JP2012209361A - Center alignment device for work - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an alignment device capable of aligning the center position of a work with the center of a rotary shaft during rotating operation without stopping the rotating operation.SOLUTION: A center alignment device for a work includes a placement table 21 on which a work W is placed; an XY stage 22 which is arranged below the placement table 21 and moves the placement table 21 in two orthogonal directions on a plane; an X-axial driving part 6 and a Y-axial driving part 7 which drive the XY stage 22; a rotary shaft which supports the XY stage rotatably from below and is aligned with the origin of the XY stage; a rotary shaft driving part 8 which drives and rotates the rotary shaft; and edge position detection means 3 for detecting an edge position of the work W. A control part 4 calculates a movement quantity of the XY stage 22 needed to align the center position of the work W with the center of the rotary shaft based upon edge position information and rotational angle information while driving and rotating the rotary shaft, and actuates one of the X-axial driving part 6 and Y-axial driving part 7 based upon the movement quantity.

Description

  The present invention relates to a work center alignment apparatus for aligning the center position of a work having an outer shape, such as a wafer, with the center of a rotation axis of a rotary stage.

  For example, when a workpiece having a substantially disk shape, such as a wafer accommodated in a storage container such as FOUP, is loaded into the processing apparatus, or a workpiece that has been processed by the processing apparatus is loaded into the storage container, It is required to carry in all the workpieces positioned in a predetermined posture. Therefore, conventionally, for example, a workpiece is placed on a rotating stage while the workpiece is being transferred from a container such as FOUP to a semiconductor manufacturing apparatus, and the edge position of the workpiece is detected by a sensor while rotating the rotating stage in that state. A mode is known in which the center position of the workpiece is calculated based on the detected edge position (for example, Patent Document 1 and Patent Document 2).

  In Patent Document 1, an edge position is detected by a sensor while rotating a rotary stage around a rotation axis while a work is placed, and the center position of the work and the rotation axis calculated based on the detected edge position are detected. Disclosed is a mode in which the XY stage is appropriately moved in two directions orthogonal to each other in a plane in a state where the rotation of the rotary stage is stopped in accordance with the amount of deviation from the center so that the center position of the wafer coincides with the center of the rotation axis. Has been.

  In Patent Document 2, the center position of the workpiece is calculated based on the edge position detected by the sensor while rotating the rotary stage around the rotation axis while the workpiece is placed. By correcting the access position of the workpiece transfer arm with respect to the workpiece in a state where the rotation of the rotary stage is stopped according to the amount of deviation from the center of the rotation axis, the center position of the wafer in the storage container or the processing apparatus is determined. An aspect configured to be kept in order is disclosed.

Japanese Patent Laid-Open No. 09-8105 Japanese Patent No. 3748940

  However, in any of the above-described aspects, in order to calculate the center position of the wafer, the work is rotated once on the rotary stage, and all edge positions in the process or edge positions at predetermined positions (for each predetermined rotation angle) are obtained. Since detection is an essential condition, it is naturally impossible to make the center position of the workpiece coincide with the center of the rotation axis while the workpiece is rotated once.

  As described above, in the conventional mode, it is necessary to secure a time for rotating the workpiece at least once for detecting the edge position, thereby realizing a higher-speed alignment process, and thus performing a desired process on the workpiece. It is desired to shorten the entire time required for application.

  The present invention has been made paying attention to such a problem, and the main purpose of the present invention is to detect the edge position by rotating the workpiece and to detect the center position of the workpiece during the rotation operation without stopping the rotation operation. It is an object of the present invention to provide an alignment device that can adjust the center of the rotation axis to the center of the rotation axis.

  That is, the workpiece alignment apparatus according to the present invention includes a mounting table on which a workpiece having a circumferential shape or a substantially circumferential outer shape is placed, and a mounting table that is disposed below the mounting table and is orthogonal to the mounting table on a plane. An XY stage that moves in the X-axis direction and the Y-axis direction, a rotational axis that supports the XY stage rotatably from below, and that coincides with the origin of the XY stage, and an edge position that detects the edge position of the workpiece placed on the mounting table And a detecting means.

  As described above, in the present invention, the XY stage and the mounting table are configured to be rotatable around a common rotation axis, and the edge position detection unit can detect the edge position of the workpiece mounted on the mounting table. Yes. Here, as the edge position detecting means, an optical device such as a sensor or a camera can be cited. In addition, the work in the present invention may be any work as long as it has a “circumferential shape or a substantially circumferential outer shape”. It also includes a workpiece that can be regarded as having a shape of a shape. Examples of the workpiece include wafers, recording disks such as CDs and DVDs, and mechanical parts such as diaphragms and end plates.

  The workpiece alignment apparatus according to the present invention further includes an X-axis drive unit that drives the XY stage in the X-axis direction, a Y-axis drive unit that drives the XY stage in the Y-axis direction, and a rotary shaft that rotates. The rotation axis drive unit to be input, the edge position information on the edge position from the edge position detection means, the rotation angle information on the rotation angle of the rotation axis from the rotation axis drive unit, and these information (edge position information and rotation angle information) are input. And a control unit that controls the operation of the X-axis drive unit and the Y-axis drive unit, and the control unit is configured to input edge position information and the rotation position when the rotary shaft is driven to rotate by the rotary shaft drive unit. Based on the rotation angle information, the amount of movement of the XY stage required to make the center position of the workpiece coincide with the center of the rotation axis is calculated, and based on this amount of movement, the amount of X-axis drive unit or Y-axis drive unit is reduced. It is characterized in that Kutomo in which actuate either.

  With such a workpiece alignment device, while rotating the mounting table and the XY stage around the rotation axis in a state where the workpiece is mounted on the mounting table, while detecting the edge position of the workpiece by the edge position detection means, According to the movement amount of the XY stage calculated based on edge position information and rotation angle information input to the control unit in real time, at least one of the X-axis drive unit and the Y-axis drive unit is operated by the control unit. Since it comprises, the center position can be match | combined with the center of a rotating shaft, rotating a workpiece | work. Therefore, compared with the conventional mode in which it is necessary to secure at least a time for one rotation of the workpiece for detecting the edge position, the processing for aligning the center position of the workpiece with the center of the rotation axis (alignment processing). The overall time required for performing a desired process on the work can be shortened. Here, in the present invention, when only the X-axis drive unit is operated, only when the Y-axis drive unit is operated, and both the X-axis drive unit and the Y-axis drive unit are operated according to the movement amount calculated by the control unit. May be activated.

  Also, with the workpiece alignment apparatus according to the present invention, it is possible to match the center position of the workpiece with the center of the rotation axis while rotating the workpiece. When carrying to the next process, the access position of the arm with respect to the workpiece can be fixed. Therefore, the alignment apparatus according to the present invention corrects the access position of the workpiece transfer arm with respect to the workpiece as compared with the mode of correcting the access position of the workpiece transfer arm with respect to the workpiece while the rotation of the rotary stage is stopped. This eliminates the need for the processing to be performed, and can shorten the time while simplifying the structure and reducing the price.

  According to the present invention, by adopting a novel technical idea that the mounting table is arranged on the XY stage and the mounting table and the XY stage are rotated around a common rotation axis, the workpiece on the mounting table is moved. While rotating, the center position of the rotating workpiece can be aligned with the center of the rotation axis based on the edge position information and the rotation angle information, and the time required for the alignment process can be shortened.

BRIEF DESCRIPTION OF THE DRAWINGS The whole structure schematic diagram of the center alignment apparatus of the workpiece | work which concerns on one Embodiment of this invention. The A direction arrow directional view of FIG. The figure which shows the reference | standard data in the same embodiment. The figure which shows typically the graph corresponding to FIG. 3 when the center position of a wafer does not correspond to the rotating shaft center in the embodiment. The figure which shows typically the graph corresponding to FIG. 3 at the time of performing the process which makes the center position of a wafer correspond to a rotating shaft center by the center alignment apparatus of the workpiece | work which concerns on the same embodiment. The figure which shows the process sequence of the center alignment apparatus of the workpiece | work which concerns on the same embodiment.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  A workpiece center alignment apparatus 1 (also referred to as an alignment apparatus. Hereinafter, for convenience of explanation, it may be referred to as “this apparatus 1”), the center position of a wafer W as a workpiece is set on a rotary stage. 1 and FIG. 2, a rotary stage 2 that can be rotated by placing a wafer W thereon, and a wafer provided above the rotary stage 2 at predetermined equal angular intervals. An edge position detection unit 3 capable of detecting the edge position of W and a control unit 4 for controlling the operations of the rotary stage 2 and the edge position detection unit 3 are provided.

  The rotary stage 2 includes a mounting table 21 on which the wafer W is placed, and an XY stage 22 that is disposed below the mounting table 21 and moves the mounting table 21 in the X-axis direction and the Y-axis direction orthogonal to each other on a plane. The mounting table 21 and the XY stage 22 support the XY stage 22 so as to be rotatable from below, and rotate integrally around a rotating shaft 5 that coincides with the origin of the XY stage 22. That is, in the present embodiment, the XY stage 22 itself rotates around the rotation axis 5, and the mounting table 21 disposed above the XY stage 22 is configured to rotate around the rotation axis 5 together with the XY stage 22. . The rotation center of the rotary stage 2 coincides with the center of the rotary shaft 5.

  The mounting table 21 only needs to have a flat upper surface, and in the present embodiment, the mounting table 21 has a substantially disk shape. The XY stage 22 includes an X-axis slider 22A that is slidable in the X-axis direction and a Y-axis slider 22B that is slidable in the Y-axis direction.

  The edge position detection means 3 is configured using, for example, a sensor, and is arranged at a position where the edge of the wafer W placed on the mounting table 21 can be detected. In the present embodiment, information (edge position information) related to the edge position detected by the edge position detecting means 3 is provided (output) to the control unit 4.

  The apparatus 1 also includes an X-axis drive unit 6 that drives the XY stage 22 in the X-axis direction, a Y-axis drive unit 7 that drives the XY stage 22 in the Y-axis direction, and a rotary shaft that drives the rotary shaft 5 to rotate. The drive unit 8 is provided, and the operation of each of these drive units (the X-axis drive unit 6, the Y-axis drive unit 7, and the rotary shaft drive unit 8) is controlled by the control unit 4.

  The X-axis drive unit 6 and the Y-axis drive unit 7 are configured using, for example, a linear motor. A ball screw mechanism may be applied instead of the linear motor. In the present embodiment, the X-axis drive unit 6 and the X-axis slider 22A are connected via a slip ring (not shown), and the Y-axis drive unit 7 and the Y-axis slider 22B are connected via a slip ring (not shown). Connected. As a result, even when the rotating shaft 5 is continuously rotated in one direction, the respective axis driving units (X-axis driving unit 6, Y-axis driving unit 7) and the XY stage 22 (X-axis sliders 22A, Y) Drive from each axis drive unit (X-axis drive unit 6, Y-axis drive unit 7) to the XY stage 22 (X-axis slider 22A, Y-axis slider 22B) without disconnection from the axis slider 22B) Electric power and electric signals can be transmitted appropriately.

  The rotary shaft drive unit 8 controls, for example, the rotary operation of the rotary shaft 5 by operating a rotary motor M having the rotary shaft 5. In this embodiment, the rotary shaft is rotated by the rotary shaft drive unit 8. 5 (rotation angle information) is provided (output) to the control unit 4.

  The control unit 4 performs control and processing related to the alignment between the rotation center position of the wafer W and the rotation center position of the rotation stage 2 (center of the rotation shaft 5). The control unit 4 is provided in a controller C composed of a general-purpose personal computer or the like having a calculation function, a communication function, etc., and according to a program stored in an external storage device such as an internal memory or HDD provided in the controller C. 1, at least functions as an XY stage movement amount calculation means 41 and an XY stage correction means 42 as shown in FIG. It is.

  The XY stage movement amount calculating means 41 determines the center position of the wafer W as the center of the rotation shaft 5 based on the input edge position information and rotation angle information in a state where the rotation shaft 5 is rotationally driven by the rotation shaft driving unit 8. The amount of movement of the XY stage 22 required to match the above is calculated. Here, the control unit 4 provides the rotation angle information and the edge position information when the rotation shaft 5 is rotated in a state where the center position of the wafer W placed on the rotation stage 2 and the center of the rotation shaft 5 coincide with each other. As shown in FIG. 3, data (reference data) representing the relationship with XY is stored. As can be understood from the figure, when the rotation shaft 5 is rotated in a state where the center position of the wafer W placed on the rotation stage 2 and the center of the rotation shaft 5 coincide with each other, any rotation angle is obtained. However, the edge position of the wafer W is always constant. A straight line that is a set of edge positions (reference edge positions) in the reference data is defined as a horizontal reference line L. The reference data is obtained when a circular wafer having no notches or orientation flats formed in the edge portion is applied as the wafer W.

  The edge position of the wafer W placed on the rotary stage 2 and the rotation angle of the rotary shaft 5 can also be expressed on the XY coordinates similar to the reference data, and the center position of the wafer W placed on the rotary stage 2 Is not coincident with the center of the rotary shaft 5, a line that is a set of edge positions of the wafer W on the rotary stage 2 appears as a curve as shown in FIG. In the figure, a region I in which a curve i clearly different from the other parts appears means that the notch Wn formed at the edge of the wafer W is detected by the edge position detecting means 3.

  The XY stage movement amount calculation means 41 of the present embodiment is displayed on the same XY coordinates as the reference data based on the edge position information and the rotation angle information input from the edge position detection means 3 and the rotation axis drive unit 8. Depending on the difference (vertical distance t in FIG. 4) between the edge position of the wafer W on the rotation stage 2 and the reference edge position (a certain point on the horizontal reference line L) at a certain rotation angle, the rotation axis 5 The amount (movement amount) by which the wafer W is moved in the direction of the rotation center is calculated. Specifically, the XY stage movement amount calculation means 41 grasps the rotation angle from the rotation angle information, and the XY stage so that the combined movement amount in the X axis direction and the Y axis direction at the rotation angle faces the center of the rotation axis 5. The movement amount of 22 is calculated. For example, if the rotation angle of the rotary shaft 5 is 90 degrees, the Y-axis drive unit 7 moves the Y-axis slider 22B by the difference between the edge position of the wafer W on the rotary stage 2 and the reference edge position. Calculate as If the rotation angle of the rotary shaft 5 is 45 degrees, the X-axis drive unit 6 causes the X-axis slider 22 </ b> A to be set to “½ × √” as the difference between the edge position of the wafer W on the rotary stage 2 and the reference edge position. 2 ”and the difference between the edge position of the wafer W on the rotary stage 2 and the reference edge position is set to“ 1/2 × √2 ”. A value to be moved by the multiplied amount is calculated as a movement amount.

  The XY stage correction unit 42 operates at least one of the X-axis drive unit 6 and the Y-axis drive unit 7 based on the movement amount calculated by the XY stage movement amount calculation unit 41 to move the XY stage 22 in the surface direction (X (Axial direction, Y-axis direction) with the horizontal posture maintained. In the present embodiment, the XY stage correction unit 42 moves only the X-axis slider 22A, moves only the Y-axis slider 22B, or moves the X-axis slider according to the movement amount calculated by the XY stage movement amount calculation unit 41. There are cases where both 22A and the Y-axis slider 22B are moved. The XY stage correction unit 42 controls the operation of the X-axis drive unit 6 and the Y-axis drive unit 7 based on the correction value of the XY stage 22 based on the movement amount calculated by the XY stage movement amount calculation unit 41.

  Next, the operation procedure and operation of the workpiece center alignment apparatus 1 according to the present embodiment will be described with reference to FIGS. 5 and 6.

  First, in a state in which a wafer W having a notch Wn formed at a part of the edge is set on the mounting table 21 of the rotary stage 2, the apparatus 1 rotates the rotary shaft 5 by the rotary shaft driving unit 8 to rotate the rotary stage 2. The edge position of the rotating wafer W is detected by the edge position detecting means 3. In the present apparatus 1, the XY stage movement amount calculation means 41 is based on the edge position information input from the edge position detection means 3 and the rotation angle information input from the rotation shaft drive unit 8. The amount of movement of the XY stage 22 required to make the center position coincide with the center of the rotary shaft 5 is calculated (XY stage movement amount calculation step S1, see FIG. 6). For example, as shown in FIG. 5, when the difference between the edge position of the wafer W on the rotary stage 2 and the reference edge position of the reference data is “α” when the rotation angle of the rotating shaft 5 is 90 degrees (case 1). The XY stage movement amount calculation means 41 calculates, as the movement amount, a value by which the Y axis drive unit 7 moves the Y axis slider 22B by the difference “α” between the edge position of the wafer W on the rotation stage 2 and the reference edge position. To do. If the difference between the edge position of the wafer W on the rotary stage 2 and the reference edge position of the reference data when the rotation angle of the rotary shaft 5 is 45 degrees is “β” (case 2), the XY stage movement amount calculating means 41 is a value “β (1/1/2) obtained by multiplying the difference β between the edge position of the wafer W on the rotary stage 2 and the reference edge position by the X-axis drive unit 6 by“ 1/2 × √2 ”. 2 × √2) ”and a value obtained by multiplying the difference β between the edge position of the wafer W on the rotary stage 2 and the reference edge position by the Y-axis drive unit 7 by“ 1/2 × √2 ”. “Β (½ × √2)” is calculated as the movement amount of the X-axis slider 22A and the movement amount of the Y-axis slider 22B, respectively.

  Next, in the present apparatus 1, the control unit 4 uses the calculated movement amount as a correction value, and operates at least one of the X-axis drive unit 6 and the Y-axis drive unit 7 based on the correction value, thereby XY stage. 21 is corrected (XY stage correction step S2, see FIG. 6). For example, in case 1, the XY stage correction unit 42 of the control unit 4 moves the Y-axis slider 22 </ b> B by the movement amount “α” corresponding to the correction value by the Y-axis drive unit 7. Further, in case 2, the XY stage correction means 42 of the control unit 4 moves the X-axis slider 22A by the movement amount “β (1/2 × √2)” corresponding to the correction value by the X-axis drive unit 6. At the same time, the Y-axis drive unit 7 moves the Y-axis slider 22B by the movement amount “β (1/2 × √2)”.

  Through the above processing procedure, the apparatus 1 moves the XY stage 22 by a predetermined amount in at least one of the X-axis direction and the Y-axis direction, and is mounted on the XY stage 22 supported by the XY stage 22 and rotating integrally with the XY stage 22. The center position of the wafer W placed on the mounting table 21 and the center of the rotating shaft 5 can be matched.

  Here, in order to perform the XY stage movement amount step S1 and the XY stage correction step S2 in a state where the rotary stage 2 is rotated, the present apparatus 1 is a process of rotating the rotary stage 2 once as shown in FIG. The edge position of the wafer W on the rotary stage 2 can be brought close to the reference edge position, and at least when the rotary stage 2 has completed one rotation, the edge position of the wafer W on the rotary stage 2 is made to coincide with the reference edge position. Can do.

  As described above, the apparatus 1 rotates the mounting table 21 and the XY stage 22 around the rotation axis 5 in a state where the wafer W is mounted on the mounting table 21, and the edge position of the wafer W is detected by the edge position detection unit 3. While detecting, according to the movement amount of the XY stage 22 calculated based on the edge position information and the rotation angle information input to the control unit 4 in real time, the control unit 4 controls the X-axis drive unit 6 or the Y-axis drive unit 7. Since at least one of them is configured to operate, the center position of the wafer W can be adjusted to the center of the rotation shaft 5 while rotating the wafer W. Accordingly, the center position of the wafer W is rotated as compared with the conventional method in which the rotation stage is temporarily stopped after being rotated once and then the rotation stage is moved in a predetermined direction based on the edge position information detected during the rotation. It is possible to reduce the time required for the process (positioning process) for matching with the center of the axis 5, and to reduce the entire time required for performing a desired process on the wafer W.

  Further, in the alignment apparatus 1 according to the present embodiment, since the center position of the wafer W can be matched with the center of the rotation shaft 5 in real time while rotating, the wafer W in a state where the alignment process has been completed can be obtained. For example, when an arm is transferred to the next process, the access position of a transfer arm (not shown) with respect to the wafer W can be fixed. Therefore, the present apparatus 1 is configured so that the transfer arm for the wafer W is compared with a mode in which the access position of the transfer arm for the wafer is corrected according to the calculated predetermined shift amount in a state where the rotation of the rotary stage is stopped. The process of correcting the access position is not required, and the structure can be simplified and the price can be reduced.

  Furthermore, as described above, the amount of movement of the XY stage 22 required to make the center position of the wafer W coincide with the center of the rotation axis 5 is the difference between the actual edge position of the wafer W and the reference edge position at a certain rotation angle. It is possible to use an inexpensive arithmetic processing device that is not so high in processing capacity as compared with an aspect that requires high-level and complicated arithmetic processing. Cost can also be reduced.

  Further, when the center position of the wafer W in which the notch Wn is formed in a part of the edge is made to coincide with the center of the rotating shaft 5, the region where the notch Wn is formed in the wafer W is the edge as shown in FIGS. A curve i, which is a set of edge positions based on edge position information while passing through the edge detection points of the position detection means 3, passes through the edge detection points of the edge position detection means 3 when an edge that does not form the notch Wn. Compared with a curve that is a set of edge positions based on edge position information during the process, the line is unique. Focusing on this point, the control unit 4 determines the time point I at which a specific curve i appears based on the input edge position information and rotation angle information as the edge position of the wafer W where the notch Wn is formed. If it is assumed that the edge detection point of the detection means 3 has passed and the rotation drive shaft 8 rotates the rotation drive shaft by a predetermined angle based on the rotation angle at this time, the wafer on the mounting table 21 It can be provided to the next process in a state where W is set in a predetermined direction. Further, if the wafer W is set on the mounting table 21 so that the notch Wn portion is close to the edge position detecting means 3, and the alignment process is performed, the rotation angle for detecting the notch Wn portion. Can be reduced.

  In addition, this invention is not limited to embodiment mentioned above. For example, a wafer in which notches such as notches and orientation flats are not formed, or a recording disk such as a CD or a DVD, or a mechanical part such as a diaphragm or a mirror plate may be applied as a workpiece.

  In the embodiment described above, the aspect in which the slip ring is disposed between the X-axis drive unit and the X-axis slider and between the Y-axis drive unit and the Y-axis slider is illustrated. You may connect with a lead wire. In this case, in order to avoid a situation where the lead wire is entangled when the rotary shaft is continuously rotated in one direction or an excessive force (tensile force) acts on the lead wire, It is desirable to reverse the rotation direction every time the is rotated by a predetermined angle (for example, every rotation or every predetermined number of rotations).

  Further, when the center position of the wafer does not coincide with the rotation axis center even after the XY stage is moved in accordance with a predetermined movement amount, that is, on the XY coordinates associated with the wafer edge position information and the rotation angle information. When the event that the edge position of the wafer on the mounting table does not match the preset reference edge position is confirmed, the above-described event disappears completely from the above-described XY stage movement amount calculation step and XY stage correction step. Repeat until it almost disappears.

  The edge position detecting means may detect the edge position of the workpiece using a camera or a displacement meter.

  The calculation program in the XY stage movement amount calculation means may be other than the calculation program described in the above embodiment.

  In addition, the specific configuration of each part is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 1 ... Center position alignment apparatus 21 ... Mounting stage 22 ... XY stage 3 ... Edge position detection means 4 ... Control part 5 ... Rotating shaft 6 ... X-axis drive part 7 ... Y-axis drive part 8 ... Rotation axis drive part W ... Workpiece (wafer)

Claims (1)

A mounting table on which a workpiece having a circumferential shape or a substantially circumferential outer shape is placed;
An XY stage disposed below the mounting table and moving the mounting table in the X-axis direction and the Y-axis direction orthogonal to each other on a plane;
An X-axis drive unit that drives the XY stage in the X-axis direction;
A Y-axis drive unit that drives the XY stage in the Y-axis direction;
A rotating shaft that rotatably supports the XY stage from below and coincides with the origin of the XY stage;
A rotating shaft driving unit for rotating the rotating shaft;
Edge position detecting means for detecting the edge position of the workpiece;
The operation of the X-axis drive unit and the Y-axis drive unit in response to the input of the edge position information related to the edge position from the edge position detection means and the rotation angle information related to the rotation angle of the rotation shaft from the rotation shaft drive unit And a control unit for controlling
In order to make the center position of the workpiece coincide with the center of the rotation axis based on the input edge position information and the rotation angle information in a state where the control section rotates the rotation axis by the rotation axis driving section. A workpiece center alignment apparatus that calculates a required amount of movement of the XY stage and operates at least one of the X-axis drive unit or the Y-axis drive unit based on the amount of movement. .

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