JP5430975B2 - Work processing method and work processing apparatus - Google Patents

Description

  The present invention relates to a workpiece processing method and a workpiece processing apparatus for grinding a plate-shaped workpiece so as to form a ring-shaped reinforcing portion at an outer edge portion.

  In the semiconductor device manufacturing process, a plurality of regions are partitioned by dividing lines called streets arranged in a lattice pattern on the surface of a substantially wafer-shaped semiconductor wafer, and devices such as ICs, LSIs, etc. are partitioned in the partitioned regions. Form. Then, the semiconductor wafer is cut along the streets to divide the region in which the device is formed to manufacture individual semiconductor chips. In addition, optical device wafers in which gallium nitride compound semiconductors are stacked on the surface of a sapphire substrate are also divided into optical devices such as individual light emitting diodes and laser diodes by cutting along the streets, and are widely used in electronic equipment. ing.

  The wafer to be divided as described above is formed to have a predetermined thickness by grinding or etching the back surface before cutting along the street. In recent years, it has been required to form a wafer with a thickness of 50 μm or less in order to reduce the weight and size of electronic devices.

  However, when the thickness of the wafer is formed to be 50 μm or less, there is a problem that the wafer is easily damaged and handling such as wafer conveyance becomes difficult.

  In order to solve such problems, the area corresponding to the device area on the back surface of the wafer is ground to form the thickness of the device area to a predetermined thickness, and the outer peripheral surplus area on the back surface of the wafer is left to remain in the ring. There has been proposed a wafer processing method in which a thin reinforcing portion is formed to facilitate handling of a thinned wafer (for example, see Patent Document 1).

JP 2007-19461 A

  According to Patent Document 1, even when the thickness of the wafer is formed to be 50 μm or less, it is not easily damaged and handling such as conveyance becomes easy. In an actual grinding process, the wafer is processed so that a ring-shaped reinforcing portion is formed by sequentially performing two-stage grinding processes of a rough grinding process and a finish grinding process. Such two-stage grinding is performed with the grinding surface of the grinding wheel inclined with respect to the holding surface for holding the wafer in order to improve the processing quality for the wafer. However, if the angle of inclination formed by the grinding surface in each cutting process with respect to the holding surface is too small, the abrasive grains that fall off during the grinding process will bite between the grinding surface and the surface to be ground, causing scratches on the surface to be ground. Conversely, if the inclination angle is too large, the TTV indicating the flatness of the surface to be ground may be poor.

  The present invention has been made in view of the above, and by grinding a plate-like workpiece in two stages by rough grinding and finish grinding so that a ring-shaped reinforcing portion is formed, the abrasive grains are dropped. An object of the present invention is to provide a workpiece machining method and workpiece machining apparatus that can suppress the occurrence of scratches and maintain the flatness of the surface to be ground.

In order to solve the above-described problems and achieve the object, a workpiece processing method according to the present invention includes a holding unit having a holding surface that holds a plate-like workpiece and is driven to rotate about a rotation axis, and the holding surface. A first grinding wheel for rough grinding having a first grinding surface opposite to the first grinding wheel, and the first grinding wheel can be rotated with a vertical axis perpendicular to the first grinding surface as a first rotation axis A first processing means having a first spindle part supported on the second grinding wheel, a second grinding wheel for finish grinding having a second grinding surface facing the holding surface, and the second grinding wheel. And a second processing means having a second spindle part rotatably supporting a vertical axis perpendicular to the second grinding surface as a second rotation axis, and It has a device area where the device is formed and a surplus area surrounding the device area. A ring-shaped reinforcing portion on the back surface side corresponding to the surplus region is obtained by sequentially grinding a region on the back surface side corresponding to the device region of the plate-like workpiece with the first grinding surface and the second grinding surface. A holding step of holding the surface side of the plate-like workpiece on the holding surface, and a first inclination angle relative to the rotation axis relative to the first rotation axis. The outer peripheral edge of the first grinding wheel corresponds to the surplus region and the plate shape with respect to the back side of the plate-like workpiece held on the holding surface in a slightly inclined state. A first machining step in which the first grinding surface is positioned so as to pass through the center of the workpiece and rough grinding is performed; and the second rotation axis is relatively set with respect to the rotation axis. Slightly inclined by a second inclination angle smaller than the inclination angle In this state, the outer peripheral edge of the second grinding wheel is inside the region corresponding to the surplus region with respect to the back surface side of the plate-like workpiece that is held on the holding surface and has undergone the first machining step. so as to pass through the center of the plate-shaped workpiece, a second processing step of performing finish grinding position the second grinding surface, only contains the first angle of inclination, the first grinding wheel It is characterized in that it is set at an angle larger than the grain size .

  According to the workpiece machining method and workpiece machining apparatus according to the present invention, it is found that the relationship between the occurrence of scratches due to the removal of abrasive grains and the flatness of the surface to be ground is a trade-off, and the first grinding is performed. The first rotation axis of the processing means is slightly inclined relative to the rotation axis by a first inclination angle, while the second rotation axis of the second processing means for performing finish grinding is relative to the rotation axis. By slightly inclining by a second inclination angle that is relatively smaller than the first inclination angle, the first inclination angle is relatively large during the rough grinding by the first processing means, so that the falling abrasive grains In the finish grinding process by the second processing means, the second inclination angle is relatively small but the abrasive grains are small and the ductility mode is dominant, and there are falling abrasive grains. But the effect of scratches is real Manner without addition, since the second inclination angle relatively small, an effect that it is possible to finish the abradable surface in good condition flatness.

FIG. 1 is a perspective view showing a configuration example of a workpiece machining apparatus for carrying out a workpiece machining method according to an embodiment of the present invention. FIG. 2A is a schematic diagram illustrating an inclined state of the first rotation shaft. FIG. 2-2 is a schematic diagram illustrating an inclined state of the second rotating shaft. FIG. 3A is a perspective view illustrating the surface side of the plate-like workpiece. FIG. 3-2 is a perspective view illustrating the back side of the plate-like workpiece. FIG. 4 is a diagram showing a positioning state in the first processing step. FIG. 5 is a diagram showing a state during processing in the first processing step. FIG. 6 is a diagram illustrating a state after processing by the first processing step. FIG. 7 is a diagram showing a positioning state in the second processing step. FIG. 8 is a diagram showing a state during processing in the second processing step. FIG. 9 is a diagram illustrating a state after processing by the second processing step.

  Hereinafter, a workpiece machining method and a workpiece machining apparatus, which are embodiments for carrying out the present invention, will be described with reference to the drawings. FIG. 1 is a perspective view illustrating a configuration example of a workpiece machining apparatus for carrying out the workpiece machining method according to the present embodiment, and FIG. 2A is a schematic diagram illustrating an inclined state of a first rotating shaft. FIG. 2-2 is a schematic diagram illustrating an inclined state of the second rotating shaft. As will be described later, the workpiece processing apparatus 1 according to the present embodiment grinds a region corresponding to the device region on the back surface of the plate-shaped workpiece to form a thickness of the device region to a predetermined thickness, and the back surface of the plate-shaped workpiece. The ring-shaped reinforcing portion is formed by leaving the outer peripheral surplus region. The workpiece machining apparatus 1 according to the present embodiment includes, for example, a housing 2, a first machining means 3, a second machining means 4, for example, three holding means 6 installed on a turntable 5, and a cassette. 7, 8, positioning means 9, transport means 10, carry-out means 11, cleaning means 12, carry-in / out means 13, and control means 14.

  The turntable 5 is a disk-like one provided on the upper surface of the housing 2, is provided rotatably in a horizontal plane, and is driven to rotate at an appropriate timing. On the turntable 5, for example, three holding means 6 are arranged at equal intervals with a phase angle of 120 degrees, for example. These holding means 6 have a chuck table structure having a vacuum chuck on the upper surface, and hold the plate-like workpiece W placed on a flat holding surface 6s by vacuum suction. At the time of grinding, these holding means 6 are rotationally driven in a horizontal plane around a rotation axis φ0 perpendicular to the holding surface 6s by a rotation driving mechanism (not shown). Such a holding means 6 is brought into contact with a carry-in / out standby position A, a rough grinding position B facing the first processing means 3, and a finish grinding position C facing the second processing means 4 by the rotation of the turntable 5. Moved relative to each other.

  The first processing means 3 includes a first grinding wheel 3b having a first grinding surface 3a facing the holding surface 6s of the holding means 6 located at the rough grinding position B, and the first grinding wheel 3b. A first spindle portion 3c that rotatably supports a vertical axis perpendicular to the grinding surface 3a as a first rotation axis φ1, and the first spindle portion 3c is an axis of the first rotation axis φ1 And a first slide portion 3d that is supported so as to be movable back and forth in the direction. Here, as the first grinding wheel 3b, a coarse grinding stone having a coarse abrasive grain size is used. That is, the rough grinding is performed while rotating the first grinding wheel 3b having the first grinding surface 3a detachably attached to the lower end of the first spindle portion 3c around the first rotation axis φ1 by the motor 3e. The upper surface of the plate-like workpiece W held on the holding surface 6s of the holding means 6 located at the position B is pressed and brought into contact with the upper surface of the plate-like workpiece W by the first slide portion 3d, so that it is predetermined as will be described later. For rough grinding. Although not shown, the first processing means 3 has a mechanism for setting the first rotation axis φ1 to be inclined with respect to the rotation axis φ0.

  The second processing means 4 includes a second grinding wheel 4b having a second grinding surface 4a facing the holding surface 6s of the holding means 6 located at the finish grinding position C, and the second grinding wheel 4b. A second spindle portion 4c that rotatably supports a vertical axis perpendicular to the second grinding surface 3b as a second rotation axis φ2, and the second spindle portion 4c is an axis of the second rotation axis φ2. And a second slide portion 4d that is supported so as to be able to advance and retreat in the direction. Here, as the second grinding wheel 4b, one for fine grinding with fine abrasive grains is used. That is, finish grinding is performed by rotating a second grinding wheel 4b having a second grinding surface 4a detachably mounted on the lower end of the second spindle portion 4c about the second rotation axis φ2 by a motor 4e. The upper surface of the plate-like workpiece W held on the holding surface 6s of the holding means 6 located at the position C is brought into press contact with the upper surface of the plate-like workpiece W by the second slide portion 4d, so that the predetermined upper surface of the plate-like workpiece W is described later. It is for performing the finish grinding process. Although not shown, the second processing means 4 has a mechanism for setting the second rotation axis φ2 to be inclined with respect to the rotation axis φ0.

  The first and second slide portions 3d and 4d of the first and second processing means 3 and 4 are provided so as to be moved up and down by the lifting and lowering feeding means 15 and 16, respectively. 3b and 4b are configured to be capable of being ground and fed to the upper surface of the plate-like workpiece W on the holding means 6. These elevating and feeding means 15 and 16 are mounted on movable blocks 17 and 18 provided on the upper surface of the housing 2. The movable blocks 17 and 18 are moved so that the first and second grinding wheels 3b and 4b move forward and backward in the radial direction of the turntable 5 with respect to the holding means 6 positioned at the rough grinding position B or the finish grinding position C. The housing 2 is movably provided by a moving mechanism (not shown).

The cassettes 7 and 8 are containers for plate-like workpieces having a plurality of slots. One cassette 7 accommodates the plate-like workpiece W before grinding, and the other cassette 8 accommodates the plate-like workpiece W after grinding. The plate-like workpiece W is not particularly limited. For example, a semiconductor wafer such as silicon wafer or GaAs, ceramic, glass, sapphire (Al ₂ O ₃ ) -based inorganic material substrate, plate-like metal or resin ductile material, Further, in-plane flatness (TTV: Total Thickness Variation): the maximum and minimum values of the entire surface of the plate workpiece measured in the thickness direction with the surface to be ground of the plate workpiece as the reference surface Various processing materials that require a difference between the two.

  The alignment means 9 is a table on which the plate-like workpiece W taken out from the cassette 7 is temporarily placed and its center is aligned. The carry-in means 10 is composed of a transfer arm that has a suction pad and is driven to rotate in a horizontal plane, and sucks and holds the plate-like work W before grinding that has been aligned by the alignment means 9 to carry-in / out standby position A. It is carried onto the holding means 6 located at the position. The unloading means 11 includes a transfer arm having a suction pad and rotationally driven in a horizontal plane, and holds the plate-like workpiece W after grinding held on the holding means 6 positioned at the load / unload standby position A by suction. Then, it is carried out to the cleaning means 12. The carry-in / out means 13 is, for example, a robot pick provided with a U-shaped hand 13a. The U-shaped hand 13a sucks and holds the plate-like workpiece W and conveys it. Specifically, the carry-in / out means 13 carries the plate-like workpiece W before grinding from the cassette 7 to the alignment means 9 and carries the plate-like workpiece W after grinding into the cassette 8 from the cleaning means 12. . The cleaning means 12 cleans the plate-like workpiece W after grinding, and removes contamination such as grinding dust adhering to the ground processing surface.

  Furthermore, the control means 14 consists of a microcomputer, and controls the operation | movement of each part of the workpiece | work processing apparatus 1 in order to perform a desired grinding process with respect to the plate-shaped workpiece | work W. FIG.

  In such a workpiece processing apparatus 1, when both the holding means 6 located at the rough grinding position B and the first grinding wheel 3 b rotate counterclockwise, the first rotating shaft of the first processing means 3 is used. As shown in FIG. 2A, the first φ 1 is such that the first lower side of the holding means 6 is forwardly lowered with respect to the rotation axis φ 0 perpendicular to the holding surface 6 s in the rotation direction (circumferential direction) of the holding surface 6 s. It is set to be slightly inclined by the inclination angle α.

  When both the holding means 6 and the second grinding wheel 4b positioned at the finish grinding position C rotate clockwise, the second rotation axis φ2 of the second processing means 4 is as shown in FIG. As shown in the figure, the second tilt angle β is slightly inclined with respect to the rotation axis φ0 perpendicular to the holding surface 6s of the holding means 6 so as to be forwardly lowered in the rotation direction (circumferential direction) of the holding surface 6s. Is set. That is, the second rotation axis φ2 is inclined in the direction opposite to the first rotation axis φ1 with respect to the rotation axis φ0. Further, the second inclination angle β is set to an angle smaller than the first inclination angle α. In addition, although these 1st, 2nd inclination-angle (alpha) and (beta) are shown by the exaggerated angle on drawing, it is a minute angle set within the range of 0-0.5 degree | times, for example.

  Next, the plate-like workpiece W that is an object to be ground in the present embodiment will be described. FIG. 3A is a perspective view showing the front surface side of the plate-like workpiece W, and FIG. 3-2 is a perspective view showing the back surface side of the plate-like workpiece W. In the plate-like workpiece W to be ground in the present embodiment, a plurality of devices partitioned vertically and horizontally are entirely formed on the surface Wa side, and a region having devices effective for commercialization (FIG. 3). -1 is a device area W1, and an outer area surrounding the device area W1 is a surplus area W2.

  In the present embodiment, the back surface Wb corresponding to the device region W1 of the plate-like workpiece W is ground from the back surface Wb side as a region to be ground to form a ring-shaped reinforcing portion on the back surface Wb corresponding to the surplus region W2. So that it is ground. Therefore, the first and second grinding wheels 3b and 4b of the present embodiment are formed so that the diameter of the outermost circumference of the rotation locus is larger than the radius of the device region W1 and smaller than the diameter of the device region W1. Has been.

  Hereinafter, with reference to FIGS. 4-9, the processing method of the plate-shaped workpiece | work W of this Embodiment performed under control by the control means 14 is demonstrated.

(Holding process)
First, the plate-like workpiece W before grinding is taken out from the cassette 7 by the carry-in / out means 13 and centered by the positioning means 9 and then sucked and held by the carrying means 10 from above and positioned at the carry-in / out standby position A. It is carried on the holding surface 6s of the holding means 6 to be sucked and held. At this time, the plate-like workpiece W is set so that the back surface Wb side to be ground becomes the top surface.

(First processing step)
Next, by rotating the turntable 5 120 degrees, the holding means 6 that has been located at the loading / unloading standby position A is positioned at the rough grinding position. Then, the holding surface 6s holding the plate-like workpiece W is rotated counterclockwise about the rotation axis φ0, and the first grinding wheel 3b of the first processing means 3 is rotated counterclockwise to The center portion is ground into a concave shape from the back surface Wb side of the workpiece W. First, by moving the movable block 17 back and forth, as shown in FIG. 4, the outer peripheral edge of the first grinding wheel 3b is inside the region corresponding to the surplus region W2 (the boundary between the device region W1 and the surplus region W2). The first grinding surface 3a is positioned so as to pass through the center W0 of the plate-like workpiece W. Then, as shown in FIG. 5, the first grinding wheel 3 b rotating at a high speed is lowered with respect to the back surface Wb of the plate-like workpiece W by the lifting and lowering feeding means 15 and is fed by grinding, as shown in FIG. 6. Then, grinding is performed so that the arc-shaped first grinding mark 21 is formed, and the back surface Wb corresponding to the device region W1 of the plate-like workpiece W is defined as the concave portion W3.

  Here, in the grinding process shown in FIG. 5, the first inclination angle α so that the first rotation axis φ1 of the first grinding wheel 3b is lowered forward in the rotation direction with respect to the rotation axis φ0 of the holding means 6. In the first grinding surface 3a, the half of the front lowering shown in the shaded state is in contact with the plate-like workpiece W and shows the grinding action, and the half of the rear raising is the plate. Since it floats from the workpiece W, the portion from the center W0 of the plate workpiece W to the inside of the region corresponding to the surplus region W2 is slightly ground into a concave shape. Reference numeral 22 denotes a concave shape portion formed on the back surface Wb of the plate-like workpiece W by grinding with the first grinding wheel 3b inclined forward and downward. The grinding traces in this case are arc-shaped first grinding traces 21 as shown in FIG.

  In such a first processing step, even when falling abrasive grains are generated during the grinding process by the first grinding wheel 3b, the first inclination angle α of the first rotation shaft φ1 with respect to the rotation shaft φ0 is the grinding angle. The angle is set at a relatively large angle so as to be larger than the grain size of the grains, and the falling abrasive grains from the first grinding wheel 3b are caught between the first grinding wheel 3b and the concave shape portion 22. Since it becomes difficult, scratches are unlikely to occur in the concave surface portion 22. On the other hand, since the first inclination angle α of the first rotation axis φ1 with respect to the rotation axis φ0 is relatively large, as shown in FIG. 6B, the in-plane flatness (TTV) is deteriorated.

(Second processing step)
Next, by rotating the turntable 5 by 120 degrees, the holding means 6 located at the rough grinding position B is positioned at the finish grinding position. Then, the holding surface 6s holding the plate-like workpiece W that has been subjected to rough grinding is rotated clockwise about the rotation axis φ0, and the second grinding wheel 4b of the second processing means 4 is rotated clockwise. Then, the center part (concave part W3) is further ground into a concave shape from the back surface Wb side of the plate-like workpiece W. First, by moving the movable block 18 back and forth, as shown in FIG. 7, the outer peripheral edge of the second grinding wheel 4b is inside the region corresponding to the surplus region W2 (the boundary between the device region W1 and the surplus region W2). The second grinding surface 4a is positioned so as to pass through the center W0 of the plate-like workpiece W. Then, as shown in FIG. 8, the second grinding wheel 4b rotating at a high speed is lowered and fed to the back surface Wb of the plate-like workpiece W by the lifting and lowering feeding means 16, as shown in FIG. In addition, grinding is performed so that the arc-shaped second grinding mark 23 is formed. In this way, grinding is performed from the back surface Wb side of the plate-like workpiece W, leaving the surplus area W2 of the plate-like workpiece W, and the concave shape portion W3 and this concave shape portion W3 are ground on the back surface Wb side of the plate-like workpiece W. The processing step for forming the surrounding ring-shaped reinforcing portion W4 ends. This reinforcement part W4 becomes a holding part by the carrying-out means 11 etc. after completion | finish of cutting.

  Here, in the grinding process shown in FIG. 8, the second inclination angle β so that the second rotation axis φ2 of the second grinding wheel 4b is lowered forward in the rotation direction with respect to the rotation axis φ0 of the holding means 6. In the second grinding surface 4a of the second grinding surface 4a, the half of the front lowering shown in the shaded state is in contact with the plate-like workpiece W and shows the grinding action, and the half of the rear raising is the plate Since it floats from the workpiece W, the portion from the center W0 of the plate workpiece W to the inside of the region corresponding to the surplus region W2 is slightly ground into a concave shape. Reference numeral 24 denotes a concave shape portion formed on the back surface Wb of the plate-like workpiece W by grinding with the second grinding wheel 4b inclined forward and downward.

  In this case, the grinding trace is an arc-shaped second grinding trace 23 that intersects the first grinding trace 21 as shown in FIG. That is, since the second inclination angle β of the second rotation axis φ2 is set in the direction opposite to the first inclination angle α of the first rotation axis φ1, the finish grinding by the second grinding surface 4a is performed. The second grinding mark 23 formed at the time of processing intersects the first grinding mark 21 formed by rough grinding. As a result, as shown by the broken line in FIG. 9A, the first grinding trace 21 is erased by finish grinding, and the first grinding trace and the second grinding trace are continuously formed in the same direction. Accordingly, it is possible to prevent the strength of the surface to be ground from being lowered. Therefore, when the plate-like workpiece W is ground so that the ring-shaped reinforcing portion W4 is formed, even if the plate-like workpiece W is ground thinner, the surface to be ground is cracked. Can be suppressed.

  In such a second processing step, the second inclination angle β of the second rotation axis φ2 with respect to the rotation axis φ0 is smaller than the first inclination angle α. Because it is small, it is difficult to bite. Further, in the finish grinding using the second grinding wheel 4b for finish grinding, the abrasive grains collide with the work surface and the plate workpiece is removed by the impact as in the first machining step. This is a process in which the ductile mode in which the abrasive grain scoops the surface to be ground like a bite is dominant, so even if the occlusion by the falling abrasive grains occurs, the effect of scratches by the falling abrasive grains is It is virtually negligible. On the other hand, since the second inclination angle β of the second rotation axis φ2 with respect to the rotation axis φ0 is smaller than the first inclination angle α, as shown in FIG. 9B, the in-plane flatness (TTV) Can finish in good condition.

  Therefore, according to the present embodiment, when the plate-like workpiece W is ground in two stages by rough grinding and finish grinding so as to form the ring-shaped reinforcing portion W4, Generation | occurrence | production can be suppressed and the flatness of a to-be-ground surface can be maintained.

  The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, in the present embodiment, the first and second rotating shafts φ 1 and φ 2 of the first and second grinding wheels 3 b and 4 b with respect to the rotating shaft φ 0 of the holding unit 6 are arranged in the rotation direction of the holding unit 6. Although the first and second inclination angles α and β are slightly inclined in the forward downward direction, they may be inclined relatively, and the rotation axis φ0 side of the holding means 6 may be inclined. However, if the rotation axis φ0 on the holding means 6 side can be set to be tilted, the receiving may be weakened. Therefore, the rotation axis φ0 on the holding means 6 side is preferably fixed in a state perpendicular to the holding surface 6s.

  In the rough grinding, the rotation direction of the holding means 6 and the first grinding wheel 3b is the counterclockwise direction, but it may be rotated in the clockwise direction. Similarly, in the finish grinding, the rotation direction of the holding means 6 and the second grinding wheel 4b is clockwise, but it may be rotated counterclockwise.

DESCRIPTION OF SYMBOLS 1 Work processing apparatus 3 1st processing means 3a 1st grinding surface 3b 1st grinding wheel 3c 1st spindle part 4 2nd processing means 4a 2nd grinding surface 4b 2nd grinding wheel 4c 2nd Spindle part 6 Holding means 6s Holding surface 14 Control means 21 First grinding mark 23 Second grinding mark W Plate workpiece Wa Front surface Wb Back surface W1 Device region W2 Surplus region W3 Concave portion W4 Reinforcement portion φ0 Rotating shaft φ1 First Rotation axis φ2 second rotation axis α first inclination angle β second inclination angle

Claims (1)

Holding means having a holding surface that holds the plate-like workpiece and is driven to rotate about the rotation axis;
A first grinding wheel for rough grinding having a first grinding surface facing the holding surface, and a first rotation axis with the first grinding wheel as a vertical axis perpendicular to the first grinding surface First processing means having a first spindle part rotatably supported as:
A second grinding wheel for finish grinding having a second grinding surface facing the holding surface, and a second rotation axis with the second grinding wheel as a vertical axis perpendicular to the second grinding surface A second processing means having a second spindle part rotatably supported as:
The first grinding of a region on the back surface side corresponding to the device region of the plate-like workpiece having a device region having a device formed on the front surface side and a surplus region surrounding the device region. A workpiece processing method for forming a ring-shaped reinforcing portion on the back side corresponding to the surplus region by sequentially grinding by a surface and the second grinding surface,
A holding step of holding the surface side of the plate-like workpiece on the holding surface;
With respect to the back surface side of the plate-like workpiece held on the holding surface, the first rotating shaft is slightly inclined relative to the rotating shaft by a first inclination angle. A first machining step in which rough grinding is performed by positioning the first grinding surface so that an outer peripheral edge of one grinding wheel passes through the inside of a region corresponding to the surplus region and the center of the plate-like workpiece; ,
The first machining is held on the holding surface in a state where the second rotation shaft is slightly inclined relative to the rotation shaft by a second inclination angle smaller than the first inclination angle. Second grinding is performed so that the outer peripheral edge of the second grinding wheel passes through the inside of the region corresponding to the surplus region and the center of the plate-like workpiece with respect to the back surface side of the plate-like workpiece that has been processed. A second machining step in which the surface is positioned and finish grinding is performed;
Only including,
The workpiece machining method , wherein the first inclination angle is set to an angle larger than the particle diameter of the first grinding wheel .

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