] The substrate processing unit 10 includes a substrate holding unit 40 and a lifting unit 45. The substrate holding unit 40 holds the substrate W. For example, the substrate holding unit 40 holds a plurality of substrates W at intervals in the X-axis direction and holds each substrate W vertically. The lifting unit 45 raises and lowers the substrate holding unit 40 between an immersion position where the substrate W is immersed in the phosphoric acid aqueous solution L and a standby position where the substrate W is lifted from the phosphoric acid aqueous solution L.

[0016] The substrate processing unit 10 includes a pure water supply unit 50 and a phosphoric acid supply unit 55. The pure water supply unit 50 supplies pure water to the processing tank 20 (preferably the outer tank 22). The phosphoric acid supply unit 55 supplies phosphoric acid to the processing tank 20 (preferably the outer tank 22). The pure water supply unit 50 and the phosphoric acid supply unit 55 each have, for example, an on-off valve and a flow controller.

[0017] The substrate processing unit 10 includes a discharge unit 59. The discharge unit 59 discharges the phosphoric acid aqueous solution L to the outside of the substrate processing apparatus 1. In this embodiment, the discharge unit 59 discharges the phosphoric acid aqueous solution L from the bottom of the inner tank 21, but the phosphoric acid aqueous solution L may be discharged from the circulation line 30. The discharge unit 59 has, for example, an on-off valve and a flow controller.

[0018] The discharge section 59 periodically discharges at least a part of the phosphoric acid aqueous solution L. Thereafter, the phosphoric acid supply section 55 supplies phosphoric acid to the processing tank 20 and the pure water supply section 50 supplies pure water to the processing tank 20, thereby preparing the phosphoric acid aqueous solution L. The supply amounts of the phosphoric acid and the pure water are preset.

[0019] The control section 90 is, for example, a computer and includes an arithmetic section 91 such as a CPU (Central Processing Unit) and a storage section 92 such as a memory. The storage section 92 stores programs for controlling various processes executed in the substrate processing apparatus 1. The control section 90 controls the operation of the substrate processing apparatus 1 by causing the arithmetic section 91 to execute the programs stored in the storage section 92.

[0020] The phosphoric acid aqueous solution L contains phosphoric acid and water. Water has a lower boiling point than phosphoric acid. During the boiling of the phosphoric acid aqueous solution L, water selectively evaporates. Therefore, the substrate processing apparatus 1 may include an inspection line 60 and a concentration sensor 65. The inspection line 60 branches from the circulation line 30 downstream of the temperature controller 32 and sends the phosphoric acid aqueous solution L flowing through the circulation line 30 to the outer tank 22. The inspection line 60 can suppress the retention of the phosphoric acid aqueous solution L and can suppress the temperature drop of the phosphoric acid aqueous solution L. The concentration sensor 65 detects the phosphoric acid concentration C of the phosphoric acid aqueous solution L flowing through the inspection line 60. The concentration sensor 65 detects the phosphoric acid concentration C of the phosphoric acid aqueous solution L by detecting, for example, the refractive index of the phosphoric acid aqueous solution L.

[0021] After preparing the phosphoric acid aqueous solution L, the control section 90 performs the following concentration control (see FIG. 2). The concentration control is feedback control, and controls the supply flow rate Q of pure water so that the detected value C_det of the phosphoric acid concentration C becomes the set value C_ref. Q is the supply flow rate of water that the pure water supply section 50 supplies to the processing tank 20. The concentration control is performed in a state where the substrate W is not immersed in the phosphoric acid aqueous solution L in the inner tank 21 and the phosphoric acid supply section 55 has stopped supplying phosphoric acid. Further, the concentration control is performed in a state where the temperature of the phosphoric acid aqueous solution L is stabilized.

[0022] Note that the control unit 90 may correct the set value C_ref of the phosphoric acid concentration C according to the atmospheric pressure. When the phosphoric acid concentration C is the same, the higher the atmospheric pressure, the higher the boiling point of the phosphoric acid aqueous solution L. On the other hand, when the atmospheric pressure is the same, the lower the phosphoric acid concentration C, the lower the boiling point of the phosphoric acid aqueous solution L. The higher the atmospheric pressure, the lower the control unit 90 controls the phosphoric acid concentration C, so that the temperature of the phosphoric acid aqueous solution L can be kept constant and the boiling state (e.g., the size and number of bubbles) of the phosphoric acid aqueous solution L can be kept constant. Note that the reason for keeping the temperature of the phosphoric acid aqueous solution L constant is that the volume of the phosphoric acid aqueous solution L is large, its heat capacity is large, and it takes time to change the temperature.

[0023] The control unit 90 calculates the average value Qave of the supply flow rate Q of pure water in at least a part of the period P1 of the period P during which the concentration control is performed. The average value Qave corresponds to the evaporation amount V of water per unit time in the phosphoric acid aqueous solution L. It is preferable that the control unit 90 calculates the average value Qave in a part of the period P1 of the period P during which the concentration control is performed. The part of the period P1 is preferably the period immediately before the end of the period P during which the concentration control is performed (e.g., 5 minutes). Note that the time is not limited to 5 minutes.

[0024] After the concentration control, the control unit 90 performs the following flow rate control (see FIG. 2). The flow rate control controls the supply flow rate Q of pure water based on the average value Qave of the supply flow rate Q of pure water calculated in advance. For example, the control unit 90 fixes the supply flow rate Q of pure water to the average value Qave. Thereby, the fluctuation of the phosphoric acid concentration C can be suppressed without referring to the detected value C_det of the phosphoric acid concentration C. Therefore, although it will be described in detail later, the fluctuation of the phosphoric acid concentration C in the plurality of substrate processing units 10 can be suppressed by using one concentration sensor 65.

[0025] During flow control, the control unit 90 can not only fix the supply flow rate Q of pure water to the average value Qave, but also correct it based on the average value Qave. For example, during flow control, the control unit 90 may correct the supply flow rate Q of pure water according to the change amount ΔH2 of the liquid level height H2 of the phosphoric acid aqueous solution L in the outer tank 22. Although it will be described in detail later, this is because the evaporation amount V of water per unit time in the phosphoric acid aqueous solution L depends on the liquid level height H2.

[0026] The evaporation amount V of water per unit time in the phosphoric acid aqueous solution L depends on the area of the interface between the phosphoric acid aqueous solution L and the atmosphere. The larger the area of the interface between the phosphoric acid aqueous solution L and the atmosphere, the larger the evaporation amount V. The interface between the phosphoric acid aqueous solution L and the atmosphere includes the liquid level of the phosphoric acid aqueous solution L in the inner tank 21 and the liquid level of the phosphoric acid aqueous solution L in the outer tank 22. The areas of these liquid levels are constant.

[0027] The interface between the phosphoric acid aqueous solution L and the atmosphere also includes the side surface of the phosphoric acid aqueous solution L flowing down along the side surface of the inner tank 21 from the upper end of the inner tank 21. The area of that side surface is proportional to the drop of the phosphoric acid aqueous solution L flowing down. That drop is equal to the height difference ΔH (ΔH = H1 - H2) between the liquid level height H1 of the phosphoric acid aqueous solution L in the inner tank 21 and the liquid level height H2 of the phosphoric acid aqueous solution L in the outer tank 22. Since H1 is constant, ΔH depends on H2. Note that the reference points of H1 and H2 may be points at the same height and are not particularly limited.

[0028] The larger the liquid level height H2 of the phosphoric acid aqueous solution L in the outer tank 22, the smaller the height difference ΔH, and the smaller the area of the interface between the phosphoric acid aqueous solution L and the atmosphere. Therefore, the larger the liquid level height H2, the smaller the evaporation amount V. The inventor of the present application focused on the fact that the larger the liquid level height H2, the smaller the evaporation amount V. Note that the liquid level height H2 can change due to the immersion or lifting of the substrate W, or the taking out of the phosphoric acid aqueous solution L adhering to the substrate W.

[0029] The substrate processing unit 10 is provided with a liquid level sensor 25. The liquid level sensor 25 detects the liquid level height H2 of the phosphoric acid aqueous solution L in the outer tank 22. The control unit 90 controls the supply flow rate Q of pure water based on the detected value H2_det of the liquid level height H2. Thereby, even if the liquid level height H2 fluctuates and the evaporation amount V fluctuates, pure water can be replenished at a flow rate corresponding to the evaporation amount V. Therefore, fluctuations in the phosphoric acid concentration C can be suppressed without using the concentration sensor 65.

[0030] The control unit 90 stores in advance the relationship between the liquid level height H2 and the evaporation amount V (for example, the relationship shown in FIG. 3). V is represented by a linear equation of H2. This is because V is proportional to the area of the interface between the phosphoric acid aqueous solution L and the atmosphere, and the area is represented by a linear equation of H2. The control unit 90 controls Q based on the relationship between H2 and V stored in advance and H2_det. For example, the control unit 90 calculates V by substituting H2_det as the value of H2 into the relationship formula between H2 and V stored in advance, and controls Q so as to be equal to the calculated V.

[0031] Note that the control unit 90 may perform the following liquid level height control to obtain the relationship between H2 and V. The liquid level height control is feedback control, and controls the supply flow rate Q of pure water so that the detected value H2_det of the liquid level height H2 becomes the set value H2_ref. Q that fixes H2 is V. The liquid level height control is performed in a state where the substrate W is not immersed in the phosphoric acid aqueous solution L in the inner tank 21 and the phosphoric acid supply unit 55 has stopped supplying phosphoric acid. Also, the liquid level height control is performed in a state where the temperature of the phosphoric acid aqueous solution L is stabilized.

[0032] The control unit 90 repeatedly performs the above liquid level height control while changing the set value H2_ref of the liquid level height H2 in order to obtain the relationship between H2 and V. At this time, it is preferable to gradually decrease the set value H2_ref of the liquid level height H2. Before and after the control unit 90 changes the set value H2_ref of the liquid level height H2, the discharge unit 59 only discharges a part of the phosphoric acid aqueous solution L to the outside of the substrate processing apparatus 1, and the liquid level height H2 can be decreased while maintaining the phosphoric acid concentration C constant.

[0033] As mentioned above, the evaporation amount V is expressed by a linear equation of the liquid level H2. Therefore, the ratio R of the change amount ΔV of the evaporation amount V to the change amount ΔH2 of the liquid level H2 is ΔV / ΔH2 (R ΔV / ΔH2 =ΔV / ΔH2) is constant (negative).

[0034] The control unit 90 determines the ratio R ΔV / ΔH2 is stored in advance, and the ratio R ΔV / ΔH2 The supply flow rate Q of the pure water may be corrected based on the amount of change ΔH2_det in H2_det and H2_det. ΔV / ΔH2 and the product of the change ΔH2_det (R ΔV / ΔH2 × ΔH2_det). Even if the liquid level height H2 fluctuates and the evaporation amount V fluctuates, pure water can be replenished at a flow rate equivalent to the evaporation amount V.

[0035] The control unit 90 may correct the supply flow rate Q of pure water only when ΔH2_det falls below a lower limit value or exceeds an upper limit value. The lower limit value and the upper limit value are determined taking into consideration the detection error of H2. Correcting Q may be performed multiple times until H2 is stabilized. Note that, if H2 is not stabilized even after correcting Q a set number of times, the control unit 90 may stop correcting Q and perform control to output an alarm.

[0036] The control unit 90 may perform a correction to reduce the supply flow rate Q of pure water when the substrate W is immersed in the phosphoric acid aqueous solution L in the inner bath 21. When the substrate W is immersed in the phosphoric acid aqueous solution L, an amount of the phosphoric acid aqueous solution L equivalent to the volume of the substrate W overflows from the inner bath 21 to the outer bath 22. As a result, the liquid level H2 of the phosphoric acid aqueous solution L in the outer bath 22 increases, and the evaporation amount V of water per unit time in the phosphoric acid aqueous solution L decreases. By reducing the supply flow rate Q of pure water, pure water can be replenished at a flow rate equivalent to the evaporation amount V, and fluctuations in the phosphoric acid concentration C can be suppressed.

[0037] The control unit 90 may calculate the correction amount (decrease amount) of Q during immersion based on the number N of substrates W immersed in the phosphoric acid aqueous solution L. As shown in FIG. 4, ΔH2 (ΔH2 = H2a - H2b) is proportional to the number N of substrates W. Here, H2a is H2 immediately after immersion, and H2b is H2 immediately before immersion. The ratio R of ΔH2 to N ΔH2 / N (R ΔH2 / N = ΔH2 / N) is constant.

[0038] For example, the control unit 90 may store R ΔH2 / N in advance, and calculate the decrease amount of Q during immersion based on R ΔH2 / N , R ΔV / ΔH2 , and N. The magnitude of the decrease amount is, for example, the absolute value of the product (R ΔH2 / N × R ΔV / ΔH2 × N) of R ΔH2 / N , R ΔV / ΔH2 , and N. During the immersion of the substrate W, pure water can be supplied at a flow rate corresponding to the evaporation amount V, and fluctuations in the phosphoric acid concentration C can be suppressed.

[0039] In addition, the control unit 90 may perform correction to increase the supply flow rate Q of pure water when pulling up the substrate W from the phosphoric acid aqueous solution L. When the substrate W is pulled up from the phosphoric acid aqueous solution L, an amount of the phosphoric acid aqueous solution L corresponding to the volume of the substrate W is sent from the outer tank 22 to the inner tank 21. As a result, the liquid level height H2 of the phosphoric acid aqueous solution L in the outer tank 22 decreases, and the evaporation amount V of water per unit time in the phosphoric acid aqueous solution L increases. By increasing the supply flow rate Q of pure water, pure water can be supplied at a flow rate corresponding to the evaporation amount V, and fluctuations in the phosphoric acid concentration C can be suppressed.

[0040] For example, the control unit 90 may calculate the correction amount (increase amount) of Q during pulling up based on the number N of substrates W immersed in the phosphoric acid aqueous solution L. For example, the control unit 90 may store R ΔH2 / N in advance, and calculate the increase amount of Q during pulling up based on R ΔH2 / N , R ΔV / ΔH2 , and N. The magnitude of the increase amount of Q during pulling up may be the same as the magnitude of the decrease amount of Q during immersion, but it is preferably larger as will be described later.

[0041] When the substrate W is lifted from the phosphoric acid aqueous solution L, the phosphoric acid aqueous solution L adhering to the substrate W is taken out of the treatment tank 20. The amount A taken out is proportional to the number N of substrates W (see Fig. 5). This is because the amount of the phosphoric acid aqueous solution L adhering to the substrate W is proportional to the number N of substrates W. As shown in Fig. 5, the ratio R A / N (R A / N =A / N) is constant. Also, as shown in Fig. 6, as the amount A of the phosphoric acid aqueous solution L taken out increases, the liquid level height H2 of the phosphoric acid aqueous solution L in the outer tank 22 decreases. The ratio R ΔH2 / ΔA (R ΔH2 / ΔA =ΔH2 / ΔA) is constant.

[0042] Therefore, the control unit 90 may calculate the correction amount (increase amount) of Q at the time of lifting based on the amount A taken out. The magnitude of the increase amount is, for example, the absolute value of the product of R ΔH2 / N and R ΔV / ΔH2 and N (R ΔH2 / N ×R ΔV / ΔH2 ×N), and the sum of the absolute value of the product of R ΔH2 / ΔA and R A / N and N and R ΔV / ΔH2 and (R ΔH2 / ΔA ×R A / N ×N×R ΔV / ΔH2 ). The magnitude of the increase amount of Q at the time of lifting is larger than the magnitude of the decrease amount of Q at the time of immersion by the amount of the product (R ΔH2 / ΔA ×R A / N ×N×R ΔV / ΔH2 ).

[0043] Next, with reference to FIG. 7, an example of the temporal changes in the phosphoric acid concentration C, the pure water supply flow rate Q, and the liquid level height H2 during flow control will be described. The control unit 90 monitors the liquid level height H2 with the liquid level sensor 25 during flow control, and controls the pure water supply flow rate Q based on the liquid level height H2. During immersion, since the liquid level height H2 increases, the control unit 90 reduces the pure water supply flow rate Q. Also, during lifting, since the liquid level height H2 decreases, the control unit 90 increases the supply flow rate Q of pure water. Furthermore, during lifting, since the substrate W takes out the phosphoric acid aqueous solution L adhering to the substrate W outside the processing tank 20, the liquid level height H2 decreases compared to before immersion. Therefore, it is preferable that the magnitude of the increase in Q during lifting is larger than the magnitude of the decrease in Q during immersion. By controlling the pure water supply flow rate Q based on the liquid level height H2 in this way, fluctuations in the phosphoric acid concentration C can be suppressed without referring to the detected value C_det of the phosphoric acid concentration C.

[0044] Next, with reference to FIGS. 8 and 9, a modified example of the substrate processing apparatus 1 will be described. Hereinafter, the differences from the above-described embodiment will be mainly described. The substrate processing apparatus 1 includes a plurality of substrate processing units 10, and an inspection line 60 for each substrate processing unit 10. The substrate processing apparatus 1 also includes a concentration sensor 65 and a switching valve 69 that switches the inspection line 60 connected to the concentration sensor 65. Thereby, using one concentration sensor 65, fluctuations in the phosphoric acid concentration C in a plurality of substrate processing units 10 can be suppressed.

[0045] As shown in FIG. 9, so that the periods of performing concentration control in the plurality of substrate processing units 10A, 10B, and 10C do not overlap, the control unit 90 creates plans for the preparation, concentration control, and flow control of the phosphoric acid aqueous solution L for each of the substrate processing units 10A, 10B, and 10C. The flow control plan includes a plan for immersing the substrate W. The control unit 90 performs the preparation, concentration control, and flow control of the phosphoric acid aqueous solution L according to the created plans. Thereby, the processing efficiency of the substrate W can be improved.

[0046] When an abnormality occurs in the phosphoric acid concentration C, the loading of the unprocessed substrate W into the substrate processing unit 10 where the abnormality has occurred is stopped, and the discharge and preparation of the phosphoric acid aqueous solution L are performed. Thereafter, the concentration control and the flow rate control are performed in this order in the substrate processing unit 10 where the abnormality has occurred. Then, the substrate W is immersed during the flow rate control.

[0047] As described above, the embodiments of the substrate processing apparatus and the substrate processing method according to the present disclosure have been described, but the present disclosure is not limited to the above embodiments. Within the scope described in the claims, various changes, modifications, substitutions, additions, deletions, and combinations are possible. Naturally, those also belong to the technical scope of the present disclosure.

Description of Reference Numerals

[0048] 1 Substrate processing apparatus 10 Substrate processing unit 20 Processing tank 21 Inner tank 22 Outer tank 25 Liquid level sensor 30 Circulation line 50 Pure water supply unit 90 Control unit

Claims

1. A substrate processing apparatus comprising: a substrate processing unit configured to immerse a substrate in a phosphoric acid aqueous solution; and a control unit configured to control the substrate processing unit, wherein the substrate processing unit includes: a processing tank having an inner tank for storing the phosphoric acid aqueous solution and an outer tank for collecting the phosphoric acid aqueous solution that overflows from the inner tank; a circulation line for sending the phosphoric acid aqueous solution taken out from the outer tank back to the inner tank; a liquid level sensor for detecting a liquid level height H2 of the phosphoric acid aqueous solution in the outer tank; and a pure water supply unit for supplying pure water to the processing tank, and the substrate is immersed in the phosphoric acid aqueous solution inside the inner tank, the control unit controls a supply flow rate Q of the pure water based on a detected value H2_det of the liquid level height H2.

2. The control unit stores in advance a relationship between the liquid level height H2 and an evaporation amount V of water per unit time in the phosphoric acid aqueous solution, and controls the supply flow rate Q of the pure water based on the relationship and the detected value H2_det. The substrate processing apparatus according to claim 1.

3. The control unit has a ratio R of the change amount ΔV of the evaporation amount V to the change amount ΔH2 of the liquid level height H2 ΔＶ／ΔＨ２ (R ΔＶ／ΔＨ２ = ΔV / ΔH2) stored in advance, and corrects the supply flow rate Q of pure water based on the ratio R ΔＶ／ΔＨ２ and the change amount of the detection value H2_det. The substrate processing apparatus according to claim 2

4. The control unit performs correction to reduce the supply flow rate Q of the pure water when the substrate is immersed in the phosphoric acid aqueous solution, and correction to increase the supply flow rate Q of the pure water when the substrate is lifted out of the phosphoric acid aqueous solution. The substrate processing apparatus according to claim 1.

5. The control unit calculates a correction amount of the supply flow rate Q of the pure water based on the number N of substrates. The substrate processing apparatus according to claim 4.

6. The control unit calculates a correction amount of the supply flow rate Q of the pure water based on an amount A of the phosphoric acid aqueous solution that the substrate takes out of the processing tank when the substrate is lifted out of the phosphoric acid aqueous solution. The substrate processing apparatus according to claim 4.

7. The apparatus includes a plurality of the substrate processing units, and each substrate processing unit is provided with an inspection line branched from the circulation line for sending the phosphoric acid aqueous solution flowing through the circulation line to the outer tank, and includes a concentration sensor for detecting a phosphoric acid concentration of the phosphoric acid aqueous solution flowing through the inspection line, and a switching valve for switching the inspection line connected to the concentration sensor. The substrate processing apparatus according to claim 1.

8. The substrate processing unit includes a phosphoric acid supply unit for supplying phosphoric acid to the processing tank. The substrate processing apparatus according to claim 7, wherein the control unit performs concentration control for controlling the supply flow rate Q of pure water such that a detected value C_det of the phosphoric acid concentration C becomes a set value C_ref in a state where the substrate is not immersed in the phosphoric acid aqueous solution in the inner tank and the supply of the phosphoric acid by the phosphoric acid supply unit is stopped.

9. The control unit according to claim 8 performs control for calculating an average value of the supply flow rate of pure water in at least a part of the period during which the concentration control is performed, and flow rate control for controlling the supply flow rate of pure water based on the calculated average value after the concentration control.

10. The control unit performs control for calculating an average value of the supply flow rate of pure water in a part of the period during which the concentration control is performed. The substrate processing apparatus according to claim 9, wherein the part of the period is a period immediately before the end of the period during which the concentration control is performed.

11. The substrate processing apparatus according to claim 8, wherein periods during which the concentration control is performed do not overlap in the plurality of substrate processing units.

12. A substrate processing method, comprising immersing the substrate in the phosphoric acid aqueous solution inside the inner tank using the substrate processing apparatus according to any one of claims 1 to 11.

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