Grinding method for workpieces
The described grinding method forms a recess on the wafer's outer circumference and then grinds the unground area to thin the wafer, addressing the complications of edge trimming and maintaining wafer integrity, thus simplifying processing and preventing damage.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- DISCO CORP
- Filing Date
- 2022-10-25
- Publication Date
- 2026-06-23
AI Technical Summary
The existing methods for grinding and thinning wafers require separate edge trimming with a cutting blade, adding time and cost, and complicating processing steps due to changes in wafer diameter and marker removal, which can lead to damage and necessitate additional orientation confirmation.
A method involving a recess formation step and a slide grinding step using a grinding wheel to form a recess on the outer circumference while leaving an unground area, followed by grinding this area to thin the wafer without damaging the edge, eliminating the need for edge trimming.
This method simplifies processing steps by preventing damage to the wafer edge and eliminating the need for edge trimming, while maintaining consistent dimensions and orientation markers.
Smart Images
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Abstract
Description
Technical Field
[0001] The present invention relates to a method for grinding a workpiece by using a grinding wheel.
Background Art
[0002] In the manufacturing process of device chips, a wafer having a device region in which devices are formed in a plurality of regions partitioned by a plurality of streets (division planned lines) arranged in a grid pattern on the surface side is used. By dividing this wafer along the streets, a plurality of device chips each having a device can be obtained. The device chips are incorporated into various electronic devices such as mobile phones and personal computers.
[0003] In recent years, with the miniaturization of electronic devices, thinning of device chips has been demanded. Therefore, a process of grinding and thinning the wafer before division using a grinding device may be performed. The grinding device includes a chuck table for holding a workpiece and a grinding unit for grinding the workpiece, and an annular grinding wheel including a grinding stone is attached to the grinding unit. The wafer is held by the chuck table, and while rotating the chuck table and the grinding wheel, the grinding stone is brought into contact with the back surface side of the wafer, whereby the wafer is ground and thinned.
[0004] Note that the wafer is subjected to a so-called chamfering process in which the outer peripheral portion of the wafer is ground to make the side surface of the wafer curved. When the chamfered wafer is ground and thinned, the outer peripheral portion of the wafer becomes a sharp edge shape. And when the outer peripheral portion of the wafer having the sharp edge shape is pressed against the chuck table side by the grinding stone, chipping or cracking may occur at the outer peripheral portion of the wafer, and the wafer may be damaged.
[0005] Therefore, when grinding and thinning a beveled wafer, a process called edge trimming is sometimes performed beforehand, in which the outer edge of the wafer is cut in an annular shape with a cutting blade (see Patent Document 1). When edge trimming is performed, the beveled area of the wafer is removed, so even if the wafer is subsequently ground and thinned, the outer edge of the wafer will not have a sharp edge shape. This makes it less likely for the wafer to be damaged. [Prior art documents] [Patent Documents]
[0006] [Patent Document 1] Japanese Patent Publication No. 2000-173961 [Overview of the project] [Problems that the invention aims to solve]
[0007] As described above, when performing edge trimming on a workpiece such as a chamfered wafer, the outer circumference of the workpiece is cut in an annular shape with a cutting blade before grinding. Therefore, a process is required to process the workpiece with a cutting device separate from the grinding device, which adds time and cost to the preparation for grinding.
[0008] Furthermore, if the workpiece is ground and thinned after edge trimming, the diameter of the workpiece will change before and after processing. Therefore, it becomes necessary to adjust the equipment used for subsequent handling of the workpiece (transport, holding, processing, imaging, etc.) to match the dimensions of the workpiece after grinding. In addition, if markers such as notches or orientation flats indicating the crystal orientation of the workpiece are formed on the outer circumference of the workpiece, these markers will be removed by edge trimming, so it will be necessary to confirm the crystal orientation by other methods after grinding the workpiece. As a result, the processing steps for the workpiece become complicated.
[0009] This invention has been made in view of the above problems, and aims to provide a method for grinding a workpiece that can simplify the workpiece processing steps while preventing damage to the workpiece. [Means for solving the problem]
[0010] According to one aspect of the present invention, a method for grinding a workpiece having a chamfered portion on its outer circumference is provided, comprising: a holding step of holding the workpiece with a chuck table; a recess forming step of forming a recess in the workpiece while leaving an ungrinded area on the outer circumference of the workpiece by moving the chuck table and the grinding wheel relatively along a direction parallel to the rotation axis of the grinding wheel, with the chuck table and the grinding wheel rotating after the holding step; and a slide grinding step of grinding the ungrinded area with the grinding wheel by moving the chuck table and the grinding wheel relatively along a direction intersecting the rotation axis of the grinding wheel, with the recess forming step, with the chuck table and the grinding wheel rotating after the recess forming step.
[0011] Preferably, the grinding method for the workpiece further includes a pre-grinding step to thin the entire workpiece by grinding it before the recess-forming step. Preferably, in the slide grinding step, the grinding wheel is moved relative to the outer peripheral edge of the workpiece while moving the grinding wheel relative to the bottom surface of the recess.
[0012] Preferably, the workpiece is ground by performing the recess formation step and the slide grinding step multiple times. [Effects of the Invention]
[0013] In a workpiece grinding method according to one aspect of the present invention, the workpiece is ground with a grinding wheel to form a recess in the workpiece while leaving an unground area on the outer circumference of the workpiece, and then the unground area is ground with a grinding wheel to thin the workpiece while preventing damage to the outer circumference. This eliminates the need for edge trimming, which involves cutting the outer circumference of the workpiece with a cutting blade, and simplifies the workpiece processing steps. [Brief explanation of the drawing]
[0014] [Figure 1] This is a perspective view showing a grinding machine. [Figure 2] This is a cross-sectional view showing a chuck table. [Figure 3] This is a perspective view showing the workpiece. [Figure 4] This is a flowchart showing the processing method for a workpiece. [Figure 5] Figure 5(A) is a partial cross-sectional side view showing the grinding apparatus in the holding step, and Figure 5(B) is a perspective view showing the grinding apparatus in the holding step. [Figure 6] Figure 6(A) is a partial cross-sectional side view showing the grinding apparatus in the recess formation step, and Figure 6(B) is a perspective view showing the grinding apparatus in the recess formation step. [Figure 7] Figure 7(A) is a partial cross-sectional side view showing the grinding apparatus in the slide grinding step, and Figure 7(B) is a perspective view showing the grinding apparatus in the slide grinding step. [Figure 8] Figure 8(A) is a partial cross-sectional side view showing the grinding apparatus in the slide grinding step according to a modified example, and Figure 8(B) is a perspective view showing the grinding apparatus in the slide grinding step according to a modified example. [Figure 9] Figure 9(A) is a partial cross-sectional side view showing the grinding apparatus in the pre-grinding step, and Figure 9(B) is a perspective view showing the grinding apparatus in the pre-grinding step. [Modes for carrying out the invention]
[0015] Hereinafter, an embodiment according to an aspect of the present invention will be described with reference to the accompanying drawings. First, a configuration example of a grinding apparatus that can be used for implementing a method for grinding a workpiece according to this embodiment will be described. FIG. 1 is a perspective view showing a grinding apparatus 2. In FIG. 1, the X-axis direction (the first horizontal direction, the front-rear direction) and the Y-axis direction (the second horizontal direction, the left-right direction) are perpendicular to each other. Also, the Z-axis direction (the height direction, the vertical direction, the up-down direction) is perpendicular to the X-axis direction and the Y-axis direction.
[0016] The grinding apparatus 2 includes a chuck table (holding table) 4 that holds a workpiece, which is an object to be machined by the grinding apparatus 2. The chuck table 4 includes a columnar frame body (main body portion) 6 made of a metal such as SUS (stainless steel), glass, ceramics, resin, or the like. A columnar concave portion 6b is provided at the central portion on the upper surface 6a side of the frame body 6.
[0017] A disc-shaped holding member 8 made of a porous material such as porous ceramics is fitted into the concave portion 6b of the frame body 6. The holding member 8 includes a large number of pores that communicate from the upper surface to the lower surface of the holding member 8. The upper surface of the holding member 8 constitutes a circular suction surface 8a that sucks the workpiece when the workpiece is held by the chuck table 4.
[0018] FIG. 2 is a cross-sectional view showing the chuck table 4. The upper surface 6a of the frame body 6 and the suction surface 8a of the holding member 8 constitute the holding surface 4a of the chuck table 4. The holding surface 4a is connected to a suction source (not shown) such as an ejector via pores included in the holding member 8, a flow path 6c provided inside the frame body 6, a valve (not shown), and the like.
[0019] The holding surface 4a of the chuck table 4 is formed in a conical shape with the center of the holding surface 4a as the apex and is slightly inclined with respect to the radial direction of the holding surface 4a. Then, the chuck table 4 is arranged in a slightly inclined state such that a holding region 4b corresponding to a part of the holding surface 4a and extending from the center to the outer peripheral edge of the holding surface 4a is substantially parallel to the horizontal plane. The region of the workpiece held in the holding region 4b of the holding surface 4a is ground by a grinding unit 10 described later.
[0020] Note that, for convenience of explanation, the inclination of the holding surface 4a is exaggerated in FIG. 2, but the actual inclination of the holding surface 4a is small. For example, when the diameter of the holding surface 4a is about 290 mm or more and 310 mm or less, the height difference (corresponding to the height of the cone) between the center and the outer peripheral edge of the holding surface 4a is set to about 20 μm or more and 40 μm or less.
[0021] A rotation drive source (not shown) such as a motor for rotating the chuck table 4 is connected to the chuck table 4. The rotation drive source rotates the chuck table 4 around the rotation axis 4c. The rotation axis 4c of the chuck table 4 is set along a direction perpendicular to the radial direction of the holding surface 4a and is slightly inclined with respect to the Z-axis direction. Further, the rotation axis 4c intersects the holding surface 4a while passing through the center of the holding surface 4a.
[0022] A moving unit (not shown) for moving the chuck table 4 along the horizontal direction (XY plane) is connected to the chuck table 4. For example, the moving unit is constituted by a ball screw type X-axis moving mechanism for moving the chuck table 4 along the X-axis direction. In this case, the X-axis moving mechanism includes a ball screw (not shown) arranged along the X-axis direction, a pulse motor (not shown) for rotating the ball screw, and a nut portion (not shown) connected to the chuck table 4 and screwed with the ball screw.
[0023] Further, as shown in FIG. 1, the grinding device 2 includes a grinding unit 10 for performing grinding on the workpiece. The grinding unit 10 includes a columnar spindle 12 arranged along the Z-axis direction. A rotation drive source (not shown) such as a motor for rotating the spindle 12 is connected to the base end portion (upper end portion) of the spindle 12. When the rotation drive source is driven, the spindle 12 rotates around the rotation axis 12a set along the Z-axis direction.
[0024] A disc-shaped wheel mount 14 made of metal or the like is fixed to the tip (lower end) of the spindle 12. An annular grinding wheel 16 for grinding the workpiece is detachably mounted on the lower surface of the wheel mount 14. For example, the grinding wheel 16 is fixed to the wheel mount 14 by fasteners such as bolts.
[0025] The grinding wheel 16 is made of a metal such as aluminum or stainless steel and includes an annular wheel base 18 formed to be approximately the same diameter as the wheel mount 14. The upper side of the wheel base 18 is fixed to the lower side of the wheel mount 14.
[0026] Multiple grinding wheels 20 are fixed to the lower surface of the wheel base 18. The lower surface of each grinding wheel 20 constitutes a grinding surface 20a for grinding the workpiece. For example, the grinding wheels 20 are formed in a rectangular parallelepiped shape and are arranged in a ring shape at roughly equal intervals along the circumferential direction of the wheel base 18.
[0027] The grinding wheel 20 includes abrasive grains made of diamond, cBN (cubic boron nitride), etc., and a binder (bonding material) such as a metal bond, resin bond, or vitrified bond to fix the abrasive grains. However, there are no restrictions on the material, shape, structure, size, etc. of the grinding wheel 20. The number of grinding wheels 20 can also be set arbitrarily.
[0028] The grinding wheel 16 rotates around its axis of rotation 12a by power transmitted from a rotational drive source (not shown) via the spindle 12 and wheel mount 14. That is, the axis of rotation 12a of the spindle 12 corresponds to the axis of rotation of the wheel mount 14 and the grinding wheel 16. When the grinding wheel 16 rotates, each of the multiple grinding wheels 20 revolves around the axis of rotation 12a along an annular trajectory (path) that is roughly parallel to the horizontal plane (XY plane).
[0029] The grinding unit 10 is connected to a moving unit (not shown) that moves the grinding unit 10 along the Z-axis direction. For example, the moving unit is composed of a ball screw type Z-axis moving mechanism that moves the grinding unit 10 along the Z-axis direction. In this case, the Z-axis moving mechanism comprises a ball screw (not shown) arranged along the Z-axis direction, a pulse motor (not shown) that rotates the ball screw, and a nut (not shown) connected to the grinding unit 10 and into which the ball screw is screwed.
[0030] When the chuck table 4 is moved by the X-axis movement mechanism, the chuck table 4 and the grinding wheel 16 move relative to each other along the X-axis. Also, when the grinding unit 10 is raised or lowered by the Z-axis movement mechanism, the chuck table 4 and the grinding wheel 16 move relative to each other along the Z-axis.
[0031] A grinding fluid supply passage (not shown) for supplying a liquid (grinding fluid) such as pure water is provided inside or near the grinding unit 10. When grinding a workpiece with the grinding wheel 16, the grinding fluid is supplied to the workpiece and the grinding wheel 20. This cools the workpiece and the grinding wheel 20, and washes away the debris (grinding shavings) generated by the grinding process.
[0032] Furthermore, the grinding device 2 includes a controller (not shown) that controls the grinding device 2. The controller is connected to the components of the grinding device 2 and generates control signals that control the operation of each component. For example, the controller is composed of a computer and includes a calculation unit that performs calculations necessary for the operation of the grinding device 2, and a storage unit that stores various information (data, programs, etc.) used for the operation of the grinding device 2. The calculation unit includes a processor such as a CPU (Central Processing Unit). The storage unit includes memory such as ROM (Read Only Memory) and RAM (Random Access Memory).
[0033] Figure 3 is a perspective view showing a workpiece 11 being ground by the grinding device 2. For example, the workpiece 11 is a disc-shaped wafer made of a semiconductor material such as single-crystal silicon, and includes a surface (first surface) 11a and a back surface (second surface) 11b that are generally parallel to each other, and a side surface (chamfered portion) 11c connected to the surface 11a and the back surface 11b.
[0034] The workpiece 11 is chamfered by grinding its outer periphery to create a curved surface on its side surface 11c. This chamfering process removes the corners formed at the boundary between the surface 11a and the side surface 11c, and at the boundary between the back surface 11b and the side surface 11c, shaping the side surface 11c into a curved (arc-shaped) surface from the surface 11a to the back surface 11b. In other words, the side surface 11c corresponds to the curved chamfered portion that has been chamfered, and it curves radially outward from the workpiece 11 (see Figure 5(A), etc.).
[0035] The workpiece 11 is divided into multiple rectangular regions by multiple streets (division lines) 13 arranged in a grid pattern so as to intersect each other. Furthermore, devices 15 such as ICs (Integrated Circuits), LSIs (Large Scale Integrations), LEDs (Light Emitting Diodes), and MEMS (Micro Electro Mechanical Systems) devices are formed on the surface 11a side of each region divided by the streets 13.
[0036] The workpiece 11 has a substantially circular device region 17 on which multiple devices 15 are formed, and an annular outer peripheral surplus region 19 surrounding the device region 17, on the surface 11a side. The outer peripheral surplus region 19 corresponds to a band-shaped region of a predetermined width (for example, about 2 mm) that includes the outer edge of the surface 11a. In the outer peripheral surplus region 19, there are no devices 15 formed, or only devices 15 that are not used in the product (dummy devices) are formed. In Figure 3, the virtual boundary between the device region 17 and the outer peripheral surplus region 19 is shown by a dashed line.
[0037] There are no restrictions on the material, shape, structure, size, etc., of the workpiece 11. For example, the workpiece 11 may be a substrate (wafer) made of semiconductors other than silicon (GaAs, InP, GaN, SiC, etc.), glass (quartz glass, borosilicate glass, etc.), ceramics, resin, metal, etc. There are also no restrictions on the type, quantity, shape, structure, size, arrangement, etc., of the devices 15.
[0038] By dividing the workpiece 11 along the street 13, multiple device chips, each containing a device 15, are manufactured. Furthermore, if the back surface 11b of the workpiece 11 is ground to thin it before dividing it, a thinner device chip can be obtained.
[0039] Next, a specific example of the grinding method for a workpiece according to this embodiment will be described. Figure 4 is a flowchart showing the processing method for a workpiece. In this embodiment, the workpiece 11 is thinned by grinding the back surface 11b side of the workpiece 11 using the grinding device 2.
[0040] First, the workpiece 11 is held in place by the chuck table 4 (holding step S1). Figure 5(A) is a partial cross-sectional side view showing the grinding device 2 in holding step S1, and Figure 5(B) is a perspective view showing the grinding device 2 in holding step S1. Note that in Figure 5(A), for simplification, the holding surface 4a of the chuck table 4 is shown as flat (the same applies to Figures 6(A) and subsequent figures). However, as mentioned above, the actual holding surface 4a is formed in a conical shape (see Figure 2).
[0041] In the holding step S1, the workpiece 11 is placed on the chuck table 4 such that the front surface 11a faces the holding surface 4a and the back surface 11b is exposed upwards. At this time, the workpiece 11 is positioned concentrically with the holding surface 4a such that the rotation axis 4c of the chuck table 4 passes through the center of the workpiece 11. In addition, the entire suction surface 8a (see Figure 1) of the chuck table 4 is covered by the workpiece 11. In this state, when the suction force (negative pressure) of the suction source is applied to the holding surface 4a, the workpiece 11 is held by suction from the chuck table 4.
[0042] When holding the workpiece 11 with the chuck table 4, a protective member (not shown) may be fixed to the surface 11a side of the workpiece 11. For example, a circular sheet formed to be approximately the same diameter as the workpiece 11 may be used as the protective member. Specifically, the protective member includes a film-like base material and an adhesive layer (sticking agent) provided on the base material. The base material is made of a resin such as polyolefin, polyvinyl chloride, or polyethylene terephthalate, and the adhesive layer is made of an epoxy, acrylic, or rubber-based adhesive. The adhesive layer may also be an ultraviolet-curing resin that hardens when exposed to ultraviolet light.
[0043] The protective member is fixed so as to cover the entire surface 11a side of the workpiece 11. This protects the surface 11a side of the workpiece 11 and the device 15 (see Figure 3) from the protective member. The workpiece 11 is then held by the holding surface 4a of the chuck table 4 via the protective member.
[0044] Next, the workpiece 11 is ground with the grinding wheel 20 to form a recess in the workpiece 11 while leaving an unground area on the outer circumference of the workpiece 11 (recess formation step S2). Figure 6(A) is a partial cross-sectional side view showing the grinding apparatus 2 in recess formation step S2, and Figure 6(B) is a perspective view showing the grinding apparatus 2 in recess formation step S2.
[0045] In the recess formation step S2, the positional relationship between the chuck table 4 and the grinding wheel 16 is first adjusted. Specifically, the chuck table 4 is moved along the X-axis using a moving unit (not shown) to position it so that the center of the workpiece 11 and the trajectory of the grinding wheel 20 coincide in the Z-axis direction.
[0046] Furthermore, the diameter of the grinding wheel 20's trajectory is smaller than the radius of the workpiece 11. For example, the diameter of the grinding wheel 20's trajectory is set to be approximately the same as the radius of the device region 17 (see Figure 3) of the workpiece 11. Therefore, each of the multiple grinding wheels 20 is positioned so as to overlap with the region radially inward of the workpiece 11, rather than the outer edge of the workpiece 11.
[0047] Next, with the chuck table 4 and grinding wheel 16 rotating, the chuck table 4 and grinding wheel 16 are moved relative to each other along a direction parallel to the rotation axis 12a (Z-axis direction). As a result, the back surface 11b of the workpiece 11 is ground by the grinding surface 20a of the grinding wheel 20, and a circular recess (groove) 21 is formed in the center of the back surface 11b of the workpiece 11.
[0048] Specifically, first, the chuck table 4 is rotated around the rotation axis 4c, and the grinding wheel 16 is rotated around the rotation axis 12a. For example, the rotation speed of the chuck table 4 is set to between 100 rpm and 300 rpm, and the rotation speed of the grinding wheel 16 (the rotation speed of the spindle 12) is set to between 2000 rpm and 6000 rpm.
[0049] Next, the grinding unit 10 is lowered along the Z-axis direction by a moving unit (not shown). This causes the chuck table 4 and the grinding wheel 16 to move relative to each other along a direction parallel to the rotation axis 12a (Z-axis direction), bringing the workpiece 11 and the grinding wheel 20 closer together. The relative movement speed (machining feed rate) between the chuck table 4 and the grinding wheel 16 in the Z-axis direction is set to, for example, 0.1 μm / s or more and 5 μm / s or less.
[0050] When the grinding wheel 20 comes into contact with the workpiece 11, it rotates so as to pass through the rotation axis 4c of the chuck table 4, grinding the central part of the back surface 11b of the workpiece 11. As a result, only the central part of the workpiece 11 is thinned, and a circular recess 21 is formed in the central part of the back surface 11b of the workpiece 11.
[0051] Furthermore, an annular ungrinding region (protrusion) 23 remains on the outer circumference of the workpiece 11, corresponding to the area that has not been ground. The ungrinding region 23 includes the outer periphery excess region 19 (see Figure 3) and surrounds the device region 17 (see Figure 3) and the recess 21. The width of the ungrinding region 23 depends on the diameter of the raceway of the grinding wheel 20, and is, for example, 2 mm or less.
[0052] Then, when the depth of the recess 21 reaches a predetermined value and the thickness of the central part of the workpiece 11 (device region 17, see Figure 3) reaches a predetermined target value (finished thickness), the descent of the grinding unit 10 is stopped. This completes the formation of the recess 21 by the grinding wheel 16. The recess 21 formed in the workpiece 11 includes a circular bottom surface 21a that is generally parallel to the front surface 11a and back surface 11b of the workpiece 11, and an annular side surface (side wall, inner wall) 21b connected to the bottom surface 21a and back surface 11b. The diameter of the recess 21 is generally the same as the diameter of the device region 17, and the recess 21 is formed to overlap with multiple devices 15 (see Figure 3).
[0053] As described above, in the recess formation step S2, the grinding wheel 20 does not come into contact with the outer periphery (ungrinded area 23) of the workpiece 11, and the outer periphery of the workpiece 11 is not ground or thinned. Therefore, the outer periphery of the chamfered workpiece 11 does not become sharply pointed (sharp edge shape) and is maintained in a thick state. This prevents the outer periphery of the workpiece 11, which has a sharp edge shape, from being pressed towards the holding surface 4a by the grinding wheel 20, and suppresses the occurrence of chipping or cracking on the outer periphery of the workpiece 11.
[0054] Next, the unground area 23 is ground with the grinding wheel 20 (slide grinding step S3). Figure 7(A) is a partial cross-sectional side view showing the grinding device 2 in slide grinding step S3, and Figure 7(B) is a perspective view showing the grinding device 2 in slide grinding step S3.
[0055] In the slide grinding step S3, while maintaining the rotation of the chuck table 4 and the grinding wheel 16, the chuck table 4 and the grinding wheel 16 are moved relative to each other along a direction intersecting the rotation axis 12a. Specifically, the chuck table 4 is moved along the X-axis direction by a moving unit (not shown), thereby moving the chuck table 4 and the grinding wheel 16 relative to each other along the X-axis direction.
[0056] The direction of movement of the chuck table 4 is set such that the rotation axis 4c of the chuck table 4 moves away from the rotation axis 12a of the grinding wheel 16, and the outer edge (side surface 11c) of the workpiece 11 approaches the grinding wheel 20. As a result, the grinding wheel 16 slides horizontally along the workpiece 11, and the side surface of the grinding wheel 20 is pressed against the side surface 21b of the recess 21 formed in the workpiece 11 (see Figures 6(A) and 6(B)). Consequently, the remaining ungrinded area 23 (see Figures 6(A) and 6(B)) on the workpiece 11 is ground from the side surface 21b of the recess toward the side surface 11c of the workpiece 11.
[0057] The rotational speeds of the chuck table 4 and the grinding wheel 16 may be the same as or different from those in the recess formation step S2. For example, the rotational speed of the chuck table 4 is set to 100 rpm or more and 300 rpm or less, and the rotational speed of the grinding wheel 16 (rotational speed of the spindle 12) is set to 2000 rpm or more and 6000 rpm or less. In addition, the relative movement speed (machining feed rate) of the chuck table 4 and the grinding wheel 16 in the X-axis direction is set to, for example, 0.5 mm / s or more and 5 mm / s or less.
[0058] When the relative movement distance between the chuck table 4 and the grinding wheel 16 reaches the width of the ungrinding area 23 (see Figures 6(A) and 6(B)), the ungrinding area 23 is removed, and the outer circumference of the workpiece 11 is thinned. As a result, as shown in Figures 7(A) and 7(B), the back surface 11b of the workpiece 11 becomes flat, and the overall thickness of the workpiece 11 becomes the finished thickness.
[0059] As described above, in the slide grinding step S3, the grinding wheel 16 is slid horizontally along the workpiece 11 to remove the unground area 23 surrounding the recess 21 by grinding it along the radial direction (XY plane direction) rather than the thickness direction (Z axis direction) of the workpiece 11. This prevents a large load from being placed on the outer circumference of the thinned workpiece 11 in the thickness direction during the process of removing the unground area 23. As a result, the occurrence of chipping and cracking on the outer circumference of the workpiece 11 is suppressed, and damage to the outer circumference of the workpiece 11 can be avoided.
[0060] Subsequently, by dividing the workpiece 11 along the street 13 (see Figure 3), the device region 17 (see Figure 3) of the workpiece 11 is separated into individual pieces, and a thin device chip equipped with the device 15 (see Figure 3) is obtained. Various processing devices can be used to divide the workpiece 11, such as a cutting device that cuts the workpiece 11 with an annular cutting blade, or a laser processing device that performs laser processing on the workpiece 11.
[0061] As described above, in the workpiece grinding method according to this embodiment, the workpiece 11 is ground with the grinding wheel 20 to form a recess 21 in the workpiece 11 while leaving an unground area 23 on the outer circumference of the workpiece 11, and then the unground area 23 is ground with the grinding wheel 20 to thin the workpiece 11 while preventing damage to the outer circumference of the workpiece 11. As a result, edge trimming, which involves cutting the outer circumference of the workpiece 11 with a cutting blade, can be omitted, and the processing steps for the workpiece 11 are simplified.
[0062] In the above embodiment, an example was described in which the recess formation step S2 and the slide grinding step S3 are performed once each to bring the thickness of the workpiece 11 to the finish thickness. However, the workpiece 11 may also be ground by performing the recess formation step S2 and the slide grinding step S3 multiple times. Specifically, after grinding the entire workpiece 11 by a predetermined amount by performing the recess formation step S2 and the slide grinding step S3, the recess formation step S2 and the slide grinding step S3 are performed again on the same workpiece 11. By repeating this process, the workpiece 11 is thinned until it reaches the finish thickness.
[0063] As described above, by performing the recess formation step S2 and the slide grinding step S3 in multiple steps, the height (volume) of the ungrinded area 23 removed in a single slide grinding step S3 is reduced. This reduces the load on the outer circumference of the workpiece 11 during the slide grinding step S3.
[0064] Furthermore, in the above embodiment, an example was described in which the chuck table 4 and the grinding wheel 16 are moved relative to each other along the horizontal direction (X-axis direction) in the slide grinding step S3. However, instead of the slide grinding step S3, a slide grinding step S3' may be performed in which the chuck table 4 and the grinding wheel 16 are moved relative to each other along a direction inclined with respect to the horizontal direction.
[0065] Figure 8(A) is a partial cross-sectional side view showing the grinding apparatus 2 in slide grinding step S3', and Figure 8(B) is a perspective view showing the grinding apparatus 2 in slide grinding step S3'. Slide grinding step S3' corresponds to a modified example of slide grinding step S3. In slide grinding step S3', the grinding wheel 16 is moved relative to the outer peripheral edge (side surface 11c side) of the workpiece 11, while the grinding wheel 16 is moved relative to the bottom surface 21a of the recess 21.
[0066] Specifically, while maintaining the rotation of the chuck table 4 and the grinding wheel 16, the chuck table 4 is moved along the X-axis direction by a moving unit (not shown), and the grinding unit 10 is raised along the Z-axis direction by a moving unit (not shown). As a result, the chuck table 4 and the grinding wheel 16 move relative to each other along the X-axis and Z-axis directions, and the grinding wheel 16 moves relative to the chuck table 4 in an oblique upward direction. Consequently, the grinding wheel 20 grinds the ungrinded area 23 while moving away from the bottom surface 21a of the recess 21 (see Figures 6(A) and 6(B)).
[0067] The rotational speeds of the chuck table 4 and the grinding wheel 16, and the relative movement speed (first machining feed rate) between the chuck table 4 and the grinding wheel 16 in the X-axis direction can be set in the same way as in the slide grinding step S3. The relative movement speed (second machining feed rate) between the chuck table 4 and the grinding wheel 16 in the Z-axis direction is set to, for example, 0.1 μm / s or more and 5 μm / s or less. Furthermore, the relative movement distance (amount of upward movement of the grinding wheel 16) between the chuck table 4 and the grinding wheel 16 in the Z-axis direction is set to, for example, 0.5 μm or more and 10 μm or less.
[0068] As described above, when grinding the ungrinded area 23 while keeping the grinding wheel 20 away from the bottom surface 21a of the recess 21, the grinding wheel 20 does not come into contact with the bottom surface 21a of the recess 21 during grinding of the ungrinded area 23. This prevents the formation of numerous machining marks (saw marks) on the bottom surface 21a of the recess 21 in random directions, thereby suppressing a decrease in the mechanical strength of the workpiece 11.
[0069] Furthermore, prior to the recess formation step S2, a pre-grinding step may be performed to thin the entire workpiece 11 by grinding it. Figure 9(A) is a partial cross-sectional side view showing the grinding apparatus 2 in the pre-grinding step, and Figure 9(B) is a perspective view showing the grinding apparatus 2 in the pre-grinding step.
[0070] For example, grinding apparatus 2 includes grinding unit 30 in addition to grinding unit 10 (see Figure 1). Grinding unit 30 includes a spindle 32 and a wheel mount 34, and the spindle 32 rotates around a rotation axis 32a set along the Z-axis direction. The configuration and function of the spindle 32 and wheel mount 34 are the same as those of the spindle 12 and wheel mount 14 of grinding unit 10 (see Figure 1). However, the diameter of wheel mount 34 is larger than the diameter of wheel mount 14.
[0071] A grinding wheel 36 is mounted on the wheel mount 34. The grinding wheel 36 comprises an annular wheel base 38 and a plurality of grinding wheels 40 fixed to the wheel base 38. The lower surface of the grinding wheels 40 constitutes a grinding surface 40a for grinding the workpiece 11. When the spindle 32 is rotated, the grinding wheel 36 rotates around the rotation axis 32a, and the plurality of grinding wheels 40 each revolve along an annular trajectory (path) centered on the rotation axis 32a.
[0072] The configuration and function of the grinding wheel 36, wheel base 38, and grinding wheel 40 are the same as those of the grinding wheel 16, wheel base 18, and grinding wheel 20 (see Figure 1). However, the diameter of the wheel base 38 is larger than the diameter of the wheel base 18, and the diameter of the raceway of the grinding wheel 40 is larger than the diameter of the raceway of the grinding wheel 20.
[0073] For example, the pre-grinding step is performed after the holding step S1 (see Figures 5(A) and 5(B)) and before the recess formation step S2 (see Figures 6(A) and 6(B)). That is, the workpiece 11 held by the chuck table 4 is ground with the grinding wheel 40 of the grinding wheel 36.
[0074] In the pre-grinding step, the positional relationship between the chuck table 4 and the grinding wheel 36 is first adjusted. Specifically, the chuck table 4 is moved along the X-axis using a moving unit (not shown) to position it so that the center of the workpiece 11 and the trajectory of the grinding wheel 40 coincide in the Z-axis direction. The diameter of the trajectory of the grinding wheel 40 is set to be greater than or equal to the radius of the workpiece 11. Therefore, multiple grinding wheels 40 are arranged so as to coincide with the arc-shaped region from the center to the outer edge of the workpiece 11.
[0075] Next, with the chuck table 4 and grinding wheel 36 rotating, the chuck table 4 and grinding wheel 36 are moved relative to each other along a direction parallel to the rotation axis 32a (Z-axis direction). This causes the back surface 11b of the workpiece 11 to be ground by the grinding wheel 40.
[0076] Specifically, first, the chuck table 4 is rotated around the rotation axis 4c, and the grinding wheel 36 is rotated around the rotation axis 32a. Next, the grinding unit 30 is lowered along the Z-axis direction by a moving unit (not shown). As a result, the chuck table 4 and the grinding wheel 36 move relative to each other along a direction parallel to the rotation axis 32a (Z-axis direction), bringing the workpiece 11 and the grinding wheel 40 closer together. When the grinding wheel 40 contacts the workpiece 11, the grinding wheel 40 rotates to pass the rotation axis 4c of the chuck table 4, grinding the entire back surface 11b of the workpiece 11. This thins the entire workpiece 11.
[0077] When the thickness of the workpiece 11 reaches a predetermined target value, the grinding unit 30 rises and the grinding wheel 40 moves away from the workpiece 11. This completes the grinding of the workpiece 11 by the grinding wheel 36. Note that the grinding of the workpiece 11 in the pre-grinding step is stopped before the outer circumference of the workpiece 11 becomes sharp-edged and cracks or chips occur on the outer circumference of the workpiece 11.
[0078] Performing the pre-grinding step thins the entire workpiece 11. This reduces the amount of material removed from the central part of the workpiece 11 in the recess formation step S2 and from the outer periphery of the workpiece 11 in the slide grinding step S3.
[0079] The grinding device 2 may be equipped with two or more chuck tables 4. In this case, the chuck table 4 that holds the workpiece 11 in the pre-grinding step and the chuck table 4 that holds the workpiece 11 in the recess formation step S2 and the slide grinding step S3 may be different chuck tables. The pre-grinding step may also be performed by another grinding device prepared separately from the grinding device 2. In the above case, the pre-grinding step is performed before the holding step S1.
[0080] Furthermore, the structures, methods, etc., according to the above embodiments can be modified as appropriate without departing from the scope of the objectives of the present invention. [Explanation of symbols]
[0081] 11 Workpiece 11a Surface (first side) 11b Back side (2nd side) 11c Side (chamfered part) 13th Street (planned division line) 15 devices 17 Device Areas 19. Peripheral surplus area 21 Recess (groove) 21a Bottom 21b Side (side wall, inner wall) 23 Unground area (protruding part) 2. Grinding device 4. Chuck table (holding table) 4a Holding surface 4b Holding area 4c rotation axis 6. Frame (main body) 6a Top side 6b recess 6c channel 8 Retaining member 8a Suction surface 10 Grinding Units 12 spindles 12a Rotation axis 14 Wheel Mount 16 grinding wheels 18 Wheel base 20 grinding wheels 20a Grinding surface 30 Grinding Units 32 spindles 32a Rotation axis 34 Wheel Mount 36 grinding wheels 38 Wheel base 40 grinding wheels 40a Grinding surface
Claims
1. A method for grinding a workpiece having a chamfered portion on its outer circumference using a grinding wheel that includes a grinding wheel, A holding step of holding the workpiece with a chuck table, After the holding step, with the chuck table and the grinding wheel rotating, the chuck table and the grinding wheel are moved relative to each other along a direction parallel to the rotation axis of the grinding wheel, thereby grinding the workpiece with the grinding wheel to form a recess in the workpiece while leaving an unground area on the outer circumference of the workpiece; A method for grinding a workpiece, characterized by comprising: a sliding grinding step, after the recess forming step, the chuck table and the grinding wheel are rotated, and the chuck table and the grinding wheel are moved relative to each other along a direction intersecting the rotation axis of the grinding wheel, thereby grinding the ungrinded area with the grinding wheel.
2. The method for grinding a workpiece according to claim 1, further comprising a pre-grinding step of grinding the workpiece to thin the entire workpiece before the recess-forming step.
3. The method for grinding a workpiece according to claim 1 or 2, characterized in that, in the slide grinding step, the grinding wheel is moved relative to the outer edge of the workpiece while the grinding wheel is moved relative to the bottom surface of the recess.
4. The method for grinding a workpiece according to claim 1 or 2, characterized in that the workpiece is ground by performing the recess forming step and the slide grinding step multiple times.