JP2020061515A - Manufacturing method of recovered wafer - Google Patents

Abstract

To provide a manufacturing method of a recovered wafer, which reduces a removal amount of a wafer by shallowing a crushed layer as compared with the case of using a pipe-shaped electroforming grading blade.SOLUTION: A manufacturing method of a recovered wafer, for manufacturing the recovered wafer, comprises: a roughness grinding step of grinding a circuit layer on a front face side of a wafer with a first grinding wheel in which a plurality of first grinding grinders to which abrasive grains of #500 or more and #1200 or less are fixed with a vitrified bonded is arranged in an annular shape; a finish grinding step of grinding the front face side of the wafer with a second grinding wheel in which a plurality of second grinding grinder to which the abrasive grains of #2000 or more and #5000 or less are fixed is arranged in an annular shape after the roughness grinding step; and a grinding step of removing a crushed layer remaining on the front face side of the wafer by chemical-mechanically grinding the front face side of the wafer after the finish grinding step.SELECTED DRAWING: Figure 8

Description

  The present invention relates to a method for manufacturing a reclaimed wafer in which a circuit layer is removed during the formation of a circuit layer on the front surface side of a wafer or after the circuit layer is formed on the front surface side to manufacture a reclaimed wafer.

  In a semiconductor device manufacturing process, a circuit layer is formed on a surface of a wafer made of silicon or the like, and then the wafer is cut along a dividing line to manufacture a plurality of semiconductor devices from the wafer.

  By the way, during the manufacturing process of a semiconductor device, when a defective wafer having a defective portion in a circuit layer occurs, or a dummy wafer or the like on which a test circuit pattern for performing a test of electrical continuity is formed is intentionally manufactured. There are cases.

  In defective wafers and dummy wafers, the circuit layer is formed only in the thickness range of several tens of μm from the surface of the wafer. Therefore, by removing this circuit layer from the surface of the wafer, the defective wafer etc. It can be reused as a new wafer (that is, a reclaimed wafer). In particular, in recent years, semiconductor devices have been actively manufactured, and the supply of wafers of a predetermined size is low. Therefore, there is an increasing need for manufacturing recycled wafers.

  However, since metal such as copper (Cu) and resin are mixed in the circuit layer, when the circuit layer is ground, the grinding is performed as compared with the case where a single wafer on which the circuit layer is not formed is ground. Blades are easily clogged. Therefore, it is difficult to grind and remove the circuit layer. Therefore, as a high-strength grinding blade (grinding stone) for grinding the circuit layer, a pipe-shaped electroformed grinding blade (grinding stone) in which diamond abrasive grains are electroformed with nickel (Ni) was devised ( See, for example, Patent Document 1).

JP 2000-269174 A

  However, when the circuit layer is ground with the pipe-shaped electroformed grinding blade, a relatively deep crush layer is formed on the wafer located below the circuit layer. If the wafer is further ground and polished to remove all of this deep fracture layer, the reclaimed wafer must be thin. It is difficult to reuse a thin reclaimed wafer in the semiconductor device manufacturing process.

  The present invention has been made in view of the above problems, by grinding and removing the circuit layer so that the fracture layer becomes shallower than when using a pipe-shaped electroformed grinding blade, the removal amount of the wafer It is an object of the present invention to provide a method for manufacturing a reclaimed wafer that can reduce

  According to one aspect of the present invention, during the formation of a circuit layer on the surface of the wafer or after forming the circuit layer on the surface, the circuit layer is removed from the front surface side of the wafer to produce a recycled wafer. A method for manufacturing a regenerated wafer, comprising: a first grinding wheel in which a plurality of first grinding wheels to which abrasive grains of # 500 or more and # 1200 or less are fixed by vitrified bonds are annularly arranged. A rough grinding step of grinding the circuit layer on the front surface side, and after the rough grinding step, a plurality of second grinding wheels in which abrasive grains of # 2000 or more and # 5000 or less are fixed by vitrified bonds are arranged in an annular shape. A finishing grinding step of grinding the surface side of the wafer with a second grinding wheel, and a chemical mechanical polishing of the surface side of the wafer after the finishing grinding step, Method for producing a reproduction wafer and a polishing step of removing the crushing layer remaining is provided.

  Preferably, the method for manufacturing a reclaimed wafer is configured such that after the finish grinding step and before the polishing step, a plurality of third grinding wheels in which abrasive grains of # 6000 or more and # 8000 or less are fixed by vitrified bonds are annularly formed. A third grinding wheel arranged to grind the surface side of the wafer to make the thickness of the fracture layer remaining on the surface side of the wafer smaller than the thickness of the fracture layer after the finish grinding step; Further comprising a finishing grinding step.

  Also, preferably, the first, second, and third grinding wheels are solid segment wheels.

  Further, preferably, in the method for manufacturing a recycled wafer, the rough grinding step is performed without a preliminary processing step of etching and modifying the circuit layer.

  In the method for manufacturing a reclaimed wafer according to one aspect of the present invention, since vitrified bond is used as the binding material of the first grinding wheel that performs the rough grinding step, the grinding of the circuit layer is more difficult than the case of using other binding materials. As a result, the grinding wheel is properly consumed, and the self-developing blade of the grinding wheel is generated. Therefore, it is possible to stably grind the wafer without causing the grinding wheel to be crushed or clogged.

  Furthermore, since the circuit layer is removed by using a grinding wheel in which the abrasive grains are fixed by vitrified bond, compared to the case of using a pipe-shaped electroformed grinding blade or a solid grinding wheel formed by electroformed bond, The load per unit area on the wafer can be reduced. Therefore, as compared with the case where a pipe-shaped electroformed grinding blade or an electroformed bond grinding wheel is used, the crush layer remaining on the wafer can be made shallow, and the amount of wafer removed can be reduced.

  In addition, after the rough grinding step, a finishing grinding step is performed using a second grinding wheel having a count larger than that of the first grinding wheel, and then a polishing step is performed, so that the finishing grinding step is not performed. The crushed layer formed in the rough grinding step can be removed earlier than in the case of performing the polishing step.

It is a perspective view showing an example of a processing device. FIG. 2A is a perspective view of the grinding surface side of the first grinding wheel, and FIG. 2B is a perspective view of one first grinding wheel. 3A is a perspective view showing an example of a wafer, and FIG. 3B is a sectional view taken along line III-III of FIG. 3A. It is a perspective view of the wafer to which the protection member was attached. It is a figure which shows the mode of a rough grinding step (S20), a finish grinding step (S30), and a final finish grinding step (S40). It is a figure which shows the mode of a polishing step (S50). FIG. 7A is a diagram showing the removal amount in each of the rough grinding step (S20), the finish grinding step (S30), the final finish grinding step (S40) and the polishing step (S50), and FIG. [FIG. 8] is a perspective view of a reclaimed wafer in a polishing step (S50). It is a flowchart of the manufacturing method of a recycled wafer.

  An embodiment according to an aspect of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a perspective view showing an example of the processing device 2. The processing device 2 is a device that performs grinding or the like on a wafer that is a workpiece.

  The processing device 2 includes a base 4 having a substantially rectangular parallelepiped shape. A support structure 6 having a rectangular parallelepiped shape is provided in the vicinity of one side on the back side of the rectangular upper surface of the base 4 in a manner protruding from the upper surface of the base 4. A pair of rails 8 and another pair of rails 10 are provided on the front side of the support structure 6 along the height direction (Z-axis direction) of the base 4.

  An elevating plate forming a rough grinding unit feeding mechanism 14 is mounted on the pair of rails 8. A rough grinding unit 12 is provided on the surface of the lift plate, and a nut portion is provided on the back surface of the lift plate. A Z-axis ball screw connected to the motor part is rotatably connected to the nut part. By driving this motor unit, the rough grinding unit 12 moves along the Z-axis direction.

  Here, a detailed configuration of the rough grinding unit 12 will be described with reference to FIGS. 1, 2A, 2B and 5. 2A is a perspective view of the grinding surface side of the first grinding wheel 26-1, and FIG. 2B is a perspective view of one first grinding wheel 30-1. .

  The rough grinding unit 12 has a cylindrical spindle housing 20. A motor 32 for rotationally driving the spindle 22 is connected to an upper end of the spindle 22, and the spindle 22 is rotatably accommodated in the spindle housing 20.

  The lower end of the spindle 22 is exposed to the outside from the lower surface of the spindle housing 20. As shown in FIG. 5, a disc-shaped wheel mount 24 is provided at the lower end of the spindle 22. A first grinding wheel 26-1 is mounted on the side of the wheel mount 24 opposite to the spindle 22.

  As shown in FIG. 2A, the first grinding wheel 26-1 has an annular wheel base 28 having a diameter substantially equal to that of the wheel mount 24. The wheel base 28 has a mounting surface to be mounted on the wheel mount 24 and a grindstone disposition surface located on the opposite side of the mounting surface. A plurality of first grinding wheels 30-1 are annularly arranged on the wheel mounting surface of the wheel base 28.

  As shown in FIG. 2B, the first grinding wheel 30-1 of the present embodiment has a curved inner peripheral side surface 30a and an outer peripheral side surface 30b. In addition, one side of the inner peripheral side surface 30a and the outer peripheral side surface 30b is connected to the rectangular first side surface 30c, and the other side side is the second rectangular side surface opposite to the first side surface 30c. Connect to the side surface 30d.

  Moreover, one side in the height direction of each side surface of the first grinding wheel 30-1 is connected to the top surface 30e, and the other side in the height direction is connected to the bottom surface. An adhesive agent 30f is applied to this bottom surface, and the first grinding wheel 30-1 is fixed to the grinding surface of the wheel base 28 via the adhesive agent 30f. The first grinding wheel 30-1 is a solid segment wheel without a columnar space (for example, a through hole) penetrating from the top surface 30e to the bottom surface.

  In the first grinding wheel 30-1 (that is, vitrified bond grinding wheel), the abrasive grains are fixed by vitrified bond. The first grinding wheel 30-1 is prepared by mixing abrasive grains such as alumina, silicon carbide, diamond, CBN (Cubic Boron Nitride) with a binder such as ceramics (that is, vitrified bond), and then pressing the mixture. It is manufactured by molding and then sintering.

  The first grinding wheel 30-1 is more easily worn than a solid grinding wheel formed by a pipe-shaped electroformed grinding blade or an electroformed bond (hereinafter collectively referred to as an electroformed bond grinding wheel). Because it is easy to self-blade. Therefore, the first grinding wheel 30-1 is less likely to be crushed or clogged (that is, the sharpness is easily maintained) as compared with the electroformed grinding blade, and can exhibit stable grinding ability. Therefore, compared with the case of using an electroformed bond grinding wheel, the necessary grinding ability is exhibited even if the load on the wafer per unit area is reduced, so that the crush layer formed on the surface to be ground of the wafer Can be shallow.

  As the abrasive grains of the first grinding wheel 30-1 of the present embodiment, abrasive grains having a grain size of # 500 or more and # 1200 or less are used. The symbol # and the number shown to the right of it indicate the granularity, and the number shown to the right of the symbol # is called the number (or count).

  The "greater than or equal to" and "less than or equal to" in "# 500 or more and # 1200 or less" indicate the lower limit and the upper limit of the number (or number). The smaller the count, the larger the maximum diameter of the abrasive grains, and the larger the count, the smaller the maximum diameter of the abrasive grains.

  The particle size described in the present embodiment is the JIS standard JISR6001-2: 2017 (the particle size of the grinding material for the grinding wheel-part 2: fine powder) of the JIS standard established by the Japanese Industrial Standards Committee (JISC). Refer to or follow the conventions commonly used in the industry of manufacturing and selling whetstones.

  Details of how to determine the particle size are described in the above-mentioned JISR6001-2: 2017. For example, the grain size of the abrasive grains is determined by using a sedimentation tube test method or the like. The grain size of the abrasive grains of the present embodiment is determined, for example, by the above-mentioned settling tube test method.

  However, the standard particle size distribution of the particle size not described in the sedimentation tube test method may be determined by analogy applying from the standard particle size distribution of the particle size described in the electrical resistance test method. For example, the standard particle size distribution larger than # 3000 in the sedimentation tube test method is determined by analogy applying the standard particle size distributions of # 3000, # 4000, # 6000 and # 8000 in the electrical resistance test method. Further, the standard particle size distribution corresponding to each particle size may be determined according to the sedimentation tube test method described in JISR6001-2: 2017.

  Here, the description of the rough grinding unit 12 is finished, and the description of the other configuration of the processing apparatus 2 will be made. When the rough grinding unit 12 is viewed from the front, another pair of rails 10 is provided on the right side of the pair of rails 8. The other pair of rails 10 is equipped with an elevating plate that constitutes the finish grinding unit feeding mechanism 18.

  Similarly to the rough grinding unit feeding mechanism 14, the finish grinding unit feeding mechanism 18 is also composed of an elevating plate, a nut portion, a Z-axis ball screw, a motor portion, and the like. The finishing grinding unit 16 is connected to the front surface side of the lift plate, and the finishing grinding unit 16 moves along the Z-axis direction by driving the motor unit.

  The finish grinding unit 16 has a spindle housing 20, a spindle 22, a wheel mount 24, a second grinding wheel 26-2, and the like, and is configured similarly to the rough grinding unit 12.

  The grinding wheel of the second grinding wheel 26-2 (that is, the second grinding wheel 30-2) has a larger count (that is, a smaller maximum diameter) than the first grinding wheel 30-1. Grains are fixed with vitrified bonds. Abrasive grains having a grain size of # 2000 or more and # 5000 or less are used as the abrasive grains of the second grinding wheel 30-2 of the present embodiment.

  Except for the above points, the configuration of the finish grinding unit 16 is almost the same as that of the rough grinding unit 12. For example, like the first grinding wheel 30-1, the second grinding wheel 30-2 is also a solid segment wheel. Therefore, the details of the arrangement of the plurality of second grinding wheels 30-2, the configuration of the second grinding wheel 26-2, and the like will be omitted.

  A turntable 34 is disposed below the rough grinding unit 12 and the finish grinding unit 16. The turntable 34 is arranged substantially parallel to the upper surface of the base 4 on the front side of the support structure 6.

  The turntable 34 is rotated in a direction indicated by an arrow 36 by, for example, a rotation drive mechanism (not shown). On the turntable 34, one chuck table 38 is arranged in each of the regions which are substantially divided into four equal parts in the circumferential direction.

  Each chuck table 38 has a wafer loading / unloading area A (hereinafter simply referred to as area A), a rough grinding processing area B (hereinafter simply referred to as area B), and finish every time the turntable 34 is rotated by 90 degrees in the direction of arrow 36. The grinding processing area C (hereinafter, simply area C) and the final finish grinding processing area D (hereinafter, simply area D) are sequentially moved.

  A disk-shaped porous member (not shown) is provided on the upper part of each chuck table 38, and the upper surface of this porous member is a holding surface 38a (see FIG. 5) for sucking and holding the wafer. . Below the chuck table 38, a suction path (not shown) having one end connected to a suction source (not shown) is provided, and the other end of the suction path is connected to the porous member.

  By applying a negative pressure generated by the suction source to the wafer placed on the holding surface 38a, the wafer is sucked and held by the holding surface 38a. A rotation mechanism (not shown) is connected to the chuck table 38, and the chuck table 38 can rotate around an axis perpendicular to the holding surface 38a.

  A rough grinding unit 12 is arranged above the region B, and a finish grinding unit 16 is arranged above the region C. Further, above the area D, the final finishing grinding unit 40 is arranged. Note that, in FIG. 1, the final finishing grinding unit 40 is simplified and shown in a rectangular parallelepiped shape.

  The final finish grinding unit 40 has a spindle housing 20, a spindle 22, a wheel mount 24, a third grinding wheel 26-3, and the like, and is configured similarly to the rough grinding unit 12.

  The grinding wheel of the grinding wheel 26 (that is, the third grinding wheel 30-3) is a vitrified bond of abrasive grains having a larger count (that is, a smaller maximum diameter) than the second grinding wheel 30-2. It is fixed. Abrasive grains having a grain size of # 6000 or more and # 8000 or less are used as the abrasive grains of the third grinding wheel 30-3 of the present embodiment.

  The configuration of the final finishing grinding unit 40 is substantially the same as that of the rough grinding unit 12 except for the above points. For example, like the first grinding wheel 30-1, the third grinding wheel 30-3 is also a solid segment wheel. Therefore, further detailed description of the arrangement of the plurality of third grinding wheels 30-3 and the configuration of the third grinding wheel 26-3 will be omitted.

  On the front side of the upper surface of the base 4 located on the side opposite to the support structure 6, two projecting portions projecting in the horizontal direction are provided. A first cassette 62 for accommodating unprocessed wafers is removably placed on the upper surface of one of the two protruding portions, and a first cassette 62 for accommodating the processed wafer is disposed on the other upper surface of the two protruding portions. The second cassette 64 is detachably mounted.

  A wafer transfer robot 66 is provided between the first cassette 62 and the second cassette 64 and the turntable 34. A temporary table 68 and a spinner cleaning unit 70 are provided near the wafer transfer robot 66.

  The wafer transfer robot 66 carries out the wafers stored in the first cassette 62 to the temporary placement table 68. Further, the wafer transfer robot 66 transfers the processed wafer cleaned by the spinner cleaning unit 70 to the second cassette 64.

  A transport unit 72 is provided on the side surface of the end of the base 4 on the temporary table 68 side. The transport unit 72 has a pair of support columns 74 provided along the Z-axis direction. A plate-shaped guide rail 76 provided along the Y-axis direction is fixed to the upper ends of the pair of support columns 74.

  The guide rail 76 is provided with a Y-axis moving mechanism (not shown). The Y-axis moving mechanism of the guide rail 76 is provided with a rectangular parallelepiped moving block 78, and an upper end of a rod-shaped support rod 80 along the Z-axis direction is connected to the moving block 78.

  The support rod 80 can be moved in the Z-axis direction by a lifting mechanism (not shown). The lower end of the support rod 80 is connected to one end of an arm portion 82 extending toward the turntable 34 side along the X-axis direction. The arm portion 82 is provided with a disk-shaped suction pad 84 that sucks a wafer via an X-axis moving mechanism (not shown).

  The transfer unit 72 uses the above-described X-axis, Y-axis, and Z-axis moving mechanism to transfer the unprocessed wafer from the temporary placement table 68 to the chuck table 38 positioned in the area A. Further, the transfer unit 72 transfers the processed wafer from the chuck table 38 positioned in the area A to the spinner cleaning unit 70.

  The wafer is cleaned and dried by the spinner cleaning unit 70, and then transferred to the second cassette 64 by the wafer transfer robot 66. After that, the second cassette 64 is transported to a polishing device (not shown) different from the processing device 2.

  The outline of the polishing apparatus is shown in FIG. Similar to the processing device 2, the polishing device has a chuck table 38 for sucking and holding the wafer carried out from the second cassette 64. A rotation mechanism (not shown) is connected to the chuck table 38, and the chuck table 38 can rotate about an axis perpendicular to the holding surface 38a.

  The polishing apparatus includes a polishing unit 42 that polishes the wafer held on the chuck table 38. The polishing unit 42 has a spindle 44 rotatably housed in a spindle housing (not shown).

  One end of the spindle 44 is exposed to the outside from the lower surface of the spindle housing, and a disc-shaped wheel mount 46 is fixed to one end of the spindle 44. A polishing wheel 48 is detachably attached to the wheel mount 46.

  The polishing wheel 48 has a disk-shaped base 50 having a diameter substantially equal to that of the wheel mount 46. A disc-shaped polishing pad 52 is attached to the bottom surface of the base 50. The polishing pad 52 is formed, for example, by dispersing abrasive grains of alumina, silicon carbide, diamond, CBN, or the like in polyurethane or felt and fixing the abrasive grains with a bonding agent.

  A central portion of the base 50 and the polishing pad 52 is hollow, and a polishing liquid supply passage 54 formed so as to penetrate through the central portions of the spindle 44 and the wheel mount 46 is connected to the hollow portion.

  The polishing liquid is supplied to the polishing surface (lower surface) of the polishing pad 52 via the polishing liquid supply path 54 and the cavities of the base 50 and the polishing pad 52. When the polishing liquid contains abrasive grains, the polishing pad 52 need not contain abrasive grains.

  Next, the wafer 1 processed using the processing device 2 and the polishing device will be described. 3A is a perspective view showing an example of the wafer 1, and FIG. 3B is a sectional view taken along line III-III of FIG. 3A. The wafer 1 is made of a semiconductor material such as silicon and has a substantially disc shape. A circuit layer 3 is formed on the front surface 1 a of the wafer 1.

  In the present embodiment, the surface of the circuit layer 3 opposite to the surface 1a of the wafer 1 is referred to as the surface 3a of the circuit layer 3. Further, the surface of the wafer 1 opposite to the front surface 1 a of the wafer 1 is referred to as the back surface 1 b of the wafer 1. The side opposite to the back surface 1b of the wafer 1 may be referred to as the front surface 1a side of the wafer 1.

  The front surface 1a side of the wafer 1 is divided into a plurality of regions by a plurality of dividing lines 7 arranged in a grid. Devices 5 such as ICs (integrated circuits) and LSIs (Large Scale Integrations) are formed in the respective partitioned areas. For example, when the wafer 1 is processed along the dividing line 7, the wafer 1 is divided into a plurality of device chips.

  Next, each step of the method for manufacturing a recycled wafer will be described. In this embodiment, a recycled wafer is manufactured by removing the circuit layer 3 from the front surface 1a side of the wafer 1. The circuit layer 3 to be removed may be in the state of being formed (that is, partially completed) or may be in the state of after being formed (that is, completed).

  In the method for manufacturing a reclaimed wafer, first, the protective member 9 is attached to the back surface 1b of the wafer 1 using a tape attaching device or the like arranged outside the processing device 2 (protective member attaching step (S10)).

  The protection member 9 is a circular resin film having substantially the same size as the wafer 1. The protective member 9 has a base material layer and an adhesive layer, and by adhering the adhesive layer to the back surface 1b of the wafer 1, the protective member 9 and the wafer 1 are integrated. FIG. 4 is a perspective view of the wafer 1 to which the protection member 9 is attached.

  After the protective member attaching step (S10), the wafer 1 integrated with the protective member 9 is accommodated in the first cassette 62 and is transported to the processing apparatus 2. Then, the wafer 1 is transferred to the temporary placement table 68 by the wafer transfer robot 66, and then transferred from the temporary placement table 68 to the chuck table 38 located in the area A by the transfer unit 72.

  After that, the negative pressure of the suction source connected to the chuck table 38 is applied to hold the wafer 1 by suction on the chuck table 38. Next, the turntable 34 is rotated 90 degrees in the direction of the arrow 36 to move the chuck table 38 on which the above-described wafer 1 is placed from the area A to the area B.

  Then, the surface 1a side of the wafer 1 is roughly ground using the above-described rough grinding unit 12 (rough grinding step (S20)). The front surface 1a side of the wafer 1 may be roughly ground without attaching the protective member 9 to the back surface 1b of the wafer 1, and in this case, the protective member attaching step (S10) may be omitted.

  FIG. 5 is a diagram showing the states of the rough grinding step (S20), the finish grinding step (S30), and the final finish grinding step (S40). The finish grinding step (S30) and the final finish grinding step (S40) will be described later.

  In the rough grinding step (S20), the spindle 22 and the chuck table 38 are each rotated in a predetermined direction. Then, the spindle 22 is lowered while supplying a grinding liquid such as pure water to the surface 1a side of the wafer 1, and the first grinding wheel 30-1 is pressed against the surface 3a of the circuit layer 3.

As a result, substantially the entire circuit layer 3 is removed from the wafer 1. In the rough grinding step (S20), the thickness T ₁ (see FIG. 7A) corresponding to the thickness of the circuit layer 3 is removed. The thickness T ₁ is, for example, about 20 μm.

  In the rough grinding step (S20), since the first grinding wheel 30-1 in which the vitrified bond is used as the binder is used, as compared with the case where the electroforming bond grinding wheel is used, the grinding of the circuit layer 3 is accompanied. The grinding wheel is consumed properly, and the self-developing blade of the grinding wheel is generated. Therefore, it is possible to stably grind the wafer 1 without causing the grinding wheel to be crushed or clogged.

  In the rough grinding step (S20), since the surface 1a side of the wafer 1 is ground by the above-mentioned first grinding wheel 30-1, the load on the wafer 1 is lower than in the case of using the electroformed bond grinding wheel. Even then, the wafer 1 can be ground stably.

Therefore, the load on the wafer 1 can be suppressed low, and the fracture layer 1c ₁ (see FIG. 7A) formed on the wafer 1 can be made shallow. As described above, in the rough grinding step (S20), the circuit layer 3 that is harder to grind than the wafer 1 is surely removed, and the thickness of the fracture layer 1c ₁ is larger than that in the case where the electroformed bond grinding wheel is used. Can be thin.

In addition, as shown in Table 1 described later, the number of abrasive grains used in the first grinding wheel 30-1 (that is, # 500 and # 1200) is thinner than that in the case of using the electroformed bond grinding wheel. It corresponds to the upper limit and the lower limit of the grain count of the abrasive grains that can both form the crush layer 1c ₁ and remove the circuit layer 3.

  By the way, in the present embodiment, the rough grinding step (S20) is performed without the preliminary processing step of modifying the circuit layer 3 in order to facilitate the removal of the circuit layer 3. Therefore, since the pre-processing step is not performed, the processing process can be simplified, and the processing time and processing cost can be omitted.

  In the pre-processing step described above, the circuit layer 3 is wet-etched and modified by immersing the wafer 1 in a mixed solution of sulfuric acid and hydrogen peroxide. In this wet etching, the circuit layer 3 may be partially removed.

Next, the process moves to the step of removing the crushed layer 1c ₁ formed in the rough grinding step (S20). In the present embodiment, after the rough grinding step (S20), the front surface 1a side of the wafer 1 is continuously ground (finish grinding step (S30)).

  If the abrasive grains used in the finish grinding step (S30) are too small, grinding will take time. In addition, since the circuit layer 3 that could not be completely removed in the rough grinding step (S20) may partially remain, if too small abrasive grains are used, the abrasive grains may be formed by the metal or resin forming the circuit layer 3. The wafer 1 cannot be properly ground due to clogging.

Furthermore, the finish grinding step if the abrasive grains used in (S30) greater than the abrasive grain used in the rough grinding step (S20), a thick fracture layer 1c than crushing layer 1c ₁ is formed by the rough grinding step (S20) ₂ is formed, which is not preferable.

Therefore, in the finish grinding step of the present embodiment (S30), to remove the fracture layer 1c ₁ using the second grinding wheel 26-2 having a second grinding wheel 30-2 described above. However, in the finish grinding step (S30), a thin fractured layer 1c ₂ is newly formed than crushing layer 1c ₁ to the wafer 1.

  In the finish grinding step (S30), first, the turntable 34 is rotated by 90 degrees in the direction of the arrow 36 so that the chuck table 38 on which the wafer 1 ground in the rough grinding step (S20) is mounted is moved to the area B. To area C from.

  Also in the finish grinding step (S30), the chuck table 38 and the spindle 22 of the finish grinding unit 16 are each rotated in predetermined directions. Then, the spindle 22 is lowered while supplying a grinding liquid such as pure water to the front surface 1a side of the wafer 1, and the second grinding wheel 30-2 is pressed against the front surface 1a side of the wafer 1.

As a result, in the finishing grinding step (S30), the surface 1a side of the wafer 1 is removed by the thickness T ₂ (see FIG. 7A). The thickness T ₂ substantially corresponds to the depth of the crush layer 1c ₁ formed in the rough grinding step (S20) and is, for example, 5 μm.

  Even in the finish grinding step (S30), since vitrified bond is used as the bonding material of the second grinding wheel 30-2, spontaneous cutting of the grinding wheel is likely to occur. Therefore, the grinding wheel is less likely to be clogged or clogged, and the wafer 1 can be ground stably.

Thus, in the finish grinding step (S30), while removing the remaining portion and crushing layer 1c ₁ of the circuit layer 3, and it can form a thin fractured layer 1c ₂ than crushing layer 1c _1. In addition, as shown in Table 2 described later, the numbers of the abrasive grains used in the second grinding wheel 30-2 (that is, # 2000 and # 5000) are appropriate for grinding with reduced clogging during grinding. It corresponds to the upper limit and the lower limit of the grain count of the abrasive grain, which can achieve both execution and formation of the crush layer 1c ₂ thinner than the crush layer 1c ₁ .

  Further, compared with the case where the polishing step (S50) is performed after the rough grinding step (S20), the finish grinding step (S30) is performed after the rough grinding step (S20), and then the polishing step (S50) is performed. It is possible to shorten the time required to manufacture the reclaimed wafer by performing the method.

In the present embodiment, the surface 1a side of the wafer 1 is continuously ground after the finish grinding step (S30) and before the polishing step (S50) described later (final finish grinding step (S40)). In the final finish grinding step (S40), to remove the fracture layer 1c ₂ using the third grinding wheel 26-3 having a third grinding wheel 30-3 described above.

If the abrasive grains used in the final finishing grinding step (S40) are too small, the grinding wheel will be clogged and the grinding will take time. Further, the abrasive grains used in the finish grinding step (S30) is finish grinding step is greater than the abrasive grain used in the (S30), a final finish grinding step (S40) thick fracture layer 1c than crushing layer 1c ₂ formed by _{Since 3} is formed, it is not preferable.

Therefore, in the final finish grinding step of the present embodiment (S40), to remove the fracture layer 1c ₂ using the third grinding wheel 30-3 described above. In the final finish grinding step (S40), although thin crushing layer 1c ₃ than crushing layer 1c ₂ on the surface 1a of the wafer 1 is newly formed, the thickness of the crushing layer is thinnest fracture layer 1c _3, Next, the crush layer 1c ₂ is the second thinnest, and the crush layer 1c ₁ is the thickest. Therefore, in the final finish grinding step (S40), the thickness of the fractured layer remaining on the surface 1a side of the wafer 1 can be made thinner than the thickness of the fractured layer after the finish grinding step (S30).

  In general, the removal amount of the wafer 1 per unit time by grinding is larger than the removal amount of the wafer 1 per unit time by polishing. Therefore, by performing the final finish grinding step (S40), it is possible to reduce the time required for manufacturing the regenerated wafer as compared with the case where the final finish grinding step (S40) is omitted and the polishing step (S50) described later is performed. .

  That is, compared with the case where the rough grinding step (S20), the finish grinding step (S30) and the polishing step (S50) are sequentially performed, the rough grinding step (S20) is followed by the finish grinding step (S30) and the final finish grinding step. Performing the step (S40) and the polishing step (S50) in sequence can reduce the time required to manufacture the recycled wafer.

  Of course, even if the finishing grinding step (S30) and the final finishing grinding step (S40) are performed after the rough grinding step (S20), compared to the case where the circuit layer 3 is ground with the electroformed bond grinding wheel. The crushed layer can be made sufficiently thin. Therefore, the removal amount of the wafer 1 can be reduced as compared with the case where an electroformed bond grinding wheel is used.

  In the final finishing grinding step (S40), first, the turntable 34 is rotated 90 degrees in the direction of the arrow 36 to move the chuck table 38 on which the wafer 1 is placed from the area C to the area D.

  Also in the final finish grinding step (S40), the chuck table 38 and the spindle 22 are each rotated in predetermined directions. Then, the spindle 22 is lowered while supplying a grinding liquid such as pure water to the front surface 1a side of the wafer 1, and the third grinding wheel 30-3 is pressed against the front surface 1a side of the wafer 1.

As a result, in the final finishing grinding step (S40), the surface 1a side of the wafer 1 is removed by the thickness T ₃ (see FIG. 7A). The thickness T ₃ substantially corresponds to the depth of the crush layer 1c ₂ formed in the finish grinding step (S30) and is, for example, 5 μm.

  Also in the final finish grinding step (S40), since vitrified bond is used as the bonding material of the third grinding wheel 30-3, the self-developing blade of the grinding wheel occurs. Therefore, the grinding wheel is less likely to be clogged or clogged, and the wafer 1 can be ground stably.

In addition, as shown in Table 3 described later, the numbers of the abrasive grains used for the third grinding wheel 30-3 (that is, # 6000 and # 8000) are suitable for grinding with reduced clogging during grinding. It corresponds to the upper limit and the lower limit of the grain count of the abrasive grains that can achieve both formation of the crush layer 1c ₃ thinner than the crush layer 1c ₂ .

In the present embodiment, after the final finish grinding step, the surface 1a of the wafer 1 chemically mechanically polished to remove the fracture layer 1c ₃ remaining on the surface 1a of the wafer 1 (polishing step (S50)).

By performing polishing step (S50), it can be removed crushing layer 1c ₃ which remained, thereby, a fracture layer on the surface 1a side can be completely removed. The polishing step (S50) is performed using the polishing unit 42 described above. FIG. 6 is a diagram showing a state of the polishing step (S50).

  In the polishing step (S50), first, the back surface 1b side of the wafer 1 taken out from the processing apparatus 2 is sucked and held by the chuck table 38 of the polishing apparatus. After that, the chuck table 38 and the spindle 44 are respectively rotated in predetermined directions. Then, the spindle 44 is lowered while supplying the polishing liquid to the front surface 1a side of the wafer 1 through the polishing liquid supply passage 54, and the polishing pad 52 is pressed against the front surface 1a side of the wafer 1.

In the polishing step (S50), the surface 1a side of the wafer 1 is removed by the thickness T ₄ (see FIG. 7A) by the chemical action and the mechanical action of the abrasive grains, the polishing liquid, and the wafer 1. The thickness T ₄ is, for example, a predetermined thickness of 2 μm or more and 3 μm or less.

  FIG. 7A is a diagram showing the removal amount in each of the rough grinding step (S20), the finish grinding step (S30), the final finish grinding step (S40) and the polishing step (S50), and FIG. [FIG. 6B] is a perspective view of the regenerated wafer 1c after the polishing step (S50). The surface 1a of the wafer 1 after completion of the polishing step (S50) becomes the reclaimed surface 1d of the reclaimed wafer 1c.

  Further, FIG. 8 shows a flow chart of the method for manufacturing the recycled wafer 1c in the present embodiment. As described above, in the present embodiment, by using the first grinding wheel 30-1, the fracture layer can be made shallower than in the case of using the electroformed bond grinding wheel, so that the removal amount of the wafer 1 can be reduced. .

For example, when a pipe-shaped electroformed grinding blade is used, the fracture layer has a depth of 70 μm, and the wafer 1 must be removed from the surface 1a by at least 80 μm. However, in the present embodiment, for example, since the total of about 12 μm of the crushed layer 1c ₁ (about 5 μm), the crushed layer 1c ₂ (about 5 μm) and the crushed layer 1c ₃ (about 2 μm) is removed, the removal amount of the wafer 1 is reduced. It can be reduced.

  Next, regarding the first, second, and third grinding wheels 30-1, 30-2, and 30-3, which are solid grinding wheels using vitrified bonds as the binder, the grain size of the abrasive grains and the grinding result. Tables 1 to 3 show the relationship with. Table 1 shows the relationship between the grain size of the abrasive grains and the grinding result in the rough grinding step (S20).

In # 400 having the largest maximum abrasive grain diameter in Table 1, the crushed layer 1c ₁ remained deeper than in # 500 or more and # 1200 or less. Further, in # 1500 in which the maximum diameter of the abrasive grains is the smallest in Table 1, the metal of the circuit layer 3 sticks to the first grinding wheel 30-1 to cause clogging or crushing, The load on the first grinding wheel 30-1 increased and the circuit layer 3 could not be properly ground.

Table 2 shows the relationship between the abrasive grain size and the grinding result in the finish grinding step (S30). In # 1500 in which the maximum diameter of the abrasive grains is the largest in Table 2, the crushed layer 1c ₂ remained deeper than in # 2000 or more and # 5000 or less. Further, in # 6000 in Table 2 where the maximum diameter of the abrasive grains is the smallest, the second grinding wheel 30-2 is clogged or crushed, and the load on the second grinding wheel 30-2 increases. Wafer 1 could not be ground properly.

Table 3 shows the relationship between the abrasive grain size and the grinding result in the final finish grinding step (S40). In # 5000 having the largest maximum abrasive grain diameter in Table 3, the fractured layer 1c ₃ remained deeper than in # 6000 or more and # 8000 or less. Further, in # 10000 in Table 3 where the maximum diameter of the abrasive grains is the smallest, the third grinding wheel 30-3 is clogged or crushed, and the load on the third grinding wheel 30-3 increases. Wafer 1 could not be ground properly.

  Next, the first grinding wheel 30-1 which is a solid segment wheel using vitrified bond and the pipe-shaped electroformed grinding blade using electroformed bond were compared. Table 4 shows the relationship between the grain size of the abrasive grains in the rough grinding step (S20) and the grinding result.

With regard to the pipe-shaped electroformed grinding blade, good results were not obtained with any of # 400, # 800 and # 1000. In # 400, the crush layer was deeper than the crush layer 1c ₁ when the first grinding wheel 30-1 was used.

Further, in # 800, the crush layer became deeper than the crush layer 1c ₁ , and the electroformed grinding blade was damaged due to the high load on the pipe-shaped electroformed grinding blade. In addition, with # 1000, the electroformed grinding blade was clogged or crushed, the load on the electroformed grinding blade increased, and the circuit layer 3 could not be properly ground.

  As a result, as the first grinding wheel 30-1, # 500 or more and # 1200 or less abrasive grains are suitable, and as the second grinding wheel 30-2, # 2000 or more and # 5000 or less abrasive grains are suitable. It can be said that abrasive grains of # 6000 or more and # 8000 or less are suitable as the third grinding stone 30-3. Further, regarding the bonding material and shape of the first grinding wheel 30-1, it can be said that the vitrified bond and the solid segment wheel are more suitable than the pipe-shaped electroformed grinding blade.

  If the grinding wheel is a solid segment wheel, a grinding wheel using a vitrified bond as a binder is easier to self-blade than a grinding wheel using an electroformed bond. The load per area can be reduced and the crush layer can be made thinner.

  Next, a second embodiment will be described. In the second embodiment, after the finish grinding step (S30), the final finish grinding step (S40) is omitted and the polishing step (S50) is performed. For example, the finishing grinding step (S30) is performed using the second grinding wheel 30-2 having # 5000 abrasive grains, and then the polishing step (S50) is performed using the polishing pad 52.

  In the second embodiment, the time required to process the wafer 1 is longer than in the first embodiment, but since the first grinding wheel 30-1 is used also in the second embodiment, the electroformed bond grinding is performed. The removal amount of the wafer 1 can be reduced by making the fracture layer shallower than in the case of using a grindstone.

  In addition, the structures, methods, and the like according to the above-described embodiments can be appropriately modified and implemented without departing from the scope of the object of the present invention.

1 wafer 1a surface 1b backside 1c _{1, 1c} 2, 1c ₃ crushing layer 1d reproduction wafer 1e reproduction surface 2 processing unit 3 four stage circuit layer 3a surface 5 device 6 support structure 7 division lines 8 and 10 the rail 9 protective member 12 Rough grinding unit 14 Rough grinding unit feed mechanism 16 Finish grinding unit 18 Finish grinding unit feed mechanism 20 Spindle housing 22 Spindle 24 Wheel mount 26-1 First grinding wheel 26-2 Second grinding wheel 26-3 Third grinding Wheel 28 Wheel base 30-1 First grinding wheel 30-2 Second grinding wheel 30-3 Third grinding wheel 30a Inner peripheral side surface 30b Outer peripheral side surface 30c First side surface 30d Second side surface 30e Top surface 30f Adhesive 32 motor 34 turntable 36 arrow 38 char Table 38a Holding surface 40 Final finishing grinding unit 42 Polishing unit 44 Spindle 46 Wheel mount 48 Polishing wheel 50 Base 52 Polishing pad 54 Polishing liquid supply path 62 First cassette 64 Second cassette 66 Wafer transfer robot 68 Temporary table 70 Spinner Cleaning Unit 72 Transfer Unit 74 Support Column 76 Guide Rail 78 Moving Block 80 Support Rod 82 Arm Part 84 Suction Pads T ₁ , T ₂ , T ₃ , T ₄ Thickness

Claims (4)

A method for producing a regenerated wafer, in which the circuit layer is removed from the front surface side of the wafer during the formation of the circuit layer on the surface of the wafer or after the circuit layer is formed on the surface, ,
A first grinding wheel in which a plurality of first grinding wheels having abrasive grains of # 500 or more and # 1200 or less fixed by vitrified bonds are annularly arranged is used to grind the circuit layer on the front surface side of the wafer. A grinding step,
After the rough grinding step, a second grinding wheel in which a plurality of second grinding wheels to which abrasive grains of # 2000 or more and # 5000 or less are fixed by vitrified bonds are annularly arranged is used to move the front surface side of the wafer. Finishing grinding step to grind,
And a polishing step of chemically mechanically polishing the front surface side of the wafer to remove a fracture layer remaining on the front surface side of the wafer after the finish grinding step. Method.   After the finish grinding step and before the polishing step, a third grinding wheel in which a plurality of third grinding wheels having abrasive grains of # 6000 or more and # 8000 or less fixed by vitrified bonds are annularly arranged, The method further comprises a final finishing grinding step of grinding the front surface side of the wafer and making the thickness of the crush layer remaining on the front surface side of the wafer smaller than the thickness of the crush layer after the finish grinding step. The method for manufacturing a reclaimed wafer according to claim 1, wherein   The method for manufacturing a recycled wafer according to claim 2, wherein the first, second, and third grinding wheels are solid segment wheels.   4. The method of manufacturing a reclaimed wafer according to claim 1, wherein the rough grinding step is performed without a preliminary processing step of etching and modifying the circuit layer.