Grinding device and sensor unit

Abstract

To shorten setup time in a grinding device.SOLUTION: Measurement light L is emitted to a gap D between a grinding surface 771 of a grinder 77 of a grinding mechanism 70 at a standby position and a holding surface 22 of a chuck table 20, the measurement light L having a wider width T2 than a distance T1 of the gap D, the distance T1 of the gap D is determined on the basis of a light amount of the measurement light L that has passed through the gap D, and an origin point height of the grinding mechanism 70 is determined on the basis of the distance T1. Thus, in the present embodiment, setup of determining the origin point height of the grinding mechanism 70 can be performed while the grinding mechanism 70 remains at the standby position without elevating or lowering the grinding mechanism 70 including the grinder 77. Accordingly, the setup can be completed in a short time.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a grinding machine and a sensor unit. [Background technology]

[0002] In a grinding machine that grinds wafers, a setup is performed to determine the height of the grinding wheel when its underside contacts the holding surface of the chuck table. Then, using the height determined during the setup as a reference, the grinding wheel is moved (lowered) at high speed to the grinding start position above the wafer. This grinding start position is a position where the grinding wheel does not contact the wafer, but is close to the wafer. After that, an air cut is performed, and the grinding process is carried out using the grinding wheel. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-144327 [Patent Document 2] Japanese Patent Publication No. 2021-154396 Summary of the Invention [Problem to be solved by the invention]

[0004] As disclosed in Patent Documents 1 and 2, the above-mentioned setup is performed using a block gauge placed on the holding surface while raising and lowering the grinding wheel, or using a sensor. However, in either case, it takes time to complete the setup because the grinding wheel needs to be raised and lowered.

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to reduce setup time in a grinding machine. [Means for solving the problem]

[0006] The grinding apparatus of the present invention (the present grinding apparatus) is a grinding apparatus comprising a chuck table that holds a wafer by a holding surface, a grinding mechanism that grinds the wafer by the grinding surface at the tip of a ring-shaped grinding wheel, a lifting mechanism that raises and lowers the chuck table or the grinding mechanism, and a height recognition unit that recognizes the height of the chuck table or the grinding mechanism raised and lowered by the lifting mechanism, and further includes a measuring light beam having a width wider than the gap, directed toward the gap between the holding surface and the grinding surface when the chuck table and the grinding mechanism are in a predetermined positional relationship. and a light receiving section that receives the measurement light that has passed through the gap with a portion of the light being blocked by the grinding wheel and the chuck table; a distance recognition section that recognizes the distance of the gap based on the amount of light received by the light receiving section; and a calculation section that calculates the height of the chuck table or the grinding mechanism that is raised and lowered by the lifting mechanism when the grinding wheel comes into contact with the holding surface by subtracting the distance of the gap recognized by the distance recognition section from the height recognized by the height recognition section when the gap is formed.

[0007] The grinding apparatus may include a light-projecting unit elevating mechanism that elevates the light-projecting unit, and a light-receiving unit elevating mechanism that elevates the light-receiving unit.

[0008] The sensor unit provided in the grinding apparatus may include a base that is installed in the grinding apparatus, and the light projecting portion and the light receiving portion that are provided on the base. [Effects of the Invention]

[0009] In this grinding device, a measurement light beam with a width wider than the gap between the grinding surface of the grinding wheel of the grinding mechanism and the holding surface of the chuck table is projected, and the gap distance is determined based on the amount of measurement light that passes through the gap. Based on this distance, the height (origin height) of the grinding mechanism or chuck table when the grinding wheel contacts the holding surface is determined. In other words, in this grinding device, setup can be performed to determine the origin height of the grinding mechanism or chuck table without raising or lowering the grinding mechanism or chuck table. Therefore, setup can be completed in a short time. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 2 is a perspective view showing the configuration of a grinding device. [Figure 2] FIG. 10 is a cross-sectional view showing a setup operation. [Figure 3] FIG. 10 is a cross-sectional view showing a setup operation. [Figure 4] FIG. 10 is a perspective view showing another sensor unit. DETAILED DESCRIPTION OF THE INVENTION

[0011] 1, a grinding apparatus 1, which is a processing apparatus according to this embodiment, is an apparatus that grinds a wafer 100 using an annular grinding wheel 77. The grinding apparatus 1 includes a rectangular parallelepiped base 10, a column 11 extending upward, and a control unit 7 that controls each component of the grinding apparatus 1.

[0012] Wafer 100 is, for example, a circular semiconductor wafer and includes a front surface 101 and a back surface 102. Front surface 101 of wafer 100, which faces downward in FIG. 1, holds multiple devices and is protected by the attachment of protective tape 103. Back surface 102 of wafer 100 is the processing surface on which grinding is performed.

[0013] An opening 13 is provided on the upper surface side of the base 10. A wafer holding mechanism 30 is disposed within the opening 13. The wafer holding mechanism 30 includes a chuck table 20 that holds the wafer 100 by a holding surface 22, and a table rotation mechanism 28 that supports and rotates the chuck table 20.

[0014] The chuck table 20 includes a porous member 21 and a frame 23 that houses the porous member 21 so that the upper surface of the porous member 21 is exposed. The upper surface of the porous member 21 is a holding surface 22 that holds the wafer 100 by suction. A frame surface 24, which is the upper surface of the frame 23, is formed to be flush with the holding surface 22. In the chuck table 20, the holding surface 22 is connected to a suction source (not shown), so that the wafer 100 can be held by the holding surface 22 by suction.

[0015] The table rotation mechanism 28 supports the chuck table 20 from below. The table rotation mechanism 28 is configured to rotate the chuck table 20 around the center of the holding surface 22 as an axis.

[0016] A cover plate 39 that moves along the Y-axis direction together with the chuck table 20 is provided around the periphery of the chuck table 20. A bellows cover 12 that expands and contracts in the Y-axis direction is connected to the cover plate 39. A Y-axis direction moving mechanism 40 is disposed below the wafer holding mechanism 30.

[0017] The Y-axis direction moving mechanism 40 moves the chuck table 20 and the grinding mechanism 70 relatively in the Y-axis direction, which is a direction parallel to the holding surface 22. In this embodiment, the Y-axis direction moving mechanism 40 is configured to move the wafer holding mechanism 30 including the chuck table 20 in the Y-axis direction relative to the grinding mechanism 70.

[0018] The Y-axis direction movement mechanism 40 includes a pair of Y-axis guide rails 42 parallel to the Y-axis direction, a Y-axis movement table 45 that slides on these Y-axis guide rails 42, a Y-axis ball screw 43 parallel to the Y-axis guide rails 42, a Y-axis motor 44 connected to the Y-axis ball screw 43, and a holder 41 that holds these.

[0019] The Y-axis moving table 45 is slidably installed on the Y-axis guide rail 42. A nut portion (not shown) is fixed to the underside of the Y-axis moving table 45. A Y-axis ball screw 43 is threadedly engaged with this nut portion. The Y-axis motor 44 is connected to one end of the Y-axis ball screw 43.

[0020] In the Y-axis direction moving mechanism 40, the Y-axis motor 44 rotates the Y-axis ball screw 43, thereby moving the Y-axis moving table 45 in the Y-axis direction along the Y-axis guide rails 42. The table rotation mechanism 28 of the wafer holding mechanism 30 is placed on the Y-axis moving table 45. Therefore, as the Y-axis moving table 45 moves in the Y-axis direction, the wafer holding mechanism 30 including the chuck table 20 moves in the Y-axis direction.

[0021] In this embodiment, the wafer holding mechanism 30 including the chuck table 20 is moved along the Y-axis direction by the Y-axis movement mechanism 40 between a holding position on the -Y-axis side for holding the wafer 100 by the holding surface 22 and a processing position on the +Y-axis side where the wafer 100 is ground.

[0022] Furthermore, a column 11 is erected on the rear (+Y direction side) of the base 10. In front of the column 11, a grinding mechanism 70 for grinding the wafer 100 and an elevating mechanism 50 are provided.

[0023] The lifting mechanism 50 moves the chuck table 20 and the grinding mechanism 70 relatively in the Z-axis direction (grinding feed direction) perpendicular to the holding surface 22. In this embodiment, the lifting mechanism 50 is configured to raise and lower the grinding mechanism 70 relative to the chuck table 20.

[0024] The lifting mechanism 50 includes a pair of Z-axis guide rails 51 parallel to the Z-axis direction, a Z-axis moving table 53 that slides on the Z-axis guide rails 51, a Z-axis ball screw 52 parallel to the Z-axis guide rails 51, a Z-axis motor 54 connected to the Z-axis ball screw 52, ​​a Z-axis encoder 55 for detecting the amount of rotation (number of rotations and rotation angle) of the Z-axis ball screw 52, ​​and a holder 56 attached to the Z-axis moving table 53. The holder 56 supports a grinding mechanism 70.

[0025] Z-axis moving table 53 is slidably installed on Z-axis guide rail 51. A nut portion (not shown) is fixed to Z-axis moving table 53. Z-axis ball screw 52 is threadedly engaged with this nut portion. Z-axis motor 54 is connected to one end of Z-axis ball screw 52.

[0026] In the lifting mechanism 50, the Z-axis motor 54 rotates the Z-axis ball screw 52, ​​thereby moving the Z-axis moving table 53 in the Z-axis direction along the Z-axis guide rail 51. As a result, the holder 56 attached to the Z-axis moving table 53 and the grinding mechanism 70 supported by the holder 56 also move in the Z-axis direction together with the Z-axis moving table 53.

[0027] Z-axis encoder 55 is rotated by Z-axis motor 54 rotating Z-axis ball screw 52, ​​and is able to recognize the amount of rotation (number of rotations and rotation angle) of Z-axis ball screw 52. In this embodiment, control unit 7 recognizes the amount of rotation of Z-axis ball screw 52 recognized by Z-axis encoder 55, and based on the recognition result, is able to detect the height of grinding mechanism 70 moved in the Z-axis direction (for example, the height of grinding surface 771 of grinding wheel 77). In this way, Z-axis encoder 55 functions as a height recognition unit that recognizes the height of grinding mechanism 70 raised and lowered by lifting mechanism 50.

[0028] In this embodiment, until the start of grinding, the grinding mechanism 70 is placed, for example, by the lifting mechanism 50, at a position in the Z-axis direction (standby position) where the chuck table 20 and the grinding mechanism 70 have a predetermined positional relationship. The predetermined positional relationship between the chuck table 20 and the grinding mechanism 70 is, for example, a positional relationship where the grinding surface 771 of the grinding wheel 77 and the chuck table 20 come into contact with measurement light projected from a light projecting unit 81 of a sensor unit 80 (described later).

[0029] The grinding mechanism 70 grinds the wafer 100 with a grinding surface 771 (see FIG. 2) at the tip of a ring-shaped grinding wheel 77. The grinding mechanism 70 includes a spindle housing 71 fixed to the holder 56, a spindle 72 rotatably held in the spindle housing 71, a spindle motor 73 that rotates the spindle 72, a wheel mount 74 attached to the lower end of the spindle 72, and a grinding wheel 75 supported by the wheel mount 74.

[0030] The spindle housing 71 is held by the holder 56 so as to extend in the Z-axis direction. The spindle 72 extends in the Z-axis direction so as to be perpendicular to the holding surface 22 of the chuck table 20, and is rotatably supported by the spindle housing 71.

[0031] The spindle motor 73 is connected to the upper end side of the spindle 72. The spindle motor 73 rotates the spindle 72 around an axis extending in the Z-axis direction.

[0032] The wheel mount 74 is formed in a disk shape and is fixed to the lower end (tip) of the spindle 72. The wheel mount 74 supports the grinding wheel 75.

[0033] The grinding wheel 75 is formed to have an outer diameter that is approximately the same as the outer diameter of the wheel mount 74. The grinding wheel 75 is provided with an annular wheel base 76 made of a metal material. A plurality of grinding stones 77 arranged in a ring shape are fixed to the outer periphery of the lower surface of the wheel base 76 around the entire circumference. The grinding stones 77 are rotated together with the spindle 72 by the spindle motor 73, and grind the back surface 102 of the wafer 100 held on the chuck table 20 with a grinding surface (lower surface) 771 at the tip of each grinding stone.

[0034] The grinding apparatus 1 also has a sensor unit 80 near the chuck table 20. The sensor unit 80 is used to perform setup to recognize the height of the grinding mechanism 70 (for example, the height of the grinding surface 771) when the grinding surface 771 of the grinding wheel 77 comes into contact with the holding surface 22 of the chuck table 20.

[0035] The sensor unit 80 has a light-projecting unit 81 and a light-receiving unit 83 that are arranged to face each other with the chuck table 20 in between. The light-projecting unit 81 is arranged on the cover plate 39 on the +Y direction side of the chuck table 20. The light-projecting unit 81 projects measurement light toward the light-receiving unit 83 so that the light passes through, for example, the center of the holding surface 22. The light-receiving unit 83 is arranged on the cover plate 39 on the -Y direction side of the chuck table 20, and receives the measurement light projected from the light-projecting unit 81.

[0036] Furthermore, the light-projecting unit 81 is supported on the cover plate 39 by a light-projecting unit lifting mechanism 82 that raises and lowers the light-projecting unit 81. Furthermore, the light-receiving unit 83 is supported on the cover plate 39 by a light-receiving unit lifting mechanism 84 that raises and lowers the light-receiving unit 83. The light-projecting unit 81 and the light-receiving unit 83 can be raised and lowered in the Z-axis direction by the light-projecting unit lifting mechanism 82 and the light-receiving unit lifting mechanism 84, respectively. The light-projecting unit lifting mechanism 82 and the light-receiving unit lifting mechanism 84 are, for example, cylinder-type lifting mechanisms. The light projecting unit 81 and the light receiving unit 83 may be provided with a cover to prevent processing debris from adhering thereto.

[0037] The control unit 7 includes a CPU that performs arithmetic processing according to a control program, a storage medium such as a memory, etc. For example, the control unit 7 controls the above-mentioned components of the grinding apparatus 1 to perform grinding processing on the wafer 100. The control unit 7 also includes a distance recognition unit 8 and a calculation unit 9, which are used to set up the grinding mechanism 70 using the sensor unit 80 before grinding the wafer 100.

[0038] The setup of the grinding mechanism 70 controlled by the control unit 7 will now be described. In the setup according to this embodiment, the control unit 7 first uses the Y-axis direction moving mechanism 40 to place the chuck table 20 at the processing position on the +Y direction side. As a result, the grinding wheel 77 is positioned above the center of the chuck table 20, as shown in FIG. 2. In addition, a light-projecting unit 81 and a light-projecting unit elevating mechanism 82 are disposed inside the grinding wheel 75 (grinding wheel 77), and a light-receiving unit 83 and a light-receiving unit elevating mechanism 84 are disposed outside the grinding wheel 75.

[0039] Next, the control unit 7 controls the light-projecting unit lifting mechanism 82 and the light-receiving unit lifting mechanism 84 to position the light-projecting unit 81 and the light-receiving unit 83 in the Z-axis direction at predetermined measurement positions. The predetermined measurement position of the light-projecting unit 81 is, for example, a position where the measurement light can be irradiated into the gap D between the grinding surface 771 of the grinding wheel 77 of the grinding mechanism 70, which is positioned at the standby position and has a predetermined positional relationship with the chuck table 20, and the holding surface 22 of the chuck table 20, so that the measurement light comes into contact with the grinding wheel 77 and the chuck table 20. In this case, the predetermined measurement position of the light-receiving unit 83 is a position where the measurement light projected from the light-projecting unit 81 and passing through the gap D can be received.

[0040] Next, the control unit 7 projects measurement light L from the light-projecting unit 81 of the sensor unit 80 toward the light-receiving unit 83. As shown in Fig. 2, the light-projecting unit 81 projects measurement light L having a width T2 wider than the distance T1 of the gap D toward a gap D between the grinding surface 771 of the grinding wheel 77 of the grinding mechanism 70 and the holding surface 22 of the chuck table 20 when the chuck table 20 and the grinding mechanism 70 are in a predetermined positional relationship. Then, the light-receiving unit 83 receives the measurement light L that has passed through the gap D between the grinding surface 771 and the holding surface 22 with part of the light being blocked by the grinding wheel 77 and the chuck table 20.

[0041] Thereafter, the distance recognition unit 8 of the control unit 7 recognizes the distance T1 of the gap D between the grinding surface 771 and the holding surface 22 based on the amount of light received by the light receiving unit 83. That is, the amount of light received by the light receiving unit 83 decreases as the distance T1 of the gap D between the grinding surface 771 and the holding surface 22 decreases. Therefore, the distance recognition unit 8 can obtain the distance T1 of the gap D by, for example, comparing the amount of light received by the light receiving unit 83 when the measurement light L is received in a partially blocked state after passing through the gap D with the amount of light received by the light receiving unit 83 when the measurement light L is received in an unblocked state.

[0042] For example, if the width T2 of the measurement light L is 10 mm, the amount of light blocked by the grinding wheel 77 is 1.5 mm, and the amount of light blocked by the holding surface 22 is 3.5 mm, the distance T1 of the gap D is 5 mm.

[0043] Next, the control unit 7 controls the Z-axis encoder 55 of the lifting mechanism 50 to recognize the height of the grinding mechanism 70 when the gap D is formed between the grinding surface 771 and the holding surface 22 (i.e., the height of the standby position). Then, the calculation unit 9 of the control unit 7 calculates the origin height of the grinding mechanism 70 by subtracting the distance T1 of the gap D recognized by the distance recognition unit 8 from the height of the grinding mechanism 70 recognized by the Z-axis encoder 55 when the gap D is formed, and stores this origin height. Note that the origin height of the grinding mechanism 70 is the height of the grinding mechanism 70 when the grinding surface 771 of the grinding wheel 77 contacts the holding surface 22 of the chuck table 20. This completes the setup of the grinding mechanism 70.

[0044] As described above, in the setup of this embodiment, measurement light L having a width T2 wider than the distance T1 of the gap D is projected into the gap D between the grinding surface 771 of the grinding wheel 77 of the grinding mechanism 70, which is positioned at the standby position and in a predetermined positional relationship with the chuck table 20, and the holding surface 22 of the chuck table 20. The distance T1 of the gap D is determined based on the amount of measurement light L that passes through the gap D, and the origin height of the grinding mechanism 70 is determined based on this distance T1. That is, in this embodiment, setup for determining the origin height of the grinding mechanism 70 can be performed while the grinding mechanism 70 is positioned at the standby position, without raising or lowering the grinding mechanism 70 including the grinding wheel 77. This makes it possible to complete the setup in a short time.

[0045] In this embodiment, during setup, the light-projecting unit 81 and the light-projecting unit elevating mechanism 82 are arranged inside the grinding wheel 75 (grinding stone 77), and the light-receiving unit 83 and the light-receiving unit elevating mechanism 84 are arranged outside the grinding wheel 75. In this regard, the light-projecting unit 81 and the light-projecting unit elevating mechanism 82 may be arranged outside the grinding wheel 75, and the light-receiving unit 83 and the light-receiving unit elevating mechanism 84 may be arranged inside the grinding wheel 75.

[0046] 1, the diameter of the grinding wheel 75 (grinding stone 77) is approximately the same size as the chuck table 20. In this regard, the diameter of the grinding wheel 75 (grinding stone 77) of the grinding mechanism 70 may be large enough to fit between the light-projecting unit 81 and the light-receiving unit 83, and may be smaller than the radius of the holding surface 22 of the chuck table 20, for example, as shown in FIG.

[0047] Such a grinding wheel 77 is provided, for example, in a grinding mechanism 70 for TAIKO grinding of a wafer 100. In this case, the light projecting unit 81 and the light receiving unit 83 are arranged outside the grinding wheel 75 so as to sandwich the grinding wheel 75 during setup. Even in this case, the distance T1 of the gap D can be calculated based on the amount of measurement light L (amount of light received by the light receiving unit 83) that passes through the gap D between the grinding surface 771 of the grinding wheel 77 and the holding surface 22 of the chuck table 20, and the origin height of the grinding mechanism 70 can be calculated based on this distance T1 without raising or lowering the grinding mechanism 70.

[0048] In addition, in this embodiment, as shown in Figure 1, the light-emitting unit 81 and the light-receiving unit 83 of the sensor unit 80 are arranged on the cover plate 39 of the grinding device 1 via a light-emitting unit lifting mechanism 82 and a light-receiving unit lifting mechanism 84, respectively.

[0049] In this regard, the sensor unit 80 may be configured to be detachable from the grinding apparatus 1. In this case, the sensor unit 80 includes, for example, as shown in FIG. 4 , the light-projecting unit 81 and the light-receiving unit 83 described above, as well as a base 85 that is installed (placed) on the cover plate 39 of the grinding apparatus 1. The base 85 has a substantially semicircular arc plate shape and can be disposed outside the chuck table 20 so as to follow the outer periphery of the chuck table 20. The light-projecting unit 81 and the light-receiving unit 83 are provided on both ends of the base 85. The bottom surface of the base 85 serves as a support surface that is placed on the cover plate 39 of the grinding apparatus 1.

[0050] In this configuration, during setup, the sensor unit 80 is placed in a predetermined orientation on the cover plate 39, which does not move relatively to the chuck table 20, by an operator or a carrier device (not shown), as shown in Fig. 4. In this way, the sensor unit 80 is provided in the grinding apparatus 1 so that it can be controlled by the control unit 7. 2, the light-projecting unit 81 is disposed on the +Y direction side of the chuck table 20 so as to be able to project measurement light that passes through the center of the holding surface 22 in the -Y direction. The light-receiving unit 83 is disposed on the -Y direction side of the chuck table 20 so as to be able to receive the measurement light projected from the light-projecting unit 81.

[0051] 2, this configuration also makes it possible to determine the origin height of the grinding mechanism 70 without raising or lowering the grinding mechanism 70. Furthermore, in this configuration, the sensor unit 80 can be attached and detached to the grinding apparatus 1, so that it is possible to perform setup for multiple grinding apparatuses 1 using one sensor unit 80.

[0052] 2, in this embodiment, the light receiving unit 83 receives the measurement light L that passes through the gap D between the grinding surface 771 and the holding surface 22, with part of the light being blocked by the grinding wheel 77 and the chuck table 20. In this case, the light receiving unit 83 receives part of the measurement light L until the descending grinding wheel 77 contacts the holding surface 22, and when the grinding wheel 77 contacts the holding surface 22, the amount of light received by the light receiving unit 83 becomes substantially zero. Therefore, the distance T1 of the gap D can be accurately determined based on the amount of light received by the light receiving unit 83. In this regard, the light receiving unit 83 may receive the measurement light L that has passed through the gap D between the grinding surface 771 and the holding surface 22 while being partially shielded by the member that is raised and lowered by the lifting mechanism 50, i.e., the grinding wheel 77. In this case, the measurement position of the light projecting unit 81 is, for example, a position where the lower end of the measurement light passes directly above the holding surface 22 of the chuck table 20.

[0053] In addition, in this embodiment, the lifting mechanism 50 is configured to lift and lower the grinding mechanism 70 relative to the chuck table 20. In this regard, the lifting mechanism of this embodiment may be configured to lift and lower the chuck table 20 relative to the grinding mechanism 70.

[0054] That is, the lifting mechanism of this embodiment may be configured to lift or lower the chuck table 20 or the grinding mechanism 70. Furthermore, the height recognition unit such as the Z-axis encoder 55 may be configured to recognize the height of the chuck table 20 or the grinding mechanism 70 raised or lowered by the lifting mechanism. Furthermore, the light-projecting unit 81 may be configured to project measurement light having a width wider than the gap between the holding surface 22 and the grinding surface 771 when the chuck table 20 and the grinding mechanism 70 are in a predetermined positional relationship.

[0055] In addition, the calculation unit 9 of the control unit 7 may be configured to calculate the height of the chuck table 20 or the grinding mechanism 70 raised and lowered by the lifting mechanism when the grinding wheel 77 comes into contact with the holding surface 22 by subtracting the gap distance recognized by the distance recognition unit 8 from the height recognized by the height recognition unit when a gap is formed between the holding surface 22 and the grinding surface 771 of the grinding wheel 77. Furthermore, when using a sensor unit 80 that is detachable from the grinding apparatus 1 (see Figure 4), the sensor unit 80 only needs to be installed at a predetermined location on the grinding apparatus 1 that does not move relative to the chuck table 20 or the grinding wheel 77. The holding surface 22 of the chuck table 20 is formed in a conical shape, with the radius portion of the holding surface 22 being parallel to the lower surface of the grinding wheel 77, and the straight line connecting the light-projecting unit 81 and the light-receiving unit 83 being disposed so as to intersect with the radius portion of the holding surface 22 that is parallel to the lower surface (grinding surface 771) of the grinding wheel 77. In this embodiment, the straight line connecting the light-projecting unit 81 and the light-receiving unit 83 is disposed so as to pass through the center of the holding surface 22.

[0056] Furthermore, the control unit 7 can determine the amount of wear of the grinding wheel 77 by distinguishing between the amount of light blocked by the grinding wheel 77 and the amount of light blocked by the chuck table 20. That is, for example, the control unit 7 controls the lifting mechanism 50 to raise the grinding mechanism 70, thereby positioning the grinding wheel 77 at a position where it does not block the measurement light projected from the light projector 81. In this state, the control unit 7 projects measurement light from the light projector 81 at the measurement position, and the light receiver 83 receives the measurement light L in a state where it is partially blocked by the chuck table 20. The control unit 7 acquires a first amount of received light, which is the amount of light received by the light receiver 83 at this time.

[0057] Thereafter, the control unit 7 controls the lifting mechanism 50 to lower the grinding mechanism 70 to the standby position. In this state, the control unit 7 projects measurement light from the light-projecting unit 81 located at the measurement position, and the light-receiving unit 83 receives measurement light L that is partially blocked by the grinding wheel 77 and the chuck table 20. The control unit 7 acquires a second amount of received light, which is the amount of light received by the light-receiving unit 83 at this time. The control unit 7 then calculates the difference between the first amount of received light and the second amount of received light to determine the amount of measurement light blocked by the grinding wheel 77.

[0058] Furthermore, the control unit 7 detects the wear amount of the grinding wheel 77 based on the amount of light blocked by the grinding wheel 77. For example, the control unit 7 detects the wear amount of the grinding wheel 77 based on how much the amount of light blocked by the grinding wheel 77 has decreased from the amount of light blocked by an unused grinding wheel 77. Then, the control unit 7 notifies the operator of the wear amount of the grinding wheel 77 and the replacement time using, for example, a display member (not shown) such as a touch panel provided in the grinding device 1.

[0059] Alternatively, when measuring the second amount of received light, the control unit 7 may control the lifting mechanism 50 to adjust the height of the grinding mechanism 70 so that the amount of light blocked by the grinding wheel 77 (the difference between the first amount of received light and the second amount of received light) becomes a predetermined value (for example, so that the grinding surface 771 of the grinding wheel 77 blocks the portion up to 1.5 mm from the upper end of the measurement light). In this case, the control unit 7 can determine the amount of wear of the grinding wheel 77 based on the height of the grinding mechanism 70.

[0060] In addition, in a configuration in which the chuck table 20 is raised and lowered relative to the grinding mechanism 70, the control unit 7 raises and lowers the chuck table 20 while keeping the position of the grinding mechanism 70 fixed, and irradiates measurement light during this period to measure the amount of light blocked by the chuck table 20 in the same manner as described above, thereby determining the amount of wear and replacement time of the chuck table 20. [Explanation of symbols]

[0061] 1: grinding device, 7: control unit, 8: distance recognition unit, 9: calculation unit, 10: base, 11: column, 12: bellows cover, 13: opening, 20: chuck table, 21: porous member, 22: holding surface, 23: frame body, 24: Frame surface, 28: Table rotation mechanism, 30: Wafer holding mechanism, 39: Cover plate, 40: Y-axis direction movement mechanism, 41: support base, 42: Y-axis guide rail, 43: Y-axis ball screw, 44: Y-axis motor, 45: Y-axis moving table, 50: Elevating mechanism, 51: Z-axis guide rail, 52: Z-axis ball screw, 53: Z-axis moving table, 54: Z-axis motor, 55: Z-axis encoder, 56: holder, 70: grinding mechanism, 71: spindle housing, 72: spindle, 73: spindle motor, 74: wheel mount, 75: grinding wheel, 76: Wheel base, 77: Grinding wheel, 80: Sensor unit, 81: Light projecting unit, 82: Light-emitting unit lifting mechanism, 83: Light-receiving unit, 84: Light-receiving unit lifting mechanism, 85: Base, 100: wafer, 101: front surface, 102: back surface, 103: protective tape, 771: grinding surface, D: gap between grinding surface and holding surface, L: measurement light, T1: distance of D, T2: Width of measurement light

Claims

1. A grinding device comprising: a chuck table that holds a wafer by a holding surface; a grinding mechanism that grinds the wafer by a grinding surface at the tip of a ring-shaped grinding wheel; a lifting mechanism that raises and lowers the chuck table or the grinding mechanism; and a height recognition unit that recognizes the height of the chuck table or the grinding mechanism that is raised and lowered by the lifting mechanism, a sensor unit further including: a light-projecting unit that projects measurement light having a width wider than a gap between the holding surface and the grinding surface when the chuck table and the grinding mechanism are in a predetermined positional relationship; and a light-receiving unit that receives the measurement light that has passed through the gap in a state where a portion of the light is blocked by the grinding wheel and the chuck table; a distance recognition unit that recognizes the distance of the gap based on the amount of light received by the light receiving unit; a calculation unit that calculates the height of the chuck table or the grinding mechanism raised and lowered by the lifting mechanism when the grinding wheel contacts the holding surface by subtracting the distance of the gap recognized by the distance recognition unit from the height recognized by the height recognition unit when the gap is formed.

2. a light-projecting unit lifting mechanism that lifts and lowers the light-projecting unit; and a light receiving unit lifting mechanism that lifts and lowers the light receiving unit. The grinding device according to claim 1.

3. A sensor unit provided in the grinding machine according to claim 1, a base that is installed on the grinding device, and the light-emitting unit and the light-receiving unit that are provided on the base; Sensor unit.

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