A substrate processing apparatus includes: a processing container to which a supercritical fluid is supplied, the processing container being configured to dry a substrate by replacing a drying liquid collected on the substrate with the supercritical fluid; a discharge line configured to discharge a mixed fluid containing the supercritical fluid and the drying liquid from an interior of the processing container; and a density detector configured to detect a density of the mixed fluid flowing through the discharge line.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority from Japanese Patent Application Nos. 2021-042031 and 2021-196119, filed on Mar. 16, 2021 and Dec. 2, 2021, respectively, the entire contents of which are incorporated herein by reference.

TECHNICAL FIELD

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

BACKGROUND

The substrate processing apparatus disclosed in Patent Document 1 includes a drying part, a discharge line, an acquisition part, and a detection part. The drying part dries a substrate by bringing the substrate, the surface of which is wet with liquid, into contact with a supercritical fluid and replacing the liquid with the supercritical fluid. The discharge line is provided in the drying part to discharge the fluid from the drying part. The acquisition part is provided in the discharge line to acquire optical information about the fluid discharged from the drying part. The detection part detects the presence or absence of liquid inside the drying part based on the optical information acquired by the acquisition part.

PRIOR ART DOCUMENT

Patent Document

Patent Document 1: International Publication No. WO 2018/173861

SUMMARY

According to one embodiment of the present disclosure, there is provided a substrate processing apparatus includes: a processing container to which a supercritical fluid is supplied, the processing container being configured to dry a substrate by replacing a drying liquid collected on the substrate with the supercritical fluid; a discharge line configured to discharge a mixed fluid containing the supercritical fluid and the drying liquid from an interior of the processing container; and a density detector configured to detect a density of the mixed fluid flowing through the discharge line.

DETAILED DESCRIPTION

Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In each drawing, the same or corresponding components may be denoted by the same reference numerals, and a description thereof may be omitted. Herein, the term “upstream” means upstream direction of the flow of a supercritical fluid, and the term “downstream” means downstream direction of the flow of a supercritical fluid. In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the present disclosure. However, it will be apparent to one of ordinary skill in the art that the present disclosure may be practiced without these specific details. In other instances, well-known methods, procedures, systems, and components have not been described in detail so as not to unnecessarily obscure aspects of the various embodiments.

First, a substrate processing apparatus1of the present embodiment will be described with reference toFIGS.1and2. The substrate processing apparatus1dries a substrate W by replacing a drying liquid collected on the substrate W with a supercritical fluid. The supercritical fluid is a fluid that is placed under a temperature higher than a critical temperature and a pressure higher than a critical pressure, and is a fluid in the state in which a liquid and a gas are not distinguishable from each other. By replacing the drying liquid with the supercritical fluid, it is possible to suppress the appearance of a liquid-gas interface in a concave-convex pattern of the substrate W. As a result, it is possible to suppress the generation of surface tension, and thus it is possible to suppress the collapse of the concave-convex pattern. The drying liquid is, for example, an organic solvent such as isopropyl alcohol (IPA), and the supercritical fluid is, for example, CO2.

As illustrated inFIG.2, the substrate processing apparatus1includes a processing container21, a holder22, and a lid23. The processing container21accommodates therein the substrate W on which a drying liquid is collected. The processing container21is provided with an opening24through which the substrate W is transferred. The holder22holds the substrate W horizontally with a liquid film of the drying liquid orientated upward inside the processing container21. The lid23closes the opening24of the processing container21. Since the lid23and the holder22are connected to each other, the holder22moves together with the lid23.

The processing container21defines a space therein. Supply ports26A and26B and a discharge port28are provided in the wall of the processing container21. The supply ports26A and26B are connected to a supply line L1illustrated inFIG.1. The supply line L1supplies the supercritical fluid to the processing container21. The discharge port28is connected to a discharge line L2illustrated inFIG.1.

The supply port26A is connected to a side surface of the processing container21on the side opposite to the opening24. The supply port26B is connected to a bottom surface of the processing container21. The discharge port28is connected to a lower side of the opening24. Although two supply ports26A and26B and one discharge port28are illustrated inFIGS.1and2, the number of supply ports26A and26B and the number of discharge ports28, and positions thereof are not particularly limited.

Inside the processing container21, supply headers31A and31B and a discharge header33are provided. Each of the supply headers31A and31B and the discharge header33includes a large number of openings formed therein.

The supply header31A is connected to the supply port26A and provided inside the processing container21to be adjacent to the side surface opposite to the opening24. The large number of openings formed in the supply header31A face the opening24.

The supply header31B is connected to the supply port26B and provided in the center of the bottom surface inside the processing container21. The large number of openings formed in the supply header31B face upward.

The discharge header33is connected to the discharge port28, and provided inside the processing container21to be adjacent to the side surface of the processing container21on the side of the opening24and below the opening24. In addition, the large number of openings formed in the discharge header33face the supply header31A.

The supply headers31A and31B supply the supercritical fluid to the interior of the processing container21. In addition, the discharge header33discharges the fluid inside the processing container21to the outside. The fluid discharged to the outside by the discharge header33includes the supercritical fluid, and further includes vapors of the drying liquid dissolved in the supercritical fluid.

As illustrated inFIG.1, the substrate processing apparatus1includes the supply line L1. The supply line L1connects a fluid source and the processing container21. The supercritical fluid is supplied to the supply line L1from the fluid source. The supply line L1is provided with a heater HE The heater H1maintains the supercritical fluid supplied to the processing container21at the critical temperature or higher. The heater H1is provided, for example, over the entire supply line L1.

The supply line L1includes a common line L1a, a distribution line L1b, and a boost line L1c. An upstream end of the common line L1ais connected to the fluid source, and a downstream end of the common line L1ais connected to the distribution line L1band the boost line L1c. The distribution line L1bis connected to the supply port26A, and the boost line L1cis connected to the supply port26B.

The distribution line L1bis provided with an opening/closing valve52aand a temperature sensor TS. The opening/closing valve52aopens/closes a fluid flow path. When the opening/closing valve52aopens the fluid flow path, the supercritical fluid is supplied into the processing container21via the supply port26A and the supply header31A (seeFIG.2). Meanwhile, when the opening/closing valve52acloses the fluid flow path, the supply of the supercritical fluid into the processing container21is stopped.

Similarly, the boost line L1cis provided with an opening/closing valve52band a temperature sensor TS. The opening/closing valve52bopens/closes the fluid flow path. When the opening/closing valve52bopens the fluid flow path, the supercritical fluid is supplied into the processing container21via the supply port26B and the supply header31B (seeFIG.2). Meanwhile, when the opening/closing valve52bcloses the fluid flow path, the supply of the supercritical fluid into the processing container21is stopped.

Although the distribution line L1band the boost line L1care separately provided in the present embodiment, they may be integrated with each other.

The substrate processing apparatus1includes the discharge line L2. The discharge line L2discharges the fluid inside the processing container21. The discharge line L2A is provided with a heater H2. The heater H2suppresses a change in temperature of the fluid flowing through the discharge line L2to suppress the liquefaction of the fluid. The heater H2is provided, for example, over the entire discharge line L2.

The discharge line L2includes, for example, an opening/closing line L2a, a first common line L2c, a first intermediate line L2d, a second intermediate line L2e, a third intermediate line L2f, and a second common line L2g.

The opening/closing line L2aextends from the discharge port28of the processing container21to the upstream end of the first common line L2c. The opening/closing line L2ais provided with an opening/closing valve52c, a temperature sensor TS, and a pressure sensor PS. The opening/closing valve52copens/closes the fluid flow path. When the opening/closing valve52copens the fluid flow path, the fluid inside the processing container21is discharged outside the substrate processing apparatus1via the discharge header33(seeFIG.2) and the discharge port28. Meanwhile, when the opening/closing valve52ccloses the fluid flow path, the discharge of the fluid from the processing container21is stopped.

The first common line L2cis provided with a pressure-reducing valve53, a flow meter54, a temperature sensor TS, and a pressure sensor PS. The pressure-reducing valve53reduces a pressure of the fluid on the downstream side of the pressure-reducing valve53to be lower than a pressure of the fluid on the upstream side of the pressure-reducing valve53. The pressure on the upstream side of the pressure-reducing valve53is, for example, 14 MPa to 18 MPa, and the pressure on the downstream side of the pressure-reducing valve53is, for example, 0.1 MPa to 0.5 MPa. The flow meter54measures a flow rate of the fluid before the pressure is reduced, but may measure a flow rate of the fluid after the pressure is reduced.

Each of the first intermediate line L2d, the second intermediate line L2e, and the third intermediate line L2fextends from the downstream end of the first common line L2cto the upstream end of the second common line L2g.

The first intermediate line L2dis provided with an opening/closing valve52e, a check valve55a, and an orifice56. The opening/closing valve52eopens/closes the fluid flow path. When the opening/closing valve52eopens the fluid flow path, the fluid inside the processing container21passes through the opening/closing valve52eand is discharged outside the substrate processing apparatus1. Meanwhile, when the opening/closing valve52ecloses the fluid flow path, the discharge of the fluid through the first intermediate line L2dis stopped. The check valve55aprevents backflow of the fluid.

Similarly, the second intermediate line L2eis provided with an opening/closing valve52fand a check valve55b. The opening/closing valve52fopens/closes the fluid flow path. When the opening/closing valve52fopens the fluid flow path, the fluid inside the processing container21passes through the opening/closing valve52fand is discharged outside the substrate processing apparatus1. Meanwhile, when the opening/closing valve52fcloses the fluid flow path, the discharge of the fluid through the second intermediate line L2eis stopped. The check valve55bprevents backflow of the fluid.

An opening/closing valve52gis provided in the third intermediate line L2f. The opening/closing valve52gopens/closes the fluid flow path. When the opening/closing valve52gopens the fluid flow path, the fluid inside the processing container21passes through the opening/closing valve52gand is discharged outside the substrate processing apparatus1. Meanwhile, when the opening/closing valve52gcloses the fluid flow path, the discharge of the fluid through the third intermediate line L2fis stopped.

The first intermediate line L2d, the second intermediate line L2e, and the third intermediate line L2fare separately provided in the present embodiment, but may be integrated with each other. However, in the former case, it is possible to finely control the discharge flow rate of the fluid by discharging the fluid through the plurality of opening/closing valves52e,52f, and52g.

The substrate processing apparatus1includes a control device90. The control device90is, for example, a computer, and includes a central processing unit (CPU)91and a storage medium92such as a memory. The storage medium92stores a program for controlling various processes to be executed by the substrate processing apparatus1. The control device90controls the operation of the substrate processing apparatus1by causing the CPU91to execute the program stored in the storage medium92. The storage medium92may be a non-transient computer readable storage device.

Next, a substrate processing method of the present embodiment will be described with reference toFIG.3. Steps S1to S5illustrated inFIG.3are performed under the control of the control device90.

First, in step S1, a transfer device (not illustrated) loads the substrate W on which the drying liquid is collected into the substrate processing apparatus1. The holder22receives the substrate W from the transfer device and holds the same horizontally with the liquid film of the drying liquid facing upward. The substrate W is accommodated in the processing container21, and the lid23closes the opening24of the processing container21.

Subsequently, in step S2, the supply line L1supplies the supercritical fluid into the processing container21through the supply port26B and the supply header31B, thereby increasing an internal pressure of the processing container21. At that time, the supercritical fluid is supplied from below the substrate W so as to prevent the drying liquid collected on the substrate W from being disturbed. The internal pressure of the processing container21is increased to a set pressure equal to or higher than the critical pressure. During this time, the discharge line L2does not discharge the fluid inside the processing container21.

Subsequently, in step S3, the supply line L1supplies the supercritical fluid into the processing container21through the supply port26A and the supply header31A, and the discharge line L2discharges the fluid inside the processing container21. Thus, the supercritical fluid is circulated above the substrate W. The drying liquid dissolved in the supercritical fluid is discharged outside the processing container21, and the drying liquid collected on the substrate W is replaced with the supercritical fluid, so the substrate W is dried. At that time, the supply flow rate and the discharge flow rate are equal to each other, and the internal pressure of the processing container21is maintained at the set pressure.

Subsequently, in step S4, the supply line L1stops the supply of the supercritical fluid into the processing container21, and the discharge line L2discharges the fluid inside the processing container21, so the interior of the processing container21is depressurized. The internal pressure of the processing container21is reduced to about atmospheric pressure (0.1 MPa). Thereafter, the lid23opens the opening24of the processing container21, and the substrate W is taken out of the processing container21.

Finally, in step S5, the transfer device (not illustrated) receives the substrate W from the holder22and unloads the same to the outside of the substrate processing apparatus1.

Next, the discharge line L2according to the present embodiment will be described with reference toFIG.4. The discharge line L2discharges a mixed fluid composed of the supercritical fluid and the drying liquid dissolved in the supercritical fluid from the interior of the processing container21in the above-described step S3.

As described above, the discharge line L2includes the opening/closing line L2aand the first common line L2c. The opening/closing line L2ais provided with a pressure sensor PS1, a temperature sensor TS1, and an opening/closing valve52cin this order from the upstream side to the downstream side. In addition, the first common line L2cis provided with a density detector Ma and a pressure-reducing valve53in this order from the upstream side to the downstream side.

The density detector54adetects a density of the mixed fluid flowing through the discharge line L2as an index indicating a concentration of the drying liquid in the mixed fluid flowing through the discharge line L2. The higher the concentration of the drying liquid in the mixed fluid, the higher the density of the mixed fluid. Therefore, when the density of the mixed fluid is detected, the concentration of the drying liquid can be known. That is, the index indicating the concentration of the drying liquid can be obtained.

The density detector54ais provided, for example, on the upstream side of the pressure-reducing valve53. Almost no pressure loss occurs on the upstream side of the pressure-reducing valve53. In addition, there is almost no temperature change due to the pressure loss. Therefore, the density of the mixed fluid can be detected at the same temperature and pressure as the internal temperature and pressure of the processing container21, and thus the concentration of the drying liquid in the interior of the processing container21can be detected more accurately.

The density detector54amay be any density detector as long as it can detect the density of the mixed fluid. As the density detector54a, a density meter for high temperature and high pressure may be used. For example, a gamma ray density meter or the like that measures density with gamma rays may be used.

The density detector54adetects a density D1of the mixed fluid flowing through the discharge line L2every unit time. As a result, time-dependent change data indicated by the solid line inFIG.8Ais obtained. InFIG.8A, the horizontal axis represents the elapsed time from the initiation of step S3, and the vertical axis represents the density (kg/m3).

Subsequently, time-dependent change data of the density D1of the mixed fluid indicated by the solid line inFIG.8Awill be described. After the initiation of step S3, the mixed fluid of the supercritical fluid and the drying liquid dissolved in the supercritical fluid is discharged from the processing container21to the discharge line L2. The density D1increases with time and reaches a peak value.

The peak value of the density D1and the time to reach the peak value depend on an amount of the drying liquid previously collected on the substrate W. The larger the collected amount of the drying liquid, the larger the amount of the drying liquid dissolved in the supercritical fluid, and the larger the peak value of the density D1. In addition, the larger the collected amount of the drying liquid, the longer it takes to dissolve the drying liquid in the supercritical fluid, and the longer it takes for the density D1to reach the peak value.

After the density D1reaches the peak value, as the replacement of the drying liquid with the supercritical fluid progresses on the top surface of the substrate W, the concentration of the drying liquid in the mixed fluid discharged from the processing container21to the discharge line L2decreases. As a result, the density D1decreases. The decrease in the density D1represents a degree to which the replacement of the drying liquid with the supercritical fluid proceeds, and represents a degree to which the drying of the substrate W proceeds. As the drying of the substrate W proceeds, the amount of the remaining drying liquid becomes smaller, and the rate of decrease in the density D1becomes slower.

Next, the function of the control device90will be described with reference toFIG.7. Each functional block illustrated inFIG.7is conceptual and does not necessarily have to be physically configured as illustrated. It is possible to configure all or portion of each functional block to be functionally or physically distributed/integrated in any unit. All or any portion in each processing function performed in each function block may be implemented by a program executed by a CPU, or may be implemented as hardware by wired logic. The control device90includes, for example, a storage95, a reference density calculator96, a density difference calculator97, a drying termination detector98, and a drying abnormality detector99.

The storage95stores time-dependent change data of the density D1detected by the density detector54a. In addition, the storage95stores time-dependent change data of each of a pressure detected by the pressure detector101and a temperature detected by the temperature detector102. The pressure detector101detects the pressure of the mixed fluid flowing through the discharge line L2. The pressure detector101includes, for example, the pressure sensor PS1illustrated inFIG.4. Meanwhile, the temperature detector102detects the temperature of the mixed fluid flowing through the discharge line L2. The temperature detector102includes, for example, the temperature sensor TS1illustrated inFIG.4. The pressure sensor PS1and the temperature sensor TS1are provided, for example, on the downstream side of the processing container21and on the upstream side of the opening/closing valve52c.

The reference density calculator96as a first circuitry calculates a reference density D2, which is the density of the supercritical fluid having the same temperature and the same pressure as those of the mixed fluid flowing through the discharge line L2. The reference density D2is a density of a pure supercritical fluid. Comparing the density D1and the reference density D2of the mixed fluid at the same temperature and the same pressure, the reference density D2is smaller. A density difference ΔD between the density D1of the mixed fluid and the reference density D2indicates the concentration of the drying liquid in the mixed fluid. The higher the concentration of the dry liquid, the larger the density difference ΔD. The calculation of the reference density D2is performed at every unit time, and time-dependent change data of the reference density D2as shown by the broken line inFIG.8Ais obtained.

FIG.9shows an example of the relationship of the density, pressure, and temperature of a pure supercritical fluid. As shown inFIG.9, when the pressure is constant, the higher the temperature, the lower the density. In addition, when the temperature is constant, the higher the pressure, the higher the density. The relationship of the density, the pressure, and the temperature of the supercritical fluid is obtained in advance by experiment or the like and stored in the storage medium92. This relationship may be stored in the form of an equation. The equation is commonly referred to as a state equation. The reference density calculator96calculates the reference density D2by referring to the equation stored in the storage medium92or the like.

The density detector54adetects the density D1of the mixed fluid when the mixed fluid passes through the density detector54a. Therefore, the reference density calculator96calculates the reference density D2to be compared with the density D1based on the pressure and temperature when the mixed fluid passes through the density detector54a. For example, the reference density calculator96calculates the reference density D2based on the pressure detected by the pressure detector101and the temperature detected by the temperature detector102.

The reference density calculator96may use the pressure itself detected by the pressure sensor PS1as the pressure when the mixed fluid passes through the density detector54a. Alternatively, the reference density calculator96may obtain the pressure when the mixed fluid passes through the density detector54ain consideration of a pressure loss generated between the pressure sensor PS1and the density detector54a.

Similarly, the reference density calculator96may use the temperature itself detected by the temperature sensor TS1as the temperature when the mixed fluid passes through the density detector54a. Alternatively, the reference density calculator96may obtain the temperature when the mixed fluid passes through the density detector54ain consideration of a temperature change generated between the temperature sensor TS1and the density detector54a.

Almost no pressure loss occurs on the upstream side of the pressure-reducing valve53. Meanwhile, the flow-out of heat occurs on either the upstream side or the downstream side of the pressure-reducing valve53. On the upstream side of the pressure-reducing valve53, the error of the reference density D2is mainly caused by the temperature change according to a moving distance.

As illustrated inFIG.4, the pressure sensor PS1and the temperature sensor TS1are provided on the downstream side of the processing container21and on the upstream side of the opening/closing valve52c. Meanwhile, as illustrated inFIG.5, a pressure sensor PS2and a temperature sensor TS2may be provided on the downstream side of the opening/closing valve52cand on the upstream side of the density detector54a.

When the pressure detector101includes the pressure sensor PS2, the pressure detector101may detect the pressure of the mixed fluid at a position closer to the density detector54acompared to the case of including the pressure sensor PS1. Similarly, when the temperature detector102includes the temperature sensor TS2, the temperature detector102may detect the temperature of the mixed fluid at a position closer to the density detector54acompared to the case of including the temperature sensor TS1. As a result, the reference density D2can be obtained with high accuracy.

As illustrated inFIG.6, a temperature sensor TS3may be provided on the downstream side of the density detector54aand on the upstream side of the pressure-reducing valve53. The temperature sensor TS3is provided in the vicinity of the density detector54a. In addition, a pressure sensor PS3and a temperature sensor TS4may be provided inside the density detector54a. The temperature sensor TS4may detect the temperature of the mixed fluid. The temperature sensor TS4may detect the temperature of the mixed fluid by detecting a temperature of a tube through which the mixed fluid flows.

The temperature detector102may include at least one of the three temperature sensors TS2, TS3, and TS4, and may include all the temperature sensors. When all three temperature sensors TS2, TS3, and TS4are used, the temperature when the mixed fluid passes through the density detector54acan be calculated more accurately.

The density difference calculator97as a second circuitry calculates the density difference ΔD between the density D1of the mixed fluid detected by the density detector54aand the reference density D2calculated by the reference density calculator96. The calculation of the density difference ΔD is performed every unit time, and time-dependent change data of the density difference ΔD indicated by the solid line inFIG.8Bis obtained.

Next, the time-dependent change data of the density difference ΔD indicated by the solid line inFIG.8Bwill be described. After the initiation of step S3, the mixed fluid of the supercritical fluid and the drying liquid dissolved in the supercritical fluid is discharged from the processing container21to the discharge line L2. The density difference ΔD increases with time and reaches a peak value.

The peak value of the density difference ΔD and the time to reach the peak value depend on the collected amount of the drying liquid previously collected on the substrate W. The larger the collected amount of the drying liquid, the larger the amount of the drying liquid dissolved in the supercritical fluid, and the larger the peak value of the density difference ΔD. In addition, the larger the collected amount of the drying liquid, the longer it takes to dissolve the drying liquid in the supercritical fluid, and the longer it takes for the density difference ΔD to reach the peak value.

After the density difference ΔD reaches the peak value, as the replacement of the drying liquid with the supercritical fluid proceeds on the top surface of the substrate W, the concentration of the drying liquid in the mixed fluid discharged from the processing container21to the discharge line L2decreases. As a result, the density difference ΔD decreases. The decrease in the density difference ΔD represents a degree to which the replacement of the drying liquid with the supercritical fluid proceeds, and represents a degree to which the drying of the substrate W proceeds. As the drying of the substrate W proceeds, the amount of the remaining drying liquid becomes smaller, and the rate of decrease in the density difference ΔD becomes slower.

The drying termination detector98as a third circuitry monitors the density D1or the density difference ΔD stored in the storage95, and detects the termination of drying of the substrate W based on the time-dependent change data. The termination of drying of the substrate W refers to the termination of replacement of the drying liquid with the supercritical fluid on the top surface of the substrate W. When the termination of drying of the substrate W is detected, step S4is performed.

For example, the drying termination detector98detects the termination of drying of the substrate W by detecting that the density D1is equal to or less than a threshold value. Alternatively, the drying termination detector98detects the termination of drying of the substrate W by detecting that the density difference ΔD is equal to or less than a threshold value. The detection of the termination of drying of the substrate W may be performed after an elapsed time t from the initiation of step S3reaches a set time t0. The set time t0is set in advance according to the collected amount of the dry liquid previously collected on the substrate W or the like.

Next, an example of a process performed by the drying termination detector98will be described with reference toFIG.10. InFIG.10, the drying termination detector98determines whether or not the drying is terminated based on the density difference ΔD, but may determine whether or not the drying is terminated based on the density D1. In the latter case, inFIG.10, the density difference ΔD may be referred to as the density D1.

First, in step S101, the drying termination detector98checks whether or not the elapsed time t has reached the set time t0. When the elapsed time t has not reached the set time t0(step S101, “NO”), the drying termination detector98repeats the above-described step S101after the lapse of a unit time.

Meanwhile, when the elapsed time t has reached the set time t0(step S101, “YES”), the drying termination detector98calculates the density difference ΔD by the density difference calculator97(step S102). Subsequently, the drying termination detector98determines whether or not the density difference ΔD measured in step S102is equal to or less than a threshold value ΔD0(step S103).

When the density difference ΔD exceeds the threshold value ΔD0(step S103, “NO”), the drying termination detector98determines that the drying of the substrate W is not terminated because the concentration of the drying liquid in the mixed fluid is high (step S105). Thereafter, the circulation in step S3is extended, and the drying termination detector98repeats the above-described step S102.

Meanwhile, when the density difference ΔD is equal to or less than the threshold value ΔD0(steps S103, “YES”), the drying termination detector98determines that the drying of the substrate W is terminated because the concentration of the drying liquid in the mixed fluid is low (step S104). Thereafter, the drying termination detector98terminates the current process. Thereafter, the depressurization in step S4is started.

Since the drying of the substrate W is performed inside the processing container21, it is not possible to directly observe the drying state of the substrate W. Therefore, conventionally, the circulation time in step S3was set longer to reliably terminate the drying of the substrate W before the initiation of depressurization in step S4. This causes unnecessary consumption of time.

According to the present embodiment, by detecting the termination of drying of the substrate W using the drying termination detector98, the initiation timing of depressurization in step S4can be made earlier than that in the conventional case, and thus the throughput can be improved.

The initiation of depressurization in step S4may be prohibited until the drying termination detector98detects the termination of drying of the substrate W. When the initiation timing of depressurization in step S4is erroneously set earlier, the initiation timing can be optimized.

The drying abnormality detector99as a fourth circuitry monitors the density D1or the density difference ΔD stored in the storage95, and detects a drying abnormality of the substrate W based on the time-dependent change data. The drying abnormality of the substrate W includes, for example, an abnormality in the collected amount of the drying liquid previously collected on the substrate W. When the collected amount of the drying liquid is too large, particles may be generated. When the collected amount of the drying liquid is too small, a concave-convex pattern may collapse.

In addition, the drying abnormality detector99may detect an abnormality in the length of the drying time of the substrate W as the drying abnormality of the substrate W. The drying time is the elapsed time t until the density D1or the density difference ΔD reaches the threshold value. When the drying time is too long, it may be considered that the collected amount of the drying liquid previously collected on the substrate W is too large, or a problem has occurred in the substrate processing apparatus1.

Next, an example of a process performed by the drying abnormality detector99will be described with reference toFIG.11. InFIG.11, the drying abnormality detector99determines whether it is normal or abnormal based on the density difference ΔD, but may determine whether it is normal or abnormal based on the density D1. In the latter case, inFIG.11, the density difference ΔD may be referred to as the density D1.

First, in step S201, the drying termination detector99checks whether or not the elapsed time t has reached a set time t1. The set time t1is set such that the density difference ΔD reaches the peak value when there is no drying abnormality. When the elapsed time t has not reached the set time t1(step S201, “NO”), the drying abnormality detector99repeats the above-described step S201after the lapse of a unit time.

Meanwhile, when the elapsed time t has reached the set time t1(step S201, “YES”), the drying abnormality detector99calculates the density difference ΔD by the density difference calculator97(step S202). Subsequently, the drying abnormality detector99determines whether or not the density difference ΔD measured at the time of t=t1is equal to or larger than a lower limit value ΔD1minand equal to or smaller than an upper limit value ΔD1min. (step S203).

When the density difference ΔD at the time of t=t1is equal to or larger than the lower limit value ΔD1minand equal to or smaller than the upper limit value ΔD1min. (steps S203, “YES”), the density difference ΔD is within an allowable range. Thus, the drying abnormality detector99determines that the collected amount of the dry liquid previously collected on the substrate W is normal (step S204). Thereafter, the drying abnormality detector99performs step S206.

When the density difference ΔD at the time of t=t1is smaller than the lower limit value ΔD1minor exceeds the upper limit value ΔD1min. (step S203, “NO”), the density difference ΔD is out of the allowable range. Thus, the drying abnormality detector99determines that the collected amount of the dry liquid previously collected on the substrate W is abnormal (step S205). Thereafter, the drying abnormality detector99performs step S206.

In step S206, the drying abnormality detector99checks whether or not the elapsed time t has reached a set time t2. The set time t2is set such that the concentration of the drying liquid in the mixed fluid is equal to or lower than a threshold value when there is no drying abnormality. The set time t2may be the same as the set time t0shown inFIG.10. When the elapsed time t has not reached the set time t2(step S206, “NO”), the drying abnormality detector99repeats the above-described step S206after the lapse of a unit time.

Meanwhile, when the elapsed time t has reached the set time t2(step S206, “YES”), the drying abnormality detector99calculates the density difference ΔD by the density difference calculator97(step S207). Subsequently, the drying abnormality detector99determines whether or not the density difference ΔD measured at the time of t=t2is ΔD2(step S208). The threshold value ΔD2may be the same as the threshold value ΔD0illustrated inFIG.10.

When the density difference ΔD at the time of t=t2is equal to or smaller than the threshold value ΔD2(step S208, “YES”), the drying abnormality detector99determines that the length of the drying time is normal (step S209). Thereafter, the drying abnormality detector99terminates the current process.

When the density difference ΔD at the time of t=t2exceeds the threshold value ΔD2(step S208, “NO”), the drying abnormality detector99determines that the length of the drying time is abnormal (step S210). Thereafter, the drying abnormality detector99terminates the current process.

When the density difference ΔD at the time of t=t2exceeds the threshold value ΔD2(step S208, “NO”), the circulation in step S3may be extended as inFIG.10.

When the drying time is too long, it may be considered that the collected amount of the drying liquid is too large or a problem has occurred in the substrate processing apparatus1. It is possible to determine which problem has occurred using the result of check in step S203.

That is, when it is determined that the collected amount of the drying liquid is normal as the result of check in step S203, and it is determined that the length of the drying time is abnormal as the result of check in step S208, it may be considered that a problem has occurred in the substrate processing apparatus1.

The substrate W for which the drying abnormality has been detected by the drying abnormality detector99is treated as a defective product, and the subsequent process is stopped. It is possible to prevent an unnecessary process from being performed on defective products.

According to an aspect of the present disclosure, it is possible to obtain an index indicating a concentration of a drying liquid in a mixed fluid.

Although the embodiments or the like of the substrate processing apparatus and the substrate processing method according to the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments or the like. Various changes, modifications, substitutions, additions, deletions, and combinations can be made within the scope of the claims. Of course, these also fall within the technical scope of the present disclosure.