Grinding device

Abstract

To reduce the number of man-hours by an operator, and reduce the possibility of occurrence of an operating mistake caused by manual setup, in setup of a grinding device.SOLUTION: A grinding device includes: a chuck table; a grinding unit; a moving mechanism for relatively moving the chuck table and the grinding unit in a predetermined direction; a detection part for emitting a belt-like laser beam and receiving the reflected light; and a control unit for controlling a grinding unit moving mechanism and the detection part, wherein the control unit has: a holding surface position storage part for storing a relative height position of a holding surface to a grinding wheel in the predetermined direction; a first distance calculation part for calculating a first distance in the predetermined direction between the detection part and a lower surface of a grinding stone; and a lower surface position calculation part for calculating a position of the lower surface of the grinding stone based on the holding surface, on the basis of the height position stored in the holding surface position storage part and the first distance calculated by the first distance calculation part.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a grinding device for grinding a workpiece.

Background Art

[0002] Various electronic devices such as mobile phones and personal computers are equipped with semiconductor device chips. The semiconductor device chip is manufactured by processing a semiconductor wafer (hereinafter simply referred to as a wafer) in which a plurality of planned division lines are set in a grid pattern on the surface and devices such as ICs (Integrated Circuits) are formed in each region defined by the plurality of planned division lines.

[0003] In recent years, in order to reduce the size and weight of semiconductor device chips, before cutting and dividing the wafer along each planned division line using a cutting device, a process of grinding the back surface side of the wafer using a grinding device to thin the wafer to a predetermined thickness may be adopted.

[0004] The grinding device includes a chuck table for sucking and holding a wafer. Above the chuck table, a grinding unit including a cylindrical spindle arranged along the height direction (Z-axis direction) is provided. An annular grinding wheel is attached to the lower end of the spindle.

[0005] For example, in plunge grinding, the chuck table holding the wafer is rotated, and the grinding wheel rotating about the spindle as the rotation axis is moved downward (fed for grinding) at a predetermined speed along the Z-axis direction.

[0006] In order to accurately control the grinding amount and finish thickness of the wafer, a so-called setup is required to make the grinding device recognize the position of the lower surface of the grinding wheel with the holding surface of the chuck table as a reference in the height direction (i.e., the origin position).

[0007] For example, setup is performed when replacing a used grinding wheel with a new one or when the grinding wheel wears out during use. Also, setup is performed as necessary when replacing a used chuck table with a new one or after performing so-called self-grinding in which the holding surface of the chuck table is ground with a grinding wheel.

[0008] In the setup of the grinding device, after an operator places a reference piece (block gauge) of a predetermined thickness on the holding surface, a manual setup in which the lower surface of the grinding wheel is brought into contact with the predetermined upper surface of the reference piece by feeding the grinding unit in the grinding feed direction is common (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0009]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0010] However, in manual setup, it takes a lot of man-hours for the operator, and if manual setup is performed every time setup is done, there is a possibility that the grinding device or the grinding wheel may be damaged by a work error using the reference piece.

[0011] The present invention has been made in view of such problems, and an object thereof is to reduce the man-hours of work by an operator and reduce the possibility of work errors caused by manual setup in the setup of a grinding device.

Means for Solving the Problems

[0012] According to one aspect of the present invention, there is provided a grinding apparatus for grinding a workpiece, comprising: a chuck table having a holding surface for holding the workpiece and rotatable about a predetermined rotation axis; a grinding unit disposed above the chuck table, having a spindle, and having a plurality of grinding wheels disposed along the circumferential direction of an annular wheel base on the lower surface side of the wheel base and attached to the lower end of the spindle; a moving mechanism for relatively moving the chuck table and the grinding unit along a predetermined direction so that the holding surface and the grinding wheel approach each other; at least one grinding wheel; a light emitting unit including a light emitting element and a lens for irradiating a strip-shaped laser beam across at least one grinding wheel and the lower surface of the wheel base adjacent to the at least one grinding wheel in the radial direction of the grinding wheel; a light receiving unit including a light receiving element for receiving the reflected light of the laser beam; a detection unit; a control unit having a processor and a memory for controlling the grinding unit, the moving mechanism, and the detection unit, the control unit including: a holding surface position storage unit for storing the relative height position of the holding surface with respect to the grinding wheel in the predetermined direction; a first distance calculation unit for calculating a first distance in the predetermined direction from the detection unit to the lower surface of the at least one grinding wheel; and a lower surface position calculation unit for calculating the position of the lower surface of the at least one grinding wheel with reference to the holding surface based on the height position stored in the holding surface position storage unit and the first distance calculated by the first distance calculation unit. When the grinding wheel contacts the upper surface of the reference piece disposed on the holding surface, the relative height position of the holding surface in the predetermined direction with respect to the grinding wheel is P A Let the thickness from the upper surface to the lower surface of the reference piece be D, and the first distance from the detection unit to the lower surface of the at least one grinding wheel be B 1 Also, in a state where the reference piece is removed from the holding surface, the first distance from the detection unit to the lower surface of the at least one grinding wheel is Z 1 In the case where it is set as such, the lower surface position calculation unit calculates the height position P of the lower surface of the at least one grinding wheel with respect to the holding surface in a state where the reference piece is removed from the holding surface C using (Equation 1) Z 3 =Z 1 -(B 1 - D) and (Equation 2) P C =P A +Z 3 for calculation The grinding apparatus is provided.

[0014] Preferably, the control unit further includes a cutting edge length calculation unit for calculating the cutting edge length of the at least one grinding wheel based on a second distance from the detection unit to the lower surface of the wheel base and the first distance from the detection unit to the lower surface of the at least one grinding wheel.

[0015] Also preferably, the control unit further includes a center deviation calculation unit that calculates the deviation between the rotation center of the spindle and the center of the outer peripheral side surface of the plurality of grinding wheels based on the received light data detected by the detection unit when the grinding wheel is rotated.

Effect of the Invention

[0016] The control unit of the grinding device according to one aspect of the present invention can calculate the position of the lower surface of at least one grinding wheel with reference to the holding surface by using a detection unit using a laser beam. Therefore, the man-hours required for the operator to place the reference piece on the holding surface and then collect it can be reduced, and furthermore, the possibility of work errors caused by manual setup can be reduced.

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Embodiment for Carrying Out the Invention

[0018] Referring to the accompanying drawings, an embodiment according to one aspect of the present invention will be described. FIG. 1 is a perspective view of the grinding apparatus 2. The X-axis direction (front-rear direction), Y-axis direction, and Z-axis direction (up-down direction) shown in FIG. 1 and the subsequent figures are orthogonal to each other.

[0019] The grinding apparatus 2 is of a manual type in which the loading and unloading of the wafer (workpiece) 11 and the like are performed by an operator. However, the grinding apparatus 2 may be a full-auto type that automatically performs grinding and cleaning in addition to the loading and unloading of the wafer 11.

[0020] The grinding apparatus 2 has a base 4 that supports the components of the grinding apparatus 2. On the upper surface of the base 4, a rectangular opening 4a having a long hand portion arranged along the X-axis direction is formed. Below the opening 4a, a ball screw type X-axis direction movement mechanism 6 is provided.

[0021] In FIG. 1, the schematic position of the X-axis direction movement mechanism 6 is shown. The X-axis direction movement mechanism 6 has a pair of guide rails (not shown) arranged substantially parallel to the X-axis direction. On the pair of guide rails, an X-axis direction movement plate (not shown) is slidably attached.

[0022] On the lower surface side of the X-axis direction movement plate, a nut portion (not shown) is provided, and a ball screw (not shown) arranged substantially parallel to the X-axis direction between the pair of guide rails is rotatably connected to the nut portion.

[0023] One end of the ball screw is connected to a drive source (not shown) such as a stepping motor. When the drive source is operated, the X-axis direction movement plate moves along the X-axis direction. On the upper part of the X-axis direction movement plate, a rotation drive source (not shown) such as a motor for rotating the chuck table 8 is provided.

[0024] Also, a rotating body (not shown) is arranged above the X-axis direction moving plate, and the lower surface side of the disk-shaped chuck table 8 is connected to the upper end of the rotating body. A driven pulley (not shown) is provided at the lower end of this rotating body.

[0025] An endless belt (not shown) is wound around the driven pulley of the rotating body and the drive pulley (not shown) of the rotation drive source. When the rotation drive source is operated, the chuck table 8 rotates around a predetermined rotation axis 10 (see FIG. 2).

[0026] The chuck table 8 is rotatably supported on a table base (not shown) via a bearing (not shown), and the table base is supported on the upper surface of the X-axis direction moving plate by an inclination adjustment mechanism (not shown).

[0027] The inclination adjustment mechanism has one fixed shaft (not shown) and two movable shafts (not shown) that can change their lengths along the Z-axis direction, and can adjust the inclinations of the table base and the chuck table 8.

[0028] Here, referring to FIG. 7, the structure of the chuck table 8 will be described. The chuck table 8 has a disk-shaped frame body 12 formed of ceramics or the like. A disk-shaped recess is formed on the upper surface side of the frame body 12.

[0029] A plurality of flow paths 12a are formed radially on the bottom surface of the recess of the frame body 12. Further, a central flow path 12b is formed in the frame body 12 so as to penetrate the center of the bottom surface of the frame body 12. One end of the central flow path 12b is connected to the plurality of flow paths 12a, and the other end of the central flow path 12b is connected to a suction source (not shown) such as an ejector or a vacuum pump.

[0030] A disk-shaped porous plate 14 formed of porous ceramics is fixed in the recess of the frame body 12. The porous plate 14 has a substantially flat bottom surface and a conical upper surface with the central portion slightly protruding compared to the outer peripheral portion. A negative pressure is transmitted from the suction source to the upper surface of the porous plate 14.

[0031] The upper surface of the porous plate 14 and the upper surface of the frame body 12 are substantially flush with each other, forming a holding surface 8a for sucking and holding the wafer 11. By adjusting the inclination of the rotation axis 10 of the chuck table 8 with the above-described inclination adjustment mechanism, a part of the holding surface 8a is arranged substantially parallel to the X-Y plane.

[0032] Here, returning to FIG. 1. The chuck table 8 is located on a rectangular table cover 16, and bellows-shaped cover members 18 that can expand and contract in the X-axis direction are provided on both sides of the table cover 16 in the X-axis direction.

[0033] The chuck table 8 is moved by the X-axis direction movement mechanism 6 between a loading / unloading area A1 located in front of the opening 4a (one side in the X-axis direction) and a grinding area A2 located behind the opening 4a (the other side in the X-axis direction). A disk-shaped wafer 11 is placed on the chuck table 8 arranged in the loading / unloading area A1.

[0034] The wafer 11 is, for example, a disk-shaped substrate made of silicon on which a plurality of devices (not shown) are formed on the surface 11a side. However, the wafer 11 may be formed of a compound semiconductor such as silicon carbide (SiC) or gallium nitride (GaN), or may be formed of other materials.

[0035] A resin-made protective tape 13 for device protection is attached to the surface 11a side of the wafer 11. When the surface 11a side is sucked and held by the holding surface 8a via the protective tape 13, the back surface 11b side of the wafer 11 is exposed upward (see FIG. 4).

[0036] A rectangular parallelepiped-shaped column portion 20 is provided on the rear side of the opening 4a. A grinding feed mechanism (moving mechanism) 22 is provided on the front side of the column portion 20. The grinding feed mechanism 22 has a pair of rails 24 fixed to the front surface of the column portion 20.

[0037] A Z-axis direction moving plate 26 is slidably attached to each rail 24 via a slider (not shown). A nut portion (not shown) is provided on the rear side of the Z-axis direction moving plate 26. A ball screw 28 provided along the Z-axis direction between the pair of rails 24 is rotatably connected to the nut portion.

[0038] A drive source 30 such as a stepping motor is connected to the upper end portion of the ball screw 28. When the ball screw 28 is rotated by the drive source 30, the Z-axis direction moving plate 26 moves in the Z-axis direction along the rail 24.

[0039] A grinding unit 32 is fixed to the front surface of the Z-axis direction moving plate 26 in a manner movable in the Z-axis direction (predetermined direction) by a grinding feed mechanism 22. The grinding unit 32 is fixed to the Z-axis direction moving plate 26 via a cylindrical holding member 34 fixed to the front surface of the Z-axis direction moving plate 26.

[0040] Inside the holding member 34, a cylindrical spindle housing 36 arranged substantially parallel to the Z-axis direction is arranged. A part of a cylindrical spindle 38 (see FIG. 7) arranged along the Z-axis direction is rotatably accommodated in the spindle housing 36.

[0041] A rotary drive source 40 such as a motor is provided at the upper end portion of the spindle 38. The lower end of the spindle 38 protrudes below the lower end of the spindle housing 36 (see FIG. 7). A disk-shaped wheel mount 42 is fixed to the lower end portion of the spindle 38.

[0042] An annular grinding wheel 44 is mounted on the lower surface side of the wheel mount 42 by a fixing member (not shown) such as a screw. The grinding wheel 44 includes an annular wheel base 46 formed of a metal material such as an aluminum alloy, and the lower surface 46a side of the wheel base 46 is fixed with a plurality of grinding wheels 48.

[0043] A plurality of grinding wheels 48 are arranged in a ring along the circumferential direction of the lower surface 46a of the wheel base 46 with a gap provided between adjacent grinding wheels 48. The grinding wheel 48 is formed, for example, by mixing abrasive grains such as diamond and cBN (cubic boron nitride) into a binder such as metal, ceramics, or resin, followed by molding, firing, etc.

[0044] Below the grinding unit 32, a grinding water supply nozzle (not shown) for supplying grinding water such as pure water is provided to the contact area 11c (see FIG. 5) between the wafer 11 and the grinding wheel 48 during grinding.

[0045] As shown in FIG. 2, a laser displacement meter (detection unit) 50 is provided behind the table cover 16. FIG. 2 is an enlarged perspective view of the chuck table 8 and the laser displacement meter 50, and FIG. 3 is a partial cross-sectional side view showing the outline of the laser displacement meter 50.

[0046] As shown in FIG. 3, the laser displacement meter 50 has a light emitting unit 54 housed in a rectangular parallelepiped housing 52. The light emitting unit 54 has a light emitting element 54a such as a semiconductor laser (laser diode).

[0047] A laser beam having a predetermined wavelength is emitted from the light emitting element 54a. The laser beam emitted from the light emitting element 54a is incident on a laser line generator (hereinafter simply referred to as lens 54b) such as a Powell lens, a Lineman lens, or a cylindrical lens.

[0048] The laser beam is shaped by the lens 54b into a belt-shaped laser beam L having a predetermined length along a direction (in this example, the X-axis direction) perpendicular to the traveling direction of the laser beam (in this example, the Z-axis direction) and having a substantially uniform output in the X-axis direction.

[0049] The strip-shaped laser beam L is irradiated from a rectangular opening 52a formed at the top of the housing 52 and having a long portion along the X-axis direction toward an object (in this example, the grinding wheel 48 and the wheel base 46). The reflected light of the laser beam L diffusely reflected from the object is received by the light receiving unit 56.

[0050] The light receiving unit 56 is provided in the housing 58 adjacent to the housing 52 in the Y-axis direction. The light receiving unit 56 has a condenser lens 62 for condensing the reflected light incident through a circular opening 58a formed in the upper part of the housing 58 onto a CMOS (Complementary Metal-Oxide-Semiconductor) sensor (light receiving element) 60.

[0051] Note that the condenser lens 62 may be a single lens or may be composed of a plurality of lenses like an Ernostar-type lens. The CMOS sensor 60 has a plurality of photoelectric conversion elements (not shown) arranged two-dimensionally.

[0052] Each photoelectric conversion element is a photosensor such as a phototransistor, for example. Each photoelectric conversion element photoelectrically converts the reflected light from the object at a predetermined sampling period and outputs a voltage signal corresponding to the received light amount.

[0053] The voltage signal (that is, an analog signal) is converted into a digital signal by a predetermined processing circuit (not shown) having an analog-to-digital converter (ADC) or the like, and then processed by a control unit 70 described later.

[0054] The laser displacement meter 50 irradiates the grinding wheel 44 with the laser beam L from below the grinding wheel 44, for example, so that the longitudinal direction of the strip-shaped laser beam L is along the radial direction of the wheel base 46 (see FIG. 4).

[0055] In this case, the laser beam L is irradiated across at least one grinding wheel 48 and the lower surface 46a of the wheel base 46 that is adjacent to at least one grinding wheel 48 in the radial direction of the grinding wheel 44 (i.e., the wheel base 46).

[0056] The laser beam L is diffusely reflected from the lower surface 46a of the wheel base 46 (see FIG. 7) and the lower surface 48a of the grinding wheel 48, and is received by the CMOS sensor 60.

[0057] Since the light-receiving position of the CMOS sensor 60 changes according to the distance from the light-emitting unit 54 to the reflection position, the distance to the reflection position of the object is measured according to the light-receiving position of the CMOS sensor 60 (triangulation method).

[0058] For example, with the grinding wheel 44 arranged at a height position approximately 60 mm to 90 mm away from the laser displacement meter 50 in the Z-axis direction, the first distance B1 (see FIG. 7) and the first distance Z1 (see FIG. 9) from the laser displacement meter 50 to the lower surface 48a of the grinding wheel 48 are measured.

[0059] Similarly, using the laser displacement meter 50, the second distance B2 (see FIG. 7) and the second distance Z2 (see FIG. 9) from the laser displacement meter 50 to the lower surface 46a of the wheel base 46 are measured.

[0060] Note that the protrusion amount of the grinding wheel 48 from the wheel base 46 (i.e., the cutting edge length, also called the segment height) is calculated based on the difference between the first distance B1 and the second distance B2, and the difference between the first distance Z1 and the second distance Z2.

[0061] FIG. 4 is an enlarged perspective view of the chuck table 8, the grinding wheel 44, and the laser displacement meter 50 when the laser beam L is irradiated, and FIG. 5 is a top view of the chuck table 8, the grinding wheel 44, and the laser displacement meter 50. In FIG. 5, the grinding wheel 44 is shown by a dashed line.

[0062] As shown in Fig. 1, the grinding device 2 has a control unit 70 that controls operations of the above-described X-axis direction movement mechanism 6, rotation drive source, inclination adjustment mechanism, suction source, chuck table 8, grinding feed mechanism 22, grinding unit 32, laser displacement meter 50, and the like.

[0063] The control unit 70 is constituted by a computer including, for example, a processor (processing device) represented by a CPU (Central Processing Unit) and a memory (storage device).

[0064] The storage device includes a main storage device such as a DRAM (Dynamic Random Access Memory), SRAM (Static Random Access Memory), ROM (Read Only Memory), and an auxiliary storage device such as a flash memory, hard disk drive, solid state drive.

[0065] The auxiliary storage device stores software including a predetermined program. By operating the processing device and the like according to this software, the functions of the control unit 70 are realized.

[0066] A part of the auxiliary storage device functions as a holding surface position storage unit 72 that stores the relative height position P in the Z-axis direction of the holding surface 8a with respect to the grinding wheel 44. The holding surface position storage unit 72 of the present embodiment stores the height position P of the holding surface 8a with respect to the grinding wheel 44 when the lower surface 48a of the grinding wheel 48 contacts the reference piece 64 (see Fig. 7). A A stores.

[0067] Note that the control unit 70 can grasp the movement amount of the grinding wheel 44 in the Z-axis direction by controlling the drive source 30. Therefore, once the height position P is stored in the holding surface position storage unit 72, thereafter, as long as there is no replacement of the chuck table 8, modification of the shape of the holding surface 8a, etc., the control unit 70 can always grasp the relative height position of the grinding wheel 44 (for example, the lower surface 46a of the wheel base 46). A

[0068] The auxiliary storage device stores a first program. When executed by the processor, the first program functions as a first distance calculation unit 74 that calculates the distance in the Z-axis direction from the laser displacement meter 50 to the lower surface 48a of the grinding wheel 48 (the first distance B1 (see FIG. 7), the first distance Z1 (see FIG. 9)) according to the light-receiving position on the CMOS sensor 60.

[0069] Also, the auxiliary storage device stores a second program. When executed by the processor, the second program, based on the height position P stored in the holding surface position storage unit 72, the first distance B1, etc., functions as a lower surface position calculation unit 76 that calculates the height position P (see FIG. 9) of the lower surface 48a of the grinding wheel 48 with respect to the holding surface 8a. The method of calculating the height position P will be described later. A Based on, etc., the height position P of the lower surface 48a of the grinding wheel 48 with respect to the holding surface 8a C (see FIG. 9) is calculated. Note that the height position P C The calculation method will be described later.

[0070] Furthermore, the auxiliary storage device stores a third program. When executed by the processor, the third program functions as a cutting edge length calculation unit 78. The cutting edge length calculation unit 78 can calculate the cutting edge length C (see FIG. 7) of the grinding wheel 48 based on, for example, the second distance B2 (see FIG. 7) from the laser displacement meter 50 to the lower surface 46a of the wheel base 46 and the first distance B1.

[0071] Also, for example, the cutting edge length calculation unit 78 can calculate the cutting edge length C of the grinding wheel 48 based on, for example, the second distance Z2 (see FIG. 9) from the laser displacement meter 50 to the lower surface 46a of the wheel base 46 and the first distance Z1 (see FIG. 9).

[0072] Specifically, the cutting edge length calculation unit 78 calculates the cutting edge length C located directly above the laser displacement meter 50 by subtracting the first distance Z1 (or B1) from the second distance Z2 (or B2).

[0073] Furthermore, the auxiliary storage device stores a fourth program. When executed by the processor, the fourth program functions as a center deviation calculation unit 80 that calculates the deviation (see FIG. 10) between the rotation center 38a of the spindle 38 and the center 48c of the outer peripheral side surface 48b of the plurality of grinding wheels 48 based on the light reception data detected by the laser displacement meter 50 when the grinding wheel 44 is rotated. The method of calculating the deviation will be described later.

[0074] Incidentally, when grinding the wafer 11 with the grinding apparatus 2, first, the chuck table 8 is disposed in the loading / unloading area A1. Then, after sucking and holding the surface 11a side of the wafer 11 by the holding surface 8a, the chuck table 8 is moved to the grinding area A2. Then, the chuck table 8 is rotated in a predetermined direction around the rotation axis 10.

[0075] Also, grinding water is supplied from the grinding water supply nozzle to the contact area 11c, and while rotating the grinding wheel 44 in a predetermined direction with the spindle 38 as the rotation axis, the grinding unit 32 is moved downward at a predetermined speed along the Z-axis direction by the grinding feed mechanism 22.

[0076] In this way, as the holding surface 8a and the grinding wheel 44 approach each other, the chuck table 8 and the grinding unit 32 move relatively along the Z-axis direction, and when the lower surface 48a of the grinding wheel 48 contacts the back surface 11b of the wafer 11, the back surface 11b side is ground.

[0077] However, prior to grinding the wafer 11, a process for causing the grinding apparatus 2 to recognize the position of the lower surface 48a of the grinding wheel 48 with the holding surface 8a as a reference in the height direction (i.e., the origin position), so-called setup, is performed.

[0078] Next, the setup of the grinding apparatus 2 will be described. Usually, in the setup of the grinding apparatus 2, manual setup is performed. In the manual setup, first, an operator places a reference piece (block gauge) 64 having a predetermined thickness in a predetermined area of the holding surface 8a.

[0079] Next, the grinding unit 32 is fed in the grinding direction so that the lower surface 48a of the grinding wheel 48 contacts a predetermined upper surface 64a of the reference piece 64. Thereby, the position of the lower surface 48a of the grinding wheel 48 with the holding surface 8a as a reference in the height direction is recognized by the grinding apparatus 2.

[0080] However, in the manual setup, it takes a long time for the operator to perform the work, and if the manual setup is performed every time of setup, there is a risk that the grinding apparatus 2 and the grinding wheel 44 will be damaged due to a work error.

[0081] Therefore, in the present embodiment, as shown in FIG. 6, in the first setup, the manual setup is performed using the reference piece 64 (from S10 to S30), but in the second and subsequent setups, the setup is performed using the laser displacement meter 50 without using the reference piece 64 (S50).

[0082] Thereby, the man-hour for the operator to place the reference piece 64 on the holding surface 8a and then collect it can be reduced. Further, the possibility of a work error caused by the manual setup can be reduced. That is, the possibility that the grinding apparatus 2 or the grinding wheel 44 is damaged by the reference piece 64 due to a work error can be reduced.

[0083] FIG. 6 is a flowchart for performing the setup of the present embodiment. In the reference piece placement step S10, the operator manually places the reference piece 64 in a predetermined area of the holding surface 8a corresponding to the contact area 11c. As shown in FIG. 7, the reference piece 64 has a substantially flat lower surface 64b and a substantially stepped upper surface 64a.

[0084] The distance from the lower surface 64b to the upper surface 64a changes stepwise. For example, the thickness 64c1 of the thickest area is 5.05 mm, the thickness 64c2 of the second thickest area is 5.02 mm, and the thickness 64c3 of the thinnest area is 5.00 mm.

[0085] In this example, the thickest area is used, but which thickness area to use may be determined as appropriate. The reference used Piece 64The thickness D is input to the control unit 70 by an operator via an input device (not shown) such as a touch panel.

[0086] After the reference piece placement step S10, the grinding unit 32 disposed above the chuck table 8 is lowered. Then, the relative height position P in the Z-axis direction of the holding surface 8a B The lower surface 48a of the grinding wheel 48, which is at a position different from directly above, is brought into contact with the upper surface 64a of the reference piece 64 located at (contact step S20).

[0087] Also, in the contact step S20, the relative height position P in the Z-axis direction of the holding surface 8a with respect to the grinding wheel 44 when the lower surface 48a contacts the reference piece 64 A is memorized by the holding surface position storage unit 72.

[0088] After the contact step S20, or simultaneously with the contact step S20, the first distance B1 from the laser displacement meter 50 to the lower surface 48a of the grinding wheel 48 is measured (first measurement step S30). FIG. 7 is a partial cross-sectional side view showing the first measurement step S30.

[0089] After the first measurement step S30, the reference piece 64 is removed from the holding surface 8a (removal step S40). Note that between the reference piece placement step S10 and the removal step S40, the spindle 38 of the grinding unit 32 and the chuck table 8 are not rotated.

[0090] After the removal step S40, for example, the wafer 11 is ground. As the lower surface 48a side of the grinding wheel 48 wears due to the grinding of the wafer 11, the edge length C of the grinding wheel 48 becomes shorter (see FIG. 9).

[0091] When the edge length C becomes shorter, even if the grinding wheel 44 is arranged at the height position arranged in the contact step S20, the distance from the lower surface 48a to the holding surface 8a is different from the thickness D. In such a case, it is necessary to perform the setup again in order to perform the grinding with high precision.

[0092] Incidentally, even if the lower surface 48a side of the grinding wheel 48 wears, the first distance Z1 from the laser displacement meter 50 to the lower surface 48a (see FIG. 9) and the distance Z3 from the holding surface 8a to the lower surface 48a (see FIG. 9) increase in the same manner. That is, the distance Z3 is a linear function with a coefficient (i.e., slope) of 1 of the first distance Z1.

[0093] As described above, when the first distance Z1 is the first distance B1, the distance Z3 is the thickness D (see FIG. 7). Also, in this embodiment, D < B1 (that is, the laser displacement meter 50 is located below the holding surface 8a). In this case, the first distance Z1 and the distance Z3 are represented by the following mathematical formula 1.

[0094]

Equation

[0095] FIG. 8 is a graph showing the distances from the holding surface 8a and the laser displacement meter 50 to the lower surface 48a of the grinding wheel 48. Once the distance Z3 is calculated, the height position P of the lower surface 48a of the grinding wheel 48 with respect to the holding surface 8a C is calculated by the following mathematical formula 2.

[0096]

Equation

[0097] The lower surface position calculation unit 76 has a program corresponding to the above mathematical formulas 1 and 2, and can calculate the height position P of the lower surface 48a with respect to the holding surface 8a from the first distance B1, the thickness D, the relative height position P A , and the first distance Z1. C

[0098] After grinding the wafer 11, when calculating the height position P of the lower surface 48a with respect to the holding surface 8a C , the laser beam L is irradiated onto the grinding wheel 44 arranged at an arbitrary height position to measure the first distance Z1 from the laser displacement meter 50 to the lower surface 48a of the grinding wheel 48 (second measurement step S50).

[0099] FIG. 9 is a partial cross-sectional side view showing the second measurement step S50. If the first distance Z1 is obtained in the second measurement step S50, as described above, the lower surface position calculation unit 76 determines the height position P of the lower surface 48a of the grinding wheel 48 at the time of the second measurement step S50 with respect to the holding surface 8a. C can be calculated (lower surface height position calculation step S60).

[0100] In the second measurement step S50, the setup can be performed using the laser displacement meter 50 without using the reference piece 64. Thereby, the man-hour for the operator to place the reference piece 64 on the holding surface 8a and then collect it can be reduced.

[0101] Furthermore, the possibility of work errors caused by manual setup can be reduced. That is, the possibility of damage to the grinding device 2 or the grinding wheel 44 by the reference piece 64 due to work errors can be reduced.

[0102] Also, in the second measurement step S50, since the reference piece 64 is not used, there is an advantage that the setup can be performed even during the grinding of the wafer 11 or during the rotation of the grinding wheel 44. That is, the setup is possible even with the chuck table 8 and the grinding wheel 44 rotating.

[0103] During the rotation of the grinding wheel 44, the belt-shaped laser beam L is irradiated across the lower surfaces 48a of the plurality of grinding wheels 48 and the lower surfaces 46a of the wheel bases 46 adjacent to the respective grinding wheels 48 in the radial direction of the grinding wheel 44.

[0104] After the lower surface height position calculation step S60, when the setup is performed again using the laser displacement meter 50 without using the reference piece 64 (YES in S70), the process returns to S50. On the other hand, if the setup is not performed (NO in S70), the flow ends.

[0105] Incidentally, during the second measurement step S50, the center deviation calculation unit 80 of the control unit 70 calculates the deviation between the rotation center 38a of the spindle 38 and the center 48c of the outer peripheral side surface 48b of the plurality of grinding wheels 48 (see FIG. 10).

[0106] FIG. 10 shows the center of the outer peripheral side surface 48b of the plurality of grinding wheels 48 with respect to the rotation center 38a of the spindle 38 48c of the deviation. The deviation (i.e., eccentricity) between the rotation center 38a and the center 48c occurs when the grinding wheel 44 is mounted on the wheel mount 42 and is, for example, about 100 μm.

[0107] FIG. 10 shows the outer peripheral side surface 48b when the grinding wheel 44 is located at the most rearward position E1 in a top view of the grinding apparatus 2 with a solid line, and the outer peripheral side surface 48b when the grinding wheel 44 is located at the most forward position E2 with a dashed line.

[0108] When the rotation center 38a and the center 48c are thus displaced, the position of the outer peripheral edge of the lower surface 48a of the grinding wheel 48 located directly above the laser displacement meter 50 changes as the grinding wheel 44 rotates.

[0109] FIG. 11 is a graph showing the time change of the position of the outer peripheral edge of the lower surface 48a of the grinding wheel 48. In FIG. 11, the horizontal axis represents time, and the vertical axis represents the position of the outer peripheral edge of the lower surface 48a of the grinding wheel 48 located directly above the laser displacement meter 50.

[0110] In FIG. 11, the grinding wheel 44 is located at the forward position E2 at times 0 and T, and is located at the rearward position E1 at time T / 2. The center deviation calculation unit 80 calculates the distance F between the position of the outer peripheral edge at the forward position E2 and the position of the outer peripheral edge at the rearward position E1 according to the light receiving position on the CMOS sensor 60.

[0111] Since the deviation between the rotation center 38a and the center 48c corresponds to half of the distance F, the center deviation calculation unit 80 calculates F / 2 to calculate the deviation (deviation calculation step). The calculated deviation is displayed on a display device (not shown) such as a touch panel provided in the grinding device 2.

[0112] When the deviation between the rotation center 38a and the center 48c is not zero, the operator may correct the position of the center 48c of the outer peripheral side surface 48b. For example, with the operation of the grinding unit 32 stopped, the position of the center 48c can be corrected by hitting the side surface of the grinding wheel 44 with a hammer.

[0113] Also, with the grinding wheel 44 rotating at a predetermined rotational speed, the position of the center 48c of the outer peripheral side surface 48b can be corrected by pressing a dressing member against the outer peripheral side surface 48b. In addition, the structures, methods, etc. according to the above-described embodiments can be appropriately modified and implemented without departing from the scope of the object of the present invention.

Explanation of Reference Numerals

[0114] 2: Grinding device, 4: Base, 4a: Opening, 6: X-axis direction movement mechanism 8: Chuck table, 8a: Holding surface, 10: Rotation axis 11: Wafer (workpiece), 11a: Surface, 11b: Back surface, 11c: Contact area 13: Protective tape 12: Frame body, 12a: Flow path, 12b: Central flow path, 14: Porous plate 16: Table cover, 18: Cover member 20: Column portion, 22: Grinding feed mechanism (movement mechanism) 24: Rail, 26: Z-axis direction movement plate, 28: Ball screw, 30: Drive source 32: Grinding unit, 34: Holding member, 36: Spindle housing 38: Spindle, 38a: Rotation center, 40: Rotation drive source, 42: Wheel mount 44: Grinding wheel, 46: Wheel base, 46a: Lower surface 48: Grinding stone, 48a: Lower surface, 48b: Outer peripheral side surface, 48c: Center 50: Laser displacement meter (detection unit) 52: Housing, 52a: Opening, 54: Light emitting unit, 54a: Light emitting element, 54b: Lens 56: Light receiving unit, 58: Housing, 58a: Opening, 60: CMOS sensor, 62: Condensing lens 64: Reference piece, 64a: Upper surface, 64b: Lower surface, 64c1, 64c2, 64c3: Thickness 70: Control unit, 72: Holding surface position memory unit, 74: First distance calculation unit 76: Lower surface position calculation unit, 78: Cutting edge length calculation unit, 80: Centering deviation calculation unit A 1 : Loading and unloading area, A 2 : Grinding area B1: First distance, B2: Second distance, C: Cutting edge length, D: Thickness E1: Rear position, E2: Front position, F: Distance L: Laser beam, P A , P B , P C : Height position Z1: First distance, Z2: Second distance, Z3: Distance

Claims

1. A grinding apparatus for grinding a workpiece, comprising: a chuck table having a holding surface for holding the workpiece and rotatable about a predetermined rotation axis; a grinding unit disposed above the chuck table, having a spindle, and a grinding wheel having a plurality of grinding wheels disposed along the circumferential direction of an annular wheel base on the lower surface side of the wheel base, the grinding wheel being mounted at the lower end of the spindle; a moving mechanism for relatively moving the chuck table and the grinding unit along a predetermined direction so that the holding surface and the grinding wheel approach each other; a light emitting unit including a light emitting element and a lens for irradiating a strip-shaped laser beam across at least one grinding wheel and the lower surface of the wheel base adjacent to the at least one grinding wheel in the radial direction of the grinding wheel, and a light receiving unit including a light receiving element for receiving the reflected light of the laser beam; a control unit having a processor and a memory for controlling the grinding unit, the moving mechanism, and the detecting unit; The control unit: a holding surface position storage unit for storing the relative height position of the holding surface with respect to the grinding wheel in the predetermined direction; a first distance calculation unit for calculating a first distance in the predetermined direction from the detecting unit to the lower surface of the at least one grinding wheel; a lower surface position calculation unit for calculating the position of the lower surface of the at least one grinding wheel with respect to the holding surface based on the height position stored in the holding surface position storage unit and the first distance calculated by the first distance calculation unit; and When the grinding wheel contacts the upper surface of a reference piece disposed on the holding surface, the relative height position of the holding surface with respect to the grinding wheel in the predetermined direction is designated as PA, the thickness from the upper surface to the lower surface of the reference piece is designated as D, the first distance from the detecting unit to the lower surface of the at least one grinding wheel is designated as B1, and In a state where the reference piece is removed from the holding surface, when the first distance from the detecting unit to the lower surface of the at least one grinding wheel is designated as Z1, The lower surface position calculation unit: The height position PC of the lower surface of the at least one grinding wheel with respect to the holding surface in a state where the reference piece is removed from the holding surface, 【Number 1】 and 【Number 2】 A grinding apparatus, characterized in that it is calculated using.

2. The control unit: The grinding apparatus according to claim 1, further comprising a cutting edge length calculation unit that calculates the cutting edge length of the at least one grinding wheel based on a second distance from the detection unit to the lower surface of the wheel base and a first distance from the detection unit to the lower surface of the at least one grinding wheel.

3. The control unit The grinding apparatus according to claim 1 or 2, further comprising a center deviation calculation unit that calculates a deviation between the rotation center of the spindle and the center of the outer peripheral side surface of the plurality of grinding wheels based on the received light data detected by the detection unit when the grinding wheel is rotated.

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