JP2021087982A - Adjustment method for laser processing apparatus - Google Patents

Abstract

To provide an adjustment method for a laser processing apparatus, by which the center of a light condenser and the center of a laser beam emitted from a spatial light modulator can be appropriately made to coincide with each other.SOLUTION: An adjustment method for a laser processing apparatus includes: emitting a laser beam LB1 to an upper surface 10a of an inspection plate 10 so as to position a first condensing point P1 and capturing an image by use of imaging means 47; finding X coordinate and Y coordinate positions of the first condensing point P1 displayed by display means 50; emitting a laser beam LB1 to the upper surface 10a of the inspection plate 10 by use of Z-axis adjustment means 45A so as to position a second condensing point P2 and capturing an image by use of the imaging means 47; finding X coordinate and Y coordinate positions of the second condensing point P2 displayed by the display means 50; and making an optical axis of a spatial light modulator 43 coincide with a center of a light condenser 45 by adjusting the optical axis of the spatial light modulator 43 such that the X coordinate and Y coordinate positions of the first condensing point P1 and the X coordinate and Y coordinate positions of the second condensing point P2 coincide with each other.SELECTED DRAWING: Figure 2

Description

The present invention relates to a method for adjusting a laser processing apparatus having a spatial light modulator in an optical system.

A wafer in which a plurality of devices such as ICs and LSIs are partitioned by a planned division line and formed on the surface is divided into individual device chips by a dicing device and a laser processing device, and is used for electric devices such as mobile phones and personal computers. ..

The laser processing apparatus relatively processes and feeds the holding means for holding the workpiece, the laser beam irradiating means for irradiating the workpiece held by the holding means with the laser beam, and the holding means and the laser beam irradiating means. The laser beam irradiating means is arranged between an oscillator that oscillates a laser beam, a condenser that collects the laser beam oscillated by the oscillator, and the oscillator and the condenser. It is composed of a mask that shapes the spot shape or an optical system that generates two or more focusing points (see, for example, Patent Documents 1 and 2).

Spatial light modulators (transmission type (LC), reflection type (LCOS)) are known as alternatives to the above-mentioned optical system that generates two or more masks and focusing points, and the spatial light modulator is used. By doing so, it is possible to freely adjust the focusing characteristics of the laser beam, such as shaping the spot shape of the laser beam and generating two or more focusing points formed by the condenser (for example, Patent Documents). See 3).

Japanese Unexamined Patent Publication No. 2006-319198 Japanese Unexamined Patent Publication No. 2005-028438 International Publication No. 2008/088043

When the above-mentioned spatial light modulator is used, if the center of the condenser lens constituting the condenser and the optical axis of the light beam emitted from the spatial light modulator are deviated, the laser beam is focused at a desired position. There is a problem that the points cannot be positioned, and in particular, when processing by positioning the condensing points at a plurality of positions, high-precision processing becomes difficult.

The present invention has been made in view of the above facts, and its main technical problem is a laser processing apparatus capable of appropriately aligning the center of a condenser with the optical axis of a laser beam emitted from a spatial light modulator. Is to provide a method of adjustment.

In order to solve the above-mentioned main technical problem, according to the present invention, a holding means provided with a holding surface for holding a work piece defined in the X-axis direction and the Y-axis direction orthogonal to the X-axis direction, and the said A laser beam irradiating means for irradiating a workpiece held on the holding surface with a laser beam, an imaging means for capturing the light reflected by the workpiece held on the holding surface, and an image captured by the imaging means are displayed. The laser beam irradiating means comprises a display means, and the laser beam irradiating means reflects the laser beam and guides the laser beam in the Z-axis direction orthogonal to the X-axis direction and the Y-axis direction, and is used in the workpiece. A splitter that transmits reflected light, an attenuator that is placed between the oscillator and the splitter to adjust the output of the laser beam oscillated by the oscillator, and a collection of laser beams that are placed between the attenuator and the splitter. A spatial light modulator that adjusts the optical characteristics, an operating means for operating the spatial optical modulator, a concentrator that condenses the laser beam reflected by the splitter onto a work piece held on the holding surface, and the like. It is an adjustment method of a laser processing apparatus composed of at least a Z-axis adjusting means for adjusting the position of a condensing point of a laser beam by relatively approaching and separating the concentrator and the holding means in the Z-axis direction. Then, the operating means is operated so that the spatial light modulator forms two focusing points, a first focusing point and a second focusing point of the laser beam in the Z-axis direction, and the Z-axis adjustment is performed. The first condensing point of the laser beam is positioned and irradiated on the upper surface of the inspection plate held on the holding surface by the means, the image is taken by the imaging means, and the first condensing point displayed on the display means. The X-coordinate and Y-coordinate positions are obtained, the second condensing point of the laser beam is positioned and irradiated on the upper surface of the inspection plate by the Z-axis adjusting means, the image is taken by the imaging means, and the display is displayed on the display means. The X-coordinate and Y-coordinate positions of the second condensing point are obtained, and the X-coordinate and Y-coordinate positions of the first condensing point coincide with the X-coordinate and Y-coordinate positions of the second condensing point. By adjusting the position of the optical axis of the spatial optical modulator as described above, a method for adjusting the laser processing apparatus is provided, in which the optical axis of the spatial optical modulator is aligned with the center of the condenser.

The adjustment method of the laser processing apparatus of the present invention uses an operating means so that the spatial light modulator forms two focusing points, a first focusing point and a second focusing point of the laser beam in the Z-axis direction. Operate, position the first focusing point of the laser beam on the upper surface of the inspection plate held on the holding surface by the Z-axis adjusting means, irradiate it, image it with the imaging means, and display the first focusing point on the display means. The X-coordinate and Y-coordinate positions of the points are obtained, the second condensing point of the laser beam is positioned on the upper surface of the inspection plate by the Z-axis adjusting means, irradiated, and the image is taken by the imaging means. The X-coordinate and Y-coordinate positions of the condensing point are obtained, and the X-coordinate and Y-coordinate positions of the first condensing point are matched with the X-coordinate and Y-coordinate position of the second condensing point. By adjusting the position of the optical axis of the spatial optical modulator so that the optical axis of the spatial optical modulator is aligned with the center of the condenser, the center of the condenser and the spatial optical modulator The center of the optical axis can be appropriately aligned with the center of the optical axis, and high-precision machining can be maintained even when laser machining is performed using a spatial optical modulator.

It is an overall perspective view of a laser processing apparatus. It is a block diagram which shows the optical system of the laser beam irradiation means provided in the laser processing apparatus shown in FIG. It is a conceptual diagram which shows the focusing point of a laser beam whose focusing characteristic was adjusted by a spatial light modulator, and (a) the first when the center of a condenser and the optical axis of a spatial light modulator are aligned. Conceptual diagram showing the positions of the condensing point and the second condensing point, (b) When the center of the concentrator and the optical axis of the spatial light modulator are deviated from each other, the first condensing point and , A conceptual diagram showing a deviation in the Y-axis direction from the second light collection point, (c) When the center of the light collector and the optical axis of the spatial light modulator are out of alignment, the first light collection point It is a conceptual diagram showing the deviation in the X-axis direction from the second focusing point.

Hereinafter, embodiments relating to an adjustment method for a laser processing apparatus configured based on the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows an overall perspective view of the laser processing apparatus 1 suitable for carrying out the adjustment method of the present invention, and details thereof will be described below.

The laser processing apparatus 1 shown in FIG. 1 includes a holding means 20 for holding a work piece, a moving means 30 for moving the holding means 20, and a laser beam irradiating means for irradiating a work piece held by the holding means 20 with a laser beam. 40, a display means 50, and an alignment means 60 are provided.

The holding means 20 moves in the X-axis direction indicated by the arrow X in the drawing and the rectangular X-axis direction movable plate 21 mounted on the base 2 so as to be movable in the Y-axis direction indicated by the arrow Y in the drawing. A rectangular Y-axis movable plate 22 freely placed on the X-axis movable plate 21, a cylindrical support 23 fixed to the upper surface of the Y-axis movable plate 22, and fixed to the upper end of the support 23. Includes a rectangular cover plate 26 and the like. The cover plate 26 is provided with a circular chuck table 25 that extends upward through an elongated hole formed on the cover plate 26. The chuck table 25 is configured to be rotatable by a rotation driving means (not shown). The holding surface 25a defined by the X-axis direction forming the upper surface of the chuck table 25 and the Y-axis direction orthogonal to the X-axis direction is formed of a porous material and has breathability, and the inside of the support column 23 is formed. It is connected to a suction means (not shown) by a flow path through which it passes. The chuck table 25 is also provided with a clamp 27 for fixing the annular frame F that supports the workpiece via the protective tape T. As shown in FIG. 1, the workpiece to be irradiated with the laser beam in the present embodiment is an inspection plate 10 used for adjusting the laser beam irradiating means 40 held by the annular frame F via the protective tape T. The upper surface 10a is coated with a tin film.

The moving means 30 is arranged on the base 2, and the X-axis direction feeding means 31 for processing and feeding the holding means 20 in the X-axis direction and the Y-axis direction feeding for indexing and feeding the Y-axis movable plate 22 in the Y-axis direction. Means 32 and. The X-axis direction feeding means 31 converts the rotational motion of the pulse motor 33 into a linear motion via the ball screw 34 and transmits it to the X-axis direction movable plate 21 along the guide rails 2a and 2a on the base 2. The movable plate 21 in the X-axis direction is moved forward and backward in the X-axis direction. The Y-axis direction feeding means 32 converts the rotational motion of the pulse motor 35 into a linear motion via the ball screw 36 and transmits it to the Y-axis direction movable plate 22, and the guide rail 21a on the X-axis direction movable plate 21 The movable plate 22 in the Y-axis direction is moved back and forth along the 21a in the Y-axis direction. Although not shown, the X-axis direction feeding means 31, the Y-axis direction feeding means 32, and the chuck table 25 are provided with position detecting means, and the position of the chuck table 25 in the X-axis direction, Y. The axial position and the circumferential rotation position are accurately detected and transmitted to the control means 100 (see FIG. 2) described later. Then, the rotation driving means of the X-axis direction feeding means 31, the Y-axis direction feeding means 32, and the chuck table 25 (not shown) is driven by the instruction signal instructed from the control means 100 based on the position information, and the holding means. The chuck table 25 can be positioned at a desired position on the 20.

As shown in FIG. 1, a frame body 4 is erected on the side of the moving means 30. The frame body 4 includes a vertical wall portion 4a arranged on the base 2 and a horizontal wall portion 4b extending in the horizontal direction from the upper end portion of the vertical wall portion 4a. An optical system including a laser beam irradiating means 40 is housed inside the horizontal wall portion 4b of the frame body 4.

An optical system including a laser beam irradiating means 40 provided in the laser processing apparatus 1 shown in FIG. 1 will be described with reference to FIG. The laser beam irradiating means 40 includes an oscillator 41 that oscillates a pulsed laser beam LB0 having predetermined characteristics, an attenuator 42 that adjusts the output of the laser beam LB0 oscillated from the oscillator 41, and a laser beam LB0 output from the attenuator 42. It was output from the spatial light modulator 43 that outputs the laser beam LB1 whose focusing characteristics are adjusted by adjusting the spatial distribution of the phase, the operating means 43A that operates the spatial light modulator 43, and the spatial light modulator 43. It includes a splitter 44 that reflects the laser beam LB1 and guides it in the Z-axis direction (vertical direction) toward the holding surface 25a of the chuck table 25, and transmits the light reflected by the workpiece held on the holding surface 25a. ..

The laser beam irradiating means 40 further drives a condenser 45 including a condenser lens 46 that concentrates the laser beam LB1 reflected by the splitter 44 on a workpiece held on the holding surface 25a, a drive motor (not shown), and the like. It is provided with a Z-axis adjusting means 45A that operates by means to relatively approach and separate the concentrator 45 and the holding means 20 in the Z-axis direction and adjust the position of the condensing point of the laser beam LB1. The condenser 45 is positioned on the lower surface of the tip portion of the horizontal wall portion 4b of the frame body 4 (see FIG. 1).

Further, the spatial light modulator 43 described above includes an optical axis adjusting means 43B for adjusting the position of the optical axis of the laser beam LB1 output by the spatial light modulator 43. By operating the optical axis adjusting means 43B to move the spatial light modulator 43 in the vertical direction in FIG. 2, the position of the holding surface 25a is adjusted in the Y-axis direction, and the spatial light modulation is performed in the direction perpendicular to the drawing. By moving the vessel 43, the position of the holding surface 25a is adjusted in the X-axis direction. The optical axis adjusting means 43B is composed of, for example, an adjusting screw for moving the spatial light modulator 43 in the X-axis direction and the Y-axis direction. In addition to the laser beam irradiating means 40 described above, the optical system includes an imaging means 47 that captures the light reflected on the workpiece held on the holding surface 25a and transmitted through the splitter 44.

As shown in FIG. 2, the laser processing apparatus 1 includes a control means 100. The control means 100 is composed of a computer, and temporarily stores a central processing unit (CPU) that performs arithmetic processing according to a control program, a read-only memory (ROM) that stores the control program, and detected detection values, arithmetic results, and the like. It has a readable and writable random access memory (RAM) for storing in, an input interface, and an output interface (details are not shown). In addition to controlling the moving means 30 and the laser beam irradiating means 40 described above by the control means 100, a control signal is output to the operating means 43A so that the spatial light modulator 43 can obtain desired focusing characteristics. The image captured by the imaging means 47 is captured and stored, and the image information is output to the display means 50.

In the laser processing apparatus 1 described above, the Z-axis adjusting means 45A is installed on the condenser 45 side, but it may be installed on the holding means 20 side, and the chuck table 25 of the holding means 20 is moved up and down in the Z-axis direction. By moving the laser beam LB1, the position of the focusing point of the laser beam LB1 on the workpiece can be adjusted.

The laser processing device 1 has substantially the same configuration as described above. Taking the laser processing device 1 as an example, the adjustment method of the present embodiment, more specifically, the condenser lens 46 of the condenser 45 Check whether the center and the optical axis of the laser beam LB1 output from the spatial light modulator 43 and reflected by the splitter 44 are deviated, and if they are deviated, the optical axis of the spatial light modulator 43 is set. The adjustment method for aligning with the center of the condenser 45 will be described below.

When making adjustments for aligning the optical axis of the spatial light modulator 43 arranged in the laser processing apparatus 1 with the center of the condenser lens 46 of the condenser 45, first, as described with reference to FIG. In addition, the inspection plate 10 held by the annular frame F via the protective tape T is prepared. The inspection plate 10 is a thin plate (dummy wafer) on a disk formed by imitating a semiconductor wafer that is laser-processed by the laser processing apparatus 1, and the upper surface 10a is coated with tin foil. The inspection plate 10 is not necessarily limited to a thin plate coated with tin foil, and may be, for example, a mirror wafer.

When the above-mentioned inspection plate 10 is prepared, it is placed on the holding surface 25a of the chuck table 25, a suction means (not shown) is operated to suck and hold the inspection plate 10, and the inspection plate 10 is fixed by the clamp 27. After the inspection plate 10 is fixed to the chuck table 25, the moving means 30 described above is operated to position the inspection plate 10 directly under the concentrator 45 of the laser beam irradiating means 40. If necessary, before positioning the inspection plate 10 directly under the condenser 45, the inspection plate 10 is once positioned directly under the alignment means 60, and the irradiation position on the upper surface 10a of the inspection plate 10 to be irradiated with the laser beam is imaged by the alignment means 60. May be detected.

When the inspection plate 10 is positioned directly under the condenser 45 of the laser beam irradiating means 40, the laser beam LB0 that sends a control signal from the control means 100 to the operating means 43A and is input to the spatial light modulator 43 is shown in FIG. As shown in a) to (c), two light collection points P1 and a second light collection point P2 are spaced apart from each other in the Z-axis direction (vertical direction) on the chuck table 25. The state is adjusted to the laser beam LB1 having the light-collecting characteristic in which points are formed. In the present embodiment, the first condensing point P1 and the second condensing point P2 are set to have a distance of 200 μm in the Z-axis direction. When the laser beam LB1 is adjusted by the spatial light modulator 43 to have the focusing characteristics forming the two focusing points as described above and output, for example, the first focusing point P1 included in the laser beam LB1 is included. It is assumed that one laser beam LB1a forming the above is parallel light, and the other laser beam LB1b included in the laser beam LB1 and forming the second focusing point P2 is diffused light, but is not necessarily limited to this. Do not mean. Further, the distance between the condensing point P1 and the condensing point P2 from the concentrator 45 is stored in advance in the control means 100.

First, the Z-axis adjusting means 45A is operated based on the distance from the concentrator 45 stored in the control means 100 in advance to the first condensing point P1, the position of the concentrator 45 is adjusted, and the chuck is chucked. The first focusing point P1 of the laser beam LB1a is positioned on the upper surface 10a of the inspection plate 10 held by the holding surface 25a of the table 25. Then, the oscillator 41 is operated to oscillate the laser beam LB0, and the laser beam LB1 is output from the spatial light modulator 43. As a result, a dent corresponding to the position of the first condensing point P1 is formed on the upper surface 10a of the inspection plate 10. Then, the dent is captured by the imaging means 47 via the splitter 44, stored in the control means 100, and displayed on the display means 50 shown in FIG. By specifying the position of the dent (= first condensing point P1) displayed on the display means 50 on the display means 50, the X coordinate and Y coordinate position (P1 (X)) of the first condensing point P1 , Y)) is calculated and stored in the control means 100.

As described above, when the X-coordinate and Y-coordinate positions (P1 (X, Y)) of the first condensing point P1 are obtained, then the Z-axis adjusting means 45A is operated to activate the condensing device 45. Is adjusted (raised by 200 μm), and the second focusing point P2 of the laser beam LB1b is positioned on the upper surface 10a of the inspection plate 10. Then, the oscillator 41 is operated to oscillate the laser beam LB0, and the laser beam LB1 is output from the spatial light modulator 43. As a result, a new dent corresponding to the second condensing point P2 is formed on the upper surface 10a of the inspection plate 10. Then, the dent is captured by the imaging means 47 via the splitter 44, stored in the control means 100, and displayed on the display means 50 shown in FIG. By specifying a new dent (= second light-collecting point P2) displayed on the display means 50 on the display means 50, the X-coordinate and Y-coordinate position (P2 (X)) of the second light-collecting point P2 , Y)) is calculated and stored in the control means 100.

Here, if the first condensing point P1 and the second condensing point P2 overlap in the Z-axis direction (vertical direction) and match (or match) at the X-coordinate and Y-coordinate positions on the holding surface 25a. As shown in FIG. 3A, the center C1 of the condenser lens 46 of the condenser 45 and the output from the spatial light modulator 43 are output by the splitter 44. It is determined that the light axis C2 of the reflected laser beam LB1 coincides with the light axis C2. Therefore, in this case, it is necessary to adjust the positions of the center C1 of the condenser lens 46 of the condenser 45 and the optical axis C2 of the laser beam LB1 output from the spatial light modulator 43 and reflected by the splitter 44. It is determined that there is no such adjustment, and the adjustment of the present embodiment is completed. On the other hand, as shown in the display means 50, FIG. 3 (b), and FIG. 3 (c) of FIG. 2, the position of the first condensing point P1 and the position of the second condensing point P2 deviate from each other. If it is determined that the light is aligned, the center C1 of the condenser lens 46 of the condenser 45 and the optical axis C2 of the laser beam LB1 reflected by the splitter 44 and guided to the condenser 45 are deviated from each other. Since it is judged, adjust the deviation as follows.

In order to align the center C1 of the condensing lens 46 of the condensing device 45 with the optical axis C2 of the laser beam LB1, the first condensing point P1 and the second condensing point P2 are held on the holding surface 25a. The optical axis adjusting means 43B may be operated so that the above X and Y coordinate positions match, and the position of the optical axis C2 of the laser beam LB1 output from the spatial light modulator 43 may be corrected.

More specifically, the direction of the straight line connecting the position of the first condensing point P1 and the position of the second condensing point P2 shown in the display means 50 of FIG. 2 is the direction of the condensing lens 46. The direction in which the position of the optical axis C2 of the laser beam LB1 should be corrected with respect to the center C1 is shown. Therefore, based on this direction, the direction for adjusting the position of the optical axis C2 of the laser beam LB1 is determined. Then, the distance between the two is calculated based on the position coordinates P1 (X, Y) of the first condensing point P1 and the position coordinates P2 (X, Y) of the second condensing point P2, and the distance is set to this distance. Based on this, the moving distance for moving the optical axis C2 of the laser beam LB1 is calculated. Regarding this moving distance, the amount of deviation between the center C1 of the condenser lens 46 of the condenser 45 and the optical axis C2 of the laser beam LB1 and the first focusing point according to the deviation amount are determined in advance by experiments or the like. The correlation between the deviation amount of P1 and the second condensing point P2 is obtained and stored in the control means 100, and based on the correlation, the center C1 of the condensing lens 46 of the condensing device 45 is used. The moving distance of the optical axis C2 of the laser beam LB1 that matches the optical axis C2 of the laser beam LB1 is calculated.

As described above, if the direction in which the optical axis C2 of the laser beam LB1 is moved and the moving distance are calculated, the optical axis adjusting means 43B is operated based on the calculation result to operate the optical axis of the spatial light modulator 43. Move the position of C2. As a result, as shown in FIG. 3A, the center C1 of the condenser lens 46 of the condenser 45 and the optical axis C2 of the laser beam LB1 can be aligned with each other.

The present invention is not limited to the above-described embodiment. For example, in the above-described embodiment, as the inspection plate 10, a top surface 10a coated with tin foil is prepared, and by irradiating the laser beam LB1, the inspection plate 10 corresponds to the first focusing point P1 and the second focusing point P2. A dent is formed at the position where the dent is formed, and the dent is detected by the imaging means 47. However, the output of the laser beam LB1 emitted from the laser beam irradiating means 40 is dented on the upper surface 10a of the inspection plate 10. The output is adjusted to a weak output that does not form the above light, is reflected by the upper surface 10a of the inspection plate 10, the reflected light is imaged by the imaging means 47, and the first condensing point P1 and the second condensing point P1 are condensing. The X-coordinate and Y-coordinate positions of the point P2 may be detected.

1: Laser machining equipment 2: Base 10: Inspection plate (workpiece)
10a: Top surface 20: Holding means 25: Chuck table 25a: Holding surface 27: Clamp 30: Moving means 31: X-axis direction feeding means 32: Y-axis direction feeding means 40: Laser beam irradiation means 41: Oscillator 42: Attenuator 43: Space Optical modulator 43A: Operating means 43B: Optical axis adjusting means 44: Splitter 45: Condenser 45A: Z-axis adjusting means 46: Condensing lens 47: Imaging means 50: Display means 60: Alignment means 100: Control means

Claims (1)

A holding means having a holding surface for holding a work piece defined in the X-axis direction and the Y-axis direction orthogonal to the X-axis direction, and a laser beam for irradiating the work piece held on the holding surface with a laser beam. The laser beam irradiating means includes an irradiating means, an imaging means for capturing the light reflected by the workpiece held on the holding surface, and a display means for displaying the image captured by the imaging means. The laser beam irradiating means emits a laser beam. An oscillating oscillator, a splitter that reflects the laser beam and guides it in the Z-axis direction orthogonal to the X-axis direction and the Y-axis direction, and transmits the light reflected by the workpiece, and the oscillator and the splitter. An attenuator arranged between the attenuators for adjusting the output of the laser beam oscillated by the oscillator, a spatial optical modulator arranged between the attenuator and the splitter for adjusting the focusing characteristics of the laser beam, and the spatial optical modulation. An operating means for operating the device, a concentrator that condenses the laser beam reflected by the splitter on a work piece held on the holding surface, and a concentrator and the holding means relatively in the Z-axis direction. It is an adjustment method of a laser processing apparatus composed of at least a Z-axis adjusting means for adjusting the position of a condensing point of a laser beam by approaching and separating from the laser beam.
The space light modulator operates the operating means so as to form two focusing points, a first focusing point and a second focusing point of the laser beam in the Z-axis direction, and the Z-axis adjusting means The first condensing point of the laser beam is positioned and irradiated on the upper surface of the inspection plate held on the holding surface, imaged by the imaging means, and the X coordinate of the first condensing point displayed on the display means. And the Y coordinate position is obtained, the second condensing point of the laser beam is positioned and irradiated on the upper surface of the inspection plate by the Z-axis adjusting means, the image is taken by the imaging means, and the second is displayed on the display means. The X-coordinate and Y-coordinate positions of the first condensing point are obtained, and the X-coordinate and Y-coordinate positions of the first condensing point coincide with the X-coordinate and Y-coordinate position of the second condensing point. A method for adjusting a laser processing apparatus, which aligns the optical axis of the spatial optical modulator with the center of the condenser by adjusting the position of the optical axis of the spatial optical modulator.

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