CMP grinding equipment convenient to maintain

Abstract

The CMP grinding equipment convenient to maintain comprises a cleaning area and a grinding area arranged on one side of the cleaning area, a first maintenance channel is arranged between the grinding area and the cleaning area, the first maintenance channel comprises an inlet and outlet communicated with the outside, and a first mechanical arm capable of moving in the extending direction of the first maintenance channel is arranged in the first maintenance channel. Through the arrangement, maintenance personnel can enter the first maintenance channel from the outside through the entrance and exit, maintenance of the grinding area and the cleaning area is achieved, maintenance and debugging of components in the CMP grinding equipment are facilitated, in addition, the first maintenance channel is arranged in the CMP grinding equipment and serves as a setting area and a moving area of the first mechanical arm at the same time, and the maintenance efficiency of the CMP grinding equipment is improved. In other words, the first maintenance channel does not occupy the extra space of the CMP grinding equipment, the first maintenance channel for maintenance personnel to maintain the equipment is additionally arranged under the condition that it is guaranteed that the overall size of the CMP grinding equipment is basically unchanged, and the technical problems that existing equipment is difficult to maintain and large in size are solved.

Description

Technical Field

[0001] The invention relates to the technical field of CMP grinding, and in particular to a CMP grinding device which is easy to maintain. Background Art

[0002] Chemical mechanical polishing (CMP) is a key step in wafer manufacturing, and its function is to reduce the unevenness of the wafer surface. Existing CMP grinding equipment generally does not have a special passage for maintenance personnel to enter the equipment, which makes it difficult to perform routine maintenance of the equipment. In addition, CMP equipment has high requirements for the overall volume of the equipment. If additional space is opened up to add a maintenance passage, the overall volume of the equipment will be expanded, the occupied space of the factory building will be increased, and it will be detrimental to the overall layout of the production line. Summary of the invention

[0003] The purpose of the present invention is to address the technical problems existing in the background technology and to propose a CMP polishing equipment that is easy to maintain, including a cleaning area and a polishing area arranged on one side of the cleaning area, a first maintenance channel is arranged between the polishing area and the cleaning area, the first maintenance channel includes at least one entrance and exit connected to the outside world, the polishing equipment also includes a first manipulator, the first manipulator is arranged in the first maintenance channel and can move in the extension direction of the first maintenance channel.

[0004] Further, the grinding area includes at least two grinding lines, a second maintenance channel is formed between adjacent grinding lines, and the second maintenance channel is connected to the first maintenance channel.

[0005] Furthermore, the grinding area includes a loading platform, which is disposed in the second maintenance channel and can move in the extension direction of the second maintenance channel.

[0006] Furthermore, the grinding line includes at least two grinding units, the grinding unit includes a grinding pad and a grinding assembly, the grinding assembly includes a support seat and a grinding part connected to the support seat, the support seat is arranged on one side of the grinding pad, and the grinding part is arranged above the grinding pad, and the grinding part can move laterally relative to the support seat so that the grinding part moves toward the circumferential side of the grinding pad.

[0007] Further, the support seat includes a support portion extending outward, the grinding portion includes a connecting portion and a grinding head arranged below the connecting portion, and the connecting portion is connected to the support portion;

[0008] The supporting part is provided with a sliding groove, in which a sliding rack is arranged; a sliding wheel is provided on a protrusion at one side of the connecting part, the sliding wheel is arranged in the sliding groove and connected with the sliding rack.

[0009] Furthermore, the grinding unit also includes a grinding table for carrying a grinding pad, and a liquid supplier, a grinding pad dresser, a dresser cleaner and a grinding pad cleaner arranged around the grinding table.

[0010] Furthermore, the cleaning area includes at least two cleaning lines, a third maintenance channel is formed between adjacent cleaning lines, and the third maintenance channel is connected to the first maintenance channel.

[0011] Furthermore, the cleaning area also includes a second robot, the cleaning line includes a plurality of cleaning modules, the second robot is arranged in the third maintenance channel and can move in the extension direction of the third maintenance channel, and the second robot is used for transferring wafers between the cleaning modules.

[0012] Furthermore, the cleaning area also includes a transmission module, which is arranged between adjacent cleaning lines to divide the third maintenance channel into an upper maintenance channel and a lower maintenance channel, and a second manipulator is arranged in both the upper maintenance channel and the lower maintenance channel.

[0013] Furthermore, it also includes a front area and a third robot. The front area is arranged on the side of the cleaning area away from the grinding area. A fourth maintenance channel is formed between the front area and the cleaning area. The fourth maintenance channel is connected to the third maintenance channel. The third robot is arranged in the fourth maintenance channel and can move in the extension direction of the fourth maintenance channel.

[0014] Compared with the prior art, the present invention has the following beneficial technical effects: the present invention forms a first maintenance channel between the interval-set grinding area and the cleaning area, and movably sets the first manipulator in the first maintenance channel. One side of the first maintenance channel can form an entrance and exit and communicate with the outside. When the CMP grinding equipment needs to be repaired or maintained, the first manipulator can be moved to the side of the first maintenance channel away from the entrance and exit, and the maintenance personnel can enter the first maintenance channel from the outside through the entrance and exit to achieve maintenance of the grinding area and the cleaning area, which is convenient for maintenance and debugging of the components inside the CMP grinding equipment, and maintenance is convenient. Further, the present invention sets the first maintenance channel inside the CMP grinding equipment, and at the same time serves as the setting area and the moving area of ​​the first manipulator, that is, the first maintenance channel of the present invention does not occupy the extra space of the CMP grinding equipment. Based on the above settings, the present invention, through reasonable layout, adds a first maintenance channel for maintenance personnel to repair the equipment while ensuring that the overall volume of the CMP grinding equipment remains basically unchanged, solving the technical problems of the existing equipment being difficult to repair and large in volume. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a three-dimensional state diagram of the device of the present invention;

[0016] Figure 2 A top view of the device of the present invention;

[0017] Figure 3 It is a partial enlarged view of the grinding unit;

[0018] Figure 4Another partial enlarged view of the grinding unit. DETAILED DESCRIPTION

[0019] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0020] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or component referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and the like are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, features defined as "first", "second", and the like may explicitly or implicitly include one or more features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0021] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or a specific connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood by specific circumstances.

[0022] The specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0023] like Figure 1-Figure 4 As shown, the present invention proposes a CMP polishing device that is easy to maintain, including a cleaning area 1 and a polishing area 2 arranged on one side of the cleaning area 1, a first maintenance channel 41 is arranged between the polishing area 2 and the cleaning area 1, and the first maintenance channel 41 includes at least one entrance and exit 411 connected to the outside, and the polishing device also includes a first manipulator 51, which is arranged in the first maintenance channel 41 and can move in the extension direction of the first maintenance channel 41. In some embodiments, the cleaning area 1 is used to realize the cleaning and / or pre-cleaning of incoming and / or returning wafers, the polishing area 2 is used to realize the processing and grinding of wafers to realize the flattening of wafers, and the first manipulator 51 is used to realize the round-trip transmission of wafers between the cleaning area 1 and the polishing area 2.

[0024] It can be understood that the present invention forms a first maintenance channel 41 between the interval-set grinding area 2 and the cleaning area 1, and movably sets the first manipulator 51 in the first maintenance channel 41. One side of the first maintenance channel 41 can form an entrance and exit 411 and communicate with the outside. When the CMP grinding equipment needs to be repaired or maintained, the first manipulator 51 can be moved to the side of the first maintenance channel 41 away from the entrance and exit 411, and the maintenance personnel can enter the first maintenance channel 41 from the outside through the entrance and exit 411 to achieve maintenance of the grinding area 2 and the cleaning area 1, which is convenient for maintenance and debugging of the components inside the CMP grinding equipment. Further, the present invention sets the first maintenance channel 41 inside the CMP grinding equipment, and at the same time serves as the setting area and the moving area of ​​the first manipulator 51, that is, the first maintenance channel 41 of the present invention does not occupy the extra space of the CMP grinding equipment. Based on the above settings, the present invention, through reasonable layout, adds a first maintenance channel 41 for maintenance personnel to repair the equipment while ensuring that the overall volume of the CMP grinding equipment remains basically unchanged, thereby solving the technical problems of difficult maintenance and large volume of existing equipment.

[0025] Further, in some embodiments, the grinding area 2 includes at least two grinding lines 21, and the two grinding lines 21 can operate in parallel to improve the grinding throughput of the grinding area 2, and a second maintenance channel 42 is formed between adjacent grinding lines 21, and the second maintenance channel 42 is connected to the first maintenance channel 41. Optionally, in some embodiments, the grinding area 2 can be provided with a grinding line 21 on both the upper and lower sides, and a second maintenance channel 42 is formed between the upper and lower grinding lines 21, and the second maintenance channel 42 includes at least one communication port, and the communication port is connected to the first maintenance channel 41.

[0026] It can be understood that the present invention forms a second maintenance channel 42 between the interval-arranged grinding lines 21. At the same time, the second maintenance channel 42 is connected to the first maintenance channel 41. When the grinding area 2 needs to be repaired or maintained, the maintenance personnel can enter the second maintenance channel 42 from the first maintenance channel 41 to achieve maintenance and debugging of the internal components of the grinding area 2, which is convenient for maintenance.

[0027] Furthermore, in some embodiments, the grinding area 2 also includes a loading platform 22, which is arranged in the second maintenance channel 42 and can move in the extension direction of the second maintenance channel 42, and the movable loading platform 22 is used to realize the round-trip transfer of the wafer between the grinding line 21 and the first robot.

[0028] It can be understood that the second maintenance channel 42 is arranged inside the grinding area 2 and is also used as the setting area and the moving area of ​​the loading platform 22, that is, the second maintenance channel 42 of the present invention does not occupy the extra space of the grinding area 2. Based on the above arrangement, the present invention adds a second maintenance channel 42 for maintenance personnel to repair equipment through reasonable layout while ensuring that the overall volume of the grinding area remains basically unchanged, thereby solving the technical problems of difficult maintenance and large volume of the existing grinding area.

[0029] Further, in some embodiments, the grinding line 21 includes at least two grinding units 211, the grinding unit 211 includes a grinding pad 201 and a grinding assembly 202, the grinding assembly 202 includes a support seat 2021 and a grinding portion 2022 connected to the support seat 2021, the support seat 2021 is arranged on one side of the grinding pad 201, the grinding portion 2022 is arranged above the grinding pad 201, and the grinding portion 2022 can move laterally relative to the support seat 2021 so that the grinding portion 2022 moves toward the circumferential side direction of the grinding pad 201.

[0030] Optionally, in some embodiments, the grinding part 2022 can move back and forth from one side of the periphery of the grinding pad 201 toward the other side. As an implementation mode, the grinding pad 201 can form a loading station and a maintenance station on both sides of its periphery, respectively, and the grinding part 2022 can move back and forth between the loading station and the maintenance station. Through the above-mentioned arrangement, when processing the wafer, the grinding part 2022 can be controlled to move to the loading station to realize the loading of the wafer. After the grinding part 2022 obtains the wafer, it can be moved back to the grinding pad 201 to realize the processing and polishing of the wafer. When the grinding part 2022 needs to be repaired and replaced, the grinding part 2022 can be controlled to move to the maintenance station. At this time, the maintenance personnel can repair and replace the grinding part 2022 on one side of the grinding pad 201, which is convenient to operate.

[0031] It can be understood that based on the above-mentioned grinding unit 211, the maintenance personnel only need to repair and replace the grinding part 2022 on one side of the grinding pad 201, which is safe and convenient to operate, and solves the technical problem that "the existing grinding unit maintenance personnel need to bend over and stand on the grinding pad to repair and replace the grinding part 2022, which is inconvenient to operate and easily causes damage to the grinding pad and contaminates the grinding unit."

[0032] Further, in some embodiments, the support seat 2021 includes a support portion 20211 extending outward, the grinding portion 2022 includes a connecting portion 20221 and a grinding head 20222 disposed below the connecting portion 20221, the connecting portion 20221 is slidably connected to the supporting portion 20211, and through the above arrangement, the connecting portion 20221 can move back and forth in the extension direction of the supporting portion 20211 to drive the grinding head 20222 to move. Optionally, a sliding groove is provided on the supporting portion 20211, a sliding rack is provided in the sliding groove, and a sliding wheel is provided on the side protrusion of the connecting portion 20221, the sliding wheel is disposed in the sliding groove and connected to the sliding rack, and the sliding wheel can move relative to the sliding rack to drive the connecting portion 20221 to move.

[0033] Furthermore, in some embodiments, the grinding unit also includes a grinding table 203 for carrying a grinding pad 201, and a liquid supply device 204, a grinding pad dresser 205, a dresser cleaner 206 and a grinding pad cleaner 207 arranged around the grinding table 203. The liquid supply device 204 cooperates with the grinding pad dresser 205 to achieve the rest of the grinding pad 201, the dresser cleaner 206 is used to achieve the cleaning of the grinding pad dresser 205, and the grinding pad cleaner 207 is used for the grinding pad dresser 205 to rinse the grinding pad 201 when the grinding pad dresser 205 is dressing the grinding pad 201, so as to prevent the dressing residue from entering the wafer processing area and damaging the wafer.

[0034] Further, in some embodiments, the cleaning area 1 of the present invention includes at least two cleaning lines 11, and the cleaning lines 11 can operate in parallel to achieve cleaning and / or pre-cleaning of wafers to improve the throughput of the cleaning area 1. A third maintenance channel 43 is formed between adjacent cleaning lines 11, and the third maintenance channel 43 is connected to the first maintenance channel 41. Optionally, in some embodiments, the cleaning area 1 is provided with a cleaning line 11 on both the upper and lower sides, and a third maintenance channel 43 is formed between the upper and lower cleaning lines 11. The third maintenance channel 43 is provided with a first connecting port, and the third maintenance channel 43 is connected to the first maintenance channel 41 through the first connecting port.

[0035] It can be understood that the present invention forms a third maintenance channel 43 between the cleaning lines 11 arranged at intervals. At the same time, the third maintenance channel 43 is connected to the first maintenance channel 41. When the cleaning area 1 needs to be repaired or maintained, the maintenance personnel can enter the third maintenance channel 43 from the first maintenance channel 41 to achieve maintenance and debugging of the internal components of the grinding area 2, which is convenient for maintenance.

[0036] Furthermore, in some embodiments, the cleaning area 1 further includes a second robot 52, the cleaning line 11 includes a plurality of cleaning modules 111, the second robot 52 is disposed in the third maintenance channel 43 and can move in the extension direction of the third maintenance channel 43, and the second robot 52 is used to transfer wafers between the cleaning modules 111. Optionally, in some embodiments, the cleaning area 1 further includes a transfer module 12, which is disposed between adjacent cleaning lines 11 to divide the third maintenance channel 43 into an upper maintenance channel and a lower maintenance channel, and the second robot 52 is disposed in both the upper maintenance channel and the lower maintenance channel.

[0037] It can be understood that the third maintenance channel 43 is arranged inside the grinding area 2 and is also used as the setting area and the moving area of ​​the second manipulator 52, that is, the third maintenance channel 43 of the present invention does not occupy the extra space of the cleaning area 1. Based on the above arrangement, the present invention adds a third maintenance channel 43 for maintenance personnel to repair equipment through reasonable layout while ensuring that the overall volume of the cleaning area remains basically unchanged, thereby solving the technical problems of the existing grinding area being difficult to repair and having a large volume.

[0038] Furthermore, in some embodiments, the cleaning module 111 includes a first functional module, a second functional module and a third functional module arranged in sequence, the first functional module and the second functional module both include cleaning units 1111 stacked up and down, the third functional module includes a cleaning unit 1111 and a drying unit 1112 stacked up, the drying unit 1112 is arranged above the cleaning unit 1111, the cleaning unit 1111 can realize pre-cleaning and fine cleaning of the wafer, and the drying unit 1112 is used to dry the wafer after cleaning.

[0039] It can be understood that different specifications of cleaning units 1111 and drying units 1112 may cause unit idling due to their different processing times for wafers. For example, wafers need to be cleaned through units A and B respectively. If the processing time of unit B is faster than that of unit A, unit B will have to wait for unit A, causing unit B to idle, thereby reducing the efficiency of the entire machine. The present invention configures the first functional module, the second functional module and the third functional module to form a mode of five cleaning units 1111 and one drying unit 1112 respectively, thereby being compatible with a variety of cleaning processes. For example, it can be configured as three roller cleaning units, two pen cleaning units, and one drying unit, or four roller cleaning units, a pen cleaning unit, a drying unit, and other cleaning processes, thereby effectively decomposing a single cleaning module with a bottleneck and improving the cleaning efficiency and the efficiency of the entire machine.

[0040] Further, in some embodiments, the CMP polishing equipment also includes a pre-zone 3 and a third robot 53. The pre-zone 3 is arranged on a side of the cleaning zone 1 away from the polishing zone 2. A fourth maintenance channel 44 is formed between the pre-zone 3 and the cleaning zone 1. The fourth maintenance channel 44 is connected to the third maintenance channel 43. The third robot 53 is arranged in the fourth maintenance channel 44 and can move in the extension direction of the fourth maintenance channel 44. Optionally, the third maintenance channel is provided with a second connecting port on a side away from its first connecting port, and the second connecting port is connected to the fourth maintenance channel 44.

[0041] Through the above-mentioned arrangement, the movable third robot 53 can realize the round-trip transportation of wafers between the front area 3 and the cleaning area 1. Specifically, when materials are received, the third robot 53 can receive wafers from different positions of the front area 3 by moving up and down, and transfer them to the transmission module 12. The wafers are moved to the first robot 51 through the transmission module 12. The first robot 51 moves in the first maintenance channel 41 to transfer the wafers to the loading platform 22 at different positions. The loading platform 22 moves in the second maintenance channel 42, and can transfer the wafers to different grinding units 211 for processing and polishing. When returning materials, similarly, the loading table 22 can transfer the wafer to the first robot 51 based on the movement in the second maintenance channel 42, and the first robot 51 can transfer the wafer to the first functional module at different positions based on the movement in the first maintenance channel 41 to realize the cleaning of the wafer. Then, the second robot 52 takes the wafer out of the first functional module, and transfers the wafer to the second functional module, the third functional module, and the third robot 53 in sequence by moving in the third maintenance channel 43. The third robot 53 receives the wafer from the second robot 52 at different positions by moving in the fourth maintenance channel 44, and transfers it to the front area to realize the return of the wafer.

[0042] It can be understood that the present invention forms a fourth maintenance channel 44 between the pre-area 3 and the cleaning area 1 which are arranged at intervals, and the third manipulator 53 is movably arranged in the fourth maintenance channel 44. When the pre-area 3 or the cleaning area 1 needs to be repaired or maintained, the maintenance personnel can enter the fourth maintenance channel 44 through the first maintenance channel 41 and the third maintenance channel 43 to achieve maintenance of the pre-area 3 and the cleaning area 1. Further, the present invention sets the fourth maintenance channel 44 inside the CMP grinding equipment, and at the same time serves as the setting area and the moving area of ​​the third manipulator 53, that is, the fourth maintenance channel 44 of the present invention does not occupy the additional space of the CMP grinding equipment. Based on the above arrangement, the present invention, through reasonable layout, adds a fourth maintenance channel 44 for maintenance personnel to repair the equipment while ensuring that the overall volume of the CMP grinding equipment remains basically unchanged, thereby solving the technical problems of difficult maintenance and large volume of the existing equipment. Optionally, in some embodiments, the fourth maintenance channel 44 can also be provided with open ports at both ends, and the maintenance personnel can also directly enter the fourth maintenance channel 44 through the open ports.

[0043] The above is one or more implementation methods provided in combination with specific contents, and it is not intended that the specific implementation of the present invention is limited to these descriptions. Any similarity or similarity with the method, structure, etc. of the present invention, or any technical deduction or replacement made on the premise of the concept of the present invention, shall be regarded as the protection scope of the present invention.

Claims

1. A CMP polishing device that is easy to maintain, comprising a cleaning area (1) and a polishing area (2) arranged on one side of the cleaning area (1), characterized in that: A first maintenance channel (41) is provided between the grinding area (2) and the cleaning area (1), the first maintenance channel (41) comprising at least one entrance and exit (411) communicating with the outside, the grinding device further comprising a first manipulator (51), the first manipulator (51) being arranged in the first maintenance channel (41) and being movable in the extension direction of the first maintenance channel (41).

2. The CMP polishing equipment easy to maintain according to claim 1, characterized in that: The grinding area (2) comprises at least two grinding lines (21), a second maintenance channel (42) is formed between adjacent grinding lines (21), and the second maintenance channel (42) is connected to the first maintenance channel (41).

3. The CMP polishing equipment easy to maintain according to claim 2, characterized in that: The grinding area (2) comprises a loading platform (22), wherein the loading platform (22) is arranged in the second maintenance channel (42) and can move in the extension direction of the second maintenance channel (42).

4. The CMP polishing equipment easy to maintain according to claim 2, characterized in that: The grinding line (21) comprises at least two grinding units (211), the grinding unit (211) comprises a grinding pad (201) and a grinding assembly (202), the grinding assembly (202) comprises a support seat (2021) and a grinding portion (2022) connected to the support seat (2021), the support seat (2021) is arranged on one side of the grinding pad (201), the grinding portion (2022) is arranged above the grinding pad (201), and the grinding portion (2022) can move laterally relative to the support seat (2021) so that the grinding portion (2022) moves toward the circumferential side of the grinding pad (201).

5. The CMP polishing equipment easy to maintain according to claim 4, characterized in that: The support seat (2021) comprises a support portion (20211) extending outward, the grinding portion (2022) comprises a connecting portion (20221) and a grinding head (20222) arranged below the connecting portion (20221), and the connecting portion (20221) is connected to the support portion (20211); The support portion (20211) is provided with a sliding groove, a sliding rack is arranged in the sliding groove, and the connecting portion (20221) is provided with a sliding wheel protruding on one side, the sliding wheel is arranged in the sliding groove and connected to the sliding rack.

6. The CMP polishing equipment easy to maintain according to claim 4, characterized in that: The grinding unit (211) further comprises a grinding table (203) for carrying the grinding pad (201), and a liquid supplier (204), a grinding pad dresser (205), a dresser cleaner (206) and a grinding pad cleaner (207) arranged around the grinding table (203).

7. The CMP polishing equipment easy to maintain according to claim 1, characterized in that: The cleaning area (1) comprises at least two cleaning lines (11), a third maintenance channel (43) is formed between adjacent cleaning lines (11), and the third maintenance channel (43) is connected to the first maintenance channel (41).

8. The CMP polishing equipment easy to maintain according to claim 7, characterized in that: The cleaning area (1) further comprises a second robot (52), wherein the second robot (52) is arranged in the third maintenance channel (43) and can move in the extension direction of the third maintenance channel (43).

9. The CMP polishing equipment easy to maintain according to claim 8, characterized in that: The cleaning area (1) further comprises a transmission module (12), wherein the transmission module (12) is arranged between adjacent cleaning lines (11) to divide the third maintenance channel (43) into an upper maintenance channel and a lower maintenance channel, wherein a second manipulator (52) is arranged in each of the upper maintenance channel and the lower maintenance channel.

10. The CMP polishing equipment easy to maintain according to claim 7, characterized in that: The invention also comprises a front area (3) and a third robot (53), wherein the front area (3) is arranged on a side of the cleaning area (1) away from the grinding area (2), a fourth maintenance channel (44) is formed between the front area (3) and the cleaning area (1), the fourth maintenance channel (44) is connected to the third maintenance channel (43), and the third robot (53) is arranged in the fourth maintenance channel (44) and can move in the extension direction of the fourth maintenance channel (44).

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