Drying apparatus and method for checking drying status

Abstract

To check the dryness of an object.SOLUTION: A drying device according to an embodiment includes a drying tank that holds an object to be dried inside, a pressure reducing device that reduces the pressure inside the drying tank, and a control unit that controls the pressure reducing device to perform a drying process in which the pressure inside the drying tank is reduced to evaporate and remove moisture. After the drying process, the control unit performs an additional pressure reducing process for a predetermined period of time in which the pressure inside the drying tank is lower than the pressure during the drying process, and determines the drying state of the object on the basis of the pressure inside the drying tank reached after the additional pressure reducing process.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] Embodiments of the present invention relate to a drying device and a method for confirming a drying state.

Background Art

[0002] Conventionally, in the manufacture of semiconductor wafers, wafer storage containers such as FOUP (Front Opening Unified Pod) and FOSB (Front Opening Shipping Box) for storing (accommodating) semiconductor wafers have been used. Since the inside of the container may be contaminated when storing semiconductor wafers, etc., cleaning treatment is periodically performed. For example, as a device for performing the cleaning treatment of the wafer storage container, there is known a device having a cleaning tank and a drying tank, in which ultrasonic cleaning and high-pressure shower cleaning are alternately repeated several times in the cleaning tank, and then hot air heating and vacuum drying are repeated several times in the drying tank to perform drying.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] As described above, although the wafer storage container is periodically subjected to cleaning treatment, if the semiconductor wafer is stored with insufficient drying, the semiconductor wafer is contaminated, which causes product defects. Therefore, it is important to sufficiently dry the wafer storage container. However, the above-described drying process is performed under pre-set conditions without checking the drying state, so even if the drying is insufficient, it cannot be noticed. Also, in order to sufficiently dry the wafer storage container, it may be considered to extend the drying time, but this will result in performing the drying process for an unnecessary amount of time, which is not efficient.

[0005] The present invention was made to solve the above-mentioned problems, and its purpose is to provide a drying apparatus and a drying state confirmation method that can confirm the drying state of an object. [Means for solving the problem]

[0006] To solve the above-mentioned problems and achieve the objective, a drying apparatus according to one aspect of the present invention comprises a drying tank for holding an object to be dried inside, a vacuum device for reducing the pressure inside the drying tank, and a device for controlling the vacuum device to reduce the pressure inside the drying tank. At a pressure lower than atmospheric pressure The system includes a control unit that performs a drying process to remove moisture by reducing the pressure, and after the drying process, the control unit performs an additional pressure reduction process for a predetermined time such that the pressure inside the drying tank becomes lower than the pressure at the time of the drying process, and the pressure inside the drying tank reached after the additional pressure reduction process If the threshold is reached, the drying state of the object is determined to be sufficient, and if the threshold is not reached, The dry state of the aforementioned object Insufficient and Determine. [Effects of the Invention]

[0007] According to one aspect of the present invention, the dry state of an object can be confirmed. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a plan view showing an example of a schematic configuration of a wafer storage container cleaning apparatus according to the first embodiment. [Figure 2] Figure 2 is a side view of the inside of the vacuum chamber according to the first embodiment. [Figure 3] Figure 3 is a diagram illustrating an example of processing by the control unit according to the first embodiment. [Figure 4] Figure 4 is a diagram illustrating the pressure range according to the first embodiment. [Figure 5] Figure 5 is a flowchart showing the processing procedure by the control unit according to the first embodiment. [Modes for carrying out the invention]

[0009] The embodiments of the drying apparatus and drying state confirmation method disclosed herein will be described in detail below with reference to the attached drawings. However, the drying apparatus and drying state confirmation method disclosed herein are not limited to the embodiments described below. Furthermore, each embodiment and each modification can be combined as appropriate without contradiction. In the following embodiments, a wafer storage container cleaning apparatus will be used as an example of the drying apparatus.

[0010] (First embodiment) Figure 1 is a plan view showing an example of the schematic configuration of a wafer storage container cleaning apparatus 1 according to the first embodiment. The wafer storage container cleaning apparatus 1 is installed, for example, in a factory that manufactures semiconductor wafers, and cleans wafer storage containers. As shown in Figure 1, the wafer storage container cleaning apparatus 1 includes a load port 2, a robot 3, a disassembly / connection stage 4, a cleaning tank 5, a vacuum tank 6, an unload port 7, and a control unit 8. Note that the vacuum tank 6 is an example of a drying tank. Also, the control unit 8 is an example of a control unit.

[0011] The robot 3, disassembly / combination stage 4, cleaning tank 5, vacuum tank 6, and control unit 8 are located inside the casing 1a of the wafer storage container cleaning apparatus 1. On the other hand, the load port 2 and unload port 7 are located across both the inside and outside of the casing 1a of the wafer storage container cleaning apparatus 1.

[0012] The load port 2 loads the wafer storage container 20 to be cleaned, which is placed on the external part of the casing 1a of the load port 2, into the interior of the casing 1a. The wafer storage container 20 is, for example, an FOUP or FOSB, and comprises a container body (shell) 20a and a door (lid) 20b. The container body 20a has an opening and a storage space for storing semiconductor wafers. The storage space is located inside the opening and communicates with the opening. The door 20b can be detached from / connected to the container body 20a, and when connected to the container body 20a, it is attached in a state that allows it to be opened and closed relative to the opening. The container body 20a is also provided with a flange 20c. The flange 20c is the part that is gripped (held) when the wafer storage container 20 is transported by an OHT (Overhead Hoist Transport) or a robot 3, etc.

[0013] For example, a wafer storage container 20, which has been transported with its flange 20c gripped by the OHT, is placed on the outer part of the casing 1a of the load port 2. For example, as shown in Figure 1, the wafer storage container 20 is placed on the load port 2 such that its door 20b faces the casing 1a. When the wafer storage container 20 is placed on the load port 2 in this way, the shutter 2a provided at the opening 1b of the casing 1a rises. This makes it possible to load the wafer storage container 20 into the casing 1a from the opening 1b. In other words, the wafer storage container 20 becomes ready to be loaded into the wafer storage container cleaning device 1. Then, the wafer storage container 20 is slid in the direction of arrow 2b by the sliding device of the load port 2. This loads the wafer storage container 20 into the casing 1a.

[0014] The sliding mechanism will now be described. For example, a pin provided in the sliding mechanism is inserted into a hole in the bottom (mounting surface) of the wafer storage container 20, thereby fixing the mounting surface of the wafer storage container 20 to the sliding mechanism. In this state, the wafer storage container 20 slides along with the sliding mechanism as it slides in the direction of arrow 2b. As a result, the wafer storage container 20 is placed on a predetermined part inside the casing 1a of the load port 2. Once the wafer storage container 20 is loaded into the casing 1a in this way, the shutter 2a descends, closing the opening 1b of the casing 1a. The sliding mechanism, along with the pin, descends to a position lower than the lower end of the shutter 2a (the mounting surface of the wafer storage container 20) and returns to its original position outside the casing 1a.

[0015] Robot 3 transports the wafer storage container 20 to various parts while gripping the flange 20c of the wafer storage container 20. Robot 3 is equipped with a robot arm 3a and a robot hand 3b. With the flange 20c gripped by the robot hand 3b, Robot 3 transports the wafer storage container 20 to various parts by extending and retracting or rotating the robot arm 3a.

[0016] The disassembly / connection stage 4 disassembles the wafer storage container 20 into a container body 20a and a door 20b, and connects the container body 20a and the door 20b. A latch key 4a is provided on the disassembly / connection stage 4. When this latch key 4a is inserted into a keyhole formed in the door 20b of the wafer storage container 20 and rotated, the wafer storage container 20 is disassembled (separated) into a container body 20a and a door 20b, or the container body 20a and the door 20b are connected. For example, the wafer storage container 20, which has been brought into the casing 1a, is transported to the disassembly / connection stage 4 by a robot 3. In this case, the disassembly / connection stage 4 disassembles the wafer storage container 20 into a container body 20a and a door 20b. Disassembly can be rephrased as unlocking, and connection can be rephrased as locking.

[0017] The cleaning tank 5 is a tank for cleaning the wafer storage container 20. For example, in the cleaning tank 5, the container body 20a and the door 20b are separately transported by the robot 3. Then, the cleaning tank 5 performs a cleaning process on the wafer storage container 20 while holding the container body 20a and the door 20b separately. For example, the cleaning tank 5 is composed of a cleaning tank body having an opening on the upper surface and a lid portion capable of opening and closing the opening of the cleaning tank body. The cleaning tank 5 holds the door 20b on the lid portion of the cleaning tank 5 and the container body 20a in the cleaning tank body of the cleaning tank 5, and rotates them by a rotation mechanism (not shown), and discharges a cleaning liquid (for example, pure water) from a cleaning liquid nozzle to each of the container body 20a and the door 20b, thereby cleaning the wafer storage container 20. Inside the cleaning tank 5, it is preferable that the opening of the container body 20a is arranged downward in consideration of the discharge property of the cleaning liquid.

[0018] When the cleaning of the wafer storage container 20 in the cleaning tank 5 is completed, the container body 20a and the door 20b are subsequently rotated in the cleaning tank 5, and dry air is blown onto them for drying. The drying in the cleaning tank 5 here is a process (temporary drying) for generally drying the cleaning liquid adhering to the wafer storage container 20. When the temporary drying of the wafer storage container 20 in the cleaning tank 5 is completed, the robot 3 separately transports the container body 20a and the door 20b in the cleaning tank 5 to the vacuum tank 6.

[0019] The vacuum tank 6 is a tank for vacuum-drying (final drying) the wafer storage container 20. For example, the vacuum tank 6 includes a holding portion for holding the container body 20a and the door 20b transported inside, a heater, and a decompression device capable of evacuating the inside of the vacuum tank 6. Here, the wafer storage container cleaning device 1 according to the present embodiment is configured with the vacuum tank 6 and the control unit 8 so that the drying state of the wafer storage container 20 vacuum-dried by the vacuum tank 6 can be confirmed. Details thereof will be described later.

[0020] When the vacuum drying of the wafer storage container 20 is completed in the vacuum chamber 6, the robot 3 transfers the container body 20a and the door 20b in the vacuum chamber 6 to the disassembly / connection stage 4 separately. Then, the disassembly / connection stage 4 connects the container body 20a and the door 20b.

[0021] The unload port 7 unloads the washed and vacuum-dried wafer storage container 20 placed by the robot 3 inside the casing 1a of the unload port 7 to the outside of the casing 1a.

[0022] For example, after vacuum drying, the wafer storage container 20 in which the container body 20a and the door 20b are connected at the disassembly / connection stage 4 is transferred and placed by the robot 3 inside the casing 1a of the unload port 7. When the wafer storage container 20 is placed on the unload port 7 in this way, the shutter 7a provided at the opening 1c of the casing 1a rises. As a result, the wafer storage container 20 can be unloaded from the opening 1c to the outside of the casing 1a. That is, the wafer storage container 20 can be unloaded to the outside of the wafer storage container cleaning device 1. Then, the wafer storage container 20 is slid in the direction of arrow 7b by the slide device of the unload port 7 (which has the same mechanism as the slide device of the load port 2), and the wafer storage container 20 is unloaded to the outside of the casing 1a. When the wafer storage container 20 is unloaded to the outside of the casing 1a in this way, the shutter 7a descends and the opening 1c of the casing 1a is closed.

[0023] The control unit 8 controls the operation of the entire wafer storage container cleaning device 1. For example, the control unit 8 operates the load port 2, the robot 3, the disassembly / connection stage 4, the cleaning tank 5, the vacuum chamber 6, and the unload port 7 by controlling the load port 2, the robot 3, the disassembly / connection stage 4, the cleaning tank 5, the vacuum chamber 6, and the unload port 7 as described above.

[0024] For example, the control unit 8 includes a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), HDD (Hard Disk Drive), and a communication interface. These are connected via an internal bus.

[0025] The CPU uses RAM as a temporary storage area for data used in various processes while executing them. The processes executed by the CPU will be described later. ROM and HDD store programs for executing various processes, as well as various databases and tables used when executing those processes.

[0026] The communication interface is an interface for communicating with the various parts of the wafer storage container cleaning apparatus 1 as described above, as well as for communicating with external devices connected to the wafer storage container cleaning apparatus 1 via a network. For example, the communication interface is a network interface card.

[0027] Next, the processing performed by the vacuum chamber 6 and the control unit 8 will be described. Figure 2 is a side view of the inside of the vacuum chamber 6 according to the first embodiment. Figure 2 is a schematic diagram of the vacuum chamber 6, showing the opening of the vacuum chamber body 6a closed by the opening / closing lid 6b.

[0028] As shown in Figure 2, the vacuum chamber 6 comprises a vacuum chamber body 6a, an opening / closing lid 6b, a heater 6c, and a pressure sensor 6d, and holds the object to be dried (wafer storage container 20) inside. The vacuum chamber 6 also includes a first pipe 6e, a first valve 6f, a second pipe 6g, a second valve 6h, a pipe 6i, and a pressure reducing device 6j on the vacuum chamber body 6a.

[0029] The vacuum chamber body 6a has an opening at the top and a drying space on which the container body 20a is placed. Specifically, the internal space of the vacuum chamber body 6a is a region that includes the opening and the drying space. The opening / closing lid 6b is provided above the vacuum chamber body 6a. Specifically, it is provided so as to be openable and closable with respect to the opening of the vacuum chamber body 6a. The opening / closing lid 6b opens and closes the opening of the vacuum chamber body 6a by the operation of, for example, an air cylinder.

[0030] The interior (drying space) of the vacuum chamber body 6a is located inside the opening and communicates with the opening. With the opening / closing lid 6b open to the opening, the robot 3 carries the container body 20a and door 20b into the drying space through the opening. The heater 6c, under the control of the control unit 8, releases heat to warm the interior of the vacuum chamber body 6a. The pressure sensor 6d measures the pressure inside the vacuum chamber body 6a. The arrangement of the container body 20a and door 20b inside the vacuum chamber body 6a is not limited to that shown in the diagram, and any arrangement is acceptable. The number of heaters 6c is not limited to that shown in the diagram, and two or more heaters 6c may be provided. The positions of the heaters 6c and pressure sensor 6d are not limited to those shown in the diagram, and they can be installed in any position.

[0031] The vacuum chamber body 6a is provided with two exhaust ports for creating a vacuum in the drying space, and a first pipe 6e and a second pipe 6g are connected to each exhaust port, respectively. The first pipe 6e is connected to pipe 6i via a first valve 6f, and the second pipe 6g is connected to pipe 6i via a second valve 6h. Pipe 6i is connected to a pressure reducing device 6j. Here, the first pipe 6e has a smaller conductance compared to the second pipe 6g. For example, the conductance of the first pipe 6e is adjusted by providing an orifice or the like inside the pipe.

[0032] The depressurization device 6j reduces the pressure inside the vacuum chamber 6. Specifically, the depressurization device 6j reduces the pressure inside the vacuum chamber body 6a by discharging the gas inside the vacuum chamber body 6a to the outside. For example, the depressurization device 6j can be a dry pump, a mechanical booster pump, a rotary pump, etc. By introducing gas into the vacuum chamber 6 from a gas inlet (not shown), the pressure inside the vacuum chamber 6 can be reduced to approximately atmospheric pressure.

[0033] In the vacuum chamber 6 according to this embodiment, a drying process is performed to dry the wafer storage container 20 by vacuum drying, and an additional depressurization process is performed to determine the drying state of the wafer storage container 20. Specifically, the control unit 8 controls the depressurization device 6j to reduce the pressure inside the vacuum chamber 6 and perform a drying process to evaporate and remove moisture. After the drying process, the control unit 8 performs an additional depressurization process for a predetermined time until the pressure inside the vacuum chamber 6 is lower than the pressure during the drying process, and determines the drying state of the object based on the pressure inside the vacuum chamber 6 reached after the predetermined time has elapsed.

[0034] (Drying treatment) The control unit 8 executes the drying process by controlling the heater 6c, the first valve 6f, the second valve 6h, and the pressure reducing device 6j, after the container body 20a and the door 20b have been brought into the vacuum chamber body 6a and the opening of the vacuum chamber body 6a has been closed by the opening / closing lid 6b. Specifically, the control unit 8 executes the drying process of the container body 20a and the door 20b by opening the first valve 6f and closing the second valve 6h, and then driving the pressure reducing device 6j. In other words, the control unit 8 vacuum-dries the container body 20a and the door 20b by heating the heater 6c while simultaneously evacuating the inside of the vacuum chamber 6 with the pressure reducing device 6j via the first piping 6e, the first valve 6f, and piping 6i.

[0035] Here, the pressure inside the vacuum chamber body 6a during the drying process is reduced to, for example, less than 2000 Pa. By reducing the pressure inside the vacuum chamber body 6a to less than 2000 Pa, water droplets adhering to the container body 20a or door 20b begin to evaporate at temperatures above 20°C. However, lowering the pressure inside the vacuum chamber body 6a also lowers the temperature at which water droplets begin to evaporate. Furthermore, since water droplets absorb heat from themselves through evaporative cooling when they evaporate, if the pressure inside the vacuum chamber body 6a is lowered too much, the water droplets will freeze, resulting in insufficient drying. Therefore, the pressure inside the vacuum chamber body 6a during the drying process is set to remain within a pressure range where water droplets do not freeze. That is, the conductance in the first piping 6e is adjusted so that the pressure inside the vacuum chamber body 6a when evaporated by the depressurizing device 6j remains within a pressure range where water droplets do not freeze.

[0036] Furthermore, the heater 6c heats the wafer storage container 20 (container body 20a and door 20b) to a temperature that does not damage it (for example, 30°C to 100°C). Due to the heating by the heater 6c, the temperature of the water droplets does not fall below 0°C.

[0037] (Additional depressurization treatment) After the drying process described above has been performed for a preset time, the control unit 8 performs an additional depressurization process by controlling the first valve 6f, the second valve 6h, and the depressurization device 6j while the opening of the vacuum chamber body 6a is closed by the opening / closing lid 6b. Specifically, the control unit 8 performs an additional depressurization process inside the vacuum chamber body 6a by closing the first valve 6f and opening the second valve 6h, and then driving the depressurization device 6j. In other words, the control unit 8 performs an additional depressurization process inside the vacuum chamber body 6a by evacuating the inside of the vacuum chamber body 6a via the second piping 6g, the second valve 6h, and piping 6i using the depressurization device 6j.

[0038] Here, the second pipe 6g has a larger conductance compared to the first pipe 6e. Therefore, the flow rate of gas discharged by the depressurization device 6j during the additional depressurization process increases, and the pressure inside the vacuum chamber body 6a during the additional depressurization process becomes lower than the pressure during the drying process.

[0039] The control unit 8 executes the additional depressurization process described above for a predetermined time. The processing time for executing the additional depressurization process may be arbitrarily set based on a processing time confirmed in advance, or it may be set according to the type (manufacturer, model) of the wafer storage container 20 to be dried. In such a case, for example, correspondence information (first correspondence information) that associates the type of wafer storage container 20 with the processing time of the additional depressurization process is stored in the HDD of the control unit 8. The CPU of the control unit 8 obtains the processing time corresponding to the type of wafer storage container 20 to be dried from the first correspondence information stored in the HDD and executes the additional depressurization process.

[0040] The type of wafer storage container 20 to be subjected to drying can be determined, for example, based on identification information attached to the wafer storage container 20. Here, the identification information includes at least information on the type (manufacturer, model) of the wafer storage container 20. When the wafer storage container 20 is loaded into the casing 1a at the load port 2, the control unit 8 reads the identification information attached to the wafer storage container 20 to obtain the type of wafer storage container 20 to be subjected to drying. Examples of identification information include RFID (Radio Frequency Identification) tags, barcodes, and QR codes (registered trademarks).

[0041] (Process for determining the state of dryness) After performing the additional depressurization process described above, the control unit 8 determines the drying state of the wafer storage container 20 (container body 20a and door 20b). Specifically, the control unit 8 determines that the drying state of the object (wafer storage container 20) is sufficient if the pressure inside the vacuum chamber 6 reached after the additional depressurization process reaches a predetermined threshold. Conversely, the control unit 8 determines that the drying state of the object is insufficient if the pressure inside the vacuum chamber 6 reached after the additional depressurization process does not reach a predetermined threshold.

[0042] When drying is performed by vacuum drying, the water droplets on the surface of the object (wafer storage container 20) are evaporated to dry it. However, since water evaporates as molecules and becomes a gas, it is difficult to reduce the pressure below a certain level. On the other hand, when drying is sufficient and there is no moisture, there is no evaporation of water molecules, so it is possible to reduce the pressure to the maximum achievable pressure of the vacuum device 6j's exhaust capacity.

[0043] The control unit 8 then acquires the pressure measured by the pressure sensor 6d and compares the pressure reached after the additional depressurization process with a preset reference pressure (a predetermined threshold) to determine the dry state of the wafer storage container 20. Here, the reference pressure is set based on the relationship between the previously confirmed dry state and the reached pressure. For example, the reference pressure is set based on the pressure reached when an additional depressurization process is performed on a dry wafer storage container 20. As an example, the reference pressure is set to about 10 Pa.

[0044] The reference pressure may be set according to the type (manufacturer, model) of the wafer storage container 20. The wafer storage container 20 differs in material and shape (total surface area of ​​the wafer storage container 20) depending on the manufacturer and model. When the material and shape differ, the amount of outgassing during the additional depressurization process changes, and therefore the target pressure changes. In this case, the control unit 8 determines the type of object (wafer storage container 20) and determines the drying state of the object (wafer storage container 20) using a predetermined threshold (reference pressure) set according to the type of object (wafer storage container 20). In such a case, for example, correspondence information (second correspondence information) associating the type of wafer storage container 20 with the reference pressure is stored in the HDD of the control unit 8. The CPU of the control unit 8 obtains the reference pressure corresponding to the type of wafer storage container 20 to be dried from the second correspondence information stored in the HDD, and determines the drying state of the wafer storage container 20 (container body 20a and door 20b) based on the obtained reference pressure. The type of wafer storage container 20 is determined by the identification information of the wafer storage container 20 described above.

[0045] The following describes an example of the drying state determination process by the control unit 8 using Figure 3. Figure 3 is a diagram illustrating an example of the drying state determination process by the control unit 8 according to the first embodiment. In Figure 3, the vertical axis represents pressure (Pa), and the horizontal axis represents time, showing a graph (curve C1) of the pressure inside the vacuum chamber 6 when drying and additional depressurization are performed. For example, as shown in curve C1 of Figure 3, the pressure inside the vacuum chamber 6 decreases after drying and then decreases further after additional depressurization. The control unit 8 determines the drying state of the wafer storage container 20 (container body 20a and door 20b) based on the pressure inside the vacuum chamber 6 after additional depressurization. The combined processing time for drying and additional depressurization is approximately 5 to 7 minutes.

[0046] For example, in Figure 3, since the pressure P2 after performing an additional depressurization process for a predetermined time "T1" is below the reference pressure P1, the control unit 8 determines that the wafer storage container 20 (container body 20a and door 20b) is sufficiently dry. If the control unit 8 determines that the drying process is sufficient, it terminates the drying of the wafer storage container 20 (container body 20a and door 20b) by the vacuum chamber 6.

[0047] On the other hand, if pressure P2 exceeds the reference pressure P1, the control unit 8 determines that the wafer storage container 20 (container body 20a and door 20b) is not sufficiently dry and performs an additional drying process on the wafer storage container 20 (container body 20a and door 20b).

[0048] (Additional drying treatment) As described above, if the control unit 8 determines that the wafer storage container 20 (container body 20a and door 20b) is not sufficiently dry, it will perform an additional drying process. For example, the control unit 8 will control the process to repeat the same drying process as the first drying process. In such a case, after the additional depressurization process, with the opening of the vacuum chamber body 6a closed by the opening / closing lid 6b, the control unit 8 will open the first valve 6f, close the second valve 6h, drive the depressurization device 6j, and perform heating with the heater 6c to perform the drying process. Here, the control unit 8 performs the drying process at the same temperature and for the same duration as the first drying process. Note that if the pressure inside the vacuum chamber 6 is to be returned to the pressure at the time of the first drying process, this may be done by introducing gas from a gas introduction port (not shown).

[0049] Alternatively, if the control unit 8 determines that the drying state is insufficient, it controls the system to perform a drying process with the same pressure and heating conditions as the initial drying process, but with a shorter drying time. In this case, after the additional depressurization process, with the opening of the vacuum chamber body 6a closed by the opening / closing lid 6b, the control unit 8 opens the first valve 6f, closes the second valve 6h, drives the depressurization device 6j, and performs heating with the heater 6c to perform the drying process. Here, the control unit 8 performs a drying process with a shorter processing time than the initial drying process.

[0050] Alternatively, if the control unit 8 determines that the drying state is insufficient, it can perform a drying process that continues the additional depressurization process until the reference pressure is reached. In other words, the control unit 8 controls the system to perform a drying process that evaporates water droplets by additional depressurization. In such cases, the control unit 8 performs the drying process by continuing the control in the additional depressurization process. In this case, the control unit 8 can also perform heating using the heater 6c.

[0051] Here, the processing content of the additional drying treatment described above may be set by selecting one of the three options described above in advance, or the processing content may be changed according to the pressure state after the additional depressurization treatment. In other words, the processing content of the drying treatment may be changed according to the degree of pressure after the additional depressurization treatment. In such cases, multiple thresholds are set for the pressure inside the vacuum chamber 6, thereby setting multiple different pressure ranges. The control unit 8 changes the processing after the additional depressurization treatment according to the pressure range reached by the pressure inside the vacuum chamber 6 after the additional depressurization treatment.

[0052] Figure 4 is a diagram illustrating the pressure range according to the first embodiment. Figure 4 shows a graph with pressure (Pa) on the vertical axis and time on the horizontal axis. For example, as shown in Figure 4, in addition to the reference pressure P1, reference pressures P3 and P4 are set for the pressure inside the vacuum chamber 6. In this case, the pressure ranges "P1-P3" and "P3-P4" are set. The control unit 8 changes the processing content depending on which range the pressure after the additional depressurization process falls into.

[0053] For example, if the pressure after the additional depressurization process falls within the pressure range "P3-P4", the control unit 8 controls the system to perform a drying process with the same pressure and heating conditions as the initial drying process, but with a shorter drying time, or to perform the same drying process as the initial drying process. In the case of the pressure range "P3-P4", the difference from the reference pressure is large, so it is more efficient to perform the same process as the initial drying process. Also, if the degree of pressure reduction during the additional depressurization process is small, there is a possibility that water droplets have frozen, and it is necessary to melt the water droplets. Therefore, if the pressure after the additional depressurization process falls within the pressure range "P3-P4", the control unit 8 controls the system to perform a drying process similar to the initial drying process again.

[0054] Furthermore, for example, if the pressure after the additional pressure reduction treatment falls within the pressure range "P1-P3", the control unit 8 performs a drying process that continues the additional pressure reduction treatment until it reaches the reference pressure. In the case of the pressure range "P1-P3", the difference from the reference pressure is small, so it is more efficient to continue the additional pressure reduction treatment. Therefore, if the pressure after the additional pressure reduction treatment falls within the pressure range "P1-P3", the control unit 8 controls the process to, for example, continue the additional pressure reduction treatment while simultaneously performing heating with the heater 6c.

[0055] Although Figure 4 illustrates the case where two pressure ranges are set, the embodiment is not limited to this, and it may also be possible to set three or more pressure ranges.

[0056] Next, the processing procedure by the control unit 8 of the wafer storage container cleaning apparatus 1 will be explained using Figure 5. Figure 5 is a flowchart showing the processing procedure by the control unit 8 according to the first embodiment. Figure 5 shows the processing after the container body 20a and door 20b have been brought into the vacuum chamber body 6a and the opening of the vacuum chamber body 6a has been closed by the opening / closing lid 6b.

[0057] For example, as shown in Figure 5, the control unit 8 controls the heater 6c, the first valve 6f, the second valve 6h, and the pressure reducing device 6j to perform a drying process for a preset time (step S101).

[0058] Next, the control unit 8, while keeping the opening / closing cover 6b closed, controls the first valve 6f, the second valve 6h, and the pressure reducing device 6j to perform an additional pressure reduction process for a predetermined time (step S102).

[0059] Next, the control unit 8 obtains the pressure after a predetermined time has elapsed (after additional depressurization) (step S103) and determines whether or not it has reached the reference pressure (step S104). If the pressure after additional depressurization has reached the reference pressure (step S104, Yes), the control unit 8 terminates the drying process for the wafer storage container 20 (container body 20a and door 20b).

[0060] On the other hand, if the pressure after the additional depressurization process in step S104 has not reached the reference pressure (step S104, No), the control unit 8 performs an additional drying process (step S105) and then repeats the process from step S102 onwards. If the additional drying process is a process that continues the additional depressurization process, the control unit 8 acquires the pressure during the process over time, and terminates the drying process for the wafer storage container 20 (container body 20a and door 20b) when the acquired pressure reaches the reference pressure.

[0061] According to the first embodiment, after the drying process, the control unit 8 performs an additional depressurization process to lower the pressure inside the vacuum chamber 6 to a level lower than the pressure during the drying process, and determines the drying state of the wafer storage container 20 based on the pressure inside the vacuum chamber 6 reached after the additional depressurization process. Therefore, the wafer storage container cleaning apparatus 1 can determine the drying state of the object based on the reached pressure, which changes depending on whether or not water molecules evaporate, and makes it possible to confirm the drying state of the wafer storage container 20. As a result, the wafer storage container cleaning apparatus 1 eliminates the use of wafer storage containers that are not sufficiently dried, and makes it possible to suppress the occurrence of defects in semiconductor wafers caused by contamination from the wafer storage container. Furthermore, since the wafer storage container cleaning apparatus 1 can confirm the drying state of the wafer storage container 20, it can avoid spending more time than necessary on the drying process and efficiently dry the wafer storage container 20.

[0062] Furthermore, according to the first embodiment, the control unit 8 determines that the wafer storage container 20 is sufficiently dry when the pressure inside the vacuum chamber 6 reached after the additional depressurization process reaches the reference pressure. Also, the control unit 8 determines that the wafer storage container 20 is not sufficiently dry when the pressure inside the vacuum chamber 6 reached after the additional depressurization process does not reach the reference pressure, and performs an additional drying process on the wafer storage container 20.Therefore, the wafer storage container cleaning apparatus 1 can reliably dry the wafer storage container 20.

[0063] Furthermore, according to the first embodiment, multiple thresholds are set for the pressure inside the vacuum chamber 6, thereby setting multiple different pressure ranges. The control unit 8 changes the processing after the additional depressurization process according to the pressure range reached by the pressure inside the vacuum chamber 6 after the additional depressurization process. Therefore, the wafer storage container cleaning apparatus 1 can perform additional drying processing according to the degree of drying of the wafer storage container 20, and can perform the additional drying processing efficiently.

[0064] Furthermore, according to the first embodiment, the control unit 8 determines the type of wafer storage container 20 and determines the drying state of the wafer storage container 20 using a reference pressure set according to the type of wafer storage container 20. Therefore, the wafer storage container cleaning apparatus 1 can determine the drying state of the wafer storage container 20 using a reference pressure set according to the material and shape of the wafer storage container 20, and can appropriately determine the drying state of various wafer storage containers 20.

[0065] (Other embodiments) In the first embodiment described above, a first pipe 6e with low conductance and a second pipe 6g with high conductance are connected to the vacuum chamber body 6a, and a drying process is performed via the first pipe 6e and an additional vacuum process is performed via the second pipe 6g. However, the embodiment is not limited to this, and a single pipe may be connected to the vacuum chamber body 6a, and both the drying process and the additional vacuum process may be performed via this pipe.

[0066] In such cases, for example, a pipe having the same conductance as the second pipe 6g is connected to the vacuum chamber body 6a, and the drying process and additional depressurization process are performed through this pipe. Here, in order to adjust the pressure during the drying process, the vacuum chamber 6 is connected to a gas supply unit so that dry gas is supplied to the inside. That is, during the drying process, the control unit 8 controls the depressurization device 6j to reduce the pressure inside the vacuum chamber body 6a, and at the same time controls the gas supply unit to supply dry gas to the inside of the vacuum chamber body 6a, thereby preventing the pressure inside the vacuum chamber body 6a from dropping too low.

[0067] During the additional depressurization process, the control unit 8 reduces the pressure inside the vacuum chamber body 6a by stopping the supply of dry gas by the gas supply unit.

[0068] In this way, by using dry gas during the drying process, both the drying process and the additional vacuum treatment can be performed in a single pipe. Furthermore, by using dry gas during the drying process, an airflow can be formed that expels the evaporated water molecules with the dry gas, which is expected to improve drying efficiency.

[0069] Furthermore, in the first embodiment described above, the case in which the wafer storage container 20 is the object to be dried was explained. However, the embodiments are not limited to this, and the object to be dried by vacuum drying may also be something other than the wafer storage container 20. In other words, the drying state confirmation method of the present application can be applied to devices other than wafer storage container cleaning devices.

[0070] Furthermore, in the first embodiment described above, a case was described in which, after the drying process, the control unit 8 performs an additional depressurization process to lower the pressure inside the vacuum chamber 6 to a level lower than the pressure during the drying process, and the drying state of the wafer storage container 20 is determined based on the pressure inside the vacuum chamber 6 reached after the additional depressurization process. However, the embodiments are not limited to this. For example, after the additional depressurization process, the control unit 8 reduces the pressure inside the vacuum chamber 6 to a predetermined pressure lower than the pressure during the drying process, and then stops the depressurization inside the vacuum chamber 6. The control unit 8 may then maintain the state in which the depressurization inside the vacuum chamber 6 is stopped for a predetermined time and determine the drying state of the wafer storage container 20 based on whether or not the pressure measured by the pressure sensor 6d rises. The predetermined pressure is a pressure higher than the reference pressure P1. For example, the predetermined pressure is greater than 10 Pa and less than or equal to 50 Pa.

[0071] In determining the drying state using the above-described method, the control unit 8 determines that the drying state of the object (e.g., wafer storage container 20) is insufficient if the pressure inside the vacuum chamber 6 rises from the predetermined pressure after a predetermined time has elapsed with the depressurization of the vacuum chamber 6 stopped. For example, if water droplets remain in the wafer storage container 20, maintaining the pressure inside the vacuum chamber 6 at a predetermined pressure lower than the pressure during the drying process for a predetermined time will cause the remaining water droplets to evaporate, increasing the pressure inside the vacuum chamber 6. Therefore, the control unit 8 determines that the drying state of the object is insufficient if the pressure inside the vacuum chamber 6 rises from the predetermined pressure. On the other hand, if the pressure inside the vacuum chamber 6 does not rise from the predetermined pressure after a predetermined time has elapsed with the depressurization of the vacuum chamber 6 stopped, the control unit 8 determines that the drying state of the object (e.g., wafer storage container 20) is sufficient. For example, if no water droplets remain in the wafer storage container 20, even if the inside of the vacuum chamber 6 is maintained at a predetermined pressure lower than the pressure during the drying process for a predetermined time, the water droplets will not evaporate, and the pressure inside the vacuum chamber 6 will not rise. Therefore, the control unit 8 determines that the object is sufficiently dry if the pressure inside the vacuum chamber 6 does not rise above the predetermined pressure. [Explanation of Symbols]

[0072] 1. Wafer storage container cleaning device 6 Vacuum chamber 6j pressure reducing device 8 Control Unit

Claims

1. A drying tank that holds the object to be dried inside, A vacuum device for reducing the pressure inside the drying tank, A control unit controls the vacuum device to reduce the pressure inside the drying tank to a pressure lower than atmospheric pressure, thereby performing a drying process to evaporate and remove moisture. Equipped with, The control unit performs an additional depressurization process for a predetermined time after the drying process so that the pressure inside the drying tank becomes lower than the pressure during the drying process, and determines that the drying state of the object is sufficient when the pressure inside the drying tank reached after the additional depressurization process reaches a predetermined threshold, and determines that the drying state of the object is insufficient when the pressure does not reach the predetermined threshold.

2. A drying tank for holding an object to be dried inside, A vacuum device for reducing the pressure inside the drying tank, A control unit controls the vacuum device to reduce the pressure inside the drying tank and perform a drying process to evaporate and remove moisture. Equipped with, The control unit, after the drying process, performs an additional depressurization process for a predetermined time such that the pressure inside the drying tank becomes lower than the pressure during the drying process, and determines the drying state of the object based on the pressure inside the drying tank reached after the additional depressurization process. Multiple thresholds are set for the pressure inside the drying tank, resulting in multiple different pressure ranges. Set The control unit responds to the pressure range reached by the internal pressure of the drying tank after the additional depressurization process. A drying apparatus that modifies the processing after the additional reduced pressure treatment.

3. The drying apparatus according to claim 1, wherein the control unit determines that the drying state of the object is insufficient and performs an additional drying process on the object.

4. The drying apparatus according to any one of claims 1 to 3, wherein the object is a wafer storage container including a FOUP (Front Opening Unified Pod) and a FOSB (Front Opening Shipping Box).

5. The drying apparatus according to claim 1, wherein the control unit determines the type of object and determines the drying state of the object using the predetermined threshold set according to the type of object.

6. By controlling a vacuum device that reduces the pressure inside a drying tank that holds the object to be dried, the inside of the drying tank is reduced to a pressure lower than atmospheric pressure, thereby performing a drying process in which moisture is evaporated and removed. After the drying process, an additional depressurization process is performed for a predetermined time to lower the pressure inside the drying tank to a level lower than the pressure during the drying process. If the pressure inside the drying tank reached after the additional depressurization process reached a predetermined threshold, the drying state of the object is determined to be sufficient. If the pressure does not reach the predetermined threshold, the drying state of the object is determined to be insufficient. A method for checking the dry state, including the following.

7. A drying tank that holds the object to be dried inside, A vacuum device for reducing the pressure inside the drying tank, A control unit controls the vacuum device to reduce the pressure inside the drying tank and perform a drying process to evaporate and remove moisture. Equipped with, The control unit, after the drying process, reduces the pressure inside the drying tank to a predetermined pressure lower than the pressure during the drying process, and determines the drying state of the object based on whether the pressure inside the drying tank rises from the predetermined pressure after a predetermined time has elapsed with the depressurization of the inside of the drying tank stopped.

8. Drying tank and By controlling a vacuum device that reduces the pressure inside a drying tank that holds the object to be dried, a drying process is performed in which moisture is evaporated and removed by reducing the pressure inside the drying tank. After the drying process, the pressure inside the drying tank is reduced to a predetermined pressure lower than the pressure during the drying process. The drying state of the object is determined based on whether or not the pressure inside the drying tank rises from the predetermined pressure after a predetermined time has elapsed with the depressurization of the inside of the drying tank stopped. A method for checking the dry state, including the following.

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