JP2023177697A - Grinding method of workpiece - Google Patents

Abstract

To provide a grinding method of a workpiece which can inhibit occurrence of chips at an outer periphery part of the workpiece.SOLUTION: A grinding method of a workpiece includes: a holding step 101 in which a workpiece is held on a holding table; a center part grinding step 102 in which a center part of the workpiece is ground to a predetermined thickness to form a recessed part with a first grinding wheel having an outer diameter smaller than that of the workpiece; and an outer periphery part grinding step 103 in which the first grinding wheel is relatively moved from the recessed part to an outer periphery area of a holding surface of the holding table to grind an outer periphery part of the workpiece surrounding the recessed part after the center part grinding step 102 is performed.SELECTED DRAWING: Figure 2

Description

The present invention relates to a method for grinding a workpiece.

When grinding a warped workpiece, it has been thought that in conventional processing methods, it is necessary to first adsorb the workpiece to a holding table. Therefore, in order to attract the workpiece to the holding table, a mechanism for pressing the outer circumference of the workpiece against the holding table is provided on the transfer arm (for example, see Patent Document 1), and a pump is increased to increase the suction force of the holding table. The suction path on the holding surface is divided into the center and the outer periphery, so that even if the outer periphery lifts off the holding surface, the center will not leak, and the outer periphery can be vacuumed by pushing the outer periphery with a transfer arm. Solutions have been taken, such as creating dedicated vacuum paths.

JP 2019-123047 Publication

In addition, in recent years, workpieces with large warpage have occurred, and cases have also arisen in which the entire surface of the workpiece cannot be suctioned even if the conveyance or holding surface is devised.

If grinding were to proceed while the outer periphery was floating and the grinding wheel hit the outer periphery, there was a risk that the outer periphery would be chipped.

An object of the present invention is to provide a method for grinding a workpiece that can suppress the occurrence of chipping on the outer periphery of the workpiece.

In order to solve the above-mentioned problems and achieve the objects, the present invention provides a method for grinding a workpiece, which comprises: a holding step for holding the workpiece on a holding table; and a holding step for holding the workpiece on a holding table; a center part grinding step of grinding the center part of the workpiece to a predetermined thickness to form a concave part using a first grinding wheel having a smaller diameter than the workpiece; and after performing the center part grinding step, the first grinding wheel The method is characterized by comprising an outer peripheral part grinding step of relatively moving the material from the recess to an outer peripheral area of the holding surface of the holding table and grinding the outer peripheral part of the workpiece surrounding the recess.

In the method for grinding a workpiece, the holding table includes a holding surface partitioned into an outer peripheral area for holding the outer peripheral part and a central area for holding the central part, the outer peripheral area and the central area. and a suction path that connects each independently to a suction source, and the holding step may generate a suction force in the central region to hold the central portion of the workpiece.

In the method for grinding the workpiece, the central portion grinding step and the outer peripheral portion grinding step may be repeatedly performed.

In the method for grinding the workpiece, at a predetermined timing after starting the outer circumferential grinding step, while maintaining the suction force in the central area, a suction force is further generated in the outer circumferential area so that the workpiece is thinned. an outer periphery adsorption step of adsorbing the outer periphery of the workpiece to the outer periphery area; and after performing the outer periphery adsorption step, the outer periphery of the workpiece is covered with the first grinding wheel or a second grinding wheel different from the first grinding wheel; and a full-surface grinding step of grinding the entire surface of the workpiece and thinning the workpiece to a desired final thickness.

In the method for grinding a workpiece, the first grinding wheel may have a smaller outer diameter than the central region.

In the method for grinding a workpiece, the second grinding wheel used in the entire surface grinding step may have a larger outer diameter than the first grinding wheel.

The present invention has the effect of being able to suppress the occurrence of chipping on the outer peripheral portion of the workpiece.

FIG. 1 is a perspective view showing a configuration example of a workpiece to be processed by a method for grinding a workpiece according to a first embodiment. FIG. 2 is a flowchart showing the flow of the method for grinding a workpiece according to the first embodiment. FIG. 3 is a side view schematically showing, partially in section, the holding step of the method for grinding the workpiece shown in FIG. FIG. 4 is a side view schematically showing, partially in cross section, the central part grinding step of the method for grinding the workpiece shown in FIG. FIG. 5 is a side view schematically showing, in partial cross section, immediately after the start of the outer circumference grinding step of the method for grinding the workpiece shown in FIG. FIG. 6 is a side view schematically showing, in partial cross section, immediately before the end of the outer circumference grinding step of the method for grinding the workpiece shown in FIG. FIG. 7 is a flowchart showing the flow of a method for grinding a workpiece according to the second embodiment. FIG. 8 is a side view schematically showing, in partial cross section, immediately before the end of the first outer circumference grinding step of the method for grinding the workpiece shown in FIG. FIG. 9 is a side view schematically showing, partially in cross section, the retraction step of the method for grinding the workpiece shown in FIG. FIG. 10 is a side view schematically showing a central part grinding preparation step of the method for grinding the workpiece shown in FIG. 7, with a partial cross section. FIG. 11 is a flowchart showing the flow of the method for grinding a workpiece according to the third embodiment. FIG. 12 is a side view schematically showing, partially in cross section, the outer periphery suction step of the method for grinding the workpiece shown in FIG. FIG. 13 is a side view schematically showing, in partial cross section, the entire surface grinding step of the method for grinding the workpiece shown in FIG. FIG. 14 is a side view schematically showing, partially in cross section, a holding step of a method for grinding a workpiece according to a modification of Embodiment 1, Embodiment 2, and Embodiment 3.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Modes (embodiments) for carrying out the present invention will be described in detail with reference to the drawings. The present invention is not limited to the contents described in the following embodiments. Further, the constituent elements described below include those that can be easily assumed by those skilled in the art and those that are substantially the same. Furthermore, the configurations described below can be combined as appropriate. Further, various omissions, substitutions, or changes in the configuration can be made without departing from the gist of the present invention.

[Embodiment 1]
A method for grinding a workpiece according to Embodiment 1 of the present invention will be described based on the drawings. FIG. 1 is a perspective view showing a configuration example of a workpiece to be processed by a method for grinding a workpiece according to a first embodiment. FIG. 2 is a flowchart showing the flow of the method for grinding a workpiece according to the first embodiment.

(Workpiece)
The method for grinding a workpiece according to the first embodiment is a method for grinding a workpiece 1 shown in FIG. The workpiece 1 to be processed in the workpiece grinding method according to the first embodiment is a disk-shaped semiconductor wafer or an optical device whose substrate 2 is silicon, sapphire, gallium arsenide, SiC (silicon carbide), or the like. Such as wafers. As shown in FIG. 1, the workpiece 1 has a plurality of dividing lines 4 that intersect with each other on the surface 3, and devices 5 are formed in areas partitioned by the dividing lines 4.

The device 5 is, for example, an integrated circuit such as an IC (Integrated Circuit) or an LSI (Large Scale Integration), an image sensor such as a CCD (Charge Coupled Device), or a CMOS (Complementary Metal Oxide Semiconductor), or a memory (semiconductor storage device). ).

Further, in the first embodiment, the workpiece 1 includes a central portion 8 and an outer circumferential portion 9 on the outer circumferential side of the central portion 8, and the outer circumferential portion 9 is more warped in the thickness direction than the central portion 8 ( Note that FIG. 1 omits the warping of the workpiece 1). Note that the central portion 8 is a region including the center of the workpiece 1 in plan view, and the outer peripheral portion 9 is a region on the outer peripheral side of the central portion 8 and including the outer edge of the workpiece 1. Note that the device 5 may be formed on the surface 3 of the outer peripheral portion 9, or the device 5 may not be formed on the surface 3.

In Embodiment 1, the workpiece 1 is the aforementioned wafer, but in the present invention, it is not limited to the wafer, but may include, for example, a substrate on which a plurality of device chips are arranged, and a plurality of device chips on the substrate. Various workpieces may be used, such as a package substrate with a molded resin sealed with a mold. Further, in the present invention, the workpiece 1 may be a wafer in which the device 5 is not formed on the surface 3.

(Grinding method of workpiece)
The method of grinding a workpiece according to the first embodiment is a method of thinning the workpiece 1 to a desired final thickness 6 by grinding the back surface 7 on the back side of the front surface 3 of the workpiece 1. As shown in FIG. 2, the method for grinding a workpiece includes a holding step 101, a center grinding step 102, and an outer peripheral grinding step 103.

(holding step)
FIG. 3 is a side view schematically showing, partially in section, the holding step of the method for grinding the workpiece shown in FIG. The holding step 101 is a step of holding the workpiece 1 on the holding surface 25 of the holding table 21 of the grinding device 20 . Note that the holding table 21 includes a disc-shaped porous member 22 and a frame 23 provided with a circular recess 24 in the center of which the porous member 22 is fitted and attached.

The porous member 22 is made of a porous material such as porous ceramic. The upper surface of the porous member 22 is a holding surface 25 that is formed flat along the horizontal direction and holds the workpiece 1 . Further, in the holding table 21, a holding surface 25, which is the upper surface of the porous member 22, and the upper surface of the frame body 23 are arranged on the same plane.

Further, in the first embodiment, the holding surface 25 of the holding table 21 is divided into an outer peripheral area 251 that holds the outer peripheral part 9 of the workpiece 1 and a central area 252 that holds the central part 8 of the workpiece 1. ing. In the first embodiment, the holding table 21 is made of porous ceramic having lower air permeability than other parts of the porous member 22, non-porous resin, or non-porous material between the outer peripheral area 251 and the central area 252. A partition wall member 26 made of glass or the like is embedded within the porous member 22, and the holding surface 25 is divided into an outer peripheral region 251 and a central region 252. In this way, the holding table 21 has a holding surface 25 divided into an outer peripheral area 251 and a central area 252.

Further, the holding table 21 has suction paths 27 and 28 that independently connect the outer peripheral area 251 of the holding surface 25 and the central area 252 of the holding surface 25 to the suction source 29. Each suction path 27, 28 is provided with an on-off valve 271, 281. The suction path 27 opens at a position on the bottom surface of the recess 24 on the outer periphery side of the partition member 26, and the suction path 28 opens on the bottom surface of the recess 24 at a position on the inner periphery side of the partition wall member 26. .

In the first embodiment, in the holding step 101 , the workpiece 1 having the support member 10 attached to the surface 3 is placed on the holding surface 25 of the holding table 21 of the grinding device 20 . At this time, the outer peripheral portion 9 of the workpiece 1 is located on the outer peripheral region 251, and the center portion 8 of the workpiece 1 is located on the central region 252. In the first embodiment, in the holding step 101, the grinding device 20 opens the on-off valve 281 with the on-off valve 271 closed, and applies only the central area 252 of the outer peripheral area 251 and the central area 252 of the holding surface 25. A suction force is generated to suction and hold the central portion 8 of the workpiece 1 in the central region 252 .

In Embodiment 1, the support member 10 is an adhesive tape having a base material layer having flexibility and non-adhesiveness, and an adhesive layer laminated on the base material layer and having flexibility and adhesiveness. However, the present invention is not limited to adhesive tapes. In the present invention, the support member 10 may be a sheet made of thermoplastic resin without an adhesive layer. In the case of a non-adhesive sheet, the support member 10 is preferably a polyolefin sheet, a polyethylene sheet, a polypropylene sheet, or a polystyrene sheet, and is adhered to the workpiece 1 by thermocompression bonding.

(Central grinding step)
FIG. 4 is a side view schematically showing, partially in cross section, the central part grinding step of the method for grinding the workpiece shown in FIG. In the center part grinding step 102, the center part 8 of the workpiece 1 is ground to a predetermined thickness using a first grinding wheel 30 whose outer diameter is smaller than the outer diameter of the workpiece 1, and a recess 11 is partially formed on the back surface 7. This is the step of forming.

In the first embodiment, the first grinding wheel 30 has an outer diameter smaller than the outer diameter of the workpiece 1. It includes a disc-shaped wheel base 31 smaller than the outer diameter of the central region 252 of the workpiece 1, and a plurality of grinding wheels 32 provided on the outer edge of the wheel base 31. In this way, the first grinding wheel 30 has the diameter of the circle formed by the outer edges of the plurality of grinding wheels 32 (corresponding to the outer diameter of the first grinding wheel 30) equal to the outer diameter of the workpiece 1 and the outer diameter of the workpiece 1. It is smaller than the outer diameter of the central region 252 of the workpiece 1. The central region 252 holds the central portion 8 of the workpiece 1, but since the central portion 8 has less warp than the outer circumferential portion 9, it is held by the holding surface 25 under suction. Since the outer diameter of the first grinding wheel 30 is smaller than the central area 252, it is possible to grind only the area sucked and held by the holding surface 25, so that the workpiece 1 is warped and floats from the holding surface 25. There is no risk that the first grinding wheel 30 will collide with the part where the workpiece 1 is being processed and the workpiece 1 will be damaged.

Further, in the first embodiment, the outer diameter of the first grinding wheel 30 is larger than the radius of the center portion 8 of the workpiece 1. In addition, in the present invention, the purpose is not to grind the outer peripheral part 9 that is warped and floating from the holding surface 25, but to first grind the central part 8 that is sucked and held by the holding surface 25, so the first grinding It is preferable that the outer diameter of the wheel 30 is less than or equal to the outer diameter of the central region 252 of the workpiece 1, but the warpage around the central region 252 is also small, so that the workpiece 1 can be held even if it is not held by suction. Since it may be possible to grind without causing damage, it is sufficient that the diameter is smaller than the outer diameter of the workpiece 1. Further, in the present invention, the outer diameter of the first grinding wheel 30 may be limited to the radius of the central portion 8 of the workpiece 1.

In the first embodiment, in the center grinding step 102, the grinding device 20 aligns the axial center of the holding table 21 and the axial center 34 of the spindle 33, on which the first grinding wheel 30 is attached to the lower end, to be parallel to each other and spaced apart from each other. At the same time, the grinding wheel 32 of the first grinding wheel 30 is positioned above the center part 8 of the back surface 7 of the workpiece 1 held on the holding table 21. In the first embodiment, in the center grinding step 102, the grinding device 20 rotates the workpiece 1 while rotating the first grinding wheel 30 about the axis 34 while rotating the holding table 21 about the axis. The first grinding wheel 30 is moved downward while supplying grinding water.

In the first embodiment, in the central part grinding step 102, the grinding device 20, as shown in FIG. By approaching the workpiece 1, the grinding wheel 32 grinds the back surface 7 of the workpiece 1. In the first embodiment, in the central part grinding step 102, the grinding device 20 grinds and thins the central part 8 of the workpiece 1 to a final thickness 6, and partially forms a recess 11 in the back surface 7 of the workpiece 1. Form. In the first embodiment, since the outer diameter of the first grinding wheel 30 is larger than the radius of the center part 8 of the workpiece 1, the vicinity of the axis of the center part 8 of the back surface 7 of the workpiece 1 is not ground. A recess 11 is formed in an annular shape.

(Outer periphery grinding step)
FIG. 5 is a side view schematically showing, in partial cross section, immediately after the start of the outer circumference grinding step of the method for grinding the workpiece shown in FIG. FIG. 6 is a side view schematically showing, in partial cross section, immediately before the end of the outer circumference grinding step of the method for grinding the workpiece shown in FIG. In the outer peripheral grinding step 103, after the center grinding step 102 is performed, the first grinding wheel 30 is moved relatively from the recess 11 to the outer peripheral area 251 of the holding surface 25 of the holding table 21, and the cover surrounding the recess 11 is removed. This is a step of grinding the outer peripheral portion 9 of the workpiece 1.

In the first embodiment, in the outer peripheral part grinding step 103, as shown in FIG. 5, the grinding device 20 performs the first The grinding wheel 30 is moved relative to the holding table 21 toward the outer peripheral area 251 of the holding surface 25 of the holding table 21 along the holding surface 25, and the outer peripheral part 9 of the workpiece 1 is moved into the recess 11. Grind from the inside side. In the outer periphery grinding step 103, the first grinding wheel 30 performs the grinding while moving, thereby also removing an unground area near the axis of the central portion 8 of the workpiece 1 shown in FIG. In the outer peripheral grinding step 103, as finally shown in FIG. 6, the grinding wheel 32 of the first grinding wheel 30 is moved and positioned relative to the holding surface 25 to the outer edge of the workpiece 1, The outer peripheral portion 9 of the workpiece 1 is thinned to a final thickness 6.

In the first embodiment, in the outer circumference grinding step 103, the grinding device 20 relatively moves the first grinding wheel 30 by 50 mm toward the outer circumference region 251 of the holding surface 25 of the holding table 21.

In the method for grinding a workpiece according to the first embodiment described above, after forming the recess 11 in the center part 8 of the back surface 7 of the workpiece 1 in the center part grinding step 102, the recess 11 is formed in the outer peripheral part grinding step 103. Since the inner surface is ground toward the outer edge of the workpiece 1, even if the outer peripheral part 9 of the workpiece 1 is floating from the holding surface 25, the first grinding wheel 30 is pressed against the inner surface of the recess 11. The outer circumferential portion 9 is ground while being pressed against the holding surface 25 with the grinding wheel 30 . For this reason, in the method for grinding a workpiece according to the first embodiment, even if the outer circumference 9 of the workpiece 1 is floating from the holding surface 25, the first grinding wheel is attached to the outer circumference 9 of the workpiece 1. 30 can be prevented from colliding, and chipping of the outer peripheral portion 9 can be prevented.

As a result, the method for grinding a workpiece according to the first embodiment has the effect of suppressing the occurrence of chipping in the outer peripheral portion 9 of the workpiece 1.

[Embodiment 2]
A method for grinding a workpiece according to Embodiment 2 of the present invention will be described based on the drawings. FIG. 7 is a flowchart showing the flow of a method for grinding a workpiece according to the second embodiment. FIG. 8 is a side view schematically showing, in partial cross section, immediately before the end of the first outer circumference grinding step of the method for grinding the workpiece shown in FIG. FIG. 9 is a side view schematically showing, partially in cross section, the retraction step of the method for grinding the workpiece shown in FIG. FIG. 10 is a side view schematically showing a central part grinding preparation step of the method for grinding the workpiece shown in FIG. 7, with a partial cross section. In addition, in FIGS. 7, 8, 9, and 10, the same parts as in the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted.

The method for grinding a workpiece according to the second embodiment includes grinding the center part 8 of the workpiece 1 to a predetermined thickness 12 (shown in FIG. 8) which is thicker than the final thickness 6 in the first center part grinding step 102, and 7, the central part grinding step 102 and the outer peripheral part grinding step 103 are repeated multiple times to gradually thin the entire surface of the workpiece 1 to a final thickness of 6, and the retreat step 105 and the central part grinding preparation step 106 are the same as in the first embodiment.

In the method for grinding a workpiece according to the second embodiment, the grinding device 20 grinds the center part 8 of the workpiece 1 to a predetermined thickness 12 that is thicker than the final thickness 6 in the first center part grinding step 102, and In the outer peripheral grinding step 103, the first grinding wheel 30 is moved against the holding table 21 while maintaining the distance from the holding surface 25 of the grinding wheel 32 at the end of the first central grinding step 102. The outer circumferential portion 9 of the workpiece 1 is ground from the inner surface side of the recess 11 by relatively moving along the holding surface 25 toward the outer circumferential region 251 of the holding surface 25 . In the second embodiment, in the outer peripheral grinding step 103, as shown in FIG. It is determined whether the thickness has been reduced to a final thickness of 6 (step 104). In the second embodiment, when the grinding device 20 determines that the workpiece 1 has not been thinned to the final thickness 6 (step 104: No), the process proceeds to a retreat step 105.

In the second embodiment, the retreat step 105 is a step of raising the first grinding wheel 30 so that the grinding wheel 32 does not hit the workpiece 1, that is, is located above the back surface 7 of the workpiece 1. It is. In the second embodiment, in the retreat step 105, the grinding device 20 raises the first grinding wheel 30 relative to the holding table 21, as shown in FIG.

In the second embodiment, the central part grinding preparation step 106 is a step of positioning the first grinding wheel 30 above the central part 8 of the back surface 7 of the workpiece 1 . In the second embodiment, in the central part grinding preparation step 106, as shown in FIG. 10, the grinding device 20 moves the first grinding wheel 30 relative to the holding table 21 along the holding surface 25, The first grinding wheel 30 is positioned above the center part 8 of the back surface 7 of the workpiece 1 held on the holding table 21, and the process returns to the center part grinding step 102.

In the second embodiment, the grinding device 20 thins the center portion 8 of the workpiece 1 by a predetermined distance, such as 10 μm or 100 μm, each time the center portion grinding step 102 is performed, and the outer peripheral portion grinding step 103 is also performed once. , the central portion is thinned by a predetermined distance in the same manner as in the center grinding step 102. Further, in the second embodiment, after the outer peripheral portion grinding step 103, when the grinding device 20 determines that the workpiece 1 has been thinned to the final thickness 6 (step 104: Yes), the process ends. In this manner, in the second embodiment, the central portion grinding step 102 and the outer peripheral portion grinding step 103 are repeatedly performed until the thickness of the workpiece 1 reaches the final thickness 6.

In the method for grinding a workpiece according to the second embodiment, after forming a recess 11 in the center part 8 of the back surface 7 of the workpiece 1 in a central part grinding step 102, the inner surface of the recess 11 is covered in an outer peripheral part grinding step 103. Since grinding is performed toward the outer edge of the workpiece 1, collision of the first grinding wheel 30 with the outer circumference 9 of the workpiece 1 can be suppressed, and chipping of the outer circumference 9 can be suppressed. As a result, the method for grinding a workpiece according to the second embodiment has the effect of suppressing the occurrence of chipping in the outer peripheral portion 9 of the workpiece 1, similarly to the first embodiment.

[Embodiment 3]
A method for grinding a workpiece according to Embodiment 3 of the present invention will be described based on the drawings. FIG. 11 is a flowchart showing the flow of the method for grinding a workpiece according to the third embodiment. FIG. 12 is a side view schematically showing, partially in cross section, the outer periphery suction step of the method for grinding the workpiece shown in FIG. FIG. 13 is a side view schematically showing, in partial cross section, the entire surface grinding step of the method for grinding the workpiece shown in FIG. Note that in FIGS. 11, 12, and 13, the same parts as in the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted.

The method for grinding a workpiece according to Embodiment 3 includes grinding the center part 8 of the workpiece 1 to a first stage finishing thickness 13 (shown in FIG. 12) which is thicker than the final thickness 6 in a center part grinding step 102; As shown in FIG. 11, this is the same as the first embodiment except that it includes an outer periphery adsorption step 107 and a full surface grinding step 108 that are performed after the outer periphery grinding step 103.

In the method for grinding a workpiece according to the third embodiment, the grinding device 20 grinds the center part 8 of the workpiece 1 in the center part grinding step 102 to a first-stage finishing thickness 13 that is thicker than the final thickness 6, and grinds the outer periphery. In the center grinding step 103, the first grinding wheel 30 is moved against the holding surface 25 of the holding table 21 while maintaining the distance from the holding surface 25 of the grinding wheel 32 at the end of the center grinding step 102. The outer circumferential portion 9 of the workpiece 1 is ground from the inner surface side of the recess 11 by relatively moving along the holding surface 25 toward the outer circumferential region 251 . Note that the first stage finishing thickness 13 is the thickness of the workpiece 1 at which the outer circumferential portion 9 is thinned, the warping is alleviated, and the outer circumferential portion 9 can be sucked and held in the outer circumferential region 251 of the holding table 21. be.

In the third embodiment, the outer periphery suction step 107 further generates a suction force in the outer periphery area 251 while maintaining the suction force in the central area 252 at a predetermined timing after starting the outer periphery grinding step 103, thereby removing the thin layer. This is a step in which the outer circumferential portion 9 of the processed workpiece 1 is attracted to the outer circumferential region 251. In the third embodiment, in the outer periphery adsorption step 107, after the outer periphery grinding step 103 is completed at a predetermined timing, the grinding device 20 opens the on-off valve 281 and opens the on-off valve 271 to suck the outer periphery of the holding surface 25. A suction force is generated at 251 to suction and hold the outer circumferential portion 9 of the workpiece 1 in the outer circumferential region 251, as shown in FIG.

In the third embodiment, the entire surface grinding step 108 includes grinding the entire back surface 7 of the workpiece 1 with a second grinding wheel 40 different from the first grinding wheel 30 after the outer circumferential suction step 107 is performed. 1 to a desired final thickness 6. The second grinding wheel 40 includes a disc-shaped wheel base 41 whose radius is larger than the radius of the workpiece 1, and a plurality of grinding wheels 42 provided on the outer edge of the wheel base 41. Thus, in the second grinding wheel 40, the radius of the circle formed by the outer edges of the plurality of grinding wheels 42 (corresponding to the radius of the second grinding wheel 40) is larger than the radius of the workpiece 1.

In the third embodiment, in the entire surface grinding step 108, the grinding device 20 makes the axial center of the holding table 21 and the axial center 44 of the spindle 43, on which the second grinding wheel 40 is mounted at the lower end, parallel to each other and spaced apart from each other. At the same time, the grinding wheel 42 of the second grinding wheel 40 is positioned above the center portion 8 of the back surface 7 of the workpiece 1 held on the holding table 21 . In the third embodiment, in the entire surface grinding step 108, the grinding device 20 grinds the workpiece 1 while rotating the second grinding wheel 40 about the axis while rotating the holding table 21 about the axis. By moving the second grinding wheel 40 downward while supplying water, the entire back surface 7 of the workpiece 1 is ground.

In the third embodiment, in the entire surface grinding step 108, the grinding device 20 holds the plurality of grinding wheels 42 provided on the outer edge of the wheel base 41 of the second grinding wheel 40 on the holding table 21, as shown in FIG. By approaching the grinding wheel 42 at a predetermined feed rate, the entire back surface 7 of the workpiece 1 is ground with the grinding wheel 42. Note that in the present invention, although the grinding time takes longer than in the third embodiment, the grinding device 20 may grind the entire back surface 7 of the workpiece 1 with the first grinding wheel 30 in the entire surface grinding step 108. .

In the method for grinding a workpiece according to the third embodiment, after forming a recess 11 in the center part 8 of the back surface 7 of the workpiece 1 in a center part grinding step 102, the inner surface of the recess 11 is covered in an outer peripheral part grinding step 103. Since grinding is performed toward the outer edge of the workpiece 1, collision of the first grinding wheel 30 with the outer circumference 9 of the workpiece 1 can be suppressed, and chipping of the outer circumference 9 can be suppressed. As a result, the method for grinding a workpiece according to the third embodiment has the effect of suppressing the occurrence of chipping in the outer peripheral portion 9 of the workpiece 1, similarly to the first embodiment. In addition, in the third embodiment, the second grinding wheel 40 having a radius greater than or equal to the radius of the workpiece 1 performs the entire surface grinding, thereby moving the holding surface 25 and the second grinding wheel 40 relatively. You can grind the entire surface without having to do so. Therefore, compared to grinding the entire surface of the workpiece 1 to the final thickness 6 using the first grinding wheel 30 whose outer diameter is smaller than the radius of the workpiece 1, the grinding time can be reduced.

In addition, in the present invention, in the third embodiment, the grinding device 20 grinds the center part 8 of the workpiece 1 to a predetermined thickness 12 that is thicker than the first stage finishing thickness 13 in the first center part grinding step 102. Similarly to the second embodiment, the central part grinding step 102 and the outer peripheral part grinding step 103 may be repeated multiple times.

Further, in the present invention, in Embodiments 1 to 3, the outer periphery suction step 107 may be performed during the outer periphery grinding step 103 (corresponding to a predetermined timing). In particular, in the present invention, when repeating the central part grinding step 102 and the outer peripheral part grinding step 103 multiple times, the outer peripheral adsorption step 107 is performed after performing these a predetermined number of times (corresponding to a predetermined timing). You may do so.

[Modified example]
A method for grinding a workpiece according to a modification of Embodiment 1, Embodiment 2, and Embodiment 3 of the present invention will be described based on the drawings. FIG. 14 is a side view schematically showing, partially in cross section, a holding step of a method for grinding a workpiece according to a modification of Embodiment 1, Embodiment 2, and Embodiment 3. In addition, in FIG. 14, the same parts as in Embodiment 1 are given the same reference numerals, and the description thereof will be omitted.

In the method of grinding a workpiece according to the modified example, the holding table 21 has no partition wall member 26 embedded in the porous member 22, and the holding surface 25 is not divided into a central region 252 and an outer peripheral region 251. , is the same as the first embodiment except that only one suction path 28-1 connecting the holding surface 25 and the suction source 29 is provided. The suction path 28-1 is provided with an on-off valve 281-1.

In the modification, in the holding step 101 , the workpiece 1 with the support member 10 attached to the surface 3 is placed on the holding surface 25 of the holding table 21 of the grinding device 20 . At this time, similarly to Embodiment 1, the outer peripheral portion 9 of the workpiece 1 is located on the outer peripheral region 251, and the center portion 8 of the workpiece 1 is located on the central region 252. In the first embodiment, in the holding step 101, the grinding device 20 opens the on-off valve 281-1 to generate a suction force on the entire holding surface 25, and in the case of a warped workpiece 1, as shown in FIG. Then, the central portion 8 is held in the central region 252 by suction. In addition, in a modification, when carrying out the whole surface grinding step 108 like Embodiment 3, the outer periphery suction step 107 is not carried out.

In the method for grinding a workpiece according to the modified example, after forming a recess 11 in the center part 8 of the back surface 7 of the workpiece 1 in a central part grinding step 102, the inner surface of the recess 11 is processed in an outer peripheral part grinding step 103. Since the object 1 is ground toward the outer edge, it is possible to prevent the first grinding wheel 30 from colliding with the outer circumferential portion 9 of the workpiece 1, and to prevent the outer circumferential portion 9 from chipping. As a result, the method for grinding a workpiece according to the modified example has the effect of suppressing the occurrence of chipping in the outer peripheral portion 9 of the workpiece 1, as in the first embodiment.

In addition, in the method for grinding a workpiece according to the modified example, suction force is generated on the entire holding surface 25 in the holding step 101, so when the outer circumferential portion 9 is ground in the outer circumferential portion grinding step 103 to alleviate the warp, the holding surface 25 Also, the outer peripheral portion 9 of the workpiece 1 can be held by suction. As a result, the method for grinding a workpiece according to the modified example can prevent the first grinding wheel 30 from colliding with the outer circumference 9 of the workpiece 1, and can suppress chipping of the outer circumference 9. .

Note that although the embodiment of the present invention has been described with reference to a warped workpiece 1, the present invention is also effective for a workpiece 1 that is not warped. This is not limited to warping of the workpiece 1, but the outer edge of the workpiece 1 is usually chamfered into a rounded shape and is slightly lifted from the holding surface 25, which prevents grinding water from entering during grinding. The grinding wheel is likely to flutter due to collisions, and even if the workpiece 1 has had its chamfered portion removed in advance, the grinding wheel will collide with it from the outer periphery, causing the workpiece to start from the outer periphery. This is because there is a risk that chipping may occur in 1. Therefore, in the present invention, in which a recess 11 is formed in the center part 8 of the workpiece 1 and the grinding wheel is applied to the inner surface of the recess 11 to widen the grinding area and grind the outer peripheral part 9, the grinding wheel does not come into contact with the outer peripheral part 9. This is because it is possible to prevent the workpiece 1 from being damaged starting from the outer peripheral portion 9 where the holding force is unstable. Note that the present invention is not limited to the above embodiments. That is, various modifications can be made without departing from the gist of the invention.

1 Workpiece 6 Final thickness (predetermined thickness)
8 Central part 9 Peripheral part 11 Recessed part 12 Predetermined thickness 21 Holding table 25 Holding surface 27, 28 Suction path 29 Suction source 30 First grinding wheel 40 Second grinding wheel 101 Holding step 102 Central part grinding step 103 Outer peripheral part grinding step 107 Outer periphery suction step 108 Full surface grinding step 251 Outer periphery area 252 Central area

Claims (6)

A method for grinding a workpiece, the method comprising:
a holding step for holding the workpiece on a holding table;
a center part grinding step of grinding the center part of the workpiece to a predetermined thickness using a first grinding wheel having an outer diameter smaller than the workpiece to form a recess;
After performing the central part grinding step, the first grinding wheel is moved from the recess relatively to the outer peripheral area of the holding surface of the holding table to grind the outer peripheral part of the workpiece surrounding the recess. part grinding step;
A method for grinding a workpiece, comprising: The holding table is
a holding surface partitioned into an outer peripheral area that holds the outer peripheral part and a central area that holds the central part;
a suction path that independently connects the outer peripheral region and the central region to a suction source;
2. The method of grinding a workpiece according to claim 1, wherein the holding step includes generating a suction force in the central region to hold the central portion of the workpiece. 2. The method of grinding a workpiece according to claim 1, wherein the central portion grinding step and the outer peripheral portion grinding step are repeatedly performed. At a predetermined timing after starting the outer periphery grinding step, while maintaining the suction force in the central area, a suction force is further generated in the outer periphery to grind the thinned outer periphery of the workpiece. an outer periphery adsorption step of adhering to the outer periphery area;
After performing the outer circumferential suction step, the entire surface of the workpiece is ground with the first grinding wheel or a second grinding wheel different from the first grinding wheel, and the workpiece is thinned to a desired final thickness. Full-face grinding step,
The method for grinding a workpiece according to claim 2, further comprising: 3. The method of grinding a workpiece according to claim 2, wherein the first grinding wheel has a smaller outer diameter than the central region. 5. The method of grinding a workpiece according to claim 4, wherein the second grinding wheel used in the entire surface grinding step has a larger outer diameter than the first grinding wheel.

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