Grinding device

Abstract

This invention provides a grinding apparatus that reduces operator working hours and lowers the possibility of operational errors caused by manual settings. The grinding apparatus includes a chuck table, a grinding unit, a moving mechanism for moving the chuck table and 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 moving mechanism and the detection unit. The control unit includes: a holding surface position storage 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 from the detection unit to the lower surface of the grinding wheel in a predetermined direction; and a lower surface position calculation unit that calculates the position of the lower surface of the grinding wheel with the holding surface as a reference, based on the height position stored in the holding surface position storage 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. Background Technology

[0002] Semiconductor device chips are incorporated into various electronic devices such as mobile phones and personal computers. These chips have multiple predefined dividing lines arranged in a grid pattern on their front side. They are manufactured by processing semiconductor wafers (hereinafter referred to as wafers) in areas defined by these dividing lines, where ICs (Integrated Circuits) and other devices are formed.

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

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

[0005] For example, in feed grinding, the chuck table that holds the wafer is rotated, and the grinding wheel that rotates around the spindle moves downward along the Z-axis at a predetermined speed (i.e., grinding feed is performed).

[0006] In order to control the grinding amount and finished thickness of the wafer with high precision, it is necessary to use the holding surface of the chuck stage as a reference in the height direction (i.e., the origin position) and to make the grinding device recognize the position of the lower surface of the grinding wheel.

[0007] For example, this setting is configured when replacing a used grinding wheel with a new one, or when the grinding wheel wears out with use. Additionally, it is configured as needed when replacing a used chuck table with a new one, or after so-called self-grinding where the holding surface of the chuck table is ground using a grinding wheel.

[0008] In the setup of a grinding apparatus, the grinding unit is typically manually set up so that the lower surface of the grinding wheel contacts the upper surface of the reference plate after the operator places a reference plate (gauge) of a specified thickness on the holding surface (for example, see Patent Document 1).

[0009] Patent Document 1: Japanese Patent Application Publication No. 2013-253837

[0010] However, manual setup not only consumes the operator's time, but also, if manual setup is performed every time, there is a possibility that the reference plate may be damaged due to operational errors, causing damage to the grinding device or grinding wheel. Summary of the Invention

[0011] The present invention was made in view of the above-mentioned problems, and its object is to reduce the operator's working hours and reduce the possibility of operational errors caused by manual settings in the setting of grinding equipment.

[0012] According to one aspect of the present invention, a grinding apparatus is provided for grinding a workpiece, characterized in that...

[0013] The grinding apparatus includes: a chuck table having a holding surface for holding the workpiece and capable of rotating about a predetermined axis of rotation; a grinding unit positioned above the chuck table, the grinding unit having a spindle with a grinding wheel mounted at its lower end, the grinding wheel having a plurality of grinding tools arranged circumferentially on the lower surface of an annular grinding wheel base; a moving mechanism for moving the chuck table and the grinding unit relative to each other in a predetermined direction such that the holding surface approaches the grinding wheel; and a detection unit having a light-emitting part and a light-receiving part, the light-emitting part including illumination over at least one grinding tool and the lower surface of the grinding wheel base adjacent to the at least one grinding tool in the radial direction of the grinding wheel. The grinding unit comprises a light-emitting element and a lens that emits a strip-shaped laser beam, the light-receiving part including a light-receiving element for receiving reflected light from the laser beam; and a control unit having a processor and a memory for controlling the grinding unit, the moving mechanism, and the detection part. The control unit includes: a holding surface position storage 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 from the detection part to the lower surface of the at least one grinding wheel in the predetermined direction; and a lower surface position calculation unit that calculates the position of the lower surface of the at least one grinding wheel with the holding surface as a reference based on the height position stored in the holding surface position storage unit and the first distance calculated by the first distance calculation unit.

[0014] Preferably, when the grinding wheel contacts the upper surface of the reference piece disposed on the retaining surface, the relative height position of the retaining surface with respect to the grinding wheel in the specified direction is set as P. AThe thickness from the upper surface to the lower surface of the reference piece is defined as D, the first distance from the detection unit to the lower surface of the at least one grinding wheel is defined 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 wheel is defined as Z1. In the above case, the lower surface position calculation unit uses Z3 = Z1 - (B1 - D) (Mathematical Formula 1) and P C =P A +Z3 (Mathematical Formula 2) is used to calculate the height position P of the lower surface of the at least one grinding wheel with the retaining surface as a reference, in the state where the reference piece has been removed from the retaining surface. C .

[0015] In addition, preferably, the control unit also includes a tool tip length calculation unit, which calculates the tool tip length of the at least one grinding tool based on a second distance from the detection unit to the lower surface of the grinding wheel base and a first distance from the detection unit to the lower surface of the at least one grinding tool.

[0016] In addition, preferably, the control unit also includes a center offset calculation unit, which calculates the offset between the rotation center of the spindle and the center of the outer peripheral side surface of the plurality of grinding tools based on the light-receiving data detected by the detection unit when the grinding wheel is rotated.

[0017] In one aspect of the present invention, the control unit of the grinding apparatus is capable of calculating the position of the lower surface of at least one grinding wheel with reference to a holding surface using a detection unit employing a laser beam. Therefore, the operator can reduce the time spent placing the reference piece on the holding surface and then retrieving it, and further reduce the possibility of operational errors caused by manual settings. Attached Figure Description

[0018] Figure 1 It is a three-dimensional diagram of the grinding device.

[0019] Figure 2 It is an enlarged 3D view of the chuck table and laser displacement gauge.

[0020] Figure 3 This is a partial cross-sectional side view showing the outline of the laser displacement gauge.

[0021] Figure 4 It is an enlarged 3D view of the chuck table, grinding wheel, and laser displacement gauge.

[0022] Figure 5 It is a top view of the chuck table, grinding wheel, and laser displacement gauge.

[0023] Figure 6 This is a flowchart used for setting up.

[0024] Figure 7 This is a partial cross-sectional side view showing the first measurement procedure.

[0025] Figure 8 It is a graph showing the distance from the holding surface and the laser displacement gauge to the lower surface of the grinding wheel.

[0026] Figure 9 This is a partial cross-sectional side view showing the second measurement procedure.

[0027] Figure 10 This is a diagram showing the offset of the center of the outer peripheral side of multiple grinding wheels relative to the rotation center of the spindle.

[0028] Figure 11 It is a graph showing the time-varying position of the outer periphery of the lower surface of the grinding wheel.

[0029] Label Explanation

[0030] 2: Grinding device; 4: Base; 4a: Opening; 6: X-axis moving mechanism; 8: Chuck table; 8a: Holding surface; 10: Rotation axis; 11: Wafer (workpiece); 11a: Front side; 11b: Back side; 11c: Contact area; 13: Protective belt; 12: Frame; 12a: Flow path; 12b: Central flow path; 14: Porous plate; 16: Table cover; 18: Cover component; 20: Column Part; 22: Grinding feed mechanism (moving mechanism); 24: Track; 26: Z-axis moving plate; 28: Ball screw; 30: Drive source; 32: Grinding unit; 34: Holding component; 36: Spindle housing; 38: Spindle; 38a: Rotation center; 40: Rotation drive source; 42: Wheel seat; 44: Grinding wheel; 46: Grinding wheel base; 46a: Lower surface; 48: Grinding tool; 48a: Lower surface ; 48b: Outer peripheral side; 48c: Center; 50: Laser displacement gauge (detection unit); 52: Housing; 52a: Opening; 54: Light-emitting part; 54a: Light-emitting element; 54b: Lens; 56: Light-receiving part; 58: Housing; 58a: Opening; 60: CMOS sensor; 62: Condensing lens; 64: Reference plate; 64a: Upper surface; 64b: Lower surface; 64c1, 64c2, 64c3: Thickness; 70: Control unit; 72: Holding surface position storage unit; 74: First distance calculation unit; 76: Lower surface position calculation unit; 78: Tool tip length calculation unit; 80: Center offset calculation unit; A1: Loading / unloading area; A2: Grinding area; B1: First distance; B2: Second distance; C: Tool tip length; D: Thickness; E1: Rear position; E2: Front position; F: Distance; L: Laser beam; P A P B P CZ1: Altitude position; Z2: First distance; Z3: Second distance; Z4: Distance. Detailed Implementation

[0031] An embodiment of one aspect of the present invention will be described with reference to the accompanying drawings. Figure 1 This is a three-dimensional view of the grinding device 2. Figure 1 The X-axis (front-back direction), Y-axis, and Z-axis (up-down direction) shown in the following figures are perpendicular to each other.

[0032] The grinding device 2 is manually operated by the operator to load and unload the wafer (workpiece) 11. However, in addition to loading and unloading the wafer 11, the grinding device 2 can also be a fully automatic type that automatically performs grinding and cleaning.

[0033] The grinding apparatus 2 has a base 4 that supports the structural elements of the grinding apparatus 2. A rectangular opening 4a with its long side arranged along the X-axis is formed on the upper surface of the base 4. A ball screw type X-axis moving mechanism 6 is provided at the lower part of the opening 4a.

[0034] In addition, Figure 1 The diagram shows the approximate location of the X-axis moving mechanism 6. The X-axis moving mechanism 6 has a pair of guide rails (not shown) arranged approximately parallel to the X-axis direction. An X-axis moving plate (not shown) is slidably mounted on the pair of guide rails.

[0035] A nut portion (not shown) is provided on the lower surface of the plate that moves in the X-axis direction. A ball screw (not shown) is rotatably connected to the nut portion and is arranged between a pair of guide rails that are approximately parallel to the X-axis direction.

[0036] A drive source, such as a stepper motor (not shown), 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. A rotary drive source, such as a motor (not shown), is provided on the upper part of the X-axis moving plate to rotate the chuck table 8.

[0037] Additionally, a rotation axis 10 is positioned above the moving plate in the X-axis direction (see reference). Figure 2 A rotating body (not shown) performs a function, the upper end of which is connected to the lower surface of a circular plate-shaped chuck worktable 8. A driven pulley (not shown) is provided at the lower end of the rotating body.

[0038] An annular 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 chuck table 8 rotates around a predetermined axis of rotation 10 (see reference). Figure 2 Rotate.

[0039] The chuck table 8 is rotatably supported on the table base (not shown) via bearings (not shown), and the table base is supported on the upper surface of the X-axis moving plate via a tilt adjustment mechanism (not shown).

[0040] The tilt adjustment mechanism has one fixed axis (not shown) and two movable axes (not shown) that can change length along the Z-axis direction respectively, and can adjust the tilt of the worktable base and the chuck worktable 8.

[0041] Here, refer to Figure 7 The structure of the chuck worktable 8 will be described. The chuck worktable 8 has a circular plate-shaped frame 12 made of ceramic or the like. A circular plate-shaped recess is formed on the upper surface of the frame 12.

[0042] Multiple flow paths 12a are radially formed on the bottom surface of the recess of the frame 12. In addition, a central flow path 12b is formed on the frame 12, penetrating the center of the bottom surface of the frame 12. One end of the central flow path 12b is connected to the multiple 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.

[0043] A porous plate 14, formed of porous ceramic, 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 is transmitted from the suction source to the upper surface of the porous plate 14.

[0044] The upper surface of the porous plate 14 is substantially the same as 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 chuck stage 8 using the tilt adjustment mechanism described above, a portion of the holding surface 8a is arranged substantially parallel to the XY plane.

[0045] Here, return Figure 1 The chuck table 8 is located on a rectangular table cover 16, and corrugated cover members 18 that can extend and retract in the X-axis direction are provided on both sides of the table cover 16. Additionally, in Figure 1 In the text, only the cover component 18 on one side in the X-axis direction is labeled.

[0046] The chuck stage 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 is placed on the chuck stage 8, which is located in the loading / unloading area A1.

[0047] The wafer 11 is, for example, a silicon disc-shaped substrate on the front side 11a on which multiple devices (not shown) are formed. However, the wafer 11 may also be formed from compound semiconductors such as silicon carbide (SiC) and gallium nitride (GaN), or from other materials.

[0048] A protective resin strip 13 for device protection is attached to the front side 11a of the wafer 11. When the front side 11a is held by the holding surface 8a via the protective strip 13, the back side 11b of the wafer 11 is exposed upwards (see reference). Figure 4 ).

[0049] 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 the front surface of the column 20.

[0050] 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.

[0051] A drive source 30, such as a stepper motor, is connected to the upper end of the ball screw 28. If the ball screw 28 is rotated using the drive source 30, the Z-axis moving plate 26 moves along the track 24 in the Z-axis direction.

[0052] A grinding unit 32 is fixed to the front surface of the Z-axis moving plate 26 in such a way that it can be moved along the Z-axis direction (a specified direction) by the grinding feed mechanism 22. The grinding unit 32 is fixed to the Z-axis moving plate 26 via a cylindrical holding member 34 fixed to the front surface of the Z-axis moving plate 26.

[0053] A portion of a cylindrical spindle housing 36, arranged substantially parallel to the Z-axis direction, is disposed inside the retaining component 34. A cylindrical spindle 38, arranged along the Z-axis direction, is rotatably housed within the spindle housing 36. Figure 7 Part of ).

[0054] A rotation drive source 40, such as an electric motor, is provided at the upper end of the spindle 38. The lower end of the spindle 38 protrudes downwards beyond the lower end of the spindle housing 36 (see reference). Figure 7 A circular plate-shaped wheel seat 42 is fixed at the lower end of the main shaft 38.

[0055] A ring-shaped grinding wheel 44 is mounted on the lower surface of the wheel base 42 by fastening components such as screws (not shown). The grinding wheel 44 has a ring-shaped grinding wheel base 46 formed of a metal material such as aluminum alloy and a plurality of grinding tools 48 fixed to the lower surface 46a side of the grinding wheel base 46.

[0056] Multiple grinding wheels 48 are arranged in a ring along the circumference of the lower surface 46a of the grinding wheel base 46, with gaps between adjacent grinding wheels 48. The grinding wheels 48 are formed, for example, by mixing abrasive grains such as diamond or cBN (cubic boron nitride) into a bonding material such as metal, ceramic, or resin, and then by molding, firing, etc.

[0057] Below the grinding unit 32 is a contact area 11c for contacting the wafer 11 and the grinding tool 48 during grinding (see reference). Figure 5 A grinding water supply nozzle (not shown) provides grinding water such as pure water.

[0058] like Figure 2 As shown, a laser displacement meter (detection unit) 50 is installed behind the worktable cover 16. Figure 2 This is an enlarged 3D view of the chuck table 8 and the laser displacement meter 50. Figure 3 This is a partial cross-sectional side view showing the outline of the laser displacement meter 50.

[0059] like Figure 3 As shown, the laser displacement meter 50 has a light-emitting part 54 housed in a cuboid housing 52. The light-emitting part 54 has a light-emitting element 54a such as a semiconductor laser (laser diode).

[0060] A laser beam with a specified wavelength is emitted from the light-emitting element 54a. The laser beam emitted from the light-emitting element 54a is incident on a laser beam generator such as a Powell lens, a Lineman lens, or a cylindrical lens (hereinafter referred to as lens 54b).

[0061] The laser beam passes through lens 54b along a direction perpendicular to the direction of travel of the laser beam (Z-axis direction in this example) (X-axis direction in this example) and has a specified length, and is shaped into a strip-shaped laser beam L that is output in a substantially uniform direction in the X-axis direction.

[0062] A strip-shaped laser beam L is directed toward the object (in this example, the grinding wheel 48 and the grinding wheel base 46) through a rectangular opening 52a formed at the top of the housing 52 and having a long side along the X-axis. The reflected light from the laser beam L diffusely reflected from the object is received by the light-receiving part 56.

[0063] The light-receiving part 56 is disposed in the housing 58 adjacent to the housing 52 along the Y-axis direction. The light-receiving part 56 has a condensing lens 62 for converging reflected light incident 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.

[0064] Alternatively, the condenser lens 62 can be a single lens or, like an Elnorst-type lens, composed of multiple lenses. The CMOS sensor 60 has multiple photoelectric conversion elements (not shown) arranged in a two-dimensional configuration.

[0065] Each photoelectric conversion element is a photoelectric sensor, such as a phototransistor. Each photoelectric conversion element performs photoelectric conversion on the reflected light from the object according to a specified sampling period and outputs a voltage signal corresponding to the amount of light received.

[0066] The voltage signal (i.e., analog signal) is converted into a digital signal by a specified processing circuit (not shown) having an analog-to-digital converter (ADC) and the like, and then processed by the control unit 70 described later.

[0067] The laser displacement gauge 50, for example, irradiates the grinding wheel 44 from below in a radial direction along the long side of the strip-shaped laser beam L on the grinding wheel base 46 (see reference). Figure 4 ).

[0068] In this case, the laser beam L irradiates at least one grinding wheel 48 and the lower surface 46a of the grinding wheel base 46 adjacent to at least one grinding wheel 48 in the radial direction of the grinding wheel 44 (i.e., grinding wheel base 46).

[0069] The laser beam L originates from the lower surface 46a of the grinding wheel base 46 (see reference). Figure 7 The lower surface 48a of the grinding wheel 48 diffusely reflects the light and is received by the CMOS sensor 60.

[0070] The light-receiving position of the CMOS sensor 60 varies depending on the distance from the light-emitting part 54 to the reflection position. Therefore, the distance to the reflection position of the object is measured based on the light-receiving position of the CMOS sensor 60 (triangulation method).

[0071] For example, with the grinding wheel 44 positioned at a height of approximately 60mm to 90mm away from the laser displacement meter 50 in the Z-axis direction, the first distance B1 from the laser displacement meter 50 to the lower surface 48a of the grinding wheel 48 (refer to...) Figure 7 ), the first distance Z1 (reference) Figure 9) to be measured.

[0072] Similarly, using laser displacement gauge 50, the second distance B2 from laser displacement gauge 50 to the lower surface 46a of grinding wheel base 46 (refer to...) is... Figure 7 ), the second distance Z2 (refer to) Figure 9 ) to be measured.

[0073] In addition, 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, the protrusion of the grinding wheel 48 from the grinding wheel base 46 (i.e., the tool tip length, also known as the segment height) is calculated.

[0074] Figure 4 This is an enlarged 3D view of the chuck table 8, grinding wheel 44, and laser displacement meter 50 under laser beam L irradiation. Figure 5 This is a top view of the chuck table 8, the grinding wheel 44, and the laser displacement meter 50. Additionally, in Figure 5 In the middle, the grinding wheel 44 is represented by a dashed line.

[0075] like Figure 1 As shown, the grinding device 2 has a control unit 70, which controls the operation of the X-axis moving mechanism 6, the rotary drive source, the tilt adjustment mechanism, the suction source, the chuck table 8, the grinding feed mechanism 22, the grinding unit 32, the laser displacement meter 50, etc.

[0076] The control unit 70 is, for example, a computer that includes a memory (storage device) and a processor (processing device) represented by a CPU (Central Processing Unit).

[0077] Storage devices include main storage devices such as DRAM (Dynamic Random Access Memory), SRAM (Static Random Access Memory), and ROM (Read Only Memory), as well as auxiliary storage devices such as flash memory, hard disk drives, and solid-state drives.

[0078] The auxiliary storage device stores software containing a prescribed program. By following this software, the processing device and other components are operated to perform the functions of the control unit 70.

[0079] Part of the auxiliary storage device serves as the relative height position P of the holding surface 8a with respect to the grinding wheel 44 in the Z-axis direction. AThe holding surface position storage unit 72 functions to store the grinding wheel 48's lower surface 48a and the reference plate 64 (see reference). Figure 7 The height position P of the holding surface 8a relative to the grinding wheel 44 during contact A .

[0080] Furthermore, the control unit 70, by controlling the drive source 30, can control the amount of movement of the grinding wheel 44 in the Z-axis direction. Therefore, if the height position P is adjusted... A Once the position is stored in the holding surface storage 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 grinding wheel base 46) as long as there is no replacement of the chuck table 8 or correction of the shape of the holding surface 8a.

[0081] A first program is stored in the auxiliary storage device. This first program is executed by the processor, thereby calculating the distance (first distance B1) in the Z-axis direction from the laser displacement meter 50 to the lower surface 48a of the grinding wheel 48 based on the light-receiving position on the CMOS sensor 60. Figure 7 ), the first distance Z1 (reference) Figure 9 The first distance calculation unit 74 functions as such.

[0082] Additionally, a second program is stored in the auxiliary storage device. This second program is executed by the processor, thereby determining the height position P based on the position stored in the holding surface storage unit 72. A The height position P of the lower surface 48a of the grinding wheel 48, with the holding surface 8a as the reference, is calculated using the first distance B1, etc. C (Refer to Figure 9 The lower surface position calculation unit 76 functions accordingly. Additionally, regarding the height position P... C The calculation method will be described later.

[0083] Furthermore, a third program is stored in the auxiliary storage device. This third program is executed by the processor, thereby functioning as the tool tip length calculation unit 78. The tool tip length calculation unit 78 can, for example, calculate based on a second distance B2 from the laser displacement meter 50 to the lower surface 46a of the grinding wheel base 46 (see reference). Figure 7 The tip length C of the grinding wheel 48 is calculated using the first distance B1 and the first distance B1 (refer to...). Figure 7 ).

[0084] Additionally, for example, the tool tip length calculation unit 78 can also calculate based on the second distance Z2 from the laser displacement meter 50 to the lower surface 46a of the grinding wheel base 46 (see reference). Figure 9 ) and the first distance Z1 (refer to) Figure 9 The tip length C of the grinding tool 48 is calculated using this method.

[0085] 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).

[0086] Furthermore, a fourth program is stored in the auxiliary storage device. This fourth program is executed by the processor, thereby calculating the offset between the rotation center 38a of the spindle 38 and the center 48c of the outer peripheral side surfaces 48b of the plurality of grinding wheels 48 based on the light-receiving data detected by the laser displacement meter 50 when the grinding wheel 44 is rotated (see reference). Figure 10 The center offset calculation unit 80 functions as the offset calculation unit. The method for calculating the offset will be described later.

[0087] Furthermore, when grinding the wafer 11 using the grinding apparatus 2, firstly, the chuck stage 8 is positioned in the loading / unloading area A1. Then, after holding the wafer 11 on the front side 11a using the holding surface 8a, the chuck stage 8 is moved towards the grinding area A2. Moreover, the chuck stage 8 is rotated about the rotation axis 10 in a predetermined direction.

[0088] In addition, grinding water is supplied from the grinding water supply nozzle to the contact area 11c, and while the grinding wheel 44 is rotated in a predetermined direction with the spindle 38 as the rotation axis, the grinding unit 32 is moved downward along the Z-axis direction at a predetermined speed by the grinding feed mechanism 22.

[0089] In this way, the chuck stage 8 and the grinding unit 32 move relative to each other along the Z-axis in such a way that the surface 8a is close to the grinding wheel 44, and when the lower surface 48a of the grinding tool 48 contacts the back side 11b of the wafer 11, the back side 11b is ground.

[0090] However, before grinding the wafer 11, a process (so-called setting) is performed to enable the grinding apparatus 2 to identify the position of the lower surface 48a of the grinding tool 48, which uses the holding surface 8a as a reference in the height direction (i.e., the origin position).

[0091] Next, the setup of the grinding apparatus 2 will be explained. Typically, the grinding apparatus 2 is set up manually. In manual setup, the operator first places a reference plate (gauge block) 64 of a specified thickness in a designated area of ​​the holding surface 8a.

[0092] Next, the grinding unit 32 performs grinding feed, bringing the lower surface 48a of the grinding wheel 48 into contact with the designated upper surface 64a of the reference plate 64. Thus, the position of the lower surface 48a of the grinding wheel 48, with the holding surface 8a serving as a reference in the height direction, is identified by the grinding apparatus 2.

[0093] However, manual setup not only consumes the operator's working hours, but also carries the risk of damage to the grinding device 2 and grinding wheel 44 due to operational errors if manual setup is performed every time.

[0094] Therefore, in this embodiment, as Figure 6 As shown, in the first setup, the reference plate 64 is used for manual setup (S10 to S30), but in the second and subsequent setups, the reference plate 64 is not used and the laser displacement meter 50 is used for setup (S50).

[0095] This reduces the time required for the operator 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. Specifically, it reduces the possibility of damage to the grinding device 2 or the grinding wheel 44 due to operational errors.

[0096] Figure 6 This is a flowchart for setting up this embodiment. In the reference piece placement process S10, the operator manually places the reference piece 64 into a designated area of ​​the holding surface 8a corresponding to the contact area 11c. For example... Figure 7 As shown, the reference piece 64 has a generally flat lower surface 64b and a generally stepped upper surface 64a.

[0097] 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.

[0098] In this example, the thickest area is used, but which thickness of area to use can be appropriately determined. The thickness D of the reference sheet 64 used is input by the operator to the control unit 70 via an input device such as a touch panel (not shown).

[0099] After the reference plate placement process S10, the grinding unit 32, positioned above the chuck table 8, is lowered. Then, the lower surface 48a of the grinding tool 48, located at a position different from directly above the laser displacement meter 50, is positioned relative to the height P of the grinding tool 48 in the Z-axis direction relative to the holding surface 8a. B The upper surface 64a of the reference piece 64 is in contact (contact process S20).

[0100] Furthermore, in the contact process S20, the holding surface position storage unit 72 stores the relative height position P 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. A .

[0101] After or simultaneously with the contact process S20, the first distance B1 to the lower surface 48a of the grinding wheel 48 is measured using the laser displacement meter 50 (first measurement process S30). Figure 7 This is a partial cross-sectional side view showing the first measurement step S30.

[0102] After the first measurement step S30, the reference piece 64 is removed from the holding surface 8a (removal step S40). In addition, during the period from the reference piece placement step S10 to the removal step S40, the spindle 38 of the grinding unit 32 and the chuck table 8 do not rotate.

[0103] After the removal process S40, for example, grinding of the wafer 11 is performed. Since the lower surface 48a of the grinding tool 48 wears down during the grinding of the wafer 11, the tip length C of the grinding tool 48 becomes shorter (see reference). Figure 9 ).

[0104] If the tool tip length C becomes shorter, even if the grinding wheel 44 is positioned at the height set in the contact process S20, the distance from the lower surface 48a to the holding surface 8a will differ from the thickness D. In such cases, the settings need to be readjusted for high-precision grinding.

[0105] Furthermore, even if the lower surface 48a of the grinding wheel 48 is worn, the first distance Z1 from the laser displacement meter 50 to the lower surface 48a (refer to...) Figure 9 ) and the distance Z3 from the holding surface 8a to the lower surface 48a (refer to Figure 9 The same applies. That is, distance Z3 is a linear function of the coefficient (i.e., slope) of the first distance Z1, which is 1.

[0106] As mentioned above, when the first distance Z1 is the first distance B1, the distance Z3 is the thickness D (refer to...). Figure 7 Furthermore, in this embodiment, D < B1 (i.e., 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.

[0107]

Mathematical Formula 1

[0108] Z3==Z1-(B1-D)

[0109] Figure 8 This 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 wheel 48. If the distance Z3 is calculated, the height position P of the lower surface 48a of the grinding wheel 48, with the holding surface 8a as the reference, is... C The calculation is performed using the following mathematical formula 2.

[0110]

Mathematical Formula 2

[0111] P C =P A +Z3

[0112] The lower surface position calculation unit 76 has a program corresponding to the mathematical formulas 1 and 2 mentioned above, which can calculate the position based on the first distance B1, thickness D, and relative height position P. A And the first distance Z1 is used to calculate the height position P of the lower surface 48a with the holding surface 8a as the reference. C .

[0113] After grinding the wafer 11, the height position P of the lower surface 48a, based on the holding surface 8a, is calculated. C At that time, a laser beam L is irradiated onto the grinding wheel 44, which is arranged at an arbitrary height, and the first distance Z1 from the laser displacement meter 50 to the lower surface 48a of the grinding tool 48 is measured (second measurement step S50).

[0114] Figure 9 This 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, then as described above, the lower surface position calculation unit 76 can calculate the height position P of the lower surface 48a of the grinding wheel 48 during the second measurement step S50 with the holding surface 8a as the reference. C (Calculation of the height position of the lower surface S60)

[0115] In the second measurement step S50, the laser displacement meter 50 can be used for setting without the reference plate 64. As a result, the operator can reduce the time spent placing the reference plate 64 on the holding surface 8a and then retrieving it.

[0116] Furthermore, it can reduce the possibility of operational errors caused by manual settings. That is, it can reduce the possibility of damage to the grinding device 2 or the grinding wheel 44 caused by operational errors due to the reference plate 64.

[0117] Furthermore, since the reference plate 64 is not used in the second measurement step S50, it has the advantage that 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 chuck table 8 and the grinding wheel 44 are rotating.

[0118] In addition, during the rotation of the grinding wheel 44, the strip-shaped laser beam L irradiates the lower surfaces 48a of the multiple grinding tools 48 and the lower surfaces 46a of the grinding wheel base 46 adjacent to each grinding tool 48 in the radial direction of the grinding wheel 44.

[0119] After step S60, if the laser displacement meter 50 is used again without the reference plate 64 for setting (S70: Yes), the process returns to S50. Conversely, if no setting is performed (S70: No), the process ends.

[0120] Additionally, in the second measurement step S50, the center offset calculation unit 80 of the control unit 70 calculates the offset 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 tools 48 (see reference). Figure 10 ).

[0121] Figure 10 This is a diagram showing the offset of the center 48c of the outer peripheral side surface 48b of a plurality of grinding wheels 48 relative to the rotation center 38a of the spindle 38. The offset (i.e., eccentricity) between the rotation center 38a and the center 48c is produced when the grinding wheel 44 is mounted on the wheel holder 42, for example, by about 100 μm.

[0122] exist Figure 10 In the above view of the grinding device 2, the outer peripheral side 48b of the grinding wheel 44 is shown by a solid line when it is in the rearmost position E1, and the outer peripheral side 48b of the grinding wheel 44 is shown by a dashed line when it is in the foremost position E2.

[0123] With the rotation center 38a offset from the center 48c, the position of the outer periphery of the lower surface 48a of the grinding wheel 48, which is located directly above the laser displacement meter 50, changes as the grinding wheel 44 rotates.

[0124] Figure 11 This is a graph showing the time-varying position of the outer periphery of the lower surface 48a of the grinding wheel 48. Figure 11 In the diagram, the horizontal axis represents time, and the vertical axis represents the position of the outer periphery of the lower surface 48a of the grinding wheel 48, which is located directly above the laser displacement meter 50.

[0125] exist Figure 11 In the process, the grinding wheel 44 is located at the forward position E2 at time 0 and time T, and at the rear position E1 at time T / 2. The center offset calculation unit 80 calculates the distance F between the outer periphery position at the forward position E2 and the outer periphery position at the rear position E1 based on the light-receiving position on the CMOS sensor 60.

[0126] The offset between the rotation center 38a and the center 48c corresponds to half of the distance F. Therefore, the center offset calculation unit 80 calculates the offset by calculating F / 2 (offset calculation process). The calculated offset is displayed on a display device such as a touch panel provided on the grinding device 2 (not shown).

[0127] When the offset between the rotation center 38a and the center 48c is not zero, the operator can correct the position of the center 48c on the outer peripheral side 48b. For example, with the grinding unit 32 stopped, the position of the center 48c can be corrected by striking the side of the grinding wheel 44 with a hammer.

[0128] Furthermore, while the grinding wheel 44 is rotating at a predetermined speed, the position of the center 48c of the outer peripheral side surface 48b can be corrected by pressing the dressing component against the outer peripheral side surface 48b. Moreover, the structure and method of the above-described embodiment can be appropriately modified without departing from the purpose of the present invention.

Claims

1. A grinding apparatus for grinding a workpiece, characterized in that, This grinding device has the following features: A chuck table having a holding surface for holding the workpiece and capable of rotating about a specified axis of rotation; The grinding unit is positioned above the chuck table. The grinding unit has a spindle, and a grinding wheel is mounted at the lower end of the spindle. Multiple grinding tools are arranged around the lower surface of the annular grinding wheel base. A moving mechanism that moves the chuck table and the grinding unit relative to each other in a predetermined direction such that the holding surface approaches the grinding wheel; The detection unit has a light-emitting part and a light-receiving part. The light-emitting part includes 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 grinding wheel base adjacent to the at least one grinding wheel in the radial direction of the grinding wheel. The light-receiving part includes a light-receiving element for receiving reflected light from the laser beam. as well as The control unit, which has a processor and a memory, controls the grinding unit, the moving mechanism, and the detection unit. The control unit has: A holding surface position storage section stores the relative height position of the holding surface with respect to the grinding wheel in a predetermined direction when the grinding tool contacts the upper surface of the reference piece disposed on the holding surface; The first distance calculation unit calculates a first distance in the prescribed direction from the detection unit to the lower surface of the at least one grinding wheel; and The lower surface position calculation unit calculates the position of the lower surface of at least one grinding tool with the retaining surface as a reference, based on the height position stored in the retaining surface position storage unit, the first distance calculated by the first distance calculation unit, and the thickness from the upper surface of the reference piece to the lower surface of the reference piece.

2. The grinding apparatus according to claim 1, characterized in that, When the grinding wheel contacts the upper surface of the reference piece disposed on the retaining surface, the relative height position of the retaining surface with respect to the grinding wheel in the specified direction is set as P. A Let D be the thickness from the upper surface to the lower surface of the reference piece, and let B1 be the first distance from the detection part to the lower surface of the at least one grinding wheel. With the reference piece removed from the holding surface, the first distance from the detection section to the lower surface of the at least one grinding wheel is defined as Z1. In the above case, the lower surface position calculation unit uses mathematical formula 1: Z3 = Z1 - (B1 - D) and mathematical formula 2: P C =P A +Z3 is used to calculate the height position P of the lower surface of the at least one grinding wheel with the retaining surface as a reference, in the state where the reference piece has been removed from the retaining surface. C .

3. The grinding apparatus according to claim 1, characterized in that, The control unit also includes a tip length calculation unit, which calculates the tip length of the at least one grinding wheel based on a second distance from the detection unit to the lower surface of the grinding wheel base and a first distance from the detection unit to the lower surface of the at least one grinding wheel.

4. The grinding apparatus according to any one of claims 1 to 3, characterized in that, The control unit also includes a center offset calculation unit, which calculates the offset between the rotation center of the spindle and the center of the outer peripheral side surface of the plurality of grinding tools based on the light-receiving data detected by the detection unit when the grinding wheel is rotated.

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