Grinding apparatus and workpiece grinding method

Abstract

To reduce a difference between a shape of a holding surface after grinding and a shape of one surface of a workpiece after grinding.SOLUTION: A chuck table having a holding surface of a polygonal shape as viewed in plan, a grinding unit, a moving unit, a load detecting unit, and a controller, the controller including a load storage section, a holding surface grinding control section for controlling a load applied to one or both of the grinding unit and the chuck table by controlling a parameter relating to grinding when the holding surface is ground by a grinding wheel, and a workpiece grinding control section for controlling a load to be controlled by the holding surface grinding control section by controlling a parameter relating to grinding when a workpiece held on the holding surface is ground, the controller controls a parameter related to grinding so that a load to be controlled by the holding surface grinding command part and a load to be controlled by the workpiece grinding command part have the same value.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a grinding device equipped with a chuck table having a holding surface that is polygonal in plan view, and a grinding method for grinding a workpiece held by the holding surface. [Background technology]

[0002] Integrated circuit (IC) packages are essential components in electronic devices such as mobile phones and personal computers. As electronic devices have become smaller and thinner in recent years, there has been a demand for thinner IC packages as well.

[0003] To make the IC package thinner, a rectangular substrate is formed by sealing a number of semiconductor device chips arranged in a matrix with molding resin, and then one surface (e.g., the back surface) of this rectangular substrate is thinned by grinding using a grinding device.

[0004] The grinding device includes a chuck table that can rotate around a rotation axis. The center of rotation of the rotation axis is located at a position corresponding to the center of the surface (i.e., the holding surface) on which the rectangular substrate is held. Depending on the shape of the rectangular substrate, which is square or rectangular in plan view, the shape of the holding surface in plan view is also square or rectangular.

[0005] A grinding unit including a spindle is provided above the chuck table. An annular grinding wheel is attached to the lower end of the spindle. The grinding wheel has an annular base, and a plurality of grinding stones are arranged at approximately equal intervals around the periphery of the base on the underside of the base.

[0006] When the grinding wheel rotates due to the rotation of the spindle, the annular grinding surface formed by the trajectories of the grinding stones passes through the center of the holding surface of the chuck table. Grinding of one surface of a rectangular substrate in this grinding device is performed, for example, in the following order: First, the other surface (e.g., the front surface) of the rectangular substrate is suction-held on the holding surface of the chuck table.

[0007] Next, the position of the chuck table is adjusted so that the center of one surface of the rectangular substrate and the trajectories of the grinding wheels are aligned vertically. Then, while rotating both the chuck table and the spindle, the grinding unit is moved downward at a predetermined grinding feed rate.

[0008] The portions of one surface of the rectangular substrate that come into contact with the grinding wheels are ground, but because the chuck table rotates during grinding, the entire surface of the rectangular substrate is ground. However, as the chuck table rotates, the contact area (grinding area) between the rectangular substrate and the grinding wheels repeatedly increases and decreases in the direction along the rotation axis.

[0009] For example, when grinding the portion between the center of one surface of the rectangular substrate and each corner of the rectangular substrate, the grinding area of ​​the rectangular substrate is larger than the grinding area when grinding the portion between the center of one surface of the rectangular substrate and each side of the rectangular substrate.

[0010] Therefore, when grinding one surface of a rectangular substrate, the portions near the corners of the rectangular substrate tend to be relatively thick, and the other portions tend to be relatively thin. In light of this, a method has been proposed in which the holding surface of a chuck table is ground before grinding the workpiece in order to reduce the variation in thickness that occurs when grinding a rectangular substrate (see, for example, Patent Document 1).

[0011] The technique described in Patent Document 1 aims to reduce variations in the thickness of the rectangular substrate after grinding by grinding the holding surface in advance, so that the shape formed on one side of the holding surface due to an increase or decrease in the grinding area when grinding the holding surface is approximately the same as the shape formed on one side of the rectangular substrate due to an increase or decrease in the grinding area when grinding the rectangular substrate.

[0012] However, the holding surface and the rectangular substrate are made of different materials: for example, the holding surface is made of ceramics such as alumina, while the area to be ground of the rectangular substrate is made of epoxy resin mixed with silica filler.

[0013] The holding surface includes a frame region made of a non-porous dense ceramic and a porous region made of a porous ceramic. Due to the use of such materials and structures, it is generally difficult to make the shape of the holding surface after grinding exactly the same as the shape of one surface of the rectangular substrate after grinding. [Prior art documents] [Patent documents]

[0014] [Patent Document 1] Japanese Patent Application Publication No. 2020-55080 Summary of the Invention [Problem to be solved by the invention]

[0015] The present invention has been made in consideration of the above problems, and aims to reduce the difference between the shape of the holding surface after grinding and the shape of one side of the workpiece after grinding when the holding surface is polygonal in a planar view. [Means for solving the problem]

[0016] According to one aspect of the present invention, a grinding device includes a chuck table having a polygonal holding surface in a plan view and rotatable around a predetermined rotation axis by a rotary drive source including a first motor, a spindle arranged above the holding surface, and a spindle motor for rotating the spindle, a grinding unit having a grinding wheel attached to the spindle, a movement unit having a second motor and moving the chuck table and the grinding unit relatively along a predetermined direction, a load detection unit for detecting a load acting on one or both of the grinding unit and the chuck table, and a controller having a processor and memory and receiving information about the load from the load detection unit, the controller being configured to detect a predetermined load value and the load. a holding surface grinding command unit that controls parameters related to the grinding process when the holding surface is ground with the grinding wheel, thereby controlling the load applied to one or both of the grinding unit and the chuck table; and a workpiece grinding command unit that controls parameters related to the grinding process when the workpiece held on the holding surface is ground, thereby controlling the load applied to one or both of the grinding unit and the chuck table, the load being controlled by the holding surface grinding command unit, wherein the controller controls the parameters related to the grinding process so that the load controlled by the holding surface grinding command unit and the load controlled by the workpiece grinding command unit have the same value.

[0017] Preferably, the load detection unit includes at least one of a first load sensor for detecting a first load that is the load on the grinding unit, a second load sensor for detecting a second load that is the load on the chuck table, and a load ammeter for measuring a load current flowing through the spindle motor that is the load on the spindle motor, wherein the load on the grinding unit includes the first load and the load current, and the load on the chuck table includes the second load, and the parameters related to the grinding process include the relative movement speed of the chuck table and the grinding unit along the predetermined direction, the rotation speed of the chuck table, the rotation speed of the spindle, and the flow rate of grinding water supplied per unit time.

[0018] Preferably, the parameter related to the grinding process is the relative movement speed between the chuck table and the grinding unit along the predetermined direction, and when grinding the holding surface with the grinding wheel, the holding surface grinding command unit controls the movement speed so that the load applied to one or both of the grinding unit and the chuck table becomes the predetermined load value, and when grinding the workpiece held on the holding surface, the workpiece grinding command unit controls the movement speed so that the load that is the target of control of the holding surface grinding command, out of the load applied to one or both of the grinding unit and the chuck table, becomes the predetermined load value.

[0019] According to another aspect of the present invention, there is provided a method for grinding a workpiece, which includes grinding a holding surface of a chuck table having a polygonal shape in a plan view, and then grinding a workpiece held on the holding surface, the method including: a holding surface grinding step in which a load applied to one or both of a grinding unit having a spindle and the chuck table rotatable about a predetermined rotation axis is detected by a load detection unit, and the holding surface of the chuck table is ground with a first grinding wheel attached to the spindle while the grinding unit and the chuck table are brought relatively close to each other in a predetermined direction; a holding step in which, after the holding surface grinding step, the workpiece, which has a polygonal shape corresponding to the holding surface, is held on the holding surface; and after the holding step, grinding the grinding unit and the chuck table. and a workpiece grinding step in which the load applied to one or both of the grinding unit and the chuck table is detected by the load detection unit, and the workpiece held on the holding surface is ground with a second grinding wheel attached to the spindle while the grinding unit and the chuck table are moved relatively closer to each other in the predetermined direction, wherein parameters related to the grinding process are controlled so that the load applied to one or both of the grinding unit and the chuck table detected by the load detection unit in the holding surface grinding step and the load applied to one or both of the grinding unit and the chuck table detected by the load detection unit in the workpiece grinding step, which is the load to be controlled in the holding surface grinding step, have the same value.

[0020] Preferably, the load on the grinding unit includes a first load on the grinding unit and a load current that is a load on a spindle motor that rotates the spindle, the load on the chuck table includes a second load on the chuck table, and the parameters related to the grinding process include the relative movement speed of the chuck table and the grinding unit along the specified direction, the rotation speed of the chuck table, the rotation speed of the spindle, and the flow rate of grinding water supplied per unit time.

[0021] Preferably, in the holding surface grinding process, the parameters related to the grinding process are controlled so that the load applied to one or both of the grinding unit and the chuck table is the load detected by the load detection unit when the workpiece is ground in the workpiece grinding process, and is the load known in advance.

[0022] Preferably, in the workpiece grinding process, parameters related to the grinding process are controlled so that the load applied to one or both of the grinding unit and the chuck table becomes the load detected by the load detection unit when the holding surface is ground in the holding surface grinding process.

[0023] Preferably, the method for grinding a workpiece further comprises, before the holding surface grinding step, a load value setting step for setting the predetermined load value to be targeted in the holding surface grinding step and the workpiece grinding step, and parameters related to the grinding process are controlled so that the load to be controlled becomes the predetermined load value in both the holding surface grinding step and the workpiece grinding step.

[0024] Preferably, the first grinding wheel that lastly grinds the holding surface in the holding surface grinding step and the second grinding wheel used throughout the workpiece grinding step are the same grinding wheel. [Effects of the Invention]

[0025] A controller for a grinding apparatus according to one aspect of the present invention includes a holding surface grinding command unit and a workpiece grinding command unit. The holding surface grinding command unit controls parameters related to the grinding process when grinding the holding surface with a grinding wheel, thereby controlling the load applied to one or both of the grinding unit and the chuck table.

[0026] In response to this, the workpiece grinding command unit controls parameters related to the grinding process when grinding a workpiece held on the holding surface, thereby controlling the load applied to one or both of the grinding unit and the chuck table, which is the load that is the subject of control by the holding surface grinding command unit.

[0027] In other words, by having the controller control the parameters related to the grinding process so that the load controlled by the holding surface grinding command unit and the load controlled by the workpiece grinding command unit are the same value, the difference between the shape of the holding surface after grinding and the shape of one side of the workpiece after grinding can be reduced compared to when such control is not performed.

[0028] Similarly, in the grinding method according to the other aspect of the present invention, the difference between the shape of the holding surface after grinding and the shape of one surface of the workpiece after grinding can be reduced compared to when the parameters related to the grinding process are not controlled so that the load is the same, and therefore the variation in thickness of the workpiece after grinding can be reduced. [Brief explanation of the drawings]

[0029] [Figure 1] FIG. 2 is a partial cross-sectional side view of the grinding device. [Figure 2] 2A is a perspective view of the chuck table, FIG. 2B is a cross-sectional view taken along line AA in FIG. 2A, and FIG. 2C is a cross-sectional view taken along line BB in FIG. 2A. [Figure 3] FIG. 2 is a partial cross-sectional side view showing a rotation mechanism and a support mechanism of the chuck table. [Figure 4] FIG. [Figure 5] FIG. [Figure 6] FIG. 10 is a diagram showing a part of the movement trajectories of a plurality of grinding wheels. [Figure 7] FIG. 2 is a partial cross-sectional side view of the grinding unit in the vicinity of the grinding wheel. [Figure 8] FIG. 1 is a flow diagram of a method for grinding a rectangular substrate. [Figure 9] FIG. 10 is a partial cross-sectional side view showing a holding surface grinding step. [Figure 10] FIG. [Figure 11] FIG. 10 is a partial cross-sectional side view showing a workpiece grinding step. [Figure 12]Figure 12(A) is an oblique view of the rectangular substrate after the workpiece grinding process, Figure 12(B) is a side view of the rectangular substrate after the workpiece grinding process, and Figure 12(C) is a plan view of one surface of the rectangular substrate after the workpiece grinding process. [Figure 13] FIG. 10 is a flowchart of a method for grinding a rectangular substrate according to a second modified example. [Figure 14] FIG. 10 is a flow diagram of a grinding method for a rectangular substrate according to a second embodiment. [Figure 15] Figure 15(A) is a plan view of a chuck table having multiple holding surfaces, each of which is strip-shaped, Figure 15(B) is a perspective view of the chuck table shown in Figure 15(A), Figure 15(C) is a plan view of a chuck table having multiple holding surfaces, each of which is square-shaped, and Figure 15(D) is a perspective view of the chuck table shown in Figure 15(C). DETAILED DESCRIPTION OF THE INVENTION

[0030] (First embodiment) An embodiment according to one aspect of the present invention will be described with reference to the accompanying drawings. Fig. 1 is a partially cross-sectional side view of a grinding apparatus 2. In Fig. 1, some of the components are shown as functional blocks. The X-axis, Y-axis, and Z-axis shown in Fig. 1 are orthogonal to one another.

[0031] In this specification, the direction parallel to the X axis is referred to as the X-axis direction, the direction parallel to the Y axis is referred to as the Y-axis direction, and the direction parallel to the Z axis is referred to as the Z-axis direction. The Z axis is parallel to the vertical direction and the up-down direction, and the XY plane corresponds to the horizontal plane perpendicular to the Z axis.

[0032] The grinding device 2 includes a base 4 that supports or houses each of the components. A rectangular parallelepiped recess 4a having a longitudinal portion aligned along the X-axis is formed on the upper surface of the base 4. A ball screw type movement mechanism 6 is provided in the recess 4a.

[0033] The movement mechanism 6 has a pair of guide rails (not shown). The pair of guide rails are arranged substantially parallel to the X-axis and fixed to the base 4. A movement plate 8 is slidably attached to the upper side of the pair of guide rails.

[0034] A nut portion 10 is provided on the lower surface of the moving plate 8. A screw shaft 12 is rotatably coupled to the nut portion 10 via a plurality of balls (not shown). The screw shaft 12 is disposed along the X-axis between a pair of guide rails.

[0035] A drive source 14 such as a servo motor or a stepping motor is connected to one end of the screw shaft 12. When the screw shaft 12 is rotated by the drive source 14, the movable plate 8 moves along the X-axis. A chuck table 16 having a disk-shaped outer shape is provided above the movable plate 8.

[0036] Here, the chuck table 16 will be described with reference to Figures 2(A) to 2(C). Figure 2(A) is a perspective view of the chuck table 16, Figure 2(B) is a cross-sectional view taken along line AA in Figure 2(A), and Figure 2(C) is a cross-sectional view taken along line BB in Figure 2(A).

[0037] 2(A) to 2(C), the shape of the holding surface 16a is exaggerated for ease of explanation. The holding surface 16a shown in FIGS. 2(A) to 2(C) is the shape after the holding surface grinding step S10 and before the holding step S20, which will be described later, i.e., the shape immediately before the rectangular substrate (workpiece) 11 is held.

[0038] The chuck table 16 has a non-porous, dense, disk-shaped first frame 18 made of ceramics such as alumina. The first frame 18 has a large diameter portion with a plurality of screw holes formed on the outer periphery, and a small diameter portion arranged concentrically with the large diameter portion.

[0039] A second frame 20, which is square (i.e., polygonal) in plan view, is provided on the upper surface of the small diameter portion of the first frame 18. Like the first frame 18, the second frame 20 is also made of ceramics such as alumina, and is a non-porous, dense frame.

[0040] The second frame 20 has a square recess 20a in plan view. A square porous plate 22 made of ceramics such as alumina is fixed to the recess 20a via an adhesive or the like. The outer shape of the porous plate 22 is the same as the outer shape of the recess 20a.

[0041] 2B, the plurality of flow paths include a first flow path 20b disposed on the bottom surface of the recess 20a and a second flow path 20c positioned at the center of the bottom surface of the recess 20a and penetrating from the bottom surface of the recess 20a to a bottom surface 20d of the second frame 20.

[0042] A vacuum device (not shown), such as a vacuum pump or an ejector, is connected via a rotary joint (not shown) to the second frame 20. The porous plate 22 is a continuous porous body in which pores are continuously connected, and a vacuum generated by the vacuum device can be transmitted to the upper surface of the porous plate 22 via the first flow path 20b, the second flow path 20c, etc.

[0043] The upper surface of the second frame 20 and the upper surface of the porous plate 22 are substantially flush with each other, forming a holding surface 16a that suction-holds the rectangular substrate 11 (see FIG. 1). In this example, the holding surface 16a is a square (i.e., a polygon) in plan view, and each side of the holding surface 16a is a straight line in plan view.

[0044] However, as shown in the perspective view of Fig. 2(A), corners 16b of each side of the holding surface 16a protrude compared to midpoints 16c of each side. That is, when the second frame 20 and the porous plate 22 (i.e., the holding member) are viewed from the side, one side of the holding surface 16a is not a straight line but is a curved line that is slightly recessed in the center (see Fig. 12(B)).

[0045] 2(B) shows a cross section of the chuck table 16 taken on a plane that passes through the center 16a0 of the holding surface 16a and the corner 16b of the holding surface 16a and is parallel to the upper surface of the first frame 18. As shown in FIG. 2(B), the center 16a0 protrudes upward beyond the corner 16b by a predetermined length Δ (for example, 25 μm).

[0046] However, the amount of protrusion of center 16a0 from corner 16b is sufficiently smaller than the length of one side of holding surface 16a. The length of one side of holding surface 16a in plan view is a predetermined value, for example, between 320 mm and 700 mm. In Figure 2(B), the amount of protrusion of center 16a0 is exaggerated.

[0047] The cross section AA shown in FIG. 2(B) includes a conical region 16a1 with the center 16a0 as the apex, and a concave curved region 16a2 in which the holding surface 16a gradually becomes lower as it moves from the corner 16b toward the center 16a0.

[0048] As described above, the holding surface 16a gradually becomes lower as one moves along one side from the corner 16b to the midpoint 16c of the side (see arrow C in FIG. 2A). As shown in FIG. 2C, the concave curved surface region 16a2 disappears in a cross section passing through the midpoint 16c of the side and the center 16a0.

[0049] The holding surface 16a at the end face of the BB cross section shown in Fig. 2(C) corresponds to two sides of an isosceles triangle. In Fig. 2(C), the corner 16b located further into the page than the end face of the BB cross section is located above the midpoint 16c.

[0050] The square holding surface 16a in plan view has a conical region 16a1 in the center, and concave curved regions 16a2 are provided near each corner 16b so as to fill the gap between the central conical region 16a1 and each of the four corners 16b.

[0051] The rectangular substrate 11 (see FIG. 1) that is suction-held by the holding surface 16a has, in a plan view, substantially the same square shape as the holding surface 16a (a polygonal shape corresponding to the holding surface 16a) and has substantially the same size as the holding surface 16a.

[0052] The rectangular substrate 11 is formed by sealing a plurality of semiconductor device chips together with a semiconductor package substrate having a die pad, a lead frame, etc., with a molding resin (for example, an epoxy resin mixed with a silica filler).

[0053] The rectangular substrate 11 includes one surface (back surface) 11b that is the surface to be ground, and a held surface (front surface) 11a that faces the holding surface 16a during grinding. Here, another configuration of the grinding device 2 will be described with reference to FIG.

[0054] 3 is a partial cross-sectional side view showing the rotation mechanism and support mechanism of the chuck table 16. Some of the components are shown as functional blocks in FIG. 3. The chuck table 16 is rotatably supported by an air bearing 24.

[0055] The air bearing 24 has a rotor 24a (a predetermined rotation axis) connected to the lower surface of the chuck table 16. The rotor 24a has a large diameter portion 24a1 provided at the top in the longitudinal direction, and a small diameter portion 24a2 located below the large diameter portion 24a1.

[0056] A ring-shaped stator 24b is disposed below the large-diameter portion 24a1 and around the small-diameter portion 24a2. The rotor 24a and the stator 24b are not in contact with each other, and a small gap (not shown) is formed between them. Compressed air is supplied to this gap from an air supply source (not shown).

[0057] A driven pulley (not shown) is fixed to the lower end of the rotor 24a. A rotary drive source 26 having a motor (first motor) 26a such as a servo motor is provided near the rotor 24a. The rotary drive source 26 is supported by the moving plate 8 described above.

[0058] A drive pulley (not shown) is fixed to the output shaft of the motor 26a, and an endless belt (not shown) is looped between the drive pulley and the driven pulley. When the motor 26a is operated, rotational power is transmitted to the rotor 24a.

[0059] The rotor 24a rotates by power transmitted from the rotary drive source 26 while maintaining a non-contact state with the stator 24b. Due to the rotation of the rotor 24a, the chuck table 16 rotates (is rotatable) around the rotor 24a.

[0060] The stator 24b of the air bearing 24 is supported by an annular table base 28. A through hole 28a is formed in the radial center of the table base 28, into which the rotor 24a is inserted.

[0061] A plurality of disk-shaped lower load sensors (i.e., second load sensors) 30 are provided around the through-hole 28a on the upper surface of the table base 28. The lower load sensors 30 detect a downward load (second load) that is a load applied downward to the chuck table 16 (see FIG. 1).

[0062] Each lower load sensor 30 is supported by the table base 28. Fig. 4 is a plan view of the table base 28. In this example, three lower load sensors 30 are arranged at approximately equal intervals along the circumferential direction of the through-hole 28a.

[0063] However, the number of lower load sensors 30 is not limited to three. At least one lower load sensor 30 may be provided on the table base 28. The lower load sensor 30 is, for example, a diaphragm-type load cell.

[0064] However, the lower load sensor 30 may be a column-type load cell. The load cell includes a sensor that converts the load into an electrical signal. For example, the load cell includes a piezoelectric sensor having a piezoelectric element, but may instead include a strain gauge sensor, a capacitance sensor, or the like.

[0065] The upper surface of the lower load sensor 30 is in contact with the lower surface of the stator 24b (see FIG. 3). The force pressing the chuck table 16 downward is transmitted to the lower load sensor 30 via the stator 24b.

[0066] The downward load value 30a (i.e., information 84a relating to the load) (see FIG. 1) applied to each lower load sensor 30 is notified to a controller 86, which will be described later. The controller 86 can grasp the downward load in real time and can calculate the average value or total value of the downward loads applied to the plurality of lower load sensors 30.

[0067] In FIG. 1, for ease of viewing, one lower load sensor 30 and the controller 86 are connected by a line, but in reality, all of the lower load sensors 30 and the controller 86 are connected.

[0068] Returning to Fig. 3, the table base 28 is supported by an inclination adjustment mechanism 32. The inclination adjustment mechanism 32 adjusts the inclination of the table base 28 with respect to the XY plane. The inclination adjustment mechanism 32 has a fixed support mechanism 32a, a first movable support mechanism 32b, and a second movable support mechanism 32c.

[0069] The fixed support mechanism 32a, the first movable support mechanism 32b, and the second movable support mechanism 32c are spaced apart at approximately equal intervals along the circumferential direction of the through-hole 28a, and each top portion is fixed to the underside of the table base 28.

[0070] The fixed support mechanism 32a, the first movable support mechanism 32b, and the second movable support mechanism 32c are provided at positions in the Z-axis direction that do not overlap with the lower load sensor 30. For example, the fixed support mechanism 32a, the first movable support mechanism 32b, the second movable support mechanism 32c, and the three lower load sensors 30 are located at the vertices of a regular hexagon (see FIG. 4).

[0071] The fixed support mechanism 32a has a fixed shaft 34a of a predetermined length. In contrast, the first movable support mechanism 32b has a movable shaft 34b with a male thread formed at its tip, and the second movable support mechanism 32c has a movable shaft 34c with a male thread formed at its tip.

[0072] The upper portions of the movable shafts 34b, 34c are rotatably connected to threaded holes in an upper support fixed to the underside of the table base 28. Drive sources 36b, 36c such as servo motors or pulse motors are connected to the lower ends of the movable shafts 34b, 34c.

[0073] The movable shafts 34b and 34c can be rotated by drive sources 36b and 36c. The movable shafts 34b and 34c are supported by a moving plate 8. The inclination of the table base 28 with respect to the XY plane can be adjusted by adjusting the amount that the movable shafts 34b and 34c are screwed into the upper support body.

[0074] The rotor 24a tilts in accordance with the tilt of the table base 28. The rotation center 24a3 of the rotor 24a is tilted by a small angle α with respect to the Z axis in the YZ plane, and is also tilted by a small angle with respect to the Z axis in the XZ plane.

[0075] 1, another configuration of the grinding device 2 will now be described. On both sides of the chuck table 16 in the X-axis direction, bellows-shaped cover members 40 that are extendable and contractible along the X-axis direction are provided. The cover members 40 prevent contamination of the moving mechanism 6 by grinding water 70 (see FIG. 7), grinding chips generated during grinding, etc.

[0076] A rectangular parallelepiped support structure 4b is provided in an upwardly protruding manner at the rear (one side in the X-axis direction) of the grinding device 2. A ball screw type grinding feed mechanism (moving unit) 42 is provided on the front side (the other side in the X-axis direction) of the support structure 4b.

[0077] The grinding feed mechanism 42 moves a grinding unit 54 (described later) along the Z-axis direction (predetermined direction), thereby moving the chuck table 16 and the grinding unit 54 relatively along the Z-axis direction.

[0078] The grinding feed mechanism 42 includes a pair of guide rails 44 arranged along the Z axis. A rectangular moving plate 46 is fixed to the pair of guide rails 44 so as to be slidable in the Z axis direction. A nut portion 48 is provided on the rear side surface of the moving plate 46.

[0079] A screw shaft 50 is rotatably coupled to the nut portion 48 via a plurality of balls (not shown). The screw shaft 50 is disposed along the Z axis between the pair of guide rails 44. A motor (second motor) 52 such as a servo motor or a stepping motor is connected to the upper end of the screw shaft 50.

[0080] When the screw shaft 50 is rotated by the motor 52, the moving plate 46 moves along the Z axis. A cylindrical holding member 56 for holding the grinding unit 54 is fixed to the front side surface of the moving plate 46. The grinding unit 54 has a cylindrical spindle housing 58.

[0081] The spindle housing 58 is disposed in a hollow portion of the holding member 56 and is supported by the holding member 56. More specifically, the spindle housing 58 is supported by the holding member 56 via a plurality of upper load sensors (first load sensors) 60.

[0082] The lower surface of each upper load sensor 60 is fixed to the bottom plate of the holding member 56, and the upper surface of each upper load sensor 60 is fixed to the bottom surface of the spindle housing 58. The upper load sensors 60 are, for example, diaphragm-type or column-type load cells.

[0083] A downward force (i.e., compressive force) along the Z-axis direction is constantly acting on each upper load sensor 60 due to a force caused by the weight of the grinding unit 54. However, during grinding, the grinding unit 54 moved by the grinding feed mechanism 42 presses downward against the holding surface 16a or the rectangular substrate 11, and as a reaction to this, the grinding wheel 68 receives an upward force.

[0084] At this time, the spindle housing 58 also receives an upward force, and an upward force (i.e., a tensile force) acts on each upper load sensor 60. This tensile force reduces the compressive force acting on the upper load sensor 60. In other words, an upward load (first load) acting upward on the grinding unit 54 is detected in accordance with an increase or decrease in the compressive force acting on the upper load sensor 60.

[0085] The upward load value 60a (i.e., information 84a related to the load) applied to each upper load sensor 60 is notified to the controller 86. The controller 86 can grasp the upward load in real time and can calculate the average value or total value of the upward loads applied to the multiple upper load sensors 60.

[0086] In FIG. 1, for ease of viewing, one upper load sensor 60 and the controller 86 are connected by a line, but in reality, all of the upper load sensors 60 and the controller 86 are connected.

[0087] 5 is a plan view of the grinding unit 54 showing multiple upper load sensors 60. In this embodiment, three upper load sensors 60 are arranged at approximately equal intervals along the circumferential direction of the spindle housing 58. However, the number of upper load sensors 60 is not limited to three. At least one upper load sensor 60 may be provided on the table base 28.

[0088] Returning to Figure 1, a portion of a cylindrical spindle 62 is rotatably housed in the spindle housing 58. The spindle 62 and the spindle housing 58 are disposed above the holding surface 16a of the chuck table 16. The longitudinal direction of the spindle 62 is aligned with the Z axis.

[0089] A spindle motor 64, such as a DC (Direct Current) servo motor, is provided around the spindle 62 within the spindle housing 58. When there is no load to stop the rotation (i.e., when there is no load), the spindle motor 64 rotates the spindle 62 at a number of rotations (rotational speed) according to the power supplied.

[0090] The lower end of the spindle 62 protrudes downward below the bottom surface of the holding member 56, and a disk-shaped wheel mount 66 is fixed to the lower end of the spindle 62. An annular grinding wheel 68 is fixed to the bottom surface of the wheel mount 66 using a bolt (not shown). In other words, the grinding wheel 68 is attached to the lower end of the spindle 62.

[0091] The grinding wheel 68 includes an annular wheel base 68a having an outer diameter approximately the same as that of the wheel mount 66. The wheel base 68a is made of a metal such as an aluminum alloy. A plurality of grinding stones 68b are fixed to the underside of the wheel base 68a at approximately equal intervals along the circumferential direction of the wheel base 68a.

[0092] Each grinding wheel 68b has abrasive grains made of diamond, cBN (cubic boron nitride), etc., and a bonding material (bond material) made of resin, metal, vitrified (i.e., ceramics), etc. that secures the abrasive grains.

[0093] When the spindle 62 is rotated, the grinding wheel 68 rotates around the spindle 62. When the grinding wheel 68 rotates, the locus of the bottom surfaces of the multiple grinding stones 68b forms an annular grinding surface 68c (see FIG. 6).

[0094] 6 is a diagram showing part of the movement locus of the plurality of grinding stones 68b when the holding surface 16a is viewed from above. The grinding surface 68c is arranged so as to pass through the center 16a0 of the holding surface 16a when viewed from above.

[0095] The spindle 62, the wheel mount 66 and the wheel base 68a are provided with flow paths 62a, 66a and 68a1 for supplying grinding water 70 such as pure water to the grinding wheel 68b (see FIG. 7).

[0096] 7 is a partial cross-sectional side view of the grinding unit 54 near the grinding wheel 68. Grinding water 70 is used to remove heat and grinding dust generated in the processing area. A grinding water supply source 72 is connected to the flow path 62a of the spindle 62.

[0097] The grinding water supply source 72 includes a tank in which the grinding water 70 is stored, a pump for supplying the grinding water 70 from the tank, and the like (none of which are shown). The grinding water supply source 72 is usually a device provided separately from the grinding device 2.

[0098] When grinding the holding surface 16a and the rectangular substrate 11, the chuck table 16 and the spindle 62 are rotated, and grinding water 70 is supplied to the grinding wheel 68b from the grinding water supply source 72 at a predetermined flow rate while the grinding unit 54 is moved downward at a predetermined speed by the grinding feed mechanism 42.

[0099] During grinding, a power supply unit 80 (see FIG. 1) supplies power to the spindle motor 64 to rotate the spindle 62. The power supply unit 80 includes a DC power supply (not shown) and a predetermined circuit (not shown) for changing the drive voltage supplied from the DC power supply to the spindle motor 64. The predetermined circuit is a circuit that changes the drive voltage using, for example, a PWM (Pulse Width Modulation) method or a linear method.

[0100] During grinding, the load current flowing through the spindle motor 64 (i.e., the load on the grinding unit 54) changes according to the load torque (i.e., the grinding load) of the spindle 62. As shown in Fig. 1, a load ammeter 82 is connected in series to the spindle motor 64 and the power supply unit 80, and the load current flowing through the spindle motor 64 is measured by the load ammeter 82.

[0101] The load current value 82a (load-related information 84a) measured by the load ammeter 82 is notified to the controller 86 of the grinding device 2. The controller 86 can grasp the load current value 82a in real time and can calculate the average value of the load current.

[0102] For example, if the load current value 82a becomes larger than a predetermined reference value, it means that the grinding load is larger than the predetermined reference value, i.e., the rotation speed of the spindle 62 is lower than the predetermined reference value.

[0103] The plurality of lower load sensors 30, the plurality of upper load sensors 60, and the load ammeter 82 constitute a load detection unit 84. That is, the load detection unit 84 of this embodiment can detect the load applied to both the grinding unit 54 and the chuck table 16.

[0104] The load detection unit 84 of this embodiment has three lower load sensors 30, three upper load sensors 60, and a load ammeter 82, but the load detection unit 84 may also include at least one of the lower load sensor 30, the upper load sensor 60, and the load ammeter 82.

[0105] The load detection unit 84 may detect only the load (load) applied to either the grinding unit 54 or the chuck table 16, or may detect only the load current (load) of the grinding unit 54. It may also detect a combination of the load and the load current.

[0106] The load on the grinding unit 54 detected by the load detection unit 84 includes an upward load and a load current, and the load on the chuck table 16 detected by the load detection unit 84 includes a downward load.

[0107] The controller 86 is configured by a computer having a processor 86a, such as a CPU (Central Processing Unit), and a memory 86b. The memory 86b includes a main storage device such as a DRAM (Dynamic Random Access Memory) and an auxiliary storage device such as a flash memory.

[0108] The auxiliary storage device stores software including a predetermined program. The functions of the controller 86 are realized by operating the processor 86a and other components in accordance with this software.

[0109] The controller 86 receives information 84a regarding the load (i.e., at least one of the downward load value 30a, the upward load value 60a, and the load current value 82a) from the load detection unit 84, and controls the grinding device 2 in accordance with the received information 84a regarding the load.

[0110] Here, the function of the controller 86 during grinding will be described with reference to Fig. 9. A part of the storage area of ​​the memory 86b functions as a load storage unit 88. The load storage unit 88 stores one or both of a predetermined load value and information 84a related to the load.

[0111] In this specification, the term "predetermined load value" refers to a predetermined value for at least one of (i) the load (i.e., upward load) applied to the grinding unit 54 measured by the upper load sensor 60, (ii) the load (i.e., downward load) applied to the chuck table 16 measured by the lower load sensor 30, and (iii) the load (i.e., load current) measured by the load ammeter 82.

[0112] The holding surface grinding command unit 90 is realized, for example, by having the processor 86 a execute a program stored in the memory 86 b. When the holding surface 16 a is ground with the grinding wheel 68, the holding surface grinding command unit 90 controls parameters related to the grinding process, thereby controlling the load applied to one or both of the grinding unit 54 and the chuck table 16.

[0113] The parameters related to the grinding process include (a) the relative movement speed (μm / s) of the chuck table 16 and the grinding unit 54 along the Z-axis direction (predetermined direction), (b) the rotation speed (rpm) of the chuck table 16, (c) the rotation speed (rpm) of the spindle 62, and (d) the flow rate (L / min) of the grinding water 70 supplied per unit time.

[0114] The downward load, upward load, and load current (a) increase as the relative movement speed increases, (b) decrease as the rotation speed of the chuck table 16 increases, (c) decrease as the rotation speed of the spindle 62 increases, and (d) decrease as the flow rate of the grinding water 70 increases.

[0115] Conversely, the downward load, upward load, and load current (a) decrease when the relative movement speed is reduced, (b) increase when the rotation speed of the chuck table 16 is reduced, (c) increase when the rotation speed of the spindle 62 is reduced, and (d) increase when the flow rate of the grinding water 70 is reduced.

[0116] In this way, the holding surface grinding command unit 90 controls the load applied to one or both of the grinding unit 54 and the chuck table 16 by controlling at least one of the parameters (a) to (d) related to the grinding process when grinding the holding surface 16a.

[0117] The workpiece grinding command unit 92 is also realized by, for example, executing a program stored in the memory 86b by the processor 86a. The workpiece grinding command unit 92 controls the load applied to one or both of the grinding unit 54 and the chuck table 16 by controlling parameters related to the grinding process when grinding the rectangular substrate 11 held by suction on the holding surface 16a.

[0118] However, in this embodiment, the load controlled by the workpiece grinding command unit 92 is the same as the load controlled by the holding surface grinding command unit 90. Furthermore, similar to when grinding the holding surface 16a, the parameters related to the grinding process when grinding the workpiece include the above-mentioned (a) to (d).

[0119] When grinding the rectangular substrate 11, the workpiece grinding command unit 92 controls the load applied to one or both of the grinding unit 54 and the chuck table 16 by controlling at least one of the parameters (a) to (d) related to the grinding process.

[0120] In particular, the controller 86 controls parameters related to the grinding process so that the load controlled by the holding surface grinding command unit 90 and the load controlled by the workpiece grinding command unit 92 have the same value.

[0121] For example, when the load controlled by the holding surface grinding command unit 90 is a downward load, the controller 86 also sets the load controlled by the workpiece grinding command unit 92 to a downward load. The controller 86 controls at least one of the above-mentioned parameters (a) to (d) so that the downward load when grinding the rectangular substrate 11 has the same value as the downward load when grinding the holding surface 16a.

[0122] Similarly, when the load controlled by the holding surface grinding command unit 90 is an upward load, the controller 86 also sets the load controlled by the workpiece grinding command unit 92 to an upward load. The controller 86 controls at least one of the above-mentioned parameters (a) to (d) so that the upward load when grinding the rectangular substrate 11 has the same value as the upward load when grinding the holding surface 16a.

[0123] Similarly, when the load controlled by the holding surface grinding command unit 90 is a load current, the controller 86 also sets the load controlled by the workpiece grinding command unit 92 to a load current. The controller 86 controls at least one of the above parameters (a) to (d) so that the load current when grinding the rectangular substrate 11 has the same value as the load current when grinding the holding surface 16a.

[0124] More specifically, the controller 86 performs, for example, proportional-integral-derivative (PID) control so that the load when grinding the holding surface 16a and the load when grinding the rectangular substrate 11 have the same value.

[0125] When performing PID control, for example, the controller 86 controls at least one of the above parameters (a) to (d) so that the current load value when grinding the rectangular substrate 11 (i.e., the output value of the PID control) becomes the load value when grinding the holding surface 16a (i.e., the target value of the PID control).

[0126] Furthermore, for example, the controller 86 controls at least one of the above-mentioned parameters (a) to (d) so that the current load value (i.e., the output value of the PID control) when grinding the holding surface 16a or the rectangular substrate 11 becomes a predetermined load value (i.e., the target value of the PID control).

[0127] To give a specific example, when grinding the holding surface 16a with the grinding wheel 68, the holding surface grinding command unit 90 controls (a) the moving speed so that the load applied to one or both of the grinding unit 54 and the chuck table 16 becomes a predetermined load value, and when grinding the rectangular substrate 11 held by the holding surface 16a after grinding the holding surface 16a, the workpiece grinding command unit 92 controls (a) the moving speed so that the load that is the object of control when grinding the holding surface 16a with the grinding wheel 68 becomes a predetermined load value.

[0128] The controller 86 can instantly issue instructions to the motor 52 using electrical signals, and (a) the movement speed also responds to the instructions instantly, allowing for more precise control than (b) the rotation speed of the chuck table 16, (c) the rotation speed of the spindle 62, and (d) the flow rate of the grinding water 70.

[0129] In this embodiment, when grinding the rectangular substrate 11, the controller 86 performs such control, so that the difference between the shape of the holding surface 16a after grinding and the shape of one surface 11b of the rectangular substrate 11 after grinding can be reduced compared to when such control is not performed.

[0130] Of course, it is not always possible to make the shape of the holding surface 16a after grinding exactly the same as the shape of one surface 11b of the rectangular substrate 11 after grinding, but the difference between the two shapes can be reliably reduced compared to when such control is not performed. Therefore, the thickness variation (e.g., TTV (Total Thickness Variation)) of the rectangular substrate 11 after grinding can be reduced.

[0131] Next, with reference to Fig. 8 to Fig. 12(C), a method for grinding the rectangular substrate 11 held by the holding surface 16a after grinding the holding surface 16a will be described. Fig. 8 is a flow diagram of the method for grinding the rectangular substrate 11. In this embodiment, the above-mentioned grinding device 2 is used to perform the holding surface grinding step S10, the holding step S20, and the workpiece grinding step S30 in this order.

[0132] 9 is a partial cross-sectional side view showing the holding surface grinding step S 10. In the holding surface grinding step S 10, the holding surface 16a is formed into the shape shown in FIGS.

[0133] In the holding surface grinding process S10, the load applied to one or both of the grinding unit 54 and the chuck table 16 is detected by the load detection unit 84, and the holding surface 16a is ground with a grinding wheel (first grinding wheel) 68 while the grinding unit 54 and the chuck table 16 are brought relatively closer together along the Z-axis direction.

[0134] In the holding surface grinding process S10 of this embodiment, under the premise that the average value of the downward load applied to the chuck table 16 in the subsequent workpiece grinding process S30 has been empirically determined to be 50 N, the above-mentioned (a) moving speed, which is a parameter related to the grinding process, is controlled so that the load applied to the chuck table 16 becomes 50 N (i.e., a predetermined load value).

[0135] However, the load to be controlled in the holding surface grinding step S10 may be a load acting only on the grinding unit 54, which is determined in advance in the workpiece grinding step S30, or a load acting on both the grinding unit 54 and the chuck table 16. In this case as well, the parameters related to the grinding process are controlled so that the load to be controlled in the holding surface grinding step S10 becomes the load determined in advance in the workpiece grinding step S30.

[0136] In addition, not only (a) the moving speed, but also at least one of (a) the moving speed, (b) the rotation speed of the chuck table 16, (c) the rotation speed of the spindle 62, and (d) the flow rate of the grinding water 70 may be controlled.

[0137] After the holding surface grinding step S10, the rectangular substrate 11 is suction-held by the holding surface 16a so that one surface 11b is exposed upward and the other surface 11a faces the holding surface 16a (holding step S20). Fig. 10 is a partial cross-sectional side view showing the holding step S20.

[0138] After the holding step S20, the load applied to one or both of the grinding unit 54 and the chuck table 16 is detected by the load detection unit 84, and while the grinding unit 54 and the chuck table 16 are brought relatively closer together along the Z-axis direction, one surface 11b of the rectangular substrate 11 held by the holding surface 16a is ground with a grinding wheel 68 (second grinding wheel) (workpiece grinding step S30).

[0139] The controller 86 controls the parameters related to the grinding process so that the load applied to one or both of the grinding unit 54 and the chuck table 16 detected by the load detection unit 84 in the holding surface grinding process S10 and the load applied to one or both of the grinding unit 54 and the chuck table 16 detected by the load detection unit 84 in the workpiece grinding process S30, which is the load to be controlled in the holding surface grinding process S10, are the same value.

[0140] In this embodiment, the controller 86 (a) controls the movement speed so that the average value of the load applied to the chuck table 16 in the holding surface grinding step S10 and the average value of the load applied to the chuck table 16 in the workpiece grinding step S30 are both 50 N (predetermined load value). Figure 11 is a partial cross-sectional side view showing the workpiece grinding step S30.

[0141] In the workpiece grinding step S30 of this embodiment, the same grinding wheel (i.e., grinding wheel 68) as the grinding wheel 68 that lastly ground the holding surface 16a in the holding surface grinding step S10 is used throughout the workpiece grinding step S30. The processing conditions in the holding surface grinding step S10 and the workpiece grinding step S30 are adjusted appropriately within the following ranges, for example.

[0142] (a) Traveling speed: 1.0μm / s or more and 10μm / s or less (b) Chuck table rotation speed: 100 rpm or more and 500 rpm or less (c) Spindle speed: 1000 rpm or more and 7000 rpm or less (d) Grinding water flow rate: 1.0 L / min or more and 10 L / min or less

[0143] 12(A) is a perspective view of rectangular substrate 11 after workpiece grinding step S30. In workpiece grinding step S30, one surface 11b of rectangular substrate 11 is ground to follow the shape of holding surface 16a formed in holding surface grinding step S10, as shown in FIG.

[0144] As a result, the difference between the shape of holding surface 16a after grinding and the shape of one surface 11b of rectangular substrate 11 after grinding can be reduced compared to when parameters related to grinding are not controlled so that the load is the same in holding surface grinding step S10 and workpiece grinding step S30. Therefore, the variation in thickness of rectangular substrate 11 after grinding can be reduced.

[0145] Fig. 12(B) is a side view of rectangular substrate 11 after workpiece grinding step S30. Fig. 12(C) is a plan view of one surface 11b of rectangular substrate 11 after workpiece grinding step S30. Fig. 12(C) also shows radial saw marks (i.e., grinding marks) 11c.

[0146] In Figure 12(C), the brighter the color, the closer the holding surface 16a is to the bottom surface 20d of the second frame body 20 in a straight line perpendicular to the bottom surface 20d (i.e., the thinner the thickness), and the darker the color, the farther the holding surface 16a is from the bottom surface 20d (i.e., the thicker the thickness).

[0147] (First Modification) Next, a first modification of the first embodiment will be described. In the first modification, first, the holding surface grinding step S10 is performed, and the load applied to the chuck table 16 in the holding surface grinding step S10 is detected. For example, suppose that the average value of the downward load applied to the chuck table 16 is 30 N.

[0148] In this case, in the subsequent workpiece grinding step S30, the moving speed (a), which is one of the parameters related to the grinding process, is controlled so that the average value of the downward load applied to the chuck table 16 becomes 30N.

[0149] However, in the holding surface grinding process S10, the load applied only to the grinding unit 54 or the load applied to both the grinding unit 54 and the chuck table 16 may be detected, and the parameters related to the grinding process may be controlled so that the load controlled in the workpiece grinding process S30 is the same as the load controlled in the holding surface grinding process S10 (i.e., the same type and value).

[0150] Of course, it is not limited to controlling only (a) the moving speed, but at least one of (a) the moving speed, (b) the rotation speed of the chuck table 16, (c) the rotation speed of the spindle 62, and (d) the flow rate of the grinding water 70 may be controlled.

[0151] In the first variant, compared to the first embodiment, there is a possibility that the UPH (Unit Per Hour) and the grinding quality of the rectangular substrate 11 may decrease, but compared to the case where the parameters related to the grinding process are not controlled so that the load is the same value in the holding surface grinding process S10 and the workpiece grinding process S30, the thickness variation of the rectangular substrate 11 after grinding can be reduced.

[0152] (Second Modification) Next, a second modification of the first embodiment will be described. Fig. 13 is a flow diagram of a grinding method for a rectangular substrate 11 according to the second modification. In the second modification, before the holding surface grinding step S10, a predetermined load value to be targeted in the holding surface grinding step S10 and the workpiece grinding step S30 is set (load value setting step S5).

[0153] In the load value setting step S5, the operator inputs a predetermined load value via a display input device such as a touch panel (not shown) provided on the grinding device 2.

[0154] In both the holding surface grinding process S10 and the workpiece grinding process S30, the controller 86 controls the parameters related to the grinding process so that the load to be controlled (for example, the average value of the downward load applied to the chuck table 16) becomes a predetermined load value (for example, 40 N).

[0155] Of course, in the holding surface grinding process S10 and the workpiece grinding process S30, the controller 86 may detect the load applied only to the grinding unit 54 or the load applied to both the grinding unit 54 and the chuck table 16, and control the parameters related to the grinding process so that the loads controlled in both processes are the same value.

[0156] In addition, not only (a) the moving speed, but also at least one of (a) the moving speed, (b) the rotation speed of the chuck table 16, (c) the rotation speed of the spindle 62, and (d) the flow rate of the grinding water 70 may be controlled.

[0157] Incidentally, making the load applied to the load detection unit 84 in the holding surface grinding process S10 (i.e., the load controlled by the holding surface grinding command unit 90) and the load applied to the load detection unit 84 in the workpiece grinding process S30 (i.e., the load controlled by the workpiece grinding command unit 92) the same value is not limited to making the average values ​​over the entire period of both processes the same.

[0158] In the support surface grinding step S10 and the workpiece grinding step S30, the shape of the grinding surface is significantly affected by the grinding feed rate of the last few tens of microns of each step. Furthermore, in the workpiece grinding step S30, in order to improve throughput, grinding may be performed at a relatively high grinding feed rate, followed by grinding feed rate of the last few tens of microns at a relatively low grinding feed rate. The grinding feed rate is the relative movement speed (a) described above, and the load on the load detection unit 84 may vary depending on the grinding feed rate.

[0159] Therefore, the controller 86 may control parameters related to the grinding process so that the average value of the load applied to the load detection unit 84 when performing the final grinding feed of several tens of μm in the hold surface grinding process S10 and the average value of the load applied to the load detection unit 84 when performing the final grinding feed of several tens of μm at a relatively low grinding feed rate in the workpiece grinding process S30 are the same. Of course, the same load is subject to monitoring and control in both the hold surface grinding process S10 and the workpiece grinding process S30.

[0160] In addition, the grinding feed rate may be kept constant throughout the entire period in the hold surface grinding step S10. In this case, the controller 86 may control parameters related to the grinding process so that the average value of the load acting on the load detection unit 84 throughout the entire period of the hold surface grinding step S10 is the same as the average value of the load acting on the load detection unit 84 when the last few tens of μm are ground at a relatively low grinding feed rate in the workpiece grinding step S30.

[0161] Second Embodiment Next, a second embodiment will be described with reference to Fig. 14. Fig. 14 is a flow diagram of a grinding method for a rectangular substrate 11 according to the second embodiment. In the second embodiment, first, the holding surface grinding step S12 is performed using a grinding wheel (not shown) dedicated to the holding surface.

[0162] In the holding surface grinding step S12, the holding surface 16a is ground with a dedicated holding surface grinding wheel to form the upper surfaces of the second frame 20 and the porous plate 22 into a substantially conical shape (at this time, the concave curved surface region 16a2 is not formed).

[0163] Thereafter, the dedicated holding surface grinding wheel is replaced with a workpiece grinding wheel (corresponding to the grinding wheel 68 described above) (wheel replacing step S14). After the wheel replacing step S14, the holding surface 16a is ground with the workpiece grinding wheel to form the holding surface 16a including the conical region 16a1 and the concave curved surface region 16a2 (later holding surface grinding step S16).

[0164] After the holding surface 16a is completed in this way, the holding step S20 is performed, and then the workpiece grinding wheel is subsequently used to grind one surface 11b of the rectangular substrate 11 (workpiece grinding step S30).

[0165] The grinding wheel for the holding surface has multiple grinding stones, each containing abrasive grains with a relatively large average grain size. The grain size of the abrasive grains in the grinding wheel for the holding surface is, for example, #320, and the bonding material is, for example, a resin bond.

[0166] Grain size refers to the size of the abrasive grains. Grain size is determined in accordance with JIS R 6001-2:2017 (Grain size of abrasives for grinding wheels - Part 2: Fine powder) as specified in the Japanese Industrial Standards (JIS), or in accordance with the standard.

[0167] The workpiece grinding wheel has multiple grinding stones, each containing abrasive grains with a relatively small average grain size. The average grain size of the abrasive grains in the workpiece grinding wheel is smaller than the average grain size of the abrasive grains in the grinding wheel for holding surfaces. The grain size of the abrasive grains in the workpiece grinding wheel is, for example, #3000, and the bonding material is, for example, a vitrified bond.

[0168] In the second embodiment, the holding surface 16a can be formed more efficiently than when a substantially flat holding surface 16a that does not have the conical region 16a1 and the concave curved region 16a2 is formed into a holding surface 16a that has the conical region 16a1 and the concave curved region 16a2 using only a grinding wheel for workpieces.

[0169] It should be noted that grinding the holding surface 16a using only the above-described dedicated grinding wheel for holding surfaces does not result in the formation of the holding surface 16a having the concave curved surface region 16a2. When using a dedicated grinding wheel for holding surfaces, which has a relatively high grinding power, it is necessary to grind the holding surface 16a with a grinding wheel for workpieces, which has a relatively low grinding power.

[0170] (Modifications of the chuck table 16) Next, with reference to Figures 15(A) to 15(D), we will explain modifications of the chuck table 16. Figure 15(A) is a plan view of a chuck table 96 having a plurality of holding surfaces 96a, each of which is shaped like a strip.

[0171] 15(B) is a perspective view of the chuck table 96 shown in Fig. 15(A). In the chuck table 96 shown in Fig. 15(A) and Fig. 15(B), three sets of second frames 20 and porous plates 22, each having a rectangular shape, are arranged in parallel on the upper surface of the first frame 18.

[0172] However, the shapes of the multiple holding surfaces 96a formed through the holding surface grinding step S10 are different from each other. As can be inferred from the shape of the holding surface 16a in Figures 2(A) to 2(C), a conical region 16a1 is formed near the rotation center 24a3 of the holding surface 96a located in the center in a plan view.

[0173] In addition, in each of the two holding surfaces 96a located at both ends in a planar view, a concave curved surface area 16a2 is formed near a corner 96b that is relatively far from the rotation center 24a3, and this corner 96b protrudes compared to the midpoint 96c of the long side farther from the rotation center 24a3.

[0174] In the holding surface grinding process S10, as the chuck table 106 rotates around the rotation center 24a3, the area where the contact area (grinding area) between the holding surface 96a and the grinding surface 68c (see Figure 6) is large becomes relatively thick, and the area where the contact area (grinding area) between the holding surface 96a and the grinding surface 68c is small becomes relatively thin.

[0175] FIG. 15(C) is a plan view of the chuck table 106 having a plurality of holding surfaces 106a, each of which has a square shape, and FIG. 15(D) is a perspective view of the chuck table 106 shown in FIG. 15(C).

[0176] 15(C) and 15(D), three sets of second frames 20 and porous plates 22, each having a square shape, are arranged to surround the rotation center 24a3 on the first frame 18. However, the shapes of the holding surfaces 106a formed through the holding surface grinding step S10 are different for each set.

[0177] Although the specific shape of each holding surface 106a will not be described here, as the chuck table 106 rotates around the rotation center 24a3, the area where the contact area (grinding area) between the holding surface 106a and the grinding surface 68c (see Figure 6) is large becomes relatively thick, and the area where the contact area (grinding area) between the holding surface 106a and the grinding surface 68c is small becomes relatively thin.

[0178] When the chuck table 96 shown in Figures 15(A) and 15(B) or the chuck table 106 shown in Figures 15(C) and 15(D) is used, the parameters related to the grinding process are controlled so that the load is the same value in the holding surface grinding process S10 and the workpiece grinding process S30.

[0179] This reduces the difference between the shape of holding surfaces 96a and 106a after grinding and the shape of one surface 11b of rectangular substrate 11 after grinding, compared to when such control is not performed. Therefore, the variation in thickness of rectangular substrate 11 after grinding can be reduced.

[0180] The structures, methods, etc. according to the above-described embodiments can be modified as appropriate without departing from the scope of the present invention. The shape of the holding surfaces 16a, 96a, 106a is not limited to a square or a rectangle, but may be a parallelogram, a rhombus, a trapezoid, or any other quadrilateral, a triangle, a pentagon, or any other polygon.

[0181] In addition, in the controller 86, the function of the hold surface grinding command unit 90 and the function of the workpiece grinding command unit 92 are essentially the same, so the controller 86 may have either the hold surface grinding command unit 90 or the workpiece grinding command unit 92. In this case, this one unit is used in both the hold surface grinding step S10 and the workpiece grinding step S30. [Explanation of symbols]

[0182] 2: Grinding equipment 4: base, 4a: recess, 4b: support structure 6: moving mechanism, 8: moving plate, 10: nut portion, 12: screw shaft, 14: driving source 11: Rectangular substrate (workpiece), 11a: Other side (back side), 11b: One side (front side) 11c: Sawmark 16: chuck table, 16a: holding surface 16a0: center, 16a1: cone-shaped region, 16a2: concave surface region 16b: corner, 16c: midpoint 18: First frame 20: second frame, 20a: recess, 20b: first flow path, 20c: second flow path, 20d: bottom surface 22: Porous board 24: Air bearing 24a: rotor, 24a1: large diameter portion, 24a2: small diameter portion, 24a3: rotation center 24b: Stator 26: Rotation drive source, 26a: Motor (first motor) 28: table base, 28a: through hole 30: Lower load sensor (second load sensor), 30a: Downward load value 32: tilt adjustment mechanism, 32a: fixed support mechanism 32b: First movable support mechanism, 32c: Second movable support mechanism 34a: fixed shaft, 34b, 34c: movable shaft, 36b: driving source, 36c: driving source 40: Cover member 42: Grinding feed mechanism (moving unit), 44: Guide rail 46: Moving plate, 48: Nut part 50: screw shaft, 52: motor (second motor) 54: Grinding unit, 56: Holding member, 58: Spindle housing 60: Upper load sensor (first load sensor), 60a: Upper load value 62: spindle, 62a: flow path 64: spindle motor, 66: wheel mount, 66a: flow path 68: Grinding wheels (first grinding wheel, second grinding wheel) 68a: Wheel base, 68a1: Flow path 68b: grinding wheel, 68c: grinding surface 70: grinding water, 72: grinding water supply source 80: power supply unit, 82: load current meter, 82a: load current value 84: Load detection unit, 84a: Information about the load 86: Controller, 86a: Processor, 86b: Memory 88: Load memory unit, 90: Holding surface grinding command unit, 92: Workpiece grinding command unit 96,106: Chuck table 96a, 106a: Holding surface, 96b: Corner, 96c: Midpoint C: Arrow, α: Minute angle, Δ: Predetermined length S5: Load value setting process S10: Grinding process for holding surface, S12: Early grinding process for holding surface, S16: Late grinding process for holding surface S14: Wheel replacement process S20: Holding process; S30: Grinding process for workpiece

Claims

1. A grinding device comprising: a chuck table having a polygonal holding surface in a plan view and rotatable around a predetermined rotation axis by a rotary drive source including a first motor; a grinding unit including a spindle disposed above the holding surface and a spindle motor for rotating the spindle, the spindle having a grinding wheel attached thereto; a moving unit having a second motor for relatively moving the chuck table and the grinding unit in a predetermined direction; a load detection unit that detects a load applied to one or both of the grinding unit and the chuck table; a controller having a processor and a memory, the controller receiving information about the load from the load detection unit; Equipped with The controller a load storage unit that stores a predetermined load value and / or information related to the load; a holding surface grinding command unit that controls parameters related to grinding when grinding the holding surface with the grinding wheel, thereby controlling the load applied to one or both of the grinding unit and the chuck table; a workpiece grinding command unit that controls parameters related to the grinding process when grinding a workpiece held on the holding surface, thereby controlling the load applied to one or both of the grinding unit and the chuck table, the load being an object of control by the holding surface grinding command unit; The controller controls parameters related to the grinding process so that the load controlled by the holding surface grinding command unit and the load controlled by the workpiece grinding command unit have the same value.

2. The load detection unit a first load sensor for detecting a first load that is a load applied to the grinding unit; a second load sensor for detecting a second load that is a load applied to the chuck table; a load current meter for measuring a load current flowing through the spindle motor; and the load on the grinding unit includes the first load and the load current; the load applied to the chuck table includes the second load, The parameters for the grinding process are: a relative moving speed between the chuck table and the grinding unit along the predetermined direction; The rotation speed of the chuck table; The rotation speed of the spindle; The flow rate of grinding water supplied per unit time; 2. The grinding apparatus according to claim 1, further comprising:

3. the parameter related to the grinding process is a relative movement speed between the chuck table and the grinding unit along the predetermined direction; when grinding the holding surface with the grinding wheel, the holding surface grinding command unit controls the moving speed so that the load applied to one or both of the grinding unit and the chuck table becomes the predetermined load value; 2. The grinding device according to claim 1, wherein, when grinding the workpiece held on the holding surface, the workpiece grinding command unit controls the moving speed so that the load that is the object of control of the holding surface grinding command unit, out of the loads applied to one or both of the grinding unit and the chuck table, becomes the predetermined load value.

4. A method for grinding a workpiece, comprising grinding a holding surface of a chuck table having a polygonal shape in a plan view, and then grinding a workpiece held by the holding surface, the method comprising: a holding surface grinding step in which a load applied to one or both of a grinding unit having a spindle and the chuck table rotatable around a predetermined rotation axis is detected by a load detection unit, and the holding surface of the chuck table is ground with a first grinding wheel attached to the spindle while the grinding unit and the chuck table are brought relatively close to each other in a predetermined direction; a holding step of holding the workpiece, which has a polygonal shape corresponding to the holding surface, on the holding surface after the holding surface grinding step; a workpiece grinding step in which, after the holding step, the load acting on one or both of the grinding unit and the chuck table is detected by the load detection unit, and the grinding unit and the chuck table are brought relatively close to each other along the predetermined direction, while the workpiece held on the holding surface is ground with a second grinding wheel attached to the spindle; Equipped with a grinding method for a workpiece, characterized in that parameters related to the grinding process are controlled so that the load applied to one or both of the grinding unit and the chuck table detected by the load detection unit in the holding surface grinding process and the load applied to one or both of the grinding unit and the chuck table detected by the load detection unit in the workpiece grinding process, which is the load to be controlled in the holding surface grinding process, have the same value.

5. the load applied to the grinding unit includes a first load applied to the grinding unit and a load current that is a load on a spindle motor that rotates the spindle; the load on the chuck table includes a second load on the chuck table; The parameters for the grinding process are: a relative moving speed between the chuck table and the grinding unit along the predetermined direction; The rotation speed of the chuck table; The rotation speed of the spindle; The flow rate of grinding water supplied per unit time; 5. The method for grinding a workpiece according to claim 4, further comprising:

6. In the holding surface grinding step, 5. The method for grinding a workpiece according to claim 4, wherein the load applied to one or both of the grinding unit and the chuck table is the load detected by the load detection unit when the workpiece is ground in the workpiece grinding process, and parameters related to the grinding process are controlled so that the load becomes the load that is known in advance.

7. In the workpiece grinding step, 5. The method for grinding a workpiece according to claim 4, wherein parameters related to the grinding process are controlled so that the load applied to one or both of the grinding unit and the chuck table becomes the load detected by the load detection unit when the holding surface is ground in the holding surface grinding process.

8. a load value setting step of setting the predetermined load value targeted in the hold surface grinding step and the workpiece grinding step before the hold surface grinding step, 5. The method for grinding a workpiece according to claim 4, wherein parameters related to the grinding process are controlled so that the load to be controlled becomes the predetermined load value in both the holding surface grinding process and the workpiece grinding process.

9. 9. A method for grinding a workpiece according to claim 4, wherein the first grinding wheel that last grinds the holding surface in the holding surface grinding process and the second grinding wheel used throughout the workpiece grinding process are the same grinding wheel.

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