Abstract:
Provided is a load lock device which includes: a container with an opening formed therein and configured to be selectively maintained at an atmospheric environment and a vacuum atmosphere; a holding unit arranged within the container and configured to hold objects to be processed; an elevation mechanism configured to vertically move the holding unit; and a pressure regulating mechanism configured to vacuum-evacuate the container through the opening of the container. The elevation mechanism includes at least two vertically-extended elevation shaft members connected to the holding unit; and a drive unit configured to vertically move the elevation shaft members. The elevation shaft members are arranged opposite each other with the opening interposed therebetween.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of Japanese Patent Application No. 2012-246327, filed on Nov. 8, 2012, in the Japan Patent Office, the disclosure of which is incorporated herein in its entirety by reference. 
     TECHNICAL FIELD 
     The present disclosure relates to a load lock device. 
     BACKGROUND 
     Load lock devices include a load lock chamber for holding semiconductor wafers and an elevation drive unit for moving the load lock chamber up and down. The load lock chamber is vertically movable within a container. In such a device, an elevation rod is connected to a central portion of the load lock chamber. The elevation rod extends outward from a central portion of the container such that it is connected to the elevation drive unit. 
     In a processing system provided with a load lock device, the process must be performed in a low-impurity environment. For this reason, the load lock device must have a high degree of vacuum to reduce impurities. In order to achieve a high degree of vacuum, a large-diameter exhaust port is necessary. It is however difficult to have a large-diameter exhaust port in the container because the elevation rod is connected to the central portion of the load lock chamber. In addition, the installation of the large-diameter exhaust port may cause an increase in size of the load lock device. If a plurality of exhaust ports is used, the complexity of the device may be increased. 
     SUMMARY 
     Some embodiments of the present disclosure provide a load lock device capable of rapidly realizing a high degree of vacuum with a simple configuration. 
     According to an embodiment of the present disclosure, provided is a load lock device which includes: a container with an opening formed therein and configured to be selectively maintained at an atmospheric environment and a vacuum atmosphere; a holding unit arranged within the container and configured to hold objects to be processed; an elevation mechanism configured to vertically move the holding unit; and a pressure regulating mechanism configured to vacuum-evacuate the container through the opening of the container. The elevation mechanism includes at least two vertically-extended elevation shaft members connected to the holding unit; and a drive unit configured to vertically move the elevation shaft members. The elevation shaft members are arranged opposite each other with the opening interposed therebetween. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the present disclosure, and together with the general description given above and the detailed description of the embodiments given below, serve to explain the principles of the present disclosure. 
         FIG. 1  is a top view showing a configuration of a processing system equipped with a load lock device according to one embodiment. 
         FIG. 2  is a view showing a cross-sectional configuration of the load lock device. 
         FIG. 3  is a view showing another cross-sectional configuration of the load lock device. 
         FIG. 4  is a schematic top view of the load lock device. 
         FIG. 5  is a partially enlarged sectional view of a first holding unit of the load lock device. 
         FIG. 6  is a partially enlarged sectional view of a second holding unit of the load lock device. 
         FIG. 7  is a view showing a cross-sectional configuration of a holding unit of a load lock device according to another embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to various embodiments, examples of which are illustrated in the accompanying drawings. In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the present disclosure. However, it will be apparent to one of ordinary skill in the art that the present disclosure may be practiced without these specific details. In other instances, well-known methods, procedures, systems, and components have not been described in detail so as not to unnecessarily obscure aspects of the various embodiments. Like reference numerals in the drawings denote like elements, and a duplicate description thereof will be omitted. 
       FIG. 1  is a top view showing a configuration of a processing system  100  equipped with a load lock device according to one embodiment. As shown in  FIG. 1 , the processing system  100  includes mounting tables  102   a  to  102   d , receiving containers  104   a  to  104   d , a loader module  106 , load lock devices LL 1  and LL 2 , process modules  108   a  to  108   c  and a transfer chamber  110 . 
     The mounting tables  102   a  to  102   d  are arranged along one side of the loader module  106 . The receiving containers  104   a  to  104   d  are respectively mounted on the mounting tables  102   a  to  102   d . Semiconductor wafers W (objects to be processed) are accommodated within the receiving containers  104   a  to  104   d.    
     A first transfer robot  112  is installed within the loader module  106  and is movable along a rail R. The first transfer robot  112  extracts the semiconductor wafers W accommodated within one of the receiving containers  104   a  to  104   d  and transfers the same to the load lock device LL 1  or LL 2 . 
     The load lock devices LL 1  and LL 2  are installed along another side of the loader module  106 . Each of the load lock devices LL 1  and LL 2  constitutes a preliminary depressurizing chamber. The load lock devices LL 1  and LL 2  are installed between the loader module  106  (kept in an atmospheric environment) and the transfer chamber  110  (a vacuum chamber) and are respectively connected to the transfer chamber  110  through gate valves G 1  (see  FIG. 3 ). The load lock devices LL 1  and LL 2  are, in this embodiment, independently connected to the loader module  106  through gate valves G 2  and G 3  (see  FIG. 3 ). 
     The transfer chamber  110  is a chamber capable of being depressurized. A second transfer robot  114  is installed to be rotatable around its vertical axis within the transfer chamber  110 . The process modules  108   a  to  108   c  are respectively connected to the transfer chamber  110  through a respective gate valve G. The second transfer robot  114  extracts the semiconductor wafers W from the load lock devices LL 1  or LL 2  and transfers the same to the process modules  108   a  to  108   c  one after another. Each of the process modules  108   a  to  108   c  of the processing system  100  may be, e.g., a physical vapor deposition (PVD) apparatus (sputtering apparatus), a chemical vapor deposition (CVD) apparatus, an etching apparatus or the like. 
     Next, the load lock devices LL 1  and LL 2  will be described in detail. The load lock device LL 1  and the load lock device LL 2  are identical in configuration with each other. In this embodiment, the load lock device LL 1  will be described in detail as an example.  FIG. 2  is a view showing a cross-sectional configuration of the load lock device LL 1 .  FIG. 3  is a view showing another cross-sectional configuration of the load lock device LL 1 .  FIG. 4  is a schematic top view of the load lock device LL 1 .  FIG. 5  is a partially enlarged sectional view of a first holding unit provided in the load lock device LL 1 .  FIG. 6  is a partially enlarged sectional view of a second holding unit provided in the load lock device LL 1 . Specifically,  FIG. 2  is the cross-sectional view of the load lock device LL 1  when viewed in a transfer direction of the semiconductor wafers W, and  FIG. 3  is the cross-sectional view of the load lock device LL 1  when viewed in a direction orthogonal to the transfer direction of the semiconductor wafers W. 
     As shown in  FIGS. 2 to 4 , the load lock device LL 1  includes a chamber (container)  1 , a first holding unit  3 , a first elevation mechanism  5 , a first pressure regulating mechanism  7 , a second holding unit  9 , a second elevation mechanism  11  and a second pressure regulating mechanism  13 . The operation of the load lock device LL 1  is controlled by a control unit (not shown). 
     The chamber  1  is configured such that an internal pressure thereof is changed between an internal pressure of the transfer chamber  110  and an atmospheric pressure. The chamber  1  is made of, e.g., an aluminum alloy or the like. As shown in  FIG. 3 , on a sidewall  1   a  of the chamber  1 , there are formed inlet/outlets C 1   a  and C 1   b  through which the semiconductor wafers W are carried into or out of the chamber  1  by the first transfer robot  112  and an inlet/outlet C 2  through which the semiconductor wafers W are carried into or out of the chamber  1  by the second transfer robot  114 . The inlet/outlets C 1   a  and C 1   b  are respectively formed in upper and lower portions of the chamber  1  (i.e., in positions where the first holding unit  3  is positioned at the uppermost location and where the second holding unit  9  is positioned at the lowermost location). The inlet/outlets C 1   a  and C 1   b  are in communication with the loader module  106  through the gate valves G 2  and G 3 . The inlet/outlet C 2  is formed in the vertical central position of the chamber  1 . The inlet/outlet C 2  is in communication with the transfer chamber  110  through the gate valve G 1 . 
     A first opening O 1  is formed in a ceiling portion  1   b  of the chamber  1 . As shown in  FIG. 4 , the first opening O 1  has a substantially circular shape and is positioned substantially at the center of the ceiling portion  1   b  of the chamber  1 . The diameter R of the first opening O 1  is substantially equal to that of the semiconductor wafer W. 
     A second opening O 2  is formed in a bottom portion  1   c  of the chamber  1 . The second opening O 2  has a substantially circular shape and is positioned substantially at the center of the bottom portion  1   c  of the chamber  1 . The diameter of the second opening O 2  is substantially equal to that of the semiconductor wafer W. 
     First and second stepped portions  1   d  and  1   e  are formed at the inner side of the sidewall  1   a  of the chamber  1 . The first and second stepped portions  1   d  and  1   e  are formed over the entire circumference within the chamber  1 . The first and second stepped portions  1   d  and  1   e  are formed to face each other. The first stepped portion  1   d  is formed at the side of the ceiling portion  1   b  of the chamber  1 . The second stepped portion  1   e  is formed at the side of the bottom portion  1   c  of the chamber  1 . 
     The first holding unit  3  is arranged within the chamber  1  to hold the semiconductor wafers W. As an example, the first holding unit  3  is configured to hold five semiconductor wafers W. The first holding unit  3  is installed so that it can be vertically moved within the chamber  1  by the first elevation mechanism  5  (which will be described later). The first holding unit  3  includes a base portion  17  and a support portion  19 . 
     The base portion  17  is a plate-like member and has a substantially circular shape when viewed from the top. A recess  18  (see  FIG. 5 ) opened toward the ceiling portion  1   b  of the chamber  1  is formed in a peripheral region of the base portion  17 . A seal member  20  is disposed in the recess  18 . A periphery of an upper surface  17   a  of the base portion  17  is brought into contact with the first stepped portion  1   d  of the chamber  1 . When the first holding unit  3  is positioned in the uppermost location, the base portion  17  is brought into contact with the first stepped portion  1   d . The seal member  20  is disposed at a position where the seal member  20  is brought into contact with the first stepped portion  1   d . Thus, a space S 1  defined by the first holding unit  3  (or the base portion  17 ) and the chamber  1  is hermetically sealed. 
     The support portion  19  is installed on the base portion  17 . The support portion  19  includes support pieces  19   a  protruding toward the center of the base portion  17 . The semiconductor wafers W are mounted on the respective support pieces  19   a  so that they are supported by the support portion  19 . The support portion  19  is positioned within the space S 1  when the first holding unit  3  is positioned at the uppermost location. A cover  22  is arranged above the support portion  19 . 
     The first elevation mechanism  5  is a mechanism configured to vertically move the first holding unit  3  and includes a first elevation unit  5   a  and a second elevation unit  5   b . As shown in  FIG. 4 , the first elevation unit  5   a  and the second elevation unit  5   b  of the first elevation mechanism  5  are arranged in peripheral regions of the chamber  1  opposite each other with the first opening O 1  of the chamber  1  interposed therebetween. The first elevation unit  5   a  and the second elevation unit  5   b  are identical in configuration with each other. As an example, a configuration of the first elevation unit  5   a  will be described in detail. The first elevation unit  5   a  includes a shaft (elevation shaft member)  24 , bellows  26  (see  FIGS. 2 and 5 ), a nut  28 , a transfer shaft  30  and a motor  32 . The nut  28 , the transfer shaft  30  and the motor  32  constitute a first drive unit. 
     The shaft  24  is a rod-like member, which serves as a threaded shaft on which a male thread (see  FIG. 5 ) is formed. The shaft  24  is inserted into a through-hole K 1  formed in the ceiling portion  1   b  of the chamber  1  such that it is disposed across inside and outside of the chamber  1 . The shaft  24  is connected to the base portion  17  of the first holding unit  3 . The shaft  24  is connected to the peripheral region of the base portion  17  at a location positioned more inward than the recess  18 . In some embodiments, the shaft  24  and the base portion  17  may be connected to each other by, e.g., forming a through-hole in the base portion  17 , inserting the shaft  24  into the through-hole and fastening them by a bolt (not shown). The length of the shaft  24  is set such that the first holding unit  3  can travel between the inlet/outlet C 1   a  and the inlet/outlet C 2 . 
     The motor  32  is connected to the shaft  24  through the transfer shaft  30 . The shaft  24  is rotated in conjunction with the rotation of the motor  32 . By the rotation of the shaft  24 , the first elevation mechanism  5  moves the first holding unit  3  up and down. The operation of the motor  32  is controlled by the control unit. 
     The bellows  26  is a tubular member having a bellows structure. The shaft  24  is arranged to extend through the bellows  26 . The bellows  26  has flexibility, air-tightness and resiliency. The bellows  26  extends and retracts along with the vertical movement of the first holding unit  3 . An upper end of the bellows  26  is air-tightly joined to a ceiling surface  1 A of the chamber  1 . A lower end of the bellows  26  is air-tightly joined to an upper surface  17   a  of the base portion  17 . 
     A female thread is formed on an inner surface of the nut  28  and balls are arranged on the inner surface of the nut  28 . The nut  28  is coupled with the shaft  24 . The nut  28  and the shaft  24  constitute a ball screw. The nut  28  is arranged in a peripheral region of the ceiling portion  1   b  of the chamber  1 . 
     The first pressure regulating mechanism  7  includes a gate valve  34  and a vacuum pump  36 . The gate valve  34  is arranged on an upper surface  1   bs  of the chamber  1 . The gate valve  34  is arranged to cover the first opening O 1  of the chamber  1 . An opening/closing operation of the gate valve  34  is controlled by the control unit. 
     The vacuum pump  36  is installed on the gate valve  34 . The vacuum pump  36  is configured to depressurize the space S 1  defined by the chamber  1  and the first holding unit  3 . The vacuum pump  36  is a pump capable of realizing a vacuum degree of, e.g., 10 −7  to 10 −8  Torr. Upon opening the gate valve  34 , the vacuum pump  36  performs the depressurization (or vacuum-evacuation) operation to maintain the space Si defined by the first holding unit  3  and the chamber  1  at a predetermined degree of vacuum. The first pressure regulating mechanism  7  may further include a configuration in which an internal state of the space S 1  is returned from a vacuum environment to an atmospheric environment. 
     The second holding unit  9  is arranged within the chamber  1  to hold the semiconductor wafers W. As an example, the second holding unit  9  is configured to hold five semiconductor wafers W. The second holding unit  9  is installed so that it can be vertically moved within the chamber  1  by the second elevation mechanism  11  (which will be described later). The second holding unit  9  includes a base portion  42  and a support portion  44 . 
     The base portion  42  is a plate-like member and has a substantially circular shape when viewed from the top. A recess  41  (see  FIG. 6 ) opened toward the bottom portion  1   c  of the chamber  1  is formed in a peripheral region of the base portion  42 . A seal member  43  is disposed in the recess  41 . A lower surface  42   a  of the base portion  42  is brought into contact with the second stepped portion  1   e  of the chamber  1 . When the second holding unit  9  is positioned in the lowermost location, the base portion  42  is brought into contact with the second stepped portion  1   e . The seal member  43  is disposed in a position where the seal member  43  is brought into contact with the second stepped portion  1   e . Thus, a space S 2  defined by the second holding unit  9  (or the base portion  42 ) and the chamber  1  is hermetically sealed. 
     The support portion  44  is installed on the base portion  42 . The support portion  44  includes support pieces  44   a  protruding toward the center of the base portion  42 . The semiconductor wafers W are mounted on the respective support pieces  44   a  so that they are supported by the support portion  44 . The support portion  44  is positioned within the space S 2  when the second holding unit  9  is positioned in the lowermost location. A cover  46  is arranged below the support portion  44 . 
     The second elevation mechanism  11  is a mechanism configured to vertically move the second holding unit  9 . The second elevation mechanism  11  is arranged in the peripheral regions of the chamber  1  and includes a first elevation unit  11   a  and a second elevation unit  11   b  positioned opposite each other with the second opening O 2  of the chamber  1  interposed therebetween. The first elevation unit  11   a  and the second elevation unit  11   b  are identical in configuration with each other. As an example, a configuration of the first elevation unit  11   a  will be described in detail. The first elevation unit  11   a  includes a shaft (elevation shaft member)  48 , a bellows  50 , a nut  52 , a transfer shaft  54  and a motor  56 . The nut  52 , the transfer shaft  54  and the motor  56  constitute a second drive unit. 
     The shaft  48  is a rod-like member, which serves as a threaded shaft on which a male thread (see  FIG. 6 ) is formed. The shaft  48  is inserted into a through-hole K 2  formed in the bottom portion  1   c  of the chamber  1  so that it is disposed across inside and outside of the chamber  1 . The shaft  48  is connected to the base portion  42  of the second holding unit  9 . The shaft  48  is connected to the peripheral region of the base portion  42  at a location positioned more inward than the recess  41 . In some embodiments, the shaft  48  and the base portion  42  may be connected to each other by, e.g., forming a through-hole in the base portion  42 , inserting the shaft  48  into the through-hole and fastening them by a bolt (not shown). The length of the shaft  48  is set such that the second holding unit  9  can travel between the inlet/outlet C 1   b  and the inlet/outlet C 2 . 
     The motor  56  is connected to the shaft  48  through the transfer shaft  54 . The shaft  48  is rotated in conjunction with the rotation of the motor  56 . By the rotation of the shaft  48 , the second elevation mechanism  11  moves the second holding unit  9  up and down. An operation of the motor  56  is controlled by the control unit. 
     The bellows  50  is a tubular member having a bellows structure. The shaft  48  is arranged to extend through the bellows  50 . The bellows  50  has flexibility, air-tightness and resiliency. The bellows  50  extends and retracts along with the vertical movement of the second holding unit  9 . An upper end of the bellows  50  is air-tightly joined to a lower surface  42   a  of the base portion  42 . A lower end of the bellows  50  is air-tightly joined to a bottom surface  1 B of the chamber  1 . 
     A female thread is formed on an inner surface of the nut  52  and balls are arranged on the inner surface of the nut  52 . The nut  52  is coupled with the shaft  48 . The nut  52  and the shaft  48  constitute a ball screw. The nut  52  is arranged in the peripheral region of the bottom portion  1   c  of the chamber  1 . 
     The second pressure regulating mechanism  13  includes a gate valve  58  and a vacuum pump  60 . The gate valve  58  is arranged on a lower surface  1   cs  of the chamber  1 . The gate valve  58  is arranged to cover the second opening O 2  of the chamber  1 . An opening/closing operation of the gate valve  58  is controlled by the control unit. 
     The vacuum pump  60  is installed on the gate valve  58 . The vacuum pump  60  is configured to depressurize the space S 2  defined by the chamber  1  and the second holding unit  9 . The vacuum pump  60  is a pump capable of realizing a vacuum degree of, e.g., 10 −7  to 10 −8  Torr. Upon opening the gate valve  58 , the vacuum pump  60  performs the depressurization (or vacuum-evacuation) operation to maintain the space S 2  defined by the second holding unit  9  and the chamber  1  at a predetermined degree of vacuum. The second pressure regulating mechanism  13  may further include a configuration in which an internal state of the space S 2  is returned from a vacuum environment to an atmospheric environment. 
     Next, a description will be made of one example of the operation of the processing system  100  equipped with the load lock device LL 1 . In the processing system  100 , a carrier in which a predetermined number of semiconductor wafers W to be processed are accommodated, is received within the respective receiving containers  104   a  to  104   d . Then, the first transfer robot  112  moves just in front of, e.g., the receiving container  104   d  (see  FIG. 1 ), and extracts a semiconductor wafer W from the receiving container  104   d . Subsequently, the first transfer robot  112  transfers the extracted semiconductor wafer W to the front of the load lock device LL 1 . 
     In parallel with the aforementioned operation, the gate valve G 2  of the load lock device LL 1  is opened such that an interior of the chamber  1  is set to be an atmospheric environment. At this time, in the load lock device LL 1 , the first holding unit  3  waits at a position corresponding to the inlet/outlet C 1   a . If the gate valve G 2  is opened, the first transfer robot  112  transfers the extracted semiconductor wafer W to the first holding unit  3 . In this way, the first transfer robot  112  transfers the five semiconductor wafers W. 
     Thereafter, in the load lock device LL 1 , the gate valve G 2  is closed and the gate valve  34  of the first pressure regulating mechanism  7  is opened. The space S 1  is kept at a predetermined degree of vacuum by the vacuum pump  36 . Subsequently, in the load lock device LL 1 , the first elevation mechanism  5  moves the first holding unit  3  down to a position corresponding to the inlet/outlet C 2 . 
     Then, in the load lock device LL 1 , the gate valve G 1  is opened if the first holding unit  3  is moved down to the position corresponding to the inlet/outlet C 2 . Thus, the space  51  of the load lock device LL 1  communicates with the transfer chamber  110 . Subsequently, the second transfer robot  114  extracts the semiconductor wafer W from the first holding unit  3  and transfers the same to, e.g., the process module  108   b  (see  FIG. 1 ). The process module  108   b  performs a predetermined process onto the semiconductor wafer W. 
     After all the semiconductor wafers W are extracted from the first holding unit  3  in the above way, the first elevation mechanism  5  of the load lock device LL 1  moves the first holding unit  3  upward such that the first holding unit  3  is positioned in the uppermost position (near the inlet/outlet C 1   a ). Then, in the load lock device LL 1 , the first pressure regulating mechanism  7  returns the internal state of the space  51  to an atmospheric environment. In the load lock device LL 1 , the aforementioned operation is repeatedly carried out. 
     If the predetermined process for the semiconductor wafers W is carried out by the process modules  108   a  to  108   c , the second elevation mechanism  11  of the load lock device LL 1  moves the second holding unit  9  upward, whereby the second holding unit  9  waits at the position corresponding to the inlet/outlet C 2 . Then, the gate valve G 1  of the load lock device LL 1  is opened so that the chamber  1  communicates with the transfer chamber  110 . Subsequently, the second transfer robot  114  transfers the processed semiconductor wafers W to the second holding unit  9 . 
     If the transfer of the semiconductor wafers W using the second transfer robot  114  is finished, the second holding unit  9  is moved downward by the second elevation mechanism  11  of the load lock device LL 1 . If the second holding unit  9  is positioned in the lowermost location (near the inlet/outlet C 1   b ), the internal state of the space S 2  is returned to an atmospheric environment by the second pressure regulating mechanism  13 . Thereafter, the gate valve G 3  is opened. Thus, the chamber  1  is under an atmospheric environment (i.e., communicates with the loader module  106 ). Then, the first transfer robot  112  extracts the semiconductor wafers W from the second holding unit  9  and transfers the same to, e.g., the receiving container  104   a.    
     As described above, in this embodiment, the first opening O 1  and the second opening O 2 , each of which is in communication with the inside of the chamber  1 , are formed in the ceiling portion  1   b  and the bottom portion  1   c  of the chamber  1 , respectively. The pair of the shafts  24  (and  48 ) used in vertically moving the first holding unit  3  (and the second holding unit  9 ) is arranged opposite each other with the first opening O 1  (and the second opening O 2 ) interposed therebetween. 
     This configuration allows regions for the formation of the first opening O 1  and the second opening O 2  to be obtained in the chamber  1 . This makes it possible to increase the diameter of the first opening O 1  and the second opening O 2 . It is therefore possible to rapidly realize a high degree of vacuum in the spaces S 1  and S 2  using the first and second pressure regulating mechanisms  7  and  13 . Further, since the aforementioned configuration of the present disclosure can be applied to a conventional device, it is possible to prevent the conventional device from becoming large and complex. Accordingly, in the load lock devices LL 1  and LL 2 , a high degree of vacuum can be rapidly realized with a simple configuration. 
     In this embodiment, the shafts  24  and  48  are respectively connected (joined) to the base portions  17  and  42 . In the configuration that maintains the spaces S 1  and S 2  defined by each of the base portions  17  and  42  and the chamber  1  at a vacuum state, it is necessary to secure air-tightness of the spaces S 1  and S 2  defined by the chamber  1  and each of the base portions  17  and  42 . To do this, it is required to bring each of the base portions  17  and  42  and the chamber  1  into close contact with each other. Thus, a force for bringing each of the base portions  17  and  42  and the chamber  1  into close contact with each other needs to be sufficiently transferred from the shafts  24  and  48  to the base portions  17  and  42 , respectively. For that reason, the base portions  17  and  42  need to be made rigid. Unfortunately, this increases the thickness of each of the base portions  17  and  42 . In this embodiment, the shafts  24  and  48  are respectively connected to the base portions  17  and  42 . Thus, the force for bringing each of the base portions  17  and  42  and the chamber  1  into close contact with each other can be stably transferred from the shafts  24  and  48  to the base portions  17  and  42 , respectively. This reduces the thickness of each of the base portions  17  and  42 , which makes it possible to reduce the size of the apparatus. 
     As described above, each of the load lock devices LL 1  and LL 2  includes the first holding unit  3  and the second holding unit  9 . With this configuration, for example, the semiconductor wafers W can be supplied to the transfer chamber  110  using the second holding unit  9  while the first holding unit  3  holds the semiconductor wafers W in the atmospheric environment. This enables the load lock devices LL 1  and LL 2  to perform two processes in parallel, which increases the processing efficiency. 
     The present disclosure is not limited to the above embodiment. In some embodiments, the first holding unit  3  may be implemented with a configuration shown in  FIG. 7 .  FIG. 7  is a view showing a cross-sectional configuration of a holding unit of a load lock device according to another embodiment. As shown in  FIG. 7 , a first holding unit  3 A includes a base portion  62  having a substantially circular shape when viewed from the top, a vertical wall  64  installed upright on the base portion  62 , and support parts  65  installed in the vertical wall  64 . A recess  62   a  is formed in a peripheral region of the base portion  62 . A seal member  20 A is arranged in the recess  62   a . A cover  66  is installed above the vertical wall  64 . 
     In the first holding unit  3 A, the shafts  24  may be connected to the vertical wall  64 . Alternatively, the shafts  24  may be connected to the base portion  62  through the vertical wall  64 . In some embodiments, from the viewpoint of close contact of the base portion  62  and the chamber  1 , the shafts  24  may be connected to the base portion  62 . 
     While in the above embodiment, each of the first opening O 1  and the second opening O 2  has been described to be formed in the central region of each of the ceiling portion  1   b  and the bottom portion  1   c  of the chamber  1 , the present disclosure is not limited thereto. Alternatively, each of the first opening O 1  and the second opening O 2  may be formed in a position offset from the central region of each of the ceiling portion  1   b  and the bottom portion  1   c.    
     In some embodiments, a mechanism configured to heat and cool the semiconductor wafers W may be installed in each of the first holding unit  3  and the second holding unit  9 . 
     While in the above embodiment, each of the load lock devices LL 1  and LL 2  has been described to be connected to the transfer chamber  110  via the gate valve G 1 , but is not limited thereto. In some embodiments, the gate valve G 1  may be omitted. 
     According to the present disclosure, it is possible to rapidly realize a high degree of vacuum with a simple configuration. 
     While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the disclosures. Indeed, the novel devices described herein may be embodied in a variety of other forms. Furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the disclosures. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the disclosures.