Work-piece processing method

Abstract

To provide a work-piece processing method in which an effective region usable for a product can be sufficiently ensured without requiring a significantly longer time than a conventional method when forming a thin plate part and a thick plate part by grinding a disc-shaped work-piece.SOLUTION: A work-piece processing method includes: a cut groove formation step at which a disc-shaped first grinding planned part that is positioned on a center side with respect to a cut groove and an annular thick plate part that is positioned on an outer peripheral side with respect to the cut groove are formed by forming the cut groove in a work-piece; a first grinding step at which after the cut groove formation step, a disk-shaped second grinding planned part thinner than the first grinding planned part is formed by grinding the first grinding planned part by using a first grindstone; and a second grinding step at which a disk-like thin plate part thinner than the second grinding planned part is formed by grinding the second grinding planned by using a second grindstone that contains smaller abrasive grains compared to the first grindstone.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a method for processing a workpiece, which is applied when processing a plate-like workpiece such as a wafer. [Background technology]

[0002] In order to realize small and lightweight device chips, there are increasing opportunities to thin wafers on which devices such as integrated circuits are provided on the front side. For example, the front side of the wafer is held by a chuck table, and a grinding wheel with a grinding wheel containing abrasive grains fixed thereto and the chuck table are rotated relative to each other, and the grinding wheel is pressed against the back side of the wafer while supplying liquid such as pure water, thereby grinding the wafer to make it thinner.

[0003] However, when the entire wafer is thinned by the above-mentioned method, the rigidity of the wafer is also significantly reduced, making it difficult to handle the wafer in the subsequent steps. Therefore, a technique has been proposed in which a grinding wheel with a diameter smaller than the radius of the wafer is used to grind the central (inner) region of the wafer on which the devices are provided from the backside, and the outer edge (outer) region is left as it is without being ground, thereby maintaining high rigidity of the wafer after grinding (see, for example, Patent Document 1).

[0004] In this technique, first, the central region of the wafer is roughly ground with a grinding wheel having a grinding stone containing relatively large abrasive grains attached thereto, forming a disk-shaped thin plate portion and an annular thick plate portion surrounding the thin plate portion on the wafer. In this way, the use of a grinding wheel having a grinding stone containing large abrasive grains attached thereto shortens the time required to grind the wafer compared to the use of a grinding wheel having a grinding stone containing small abrasive grains attached thereto.

[0005] On the other hand, when a wafer is roughly ground using a grinding wheel with a grinding stone containing large abrasive grains, a damage layer containing scratches and distortions caused by the grinding stone is formed on the ground surface, and the mechanical strength (transverse strength, etc.) of the thin plate portion is likely to be insufficient. Therefore, after the wafer is roughly ground, the damage layer is removed by further grinding the thin plate portion using a grinding wheel with a grinding stone containing relatively small abrasive grains. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2007-19461 A Summary of the Invention [Problem to be solved by the invention]

[0007] However, when the damaged layer is removed by further grinding the thin plate portion, if the grinding wheel comes into contact with the inner side of the thick plate portion, the thick plate portion may be chipped. Therefore, when removing the damaged layer, only the central area of ​​the thin plate portion is ground so that the grinding wheel does not come into contact with the thick plate portion. However, with this method, the damaged layer remains in the outer edge area of ​​the thin plate portion (the area close to the boundary with the thick plate portion), and the outer edge area of ​​the thin plate portion cannot be used for the product.

[0008] Therefore, an object of the present invention is to provide a method for processing a workpiece, which, when grinding a disk-shaped workpiece to form a thin plate portion and a thick plate portion, does not require a significantly longer time than conventional methods, and ensures a sufficient effective area that can be used for the product. [Means for solving the problem]

[0009] According to one aspect of the present invention, there is provided a method for processing a workpiece, the method being applicable when processing a workpiece having a circular first surface and a circular second surface opposite to the first surface to form a disk-shaped thin plate portion and an annular thick plate portion surrounding the thin plate portion and thicker than the thin plate portion, the method including: a cutting groove forming step of cutting an annular cutting blade into an annular portion of the second surface of the workpiece that is located closer to the center of the second surface than the outer periphery of the second surface and surrounding the center of the second surface while rotating the annular cutting blade, thereby forming a cutting groove in the annular portion of the workpiece, thereby forming a disk-shaped first portion to be ground that is located closer to the center than the cutting groove and the annular thick plate portion that is located closer to the outer periphery than the cutting groove; and a cutting groove forming step of grinding the workpiece with a plurality of first grinding wheels, each containing abrasive grains, after the cutting groove forming step. The present invention provides a method for processing a workpiece, the method including: a first grinding step of rotating a first grinding wheel arranged in a circular area having a diameter smaller than the radius of the workpiece and the workpiece to grind the first portion to be ground with a plurality of first grinding wheels to a depth that does not reach the bottom of the cutting groove, thereby forming a disk-shaped second portion to be ground that is thinner than the first portion to be ground; and a second grinding step of rotating a second grinding wheel arranged in a circular area having a diameter smaller than the radius of the workpiece and a plurality of second grinding wheels, each of which contains smaller abrasive grains than the abrasive grains contained in the first grinding wheels, to a depth that reaches the bottom of the cutting groove, thereby forming a disk-shaped thin plate portion that is thinner than the second portion to be ground.

[0010] Preferably, the width of the cut groove is 400 μm or more.

[0011] Preferably, in the second grinding step, when the second portion to be ground is ground from the second surface side, a part of the bottom of the cut groove is ground with the second grinding wheel. Effect of the Invention

[0012] In a method for processing a workpiece according to one aspect of the present invention, an annular cut groove that defines the inner edge of an annular thick plate portion is formed by cutting using a cutting blade that, in principle, is less likely to produce a damaged layer than grinding using a first grinding wheel. As a result, at least a damaged layer that would be produced when using the first grinding wheel is not produced at the bottom of the annular cut groove. Therefore, in the method for processing a workpiece according to one aspect of the present invention, the entire bottom of the annular groove can be treated as the effective area of ​​the disk-shaped thin plate portion that will be completed later.

[0013] In addition, the volume of the portion removed from the workpiece by the cutting blade when forming the annular cutting groove is significantly smaller than the volume of the portion removed from the workpiece by the first grinding wheel and the second grinding wheel. Therefore, the time required to form the annular groove is sufficiently shorter than the time required to complete grinding of the workpiece. In other words, in the method for processing a workpiece according to one aspect of the present invention, the time required to complete processing of the workpiece is not significantly longer than that in conventional methods.

[0014] Thus, according to the method for processing a workpiece according to one aspect of the present invention, when a disk-shaped workpiece is ground to form a thin plate portion and a thick plate portion, a sufficient effective area is secured for the product. Furthermore, according to the method for processing a workpiece according to one aspect of the present invention, the time required to complete grinding of the workpiece is not significantly longer than that required in conventional methods. [Brief description of the drawings]

[0015] [Figure 1] FIG. 1 is a perspective view that illustrates a state in which a protective member is attached to a workpiece. [Diagram 2] FIG. 2 is a flow diagram of the method for processing a workpiece according to this embodiment. [Diagram 3] FIG. 3 is a cross-sectional view that typically illustrates how the workpiece is cut in the cut groove forming step. [Figure 4] FIG. 4 is a cross-sectional view that illustrates a schematic view of a portion of the workpiece after the annular cut groove has been formed. [Diagram 5]FIG. 5 is a cross-sectional view that typically illustrates how the workpiece is ground in the first grinding step. [Figure 6] FIG. 6 is a cross-sectional view showing a schematic view of a part of the workpiece after rough grinding. [Figure 7] FIG. 7 is a cross-sectional view that typically illustrates how the workpiece is ground in the second grinding step. [Figure 8] FIG. 8 is a cross-sectional view that illustrates a part of the workpiece after finish grinding. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. First, a workpiece to be processed by a workpiece processing method according to the present embodiment will be described. Fig. 1 is a perspective view showing a state in which a protective member 21 is attached to a workpiece 11.

[0017] 1, the workpiece 11 is, for example, a disk-shaped wafer made of a semiconductor such as silicon (Si). That is, the workpiece 11 has a circular front surface (first surface) 11a and a circular back surface (second surface) 11b opposite the front surface 11a. The front surface 11a side of the workpiece 11 is divided into a plurality of small regions by a plurality of mutually intersecting streets (planned division lines) 13, and a device 15 such as an integrated circuit (IC) is formed in each small region.

[0018] In this embodiment, a portion of the workpiece 11 corresponding to an area (device area) 23 where the device 15 is formed is ground from the back surface 11b side to become thinner, while the remaining annular area (peripheral excess area) 25 is left as it is without being ground. In other words, the workpiece 11 is processed into a concave shape from the back surface 11b side.

[0019] In this embodiment, a disk-shaped wafer made of a semiconductor such as silicon is used as the workpiece 11, but the material, shape, structure, size, etc. of the workpiece 11 are not necessarily limited to this embodiment. For example, a substrate made of other materials such as semiconductors, ceramics, resins, metals, etc. may be used as the workpiece 11. Similarly, the type, number, shape, structure, size, arrangement, etc. of the devices 15 formed on the workpiece 11 are not limited to the above embodiment. The devices 15 do not have to be formed on the workpiece 11.

[0020] The protective member 21 attached to the workpiece 11 is typically a circular tape (film) having approximately the same diameter as the workpiece 11, a resin substrate, a wafer of the same or different type as the workpiece 11, etc. This protective member 21 has a circular front surface 21a and a circular back surface 21b opposite to the front surface 21a.

[0021] For example, an adhesive layer exhibiting adhesive strength to the workpiece 11 is provided on the front surface 21a side of the protective member 21. In this case, as shown in Fig. 2, the front surface 21a side of the protective member 21 is brought into close contact with the front surface 11a of the workpiece 11, so that the protective member 21 is affixed to the front surface 11a of the workpiece 11. As a result, the protective member 21 absorbs the impact applied to the front surface 11a when the workpiece 11 is ground from the back surface 11b side, and the device 15 of the workpiece 11 and the like are protected.

[0022] However, in cases where the device 15 is not formed on the workpiece 11, etc., the protective member 21 does not necessarily have to be affixed to the workpiece 11. In order to improve the ease of handling of the workpiece 11 in the series of steps of this embodiment, a protective member 21 such as a tape having a diameter larger than that of the workpiece 11 may be used, and an annular frame surrounding the workpiece 11 may be fixed to the outer edge of this protective member 21.

[0023] Next, a method for machining the workpiece 11 according to this embodiment will be described. Fig. 2 is a flow diagram of the method for machining the workpiece according to this embodiment. As shown in Fig. 2, the method for machining the workpiece according to this embodiment includes a cut groove forming step S1, a first grinding step S2, and a second grinding step S3.

[0024] In the cutting groove forming step S1, the workpiece 11 to which the above-mentioned protective member 21 is attached is cut from the back surface 11b side, and a ring-shaped cutting groove is formed in a portion of the workpiece 11 corresponding to the outer edge of the area 23 in which the device 15 is formed.

[0025] 3 is a cross-sectional view that shows a schematic view of how the workpiece 11 is cut in the cut groove forming step S1. As shown in FIG 3, a cutting device 10 is used in the cut groove forming step S1.

[0026] The cutting device 10 is equipped with a chuck table 12 configured to hold a workpiece 11 to which a protective member 21 is attached. The chuck table 12 includes a disk-shaped frame 14 formed, for example, from ceramics or the like. A recess 14a having a circular opening at its upper end is formed on the upper surface side of the frame 14. A holding plate 16 formed into a porous disk shape from ceramics or the like is fixed to this recess 14a.

[0027] The upper surface 16a of the holding plate 16 functions as a holding surface for holding the workpiece 11, etc. In this embodiment, the rear surface 21b of the protection member 21 comes into contact with the upper surface 16a of the holding plate 16.

[0028] The lower surface side of the holding plate 16 is connected to a suction source (not shown) such as an ejector via a flow path 14b provided inside the frame 14 and a valve (not shown) arranged outside the frame 14. Therefore, when the valve is opened and negative pressure of the suction source is applied to the upper surface 16a of the holding plate 16 with the back surface 21b of the protective member 21 in contact with the upper surface 16a of the holding plate 16, the back surface 21b of the protective member 21 is sucked by the chuck table 12.

[0029] That is, the workpiece 11 is held on the chuck table 12 via the protective member 21 so that the back surface 11b is exposed upward. When the protective member 21 is not attached to the front surface 11a of the workpiece 11, the front surface 11a of the workpiece 11 is brought into direct contact with the upper surface 16a of the holding plate 16, and then a valve is opened so that the negative pressure of the suction source is applied to the upper surface 16a of the holding plate 16.

[0030] A rotation drive source (not shown) such as a motor is connected to the lower part of the frame 14. The chuck table 12 rotates around a rotation axis A2 that is parallel to or slightly inclined with respect to the vertical direction, by the force generated by this rotation drive source, so that the center of the upper surface 16a of the holding plate 16 becomes the center of rotation.

[0031] The chuck table 12 is supported by a ball screw type chuck table moving mechanism (not shown) equipped with a ball screw for converting a rotational driving force of a motor or the like into a linear driving force. The chuck table 12 moves in a direction approximately parallel to the upper surface 16a of the holding plate 16 by the linear driving force of the chuck table moving mechanism.

[0032] 3, the cutting device 10 has a cutting unit 18 disposed above the chuck table 12. The cutting unit 18 has a spindle 20 having a predetermined length along a direction generally parallel to the upper surface 16a of the chuck table 12, and a cutting blade 22 attached to the tip of the spindle 20.

[0033] The spindle 20 is connected to a rotary drive source (not shown) such as a motor. The force generated by the rotary drive source rotates the spindle 20 around a rotation axis A5 that passes through the center of the spindle 20 and is parallel to the direction along the length of the spindle 20. Together with the spindle 20, the cutting blade 22 attached to the tip of the spindle 20 also rotates.

[0034] The cutting blade 22 has an annular base 24 made of a metal such as stainless steel, and an annular cutting edge 26 provided on the periphery of the annular base 24. The cutting edge 26 is made of abrasive grains made of, for example, diamond or the like dispersed and fixed by a binder made of resin, metal, or the like.

[0035] The cutting unit 18 is connected to a cutting unit moving mechanism (not shown). The cutting unit 18 can be moved by the cutting unit moving mechanism in a direction substantially parallel to the rotation axis A5 of the spindle 20 and in a direction substantially parallel to the rotation axis A2 of the chuck table 12 (vertical direction).

[0036] The cutting device 10 has one or more transport mechanisms (not shown) capable of transporting the workpiece 11 to which the above-mentioned protective member 21 is affixed to the chuck table 12 or the like. The transport mechanism is, for example, a robot arm. The workpiece 11 to which the protective member 21 is affixed is transported by this transport mechanism to the chuck table 12 so that the back surface 11b side of the workpiece is exposed. In addition, the workpiece 11 to which the protective member 21 is affixed is transported from the chuck table 12 to the outside of the chuck table 12 by the transport mechanism.

[0037] In the cut groove forming step S1, the workpiece 11 is held by the chuck table 12 via the protective member 21. Specifically, the back surface 21b side of the protective member 21 is placed on the chuck table 12 by the above-mentioned conveying mechanism so that the back surface 11b side of the workpiece 11 to which the protective member 21 is affixed is exposed.

[0038] Thereafter, when negative pressure from a suction source is applied to the upper surface 16a of the holding plate 16, the back surface 21b of the protective member 21 is sucked to the chuck table 12. That is, the workpiece 11 to which the protective member 21 is affixed is held by the chuck table 12 via the protective member 21. Note that the workpiece 11 to which the protective member 21 is affixed may be placed on the chuck table 12 manually by an operator or the like.

[0039] Next, the positional relationship between the cutting blade 22 of the cutting unit 18 and the workpiece 11 is adjusted. Specifically, the position of the workpiece 11 is adjusted by the chuck table moving mechanism and the cutting unit moving mechanism so that the cutting blade 22 is positioned above a portion of the workpiece 11 that corresponds to the outer edge of the region 23 in which the device 15 is formed.

[0040] After the positional relationship between the cutting blade 22 and the workpiece 11 has been adjusted, as shown in Fig. 3, the motor, which is a rotary drive source, rotates the cutting blade 22 around the rotation axis A5, and then the cutting unit moving mechanism lowers the cutting blade 22. In addition, the rotary drive source connected to the chuck table 12 rotates the chuck table 12 around the rotation axis A2 in accordance with the descent of the cutting blade 22.

[0041] In this manner, by rotating the chuck table 12 about the rotation axis A2 while lowering the rotating cutting blade 22, the lower end of the cutting blade 22 cuts into a portion of the workpiece 11 corresponding to the outer edge of the region 23 in which the device 15 is formed, forming an annular cutting groove. In other words, the cutting groove is formed in an annular portion that is located closer to the center of the back surface 11b of the workpiece 11 than the outer periphery of the back surface 11b and surrounds the center of the back surface 11b.

[0042] When the cutting blade 22 reaches the target cutting depth (predetermined height), the cutting unit moving mechanism stops the descent of the cutting blade 22. Meanwhile, the rotary drive source connected to the chuck table 12 rotates the chuck table 12 one or more revolutions after the descent of the cutting blade 22 stops.

[0043] In this manner, the annular portion of the workpiece 11 is cut and removed by the cutting blade 22 from the back surface 11b toward the front surface 11a to a predetermined depth, thereby forming an annular cut groove 11c in the workpiece 11. Note that instead of lowering the cutting blade 22, the chuck table 12 may be raised so that the lower end of the cutting blade 22 cuts into the workpiece 11 to a predetermined depth.

[0044] For example, the speed at which the cutting blade 22 is lowered (Z-axis feed speed) is set to 0.001 mm / s or more and 0.03 mm / s or less, the rotational speed of the chuck table 12 is set to 1 deg / s or more and 10 deg / s or less, and the rotational speed of the spindle 20 is set to 10,000 rpm or more and 40,000 rpm or less.

[0045] 4 is a cross-sectional view showing a part of the workpiece 11 after the annular cut groove 11c is formed. The cut groove 11c as shown in FIG. 4 is formed in the workpiece 11 by the cut groove forming step S1 described above.

[0046] 4, in this embodiment, the target depth of the cut groove 11c is determined so that the height of the bottom of the cut groove 11c coincides with the height of at least a part of the top surface of the disk-shaped thin plate portion 11d that will ultimately be obtained. The cutting depth of the cutting blade 62 is determined based on this target depth. As a result, a part of the bottom of the cut groove 11c becomes a part of the top surface (the surface on the back surface 11b side) of the disk-shaped thin plate portion 11d.

[0047] The inner edge of the annular thick portion 11e is defined by the outer side wall of the cut groove 11c. The portion of the workpiece 11 inside the cut groove 11c becomes a disk-shaped first portion to be ground 11f that will be ground in a later step.

[0048] Therefore, the width W of the cutting groove 11c, which is substantially the same as the thickness of the cutting blade 22, is set in a range in which the grinding wheel (grinding stone) does not contact the inner edge (outer side wall of the cutting groove 11c) of the thick plate portion 11e in accordance with the grinding accuracy (accuracy of the grinding position) in the subsequent process. W is, for example, 400 μm or more and 800 μm or less.

[0049] In this manner, in the cutting groove forming step S1 of this embodiment, a ring-shaped cutting groove 11c surrounding the center of the back surface 11b is formed in the workpiece 11, thereby obtaining a disk-shaped first grinding portion 11f that is located closer to the center than the cutting groove 11c and will be further ground later, and a ring-shaped thick plate portion 11e that is located closer to the outer periphery than the cutting groove 11c and surrounds the first grinding portion 11f.

[0050] After the cutting groove forming step S1, a first grinding step S2 is performed. In the first grinding step S2, the first grinding target portion 11f is roughly ground from the back surface 11b side in order to thin the first grinding target portion 11f. FIG. 5 is a cross-sectional view that shows a schematic view of the workpiece 11 being ground in the first grinding step S2.

[0051] As shown in Fig. 5, the grinding device 2 includes a chuck table 4 configured to hold a workpiece 11. The chuck table 4 includes a disk-shaped frame 6 formed of, for example, ceramics or the like. A recess 6a having a circular opening at its upper end is formed on the upper surface side of the frame 6. A holding plate 8 formed of, for example, ceramics and the like in a porous disk shape is fixed to this recess 6a.

[0052] The upper surface 8a of the holding plate 8 is configured, for example, in a shape corresponding to the side surface of a cone, and functions as a holding surface for holding the workpiece 11, etc. The difference in height (height difference) between the center 8b of the upper surface 8a of the holding plate 8, which corresponds to the apex of the cone, and the outer edge of the upper surface 8a of the holding plate 8 is generally 10 μm or more and 30 μm or less. In this embodiment, the back surface 21b of the protective member 21 comes into contact with the upper surface 8a of the holding plate 8.

[0053] The lower surface side of the holding plate 8 is connected to a suction source (not shown) such as an ejector via a flow path 6b provided inside the frame 6 and a valve (not shown) arranged outside the frame 6. Therefore, when the valve is opened and negative pressure of the suction source is applied to the upper surface 8a of the holding plate 8 with the back surface 21b of the protective member 21 in contact with the upper surface 8a of the holding plate 8, the back surface 21b of the protective member 21 is sucked by the chuck table 4.

[0054] That is, the workpiece 11 is held on the chuck table 4 via the protective member 21 so that the back surface 11b is exposed upward. When the protective member 21 is not attached to the front surface 11a of the workpiece 11, the front surface 11a of the workpiece 11 is brought into direct contact with the upper surface 8a of the holding plate 8, and then a valve is opened so that the negative pressure of the suction source is applied to the upper surface 8a of the holding plate 8.

[0055] A rotation drive source (not shown) such as a motor is connected to the lower part of the frame 6. The force generated by this rotation drive source rotates the chuck table 4 around a rotation axis A1 that is parallel to or slightly tilted from the vertical direction, so that the center 8b of the upper surface 8a becomes the center of rotation. The frame 6 is supported by a chuck table moving mechanism (not shown), and the force generated by this chuck table moving mechanism moves the chuck table 4 in the horizontal direction.

[0056] 5, a first grinding unit (rough grinding unit) 30 is disposed at a position above the chuck table 4 of the grinding device 2. The first grinding unit 30 includes, for example, a cylindrical spindle housing (not shown). A columnar spindle 32 is accommodated in the space inside the spindle housing.

[0057] A disk-shaped mount 34 having a diameter smaller than that of the workpiece 11 is provided on the lower end of the spindle 32. A circular first grinding wheel (coarse grinding wheel) 36 having approximately the same diameter as the mount 34 is fixed to the lower surface of the mount 34 with a bolt (not shown) or the like.

[0058] The first grinding wheel 36 includes an annular wheel base 38 formed using a metal such as stainless steel or aluminum. A plurality of first grinding stones (coarse grinding stones) 40 are fixed to the annular lower surface of the wheel base 38 along the circumferential direction of the wheel base 38.

[0059] Specifically, the multiple first grinding wheels 40 are arranged in a circular region (a region along the circumference, or a region inside the circumference) with a diameter smaller than the radius of the back surface 11b of the workpiece 11. The width of the first grinding wheels 40 (the length in the direction along the diameter of the first grinding wheel 36) is, for example, 1 mm or more and 5 mm or less, typically 3 mm. However, the width of the first grinding wheels 40 is not necessarily limited to this range.

[0060] Each of the first grinding wheels 40 has a structure in which abrasive grains made of, for example, diamond or the like are dispersed in a binder made of, for example, resin. In this embodiment, for example, the first grinding wheel 40 containing abrasive grains having a grain size of #280 to #1000 as defined by the Japanese Industrial Standards (JIS) R6001 is used. Note that the size (grain size) of the abrasive grains contained in the first grinding wheel 40 is not limited to this.

[0061] A rotation drive source (not shown) such as a motor is connected to the upper end side of the spindle 32. The first grinding wheel 36 rotates around a rotation axis A3 that is parallel to or slightly inclined with respect to the vertical direction by the force generated by this rotation drive source. The spindle housing is supported, for example, by a first grinding unit moving mechanism (not shown), and the first grinding unit 30 moves in the vertical direction by the force generated by this first grinding unit moving mechanism.

[0062] A nozzle (not shown) configured to supply a grinding liquid (typically, water) to the workpiece 11, the first grinding wheel 40, etc. is provided adjacent to the first grinding wheel 36 or inside the first grinding wheel 36. When the workpiece 11 is ground, the first grinding wheel 40 is cooled by the grinding liquid supplied from this nozzle, and chips generated from the workpiece 11 and the first grinding wheel 40 are discharged to the outside of the workpiece 11.

[0063] The grinding device 2 has one or more transport mechanisms (not shown) capable of transporting the workpiece 11 to which the above-mentioned protective member 21 is affixed to the chuck table 4 or the like. The transport mechanism is, for example, a robot arm. The workpiece 11 to which the protective member 21 is affixed is carried into the chuck table 4 by this transport mechanism so that the back surface 11b side of the workpiece is exposed. In addition, the workpiece 11 to which the protective member 21 is affixed is carried out from the chuck table 4 to the outside of the chuck table 4 by the transport mechanism.

[0064] In the first grinding step S2, the workpiece 11 is held by the chuck table 4 via the protective member 21. Specifically, the back surface 21b side of the protective member 21 is placed on the chuck table 4 by the above-mentioned conveying mechanism so that the back surface 11b side of the workpiece 11 to which the protective member 21 is affixed is exposed.

[0065] Thereafter, when a negative pressure from a suction source is applied to the back surface 21b, the back surface 21b of the protective member 21 is sucked to the chuck table 4. That is, the workpiece 11 to which the protective member 21 is attached is held by the chuck table 4 via the protective member 21. Note that the workpiece 11 to which the protective member 21 is attached may be placed on the chuck table 4 manually by an operator or the like.

[0066] Next, the chuck table 4 moves to a position directly below the first grinding unit 30. More specifically, the positional relationship between the first grinding wheel 36 and the chuck table 4 (and the workpiece 11) is adjusted by the chuck table moving mechanism so that all the first grinding stones 40 are positioned directly above the cutting grooves 11c or the first portions to be ground 11f.

[0067] Thereafter, the chuck table 4 and the first grinding wheel 36 each rotate, and the first grinding unit 30 (the first grinding wheel 36) descends. That is, the first grinding wheel 36 and the workpiece 11 move relatively in a direction intersecting with the back surface 11b of the workpiece 11 while rotating relative to each other. At this time, liquid is supplied from a nozzle to the workpiece 11, the first grinding wheel 40, etc.

[0068] 5, the first grinding wheel 40 comes into contact with the first portion to be ground 11f of the workpiece 11 from the back surface 11b side, and grinding of the first portion to be ground 11f is started. In this embodiment, the first grinding unit 30 (first grinding wheel 36) is lowered until the lower end of the first grinding wheel 40 reaches a target height position higher than the bottom position of the cutting groove 11c. That is, in this embodiment, the bottom of the cutting groove 11c is not ground by the first grinding wheel 40.

[0069] There is no significant restriction on the specific grinding conditions. For example, in order to achieve efficient grinding of the first portion to be ground 11f, the rotation speed of the chuck table 4 is set to 100 rpm or more and 600 rpm or less, typically 300 rpm, the rotation speed of the first grinding wheel 36 is set to 1000 rpm or more and 7000 rpm or less, typically 4500 rpm, and the descending speed of the first grinding unit 30 (grinding feed speed) is set to 0.8 μm / s or more and 10 μm / s or less, typically 6 μm / s.

[0070] Fig. 6 is a cross-sectional view showing a schematic view of a part of the workpiece 11 after rough grinding. As shown in Fig. 6, the first portion to be ground 11f is ground to obtain a disk-shaped second portion to be ground 11g to be further ground in a later step. In addition, a damaged layer 11h including scratches or distortion is generated on the upper surface (surface on the back surface 11b side, surface to be ground) of the second portion to be ground 11g.

[0071] In this embodiment, the workpiece 11 is ground so that the upper surface (surface on the back surface 11b side) of the second portion to be ground 11g (damaged layer 11h) is formed at a height (distance) of 20 μm to 100 μm from the bottom of the cut groove 11c, typically at a height (distance) of 40 μm from the bottom of the cut groove 11c. This reduces the amount of workpiece 11 removed in the subsequent finish grinding, and therefore reduces the time required to complete grinding.

[0072] After the first grinding step S2, a second grinding step S3 is performed. In the second grinding step S3, the second grinding target portion 11g is finish-ground from the back surface 11b side in order to remove the damaged layer 11h generated in the second grinding target portion 11g. FIG. 7 is a cross-sectional view showing a schematic state in which the workpiece 11 is ground in the second grinding step S3.

[0073] 7, a second grinding unit (finish grinding unit) 50 separate from the first grinding unit 30 is disposed at a position above the chuck table 4 of the grinding device 2. The second grinding unit 50 includes, for example, a cylindrical spindle housing (not shown). A columnar spindle 52 is housed in the space inside the spindle housing.

[0074] A disk-shaped mount 54 having a diameter smaller than that of the workpiece 11 is provided on the lower end of the spindle 52. A circular second grinding wheel (finish grinding wheel) 56 having approximately the same diameter as the mount 54 is fixed to the lower surface of the mount 54 with a bolt (not shown) or the like.

[0075] The second grinding wheel 56 includes an annular wheel base 58 made of metal such as stainless steel or aluminum. A plurality of second grinding stones (finish grinding stones) 60 are fixed to the annular lower surface of the wheel base 58 along the circumferential direction of the wheel base 58.

[0076] Specifically, the second grinding wheels 60 are arranged in a circular region (a region along the circumference or a region inside the circumference) having a diameter smaller than the radius of the back surface 11b of the workpiece 11. The width of the second grinding wheels 60 (the length in the direction along the diameter of the second grinding wheel 56) is, for example, 1 mm or more and 5 mm or less, typically 3 mm. However, the width of the second grinding wheels 60 is not necessarily limited to this range.

[0077] Each of the second grinding wheels 60 has a structure in which abrasive grains made of, for example, diamond or the like are dispersed in a binder made of resin or the like. In this embodiment, for example, the second grinding wheel 60 containing abrasive grains having a grain size of #2000 to #8000 as defined by the Japanese Industrial Standards (JIS) R6001 is used.

[0078] That is, the size (average particle size) of the abrasive grains contained in the second grinding wheel 60 is smaller than the size (average particle size) of the abrasive grains contained in the first grinding wheel 40. In this specification, the particle size at 50% cumulative of the particle size distribution measured by the laser diffraction / scattering method (median diameter, d50 diameter, 50% diameter) is referred to as the average particle size.

[0079] When the workpiece 11 is ground with the second grinding wheel 56 including such a second grinding wheel 60, the amount of the workpiece 11 that can be removed per unit time is smaller than when the workpiece 11 is ground with the first grinding wheel 36, but a damaged layer is less likely to occur. On the other hand, the size of the abrasive grains contained in the second grinding wheel 60 is not necessarily limited to the above-mentioned range. It is sufficient that the second grinding wheel 60 contains at least abrasive grains with a smaller grain size than the abrasive grains contained in the first grinding wheel 40. In other words, it is sufficient that the second grinding wheel 60 does not contain at least abrasive grains larger than the abrasive grains contained in the first grinding wheel 40.

[0080] A rotation drive source (not shown) such as a motor is connected to the upper end side of the spindle 52. The second grinding wheel 56 rotates around a rotation axis A4 that is parallel to or slightly inclined with respect to the vertical direction by the force generated by this rotation drive source. The spindle housing is supported, for example, by a second grinding unit moving mechanism (not shown), and the second grinding unit 50 moves in the vertical direction by the force generated by this second grinding unit moving mechanism.

[0081] A nozzle (not shown) configured to supply a grinding liquid (typically, water) to the workpiece 11, the second grinding wheel 60, etc. is provided adjacent to the second grinding wheel 56 or inside the second grinding wheel 56. When the workpiece 11 is ground, the second grinding wheel 60 is cooled by the grinding liquid supplied from this nozzle, and chips generated from the workpiece 11 and the second grinding wheel 60 are discharged to the outside of the workpiece 11.

[0082] When the second grinding unit 50 (second grinding wheel 56) grinds the second portion to be ground 11g, first, the chuck table 4 moves to a position directly below the second grinding unit 50. More specifically, the positional relationship between the second grinding wheel 56 and the chuck table 4 (and the workpiece 11) is adjusted by the chuck table moving mechanism so that all the second grinding stones 60 are positioned in the cutting grooves 11c or directly above the second portion to be ground 11g.

[0083] Thereafter, the chuck table 4 and the second grinding wheel 56 each rotate, and the second grinding unit 50 (second grinding wheel 56) descends. That is, the second grinding wheel 56 and the workpiece 11 move relatively in a direction intersecting with the back surface 11b of the workpiece 11 while rotating relative to each other. At this time, liquid is supplied from a nozzle to the workpiece 11, the second grinding wheel 60, etc.

[0084] 7, the second grinding wheel 60 comes into contact with the second portion to be ground 11g of the workpiece 11 from the back surface 11b side, and grinding of the second portion to be ground 11g is started. In this embodiment, the second grinding unit 50 (second grinding wheel 56) is lowered until the lower end of the second grinding wheel 60 reaches a position at a height approximately equal to the bottom of the cutting groove 11c. The bottom of the cutting groove 11c may be slightly ground by the second grinding wheel 60. Of course, a part of the bottom of the cutting groove 11c does not have to be ground by the second grinding wheel 60.

[0085] There are no significant limitations on the specific grinding conditions. For example, in order to achieve efficient and highly accurate grinding of the workpiece 11, the rotation speed of the chuck table 4 is set to 100 rpm or more and 600 rpm or less, typically 300 rpm, the rotation speed of the second grinding wheel 56 is set to 1000 rpm or more and 7000 rpm or less, typically 4000 rpm, and the descending speed of the second grinding unit 50 (grinding feed rate) is set to 0.1 μm / s or more and 0.8 μm / s or less, typically 0.5 μm / s.

[0086] Fig. 8 is a cross-sectional view showing a part of the workpiece 11 after finish grinding. As shown in Fig. 8, the second grinding target portion 11g is ground to remove the damaged layer 11h, and the disk-shaped thin plate portion 11d is completed. As described above, the disk-shaped thin plate portion 11d includes the bottom of the cutting groove 11c in a part of its upper surface.

[0087] As described above, in the method for processing the workpiece according to the present embodiment, the annular cutting groove 11c that defines the inner edge of the annular thick plate portion 11e is formed by cutting using the cutting blade 22, which in principle is less likely to cause a damaged layer compared to grinding using the first grinding wheel 40. Therefore, at least the damaged layer 11h that occurs when the first grinding wheel 40 is used is not generated at the bottom of the annular cutting groove 11c. Therefore, the entire bottom of the annular cutting groove 11c can be treated as the effective area of ​​the disk-shaped thin plate portion 11d.

[0088] Furthermore, the volume of the portion removed from the workpiece 11 using the cutting device 10 when forming the annular cut groove 11c is significantly smaller than the volume of the portion removed from the workpiece 11 using the first grinding wheel 40 and the second grinding wheel 60. Therefore, the time required to form the annular cut groove 11c is sufficiently shorter than the time required to complete grinding of the workpiece 11. In other words, in the method for processing a workpiece according to this embodiment, the time required to complete grinding of the workpiece 11 is not significantly longer than that in the conventional method.

[0089] The present invention is not limited to the above-described embodiment, and may be modified in various ways. For example, in the above-described embodiment, the workpiece 11 is ground by one grinding device 2 including the first grinding unit 30 and the second grinding unit 50, but the workpiece 11 may be ground by one or more grinding devices having a different structure.

[0090] In addition, the structures, methods, and the like according to the above-described embodiment and each modified example may be modified as appropriate without departing from the scope of the present invention. [Explanation of symbols]

[0091] 11: Workpiece 11a: Surface (first side) 11b: Back side (second side) 11c: Cutting groove 11d: Thin plate part 11e: Thick plate section 11f: First grinding section 11g: Second grinding target part 11h: Damage layer 13: Street (planned division line) 15: Device 21: Protective materials 21a: Surface 21b: Back side 23: Device area 25: Surplus outer area 2: Grinding equipment 4: Chuck table 6: Frame 6a: Recess 6b: Flow path 8: Holding plate 8a:Top surface 8b: Center 10: Cutting equipment 12: Chuck table 14:Frame body 14a: Recess 14b: Flow path 16: Holding plate 16a:Top surface 18: Cutting unit 20 ;Spindle 22: Cutting blade 24: Foundation 26: Cutting edge 30: First grinding unit (rough grinding unit) 32: Spindle 34: Mount 36: First grinding wheel (rough grinding wheel) 38: Wheel base 40: First grinding wheel (rough grinding wheel) 50: Second grinding unit (finish grinding unit) 52: Spindle 54: Mount 56: Second grinding wheel (finishing grinding wheel) 58: Wheel base 60: Second grinding wheel (finishing grinding wheel) A1: Rotation axis A2:Rotation axis A3: Rotation axis A4: Rotation axis A5: Rotation axis

Claims

1. A method for processing a workpiece, the method being adapted for forming a disk-shaped thin plate portion and an annular thick plate portion surrounding the thin plate portion and thicker than the thin plate portion, by processing a workpiece having a circular first surface and a circular second surface opposite to the first surface, the method comprising: a cutting groove forming step in which, while rotating an annular cutting blade, the cutting blade is cut into an annular portion of the second surface of the workpiece that is located closer to the center of the second surface than the outer periphery of the second surface and surrounds the center of the second surface, thereby forming a cutting groove in the annular portion of the workpiece, a disk-shaped first grinding portion located closer to the center than the cutting groove, and an annular thick plate portion located closer to the outer periphery than the cutting groove, in the workpiece; a first grinding step of rotating a first grinding wheel, in which a plurality of first grinding stones each containing abrasive grains are arranged in a circular area having a diameter smaller than a radius of the workpiece, and the workpiece, after the cutting groove forming step, to grind the first portion to be ground by the plurality of first grinding stones to a depth not reaching the bottom of the cutting groove, thereby forming a disk-shaped second portion to be ground that is thinner than the first portion to be ground; a second grinding wheel in which a plurality of second grinding wheels, each containing smaller abrasive grains than the abrasive grains contained in the first grinding wheel, are arranged in a circular area having a diameter smaller than the radius of the workpiece; and a second grinding step in which the workpiece is rotated to grind the second portion to be ground with the plurality of second grinding wheels to a depth reaching the bottom of the cutting groove, thereby forming a disk-shaped thin plate portion thinner than the second portion to be ground.

2. 2. The method for machining a workpiece according to claim 1, wherein the width of the cut groove is 400 [mu]m or more.

3. 3. The method for processing a workpiece according to claim 1 or 2, wherein in the second grinding step, when the second grinding target portion is ground from the second surface side, a portion of the bottom of the cutting groove is ground with the second grinding wheel.

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