JP6560072B2 - Vacuum drying apparatus and vacuum drying method - Google Patents

Description

  The present invention is for precision electronic devices such as glass substrates for liquid crystal display devices, semiconductor wafers, glass substrates for PDPs, glass substrates for photomasks, substrates for color filters, substrates for recording disks, substrates for solar cells, substrates for electronic paper, etc. The present invention relates to a vacuum drying apparatus and a vacuum drying method for drying a coating film formed on a substrate (hereinafter simply referred to as “substrate”).

  Conventionally, in the manufacturing process of the substrate for precision electronic devices described above, in order to dry the coating film formed on the surface of the substrate, a vacuum drying technique is used in which the solvent component contained in the coating film is vaporized and dried by a vacuum process. It was done. However, as the coating film becomes thicker, the time required for reduced-pressure drying becomes longer, and a more efficient reduced-pressure drying technique is desired. In order to satisfy this demand, a reduced-pressure drying apparatus that performs heat treatment in parallel with the reduced-pressure treatment has been proposed (for example, see Patent Document 1).

  This vacuum drying apparatus has a chamber for storing a substrate on which a coating film is formed in its internal space. The vacuum drying apparatus has a function of decompressing the internal space and a function of heating the internal space. By performing the decompression process and the heating process in parallel, the decompression drying time of the coating film is shortened. ing.

JP 2008-202930 A

  By the way, when the decompression process and the heating process are performed in parallel, a large amount of the solvent component contained in the coating film is vaporized in a short time and is discharged from the internal space via the exhaust pipe connected to the chamber. In Patent Document 1, the exhaust pipe is placed at room temperature, and various problems may occur as will be described in the experiments and analysis described below. For example, it is difficult to shorten the time required for the reduced pressure drying process, the so-called tact time. In addition, the tact time varies for each vacuum drying process, and the vacuum drying process becomes unstable.

  This invention is made in view of the said subject, and provides the reduced pressure drying apparatus and reduced pressure drying method which can perform the reduced pressure drying process which performs pressure reduction and a heating in parallel in a short time, and also stably. Objective.

One aspect of the present invention is to depressurize the internal space and heat the internal space by exhausting the atmosphere of the internal space through the exhaust pipe connected to the chamber while storing the substrate in the internal space of the chamber. the solvent component contained in the coating film on the substrate is vaporized by a vacuum drying apparatus for drying the coated film, provided with a pipe heating part for heating the exhaust pipe from the outer peripheral surface of the exhaust pipe, the pipe heating section, the chamber The exhaust pipe is heated so that the temperature of the exhaust pipe increases as the distance from the engine increases .

Another aspect of the present invention is a vacuum drying method, comprising: a housing step of housing a substrate on which a coating film is formed in an internal space of a chamber; and an atmosphere of the internal space via an exhaust pipe connected to the chamber The internal space is decompressed and the internal space is heated, and the solvent component contained in the coating film on the substrate is vaporized to dry the coating film, and the chamber is separated from the chamber in parallel with the drying process. And a pipe heating step for heating the exhaust pipe from the outer peripheral surface side of the exhaust pipe so as to increase the temperature of the exhaust pipe .

  When performing not only the decompression process but also the heat process in parallel in the internal space of the chamber, the solvent component is efficiently vaporized from the coating film on the substrate and is discharged from the chamber through the exhaust pipe. If the exhaust pipe is at room temperature at the time of discharge, the vaporized solvent component is liquefied and adheres to the exhaust pipe. However, in the present invention, since the exhaust pipe is heated, liquefaction of the solvent component can be suppressed, and the coating film can be stably dried in a short time.

It is a longitudinal cross-sectional view which shows the structure of one Embodiment of the reduced pressure drying apparatus concerning this invention. It is a block diagram which shows the structure of the reduced pressure drying apparatus shown in FIG. It is a graph which shows the pressure reduction characteristic in the vacuum drying apparatus shown in FIG. It is a graph which shows an example of the vapor pressure curve of a solvent. It is a flowchart which shows operation | movement of the reduced pressure drying apparatus shown in FIG.

  FIG. 1 is a longitudinal sectional view showing a configuration of an embodiment of a reduced pressure drying apparatus according to the present invention. FIG. 2 is a block diagram showing the configuration of the vacuum drying apparatus shown in FIG. The reduced-pressure drying apparatus 1 is an apparatus that evaporates a solvent component contained in a coating film 92 formed by applying a coating liquid on the upper surface 91 of the substrate 9 to dry the coating film 92. For example, when a polyimide film is formed on the upper surface 91 of the substrate 9, polyamic acid (polyamic acid) which is a polyimide precursor is used as an organic solvent, for example, NMB (N-Methyl-2-pyrrolidone: N-Methyl-2-Pyrrolidone). ) Is used as a coating solution. The coating solution is applied to form a relatively thick coating film having a thickness about 10 times the desired thickness (for example, about 50 to 100 [μm] when a polyimide film of about 5 to 10 [μm] is formed). . Then, the solvent component contained in the coating film is vaporized and removed by the reduced-pressure drying apparatus 1 and further heated at a high temperature by a heating apparatus different from the reduced-pressure drying apparatus 1 to imidize the polyimide film on the upper surface 91 of the substrate 9. Is formed. As described above, the reduced pressure drying apparatus 1 according to the present invention can dry the relatively thick coating film 92 under reduced pressure, and is particularly suitable when a large amount of solvent components are vaporized during the reduced pressure drying process.

  As shown in FIG. 1, the vacuum drying apparatus 1 includes a chamber 10, a substrate holding unit 20, a substrate heating unit 30, an exhaust unit 40, a pipe heating unit 50, and a control unit 60 (FIG. 2).

  The chamber 10 is a pressure vessel having an internal space SP for performing a reduced-pressure drying process (= depressurization process + heating process) on the substrate 9. The chamber 10 has a base portion 11 and a lid portion 12 that are separable from each other. The base portion 11 is fixedly installed on an apparatus frame (not shown). Further, the lid 12 is connected to a chamber lifting mechanism 12a conceptually shown in FIG. For this reason, the lid 12 moves up and down with respect to the base 11 by operating the chamber lifting mechanism 12 a according to the lifting command from the controller 60. When the lid portion 12 is lowered, the base portion 11 and the lid portion 12 come into contact with each other, and an internal space SP (processing space for the substrate 9) is formed therein. In the present embodiment, an O-ring 13 made of silicon rubber or the like is provided on the peripheral edge portion of the upper surface of the base portion 11. For this reason, when the lid portion 12 is lowered, the O-ring 13 is interposed between the upper surface of the base portion 11 and the lower surface of the lid portion 12, and the chamber 10 internal space SP is in an airtight state. On the other hand, when the lid 12 is raised, the chamber 10 is opened, and the substrate 9 can be carried into and out of the chamber 10.

  The substrate holding unit 20 is a mechanism for holding the substrate 9 in the internal space SP of the chamber 10. The substrate holding unit 20 has a plurality of substrate holding pins 21, and supports the substrate 9 in a horizontal posture by bringing the head of each substrate holding pin 21 into contact with the lower surface of the substrate 9. The plurality of substrate holding pins 21 are erected on one support member 22 arranged outside the chamber 10, and protrude through the base portion 11 and the substrate heating portion 30 into the internal space SP of the chamber 10. It is installed.

  As shown in FIG. 1, a pin elevating mechanism 22a is connected to the support member 22. For this reason, the pin elevating mechanism 22a operates in accordance with the elevating command from the control unit 60, whereby the support member 22 and the plurality of substrate holding pins 21 move up and down as a unit. In the vacuum drying apparatus 1, it is possible to adjust the height position of the substrate 9 relative to the substrate heating unit 30 by operating the pin lifting mechanism 22 a while holding the substrate 9 on the plurality of substrate holding pins 21. Yes.

  The substrate heating unit 30 is arranged at the center of the upper surface of the base unit 11. In the substrate heating unit 30, a plurality of rod heaters serving as heating sources are provided. If the rod heater is operated in accordance with a heating command from the control unit 60 before the substrate 9 is loaded into the plurality of substrate holding pins 21, the internal space SP is heated before the substrate 9 is loaded. At the same time, the loaded substrate 9 is heated from the lower surface side. In this way, the substrate 9 is heated in the internal space SP where the ambient temperature has risen, and the solvent component is vaporized from the coating film 92.

  Moreover, in this embodiment, in order to perform a pressure reduction process in parallel with a heat processing, the exhaust part 40 is provided. The exhaust unit 40 includes an exhaust pipe 41 for sucking and exhausting a gas containing a solvent component (hereinafter referred to as “exhaust gas”) from the internal space SP of the chamber 10, and exhaust exhausted from the chamber 10 via the exhaust pipe 41. It has butterfly valves 42 and 43 for controlling the exhaust amount of gas, an on-off valve 44, and an exhaust pump 45. In the present embodiment, two exhaust ports 111 and 112 are provided in the peripheral edge portion of the base portion 11. Corresponding to the provision of two exhaust ports in this way, one end portion of the exhaust pipe 41 branches into two, and the branch end portions 411 and 412 are connected to the exhaust ports 111 and 112, respectively. Further, butterfly valves 42 and 43 are inserted into the branch end portions 411 and 412 at positions near the exhaust ports 111 and 112, respectively. On the other hand, the other end of the exhaust pipe 41 is connected to an exhaust line (not shown) via an on-off valve 44 and an exhaust pump 45. For this reason, when the on-off valve 44 is opened according to the opening / closing command from the control unit 60 and the exhaust pump 45 is operated according to the operation command from the control unit 60, the exhaust amount according to the opening degree of the butterfly valves 42, 43 is obtained. Exhaust gas is exhausted to the exhaust line via the exhaust pipe 41.

  In the present embodiment, the exhaust pipe 41 is provided with a pipe heating unit 50. The pipe heating unit 50 is obtained by winding a rubber heater around the outer peripheral surface of the exhaust pipe 41 as a pipe heater 51. The exhaust pipe 41 is heated when the pipe heater 51 generates heat in response to a heating command from the control unit 60. As the piping heater 51, a ribbon heater, a cable heater, a seat heater, or the like may be used in addition to the rubber heater.

  In order to adjust the exhaust pipe 41 with high accuracy, in this embodiment, as shown in FIG. 2, a pipe temperature sensor 41a for detecting the temperature of the exhaust pipe 41 is provided, and a detection signal related to the detected temperature. Is output to the control unit 60. And the control part 60 adjusts the temperature of the exhaust piping 41 by feedback-controlling the air piping heating part 50 based on the temperature of the exhaust piping 41 in parallel with a decompression drying process, and is a solvent component contained in exhaust gas Is prevented from touching the exhaust pipe 41 and liquefying. Thus, in this embodiment, the control unit 60 functions as the “pipe temperature control unit” of the present invention. In the following, before explaining the operation of the vacuum drying apparatus 1 configured as described above, the technical significance of heating and adjusting the temperature of the exhaust pipe 41 by the air pipe heating unit 50 will be described with reference to FIGS. 3 and 4. Will be described with reference to FIG.

  FIG. 3 is a graph showing the pressure reduction characteristics in the vacuum drying apparatus shown in FIG. 1, and the pressure reduction characteristics are obtained by the following experiment. In the initial stage of the reduced pressure drying process, the solvent component is rapidly vaporized from the coating film 92, but the reduced pressure operation is executed with an exhaust amount corresponding to the solvent component. For this reason, the pressure in the chamber 10 decreases, and the pressure gradually decreases as the vacuum drying process proceeds, and the vacuum drying process of the coating film 92 is completed. Therefore, in this experiment, the three substrates 9 were continuously subjected to the reduced-pressure drying process while setting the same except for the condition that the pipe heater 51 was turned on / off, and a constant value Ps (atmospheric pressure in this experiment). (100,000 Pa)) until the vacuum drying process of the coating film 92 was completed, the change in the pressure in the chamber 10 was measured. The upper waveform in the figure shows the pressure reduction characteristic when the pipe heater 51 is not operated (OFF), and the lower waveform shows the pressure reduction characteristic when the pipe heater 51 is operated (ON).

  In the vacuum drying apparatus 1, the exhaust gas containing the solvent component generated in the chamber 10 is exhausted from the chamber 10 through the exhaust pipe 41, so that the pressure in the chamber 10 decreases with time. Here, there are three points to be noted in the decompression characteristics shown in FIG.

  The first point is that the case where the pipe heater 51 is kept in the OFF state at the initial stage of the pressure decrease (substantially equivalent to the conventional apparatus, hereinafter referred to as “conventional example”) keeps the pipe heater 51 in the ON state. The pressure drop rate is higher than that of the case (corresponding to the present embodiment, hereinafter referred to as “Example”). This is due to the fact that the solvent component contained in the exhaust gas is rapidly cooled and liquefied in the exhaust pipe 41, and the liquefied solvent component is again vaporized and exhausted. The present inventor analyzed. That is, in the embodiment, the pipe heater 51 is turned on, and in the conventional example, the vaporized state is maintained in the embodiment because the liquefied portion adheres to the exhaust pipe 41. It can be considered that the number has increased. In other words, it is considered that the exhaust speed was slower in the early stage of the pressure reduction because the amount of exhaust gas to be exhausted was larger in the embodiment than in the conventional example. As described above, the pressure characteristic is closely related to the temperature of the exhaust pipe 41.

  The second point of interest is that, as described above, the exhaust speed decreases as the temperature of the exhaust pipe 41 increases. However, in the conventional example, after the middle stage of the pressure decrease, the decompression speed decreases and the decompression drying process is completed. The time is longer than that of the example. Here, the inventor of the present application analyzed the cause of the decrease in the decompression speed in the conventional example as follows. That is, when viewing the upper waveform of FIG. 3, the pressure in the chamber 10 greatly decreases immediately before reaching the specific pressure Pv, and after the pressure reduction rate becomes substantially zero at the pressure Pv for a certain time, the pressure decreases again. To do. This is because the solvent component contained in the exhaust gas is rapidly cooled and liquefied in the exhaust pipe 41 as described above, and the liquefied solvent component is again vaporized and exhausted. The inventor of this application analyzed that it was caused. Further, it can be analyzed that heating of the exhaust pipe 41 can suppress the liquefaction of the solvent component to the exhaust pipe 41 and prevent the pressure reduction rate from decreasing, and the analysis result is consistent with the experimental result. . That is, by heating the exhaust pipe 41, it is possible to prevent the solvent component in the exhaust gas from being liquefied in the exhaust pipe 41 and to shorten the time required for the reduced pressure drying process, the so-called tact time.

  Furthermore, the third point of interest is the stability of the vacuum drying process. As shown in the figure, in the conventional example, the vacuum drying end timing Toff differs for each vacuum drying process. That is, the tact time fluctuates. The reason can be analyzed as follows. As described above, the solvent once liquefied in the exhaust pipe 41 is re-vaporized. Therefore, if all the re-vaporized gas is exhausted, the first, second, and third sheets differ in the end timing Toff. Is not expected to occur. However, when the pipe heater 51 is maintained in the OFF state, a large amount of vaporized solvent may be reliquefied and adhere to the exhaust pipe 41 at the time when the pressure is the pressure Pv. Become. In addition, the fact that the pressure falls below the pressure Pv seems to completely vaporize the re-liquefied one, but the drying process is continued even while the pressure drops below the pressure Pv. Re-liquefaction adhesion continues to occur. As a result, it is considered that the adhesion amount increases as the number of sheets increases, and the end timing Toff shifts accordingly. On the other hand, in the embodiment, the end timing Ton is substantially the same, that is, the tact time is substantially constant. This can be attributed to the fact that the pipe heater 51 is in the ON state and liquefaction does not occur in the heated exhaust pipe 41. In fact, as long as the lower waveform of FIG. 3 is seen in the example, liquefaction of the solvent component is not recognized and the tact time is stable. Thus, the heating of the exhaust pipe 41 greatly contributes to the stabilization of the reduced pressure drying process.

  From the above three points of interest and analysis results, the inventor of the present application says that heating the exhaust pipe 41 during the reduced pressure drying process plays an important role in reducing the tact time and stabilizing the reduced pressure drying process. I got a conclusion. From the viewpoint of preventing the liquefaction of the solvent component in the exhaust pipe 41, it is desirable to adjust the exhaust pipe 41 to a temperature higher than the dew point temperature of the exhaust gas. Here, “dew point temperature (or sometimes simply referred to as“ dew point ”)” means that the solvent component is easily liquefied when the exhaust gas temperature is lower than the dew point temperature. Can be prevented from liquefying the solvent component contained in the exhaust gas. Further, if the heating temperature of the exhaust pipe 41 is too high, the exhaust gas expands in the subordinate pipe 41 and causes a reduction in the exhaust speed. Therefore, the temperature of the exhaust pipe 41 is set lower than the internal space SP of the chamber 10. Is desirable.

  Here, since it is difficult to directly detect the dew point temperature in the vacuum drying apparatus 1 shown in FIG. 1, in the present embodiment, the pressure Pv (pressure in the chamber 10 when liquefaction is considered to occur) And the temperature of the exhaust pipe 41 is set based on the vapor pressure curve of the solvent shown in FIG. That is, the temperature TPv corresponding to the pressure Pv is obtained based on the vapor pressure curve, and the control unit 60 drives the pipe heater 51 to heat the exhaust pipe 41 within a range of ± 20 [° C.] of the temperature TPv. Specifically, the temperature of the exhaust pipe 41 during the vacuum drying process is stored in advance in the control unit 60 as the target pipe temperature, and the control unit 60 controls each part of the vacuum drying apparatus 1 according to the program for the vacuum drying process. By doing so, the following operations are executed.

FIG. 5 is a flowchart showing the operation of the vacuum drying apparatus shown in FIG. When the substrate 9 is processed by the vacuum drying apparatus 1, the substrate heating unit 30 receives a heating command from the control unit 60 and operates the rod heater to raise the ambient temperature in the internal space SP in advance (step). S1: Heat preparation step). The heat treatment for the exhaust pipe 41 is also started in advance (step S2: pipe heating process). That is, the pipe heating unit 50 receives a heating command from the control unit 60 and operates the pipe heater 51 to It heats from the outer peripheral surface side and raises the temperature of the exhaust pipe 41. Here, the control unit 60 monitors the temperature of the exhaust pipe 41 detected by the pipe temperature sensor 41a, and performs feedback control based on the temperature so that the exhaust pipe 41 becomes the target pipe temperature. As a result, the temperature of the exhaust pipe 41 during the vacuum drying process is maintained at the target pipe temperature.
After steps S1 and S2 are performed as described above, the substrate 9 having the upper surface 91 coated with the coating film 92 is loaded into the chamber 10 and stored in the internal space SP (step S3: loading step). Specifically, the lid portion 12 of the chamber 10 is raised by the chamber lifting mechanism 12a. Then, the substrate 9 is carried into the chamber 10 by a transfer robot (not shown) and placed on the plurality of substrate holding pins 21. When the loading of the substrate 9 is completed, the transfer robot retracts to the outside of the chamber 10, and the lid 12 of the chamber 10 is lowered by the chamber lifting mechanism 12a. As a result, the internal space SP becomes a sealed space.

  In the next step S4, the on-off valve 44 is opened and the butterfly valves 42, 43 are opened to a predetermined opening degree. Further, the exhaust pump 45 is operated, and the gas inside the chamber 10 is forcibly exhausted through the exhaust ports 111 and 112. As a result, the atmosphere in the internal space SP is discharged to the exhaust line via the exhaust ports 111 and 112, the butterfly valves 42 and 43, the exhaust pipe 41 and the on-off valve 44, and the internal space SP of the chamber 10 is decompressed. The solvent component contained in the coating film 92 applied to the surface of the substrate 9 is vaporized in accordance with the decompression of the internal space SP. Thereby, the pressure reduction process with respect to the coating film 92 on the board | substrate 9 is started.

  In the decompression process, since the rod heater has already been operated in step S1, the heating process for the substrate 9 is also started (step S4). That is, the substrate 9 is heated from the lower surface side by the rod heater in the internal space SP where the ambient temperature has increased. By this heat treatment, the temperature of the solvent component contained in the coating film 92 on the substrate 9 is raised to further promote the vaporization of the solvent component. Thus, the reduced pressure drying apparatus 1 improves the drying efficiency of the coating film 92 by performing the reduced pressure drying process using both the reduced pressure and heating of the internal space SP (drying process).

  In this way, the pressure reduction process and the drying process are performed in parallel while heating the exhaust pipe 41 to the target pipe temperature, and when the drying of the coating film 92 is completed, the exhaust pump 45 is stopped and an unshown open valve is opened. As a result, the internal space SP of the chamber 10 is restored to atmospheric pressure. Thereafter, the chamber elevating mechanism 12a raises the lid 12 of the chamber 10, and the hand of the transfer robot enters the chamber 10 to receive the substrate 9 on the substrate holding pin 21 and carry it out of the chamber 10 (step S5). : Unloading process). Thus, the reduced-pressure drying process for one substrate 9 is completed. The heating of the internal space SP by the substrate heating unit 30 and the heating of the exhaust pipe 41 by the pipe heating unit 50 are continuously performed.

  As described above, in the vacuum drying apparatus 1, the vacuum drying process is performed while heating the exhaust pipe 41. Therefore, the solvent component contained in the exhaust gas is liquefied and adheres to the exhaust pipe 41 during the vacuum drying process. Can be prevented. As a result, the vacuum drying process by the vacuum drying apparatus 1 can be performed in a short time. Further, each time the vacuum drying process is performed, the solvent component remaining in the exhaust pipe 41 can be suppressed, and the vacuum drying process can be performed stably. In particular, even when a plurality of substrates 9 are processed successively, each substrate 9 can be dried under reduced pressure with a fixed tact time.

  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 above embodiment, the entire exhaust pipe 41 is uniformly heated and adjusted to the target pipe temperature during the reduced-pressure drying process. However, the pipe temperature may be varied. This is because when the exhaust pipe 41 becomes longer, the temperature of the exhaust gas passing through each region differs between the region near the chamber 10 and the region away from the exhaust pipe 41. That is, as the distance from the chamber 10 increases, the temperature of the exhaust gas in the exhaust pipe 41 decreases, and a liquefaction phenomenon is likely to occur. Therefore, it is preferable to heat the exhaust pipe 41 so that the temperature of the exhaust pipe 41 increases as the distance from the chamber 10 increases.

  In the above embodiment, the present invention is applied to the vacuum drying apparatus 1 that vacuum-drys the coating film 92 formed by applying the polyamic acid solution to the upper surface 91 of the substrate 9. The range is not limited to this, and it is an apparatus for drying a coating film formed of a resist solution, an interlayer insulating material, a low dielectric material, a ferroelectric material, a wiring material, an organic metal material, a metal paste, etc. under reduced pressure. Is also applicable. The present invention can also be applied to a vacuum drying apparatus that vacuum-drys a coating film formed on the lower surface of the substrate 9 or on both surfaces of the substrate 9.

  As described above, the present invention has been described by exemplifying a specific embodiment. For example, the present invention provides a dew point of an exhaust gas containing a solvent component exhausted through the exhaust pipe by adjusting the temperature of the exhaust pipe, for example, by a pipe temperature control unit. You may comprise so that it may adjust to temperature higher than temperature. That is, in order to suppress the liquefaction of the solvent component to the exhaust pipe, it is preferable to employ such a configuration.

  Moreover, if the temperature of the exhaust pipe is adjusted to a temperature lower than that of the internal space by the pipe temperature control unit, it is possible to prevent the exhaust speed from being lowered, which is preferable.

  Furthermore, it is desirable that the pipe heating unit is configured to heat the exhaust pipe so that the temperature of the exhaust pipe becomes higher as the distance from the chamber increases, so that the liquefaction of the solvent component is effective even when the exhaust pipe becomes longer. Therefore, it can be prevented.

  The present invention can be applied to general vacuum drying techniques for drying a coating film formed on a substrate by the combined use of vacuum processing and heat treatment.

DESCRIPTION OF SYMBOLS 1 ... Low pressure drying apparatus 9 ... Board | substrate 10 ... Chamber 41 ... Exhaust piping 50 ... Pipe heating part 51 ... Pipe heater 60 ... Control part (pipe temperature control part)
91 ... Upper surface of substrate 92 ... Coating film SP ... Internal space of (chamber)

Claims (5)

The substrate is housed in the internal space of the chamber, and the internal space is decompressed and the internal space is heated by exhausting the atmosphere of the internal space through an exhaust pipe connected to the chamber. A vacuum drying apparatus for evaporating the solvent component contained in the coating film and drying the coating film,
A pipe heating unit for heating the exhaust pipe from the outer peripheral surface side of the exhaust pipe;
The reduced pressure drying apparatus , wherein the pipe heating unit heats the exhaust pipe so that the temperature of the exhaust pipe increases as the distance from the chamber increases . The vacuum drying apparatus according to claim 1,
A vacuum drying apparatus further comprising a pipe temperature control unit that adjusts the temperature of the exhaust pipe by controlling the pipe heating unit. The vacuum drying apparatus according to claim 2,
The said piping temperature control part is a reduced pressure drying apparatus which adjusts the temperature of the said exhaust piping to temperature higher than the dew point temperature of the exhaust gas containing the said solvent component exhausted via the said exhaust piping. The reduced-pressure drying apparatus according to claim 2 or 3,
The said piping temperature control part is a reduced pressure drying apparatus which adjusts the temperature of the said exhaust piping to the temperature lower than the said internal space. A storage step of storing the substrate on which the coating film is formed in the internal space of the chamber;
The solvent component contained in the coating film on the substrate is vaporized by exhausting the atmosphere of the internal space through an exhaust pipe connected to the chamber to depressurize the internal space and heating the internal space. Drying step of drying the coating film,
In parallel with the drying step, the method includes a pipe heating step for heating the exhaust pipe from the outer peripheral surface side of the exhaust pipe so that the temperature of the exhaust pipe increases as the distance from the chamber increases. Method.

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