Grinding wheel and workpiece grinding method

Abstract

To perform grinding similar to grinding which uses two grinding wheels having grinding characteristics different from each other by mounting one grinding wheel to one spindle.SOLUTION: A grinding wheel is mounted on a tip part of a spindle and is used for grinding a workpiece by rotating the spindle, and includes an annular base and a plurality of grinding stone sets arranged annularly along a circumferential direction of the base on one face side of the base. On each of the plurality of grinding stone sets, a first grinding stone and a second grinding stone having low self-sharpening ability as compared to the first grinding stone are provided in predetermined directions so as to be adjacent to each other on the circumferential direction of the base and, between the respective grinding stone sets, a predetermined interval is provided which is larger than the interval between the first grinding stone and the second grinding stone in the circumferential direction of the base.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a grinding wheel for grinding a workpiece and a grinding method for grinding a workpiece with the grinding wheel.

Background Art

[0002] In order to thin a semiconductor device chip, usually, after forming a device such as an IC (Integrated Circuit) on the front surface side of a wafer formed of a semiconductor such as silicon, the back surface side of the wafer is ground with a grinding device.

[0003] The grinding device includes a disk-shaped chuck table rotatable around a predetermined rotation axis. Above the chuck table, a grinding unit is arranged. The grinding unit has a spindle whose longitudinal part is arranged along the Z-axis direction (for example, the vertical direction).

[0004] An annular grinding wheel is mounted at the lower end of the spindle via a disk-shaped mount. The grinding wheel has an annular base formed of metal. On one surface (lower surface) side of the base, a plurality of grinding wheels each having abrasive grains and a bonding material are arranged at substantially equal intervals along the circumferential direction of the base.

[0005] When grinding the back surface side of the wafer by infeed grinding, the chuck table that sucks and holds the front surface side of the wafer is rotated around a predetermined rotation axis. Further, grinding water such as pure water is supplied to the back surface side of the wafer, and while rotating the grinding wheel with the spindle, the grinding unit is fed at a predetermined speed for machining (for example, see Patent Document 1).

[0006] By the way, on the surface to be ground of the wafer, there may be a layer or film having a material and properties different from those of the material constituting the wafer. For example, on the surface to be ground of a silicon carbide (SiC) wafer, there may be a modified layer in which silicon (Si) and carbon (C) are separated, and on the surface to be ground of a silicon wafer, there may be a silicon oxide film formed.

[0007] In this manner, when a layer or film made of a different material or having different properties from the material constituting the wafer body is formed on the surface to be ground, a first grinding wheel is usually used to grind the layer or film, and after the layer or film is removed, a second grinding wheel with different characteristics from the first grinding wheel is used to grind the wafer body.

[0008] However, since typically one grinding wheel is mounted on one grinding unit (i.e., one spindle), two grinding units are required to grind a wafer using a first grinding wheel and a second grinding wheel, each having different grinding characteristics.

[0009] However, when grinding wafers using two grinding machines, each having a single grinding unit, an additional step is required to transport the wafers between the grinding machines, which increases the labor involved. Furthermore, using two grinding machines in this way increases the footprint of the equipment within a cleanroom or similar indoor space. [Prior art documents] [Patent Documents]

[0010] [Patent Document 1] Japanese Patent Publication No. 2014-124690 [Overview of the project] [Problems that the invention aims to solve]

[0011] This invention has been made in view of the aforementioned problems, and aims to perform grinding on a workpiece in the same way as grinding using two grinding wheels having different grinding characteristics, by mounting one grinding wheel on one spindle. [Means for solving the problem]

[0012] According to one aspect of the present invention, a grinding wheel is mounted on the tip of a spindle and used to grind a workpiece by rotating the spindle, comprising: an annular base; and a plurality of grinding wheel sets arranged in a ring along the circumferential direction of the base on one side of the base, wherein each of the plurality of grinding wheel sets is provided with a first grinding wheel and a second grinding wheel having a lower self-sharpening ability than the first grinding wheel, adjacent to each other in a predetermined orientation along the circumferential direction of the base. Each of the plurality of grinding wheel sets is arranged such that when the spindle is rotated in a predetermined direction, one of the first grinding wheel and the second grinding wheel is in front of the other, and when the spindle is rotated in the opposite direction to the predetermined direction, the other of the first grinding wheel and the second grinding wheel is in front of the other. A grinding wheel is provided in which a predetermined gap is provided between each grinding wheel set that is larger than the gap between the first grinding wheel and the second grinding wheel in the circumferential direction of the base.

[0013] According to another aspect of the present invention, a grinding wheel having a single-crystal substrate on which a non-single-crystal layer is formed on the surface ru A grinding method for grinding a workpiece, wherein the grinding wheel comprises an annular base and a plurality of grinding wheel sets arranged in a ring along the circumferential direction of the base on one side of the base, each of the plurality of grinding wheel sets being provided adjacent to a first grinding wheel and a second grinding wheel having lower self-sharpening ability than the first grinding wheel in a predetermined orientation in the circumferential direction of the base, and a predetermined distance greater than the distance between the first grinding wheel and the second grinding wheel in the circumferential direction of the base is provided between each grinding wheel set, the method comprising a holding step of holding the back side of the substrate, which is located opposite to the front surface, with a chuck table, and after the holding step, the grinding wheel set is positioned in a predetermined direction such that the second grinding wheel is ahead of the first grinding wheel. grinding wheel A first grinding step in which the first grinding wheel is rotated and the surface side is ground to remove the non-single crystal layer, and after the first grinding step, the first grinding wheel is positioned in front of the second grinding wheel in the grinding wheel set in the opposite direction to the predetermined direction. grinding wheel A method for grinding a workpiece is provided, comprising a second grinding step of rotating a blade to grind the substrate.

[0014] Furthermore, according to yet another aspect of the present invention, a grinding wheel having a substrate on which a film is formed on its surface ruA grinding method for grinding a workpiece, wherein the grinding wheel comprises an annular base and a plurality of grinding wheel sets arranged in a ring along the circumferential direction of the base on one side of the base, each of the plurality of grinding wheel sets having a first grinding wheel and a second grinding wheel having a lower self-sharpening ability than the first grinding wheel, arranged adjacent to each other in a predetermined orientation in the circumferential direction of the base, and a predetermined distance greater than the distance between the first grinding wheel and the second grinding wheel in the circumferential direction of the base, and a holding step of holding the back side of the substrate, which is located opposite the front surface, with a chuck table, and after the holding step, the first grinding wheel in the grinding wheel set is positioned ahead of the second grinding wheel in a predetermined direction grinding wheel A first grinding step in which the grinding wheel is rotated to grind and remove the film, and after the first grinding step, the second grinding wheel is positioned in front of the first grinding wheel in the grinding wheel set in the opposite direction to the predetermined direction. grinding wheel A method for grinding a workpiece is provided, comprising a second grinding step of rotating a blade to grind the substrate. [Effects of the Invention]

[0015] Using a grinding wheel according to one aspect of the present invention, the grinding characteristics can be changed by rotating the spindle in a predetermined direction so that the second grinding wheel in the grinding wheel set is ahead of the first grinding wheel, and by rotating the spindle in the opposite direction to the predetermined direction so that the first grinding wheel in the grinding wheel set is ahead of the second grinding wheel.

[0016] In other words, by changing the rotation direction of a single spindle, it is possible to grind a workpiece with different grinding characteristics. Therefore, with one grinding wheel mounted on a single spindle, it is possible to perform grinding on a workpiece in the same way as grinding using two grinding wheels with different grinding characteristics. [Brief explanation of the drawing]

[0017] [Figure 1]Fig. 1(A) is a top view of the grinding wheel, Fig. 1(B) is a cross-sectional view of the grinding wheel, and Fig. 1(C) is a bottom view of the grinding wheel. [Figure 2] It is a perspective view of the grinding device. [Figure 3] It is a top view of a chuck table or the like. [Figure 4] It is a flowchart of the grinding method. [Figure 5] It is a diagram showing the holding step. [Figure 6] Fig. 6(A) is a diagram showing the first grinding step, and Fig. 6(B) is a partially enlarged cross-sectional view showing the first grinding step. [Figure 7] Fig. 7(A) is a diagram showing the second grinding step, and Fig. 7(B) is a partially enlarged cross-sectional view showing the second grinding step. [Figure 8] It is a diagram showing the holding step of the second embodiment. [Figure 9] It is a diagram showing the first grinding step of the second embodiment. [Figure 10] It is a diagram showing the second grinding step of the second embodiment. [Figure 11] Fig. 11(A) is a diagram showing the correspondence between the rotation direction of the chuck table and the machining area when the second grinding wheel is at the head, and Fig. 11(B) is a diagram showing the correspondence between the rotation direction of the chuck table and the machining area when the first grinding wheel is at the head.

Embodiments for Carrying Out the Invention

[0018] Embodiments according to an aspect of the present invention will be described with reference to the accompanying drawings. Fig. 1(A) is a top view of the grinding wheel 2, Fig. 1(B) is a cross-sectional view of the grinding wheel 2, and Fig. 1(C) is a bottom view of the grinding wheel 2.

[0019] The grinding wheel 2 has an annular base 4 formed of a metal such as an aluminum alloy. For example, the outer diameter of the base 4 is 200 mm, but the outer diameter of the base 4 is appropriately selected according to the purpose of grinding or the like.

[0020] Each base 4 is substantially flat and has an annular upper surface (other surface) 4a and lower surface (one surface) 4b. On the upper surface 4a, screw holes 4c are formed at approximately equal intervals along the circumferential direction of the base 4, which are used when attaching the grinding wheel 2 to the mount 28 shown in Figure 2.

[0021] Furthermore, multiple openings (not shown) for supplying grinding fluid such as pure water may be provided at approximately equal intervals along the circumferential direction of the base 4 on the frustoconical inner side surface of the base 4, which is located on the inner side of the lower surface 4b.

[0022] As shown in Figure 1(C), multiple grinding wheel sets 6 are arranged in a ring shape at approximately equal intervals along the circumferential direction of the base 4 on the lower surface 4b side of the base 4. In Figure 1(C), 24 grinding wheel sets 6 are arranged, but the number of grinding wheel sets 6 is not limited to 24.

[0023] As shown in Figure 1(B), one grinding wheel set 6 has a segmented first grinding wheel 8 and a second grinding wheel 10, respectively. The upper ends of the first grinding wheel 8 and the second grinding wheel 10 are placed in grooves formed on the lower surface 4b side of the base 4 and are fixed to the base 4 with adhesive (not shown).

[0024] Furthermore, the lower ends of the first grinding wheel 8 and the second grinding wheel 10 protrude from the lower surface 4b to a predetermined protrusion amount (also referred to as segment height). The protrusion amounts of the first grinding wheel 8 and the second grinding wheel 10 are approximately the same.

[0025] The first grinding wheel 8 and the second grinding wheel 10 are, for example, made of the same material and have abrasive grains of the same size (e.g., diamond abrasive grains), and the concentration of abrasive grains is approximately the same in both, but the material of the bonding agent and the porosity are different.

[0026] In this specification, the first grinding wheel 8 is a relatively soft grinding wheel, and the second grinding wheel 10 is a harder grinding wheel than the first grinding wheel 8. The hardness of the grinding wheels can be evaluated, for example, by a three-point bending test. The bending strength of the second grinding wheel 10 is more than twice that of the first grinding wheel 8.

[0027] The hardness of a grinding wheel depends, for example, on the material of the bonding agent. If the bonding agent of the first grinding wheel 8 is a resin bond and the bonding agent of the second grinding wheel 10 is a vitrified bond, then the hardness of the second grinding wheel 10 will be higher than that of the first grinding wheel 8.

[0028] Furthermore, for example, the hardness of a grinding wheel is due to its porosity. If the bonding material of the first grinding wheel 8 and the bonding material of the second grinding wheel 10 are both vitrified bonds with approximately the same composition, but the porosity of the first grinding wheel 8 is higher than that of the second grinding wheel 10, then the hardness of the second grinding wheel 10 will be higher than that of the first grinding wheel 8.

[0029] Similarly, if the bonding material of the first grinding wheel 8 and the bonding material of the second grinding wheel 10 are both resin bonds with substantially the same composition, but the porosity of the first grinding wheel 8 is higher than that of the second grinding wheel 10, then similarly, the hardness of the second grinding wheel 10 will be higher than that of the first grinding wheel 8.

[0030] Thus, when the hardness of the second grinding wheel 10 is higher than the hardness of the first grinding wheel 8, the force that fixes the abrasive grains in the second grinding wheel 10 with the bonding material (i.e., the bonding force) is stronger than the bonding force of the bonding material in the first grinding wheel 8.

[0031] Due to this difference in bonding strength, the relatively soft first grinding wheel 8 has a relatively high self-sharpening ability, while the relatively hard second grinding wheel 10 has a lower self-sharpening ability compared to the first grinding wheel 8.

[0032] In a single grinding wheel set 6, the first grinding wheel 8 and the second grinding wheel 10 are arranged in a predetermined orientation in the circumferential direction of the base 4. In the bottom view shown in Figure 1(C), the first grinding wheel 8 and the second grinding wheel 10 are arranged in a single grinding wheel set 6 such that the direction of movement from the second grinding wheel 10 to the first grinding wheel 8 is clockwise.

[0033] However, when the grinding wheel 2 is viewed from below in the same manner, the first grinding wheel 8 and the second grinding wheel 10 may be arranged such that the direction of movement from the first grinding wheel 8 to the second grinding wheel 10 in one grinding wheel set 6 is clockwise.

[0034] As shown in Figure 1(C), in one grinding wheel set 6, the first grinding wheel 8 and the second grinding wheel 10 are arranged adjacent to each other. In this embodiment, the first grinding wheel 8 and the second grinding wheel 10 are in substantially contact, but they may be adjacent to each other to the extent that there is a slight gap in the circumferential direction of the base 4.

[0035] The small circumferential gap between the first grinding wheel 8 and the second grinding wheel 10 of the base 4 is, for example, sufficiently smaller than a predetermined gap 6a between two adjacent grinding wheel sets 6 in the circumferential direction of the base 4.

[0036] The circumferential spacing of the base 4 between the first grinding wheel 8 and the second grinding wheel 10 is 1 / 3 or less of a predetermined spacing 6a, preferably 1 / 4 or less. For example, the circumferential spacing of the base 4 between the first grinding wheel 8 and the second grinding wheel 10 is 1 mm or less.

[0037] Furthermore, for example, the first grinding wheel 8 and the second grinding wheel 10 are close enough that abrasive grains protruding from the side surface of the first grinding wheel 8 adjacent to the second grinding wheel 10 are in contact with the second grinding wheel 10, or that abrasive grains protruding from the side surface of the second grinding wheel 10 adjacent to the first grinding wheel 8 are in contact with the first grinding wheel 8.

[0038] As described above, a predetermined interval 6a is provided between each grinding wheel set 6, and this predetermined interval 6a is greater than the slight circumferential gap between the first grinding wheel 8 and the second grinding wheel 10 on the base 4.

[0039] The predetermined spacing 6a along the circumferential direction of the base 4 is, for example, a predetermined value of 3.0 mm or more and 4.0 mm or less, but this predetermined spacing 6a is appropriately adjusted depending on the number, size, etc., of the first grinding wheel 8 and the second grinding wheel 10.

[0040] The first grinding wheel 8 and the second grinding wheel 10 are individually formed by, for example, mixing a bonding agent, abrasive grains, fillers, etc., followed by compression molding, firing, and shaping. As abrasive grains, so-called superabrasive grains such as diamond and cBN (cubic boron nitride) are used.

[0041] After shaping, the first grinding wheel 8 and the second grinding wheel 10 are fixed to the base 4 with adhesive so that they are arranged as shown in Figures 1(A) to 1(C). The grinding wheel 2 manufactured in this manner is used in a grinding device 12 to grind a workpiece 11 (see Figure 5, etc.).

[0042] Figure 2 is a perspective view of the grinding device 12. Note that Figure 2 shows the main components of the grinding device 12, and other components are omitted for convenience. Also, the Z-axis direction shown in Figure 2 is, for example, parallel to the vertical direction.

[0043] The grinding device 12 has a disc-shaped chuck table 14. The chuck table 14 has a disc-shaped frame 16 (see Figure 5) made of non-porous ceramics. A disc-shaped recess is formed on the upper part of the frame 16, and a disc-shaped porous plate 18 (see Figure 5) made of porous ceramics is fixed in this recess.

[0044] A gas channel 16a (see Figure 5) is formed in the frame 16, and a suction source (not shown), such as an ejector, is connected to one end of this gas channel 16a. The negative pressure from the suction source is transmitted to the porous plate 18 via the gas channel 16a.

[0045] The upper surface of the frame 16 and the upper surface of the porous plate 18 are substantially flush and function as a holding surface 14a that suctions and holds the workpiece 11. The central part of the porous plate 18 protrudes compared to the outer periphery, and the holding surface 14a has a conical shape.

[0046] However, the amount of protrusion in the central part is very small compared to the diameter of the holding surface 14a. For example, the amount of protrusion in the central part is 20 μm, while the diameter of the holding surface 14a is 200 mm. Therefore, for convenience, the holding surface 14a is shown as approximately flat in Figure 5.

[0047] A cylindrical rotating shaft 20 (see Figure 5) is provided at the bottom of the chuck table 14. This rotating shaft 20 rotates in a predetermined direction by a drive mechanism (not shown) such as a pulley or belt. In Figure 2, the rotation center 20a of the rotating shaft 20 is shown by a dashed line.

[0048] The chuck table 14 is rotatably supported by a table base 22. A tilt adjustment mechanism (not shown) for adjusting the tilt of the table base 22 is provided at the bottom of the table base 22.

[0049] The tilt adjustment mechanism includes a first support portion with a fixed length in the Z-axis direction, and second and third support portions whose lengths in the Z-axis direction can be independently changed. The first to third support portions are arranged at approximately equal intervals in the circumferential direction of the table base 22, and support the table base 22 at three points.

[0050] An internal nozzle (not shown) is provided near the chuck table 14 for supplying grinding water to the contact area (machining area) between the grinding wheel 2 and the workpiece. In this embodiment, since internal cutting is performed to grind the workpiece on the inner circumference side of the grinding wheel, an internal nozzle is used to supply grinding water to the inner circumference side of the grinding wheel.

[0051] Alternatively, grinding fluid may be supplied through an opening provided in the base 4. Furthermore, when performing outer-edge grinding, where the workpiece is ground on the outer circumference of the grinding wheel, an external nozzle (not shown) may be used to supply grinding fluid to the outer circumference of the grinding wheel.

[0052] A grinding unit 24 is provided above the chuck table 14. The grinding unit 24 has a cylindrical spindle housing (not shown). A ball screw type Z-axis movement unit (not shown) is attached to the spindle housing.

[0053] The Z-axis movement unit can move the spindle housing up and down along the Z-axis. For example, during grinding, the grinding unit 24 is moved downward at a predetermined machining feed rate (i.e., it is machined).

[0054] A portion of a cylindrical spindle 26 is rotatably housed in the spindle housing. A drive source (not shown), such as a motor, for rotating the spindle 26 is provided at the upper end of the spindle housing. Depending on the direction of the current supplied to the drive source, the spindle 26 can rotate in either a clockwise or counterclockwise direction.

[0055] The lower end (tip) 26a of the spindle 26 protrudes from the spindle housing. The upper side of a disc-shaped mount 28 is fixed to the lower end 26a. The grinding wheel 2 described above is attached to the lower side of the mount 28 by bolts 30.

[0056] As shown above, the grinding wheel 2 is mounted on the lower end portion 26a via the mount 28. When the grinding wheel 2 rotates due to the rotation of the spindle 26, an annular grinding surface is formed by the trajectories of the lower surfaces of the first grinding wheel 8 and the second grinding wheel 10.

[0057] The rotation axis 20 of the chuck table 14 is tilted such that a portion of the holding surface 14a, area 14b (see Figure 3), is approximately parallel to the grinding surface. Area 14b is an arc-shaped area passing through the center of the holding surface 14a.

[0058] Region 14b is located directly beneath the multiple grinding wheel sets 6, and in Figure 3, the extent of region 14b is indicated by a double-headed arrow. During grinding, the portion of the workpiece 11 held by the holding surface 14a that corresponds to region 14b is ground (i.e., becomes the processing area).

[0059] Figure 3 is a top view of the chuck table 14, etc. In Figure 3, in addition to the chuck table 14, only the multiple grinding wheel sets 6 of the grinding unit 24 located on the holding surface 14a are shown together.

[0060] Next, the grinding method of the first embodiment will be described with reference to Figures 4 to 7(B). Figure 4 is a flowchart of the grinding method in the first embodiment. In the first embodiment, infeed grinding is performed on the workpiece 11 in the order of holding step S10, first grinding step S20, and second grinding step S30.

[0061] The workpiece 11 is disc-shaped and has a single-crystal substrate (wafer) 13 mainly made of silicon carbide (SiC). When forming the workpiece 11, first, a laser beam is focused to a predetermined depth in the SiC ingot to form an amorphous region (also called a modified region, separated region, etc.).

[0062] In the amorphous region, amorphous carbon (C) and amorphous silicon (Si) are thought to be formed. After the amorphous region is formed, the substrate 13 is separated from the ingot at the amorphous region boundary.

[0063] Therefore, an amorphous layer (non-single crystal layer) 15 is formed on the surface 13a of the substrate 13 separated from the ingot. The separated surface 13a has an arithmetic mean roughness Ra of, for example, 80 μm to 100 μm.

[0064] When grinding the workpiece 11, first, the back surface 13b of the substrate 13, which is located opposite the surface 13a, is held in place by suction on the holding surface 14a (holding step S10). Figure 5 shows the holding step S10.

[0065] After the holding step S10, the first grinding step S20 is performed. Figure 6(A) shows the first grinding step S20. In the first grinding step S20, the surface 13a side is mainly ground using a second grinding wheel 10 which is relatively hard and has low self-sharpening ability in order to remove the amorphous layer 15.

[0066] In the first grinding step S20, the chuck table 14 is rotated in a predetermined direction at a predetermined value of 100 rpm to 300 rpm, and the spindle 26 is rotated in a predetermined direction at a predetermined value of 1000 rpm to 4000 rpm. Simultaneously, grinding fluid is supplied to the machining point, and the grinding unit 24 is fed at a predetermined machining feed rate of 0.1 μm / s to 2.0 μm / s.

[0067] In particular, during the first grinding step S20, the spindle 26 and grinding wheel 2 are rotated in a predetermined direction so that the second grinding wheel 10 is positioned ahead of the first grinding wheel 8 in the grinding wheel set 6. Figure 6(B) is a partially enlarged cross-sectional view showing the first grinding step S20.

[0068] As shown in Figure 6(B), in the first grinding step S20, the second grinding wheel 10 of each grinding wheel set 6 is mainly used to grind the surface 13a. Therefore, grinding can be performed that reflects the grinding characteristics of the second grinding wheel 10. Specifically, the surface 13a can be ground while reducing the amount of wear on the grinding wheel.

[0069] In the first grinding step S20, the first grinding wheel 8, which is relatively soft and has high self-sharpening ability, only traces the surface 13a that has been ground by the second grinding wheel 10. Therefore, the amount of wear on the first grinding wheel 8 is approximately the same as the amount of wear on the second grinding wheel 10.

[0070] In this way, the first grinding step S20 allows grinding of the workpiece 11 while relatively reducing the amount of wear on the grinding wheel. In the first grinding step S20, the surface 13a is ground until the amorphous layer 15 is removed and the substrate 13 body is exposed.

[0071] After the first grinding step S20, the second grinding step S30 is performed. The single-crystal substrate 13 is harder than the amorphous layer 15. When grinding this hard substrate 13, the grinding wheel is prone to becoming dull or chipped.

[0072] Therefore, in order to stably grind the substrate 13, it is necessary to proceed with grinding while promoting the self-sharpening of the grinding wheel. In the second grinding step S30, the substrate 13 is ground by effectively utilizing the first grinding wheel 8, which is relatively soft and has high self-sharpening ability.

[0073] In the second grinding step S30, the grinding unit 24 is first raised to the extent that the first grinding wheel 8 and the second grinding wheel 10 do not come into contact with the workpiece 11. The rotation direction and rotation speed of the chuck table 14 are maintained to be the same as in the first grinding step S20.

[0074] Then, in the grinding wheel set 6, the spindle 26 and grinding wheel 2 are rotated at a predetermined value of 1000 rpm to 4000 rpm in the opposite direction to the predetermined direction of the first grinding step S20, so that the first grinding wheel 8 is ahead of the second grinding wheel 10.

[0075] Subsequently, the spindle 26 is rotated, and grinding fluid is supplied to the machining point while the grinding unit 24 is fed at a predetermined machining feed rate of 0.1 μm / s to 2.0 μm / s. Figure 7(A) shows the second grinding step S30.

[0076] In the second grinding step S30, grinding can be performed that reflects the grinding characteristics of the first grinding wheel 8. Specifically, grinding can be performed that reflects high self-sharpening ability.

[0077] Furthermore, when abrasive grains 8b that have detached from the bonding material 8a of the first grinding wheel 8 enter the lower surface (grinding surface) of the second grinding wheel 10, the self-sharpening of the second grinding wheel 10, which is relatively hard and has low self-sharpening ability, is promoted.

[0078] Figure 7(B) is a partially enlarged cross-sectional view showing the second grinding step S30. As shown in Figure 7(B), in the second grinding step S30, the detached abrasive grains 8b promote the self-sharpening of the second grinding wheel 10. As a result, the amount of wear on the first grinding wheel 8 and the second grinding wheel 10 becomes approximately the same.

[0079] In this manner, in the second grinding step S30, the workpiece 11 is ground while increasing the wear of the first grinding wheel 8 and the second grinding wheel 10 compared to the first grinding step S20, and the substrate 13 is ground until a predetermined finish thickness is achieved.

[0080] In the first embodiment, using one grinding wheel 2 mounted on one spindle 26, grinding can be performed with reduced wear on the grinding wheel in the first grinding step S20, depending on the rotation direction of the spindle 26, and furthermore, high self-sharpening ability can be exhibited in the second grinding step S30. In this way, the grinding characteristics can be changed according to the rotation direction of the spindle 26.

[0081] In other words, depending on the rotation direction of the spindle 26, the workpiece 11 can be subjected to grinding similar to that performed using two grinding wheels with different grinding characteristics. Therefore, the addition of a transfer process between grinding devices and an increase in the footprint of the grinding devices can be suppressed.

[0082] Furthermore, since multiple grinding wheel sets 6 are arranged in a ring along the circumferential direction of the base 4, the inner and outer diameters of the grinding surface of the grinding wheel 2 can be made approximately the same regardless of the direction of rotation of the spindle 26.

[0083] Incidentally, according to experiments conducted by the applicant, when the amount of wear of the first grinding wheel 8 and the second grinding wheel 10 in the first grinding step S20 is set to 1, the amount of wear of the first grinding wheel 8 and the second grinding wheel 10 in the second grinding step S30 was 1.5.

[0084] (Comparative experiment) In contrast, a comparative experiment was conducted in which one side of a workpiece was ground using a grinding wheel in which the first grinding wheel 8 and the second grinding wheel 10 were arranged alternately in a ring along the circumferential direction of the base 4 at predetermined intervals of 3.0 mm to 4.0 mm.

[0085] In comparative experiments, the amount of wear on the first grinding wheel 8 and the second grinding wheel 10 was approximately the same in the first step, where the grinding wheel was rotated in a predetermined direction to grind the workpiece, and in the second step, where the grinding wheel was rotated in the opposite direction to the predetermined direction to grind the workpiece.

[0086] Therefore, in order to change the grinding characteristics according to the direction of rotation, it can be said that the circumferential spacing between the bases 4 of the first grinding wheel 8 and the second grinding wheel 10 that constitute one grinding wheel set 6 must be narrower than the circumferential spacing between the grinding wheel sets 6 themselves.

[0087] Next, a second embodiment will be described. In the second embodiment, the workpiece 21 (see Figure 8) is ground using a grinding device 12 equipped with the grinding wheel 2 described above, according to the grinding method shown in the flowchart in Figure 4.

[0088] As shown in Figure 8, the workpiece 21 has a single-crystal substrate (wafer) 23 mainly made of silicon. The substrate 23 has a disc shape, and a film 25 made of a different material from the substrate 23 itself is formed on the surface 23a of the substrate 23, such as a silicon oxide (e.g., SiO2) film, a silicon nitride (e.g., Si3N4) film, or a metal film.

[0089] When grinding the workpiece 21, first, the back surface 23b of the substrate 23, which is located opposite the surface 23a, is held in place by suction on the holding surface 14a (holding step S10). Figure 8 shows the holding step S10 of the second embodiment.

[0090] After the holding step S10, the first grinding step S20 is performed. Figure 9 shows the first grinding step S20 of the second embodiment.

[0091] In the first grinding step S20, the chuck table 14 is rotated in a predetermined direction at a predetermined value of 100 rpm to 300 rpm, and the spindle 26 is rotated in a predetermined direction at a predetermined value of 3000 rpm to 4000 rpm. Simultaneously, grinding fluid is supplied to the machining point, and the grinding unit 24 is fed through grinding at a predetermined machining feed rate of 0.1 μm / s to 2.0 μm / s.

[0092] In the first grinding step S20, the spindle 26 and grinding wheel 2 are rotated in a predetermined direction so that the first grinding wheel 8 is ahead of the second grinding wheel 10 in the grinding wheel set 6.

[0093] In the first grinding step S20, the film 25 is ground using a first grinding wheel 8 that is relatively soft and has high self-sharpening ability, in order to grind metal films that are relatively soft and prone to clogging of the grinding wheel during grinding, and silicon oxide films and silicon nitride films that are relatively hard and prone to dulling and chipping of the grinding wheel during grinding.

[0094] Therefore, grinding can be performed that reflects the grinding characteristics of the first grinding wheel 8. Specifically, grinding can be performed that reflects the high self-sharpening ability of the first grinding wheel 8.

[0095] Furthermore, in the first grinding step S20, the film 25 can be ground using the first grinding wheel 8, which has high self-sharpening ability, and the film 25 can also be ground using the second grinding wheel 10 while promoting the self-sharpening of the second grinding wheel 10 with the detached abrasive grains 8b.

[0096] In the first grinding step S20, the wear amounts of the first grinding wheel 8 and the second grinding wheel 10 are approximately the same. In the first grinding step S20, the surface 23a is ground until the film 25 is removed, exposing the substrate 23 body. After the first grinding step S20, the second grinding step S30 is performed.

[0097] In the second grinding step S30, the grinding unit 24 is first raised to the extent that the first grinding wheel 8 and the second grinding wheel 10 do not come into contact with the workpiece 11. The rotation direction and rotation speed of the chuck table 14 are maintained to be the same as in the first grinding step S20.

[0098] Then, in the grinding wheel set 6, the spindle 26 and grinding wheel 2 are rotated at a predetermined value of 3000 rpm to 4000 rpm in the opposite direction to the predetermined direction of the first grinding step S20, so that the second grinding wheel 10 is positioned ahead of the first grinding wheel 8.

[0099] Subsequently, the spindle 26 is rotated, and grinding fluid is supplied to the machining point while the grinding unit 24 is fed at a predetermined machining feed rate of 0.5 μm / s to 2.0 μm / s. Figure 10 shows the second grinding step S30 of the second embodiment.

[0100] In the second grinding step S30, the processing feed is performed for a predetermined time, and the substrate 23 is ground until a predetermined finish thickness is achieved. In the second grinding step S30, the second grinding wheel 10 of each grinding wheel set 6 is used to primarily grind the surface 23a side.

[0101] Therefore, in the second grinding step S30, grinding can be performed that reflects the grinding characteristics of the second grinding wheel 10. Specifically, the surface 23a can be ground while reducing the amount of wear on the grinding wheel.

[0102] In the second grinding step S30, the first grinding wheel 8 traces the surface 13a that the second grinding wheel 10 has ground, so the amount of wear on the first grinding wheel 8 is approximately the same as the amount of wear on the second grinding wheel 10.

[0103] In the second embodiment, by using the grinding wheel 2 to change the rotation direction of the spindle 26, high self-sharpening ability can be achieved in the first grinding step S20, and grinding with reduced wear of the grinding wheel can be performed in the second grinding step S30.

[0104] In this way, using a single grinding wheel 2 mounted on a single spindle 26, it is possible to perform grinding on the workpiece 21 in the same manner as grinding using two grinding wheels with different grinding characteristics. Therefore, it is possible to suppress the addition of a transport process between grinding devices and the increase in the footprint of the grinding devices.

[0105] Next, with reference to Figures 11(A) and 11(B), modifications of the first and second embodiments will be described. In the first and second embodiments described above, the rotation direction of the chuck table 14 is kept the same.

[0106] However, in this modified example, the rotation direction of the chuck table 14 and the inclination of the table base 22 are changed according to the rotation direction of the spindle 26 so that the grinding method is both external and internal grinding, and internal cutting edge grinding.

[0107] External grinding refers to grinding a workpiece by advancing the grinding wheel from the outer periphery towards the center. The rotation direction of the chuck table 14 can be changed by the drive mechanism described above, and the tilt of the table base 22 can be adjusted by the tilt adjustment mechanism described above.

[0108] Figure 11(A) shows the relationship between the rotation direction of the chuck table 14 and the machining area (area 14b) which is approximately parallel to the grinding surface, when the second grinding wheel 10 of the grinding wheel set 6 is positioned first. However, the workpiece on the holding surface 14a is omitted in Figure 11(A).

[0109] In the top view shown in Figure 11(A), the rotation direction of the chuck table 14 and the grinding wheel 2 is approximately the same clockwise direction, and region 14b exists in the right half of the holding surface 14a.

[0110] Figure 11(B) shows the relationship between the rotation direction of the chuck table 14 and the machining area (area 14b) which is approximately parallel to the grinding surface, when the first grinding wheel 8 of the grinding wheel set 6 is positioned at the front. However, the workpiece on the holding surface 14a is omitted in Figure 11(B).

[0111] In the top view shown in Figure 11(B), the rotation direction of the chuck table 14 and the grinding wheel 2 is approximately the same, counterclockwise. Also, the inclination of the table base 22 differs from the inclination in Figure 11(A), with a region 14b existing in the left half of the holding surface 14a.

[0112] In this modified example, the rotation direction of the chuck table 14 and the inclination of the table base 22 are changed according to the rotation direction of the spindle 26, so that the grinding method can be maintained as both external and internal grinding, and internal cutting edge grinding.

[0113] Furthermore, the structures, methods, etc., according to the embodiments described above can be modified as appropriate without departing from the scope of the object of the present invention. [Explanation of Symbols]

[0114] 2: Grinding wheel, 4: Base, 4a: Top surface (other side), 4b: Bottom surface (one side), 4c: Screw hole 6: Grinding wheel set, 6a: Spacing 8: First grinding wheel, 8a: Bonding material, 8b: Abrasive grains, 10: Second grinding wheel 11: Workpiece, 13: Substrate, 13a: Front surface, 13b: Back surface 15: Amorphous layer (non-single crystal layer) 12: Grinding device, 14: Chuck table, 14a: Holding surface, 14b: Area 16: Frame, 16a: Gas channel, 18: Porous plate 20: Axis of rotation, 20a: Center of rotation, 22: Table base 21: Workpiece, 23: Substrate, 23a: Front surface, 23b: Back surface, 25: Film 24: Grinding unit, 26: Spindle, 26a: Lower end (tip) 28: Mount, 30: Bolt S10: Holding step, S20: First grinding step, S30: Second grinding step

Claims

1. A grinding wheel mounted on the tip of a spindle, for grinding a workpiece by rotating the spindle, A ring-shaped base, The base comprises a plurality of grinding wheel sets arranged in a ring along the circumferential direction of the base on one side of the base, Each of the multiple grinding wheel sets is provided with a first grinding wheel and a second grinding wheel having a lower self-sharpening ability than the first grinding wheel, arranged adjacent to each other in a predetermined orientation in the circumferential direction of the base. Each of the plurality of grinding wheel sets is arranged such that when the spindle is rotated in a predetermined direction, one of the first grinding wheel and the second grinding wheel is in front of the other, and when the spindle is rotated in the opposite direction to the predetermined direction, the other of the first grinding wheel and the second grinding wheel is in front of the other. A grinding wheel characterized in that a predetermined gap is provided between each grinding wheel set, which is larger than the gap between the first grinding wheel and the second grinding wheel in the circumferential direction of the base.

2. A grinding method for grinding a workpiece having a single-crystal substrate on which a non-single-crystal layer is formed on the surface, using a grinding wheel, The grinding wheel is A ring-shaped base, The base comprises a plurality of grinding wheel sets arranged in a ring along the circumferential direction of the base on one side of the base, Each of the multiple grinding wheel sets is provided with a first grinding wheel and a second grinding wheel having a lower self-sharpening ability than the first grinding wheel, arranged adjacent to each other in a predetermined orientation in the circumferential direction of the base. Between each grinding wheel set, there is a predetermined spacing that is larger than the spacing between the first grinding wheel and the second grinding wheel in the circumferential direction of the base. A holding step in which the back side of the substrate, located opposite to the front side, is held by suction using a chuck table, After the holding step, the first grinding step involves rotating the grinding wheel in a predetermined direction so that the second grinding wheel is ahead of the first grinding wheel in the grinding wheel set, and grinding the surface to remove the non-single crystal layer. Following the first grinding step, a second grinding step is performed in which the grinding wheel is rotated in the opposite direction to the predetermined direction so that the first grinding wheel is ahead of the second grinding wheel in the grinding wheel set, and the substrate is ground. A method for grinding a workpiece, characterized by comprising the following features.

3. A grinding method for grinding a workpiece having a substrate on which a film is formed on its surface using a grinding wheel, The grinding wheel is A ring-shaped base, The base comprises a plurality of grinding wheel sets arranged in a ring along the circumferential direction of the base on one side of the base, Each of the multiple grinding wheel sets is provided with a first grinding wheel and a second grinding wheel having a lower self-sharpening ability than the first grinding wheel, arranged adjacent to each other in a predetermined orientation in the circumferential direction of the base. Between each grinding wheel set, there is a predetermined spacing that is larger than the spacing between the first grinding wheel and the second grinding wheel in the circumferential direction of the base. A holding step in which the back side of the substrate, located opposite to the front side, is held by suction using a chuck table, After the holding step, the first grinding step involves rotating the grinding wheel in a predetermined direction so that the first grinding wheel is ahead of the second grinding wheel in the grinding wheel set, thereby grinding and removing the film. Following the first grinding step, a second grinding step is performed in which the grinding wheel is rotated in the opposite direction to the predetermined direction so that the second grinding wheel is positioned ahead of the first grinding wheel in the grinding wheel set, and the substrate is ground. A method for grinding a workpiece, characterized by comprising the following features.

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