Grinding equipment

Abstract

[Topic] In the setup of grinding equipment, reduce the working hours performed by operators and reduce the possibility of operational errors caused by manual settings. [Solution] A grinding apparatus is provided, comprising: a work chuck; a grinding unit; a moving mechanism for moving the work chuck and the grinding unit relative to each other in a predetermined direction; a detection unit for irradiating a strip-shaped laser beam and receiving its reflected light; and a control unit for controlling the grinding unit moving mechanism and the detection unit. The control unit includes: a holding surface position memory unit for storing the relative height position of the holding surface relative to the grinding wheel in a predetermined direction; a first distance calculation unit for calculating a first distance in a predetermined direction from the detection unit to the lower surface of the grinding stone; and a lower surface position calculation unit for calculating the position of the lower surface of the grinding stone with the holding surface as a reference, based on the height position stored in the holding surface position memory unit and the first distance calculated by the first distance calculation unit.

Description

[Technical Field]

[0001] This invention relates to a grinding apparatus for grinding a workpiece. [Previous Technology]

[0002] Semiconductor device chips are mounted in various electronic devices such as mobile phones and personal computers. Semiconductor device chips are manufactured by processing semiconductor wafers (hereinafter referred to as wafers). The aforementioned semiconductor wafers have a plurality of predetermined dividing lines set in a grid pattern on the front side, and devices such as ICs (integrated circuits) are formed in each area defined by the plurality of predetermined dividing lines.

[0003] In recent years, in order to achieve miniaturization and weight reduction of semiconductor device wafers, the following procedure is sometimes adopted: before using a cutting device to cut and divide the wafer along each predetermined dividing line, a grinding device is used to grind the back side of the wafer to thin the wafer to a predetermined thickness.

[0004] The grinding apparatus includes a work chuck for attracting and holding the wafer. A grinding unit is provided above the work chuck, the grinding unit including a cylindrical spindle arranged along the height direction (Z-axis direction). An annular grinding wheel is mounted at the lower end of the spindle.

[0005] For example, in axial feed grinding, the work chuck holding the wafer is rotated, and the grinding wheel, which is rotating with the spindle as the axis of rotation, moves downward along the Z-axis at a predetermined speed (i.e., grinding feed).

[0006] In order to accurately control the grinding amount or finished thickness of the wafer, the holding surface of the work chuck must be set as the reference in the height direction (i.e., the origin position), and a so-called setup is performed to enable the grinding device to identify the position of the lower surface of the grinding stone.

[0007] For example, this setting can be made when replacing a used grinding wheel with a new grinding wheel, or when the grinding stone has worn out with use. Also, this setting can be made as needed when replacing a used work chuck with a new work chuck, or after what is called self-grinding of the holding surface of the work chuck by grinding with a grinding stone.

[0008] In the setup of a grinding apparatus, the following manual setting is generally performed: after the operator places a reference plate (block gauge) of predetermined thickness on the holding surface, the grinding unit feeds the grinding stone so that the lower surface of the grinding stone contacts the predetermined upper surface of the reference plate (see, for example, Patent Document 1). Previous Art Documents Patent Documents

[0009] Patent Document 1: Japanese Patent Application Publication No. 2013-253837 [Summary of the Invention]

[0010] The problem the invention aims to solve

[0011] However, in manual setup, in addition to the higher time required by the operator, there is also the possibility that the grinding device or grinding wheel may be damaged by the reference plate due to operational errors if manual setup is performed every time.

[0012] This invention was made in view of the aforementioned problems, and its object is to reduce the working hours performed by operators in the setup of grinding equipment, and to reduce the possibility of operational errors caused by manual settings. Means for solving the problems.

[0013] According to one aspect of the present invention, a grinding apparatus for grinding a workpiece can be provided, the grinding apparatus comprising: a work chuck having a holding surface for holding the workpiece and being rotatable about a predetermined rotation axis; a grinding unit disposed above the work chuck and having a spindle, wherein a grinding wheel is mounted on the lower end of the spindle, the grinding wheel having a plurality of grinding stones arranged along the circumference of the annular wheel base on the lower surface side of the wheel base; and a moving mechanism for moving the work chuck and the grinding unit along a predetermined rotation axis. The grinding unit moves relative to the grinding wheel in a fixed direction to bring the holding surface close to the grinding wheel; the detection unit has a light-emitting part and a light-receiving part, the light-emitting part including a light-emitting element and a lens for irradiating a strip-shaped laser beam onto the lower surface of the wheel base adjacent to at least one grinding stone in the radial direction of the grinding wheel; the light-receiving part includes a light-receiving element for receiving the reflected light of the laser beam; and a control unit having a processor and memory, and controlling the grinding unit, the moving mechanism, and the detection unit. The control unit includes: a holding surface position memory unit that stores the relative height position of the holding surface with respect to the grinding wheel in a predetermined direction; a first distance calculation unit that calculates a first distance in the predetermined direction from the detection unit to the lower surface of the at least one grinding stone; and a lower surface position calculation unit that calculates the position of the lower surface of the at least one grinding stone with the holding surface as a reference, based on the height position stored in the holding surface position memory unit and the first distance calculated by the first distance calculation unit.

[0014] Preferably, when the grinding stone contacts the upper surface of the 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 set as PA, the thickness of the reference piece from the upper surface to the lower surface is set as D, the first distance from the detection unit to the lower surface of the at least one grinding stone is set as B1, and when the reference piece has been removed from the holding surface and the first distance from the detection unit to the lower surface of the at least one grinding stone is set as Z1, the lower surface position calculation unit uses (Equation 1) Z3 = Z1 - (B1 - D) and (Equation 2) PC = PA + Z3 to calculate the height position PC of the lower surface of the at least one grinding stone with the holding surface as a reference when the reference piece has been removed from the holding surface.

[0015] Furthermore, preferably, the control unit further includes a blade tip length calculation unit, which calculates the blade tip length of the at least one grinding stone 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 stone.

[0016] Furthermore, preferably, the control unit further includes a center deviation calculation unit, which calculates the deviation between the rotation center of the spindle and the center of the outer peripheral surface of the plurality of grinding stones based on the light reception data detected by the detection unit when the grinding wheel is rotated. Effects of the Invention

[0017] The control unit of one type of grinding apparatus of the present invention can use a detection unit employing a laser beam to calculate the position of the lower surface of at least one grinding stone with the holding surface as a reference. Therefore, the time spent by the operator in placing the reference piece on the holding surface and then retrieving it can be reduced, and the possibility of operational errors caused by manual setting can be reduced.

Implementation Method

[0019] Form used to implement the invention

[0020] Referring to the accompanying drawings, one embodiment of the present invention will be described. FIG1 is a perspective view of the grinding apparatus 2. The X-axis direction (front-back direction), Y-axis direction, and Z-axis direction (up-down direction) shown in FIG1 and the following figures are mutually orthogonal.

[0021] The grinding device 2 is a manual type in which the wafer (workpiece) 11 is moved in and out by an operator. However, the grinding device 2 can also be a fully automatic type that automatically performs grinding and cleaning in addition to moving the wafer 11 in and out.

[0022] The grinding apparatus 2 has a base 4 that supports the constituent elements of the grinding apparatus 2. A rectangular opening 4a is formed on the upper surface of the base 4, with its long side arranged along the X-axis direction. A ball screw type X-axis direction moving mechanism 6 is provided at the lower part of the opening 4a.

[0023] Furthermore, Figure 1 shows the approximate location of the X-axis direction moving mechanism 6. The X-axis direction moving mechanism 6 has a pair of guide rails (not shown) configured to be substantially parallel to the X-axis direction. An X-axis direction moving plate (not shown) is slidably mounted on the pair of guide rails.

[0024] A nut portion (not shown) is provided on the lower surface side of the moving plate in the X-axis direction, and a ball screw (not shown) is rotatably connected to the nut portion. The ball screw is arranged between a pair of guide rails and is approximately parallel to the X-axis direction.

[0025] A drive source (not shown) such as a stepper motor is connected to one end of the ball screw. When the drive source is activated, the X-axis moving plate moves along the X-axis direction. A rotary drive source (not shown) such as a motor for rotating the worktable 8 is provided on the upper part of the X-axis moving plate.

[0026] Furthermore, a rotating body (not shown) that functions as a rotation axis 10 (see Figure 2) is disposed on the upper part of the moving plate in the X-axis direction, and the lower surface of a circular plate-shaped work stand 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.

[0027] An endless belt (not shown) is mounted on the driven pulley of the rotating body and the drive pulley (not shown) of the rotary drive source. When the rotary drive source is activated, the work table 8 rotates around the predetermined rotation axis 10 (see Figure 2).

[0028] The worktable 8 is rotatably supported by a worktable base (not shown) via a bearing (not shown), and the worktable base is supported on the upper surface of the X-axis moving plate by a tilt adjustment mechanism (not shown).

[0029] The tilt adjustment mechanism has one fixed axis (not shown) and two movable axes (not shown) that can each change length along the Z-axis direction, thereby adjusting the tilt of the worktable base and the work clamp 8.

[0030] Here, the structure of the work clamp 8 will be described with reference to FIG7. The work clamp 8 has a circular plate-shaped frame 12 formed of ceramic or the like. A circular plate-shaped recess is formed on the upper surface of the frame 12.

[0031] A plurality of flow paths 12a are radially formed on the bottom surface of the recess of the frame 12. A central flow path 12b is formed in the frame 12, extending through the center of the bottom surface of the frame 12. One end of the central flow path 12b is connected to one of the plurality of flow paths 12a, and the other end of the central flow path 12b is connected to an suction source (not shown) such as an ejector or a vacuum pump.

[0032] A porous plate 14, formed of porous ceramic in the shape of a circular plate, is fixed in the recess of the frame 12. The porous plate 14 has a generally flat bottom surface and a conical upper surface that protrudes slightly from the center than from the outer periphery. Negative pressure can be transmitted from the suction source to the upper surface of the porous plate 14.

[0033] The upper surface of the porous plate 14 is substantially flush with the upper surface of the frame 12, forming a holding surface 8a for attracting and holding the wafer 11. By adjusting the tilt of the rotation axis 10 of the work chuck 8 using the tilt adjustment mechanism described above, a portion of the holding surface 8a can be configured to be substantially parallel to the XY plane.

[0034] Here, returning to Figure 1. The worktable 8 is located on the rectangular worktable cover 16, and on both sides of the worktable cover 16 in the X-axis direction, there are serpentine cover members 18 that can extend and retract in the X-axis direction. Furthermore, in Figure 1, only the cover member 18 on one side in the X-axis direction is marked with a symbol.

[0035] The work chuck 8 moves between the loading / unloading area A1 located in front of the opening 4a (on one side of the X-axis direction) and the grinding area A2 located behind the opening 4a (on the other side of the X-axis direction) via the X-axis moving mechanism 6. A circular wafer 11 can be placed on the work chuck 8 which is already configured in the loading / unloading area A1.

[0036] Wafer 11 is, for example, a silicon disc-shaped substrate on which a plurality of devices (not shown) are formed on the front side 11a. However, wafer 11 can also be formed using compound semiconductors such as silicon carbide (SiC) and gallium nitride (GaN), or other materials.

[0037] A protective tape 13 made of resin for device protection can be attached to the front side 11a of the wafer 11. When the front side 11a is held by the holding surface 8a through the protective tape 13, the back side 11b of the wafer 11 is exposed above (see Figure 4).

[0038] A cuboid column 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 20. The grinding feed mechanism 22 has a pair of tracks 24 fixed to one of the front surfaces of the column 20.

[0039] A Z-axis moving plate 26 is slidably mounted on each track 24 via a slider (not shown). A nut (not shown) is provided on the rear side of the Z-axis moving plate 26. A ball screw 28, which is arranged along the Z-axis between a pair of tracks 24, is rotatably connected to the nut.

[0040] A drive source 30, such as a stepper motor, is connected to the upper end of the ball screw 28. As long as the ball screw 28 is rotated by the drive source 30, the Z-axis moving plate 26 moves along the track 24 in the Z-axis direction.

[0041] A grinding unit 32 is fixed on the front surface of the Z-axis moving plate 26 in a manner that allows it to move in the Z-axis direction (a predetermined direction) by means of the grinding feed mechanism 22. The grinding unit 32 is fixed to the Z-axis moving plate 26 by means of a cylindrical retaining member 34 that is fixed to the front surface of the Z-axis moving plate 26.

[0042] A portion of a cylindrical spindle housing 36, which is arranged substantially parallel to the Z-axis direction, is disposed inside the retaining member 34. A portion of a cylindrical spindle 38 (see Figure 7) arranged along the Z-axis direction is rotatably housed within the spindle housing 36.

[0043] A rotation drive source 40, such as a motor, is provided at the upper end of the main shaft 38. The lower end of the main shaft 38 protrudes further downward than the lower end of the main shaft housing 36 (see Figure 7). A circular plate-shaped wheel seat 42 is fixed at the lower end of the main shaft 38.

[0044] On the lower surface of the wheel base 42, an annular grinding wheel 44 is mounted by means of fastening components such as screws (not shown). The grinding wheel 44 has an annular wheel base 46 formed of a metal material such as aluminum alloy, and a plurality of grinding stones 48 fixed to the lower surface 46a side of the wheel base 46.

[0045] A plurality of grinding stones 48 are arranged in a ring along the circumferential direction of the lower surface 46a of the wheel base 46, with gaps between adjacent grinding stones 48. The grinding stones 48 are formed by mixing abrasive grains such as diamond or cBN (cubic boron nitride) with a bonding material such as metal, ceramic, or resin, and then molding and firing them.

[0046] A grinding water supply nozzle (not shown) is provided below the grinding unit 32. The grinding water supply nozzle is used to supply grinding water such as pure water to the contact area 11c between the wafer 11 and the grinding stone 48 during grinding (see Figure 5).

[0047] As shown in Figure 2, a laser displacement meter (detection unit) 50 is provided behind the workbench cover 16. Figure 2 is an enlarged perspective view of the workbench 8 and the laser displacement meter 50, and Figure 3 is a partial cross-sectional side view showing the outline of the laser displacement meter 50.

[0048] As shown in FIG3, the laser displacement meter 50 has a light-emitting part 54 housed in a rectangular parallelepiped housing 52. The light-emitting part 54 has a light-emitting element 54a such as a semiconductor laser (laser diode).

[0049] A laser beam with a predetermined wavelength can be emitted from the light-emitting element 54a. The laser beam emitted from the light-emitting element 54a will be incident on a linear laser generator (hereinafter referred to as lens 54b) such as a Powell lens, a plano-concave lens, or a cylindrical lens.

[0050] The laser beam is shaped by lens 54b into a laser beam L with a predetermined length along a direction orthogonal to the direction of travel of the laser beam (Z-axis direction in this example) (X-axis direction in this example), and outputs a laser beam L that is approximately uniform in the X-axis direction.

[0051] A strip-shaped laser beam L is emitted from a rectangular opening 52a formed on the top of the housing 52 and having a long side along the X-axis, toward the object (in this example, the grinding stone 48 and the wheel base 46). The reflected light from the laser beam L, which diffuses and reflects off the object, is received by the light receiving unit 56.

[0052] The light receiving unit 56 is disposed in the housing 58 adjacent to the housing 52 in the Y-axis direction. The light receiving unit 56 has a condensing lens 62, which is used to focus the reflected light that passes through the circular opening 58a formed in the upper part of the housing 58 onto the CMOS (Complementary Metal-Oxide-Semiconductor) sensor (light receiving element) 60.

[0053] Furthermore, the condenser lens 62 can be a single lens, or it can be composed of multiple lenses, as in an Ernostar-type lens group. The CMOS sensor 60 has multiple photoelectric conversion elements (not shown) arranged in a two-dimensional form.

[0054] Each photoelectric conversion element is a light sensor, such as a phototransistor. Each photoelectric conversion element performs photoelectric conversion on the reflected light from the object at a predetermined sampling period and outputs a voltage signal corresponding to the amount of light received.

[0055] The voltage signal (i.e., the analog signal) can be converted into a digital signal by a predetermined processing circuit (not shown) having an analog-to-digital converter (ADC) and then processed by the control unit 70 described below.

[0056] The laser displacement meter 50 irradiates the grinding wheel 44 from below the grinding wheel 44 in such a way that the long side of the laser beam L is along the radial direction of the wheel base 46 (see Figure 4).

[0057] In this case, the laser beam L covers at least one grinding stone 48 and the lower surface 46a of the wheel base 46 adjacent to at least one grinding stone 48 in the radial direction of the grinding wheel 44 (i.e., wheel base 46).

[0058] The laser beam L is diffused and reflected from the lower surface 46a of the wheel base 46 (see Figure 7) or the lower surface 48a of the grinding stone 48, and is received by the CMOS sensor 60.

[0059] Since the light receiving position of the CMOS sensor 60 changes according to the distance from the light-emitting part 54 to the reflection position, the distance to the reflection position of the object can be measured according to the light receiving position of the CMOS sensor 60 (triangulation method).

[0060] For example, with the grinding wheel 44 positioned at a height of about 60 mm to 90 mm away from the laser displacement meter 50 in the Z-axis direction, the first distance B1 (see Figure 7) and the first distance Z1 (see Figure 9) from the laser displacement meter 50 to the lower surface 48a of the grinding stone 48 can be measured.

[0061] Similarly, the laser displacement meter 50 can be used to measure the second distance B2 (see Figure 7) and the second distance Z2 (see Figure 9) from the laser displacement meter 50 to the lower surface 46a of the wheel base 46.

[0062] Furthermore, the protrusion of the grinding stone 48 from the wheel base 46 (i.e., the tip length, also known as the grinding wheel tooth (segment) height) can be calculated by the difference between the first distance B1 and the second distance B2, or the difference between the first distance Z1 and the second distance Z2.

[0063] Figure 4 is an enlarged perspective view of the work chuck 8, grinding wheel 44, and laser displacement meter 50 under laser beam L irradiation, and Figure 5 is a top view of the work chuck 8, grinding wheel 44, and laser displacement meter 50. Furthermore, the grinding wheel 44 is indicated by dashed lines in Figure 5.

[0064] As shown in Figure 1, the grinding device 2 has a control unit 70, which controls the operation of the X-axis direction moving mechanism 6, the rotary drive source, the tilt adjustment mechanism, the suction source, the work table 8, the grinding feed mechanism 22, the grinding unit 32, the laser displacement meter 50, etc.

[0065] The control unit 70 is constructed by a computer, which includes, for example, a processor (processing device) represented by a CPU (Central Processing Unit) and memory (memory device).

[0066] The memory device includes main memory devices such as DRAM (Dynamic Random Access Memory), SRAM (Static Random Access Memory), and ROM (Read Only Memory), and auxiliary memory devices such as flash memory, hard disk drive, and solid-state drive.

[0067] The auxiliary memory device stores software containing a predetermined program. The processing device and other devices can be operated according to this software, thereby realizing the function of the control unit 70.

[0068] Part of the auxiliary memory device functions as a holding surface position memory unit 72, which stores the relative height position PA of the holding surface 8a relative to the grinding wheel 44 in the Z-axis direction. In this embodiment, the holding surface position memory unit 72 stores the height position PA of the holding surface 8a relative to the grinding wheel 44 when the lower surface 48a of the grinding stone 48 contacts the reference plate 64 (see Figure 7).

[0069] Furthermore, the control unit 70 can control the amount of movement of the grinding wheel 44 in the Z-axis direction by controlling the drive source 30. Therefore, once the height position PA is memorized in the holding surface position memory unit 72, the control unit 70 can always keep track of the relative height position of the grinding wheel 44 (e.g., the lower surface 46a of the wheel base 46) as long as there is no subsequent replacement of the work chuck 8 or correction of the shape of the holding surface 8a.

[0070] A first program is stored in the auxiliary memory device. The first program is executed by the processor and functions as a first distance calculation unit 74. The first distance calculation unit 74 calculates the distance in the Z-axis direction from the laser displacement meter 50 to the lower surface 48a of the grinding stone 48 (first distance B1 (see Figure 7) and first distance Z1 (see Figure 9)) according to the light receiving position on the CMOS sensor 60.

[0071] Furthermore, a second program is stored in the auxiliary memory device. This second program is executed by the processor and functions as a lower surface position calculation unit 76. The lower surface position calculation unit 76 calculates the height position PC of the lower surface 48a of the grinding stone 48 with the holding surface 8a as a reference, based on the height position PA, the first distance B1, etc., already stored in the holding surface position memory unit 72 (see Figure 9). The method for calculating the height position PC will be described later.

[0072] Furthermore, a third program is stored in the auxiliary memory device. The third program is executed by the processor and functions as the tool tip length calculation unit 78. The tool tip length calculation unit 78 can, for example, calculate the tool tip length C of the grinding stone 48 (see Figure 7) based on the second distance B2 (see Figure 7) from the laser displacement meter 50 to the lower surface 46a of the wheel base 46 and the first distance B1.

[0073] Furthermore, for example, the tip length calculation unit 78 may also calculate the tip length C of the grinding stone 48 based on, for example, the second distance Z2 (see Figure 9) from the laser displacement meter 50 to the lower surface 46a of the wheel base 46 and the first distance Z1 (see Figure 9).

[0074] Specifically, the blade tip length calculation unit 78 calculates the blade tip 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).

[0075] Furthermore, a fourth program is stored in the auxiliary memory device. This fourth program is executed by a processor and functions as a center deviation calculation unit 80. The aforementioned center deviation calculation unit 80 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 stones 48 based on the light reception data detected by the laser displacement meter 50 when the grinding wheel 44 is rotated (see Figure 10). Furthermore, the method for calculating the deviation will be described later.

[0076] Incidentally, when grinding the wafer 11 with the grinding apparatus 2, the work chuck 8 is first positioned in the loading / unloading area A1. Then, after the front side 11a of the wafer 11 is attracted and held by the holding surface 8a, the work chuck 8 is moved towards the grinding area A2. Next, the work chuck 8 is rotated in a predetermined direction about the rotation axis 10.

[0077] Furthermore, while supplying grinding water from the grinding water supply nozzle to the contact area 11c and setting the spindle 38 as the rotation axis to make the grinding wheel 44 rotate in a predetermined direction, the grinding unit 32 is moved downward along the Z-axis direction at a predetermined speed by means of the grinding feed mechanism 22.

[0078] Thus, the work chuck 8 and the grinding unit 32 move relative to each other along the Z-axis so that the holding surface 8a approaches the grinding wheel 44, and when the lower surface 48a of the grinding stone 48 contacts the back side 11b of the wafer 11, the back side 11b is ground.

[0079] However, before the wafer 11 is ground, a process called setting is performed to enable the grinding device 2 to identify the position of the lower surface 48a of the grinding stone 48 that holds the surface 8a as a reference (i.e., the origin position) in the height direction.

[0080] Next, the setup of the grinding apparatus 2 will be explained. Typically, the grinding apparatus 2 is set manually. In manual setup, the operator first places a reference plate (gauge block) 64 of predetermined thickness in a predetermined area of ​​the holding surface 8a.

[0081] Next, the grinding unit 32 is fed to grind, so that the lower surface 48a of the grinding stone 48 contacts the predetermined upper surface 64a of the reference plate 64. In this way, the grinding apparatus 2 identifies the position of the lower surface 48a of the grinding stone 48 with the holding surface 8a as the reference in the height direction.

[0082] However, in manual setup, in addition to the higher time required by the operator, there is also the risk of damage to the grinding device 2 and the grinding wheel 44 due to operational errors if manual setup is performed every time.

[0083] Therefore, in this embodiment, as shown in FIG6, in the first setting, the reference plate 64 is used for manual setting (S10 to S30), but in the second and subsequent settings, the laser displacement meter 50 is used for setting without using the reference plate 64 (S50).

[0084] This reduces the time required for operators to position the reference plate 64 on the holding surface 8a and then retrieve it. Furthermore, it reduces the likelihood of operational errors caused by manual setting. That is, it reduces the possibility of damage to the grinding device 2 or the grinding wheel 44 due to operational errors caused by the reference plate 64.

[0085] FIG6 is a flowchart for setting up this embodiment. In the reference piece placement step S10, an operator manually places the reference piece 64 on a predetermined area corresponding to the holding surface 8a of the contact area 11c. As shown in FIG7, the reference piece 64 has a generally flat lower surface 64b and a generally stepped upper surface 64a.

[0086] The distance from the lower surface 64b to the upper surface 64a varies in stages, for example, the thickness of the thickest region 64c1 is 5.05 mm, the thickness of the second thickest region 64c2 is 5.02 mm, and the thickness of the thinnest region 64c3 is 5.00 mm.

[0087] In this example, although the thickest area is used, it is also possible to decide which thickness of area to use. The thickness D of the reference sheet 64 used is input to the control unit 70 by the operator through an input device (not shown) such as a touch panel.

[0088] After the reference plate placement step S10, the grinding unit 32, which has been positioned above the worktable 8, is lowered. Then, the lower surface 48a of the grinding stone 48, which is located at a different position than directly above the laser displacement meter 50, contacts the upper surface 64a of the reference plate 64, which is located at a relative height position PB in the Z-axis direction of the holding surface 8a (contact step S20).

[0089] Furthermore, in the contact step S20, the holding surface position memory unit 72 stores the relative height position PA of the holding surface 8a with respect to the grinding wheel 44 in the Z-axis direction when the lower surface 48a contacts the reference plate 64.

[0090] After or simultaneously with the contact step S20, a first distance B1 is measured by laser displacement meter 50 up to the lower surface 48a of the grinding stone 48 (first measurement step S30). Figure 7 is a partial cross-sectional side view showing the first measurement step S30.

[0091] After the first measurement step S30, the reference plate 64 is removed from the holding surface 8a (removal step S40). Furthermore, during the period from the reference plate placement step S10 to the removal step S40, the spindle 38 of the grinding unit 32 and the work chuck 8 are not rotated.

[0092] After step S40, grinding of, for example, wafer 11 can be performed. Since the lower surface 48a side of the grinding stone 48 will wear down along with the grinding of wafer 11, the tip length C of the grinding stone 48 will become shorter (see Figure 9).

[0093] If the tool tip length C becomes shorter, even if the grinding wheel 44 is positioned at the height already configured in contact step S20, the distance from the lower surface 48a to the holding surface 8a will still be different from the thickness D. In such cases, the settings must be repeated in order to perform grinding with high precision.

[0094] Incidentally, even if the lower surface 48a of the grinding stone 48 wears down, the first distance Z1 from the laser displacement meter 50 to the lower surface 48a (see Figure 9) and the distance Z3 from the holding surface 8a to the lower surface 48a (see Figure 9) will increase in the same way. That is, the distance Z3 is a linear function of the coefficient (i.e., the tilt) of the first distance Z1 being 1.

[0095] As described above, when the first distance Z1 is the first distance B1, the distance Z3 is the thickness D (see Figure 7). Furthermore, 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 formula 1.

[0096] [Formula 1]

[0097] Figure 8 is a graph showing the distance from the holding surface 8a and the laser displacement meter 50 to the lower surface 48a of the grinding stone 48. By calculating the distance Z3, the height position PC of the lower surface 48a of the grinding stone 48 with the holding surface 8a as the reference can be calculated by the following formula 2.

[0098] [Formula 2]

[0099] The lower surface position calculation unit 76 has a program corresponding to the above formulas 1 and 2, and can calculate the height position PC of the lower surface 48a with the holding surface 8a as a reference from the first distance B1, the thickness D, the relative height position PA, and the first distance Z1.

[0100] After grinding the wafer 11, when calculating the height position PC of the lower surface 48a with the holding surface 8a as a reference, a laser beam L is irradiated onto the grinding wheel 44 which is arranged at an arbitrary height to measure the first distance Z1 from the laser displacement meter 50 to the lower surface 48a of the grinding stone 48 (second measurement step S50).

[0101] Figure 9 is a partial cross-sectional side view showing the second measurement step S50. As long as the first distance Z1 is obtained in the second measurement step S50, the lower surface position calculation unit 76 can calculate the height position PC of the lower surface 48a of the grinding stone 48 during the second measurement step S50 with the holding surface 8a as the reference (lower surface height position calculation step S60), as described above.

[0102] In the second measurement step S50, the laser displacement meter 50 can be used for setting without using the reference plate 64. This reduces the time required for operators to place the reference plate 64 on the holding surface 8a and then retrieve it.

[0103] In addition, the possibility of operational errors caused by manual settings can be reduced. That is, the possibility of the grinding device 2 or the grinding wheel 44 being damaged by the reference plate 64 due to operational errors can be reduced.

[0104] Furthermore, since the reference plate 64 is not used in the second measurement step S50, it has the following advantages: the setting can be performed even during the grinding of the wafer 11 or the rotation of the grinding wheel 44. That is, the setting can be performed even when the work chuck 8 and the grinding wheel 44 are rotating.

[0105] Furthermore, during the rotation of the grinding wheel 44, the ribbon-shaped laser beam L irradiates the lower surfaces 48a of the plurality of grinding stones 48 and the lower surfaces 46a of the wheel base 46 adjacent to each grinding stone 48 in the radial direction of the grinding wheel 44.

[0106] After step S60, if the laser displacement meter 50 is used for setting without using the reference plate 64 again ("Yes" in S70), the process returns to S50. Conversely, if no setting is performed ("No" in S70), the process ends.

[0107] Incidentally, 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 stones 48 in the second measurement step S50 (see Figure 10).

[0108] Figure 10 is a diagram showing the deviation of the center 48c of the outer peripheral side surface 48b of a plurality of grinding stones 48 relative to the rotation center 38a of the spindle 38. 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 holder 42, and may be, for example, about 100 μm.

[0109] Figure 10 shows the outer peripheral side 48b of the grinding wheel 44 when it is in the rearmost rear position E1 when viewed from above, and the outer peripheral side 48b of the grinding wheel 44 when it is in the foremost front position E2, with solid lines.

[0110] When the rotation center 38a and the center 48c are offset in this way, the position of the outer periphery of the lower surface 48a of the grinding stone 48 located directly above the laser displacement meter 50 will change with the rotation of the grinding wheel 44.

[0111] Figure 11 is a graph showing the time change of the position of the outer periphery of the lower surface 48a of the grinding stone 48. In Figure 11, the horizontal axis represents time, and the vertical axis represents the position of the outer periphery of the lower surface 48a of the grinding stone 48 located directly above the laser displacement meter 50.

[0112] In Figure 11, the grinding wheel 44 is located at the forward position E2 at time 0 and T, and at the rear position E1 at time T / 2. The center deviation calculation unit 80 calculates the position of the outer periphery in the forward position E2 and the distance F between the outer periphery in the rear position E1, according to the light receiving position on the CMOS sensor 60.

[0113] Since the deviation between the rotation center 38a and the center 48c corresponds to half of the distance F, the deviation can be calculated by the center deviation calculation unit 80 by calculating F / 2 (deviation calculation step). The calculated deviation will be displayed on a display device (not shown) such as a touch panel that has been installed on the grinding device 2.

[0114] The operator can also correct the position of the center 48c of the outer peripheral side 48b when the deviation between the rotation center 38a and the center 48c is not zero. For example, the position of the center 48c can be corrected by hitting the side of the grinding wheel 44 with a hammer while the grinding unit 32 has stopped operating.

[0115] Furthermore, the position of the center 48c of the outer peripheral side surface 48b can be corrected by pressing the dressing member against the outer peripheral side surface 48b while the grinding wheel 44 has been rotated at a predetermined number of rotations. In addition, the structure and method of the above embodiment can be appropriately modified and implemented as long as they do not depart from the purpose of the present invention. [Simplified Explanation of the Diagram]

[0018] Figure 1 is a perspective view of the grinding apparatus. Figure 2 is an enlarged perspective view of the work chuck and laser displacement gauge. Figure 3 is a partial cross-sectional side view showing the outline of the laser displacement gauge. Figure 4 is an enlarged perspective view of the work chuck, grinding wheel, and laser displacement gauge. Figure 5 is a top view of the work chuck, grinding wheel, and laser displacement gauge. Figure 6 is a flowchart for setting up the apparatus. Figure 7 is a partial cross-sectional side view showing the first measurement step. Figure 8 is a graph showing the distance from the holding surface and laser displacement gauge to the lower surface of the grinding stone. Figure 9 is a partial cross-sectional side view showing the second measurement step. Figure 10 is a graph showing the deviation of the center of the outer peripheral surface of a plurality of grinding stones relative to the rotation center of the spindle. Figure 11 is a graph showing the time variation of the position of the outer peripheral edge of the lower surface of the grinding stone.

Claims

1. A grinding apparatus for grinding a workpiece, characterized in that it comprises: a work chuck having a holding surface for holding the workpiece and being rotatable about a predetermined rotation axis; a grinding unit disposed above the work chuck and having a spindle, wherein a grinding wheel is mounted on the lower end of the spindle, the grinding wheel having a plurality of grinding stones arranged along the circumference of the annular wheel base on the lower surface side of the grinding wheel base; and a moving mechanism for moving the work chuck and the grinding unit relative to each other in a predetermined direction so that the holding surface approaches the grinding wheel; The detection unit includes a light-emitting unit and a light-receiving unit. The light-emitting unit includes a light-emitting element and a lens for irradiating a strip-shaped laser beam onto the lower surface of the wheel base of at least one grinding stone, which is adjacent to the at least one grinding stone in the radial direction of the grinding wheel. The light-receiving unit includes a light-receiving element for receiving reflected light from the laser beam. The control unit includes a processor and a memory, and controls the grinding unit, the moving mechanism, and the detection unit. The control unit includes: a holding surface position memory unit for storing the relative height position of the holding surface with respect to the grinding wheel in a 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 stone; and a lower surface position calculation unit for calculating the position of the lower surface of the at least one grinding stone with the holding surface as a reference, based on the height position stored in the holding surface position memory unit and the first distance calculated by the first distance calculation unit. When the grinding stone contacts the upper surface of the 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 set as PA, the thickness of the reference piece from the upper surface to the lower surface is set as D, the first distance from the detection unit to the lower surface of the at least one grinding stone is set as B1, and when the reference piece has been removed from the holding surface, the first distance from the detection unit to the lower surface of the at least one grinding stone is set as Z1. The lower surface position calculation unit uses the following formulas 1 and 2 to calculate the height position PC of the lower surface of the at least one grinding stone with the holding surface as a reference when the reference piece has been removed from the holding surface. [Formula 1] [Formula 2] 2. The grinding apparatus of claim 1, wherein the control unit further includes a tip length calculation unit, the tip length calculation unit calculating the tip length of the at least one grinding stone 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 stone.

3. The grinding apparatus of claim 1 or 2, wherein the control unit further includes a center deviation calculation unit, which calculates the deviation between the rotation center of the spindle and the center of the outer peripheral surface of the plurality of grinding stones based on the light reception data detected by the detection unit when the grinding wheel is rotated.

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