Wafer bearing device and operation method thereof

Abstract

The invention provides a wafer bearing device and an operation method thereof, the wafer bearing device comprises a bearing assembly, a detection assembly, a safety cover plate and a control unit, and the bearing assembly is placed in an accommodating chamber in wafer processing equipment. The detection assembly comprises a first position sensor and a second position sensor, and the first position sensor is arranged on the inner wall of the containing cavity and used for detecting the position of the bearing assembly. The control unit is used for preventing the bearing assembly from moving after the first position sensor detects the bearing assembly. The second position sensor is arranged on the bearing assembly and used for detecting the position of the safety cover plate. The control unit is used for relieving stopping and allowing the bearing assembly to continue moving after the second position sensor detects the safety cover plate. According to the wafer bearing device, the movement of the bearing assembly can be limited through the first position sensor, and then an operator is prompted to place the safety cover plate on the bearing assembly, so that damage to the operator and materials caused by the fact that the safety cover plate is not placed on the bearing assembly is prevented.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor manufacturing technology, and in particular to a wafer carrying device and an operating method thereof. Background Art

[0002] At present, in lithography machines (such as ASML's NXT model), a strong magnetic plate is installed at the bottom of the wafer stage, which can make the wafer stage suspend in the chamber and rotate at high speed during exposure. When the wafer stage is maintained or repaired, the wafer stage and the strong magnetic plate need to be removed synchronously through the operation panel, and the whole strong magnet will be exposed to the outside. After the strong magnetic plate is exposed, if the operator holding a metal tool approaches the strong magnetic plate, it is easy. Some other materials are also made of metal, and the materials are easily adsorbed and damaged when they are close to the strong magnetic plate.

[0003] In the prior art, the photolithography machine provides a safety cover placed on the strong magnetic plate to shield the surface of the strong magnetic plate when the strong magnetic plate is removed. However, in actual operation, there are often cases where the safety cover is not placed on the strong magnetic plate during maintenance. The photolithography machine will not have any prompts or alarms for this, nor will it prevent the wafer stage from being removed, which poses a great safety hazard.

[0004] Therefore, for technicians in this field, how to design a wafer carrying device that can remind the operator to place a safety cover on the strong magnetic plate during maintenance or repair is a technical problem that urgently needs to be solved. Summary of the invention

[0005] In order to solve the technical problems in the prior art, the purpose of the present invention is to provide a wafer carrying device and an operating method thereof, which can limit the movement of the carrying component through a first position sensor, and then prompt the operator to place a safety cover on the carrying component to prevent damage to the operator and materials due to failure to place a safety cover on the carrying component.

[0006] To achieve the above-mentioned purpose, the present invention provides a wafer carrying device, including: a carrying component, a detection component, a safety cover and a control unit, wherein the carrying component is placed in a accommodating chamber inside a wafer processing device; the detection component includes a first position sensor and a second position sensor, the first position sensor is arranged on the inner wall of the accommodating chamber, the first position sensor is used to detect the position of the carrying component, and the control unit is used to prevent the carrying component from moving after the first position sensor detects the carrying component; the second position sensor is arranged on the carrying component, the second position sensor is used to detect the position of the safety cover, and the control unit is used to release the blockage and allow the carrying component to continue moving after the second position sensor detects the safety cover.

[0007] Optionally, the supporting assembly includes a wafer stage and a strong magnetic plate, the wafer stage is placed on the strong magnetic plate and covers a partial area of ​​the strong magnetic plate; the second position sensor is fixed on the area of ​​the wafer stage not covered by the strong magnetic plate; the safety cover is used to be placed on the area of ​​the wafer stage not covered by the strong magnetic plate and cover at least a portion of the second position sensor.

[0008] Optionally, the first position sensor is arranged on an inner wall of the accommodating chamber corresponding to the moving path of the bearing assembly.

[0009] Optionally, the strong magnetic plate includes a first outer wall close to the cavity opening of the accommodating chamber; the first position sensor is arranged on the top wall or bottom wall of the accommodating chamber between a preset edge and the cavity opening, and the preset edge is the position of the first outer wall corresponding to the top wall or bottom wall of the accommodating chamber.

[0010] Optionally, the strong magnetic plate further includes a second outer wall perpendicular to the first outer wall, the length of the second outer wall is 1000 mm, and the horizontal distance between the first position sensor and the second outer wall is 500 mm to 700 mm.

[0011] Optionally, the number of the second position sensors is at least two, and at least two of the second position sensors are arranged in sequence and spaced apart in a direction parallel to the second outer wall; the control unit is used to allow the bearing assembly to move after at least two of the second position sensors detect the safety cover.

[0012] Optionally, the number of the second position sensors is two groups, the number of the second position sensors in each group is at least two, and the number of the safety covers is also at least two; the two groups of the second position sensors are respectively arranged on both sides of the wafer carrier; the control unit is used to allow the supporting assembly to move after all the second position sensors in any group detect the safety cover.

[0013] Optionally, the first position sensor and / or the second position sensor is configured as a photoelectric sensor or a limit switch.

[0014] To achieve the above object, the present invention further provides an operating method of a wafer carrier, comprising any one of the wafer carriers described above, the operating method comprising:

[0015] S01: driving the carrying assembly to move toward the opening of the accommodating chamber by the control unit;

[0016] S02: Determine whether the first position sensor detects the bearing assembly;

[0017] S03: If the first position sensor detects the load-bearing assembly, the first position sensor sends a braking signal to the control unit;

[0018] S04: the control unit stops the bearing assembly from moving after receiving the braking signal;

[0019] S05: Determine whether the second position sensor detects the safety cover;

[0020] S06: If the second position sensor detects the safety cover, the second position sensor sends a driving signal to the control unit;

[0021] S07: After receiving the driving signal, the control unit releases the blockage and allows the bearing assembly to continue moving.

[0022] Optionally, the bearing assembly includes a wafer carrier and a strong magnetic plate, the wafer carrier is placed on the strong magnetic plate and covers a partial area of ​​the strong magnetic plate; the number of the second position sensors is two groups, the number of the second position sensors in each group is at least two, and the two groups of the second position sensors are respectively arranged on the strong magnetic plates on both sides of the wafer carrier;

[0023] In S07, the step of releasing the blocking and allowing the bearing assembly to continue to move after the control unit receives the driving signal includes:

[0024] If the control unit receives driving signals sent by all the second position sensors in each group, the control unit releases the blockage and allows the bearing assembly to continue moving.

[0025] The present application provides a wafer carrier device and an operating method thereof, wherein the device can limit the removal of a carrier component through a first position sensor, thereby reminding the operator to place a safety cover on the carrier component. After the safety cover is in place, the control unit can release the limit of the carrier component and allow the carrier component to be smoothly removed. Such a setting can prevent the operator from causing damage to the operator and materials due to failure to place a safety cover on the carrier component, help the operator to safely and smoothly complete the repair or maintenance of the carrier component, and improve the safety and reliability of the operation of the wafer carrier device. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of the top view of the structure of the bearing assembly in a preferred embodiment of the present invention;

[0027] Figure 2 A schematic diagram of a use scenario of a wafer carrying device in a preferred embodiment of the present invention;

[0028] Figure 3The figure is a flow chart of an operation method of a wafer carrier device in a preferred embodiment of the present invention.

[0029] The reference numerals are described as follows:

[0030] Carrying component 1; wafer carrier 11; strong magnetic plate 12; first outer wall 121; second outer wall 122; detection component 2; first position sensor 21; second position sensor 22; safety cover 3; accommodating chamber 4; inner wall 41; preset edge 42; cavity opening 43. DETAILED DESCRIPTION

[0031] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. The advantages and features of the present invention will become more apparent from the following description. It should be noted that the accompanying drawings are in very simplified form and in non-precise proportions, and are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention.

[0032] The orientation or position relationship indicated by the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like are based on the orientation or position relationship shown in the drawings and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred mechanism or element must have a specific orientation, be constructed and operate in a specific orientation, and therefore should not be understood as limiting the present invention.

[0033] In the present invention, unless otherwise clearly specified and limited, the terms "installation", "connection", "fixation" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral one; it can be a mechanical connection, an electrical connection, or communication with each other; it can be a direct connection, or a connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0034] Furthermore, those skilled in the art may combine and associate different embodiments or examples and features of different embodiments or examples described in this specification without mutual contradiction.

[0035] In the prior art, the wafer-carrying assembly of the NXT model of the ASML lithography machine includes a large strong magnetic plate. When the strong magnetic plate is powered on, the wafer carrier can be suspended and rotated at high speed when the wafer is exposed. When the wafer carrier and the strong magnetic plate are repaired or maintained, it is necessary to use the operation panel to move them out of the accommodation chamber. Since the wafer carrier only covers part of the area on the strong magnetic plate, the area on the strong magnetic plate 12 that is not covered by the wafer carrier 11 is removed and exposed to the outside, which may cause damage to the operator or the material.

[0036] To prevent the strong magnetic plate from being exposed, ASML lithography machines are equipped with safety covers. When the wafer stage and the strong magnetic plate need to be maintained, the safety cover can be placed on the exposed area of ​​the strong magnetic plate to cover the strong magnetic plate and prevent the operator and materials from being damaged by strong magnetism. However, operators often forget to place the safety cover during actual operation, which poses a great safety hazard when maintaining the carrier components.

[0037] To solve the above problems, refer to Figure 1 and Figure 2 As shown, a preferred embodiment of the present application provides a wafer carrier device, including: a carrier component 1, a detection component 2, a safety cover 3 and a control unit. The carrier component 1 is placed in a receiving chamber 4 inside the wafer processing equipment. The detection component 2 includes a first position sensor 21 and a second position sensor 22. The first position sensor 21 is arranged on the inner wall 41 of the receiving chamber 4. The first position sensor 21 is used to detect the position of the carrier component 1. The control unit is used to prevent the carrier component 1 from moving after the first position sensor 21 detects the carrier component 1. The second position sensor 22 is arranged on the carrier component 1. The second position sensor 22 is used to detect the position of the safety cover 3. The control unit is used to release the blockage and allow the carrier component 1 to continue to move after the second position sensor 22 detects the safety cover 3.

[0038] In more detail, the first position sensor 21 can send a braking signal to the control unit after detecting the carrier component 1 (for example, the first position sensor 21 outputs a low level or a high level). After receiving the braking signal, the control unit prevents the carrier component 1 from moving out of the accommodating chamber 4, and then prompts the operator to place the safety cover 3 on the carrier component 1. The wafer carrier device also sets a second position sensor 22 at the placement position of the safety cover 3. After the safety cover 3 is placed in place, the second position sensor 22 can detect the safety cover 3 and send a driving signal to the control unit (for example, the second position sensor 22 outputs a high level or a low level). After receiving the driving signal, the control unit releases the position restriction on the carrier component 1 and allows the carrier component 1 to continue to move. Then the operator can move the carrier component 1 out of the accommodating chamber 4 for repair or maintenance through the operation panel.

[0039] The present application provides a wafer carrier device, which can limit the removal of the carrier component 1 through the first position sensor 21, and then prompt the operator to place a safety cover 3 on the carrier component 1. After the safety cover 3 is placed in place, the control unit can release the limit of the carrier component 1 and allow the carrier component 1 to be smoothly removed. Such a setting can prevent the operator from causing damage to the operator and materials due to failure to place the safety cover 3 on the carrier component, help the operator to safely and smoothly complete the repair or maintenance of the carrier component 1, and improve the safety and reliability of the operation of the wafer carrier device.

[0040] The present application does not limit the types of the first position sensor 21 and the second position sensor 22. The first position sensor 21 may include but is not limited to a photoelectric sensor or a limit switch; similarly, the second position sensor 22 may also include but is not limited to a photoelectric sensor or a limit switch.

[0041] Continue to refer to Figure 1 and Figure 2 In a preferred embodiment, the carrying assembly 1 includes a wafer carrier 11 and a strong magnetic plate 12. The wafer carrier 11 is placed on the strong magnetic plate 12 and covers a portion of the strong magnetic plate 12. The wafer carrier 11 is used to carry a wafer. The second position sensor 22 is fixed on the area where the strong magnetic plate 12 does not cover the wafer carrier 11. The safety cover 3 is used to be placed on the area where the strong magnetic plate 12 does not cover the wafer carrier 11 and covers at least a portion of the second position sensor 22.

[0042] In a preferred case, the first position sensor 21 is disposed on the inner wall 41 of the accommodating chamber 4 corresponding to the moving path of the carrying assembly 1 (including the position of the top wall, bottom wall and side wall of the accommodating chamber 4 corresponding to the carrying assembly 1). The moving path of the carrying assembly 1 here refers to the position of the inner wall 41 of the accommodating chamber 4 corresponding to the moving path of the carrying assembly 1 during the moving out process.

[0043] The specific layout position of the first position sensor 21 should satisfy the requirement that the first position sensor 21 can detect when the carrier assembly 1 (including the wafer carrier 11 and the strong magnetic plate 12) is stationary or moving. For example, the first position sensor 21 can be arranged at the position of the bottom wall or top wall of the corresponding accommodating chamber 4 of the carrier assembly 1, or the first position sensor 21 can also be arranged on the moving path of the carrier assembly 1. The present application does not limit the specific layout position of the first position sensor 21.

[0044] Continue to refer to Figure 2As a preferred solution, the first position sensor 21 is arranged on the top wall or bottom wall of the accommodating chamber 4 between the preset edge 42 and the cavity 43. The strong magnetic plate 12 includes a first outer wall 121 close to the cavity 43, that is, the first outer wall 121 is the outer wall of the strong magnetic plate 12 parallel to the cavity 43 of the accommodating chamber 4. The preset edge 42 is the position of the first outer wall 121 corresponding to the top wall or bottom wall of the accommodating chamber 4. In this way, when the wafer stage 11 or the strong magnetic plate 12 moves to the position of the first position sensor 21, the first position sensor 21 can detect the strong magnetic plate 12 and send a braking signal to the control unit. After receiving the braking signal, the control unit limits the movement of the wafer stage 11 and the strong magnetic plate 12 to prompt the operator to install the safety cover 3 on the strong magnetic plate 12. After the safety cover 3 is installed in place, the control unit can receive the driving signal sent by the second position sensor 22 and allow the wafer stage 11 and the strong magnetic plate 12 to continue to move, thereby realizing the protection of the operator and the material.

[0045] Reference Figure 1 and Figure 2 As shown, in a preferred example, the strong magnetic plate 12 also includes a second outer wall 122 perpendicular to the first outer wall 121, the length of the second outer wall 122 is approximately 1000 mm, and the horizontal distance w between the first position sensor 21 and the second outer wall 122 is 500 mm to 700 mm, which helps to improve the accuracy of detection by the first position sensor 21.

[0046] Of course, in other examples, the horizontal distance w between the first position sensor 21 and the second outer wall 122 may also be set to other values, as long as it is ensured that the first position sensor 21 can detect the strong magnetic plate 12 or the wafer stage 11 .

[0047] Continue to refer to Figure 1 and Figure 2 In a preferred case, the number of the second position sensors 22 is at least two, and the at least two second position sensors 22 are sequentially spaced in a direction parallel to the second outer wall 122. The control unit is used to allow the bearing assembly 1 to move after the at least two second position sensors 22 detect the safety cover 3. With this structure, the at least two second position sensors 22 can ensure that the safety cover 3 basically covers the designated area of ​​the strong magnetic plate 12, and ensure that the safety cover 3 is installed in place.

[0048] Continue to refer to Figure 1 and Figure 2, the number of second position sensors 22 is two groups, the number of second position sensors 22 in each group is at least two, and the number of safety covers 3 is also at least two. The two groups of second position sensors 22 are respectively arranged on both sides of the wafer stage 11. The control unit is used to allow the bearing assembly 1 to move after all the second position sensors 22 in any group have detected the safety cover 3. At this time, after all the second position sensors 22 in at least one group have detected the safety cover 3 (that is, after the safety cover 3 on one side of the wafer stage 11 is installed in place), the control unit can release the position restriction on the bearing assembly 1, and then the operator can drive the bearing assembly 1 to move out of the accommodating chamber 4 through the operation panel.

[0049] like Figure 1 and Figure 2 As shown, in this embodiment, all the second position sensors 22 in each group are preferably arranged in sequence and spaced apart in a direction parallel to the second outer wall 122, and the number of safety covers 3 is two, and each safety cover 3 is used to cover two second position sensors 22 in each group.

[0050] In another example, all the second position sensors 22 in each group may also be staggered in a direction parallel to the first outer wall 121 or the second outer wall 122, and the number of safety covers 3 may be set as needed. Specifically, the safety cover 3 may cover one or more second position sensors 22 as needed.

[0051] Reference Figure 3 As shown, a preferred embodiment of the present application provides an operating method of a wafer carrier, including any one of the wafer carriers described above, and the operating method includes:

[0052] S01: driving the carrying assembly 1 to move toward the cavity opening 43 of the accommodating chamber 4 through the control unit.

[0053] S02: Determine whether the first position sensor 21 detects the bearing assembly 1.

[0054] S03: If the first position sensor 21 detects the load-bearing assembly 1, the first position sensor 21 sends a braking signal to the control unit.

[0055] S04: After receiving the braking signal, the control unit stops the bearing assembly 1 from moving. S05: Determine whether the second position sensor 22 detects the safety cover 3.

[0056] S06: If the second position sensor 22 detects the safety cover 3, the second position sensor 22 sends a driving signal to the control unit.

[0057] S07: After receiving the driving signal, the control unit releases the blockage and allows the bearing assembly 1 to continue moving.

[0058] It should be noted that the operator can place the safety cover 3 on the bearing assembly 1 before, during or after the bearing assembly 1 moves (i.e., after the control unit receives the braking signal and prevents the bearing assembly 1 from moving). After the safety cover 3 is placed, it can be detected by the second position sensor 22.

[0059] The present application provides an operating method of a wafer carrier, which can limit the removal of the carrier assembly 1 through the first position sensor 21, and then prompt the operator to install the safety cover 3 on the carrier assembly 1. After the safety cover 3 is installed in place, the control unit can release the limit of the carrier assembly 1 and allow the carrier assembly 1 to be smoothly removed. Then the operator can move the carrier assembly 1 out of the accommodating chamber 4 for repair or maintenance through the operation panel, thereby preventing the operator from not placing the safety cover 3 on the carrier assembly 1 and causing damage to the operator and materials, thereby improving the safety and reliability of the operation of the wafer carrier.

[0060] As a preferred embodiment, in S07, the step of releasing the blockage and allowing the bearing assembly 1 to continue to move after the control unit receives the driving signal includes:

[0061] If the control unit receives the driving signals sent by all the second position sensors 22 in each group (for example, all the second position sensors 22 in each group output high level or low level), the control unit releases the blockage and allows the bearing assembly 1 to continue to move. At this time, the placement position of the safety cover 3 can be detected by multiple second position sensors 22 to ensure that the safety cover 3 can be installed in place.

[0062] The present application has no particular restrictions on the type of control unit, which may be hardware that performs logical operations, such as a single-chip microcomputer, a microprocessor, a programmable logic controller (PLC) or a field-programmable gate array (FPGA), or a software program, functional module, function, object library or dynamic link library that implements the above functions based on hardware. Those skilled in the art should know how to specifically implement the communication between the control unit and other devices.

[0063] In summary, the present invention provides a wafer carrier device and an operating method thereof, wherein the device can limit the removal of the carrier component 1 through the first position sensor 21, and then prompt the operator to place a safety cover 3 on the carrier component 1. After the safety cover 3 is placed in place, the control unit can release the limit of the carrier component 1 and allow the carrier component 1 to be smoothly removed. Such a setting can prevent the operator from causing damage to the operator and materials due to failure to place the safety cover 3 on the carrier component 1, help the operator to safely and smoothly complete the repair or maintenance of the carrier component 1, and improve the safety and reliability of the operation of the wafer carrier device.

[0064] The above description is only a description of the preferred embodiments of the present invention, and is not intended to limit the scope of the present invention. Any changes or modifications made by a person skilled in the art in the field of the present invention based on the above disclosure shall fall within the protection scope of the present invention.

Claims

1. A wafer carrying device, characterized in that: include: A carrying component, a detection component, a safety cover and a control unit, wherein the carrying component is placed in a containing chamber inside the wafer processing equipment; The detection assembly includes a first position sensor and a second position sensor, the first position sensor is arranged on the inner wall of the accommodating chamber, the first position sensor is used to detect the position of the bearing assembly, and the control unit is used to prevent the bearing assembly from moving after the first position sensor detects the bearing assembly; The second position sensor is arranged on the bearing assembly, and is used to detect the position of the safety cover. The control unit is used to release the blockage and allow the bearing assembly to continue to move after the second position sensor detects the safety cover.

2. The wafer carrier device according to claim 1, characterized in that: The supporting assembly includes a wafer carrier and a strong magnetic plate, the wafer carrier is placed on the strong magnetic plate and covers a partial area of ​​the strong magnetic plate; the second position sensor is fixed on the area of ​​the wafer carrier not covered by the strong magnetic plate; the safety cover is used to be placed on the area of ​​the wafer carrier not covered by the strong magnetic plate and cover at least a portion of the second position sensor.

3. The wafer carrier device according to claim 2, characterized in that: The first position sensor is arranged on an inner wall of the accommodating chamber corresponding to a moving path of the bearing assembly.

4. The wafer carrier device according to claim 3, characterized in that: The strong magnetic plate includes a first outer wall close to the cavity opening of the accommodating chamber; the first position sensor is arranged on the top wall or bottom wall of the accommodating chamber between a preset edge and the cavity opening, and the preset edge is the position of the first outer wall corresponding to the top wall or bottom wall of the accommodating chamber.

5. The wafer carrier device according to claim 4, characterized in that: The strong magnetic plate further includes a second outer wall perpendicular to the first outer wall, the length of the second outer wall is 1000 mm, and the horizontal distance between the first position sensor and the second outer wall is 500 mm to 700 mm.

6. The wafer carrier device according to claim 5, characterized in that: The number of the second position sensors is at least two, and at least two of the second position sensors are arranged in sequence and spaced apart in a direction parallel to the second outer wall; the control unit is used to allow the bearing assembly to move after at least two of the second position sensors detect the safety cover.

7. The wafer carrier device according to any one of claims 2 to 6, characterized in that: The number of the second position sensors is two groups, the number of the second position sensors in each group is at least two, and the number of the safety covers is also at least two; the two groups of the second position sensors are respectively arranged on both sides of the wafer carrier; the control unit is used to allow the supporting assembly to move after all the second position sensors in any group detect the safety cover.

8. The wafer carrier device according to any one of claims 1 to 6, characterized in that: The first position sensor and / or the second position sensor is configured as a photoelectric sensor or a limit switch.

9. A method for operating a wafer carrier, characterized in that: The wafer carrier device according to any one of claims 1 to 8, wherein the operating method comprises: S01: driving the carrying assembly to move toward the opening of the accommodating chamber by the control unit; S02: Determine whether the first position sensor detects the bearing assembly; S03: If the first position sensor detects the load-bearing assembly, the first position sensor sends a braking signal to the control unit; S04: the control unit stops the bearing assembly from moving after receiving the braking signal; S05: Determine whether the second position sensor detects a safety cover; S06: If the second position sensor detects the safety cover, the second position sensor sends a driving signal to the control unit; S07: After receiving the driving signal, the control unit releases the blockage and allows the bearing assembly to continue moving.

10. The method for operating the wafer carrier according to claim 9, wherein: The bearing assembly includes a wafer stage and a strong magnetic plate, the wafer stage is placed on the strong magnetic plate and covers a partial area of ​​the strong magnetic plate; the number of the second position sensors is two groups, the number of the second position sensors in each group is at least two, and the two groups of the second position sensors are respectively arranged on the strong magnetic plates on both sides of the wafer stage; In S07, the step of releasing the blocking and allowing the bearing assembly to continue to move after the control unit receives the driving signal includes: If the control unit receives driving signals sent by all the second position sensors in each group, the control unit releases the blockage and allows the bearing assembly to continue moving.

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