JP2016101611A - Manufacturing method of substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a substrate which reduces cracking and chipping of the substrate and improves the yielding.SOLUTION: A manufacturing method of a substrate which manufactures a plurality of substrates by cutting a material to be processed adhered to a slice base with wires includes: a processing process in which the material to be processed is cut by travelling the wires extended in a plurality of arrays, the plurality of substrates adhered to the slice base are obtained and the wires are located to the side of the slice base; and a wire pulling-out process in which the plurality of substrates are immersed to liquid entered into a container after the processing process and, in such a state as to stop the travelling of the wires, the wires are pulled out to the outer side of the substrate.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a method for manufacturing a substrate such as a semiconductor substrate.

  A wire saw apparatus is used to manufacture a plurality of substrates from a block by cutting blocks such as semiconductors, ceramics, and magnetic bodies. For example, when a substrate made of silicon or the like used for a solar cell element is manufactured, first, an ingot such as silicon is cut into a predetermined dimension to form a block. And a block is cut | disconnected, running a some wire provided in the wire saw apparatus, and a some board | substrate is manufactured.

  The manufacturing process of the substrate by the wire saw device includes the following processing process and wire drawing process. The processing step is a step in which the block is pressed in one direction against a plurality of wires and cut from one end of the block to the other end. In the machining process, machining fluid such as coolant, cutting fluid, and cleaning fluid is supplied to the traveling wire to cut the block. The wire drawing process is a process of moving the block in the direction opposite to the machining process and drawing the wire from the other end side of the block to the one end side.

  Here, as a wire drawing process, a method of drawing a wire while running the wire has been proposed (for example, see Patent Document 1 below).

JP 2010-194706 A

  However, in the wire drawing process described above, the substrates are likely to stick to each other due to the surface tension of the processing liquid. Further, the wire is in contact with the end portion of the substrate when the wire travels, and the end portion of the substrate is likely to be cracked or chipped. For this reason, when manufacturing a solar cell element, for example, it may cause a decrease in yield.

  Accordingly, an object of the present invention is to provide a method for manufacturing a substrate that reduces the generation of cracks and chips in the substrate and improves the yield.

  A substrate manufacturing method according to the present invention is a substrate manufacturing method for manufacturing a plurality of substrates by cutting a workpiece bonded to a slice base with a wire, and running the wires stretched in a plurality of rows. Cutting the workpiece to obtain a plurality of the substrates bonded to the slice base, and positioning the wires on the side of the slice base; and a plurality of the substrates in a liquid placed in a container And a wire drawing step of drawing the wire to the outside of the substrate in a state where the wire travels in a stopped state.

  According to the above substrate manufacturing method, the generation of cracks and chips in the substrate can be reduced, and the yield in manufacturing the substrate and the yield in manufacturing elements such as solar cell elements can be improved.

FIG. 1 is a perspective view schematically showing a configuration example of a wire saw device used in a substrate manufacturing method according to an embodiment of the present invention. FIG. 2A is a cross-sectional view schematically showing a processing step of the substrate manufacturing method according to one embodiment of the present invention, and FIG. 2B is viewed in the X direction shown in FIG. FIG. Fig.3 (a) is sectional drawing which shows typically one Embodiment of the wire drawing process of the manufacturing method of the board | substrate which concerns on one Embodiment of this invention, FIG.3 (b) shows in Fig.3 (a). It is sectional drawing seen in the X direction. FIG. 4 is a perspective view schematically showing a configuration example of a wire saw device used in the substrate manufacturing method according to the embodiment of the present invention.

  Hereinafter, a substrate manufacturing method according to an embodiment of the present invention will be described in detail with reference to the drawings. The drawings are schematically shown, and the size and positional relationship of various structures in each drawing can be appropriately changed. 2 to 4 omit some of the components shown in FIG. 1 and are simplified from FIG. Moreover, in FIGS. 2-4, in order to understand easily, hatching is drawn only to the process liquid.

<Wire saw device>
The wire saw apparatus S shown in FIGS. 1-3 is demonstrated. The wire saw device S presses a block 1, which is a workpiece fixed to the slice base 2, against the traveling wire 3 from above, cuts the block 1 with the wire 3, and manufactures a substrate from the block 1. Device.

  The block 1 is obtained, for example, by cutting an outer periphery of an ingot manufactured by a casting method or the like, or by cutting one ingot into a plurality of parts. For example, in order to manufacture a silicon substrate used for a solar cell element, an ingot made of single crystal silicon or polycrystalline silicon is used.

  When an ingot of single crystal silicon is produced by the CZ method or the like, the single crystal is raised by rotating the seed crystal to grow the single crystal. For this reason, in order to obtain the board | substrate for solar cell elements, the outer peripheral part of an ingot is cut | disconnected and a rectangular parallelepiped block whose cross-sectional shape is a rectangular shape (a square shape is included) is used in many cases. In the cross-sectional shape, a corner portion having an arc shape is also regarded as a rectangular shape.

  The polycrystalline silicon ingot, when made by a casting method or the like, depends on the shape of the mold, and is usually a rectangular parallelepiped and has a size capable of cutting out one or more blocks. In such a case, the block has a rectangular cross section (including a square shape), for example, a rectangular parallelepiped of 156 mm × 156 mm × 300 mm. In addition, what the corner | angular part was chamfered in the said cross-sectional shape shall be considered as a rectangular shape.

  The block 1 is bonded to a slice base 2 made of a carbon material, glass, resin, or the like via an adhesive or the like. As the adhesive, a thermosetting two-component epoxy resin, acrylic resin or acrylate resin, wax, or the like can be used. In order to make it easier to peel the substrate from the slice base 2 after slicing the block 1 to the substrate, it is preferable to use an adhesive whose adhesive force decreases as the temperature of the adhesive increases. One or more blocks 1 bonded to the slice base 2 are arranged in the wire saw device S by the work holder 10.

  The work holder 10 has a rectangular parallelepiped shape made of stainless steel or the like. The slice base 2 is fixed to the work holder 10 with the adhesive as described above.

  The wire 3 is supplied from the supply reel 7 and taken up on the take-up reel 8. The wire 3 is wound around a plurality of main rollers 5 (for example, a first main roller 5a, a second main roller 5b, and a third main roller 5c) between the supply reel 7 and the take-up reel 8, and the main roller 5 It is stretched between them. As the wire 3, for example, a piano wire whose main component is iron or an iron alloy is used. The wire 3 has a wire diameter of 80 μm or more and 180 μm or less, more preferably 120 μm or less. In this embodiment, the wire 3 uses an abrasive fixed wire in which abrasive grains made of diamond or silicon carbide are fixed to the outer periphery of the wire 3 by plating with nickel, copper, or chromium. In this case, the average particle diameter of the abrasive grains is preferably 5 μm or more and 30 μm or less.

  The container 6 stores, for example, a processing liquid 11 which is a liquid in which a part of the cut area of the block 1 is immersed. Moreover, this container 6 accommodates the liquid which collect | recovered the chip 1 of the block 1 and the processing liquid 11 which generate | occur | produce at the time of a cutting | disconnection, for example. Since the inter-substrate 1a in a state where the block 1 is cut is narrow, the main surfaces of the opposing substrates are easily subjected to surface tension (hereinafter, surface tension acting on the main surfaces of the substrates is referred to as "surface tension of the inter-substrate 1a"). . However, by immersing a part of the cut region of the block 1 in the liquid in the container 6, the influence of the surface tension between the substrates 1a is alleviated, making it difficult for the wire 3 to break and cutting performance and the like being lowered. It becomes difficult to do.

  When the processing liquid 11 is a coolant liquid, the processing liquid 11 is composed of a water-soluble solvent such as glycol and water, for example. Then, the machining liquid 11 is supplied to the plurality of wires 3 from the openings of the supply nozzle 4 having a plurality of openings. The supply flow rate of the machining liquid 11 supplied from the supply nozzle 4 is appropriately set depending on the size of the block, the number of blocks, and the like. Further, the machining liquid 11 may be used by being circulated, and when the circulated machining liquid 11 is supplied to the wire 3, it is preferable to remove abrasive grains, chips, and the like contained in the machining liquid 11.

  The main roller 5 includes a first main roller 5a and a second main roller 5b disposed below the block 1. The main roller 5 is made of, for example, urethane rubber such as ester, ether or urea, or resin such as ultra high molecular weight polyethylene. The main roller 5 has a diameter of 150 mm to 500 mm and a length of 200 mm to 1000 mm. A large number of grooves for arranging the wires 3 supplied from the supply reel 7 at predetermined intervals are provided on the surface of the main roller 5. The thickness of the substrate cut out from the block 1 is determined by the relationship between the interval between the grooves and the diameter of the wire 3.

  Below, the slicing method using the fixed abrasive grain type wire saw apparatus S which fixed the abrasive grain on the surface of the wire is demonstrated. The wire 3 is supplied from the supply reel 7 and is guided to the main roller 5 by the guide roller 9. The wires 3 are wound around the main roller 5 and the adjacent wires 3 are arranged at a predetermined interval. By rotating the main roller 5 at a predetermined rotational speed, the wire 3 can travel in the longitudinal direction of the wire 3. Further, the wire 3 is reciprocated by changing the rotation direction of the main roller 5. At this time, the length for supplying the wire 3 from the supply reel 7 is set to be longer than the length for supplying the wire 3 from the wire take-up reel 8, so that a new line is supplied to the main roller 5. The block 1 may be cut by running the wire 3 in one direction without reciprocating.

The block 1 is cut by lowering the block 1 and relatively pressing the block 1 against the wire 3 while supplying the machining liquid 11 from the supply nozzle 4 toward the wire 3 running at high speed. The The block 1 is divided into a plurality of substrates having a thickness of 200 μm or less, for example. At this time, the tension of the wire 3, the speed at which the wire 3 travels (travel speed), and the speed at which the block is lowered (feed speed) are appropriately controlled. For example,
The maximum traveling speed of the wire 13 is set to 500 m / min or more and 1000 m / min or less, and the maximum feed speed is set to 350 μm / min or more and 1100 μm / min or less.

  In addition, in the slicing method using the free abrasive type wire saw device in which the abrasive grains are put in the processing liquid 11 without adhering the abrasive grains to the surface of the wire, the abrasive liquid is used instead of the coolant liquid as the processing liquid. Use cutting fluid.

<Manufacturing process of substrate>
The basic process (working process and wire drawing process) of this embodiment will be described. In this embodiment, first, the upper surface of the block 1 having an upper surface and a lower surface is bonded to the slice base 2 via an adhesive or the like. In this state, the block 1 is cut from the lower surface to the upper surface of the block 1 while supplying the machining liquid 11 to the wires 3 stretched in a plurality of rows. The supply of the machining liquid 11 is not essential. Then, the plurality of substrates are bonded to the slice base 2 and the wire 3 is positioned on the slice base 2 side. The above is the processing step. Further, after this processing step, there is a wire drawing step for drawing the wire 3 from between adjacent substrates. In this wire drawing process, the substrate 1 is immersed in a liquid (for example, a liquid in the container 6 from which the processing liquid 11 has been collected) placed in the container 6, and the wire 3 is stopped while the wire 3 stops running. A step of pulling the wire 3 out of the wire. The immersion of the liquid substrate in the container 6 may be performed after the block 1 is cut to some extent, and may not necessarily be performed after the block 1 is completely cut. That is, the substrate may be immersed in the liquid in the container 6 in a processing step. However, in the wire drawing process, the substrate is always immersed in the liquid in the container 6.

  By the above-described wire drawing process, the influence of the surface tension between the substrates 1a is alleviated, and the generation of cracks and chips on the substrates can be reduced.

  Here, if the block 1 is cut by the wire 3 to which the machining liquid 11 is supplied and the machining liquid 11 is put into the container 6, the structure of the wire saw device S and the entire process may be simplified.

  Further, when the wire drawing step is performed by supplying the processing liquid 11 between the substrates adjacent to each other, the substrates may be further easily separated.

  Further, in the wire drawing step, a plate-like member is arranged below the wire 3, the processing liquid 11 is applied to the plate-like member, and the block 1 (between adjacent substrates) is interposed via the plate-like member. When the processing liquid is supplied, the substrates may be easily separated from each other.

  The block 1 is not limited to a semiconductor material. However, if the silicon is particularly susceptible to cracking in a rectangular parallelepiped shape, the substrate is less likely to be cracked or chipped, and the yield may be improved.

  In the present embodiment, the block 1 may be cut while immersing at least a part of the region where the block 1 is cut (the region after the wire 3 has passed) in the processing liquid 11 filled in the container 6. . At this time, the liquid level of the processing liquid 11 in the container 6 is preferably in a position where it does not come into contact with the traveling wire 3. Thereby, even if the wire 3 travels at a high speed, it can be cut without scattering the machining liquid 11. The interval between the processed portions (between substrates) 1a of the cut block 1 is narrow (for example, about 150 μm). For this reason, the processing liquid 11 is soaked up by the capillary phenomenon, and the influence of the surface tension of the inter-substrate 1a is alleviated, so that the wire 3 is not easily broken, and the machinability and the like are not easily lowered.

In addition, after the block 1 is immersed in the processing liquid 11 of the container 6, the supply amount of the processing liquid 11 supplied from the supply nozzle 4 may be adjusted as appropriate. In particular, when the machining fluid 11 uses a cutting fluid, the cutting performance changes, so that the machining fluid 11 is appropriately adjusted to be constant.

  At the same time as slicing the block 1, the slice base 2 is also cut to about 2 mm to 5 mm, and the wire 3 is pulled out from the inter-substrate 1a. At this time, the substrate can be taken out while being adhered to the slice base 2.

  When the wire 3 is pulled out of the substrate, the traveling of the wire 3 is stopped. In particular, in the fixed abrasive type, the abrasive grains are directly bonded and fixed to the wire 3. For this reason, the fixed abrasive type wire 3 is more likely to damage the substrate than the free abrasive type, but by stopping the traveling of the wire 3, the wire 3 is less likely to come into contact with the end of the substrate. The occurrence of cracks and chips can be reduced.

  On the other hand, when the traveling of the wire 3 is stopped, the contact resistance between the wire 3 and the substrate increases, and the substrate surface is easily damaged by the abrasive grains. Therefore, in the present embodiment, the wire 3 is pulled out from the inter-substrate 1a while immersing at least a part of the block 1, particularly the end portion of the block 1 on the cutting start side in the processing liquid 11 in the container 6. By immersing the inter-substrate 1a in the processing liquid 11, the influence of the surface tension of the inter-substrate 1a is alleviated, and the end portion at the beginning of cutting in the block 1 is not easily narrowed. For this reason, the substrate is not easily damaged when the wire 3 is pulled out.

  Further, as shown in FIGS. 3 and 4, in the wire drawing process, the working liquid 11 may be supplied from the left and right sides of the block 1 after cutting to the inter-substrate 1a. For example, in the wire drawing process, a machining liquid supply control member 12 which is a plate-like (including tray shape) member for supplying a machining liquid is inserted immediately below the wire 3 being drawn, and this machining liquid supply control member 12 is inserted. It is preferable to supply the machining liquid 11 to the inter-substrate 1a by controlling the traveling direction of the machining liquid 11 through the substrate. By disposing the machining liquid supply control member 12 immediately below the wire 3 positioned in the vicinity of the block 1, the machining liquid 11 is sufficiently supplied to the inter-substrate 1 a of the wire 3. For this reason, the wire 3 can be easily pulled out from the inter-substrate 1a. In particular, when the blocks are cut in parallel, the cut area is widened, which is effective because the wire 3 can be easily pulled out from the inter-substrate 1a.

  Further, the immersion of at least a part of the cut region of the block 1 in the processing liquid 11 may be performed immediately after the processing step or immediately before the wire drawing step, or may be performed during the processing step. When the block 1 is immersed in the processing liquid 11 in the processing step, at least a part of the cut region of the block 1 is cut after a height of 1/3 or more (more preferably half or more) of the block 1 is cut. It is desirable to adjust the height of the processing liquid 11 in the container 6 so as to be immersed in the processing liquid 11. After the height of 1/3 or more (more preferably half or more) of the block 1 is cut, it is easily affected by the surface tension of the inter-substrate 1a. For this reason, by adjusting the height of the working liquid 11 in the container 6 within the above range, in the fixed abrasive type wire saw device S, it is difficult to apply a load to the wire 3 being cut, and the wire 3 is disconnected. It ’s hard.

  In the step of immersing the block 1 in the machining liquid 11, the depth at which the block 1 is immersed in the machining liquid 11 may be adjusted by changing the height of the liquid level of the machining liquid 11. For example, it is desirable to adjust so that the liquid level of the processing liquid 11 does not contact the wire 3 in the processing step, and it is desirable to adjust the liquid level to contact the wire 3 in the wire drawing step. This is because if the wire 3 comes into contact with the liquid surface of the machining liquid 11 while the wire 3 is traveling, the traveling of the wire becomes unstable. The height of the liquid level may be adjusted by adjusting the supply amount and discharge amount of the machining liquid 11. In addition to supplying the processing liquid 11 to the supply nozzle 4, a supply port to the container 6 may be provided separately and supplied from the supply port.

  Further, after the height of 1/3 or more (more preferably half or more) of the block 1 is cut, the processing liquid is put in the container 6 in advance until the height at which the end of the block 1 on the cutting start side is immersed in the processing liquid. It may be satisfied. Thereby, the influence of the surface tension of the inter-substrate 1a can be alleviated without providing a mechanism for adjusting the processing liquid 11 separately.

  Further, the processing liquid 11 in the container 6 may be irradiated with ultrasonic waves or air may be bubbled. Thereby, the influence of the surface tension between the substrates 1a is alleviated, the wire 3 is less likely to be disconnected, and the machinability and the like can be improved.

  Then, the substrate-to-substrate 1a taken out is put into the next cleaning step while being bonded to the slice base 2.

  In the cleaning process, an alkaline liquid or a neutral liquid is used as a cleaning liquid, and water-soluble coolant, oil, and dirt adhering to the substrate are cleaned, and then the detergent is washed away with water. Then, the substrate surface can be completely dried by hot air or air, and separated from the slice base 2 to obtain a separated substrate.

  As described above, according to the substrate manufacturing method of the present embodiment, it is possible to prevent the substrate end portion from being easily cracked or chipped in the wire drawing process. Thereby, generation | occurrence | production of a substrate crack can be suppressed in the manufacturing process of a solar cell element, and a solar cell element can be produced with a high yield.

<Modification>
In addition, this invention is not limited to the said embodiment, Many corrections and changes can be added within the scope of the present invention.

  For example, the ingot as a workpiece may be processed as it is without cutting the end of the ingot or the like into a shaped block.

  Further, the number of blocks 1 to be cut may be one or plural. A plurality of blocks 1 may be arranged in parallel. In this case, in the wire saw apparatus S that is mounted so that a plurality of blocks 1 are in contact with each wire 3, the present invention is particularly effective because improvement in productivity can be expected as compared with the conventional technique.

  Further, a cutting fluid containing abrasive grains may be used as the processing fluid 11. Such a machining liquid 11 can be used, for example, in a loose abrasive type wire saw device S that cuts the block 1 by the lapping action of the wire 3. In this case, the wire 3 to be used is wound around the main roller 5. As the wire 3, for example, a piano wire whose main component is iron or an iron alloy may be used. The wire 3 has a wire diameter of 80 μm or more and 180 μm or less, more preferably 120 μm or less. The processing liquid 11 is configured by mixing wrapping oil composed of abrasive grains such as silicon carbide, alumina and diamond, mineral oil, a surfactant and a dispersant. Further, the machining liquid 11 is supplied to a plurality of wires 3 stretched from a supply nozzle 4 having a plurality of openings. As the average particle size of the abrasive grains, for example, those having a narrow particle size distribution of 5 μm or more and 20 μm or less are used. The supply flow rate of the machining liquid 11 supplied to the supply nozzle 4 is appropriately set according to the size and number of blocks. In addition, the machining liquid 11 may be circulated and used, and at that time, new abrasive grains may be added as appropriate to the used machining liquid 11 and supplied to the wire 3.

  Examples according to the present invention will be described below.

  First, an adhesive made of an epoxy resin was applied to a slice base made of a carbon plate. Next, a block made of rectangular parallelepiped polycrystalline silicon having a size of 156 mm × 156 mm × 300 mm was placed on the adhesive applied to the slice base, and then the adhesive was cured. And the block adhere | attached on the slice base was installed in the wire saw apparatus.

  At this time, a wire in which diamond abrasive grains were fixed by Ni plating (wire diameter = 120 μm, average grain diameter of abrasive grains = 14 μm, average diameter D = 148 μm) was run in both directions at about 600 m / min. While supplying the machining fluid to the wire while the wire was running, the block adhered to the slice base was sliced to produce a silicon substrate having a 156 mm square and an average thickness of 200 μm. A glycol aqueous solution was used as the processing liquid.

  Moreover, the container which collect | recovers the processing liquid used by the processing process was arrange | positioned under the block, and the processing liquid was stored in the container. The processing step and the wire drawing step were performed under the conditions shown in Table 1.

  In condition 1, after the height of 1/3 of the block was cut, the cut end of the block 1 was immersed in the liquid in the container, and the processing step and the wire drawing step were performed. Under condition 1, the substrate portion cut in both the processing step and the wire drawing step was immersed in the processing liquid.

  In condition 2, after all the blocks were cut, the wire drawing step was carried out by immersing the cut end portion (cut substrate portion) of the block 1 in the processing liquid in the container only in the wire drawing step.

  Under Condition 3, the machining process and the wire drawing process were performed without putting the machining liquid into the container, and the wire travel was stopped in the wire drawing process.

  In condition 4, the processing step and the wire drawing step were performed without putting the processing liquid in the container, and the wire was run at 1 m / min later than the processing step.

  In condition 5, after all the blocks are cut, the wire pulling process is performed by immersing the cut end (cut substrate part) of block 1 in the processing liquid in the wire pulling process and running the wire at 1 m / min. did.

  Under conditions 1, 2, and 5, in the wire drawing process, a plate-like member for supplying the processing liquid between the substrates was inserted immediately below the wire, and then the wire was drawn. In condition 3, the wire could not be drawn due to the surface tension of the processing liquid adhering between the substrates.

  Thereafter, cracks and chips at the edge of the substrate were determined by an appearance inspection machine (determined by image processing by irradiating light to the substrate) and visual inspection. Then, the occurrence rate of cracks and chips (ratio of the number of substrates with cracks and chips to the total number of substrates) was determined. The results are shown in Table 1.

  As shown in Table 1, in conditions 1 and 2, it was confirmed that the occurrence rate of cracks and chips was greatly reduced (yield was greatly improved) as compared with conditions 3 and 5.

  It should be noted that the storage of the processing liquid in the processing process is irrelevant to the cracking or chipping of the substrate. For this reason, although not described in Table 1, the condition was the same as that in the case where the machining fluid was stored in the machining process, the machining fluid was saved in the wire drawing process, and the wire traveled. Further, in the case where there is a working fluid reservoir in the machining process, in the case where there is no machining reserve in the wire drawing process and there is wire traveling, the condition 4 was the same. Further, in the case where the machining liquid was stored in the machining process, there was no machining storage in the wire drawing process, and the case where there was no wire travel was the same as Condition 3.

1: Work piece (block)
DESCRIPTION OF SYMBOLS 1a: Between board | substrates 2: Slice base 3: Wire 4: Supply nozzle 5: Main roller 6: Container 7: Supply reel 8: Take-up reel 9: Guide roller 10: Work holder 11: Processing liquid 12: Processing liquid supply control member 13: Adhesive S: Wire saw device

Claims (6)

A substrate manufacturing method for manufacturing a plurality of substrates by cutting a workpiece bonded to a slice base with a wire,
A processing step of running the wires stretched in a plurality of rows to cut the workpiece, obtaining the plurality of substrates bonded to the slice base, and positioning the wires on the slice base side;
A method of manufacturing a substrate, comprising: immersing a plurality of the substrates in a liquid placed in a container; and pulling the wires to the outside of the substrate in a state where traveling of the wires is stopped.   The substrate manufacturing method according to claim 1, wherein the workpiece is cut by the wire to which a processing liquid is supplied, and the processing liquid is put into the container.   The substrate manufacturing method according to claim 2, wherein the wire drawing step is performed by supplying the processing liquid between the substrates adjacent to each other.   The wire drawing step includes disposing a plate-like member below the wire, applying the machining liquid to the plate-like member, and supplying the machining liquid to the workpiece through the plate-like member. Item 4. A method for producing a substrate according to Item 2 or 3.   The substrate manufacturing method according to claim 1, wherein the wire is a wire having abrasive grains fixed on a surface thereof.   The substrate manufacturing method according to claim 1, wherein the workpiece is made of rectangular parallelepiped silicon.

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