JP2013164231A - Vacuum drying apparatus and vacuum drying method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vacuum drying apparatus that can reduce mixing of moisture to recover a solvent while decompression-drying a coating liquid on a substrate, and a vacuum drying method.SOLUTION: A vacuum drying apparatus 1 includes: a chamber 2 for accommodating a substrate W; an exhaust device 3 for exhausting a gas in the chamber 2; a recovery device 4 for cooling a gas to recover a liquid generated by cooling; and first piping 5 that connects the chamber 2 to the exhaust device 3 via the recovery device 4 on the way. The vacuum drying apparatus decompression-dries a coating liquid R applied on the substrate W by making the exhaust device 3 exhaust the gas in the chamber 2 through the first piping 5 to perform decompression. The solvent is recovered by liquefying the solvent evaporated from the coating liquid R through decompression drying to be cooled by the recovery device 4. Second piping 6 is further provided that connects the chamber 2 with the exhaust device 3 not by way of the recovery device 4 on the way.

Description

  The present invention relates to a vacuum drying apparatus and vacuum drying for drying a coating liquid by volatilizing a solvent in the coating liquid in a reduced pressure environment, and further liquefying and recovering the volatilized solvent on a substrate coated with the coating liquid. It is about the method.

  A flat panel display such as a liquid crystal display or a plasma display uses a substrate coated with a resist solution (referred to as a coated substrate). In the production process of the coated substrate, first, a coating film is formed by uniformly applying a resist solution onto the substrate by a coating device, and then the coating film is dried by a drying device such as a vacuum drying device.

  This vacuum drying apparatus dries the coating liquid on the coating substrate by reducing the pressure of the chamber while the substrate is accommodated in the chamber. Specifically, the air in the chamber is exhausted to the outside while the coated substrate is placed in the chamber, and the solvent in the coating solution on the coated substrate is volatilized when the chamber is in a reduced pressure environment. Then, the coating solution dries.

  Here, in Patent Document 1 described below, there is a description that a solvent liquefaction device is provided outside the chamber, and the solvent vapor generated in the chamber is liquefied by cooling in the solvent liquefaction device and recovered in a recovery tank. is there. By using this method for the exhaust mechanism of the vacuum drying apparatus, the recovered solvent can be reused for cleaning the nozzles and pipes of the coating apparatus, and the cost can be reduced. Further, it is possible to reduce the adhesion of the solvent to the exhaust equipment such as the vacuum pump of the exhaust mechanism, and to reduce the load on the exhaust equipment.

JP 2005-5469 A

  However, the solvent recovery method described in Patent Document 1 has a problem in that a high purity solvent may not be obtained because the recovered liquid contains moisture in addition to the solvent. Specifically, in addition to the solvent vapor generated in the chamber, the air in the chamber also flows into the solvent liquefier by exhaust, and when this air is cooled by the solvent liquefier, the water vapor contained in the air Is liquefied into water, and this water is mixed with the solvent and stored in the recovery tank. Therefore, when the solvent is a substance that is difficult to separate from water, there is a possibility that a high-purity solvent cannot be obtained by this recovery method.

  In addition, if the temperature in the solvent liquefier is set below the freezing point in order to increase the solvent recovery efficiency, the water vapor contained in the air may liquefy and freeze in the solvent liquefier, thereby improving the cooling efficiency. There was a risk that the piping would be lowered or the piping between the solvent liquefier and the recovery tank would be clogged.

  The present invention has been made in view of the above-described problems of the prior art, and is a vacuum drying capable of recovering a solvent by reducing moisture mixing while drying a coating liquid on a substrate under reduced pressure. An object is to provide an apparatus and a vacuum drying method.

  In order to solve the above-described problems, a vacuum drying apparatus of the present invention includes a chamber unit that accommodates a substrate, an exhaust device that exhausts gas in the chamber unit, and a recovery unit that cools the gas and collects a liquefied product generated by the cooling. A first pipe that is a pipe that connects the chamber section and the exhaust apparatus and passes through the recovery apparatus in the middle, and the gas inside the chamber section through the first pipe by the exhaust apparatus Is a reduced-pressure drying apparatus that evacuates and decompresses the coating liquid applied to the substrate under reduced pressure, and liquefies and recovers the solvent volatilized from the coating liquid by the reduced-pressure drying by cooling with the recovery apparatus, The chamber portion and the exhaust device are connected to each other, and a second pipe that is a pipe that does not pass through the recovery device is further provided on the way.

  According to the reduced-pressure drying apparatus, the second pipe, which is a pipe that does not pass through the collection apparatus, is further provided in the middle, so that the solvent is collected with less moisture mixing compared to the case where only the first pipe is used. It is possible. That is, by drying the coating liquid using the second pipe, the amount of water contained in the gas in the chamber portion flowing to the first pipe and the recovery device can be reduced. Further, since the moisture content in the collecting device is reduced, it is possible to prevent the collecting device from freezing.

  Moreover, it is good to have further the switching part which switches the piping which passes when the said exhaust apparatus exhausts the gas in the said chamber part between said 1st piping and said 2nd piping.

  By further including the switching unit in this way, it is possible to increase the amount of solvent recovered when the first pipe is used as compared with the case where the second pipe is also used. That is, when the gas inside the chamber part contains a lot of moisture, only the second pipe is used, and then the first pipe is used to perform decompression drying inside the chamber part. Since all the gas in the section can flow to the recovery device, the amount of solvent recovered can be increased.

  In order to solve the above problems, the reduced-pressure drying method of the present invention includes a chamber portion that accommodates a substrate, an exhaust device that exhausts gas, and a recovery device that cools the gas and collects the liquefied material generated by the cooling. A first pipe that is a pipe that connects the chamber part and the exhaust apparatus and passes through the recovery apparatus in the middle, and a pipe that connects the chamber part and the exhaust apparatus and does not pass through the recovery apparatus in the middle A second pipe that is, and by exhausting the gas inside the chamber part through the first pipe by the exhaust device and reducing the pressure, the coating liquid applied to the substrate is dried under reduced pressure, This is a vacuum drying method in which the solvent volatilized from the coating liquid is liquefied and recovered by cooling with the recovery device, and the gas inside the chamber part is exhausted via the second pipe and applied. And not recovered drying step of drying the, via the first pipe to exhaust the gas inside of the chamber section, and characterized in that it comprises a recovery drying step of drying the coating solution.

  By having the non-recovery drying step and the recovery drying step in this way, the amount of water contained in the gas in the chamber portion flowing to the first pipe and the recovery device is reduced compared to the case where only the recovery drying step is performed. Since the amount can be reduced, it is possible to prevent the freezing of the recovery device, and at the same time, it is possible to recover the solvent with less water mixing.

  In addition, after performing the non-recovery drying step, the piping through which the exhaust device exhausts the gas in the chamber portion is switched from the first piping to the second piping, and then the recovery drying step. It is good to do.

  By doing in this way, when performing a recovery drying process, it is possible to increase the recovery amount of a solvent compared with the case where a non-recovery drying process is also performed together. That is, when the gas inside the chamber part contains a lot of moisture, a non-recovery drying process is performed, and after the moisture is sufficiently reduced, the recovery drying process is performed by switching the piping, thereby reducing the moisture content. All of the solvent can be passed to the recovery device, so that the amount of recovered solvent can be increased.

  According to the reduced-pressure drying apparatus and the reduced-pressure drying method of the present invention, it is possible to recover the solvent while reducing the moisture content while drying the coating solution on the substrate under reduced pressure.

It is the schematic of the reduced pressure drying apparatus in one Embodiment of this invention, and is a side view. It is a graph which shows the saturated vapor pressure of a solvent and water. It is a graph showing the time-dependent change of the internal pressure of a reduced pressure drying apparatus, and the time-dependent change of the solvent amount in a chamber part, and a moisture content. It is an operation | movement flow of the vacuum drying method in one Embodiment of this invention. It is the schematic of the reduced pressure drying apparatus in other embodiment of this invention, and is a side view. It is an operation | movement flow of the vacuum drying method in other embodiment of this invention. It is the schematic of the reduced pressure drying apparatus in other embodiment of this invention, and is a side view.

  Embodiments according to the present invention will be described with reference to the drawings.

  FIG. 1 shows a side view of a vacuum drying apparatus according to an embodiment of the present invention. The vacuum drying apparatus 1 includes a chamber unit 2, an exhaust device 3, and a recovery device 4, and the exhaust device 3 exhausts the gas inside the chamber unit 2 to depressurize the substrate W contained in the chamber unit 2. The solvent is volatilized from the coating liquid R applied to the surface. In the following description, the evaporation of the solvent is called drying.

  In addition, there are two types of piping that connect the chamber unit 2 and the exhaust device 3, that is, a first piping 5 that passes through the recovery device 4 and a second piping 6 that does not pass through the recovery device 4. Are switched by the switching unit 7, and the coating solution R is dried under reduced pressure. Here, when the gas in the chamber portion 2 is exhausted via the first pipe 5, the gas is cooled by the recovery device 4, and the gas liquefied by this cooling is recovered in the recovery container 23 of the recovery device 4. Is done.

  The chamber unit 2 includes a chamber main body 11, a chamber lid unit 12, a placement unit 13, and an exhaust port 14.

  The chamber main body 11 and the chamber lid 12 can be brought into and out of contact with each other by driving and controlling a lifting mechanism (not shown) provided in the chamber lid 12, and the chamber lid 12 abuts on the chamber main body 11. A sealed space is formed inside the chamber portion 2. In a state where the substrate W coated with the coating liquid R such as a resist is accommodated in the sealed space, the gas in the sealed space is exhausted by the exhaust device 3 and the pressure is reduced, whereby the solvent is volatilized from the coating liquid R. Then, the coating solution R is dried. Further, when the chamber lid 12 is separated from the chamber main body 11, the substrate W can be carried into and out of the chamber 2 by a transfer robot (not shown).

  In this embodiment, the mounting unit 13 is a plurality of pins provided on the chamber body 11, and supports the substrate W when performing vacuum drying by having the tips of the mounting unit 13 abut the back surface of the substrate W. Thereby, the robot hand or the like can enter under the substrate W through the pins, and the substrate W can be easily carried in and out.

  Here, there is a considerable difference in temperature between the portion where the mounting portion 13 is in contact with the portion which is not in contact with the substrate W, and a difference is partially caused in the progress of drying of the coating liquid R. In order to prevent this, the end of the mounting portion 13 on the side in contact with the substrate W has a sharp shape, and by reducing the contact area with the substrate W, a temperature difference is unlikely to occur in the substrate W. It has become.

  The exhaust port 14 is an opening provided in the chamber main body 11, and the inside of the chamber portion 2 and the exhaust device 3 are connected through a pipe through the exhaust port 14.

  The exhaust device 3 is a vacuum pump, a blower or the like, and exhausts the gas inside the chamber portion 2 connected by piping. Here, two types of pipes for connecting the chamber portion 2 and the exhaust device 3 are provided: a first pipe 5 that passes through the recovery device 4 and a second pipe 6 that does not pass through the recovery device 4. . Moreover, the switching part 7 is provided between the chamber part 2 and the collection | recovery apparatus 4 of the 1st piping 5, and the 2nd piping, The piping which passes when exhausting the gas in the chamber part 2 is switched. be able to.

  In the present embodiment, the recovery device 4 includes a cooling container 21, a cooling coil 22, and a recovery container 23, cools the gas flowing into the cooling container 21 maintained at a low temperature by the cooling coil 22, and partially liquefies it. Let Then, the liquefied gas is recovered in the recovery container 23.

  The cooling container 21 is a substantially cylindrical container having a sealed space inside, two connection ports connected to the first pipe 5, an opening for drawing the cooling coil 22 into the inside, and the cooling coil 22 to the outside. For opening. Here, it is better that the two connection ports connected to the first pipe 5 are located at positions away from each other in the cooling container 21 so that the gas flowing into the cooling container 21 is efficiently cooled.

  Moreover, the cooling container 21 has a connection port for connecting to the recovery container 23 on the bottom surface, and the gas liquefied in the cooling container 21 flows into the recovery container 23 from here. Here, it is preferable that the bottom surface of the cooling container 21 has a mortar shape in which the height of the connection port with the recovery container 23 is the lowest so that the liquefied gas can easily flow into the recovery container 23.

  The cooling coil 22 is a pipe through which a refrigerant flows, and is passed through the inside of the cooling container 21, and is wound spirally along the inner wall of the cooling container 21. In the present embodiment, the temperature of the refrigerant is about −50 ° C., and the cooling coil 22 cooled by the refrigerant maintains the temperature inside the cooling container 21 at a low temperature. Further, since the cooling coil 22 is spirally wound inside the cooling container 21, the entire length of the cooling coil 22 passing through the cooling container 21 is increased, so that the temperature in the cooling container 21 can be maintained at a lower temperature.

  The recovery container 23 is a tank connected to the cooling container 21 through a connection port provided on the bottom surface of the cooling container 21, and the gas liquefied in the cooling container 21 flows into the recovery container 23 and is stored.

  Further, in the present embodiment, a valve 24 is provided in a pipe between the cooling container 21 and the recovery container 23, a pipe is provided on the bottom surface of the recovery container 23, and a valve 25 is also provided in the pipe. Yes. When the solvent is recovered by drying the coating liquid R under reduced pressure, the valve 24 is open and the valve 25 is closed, and the solvent is stored in the recovery container 23. Further, when the stored solvent is used for reuse, the valve 24 is closed and the valve 25 is opened, and the solvent is discharged to a transfer container (not shown).

  The switching unit 7 includes a valve 31 and a valve 32. The valve 31 is provided between the chamber unit 2 of the first pipe 5 and the recovery device 4, and the valve 32 is provided in the second pipe. Here, the exhaust in the state where the valve 31 is in the open state and the valve 32 is in the closed state is controlled by a control device (not shown), so that the gas in the chamber portion 2 is exhausted only through the first pipe 5. Then, the exhaust in the state where the valve 31 is closed and the valve 32 is opened causes the gas in the chamber portion 2 to be exhausted only through the second pipe 6. In other words, the switching unit 7 can switch the piping through which the gas in the chamber unit 2 is exhausted.

  Next, a vacuum drying method using the vacuum drying apparatus 1 having the above configuration will be described.

  FIG. 2 is a graph showing the saturated vapor pressure of the solvent contained in the coating liquid R normally used by the inventor, along with the graph of the saturated vapor pressure of water.

  FIG. 2 shows the saturated vapor pressures of five types of solvents and water, but all solvents show a saturated vapor pressure lower than that of water at any temperature. Is considered to have a saturated vapor pressure lower than that of water.

  Here, when the saturated vapor pressure at 20 ° C. is taken as an example, the saturated vapor pressure of water is about 2500 Pa, whereas the saturated vapor pressure of the solvent closest to the saturated vapor pressure of water is about 500 Pa. .

  Assuming that the chamber part 2 containing the substrate W coated with the coating solution R containing the solvent in a liquid state is depressurized from the atmospheric pressure with the chamber temperature set to 20 ° C., first, When the internal pressure reaches about 2500 Pa, the boiling point of water becomes 20 ° C., and even if liquid water exists in the chamber portion 2, it evaporates here. At this time, since the solvent has not yet reached the boiling point, the amount of volatilization is small, and most of the solvent exists in the coating liquid R as a liquid.

  When the internal pressure of the chamber part 2 is further reduced from about 2500 Pa, the moisture in the chamber part 2 decreases as the internal pressure of the chamber part 2 decreases, but the solvent is mostly liquid until the internal pressure reaches about 500 Pa. It remains in the chamber part 2 as it is. And when the internal pressure of the chamber part 2 reaches about 500 Pa, the boiling point of a solvent will be 20 degreeC and volatilization of a solvent will activate.

  FIG. 3 shows the change over time in the internal pressure of the chamber part 2 when the coating liquid R containing a solvent having a lower saturated vapor pressure than water is dried under reduced pressure using the reduced pressure drying apparatus 1, and the amount of solvent in the chamber part 2. It is a graph showing a time-dependent change of a moisture content.

  FIG. 3A shows the change over time in the internal pressure of the chamber portion 2. When drying under reduced pressure is started after the substrate W coated with the coating liquid R is placed inside the chamber part 2, the internal pressure of the chamber part 2 continues to decrease smoothly for a while, but when the internal pressure reaches a certain value. (The state of time t1 and pressure P1 shown in FIG. 3), the pace of pressure decrease suddenly becomes gentle. This is because the volatilization of the solvent in the coating liquid R becomes active from the time when the internal pressure of the chamber 2 part becomes P1, and the volatilization of the solvent increases the pressure while the inside of the chamber part 2 is depressurized by the exhaust. This is because the amount of pressure decrease in the chamber portion 2 is reduced as a result.

  That is, the pressure P1 is the saturated vapor pressure of the solvent, and the time t1 is the time when the internal pressure of the chamber unit 2 reaches the saturated vapor pressure of the solvent.

  Then, when the volatilization of the solvent proceeds and almost all of the solvent in the coating liquid R disappears, the pace of the decrease in the internal pressure of the chamber part 2 behaves again.

  FIG. 3B shows the change over time in the amount of solvent. As described above, the amount of the solvent that volatilizes from the coating solution R is small until the internal pressure of the chamber part 2 reaches the saturated vapor pressure P1 of the solvent, and the solvent is volatilized actively from the time when the internal pressure reaches P1 at time t1. However, the amount of solvent decreases rapidly.

  FIG.3 (c) shows the time-dependent change of a moisture content. Normally, moisture does not exist as a liquid in the chamber part 2 but only exists as water vapor in the air. Until the time t1 is reached, most of the gas present in the chamber part 2 is air that was in the chamber part 2 at the start of vacuum drying, so the amount of water is almost proportional to the decrease in the internal pressure of the chamber part 2. Also decreases. Here, in the case where the temperature is 20 ° C. as in the previous example, the atmospheric pressure is about 100,000 Pa, whereas the saturated vapor pressure of water is about 2500 Pa. When the water reaches the saturated vapor pressure of water, the amount of water present in the chamber portion 2 is about 3% at the start of drying under reduced pressure. Therefore, when the internal pressure of the chamber part 2 existing before the time t1 becomes the saturated vapor pressure of water (pressure P0 shown in FIG. 3), the amount of water in the chamber part 2 is sufficiently small. Think.

  As described above, when a solvent having a saturated vapor pressure lower than that of water is volatilized by depressurization, most of the solvent remains in the chamber unit 2 until the volatilization of the solvent becomes active. It decreases steadily as the internal pressure decreases.

  Therefore, the exhaust via the first pipe 5 may be started around the time when the volatilization of the solvent starts to be active, and the gas may pass through the recovery device 4. By doing so, it is possible to recover a large amount of solvent, and almost no moisture is mixed in, so that freezing of the recovery device can be prevented and at the same time a high-purity solvent can be recovered. Further, in this case, exhaust through the second pipe 6 is performed until exhaust through the first pipe 5 is performed.

  In the present invention, the process of drying under reduced pressure through the recovery device 4 by exhausting through the first pipe 5 is called the recovery drying process, and the recovery apparatus 4 is exhausted through the second pipe 6. The process of drying under reduced pressure without passing through is called a non-recovery drying process.

  Here, a specific guideline for starting the recovery drying process is set, for example, when the internal pressure of the chamber portion 2 reaches the saturated vapor pressure P0 of water or when the saturated vapor pressure P1 of the solvent is reached. Good. By doing so, there is almost no moisture mixing as described above, and many solvents can be recovered, and P0 and P1 are unique numerical values for water and solvent, so at the timing when these numerical values are obtained. Control is facilitated by the control. In addition, when the recovery drying process starts when the internal pressure of the chamber part 2 reaches P1, the recovery amount of the solvent is slightly reduced compared with the case where the recovery drying process starts when the internal pressure reaches P0. Reduced recovery is possible.

  As a method for confirming these timings during the actual reduced pressure drying process, there is a method in which a pressure gauge (not shown) is further provided in the chamber unit 2 and the pressure gauge measures the internal pressure of the chamber unit 2. And it is good to start a collection | recovery drying process when the measured value turns into P0 or P1. Of course, a value slightly around P0 and P1 may be used as a guide.

  If the saturated vapor pressure P1 of the solvent is unknown, the recovery / drying process is performed at the timing when the decreasing pace of the internal pressure of the chamber portion 2 continues to be measured with a pressure gauge and the decreasing pace suddenly relaxes (ie, time t1). May start.

  Further, when the times t0 and t1 when the internal pressure of the chamber part 2 reaches P0 or P1 are empirically known, the recovery drying process is performed at a timing when a predetermined time has elapsed from the start of the vacuum drying without using a pressure gauge. May start.

  Next, FIG. 4 shows an operation flow of a vacuum drying method using the vacuum drying apparatus 1. Here, it is assumed that the exhaust device 3 is always operating, and the timing for starting the recovery drying process is set when the internal pressure of the chamber portion 2 reaches the saturated vapor pressure P1 of the solvent.

  First, the substrate W coated with the coating liquid R is carried into the chamber unit 2 (step S1). Specifically, a transfer robot or the like (not shown) places the substrate W on the placement portion 13 of the chamber portion 2 in which the chamber body 11 and the chamber lid portion 12 are separated from each other, and then the chamber lid portion 12. Descends and comes into contact with the chamber body 11 to form a sealed space in the chamber portion 2. At this time, it is assumed that both the valve 31 and the valve 32 of the switching unit 7 are in the closed state, and the gas flow from the chamber unit 2 to the exhaust device 3 is blocked.

  Next, the valve 32 of the switching unit 7 is opened (step S2), and the coating liquid R is dried under reduced pressure (non-recovery drying step) via the second pipe 6 (step S3).

  This non-recovery drying process continues until the internal pressure of the chamber section 2 reaches P1 (step S4), and when the internal pressure of the chamber section 2 reaches P1, the valve 32 of the switching section 7 is closed (step S5) and continues. Thus, the valve 31 of the switching unit 7 is opened (step S6), and the vacuum drying (non-recovery drying process) via the second pipe 6 is switched to the vacuum drying (recovery drying process) via the first pipe 5. And the volatile solvent which passed the collection | recovery apparatus 4 in the middle of the 1st piping 5 is cooled, liquefied, and collect | recovered (step S7).

  This recovery drying process continues until most of the solvent in the coating solution R is volatilized and vacuum drying is completed (step S8). When vacuum drying is completed, the valve 31 of the switching unit 7 is closed and the chamber portion is closed. The gas flow from 2 to the exhaust device 3 is blocked (step S9).

  Finally, after the inside of the chamber unit 2 is opened to the atmosphere, the chamber lid unit 12 is raised and separated from the chamber body 11, and the substrate W is unloaded from the mounting unit 13 by a transfer robot (not shown) (step S10). ).

  Next, another embodiment of the present invention is shown in FIG. In FIG. 1, only one exhaust device is provided, and the piping branches into the first piping 5 and the second piping 6 between the chamber portion 2 and the exhaust device 3, but as shown in FIG. The 1st piping 5 and the 2nd piping 6 may be provided independently, and the exhaust apparatus 3 may be provided in each piping. Here, in the previous embodiment, the first pipe 5 and the second pipe 6 are switched and used by the switching unit 7, and the recovery drying process is performed after the non-recovery drying process, and the non-recovery drying process and the recovery drying process. However, the non-recovery drying process is continued until the vacuum drying is completed, and after the start of the recovery drying process, the recovery drying process is not performed. The recovery drying process may be performed together.

  FIG. 6 shows an operation flow of the reduced pressure drying method when the non-recovery drying step is continued together with the recovery drying step by the reduced pressure drying apparatus 1 shown in FIG. Here, it is assumed that the exhaust device 3 is always operating, and the timing for starting the recovery drying process is set when the internal pressure of the chamber portion 2 reaches the saturated vapor pressure P1 of the solvent.

  First, the substrate W coated with the coating liquid R is carried into the chamber unit 2 (step S21). At this time, the valve 41 provided in the first pipe 5 and the valve 42 provided in the second pipe are both closed, and the gas flow from the chamber portion 2 to the exhaust device 3 is blocked. It shall be.

  Next, the valve 42 is opened (step S22), and the coating solution R is dried under reduced pressure (non-recovery drying step) via the second pipe 6 (step S23).

  This non-recovery drying process is performed alone until the internal pressure of the chamber part 2 reaches P1 (step S24). When the internal pressure of the chamber part 2 reaches P1, the valve 41 is opened (step S25), The reduced-pressure drying (non-recovery drying step) via the pipe 6 and the reduced-pressure drying (recovery drying step) via the first pipe 5 are performed together. And the volatile solvent which passed the collection | recovery apparatus 4 in the middle of the 1st piping 5 is cooled, liquefied, and collect | recovered (step S26).

  The non-recovery drying process and the recovery drying process continue until most of the solvent in the coating liquid R is volatilized and vacuum drying is completed (step S27). When vacuum drying is completed, the valve 41 is closed (step S28). Subsequently, the valve 42 is closed (step S29), and the gas flow from the chamber portion 2 to the exhaust device 3 is blocked.

  Finally, the substrate W is unloaded from the chamber unit 2 (step S30).

  According to such a reduced-pressure drying method, since the reduced-pressure drying is performed via both the first pipe 5 and the second pipe 6 after the internal pressure of the chamber unit 2 reaches P1, the flow to the recovery device 4, Although the amount of solvent recovered is small, the drying tact can be accelerated.

  Next, still another embodiment of the present invention is shown in FIG. When the coating liquid R contains a plurality of types of solvents such as a solvent a and a solvent b, for example, each solvent can be recovered separately using the difference in saturated vapor pressure of these solvents. .

  Specifically, the same number of recovery containers 23 as the number of types of solvents (recovery containers 23a and 23b shown in FIG. 7) are provided, and a valve 24 (see FIG. 7) is connected to a pipe connecting each recovery container and the cooling container 21. 7 is provided in the reduced pressure drying apparatus 1. The valve 24a and the valve 24b) shown in FIG. Here, it is assumed that the saturated vapor pressure of the solvent a is P1a, the saturated vapor pressure of the solvent b is P1b, and P1a> P1b.

  When decompressing the chamber 2 by the decompression drying apparatus 1, the decompression is started via the second pipe 6 at the start of decompression to reduce the moisture mixed into the recovery container 21, and then the chamber In the vicinity of the time when the internal pressure of P2 becomes P1a, the pressure is switched to the pressure reduction via the first pipe 5, and at that time, the valve 24a is opened and the other valves 24 (valves 24b) are closed. In the vicinity of the pressure P1a, the volatilization of the solvent a becomes active, but the solvent b has not yet reached the saturated vapor pressure, so the volatilization amount is small. Accordingly, by keeping the valve 24a open at this time, the high-purity solvent a is recovered in the recovery container 23a.

  When the pressure is further reduced and the internal pressure of the chamber 2 becomes near P1b, the valve 24a is closed and the valve 24b is opened, so that the recovered solvent flows into the recovery container 24b. At this time, the solvent a is almost completely volatilized, and the volatilization of the solvent b becomes active, so that the high-purity solvent b is recovered in the recovery container 23b. Then, by opening the valve 25a and the valve 25b, the solvent a and the solvent b are discharged from the recovery container 23a and the recovery container 23b to a transfer container (not shown).

  Even if there are three or more types of solvent, it is possible to recover each of the high-purity solvents in each recovery container 23 by switching the valve 24 as described above.

  Further, when the solvent a and the solvent b as described above are contained in the coating liquid R, the pressure reduction via the second pipe 6 is continued until the internal pressure of the chamber portion 2 reaches P1b, and at that time, the first pipe 5 It is of course possible to select and recover only the high-purity solvent b (although the solvent a is not recovered) by switching to the reduced pressure via the.

  With the above-described reduced-pressure drying apparatus and reduced-pressure drying method, it is possible to recover the solvent while reducing the moisture content while drying the coating solution on the substrate under reduced pressure.

DESCRIPTION OF SYMBOLS 1 Vacuum drying apparatus 2 Chamber part 3 Exhaust apparatus 4 Recovery apparatus 5 1st piping 6 2nd piping 7 Switching part 11 Chamber main body 12 Chamber lid part 13 Mounting part 14 Exhaust port 21 Cooling container 22 Cooling coil 23 Recovery container 23a Recovery container 23b Collection container 24 Valve 24a Valve 24b Valve 25 Valve 25a Valve 25b Valve 31 Valve 32 Valve 41 Valve 42 Valve R Coating liquid W Substrate

Claims (4)

A chamber for accommodating the substrate;
An exhaust device for exhausting the gas in the chamber portion;
A recovery device that cools the gas and recovers the liquefied material generated by the cooling;
A first pipe which is a pipe connecting the chamber unit and the exhaust device and passing through the recovery device in the middle;
With
The exhaust device exhausts the gas inside the chamber portion through the first pipe and depressurizes, thereby drying the coating solution applied to the substrate under reduced pressure, and recovering the solvent volatilized from the coating solution by drying under reduced pressure. It is a vacuum drying device that is liquefied and recovered by cooling with
A reduced-pressure drying apparatus, further comprising a second pipe that is a pipe that connects the chamber portion and the exhaust device and does not pass through the recovery device.   2. The switch according to claim 1, further comprising a switching unit that switches a pipe through which the exhaust device exhausts the gas in the chamber section between the first pipe and the second pipe. Vacuum drying equipment. A chamber for accommodating the substrate;
An exhaust device for exhausting gas;
A recovery device that cools the gas and recovers the liquefied material generated by the cooling;
A first pipe which is a pipe connecting the chamber unit and the exhaust device and passing through the recovery device in the middle;
A second pipe that is a pipe that connects the chamber portion and the exhaust device and does not pass through the recovery device in the middle;
With
The exhaust device exhausts the gas inside the chamber portion through the first pipe and depressurizes, thereby drying the coating solution applied to the substrate under reduced pressure, and recovering the solvent volatilized from the coating solution by drying under reduced pressure. It is a vacuum drying method to recover by liquefying by cooling with,
A non-recovery drying step of exhausting the gas inside the chamber portion via the second pipe and drying the coating solution;
A recovery drying step of exhausting the gas inside the chamber part via the first pipe and drying the coating solution;
A method for drying under reduced pressure, comprising:   After performing the non-recovery drying step, the piping through which the exhaust device exhausts the gas in the chamber portion is switched from the first piping to the second piping, and then the recovery drying step is performed. The vacuum drying method according to claim 3, wherein:

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