TW202446555A - Grinding method of workpiece - Google Patents

Abstract

This invention is to provide a workpiece grinding method that can suppress the occurrence of processing defects. The solution is a workpiece grinding method that grinds a workpiece having a first surface and a second surface, and comprises: a holding step for holding a first surface side of the workpiece by a holding surface of a chuck table; a first grinding step for grinding a part of a second surface side of the workpiece to thin a first region of the workpiece while leaving an unground second region on the workpiece; and a second grinding step for grinding the second region of the workpiece and stopping the grinding of the workpiece after detecting that the first region and the second region have become the same thickness.

Description

Grinding method of workpiece

The present invention relates to a method for grinding a workpiece, which grinds a workpiece such as a wafer or a package substrate.

By dividing a wafer with multiple components into individual pieces, a component chip having components is manufactured. In addition, multiple component chips are mounted on a predetermined substrate, and the mounted component chips are covered and sealed with a resin layer (sealing resin) to form a package substrate. By dividing this package substrate into individual pieces, a packaged component having multiple packaged component chips is manufactured. Component chips or packaged components are installed in various electronic devices such as mobile phones and personal computers.

In recent years, as electronic devices become smaller, thinning of component chips or packaged components is required. Therefore, a grinding device is sometimes used to grind and thin wafers or package substrates before being divided. The grinding device includes: a chuck table that holds the workpiece; and a grinding unit that grinds the workpiece. A spindle is built into the grinding unit, and a ring-shaped grinding wheel with a plurality of grinding stones is installed at the front end of the spindle. The workpiece is held by the chuck table, and the grinding stones are brought into contact with the grinding surface of the workpiece while the chuck table and the grinding wheel are rotated, thereby grinding and thinning the workpiece (see Patent Document 1). [Known Technical Document] [Patent Document]

[Patent Document 1] Japanese Patent Application Publication No. 2014-124690

[Problems to be solved by the invention] When grinding a workpiece using a grinding device, if the grinding stone of the grinding wheel is brought into contact with the entire grinding surface of the workpiece, the contact area between the workpiece and the grinding stone increases, and the pressure (grinding load) applied to the workpiece and the grinding wheel during grinding increases. Then, if the grinding load increases, there is a concern that the temperature of the contact area between the workpiece and the grinding stone rises excessively, causing a phenomenon called surface sintering, in which the grinding surface of the workpiece is sintered, or that damage such as cracking occurs on the grinding surface side of the workpiece. Especially when grinding hard workpieces such as SiC wafers, GaN wafers, and sapphire wafers, processing defects are easily caused by the increase in grinding load.

Therefore, sometimes a method is used to reduce the grinding load by dividing the workpiece into multiple sections for grinding. For example, first, only the peripheral part of the workpiece is ground and thinned in such a way that the center of the workpiece is not ground and the original thickness is left. Then, the remaining center of the workpiece is ground until it becomes the same thickness as the peripheral part. In this way, by dividing the workpiece into multiple areas and grinding them individually, the grinding load is reduced and the occurrence of processing defects is suppressed.

When grinding a workpiece in multiple regions as described above, the grinding conditions are set so that the grinding amount (thickness difference before and after grinding) in each region becomes equal. However, due to the deviation of the wear amount of the grinding grindstone, the change of the grinding grindstone condition, etc., the grinding amount in each region may also vary. As a result, abnormalities may occur such as stopping grinding before the thickness of each region is consistent or continuing grinding for an unexpectedly long time after the thickness of each region is consistent. Such abnormalities may become the cause of new processing defects.

The present invention is made in view of this problem, and an object of the present invention is to provide a method for grinding a workpiece, which can suppress the occurrence of machining defects.

[Technical means for solving the problem] According to one aspect of the present invention, a method for grinding a workpiece is provided, wherein the workpiece includes a first surface and a second surface, and comprises: a holding step, wherein the first surface side of the workpiece is held by a holding surface of a chuck table; a first grinding step, wherein after the holding step, a portion of the second surface side of the workpiece is ground to thin the first area of the workpiece while leaving an unground second area on the workpiece; and a second grinding step, wherein after the first grinding step, the second area of the workpiece is ground, and the grinding of the workpiece is stopped after it is detected that the first area and the second area have the same thickness.

In addition, preferably, in the second grinding step, while measuring a value corresponding to a grinding load applied when grinding the workpiece, the workpiece is ground, and based on a change in the value corresponding to the grinding load, it is detected that the first region and the second region have the same thickness. In addition, preferably, in the second grinding step, while measuring the thickness of the workpiece in the first region and the second region with a thickness gauge, the workpiece is ground, and based on the value measured by the thickness gauge, it is detected that the first region and the second region have the same thickness.

Furthermore, preferably, in the second grinding step, after detecting that the first region and the second region have the same thickness, the first region and the second region are ground by a predetermined amount, and then the grinding of the workpiece is stopped.

[Effect of the invention] In a method for grinding a workpiece according to one aspect of the present invention, a portion of the workpiece is ground to thin the first area, while leaving the unground second area, and then the second area of the workpiece is ground. After detecting that the first area and the second area have the same thickness, the grinding of the workpiece is stopped. In this way, abnormalities such as stopping the grinding before the first area and the second area have the same thickness or continuing the grinding for an unexpectedly long time after the first area and the second area have the same thickness can be avoided, thereby suppressing the occurrence of processing defects.

(Implementation method 1) The following describes an implementation method of one aspect of the present invention with reference to the accompanying drawings. First, an example of the structure of a grinding device that can be used to implement the method for grinding a workpiece of the present implementation method is described. FIG. 1 is a partial cross-sectional side view of a grinding device 2. In addition, in FIG. 1, the so-called X-axis direction (first horizontal direction, front-back direction) and the Y-axis direction (second horizontal direction, left-right direction) are directions perpendicular to each other. In addition, the Z-axis direction (height direction, up-down direction, vertical direction) is a direction perpendicular to the X-axis direction and the Y-axis direction.

The grinding device 2 has a base 4 that supports or accommodates the components constituting the grinding device 2. A rectangular opening 4a is provided on the upper surface side of the base 4. A chuck table (holding table) 6 is provided inside the opening 4a, and the chuck table (holding table) 6 holds the object to be ground by the grinding device 2, that is, the workpiece. The upper surface of the chuck table 6 constitutes a holding surface 6a for holding the workpiece.

FIG. 2 is a cross-sectional view showing the chuck table 6. The chuck table 6 has a cylindrical frame (main body) 8 made of metal such as SUS (stainless steel), glass, ceramics, resin, etc. A cylindrical recess 8b is provided in the central portion of the upper surface 8a side of the frame 8 in a concentric circle with the upper surface 8a. In addition, a disc-shaped retaining member 10 made of a porous material such as porous ceramics is embedded in the recess 8b. The retaining member 10 includes a plurality of pores connected from the upper surface of the retaining member 10 to the lower surface. The upper surface of the retaining member 10 is formed into a circular suction surface 10a for attracting the workpiece when the workpiece is held by the chuck table 6.

The holding surface 6a of the chuck table 6 is formed by the upper surface 8a of the frame 8 and the suction surface 10a of the holding member 10. The holding surface 6a is connected to a suction source (not shown) such as an ejector through air holes included in the holding member 10, a flow path 8c provided inside the frame 8, a valve (not shown), and the like.

The holding surface 6a of the chuck table 6 is formed into a cone shape with the center of the holding surface 6a as the vertex, and is slightly inclined relative to the radial direction of the holding surface 6a. Then, the chuck table 6 is arranged in a slightly inclined state in such a way that a holding area 6b corresponding to a part of the holding surface 6a and extending from the center to the outer periphery of the holding surface 6a is substantially parallel to the horizontal plane (XY plane). The area held by the holding area 6b or the area near it in the workpiece is ground by the grinding unit 44 described later.

In addition, for the sake of convenience of explanation, the inclination of the holding surface 6a is exaggerated in FIG2 , but the actual inclination of the holding surface 6a is smaller. For example, when the diameter of the holding surface 6a is about 290 mm or more and 310 mm or less, the height difference between the center and the outer periphery of the holding surface 6a (equivalent to the height of the cone) is set to about 20 μm or more and 40 μm or less.

The chuck table 6 is connected to a rotation drive source (not shown) such as a motor that rotates the chuck table 6 around a rotation axis 12. The rotation axis 12 is set in a direction perpendicular to the radial direction of the holding surface 6a and is slightly inclined with respect to the Z-axis direction. In addition, the rotation axis 12 intersects the holding surface 6a in a manner that passes through the center of the holding surface 6a.

As shown in FIG1 , a tilt adjustment mechanism 14 for adjusting the tilt of the chuck table 6 is connected to the chuck table 6. For example, the tilt adjustment mechanism 14 includes: a disk-shaped table base 16 that supports the chuck table 6 through a bearing (not shown); and a fixed support member 18A and two movable support members 18B that support the table base 16. In addition, FIG1 only shows the movable support member 18B on one side, and omits the movable support member 18B on the other side.

One fixed support member 18A and two movable support members 18B are arranged at substantially equal intervals (120° intervals) along the circumferential direction of the table base 16. The upper ends of the fixed support member 18A and the movable support member 18B are fixed to the lower surface side of the outer peripheral portion of the table base 16, respectively.

The fixed support member 18A is configured so that the upper end is fixed at a predetermined height position. On the other hand, the movable support member 18B is configured so that the upper end can be moved (raised and lowered) along the Z-axis direction. By inputting a control signal from a controller 62 described later to the movable support member 18B, the position (height position) of the upper end of the two movable support members 18B in the Z-axis direction can be changed respectively. In this way, the inclination of the chuck table 6 and the rotating shaft 12 is adjusted.

A moving mechanism (moving unit) 20 is provided on the inner side of the base 4. The moving mechanism 20 is connected to the chuck table 6 so that the chuck table 6 moves along the X-axis direction. Specifically, the moving mechanism 20 has a ball screw 22 arranged along the X-axis direction. A pulse motor 24 that rotates the ball screw 22 is connected to the end of the ball screw 22. The chuck table 6 and the tilt adjustment mechanism 14 are supported by a support table 26. A nut portion 28 is connected to the support table 26, and the ball screw 22 is screwed with the nut portion 28. If the ball screw 22 is rotated by the pulse motor 24, the chuck table 6 moves along the X-axis direction.

A rectangular support structure (column) 30 is provided behind the chuck table 6 and the moving mechanism 20 (right side in FIG. 1 ). A moving mechanism (moving unit) 32 is provided on the front side (front surface side) of the support structure 30. The moving mechanism 32 has a pair of guide rails 34 fixed to the front side of the support structure 30. The pair of guide rails 34 are arranged along the Z-axis direction and are separated from each other in the Y-axis direction.

The holding member 36 formed in a hollow cylindrical shape is mounted on the pair of guide rails 34 so as to slide along the guide rails 34. A nut portion 38 is connected to the back side of the holding member 36, and a ball screw 40 arranged along the Z-axis direction between the pair of guide rails 34 is screwed with the nut portion 38. In addition, a pulse motor 42 for rotating the ball screw 40 is connected to the end of the ball screw 40. When the pulse motor 42 rotates the ball screw 40, the holding member 36 moves (rises and falls) along the guide rail 34 in the Z-axis direction.

The holding member 36 holds a grinding unit 44 that performs grinding processing on a workpiece. The grinding unit 44 has a cylindrical housing 46 accommodated in the holding member 36. The lower surface side of the housing 46 is supported by the bottom surface of the holding member 36 through a buffer member 48 made of an elastic body such as rubber.

The cylindrical spindle 50 arranged along the Z-axis direction is accommodated in the housing 46. The front end (lower end) of the spindle 50 is exposed from the housing 46, and protrudes downward from the lower surface of the holding member 36 through an opening provided at the bottom of the holding member 36. In addition, a rotation drive source (not shown) such as a motor that rotates the spindle 50 is connected to the base end (upper end) of the spindle 50.

A disc-shaped wheel seat 52 made of metal or the like is fixed to the front end of the spindle 50. A ring-shaped grinding wheel 54 for grinding a workpiece is detachably mounted on the lower surface side of the wheel seat 52. For example, the grinding wheel 54 is fixed to the wheel seat 52 by a fixing device such as a bolt.

The grinding wheel 54 has a ring-shaped wheel base 56. The wheel base 56 is made of metal such as aluminum and stainless steel and is formed to have substantially the same diameter as the wheel seat 52. The upper surface side of the wheel base 56 is fixed to the lower surface side of the wheel seat 52.

A plurality of grinding stones 58 are fixed to the lower surface of the wheel base 56. For example, the grinding stones 58 are formed into a rectangular parallelepiped shape and are arranged in a ring shape at approximately equal intervals along the circumferential direction of the wheel base 56. The grinding stones 58 include abrasive grains composed of diamond, cBN (cubic boron nitride), etc., and a bonding material (bonding material) such as a metal bonding agent, a resin bonding agent, and a ceramic bonding agent for fixing the abrasive grains. However, the material, shape, structure, size, etc. of the grinding stones 58 are not limited. In addition, the number of grinding stones 58 can also be set arbitrarily.

The grinding wheel 54 rotates around a rotation axis 60 provided along the Z-axis direction by power transmitted from a rotation drive source (not shown) through the main shaft 50 and the wheel base 52. That is, the rotation axis 60 corresponds to the rotation axis of the main shaft 50, the wheel base 52, and the grinding wheel 54. When the grinding wheel 54 is rotated, the plurality of grinding stones 58 rotate along an annular path (rotation track, convolute track) substantially parallel to the horizontal plane (XY plane) with the rotation axis 60 as the center.

A grinding liquid supply path (not shown) for supplying a liquid such as pure water (grinding liquid) is provided inside or near the grinding unit 44. For example, the grinding liquid supply path is formed by a flow path formed inside the wheel seat 52 and the grinding wheel 54, and a nozzle provided near the grinding unit 44. While the workpiece is being ground by the grinding wheel 54, the grinding liquid is supplied to the workpiece and the grinding stone 58. In this way, the workpiece and the grinding stone 58 are cooled, and the debris (grinding chips) generated by the grinding process are washed away.

Furthermore, the grinding device 2 has a controller (control unit, control section, control device) 62 for controlling the grinding device 2. The controller 62 is connected to the components of the grinding device 2 (chuck table 6, tilt adjustment mechanism 14, moving mechanism 20, moving mechanism 32, grinding unit 44, etc.), and generates a control signal for controlling the operation of each component.

For example, the controller 62 is composed of a computer. Specifically, the controller 62 includes: a calculation unit that performs calculations required for the operation of the grinding device 2; and a memory unit that stores various information (data, programs, etc.) used to operate the grinding device 2. The calculation unit is composed of a processor such as a CPU (Central Processing Unit). The memory unit is composed of a memory such as a ROM (Read Only Memory) and a RAM (Random Access Memory).

Next, a specific example of the method for grinding a workpiece according to the present embodiment will be described. Fig. 3 is a flow chart showing the method for grinding a workpiece. In the present embodiment, a case where a circular workpiece is ground using the grinding device 2 will be described.

When the grinding device 2 grinds the workpiece, first, the workpiece is held by the holding surface 6a of the chuck table 6 (holding step S1). FIG. 4 is a perspective view of the grinding device 2 in the holding step S1. In the holding step S1, the chuck table 6 holds the object of grinding by the grinding device 2, that is, the circular workpiece 11.

The workpiece 11 is a disc-shaped substrate (wafer) made of semiconductors (Si, GaAs, InP, GaN, SiC, etc.), sapphire, glass, ceramics, resin, metal, etc., and includes a first surface (front surface) 11a and a second surface (back surface) 11b that are substantially parallel to each other. For example, the workpiece 11 is divided into a plurality of rectangular regions by a plurality of cutting paths (predetermined dividing lines) arranged in a grid-like manner in a mutually intersecting manner. On the first surface 11a side of the plurality of regions divided by the cutting paths, components such as IC (Integrated Circuit), LSI (Large Scale Integration), LED (Light Emitting Diode), and MEMS (Micro Electro Mechanical Systems) components (not shown) are formed.

By dividing the workpiece 11 along the dicing line, a plurality of chips (component chips) each having a component are manufactured. The workpiece 11 is divided by using a cutting device that cuts the workpiece 11 with a ring-shaped cutting blade, a laser processing device that performs laser processing on the workpiece 11, etc. In addition, before dividing the workpiece 11, the second surface 11b side of the workpiece 11 is ground in advance by a grinding device 2 to thin the workpiece 11, thereby obtaining a thinned component chip.

However, there is no limitation on the type, material, shape, structure, size, etc. of the workpiece 11. There is no limitation on the type, number, shape, structure, size, arrangement, etc. of the elements, and the workpiece 11 may not have elements formed thereon.

For example, the workpiece 11 is arranged on the chuck table 6 in such a manner that the first surface 11a side faces the holding surface 6a and the second surface 11b side (grinding surface side) is exposed upward. At this time, the workpiece 11 is positioned in such a manner that the entire suction surface 10a is covered by the workpiece 11 and the rotation axis 12 of the chuck table 6 passes through the center of the workpiece 11. In this state, if the suction force (negative pressure) of the suction source is applied to the suction surface 10a, the first surface 11a side of the workpiece 11 is sucked and held by the holding surface 6a.

In addition, a sheet (protective sheet) for protecting the workpiece 11 may be attached to the first surface 11a of the workpiece 11. For example, a film including a film-like substrate and an adhesive layer (paste) provided on the substrate is used as the protective sheet. Furthermore, the protective sheet may be a heat-pressed sheet that does not contain an adhesive layer and can be heat-pressed to the workpiece 11. When the protective sheet is attached to the first surface 11a of the workpiece 11, the workpiece 11 is held by the chuck table 6 via the protective sheet.

As mentioned above, the holding surface 6a of the chuck table 6 is strictly formed into a cone shape (see FIG. 2). Then, if the workpiece 11 is attracted by the suction surface 10a, the workpiece 11 is held in a slightly bent and deformed state along the holding surface 6a. As a result, the held area 6b (see FIG. 2) or the area near the held area of the workpiece 11 is arranged to be roughly parallel to the horizontal plane (XY plane).

Next, by grinding a portion of the second surface 11b side of the workpiece 11, the first region of the workpiece 11 is thinned while the unground second region remains on the workpiece 11 (first grinding step S2). FIG. 5(A) is a perspective view of the grinding device 2 in the first grinding step S2, and FIG. 5(B) is a cross-sectional view of the grinding device 2 in the first grinding step S2.

In the first grinding step S2, first, the positional relationship between the chuck table 6 and the grinding wheel 54 is adjusted. Specifically, with the grinding unit 44 disposed above the chuck table 6, the chuck table 6 is moved along the X-axis direction by the moving mechanism 20 (see FIG. 1 ), and the chuck table 6 is positioned in such a manner that the rotation track of the grinding stone 58 overlaps a portion of the workpiece 11 in the Z-axis direction.

For example, the workpiece 11 includes: an annular first area (peripheral area) 13, which includes the outer periphery of the workpiece 11; and a circular second area (center area) 15, which includes the center of the workpiece 11. The first area 13 is equivalent to an area within a predetermined range from the outer periphery of the workpiece 11. And, the second area 15 is equivalent to an area within a predetermined range from the center of the workpiece 11. The second area 15 is surrounded by the first area 13, and the sum of the width of the first area 13 and the radius of the second area 15 is equivalent to the radius of the workpiece 11. Then, the positional relationship between the chuck table 6 and the grinding wheel 54 is adjusted in such a way that the grinding stone 58 overlaps with the first area 13 of the workpiece 11 but does not overlap with the second area 15.

Next, the chuck table 6 is rotated around the rotation axis 12, and the grinding wheel 54 is rotated around the rotation axis 60. For example, the rotation speed of the chuck table 6 is set to 100 rpm or more and 900 rpm or less, and the rotation speed of the grinding wheel 54 (the rotation speed of the spindle 50) is set to 1000 rpm or more and 7000 rpm or less.

Then, the grinding unit 44 is lowered along the Z-axis direction by the moving mechanism 32 (see FIG. 1 ). As a result, the chuck table 6 and the grinding wheel 54 move relative to each other in a direction parallel to the rotation axis 60 (Z-axis direction), and the grinding stone 58 approaches and contacts the workpiece 11 while rotating. The relative moving speed of the chuck table 6 and the grinding wheel 54 in the Z-axis direction at this time is equivalent to the processing feed speed. The processing feed speed is set to, for example, 1 μm/s or more and 6 μm/s or less.

The grinding stone 58 contacts only the first area 13 of the workpiece 11, but does not contact the second area 15 of the workpiece 11. As a result, the second surface 11b side of the first area 13 of the workpiece 11 is ground to thin the first area 13. On the other hand, the second area 15 of the workpiece 11 is not ground or thinned, but remains as a circular unground area with the original thickness. As a result, an annular step portion 11c corresponding to the side surface of the second area 15 is formed at the boundary between the first area 13 and the second area 15.

As described above, in the first grinding step S2, the grinding stone 58 is brought into contact with the workpiece 11 in a state where the rotation path of the grinding stone 58 does not overlap with the center of the workpiece 11. In this way, a portion (the first area 13) of the workpiece 11 can be ground and thinned, while the other area (the second area 15) of the workpiece 11 is left as an unground area where grinding is not performed. In this way, by grinding only the first area 13 of the workpiece 11, the grinding load is reduced compared to the case where the entire workpiece 11 is ground. In addition, the grinding load is equivalent to the pressure applied to the workpiece 11 and the grinding wheel 54 during grinding.

When the first area 13 of the workpiece 11 is ground to a predetermined thickness, the grinding unit 44 rises and the grinding stone 58 is separated from the workpiece 11. Thus, the grinding of the workpiece 11 by the grinding stone 58 is interrupted. In addition, by maintaining the rotation of the chuck table 6 and the grinding wheel 54 in advance during the separation of the grinding stone 58 from the workpiece 11, the grinding of the workpiece 11 can be smoothly restarted in the subsequent second grinding step S3.

Next, the second region 15 of the workpiece 11 is ground, and when it is detected that the first region 13 and the second region 15 have the same thickness, the grinding of the workpiece 11 is stopped (second grinding step S3). FIG6 is a perspective view of the grinding device 2 in the second grinding step S3.

In the second grinding step S3, first, the positional relationship between the chuck table 6 and the grinding wheel 54 is adjusted. Specifically, the chuck table 6 is moved along the X-axis direction by the moving mechanism 20 (see FIG. 1 ), and the chuck table 6 is positioned in such a manner that the rotation track of the grinding stone 58 overlaps with the center of the workpiece 11 in the Z-axis direction. Thereby, the grinding stone 58 is arranged to overlap with the second area 15 (unground area) of the workpiece 11. In addition, the diameter of the rotation track of the grinding stone 58 is at least larger than the radius of the second area 15. Therefore, the grinding stone 58 is arranged to overlap with the arc-shaped area from the center of the second area 15 to the step portion 11c.

Next, the chuck table 6 is rotated around the rotation axis 12, and the grinding wheel 54 is rotated around the rotation axis 60. For example, the rotation speed of the chuck table 6 is set to 100 rpm or more and 900 rpm or less, and the rotation speed of the grinding wheel 54 (the rotation speed of the spindle 50) is set to 1000 rpm or more and 7000 rpm or less.

Then, the grinding unit 44 is lowered in the Z-axis direction by the moving mechanism 32 (see FIG. 1 ). As a result, the chuck table 6 and the grinding wheel 54 move relatively in the direction parallel to the rotation axis 60 (Z-axis direction), and the grinding stone 58 approaches and contacts the workpiece 11 while rotating. In addition, the processing feed speed is set to, for example, 1 μm/s or more and 6 μm/s or less.

The grinding stone 58 is in contact with the second surface 11b of the second region 15 of the workpiece 11 while rotating through the rotating shaft 12. The second region 15 of the workpiece 11 is thereby ground and thinned. Then, when the second region 15 is ground to the same thickness as the first region 13, the step portion 11c disappears and the thickness of the entire workpiece 11 is uniform. In this way, by grinding only the second region 15 of the workpiece 11, the grinding load is reduced compared to the case of grinding the entire workpiece 11.

Furthermore, in the second grinding step S3, after detecting that the first region 13 and the second region 15 have the same thickness, the grinding of the workpiece 11 is stopped. For example, in the second grinding step S3, while measuring a value corresponding to the grinding load applied when grinding the workpiece 11 (load corresponding value), the workpiece 11 is ground, and based on the change in the load corresponding value, it is detected that the first region 13 and the second region 15 have the same thickness.

Specifically, the grinding device 2 has a motor 64, which functions as a measuring device for measuring the load corresponding value. The motor 64 is a rotation drive source connected to the main shaft 50. If a control signal is input from the controller 62 (refer to FIG. 1 ) to the motor 64, the motor 64 is driven to rotate the main shaft 50, the wheel base 52, and the grinding wheel 54 around the rotating shaft 60. In addition, the current value of the motor 64 is successively input to the controller 62 and monitored by the controller 62.

When the grinding stone 58 contacts the workpiece 11, a load is applied to the grinding stone 58. As a result, the torque of the spindle 50 required to maintain the rotation of the grinding wheel 54 increases, and the current value of the motor 64 also increases. Furthermore, the larger the contact area between the workpiece 11 and the grinding stone 58 becomes, the greater the grinding load becomes, and the current value of the motor 64 also increases. Therefore, the current value of the motor 64 is equivalent to the load corresponding value.

Furthermore, the grinding device 2 is provided with load measuring devices 66 and 68, which function as measuring devices for measuring load corresponding values. The load measuring devices 66 and 68 are constituted by load cells, for example. The load measuring device 66 is connected to the chuck table 6, and measures the load applied to the chuck table 6. Furthermore, the load measuring device 68 is connected to the spindle 50, and measures the load applied to the spindle 50, the wheel seat 52, and the grinding wheel 54. The loads measured by the load measuring devices 66 and 68 are successively input to the controller 62 (refer to FIG. 1), and monitored by the controller 62.

If the grinding stone 58 contacts the workpiece 11, a load is applied to the chuck table 6 and the spindle 50, and the load measured by the load measuring devices 66 and 68 increases. Furthermore, the larger the contact area between the workpiece 11 and the grinding stone 58 becomes, the larger the grinding load becomes, and the load measured by the load measuring devices 66 and 68 also increases. Therefore, the load measured by the load measuring devices 66 and 68 is equivalent to the load corresponding value.

FIG. 7 (A) is a cross-sectional view of the grinding device 2 at the initial stage of the second grinding step S3. When the second grinding step S3 is started, the grinding stone 58 first contacts only the second area 15 (unground area) of the workpiece 11. At this time, the current value of the motor 64 and the load measured by the load measuring devices 66 and 68 increase. Thereafter, while the grinding stone 58 only grinds the second area 15, the current value of the motor 64 and the load measured by the load measuring devices 66 and 68 remain substantially constant.

FIG7(B) is a cross-sectional view of the grinding device 2 at the final stage of the second grinding step S3. When the second region 15 is ground to the same thickness as the first region 13, the grinding stone 58 contacts the first region 13 in addition to the second region 15, and the contact area between the workpiece 11 and the grinding stone 58 increases. As a result, the grinding load increases dramatically, and the current value of the motor 64 and the load measured by the load measuring devices 66 and 68 also increase.

FIG8 is a graph showing the relationship between the grinding time and the load corresponding value in the second grinding step S3. If the first region 13 and the second region 15 become the same thickness, the load corresponding value (the current value of the motor 64, the load measured by the load measuring devices 66 and 68) which has been maintained substantially constant until now will increase. Therefore, based on the change in the load corresponding value, it can be detected that the first region 13 and the second region 15 become the same thickness.

For example, a reference value (threshold value) V _ref of the load corresponding value is pre-stored in the memory of the controller 62 (see FIG. 1 ). The reference value V _ref is set to be a value higher than the load corresponding value when the grinding stone 58 is in contact with only the second area 15 (unground area) of the workpiece 11 by a predetermined amount. Then, the controller 62 compares the load corresponding value measured by the measuring device (motor 64, load measuring devices 66, 68) with the reference value V _ref .

When the load corresponding value is less than the reference value V _ref , the controller 62 determines that the grinding stone 58 is not in contact with the first region 13, and the second region 15 has not yet become the same thickness as the first region 13. On the other hand, when the load corresponding value is greater than the reference value V _ref , the controller 62 determines that the grinding stone 58 is in contact with the first region 13 and the second region 15, and the first region 13 and the second region 15 have become the same thickness.

As described above, the first region 13 and the second region 15 are detected to have the same thickness based on the change in the load corresponding value. However, the method for detecting that the first region 13 and the second region 15 have the same thickness is not limited. For example, the thickness of the first region 13 and the thickness of the second region 15 can be measured with a measuring device and compared to determine whether the first region 13 and the second region 15 have the same thickness.

Fig. 9 is a cross-sectional view showing the grinding device 2 measuring the thickness of the workpiece 11. The grinding device 2 may also include a measuring unit 70 for measuring the thickness of the workpiece 11 held by the chuck table 6. In this case, the grinding device 2 can grind the workpiece 11 while measuring the thickness of the workpiece 11 with the measuring unit 70.

For example, the measuring unit 70 includes: a cylindrical rotating support portion 72 arranged along the Z-axis direction; and a columnar support arm 74 connected to the rotating support portion 72. A rotating drive source (not shown) such as a motor that rotates the rotating support portion 72 around a rotating axis that is substantially parallel to the Z-axis direction is connected to the lower end of the rotating support portion 72. In addition, the support arm 74 is fixed to the upper end of the rotating support portion 72 and is arranged substantially parallel to the horizontal plane (XY plane).

A thickness gauge 76 for measuring the thickness of the workpiece 11 is installed at the front end of the support arm 74. The type of thickness gauge 76 is not limited, and for example, an optical interference thickness gauge or an ultrasonic thickness gauge can be used. In addition, the thickness gauge 76 is used to measure the thickness of the rotating workpiece 11, so it is preferably a non-contact thickness gauge that does not directly contact the workpiece 11.

When the rotary drive source (not shown) is driven to rotate the rotary support portion 72, the support arm 74 and the thickness gauge 76 rotate around the rotation axis of the rotary support portion 72. For example, the length of the support arm 74 and the mounting position of the thickness gauge 76 are adjusted so that the thickness gauge 76 rotates while passing through a position overlapping with the center of the holding surface 6a. In this way, the thickness gauge 76 can be reciprocated between a position overlapping with the center of the workpiece 11 and a position overlapping with the outer periphery of the workpiece 11.

Then, in the second grinding step S3, within the range where the grinding wheel 54 and the measuring unit 70 are not in contact, the thickness measuring device 76 is moved back and forth between the first area 13 and the second area 15 to measure the thickness of the workpiece 11. In this way, the thickness of the first area 13 and the second area 15 are alternately measured by the measuring unit 70. Then, the thickness of the first area 13 and the second area 15 measured by the measuring unit 70 are successively input to the controller 62 (refer to FIG. 1).

The controller 62 compares the thickness of the first region 13 measured by the measuring unit 70 with the thickness of the second region 15. Then, if the thickness of the first region 13 is the same as the thickness of the second region 15, or the difference between the two is less than a predetermined value, the controller 62 determines that the first region 13 and the second region 15 have the same thickness. In this way, it is also possible to detect that the first region 13 and the second region 15 have the same thickness based on the value measured by the thickness measuring device 76.

In addition, the configuration of the measuring unit 70 is not limited as long as it can measure the thickness of the workpiece 11 in the first area 13 and the second area 15. For example, the measuring unit 70 may also be provided with a thickness measuring device (first thickness measuring device) for measuring the thickness of the first area 13 and a thickness measuring device (second thickness measuring device) for measuring the thickness of the second area. In this case, the thickness of the first area 13 measured by the first thickness measuring device and the thickness of the second area 15 measured by the second thickness measuring device are respectively input to the controller 62 (refer to FIG. 1).

After detecting that the first area 13 and the second area 15 have the same thickness, a control signal is output from the controller 62 (see FIG. 1 ) to the moving mechanism 32 (see FIG. 1 ), and the grinding unit 44 rises. As a result, the grinding stone 58 is separated from the workpiece 11 , and the grinding of the workpiece 11 by the grinding stone 58 is stopped.

As described above, in the present embodiment, after grinding only the first area 13 of the workpiece 11 in the first grinding step S2, the remaining second area 15 is ground in the second grinding step S3. In this way, by dividing the workpiece 11 into a plurality of areas and grinding each area individually, the contact area between the workpiece 11 and the grinding grindstone 58 can be reduced, thereby reducing the grinding load. In this way, the occurrence of processing defects (surface sintering, cracking, etc.) that are easy to occur when the entire workpiece 11 is ground at one time is suppressed. In particular, when the workpiece 11 is a hard material (SiC wafer, GaN wafer, sapphire wafer, etc.), processing defects caused by increased grinding load are easy to occur, so it is better to use the grinding method of the present embodiment.

Furthermore, in the second grinding step S3, since it is detected that the first area 13 and the second area 15 of the workpiece 11 have the same thickness, the grinding of the workpiece 11 can be stopped at an appropriate time. In this way, it is possible to avoid abnormalities such as stopping the grinding before the first area 13 and the second area 15 have the same thickness or continuing the grinding for an unexpectedly long time after the first area 13 and the second area 15 have the same thickness, thereby suppressing the occurrence of processing defects.

Furthermore, in the second grinding step S3, after the first area 13 and the second area 15 are detected to have the same thickness, the grinding of the workpiece 11 may be stopped after the entire workpiece 11 (the first area 13 and the second area 15) is ground by a predetermined amount. Specifically, after the first area 13 and the second area 15 are detected to have the same thickness, the machining feed is continued while the rotation of the chuck table 6 and the grinding wheel 54 is maintained. In this way, the grinding marks (polishing marks) formed on the first area 13 of the workpiece 11 in the first grinding step S2 are removed, and random grinding marks can be avoided from remaining on the second surface 11b of the workpiece 11.

While the entire workpiece 11 is ground as described above, the grinding stone 58 contacts the first area 13 and the second area 15, thereby increasing the grinding load. However, the grinding amount of the workpiece 11 is suppressed to be small within the range of removing the grinding marks formed in the first grinding step S2. Therefore, processing defects that adversely affect the quality of the workpiece 11 do not occur. For example, after the first area 13 and the second area 15 are detected to have the same thickness, the grinding amount of the entire workpiece 11 is set to be less than 10μm, preferably less than 5μm.

Furthermore, in the present embodiment, an example is described in which the workpiece 11 is divided into two regions (the first region 13 and the second region 15) for grinding, but the workpiece 11 may be divided into three or more regions for grinding. In this case, after the first grinding step S2 is performed, the second grinding step S3 is performed on two or more different regions of the workpiece 11. Then, in the second grinding step S3, it is detected that the region just ground and the region currently ground have the same thickness, and then the grinding is stopped.

In addition, the structure, method, etc. of this embodiment can be appropriately modified and implemented as long as it does not deviate from the scope of the purpose of the present invention.

(Implementation Method 2) In Implementation Method 1, the grinding device 2 is used to grind a circular workpiece 11. However, the workpiece grinding method of the present invention can also be applied to workpieces of other shapes. In this implementation method, the grinding device 2 is used to grind a non-circular workpiece.

Specifically, the non-circular workpiece is ground and thinned by sequentially performing the holding step S1', the first grinding step S2', and the second grinding step S3' on the non-circular workpiece. The holding step S1', the first grinding step S2', and the second grinding step S3' are respectively equivalent to the modified examples of the holding step S1, the first grinding step S2, and the second grinding step S3 in the first embodiment (refer to FIG. 3). In addition, except for the matters described below, the contents and processes of the holding step S1', the first grinding step S2', and the second grinding step S3' are respectively the same as the holding step S1, the first grinding step S2, and the second grinding step S3.

FIG. 10 is a perspective view of the grinding device 2 in the holding step S1'. In the holding step S1', the workpiece 21 is held by the holding surface 6a of the chuck table 6. The workpiece 21 is a non-circular member whose distance from the center to the outer periphery is not fixed. The grinding of a rectangular workpiece 21 is described below as an example. FIG. 10 illustrates a workpiece 21 having a square first surface (front surface) 21a and a second surface (back surface) 21b.

For example, the workpiece 21 is a package substrate such as a CSP (Chip Size Package) substrate or a QFN (Quad Flat Non-leaded package) substrate. The package substrate is formed by covering and sealing a plurality of component chips mounted on a predetermined substrate with a resin layer (sealing resin). For example, the package substrate is formed into a rectangular shape with a length of one side being greater than 50 mm and less than 550 mm. By dividing the package substrate into pieces, a package component having a plurality of packaged component chips is manufactured. Furthermore, by grinding and thinning the resin layer in advance with a grinding device 2 before dividing the package substrate, a thin package component can be manufactured.

However, as long as the shape of the workpiece 21 is non-circular, there is no limitation on the material, structure, size, etc. of the workpiece 21. For example, the workpiece 21 may be a polygonal component having three or more corners and sides, or an elliptical or oval component.

While the non-circular workpiece 21 is held by the chuck table 6, the workpiece 21 is supported by the support member 27. For example, the support member 27 is a high-rigidity substrate formed in a disc shape. The specific example of the material of the support member 27 is the same as that of the workpiece 11 (see FIG. 4 ). In addition, the diameter of the support member 27 is set to be greater than the diameter of the suction surface 10a of the chuck table 6.

The support member 27 is fixed to the workpiece 21 by an adhesive or the like so as to cover the surface of the workpiece 21 opposite to the ground surface. For example, when the second surface 21b of the workpiece 21 is the ground surface, the support member 27 is fixed to the first surface 21a of the workpiece 21.

However, as long as the support member 27 can support the workpiece 21, the material, structure, size, etc. of the support member 27 are not limited. For example, a circular support sheet can be used as the support member 27. The support sheet can be a film including a film-like substrate and an adhesive layer (paste) provided on the substrate, or a heat-pressed sheet that does not contain an adhesive layer and can be heat-pressed to the workpiece 21.

The workpiece 21 supported by the supporting member 27 is arranged on the chuck table 6 in such a manner that the first surface 21a side (supporting member 27 side) faces the holding surface 6a and the second surface 21b side (grinding surface side) is exposed upward. At this time, the workpiece 21 is positioned in such a manner that the rotation axis 12 of the chuck table 6 passes through the center of the workpiece 21. In addition, the supporting member 27 is arranged to cover the entire suction surface 10a. In this state, if the suction force (negative pressure) of the suction source acts on the suction surface 10a, the first surface 21a side of the workpiece 21 is sucked and held by the holding surface 6a through the supporting member 27.

In addition, as mentioned above, the holding surface 6a of the chuck table 6 is strictly formed into a cone shape (refer to FIG. 2). Then, if the support member 27 is attracted by the suction surface 10a, the workpiece 21 and the support member 27 are held in a state of being slightly bent and deformed along the holding surface 6a. As a result, the held area 6b (refer to FIG. 2) or the area held in the vicinity of the workpiece 21 is arranged to be substantially parallel to the horizontal plane (XY plane).

As described above, by placing the workpiece 21 on the chuck table 6 through the support member 27, when the suction surface 10a is formed into a circular shape in anticipation of sucking a circular workpiece, a non-circular workpiece 21 can be held by the chuck table 6. However, the shape of the suction surface 10a can be appropriately changed in accordance with the shape of the workpiece 21. For example, the suction surface 10a can be formed into a rectangular shape in accordance with a rectangular workpiece 21. In this case, the support member 27 can be omitted and the workpiece 21 can be directly sucked by the suction surface 10a.

Next, by grinding a portion of the second surface 21b side of the workpiece 21, the first area of the workpiece 21 is thinned while the unground second area remains on the workpiece 21 (first grinding step S2'). FIG. 11(A) is a perspective view of the grinding device 2 in the first grinding step S2', and FIG. 11(B) is a top view of the workpiece 21 and the grinding wheel 54 in the first grinding step S2'.

In the first grinding step S2', first, the positional relationship between the chuck table 6 and the grinding wheel 54 is adjusted. Specifically, the chuck table 6 and the grinding wheel 54 are arranged in such a manner that the grinding stone 58 is separated from the side surface of the workpiece 21 and the lower surface of the grinding stone 58 is positioned lower than the upper surface of the workpiece 21.

In more detail, the chuck table 6 rotates to adjust the orientation (angle) of the workpiece 21 so that one side of the workpiece 21 is along the Y-axis direction. In addition, the position of the chuck table 6 in the X-axis direction is adjusted by the moving mechanism 20 (see FIG. 1 ) so that the workpiece 21 does not overlap with the grinding wheel 54 but is arranged in front of the grinding wheel 54 (lower left side in FIG. 11 (A) and left side in FIG. 11 (B)). At this time, one side of the workpiece 21 and the grinding stone 58 are separated from each other in the X-axis direction.

Furthermore, the position of the grinding unit 44 in the Z-axis direction is adjusted by the moving mechanism 32 (see FIG. 1 ) so that the lower surface of the grinding stone 58 is positioned below the upper surface (second surface 21 b, grinding surface) of the workpiece 21. The height position difference between the upper surface of the workpiece 21 and the lower surface of the grinding stone 58 at this time corresponds to the target value of the grinding amount of the workpiece 21 in the first grinding step S2 '.

Next, the chuck table 6 is brought close to the grinding wheel 54, and the grinding stone 58 is brought into contact with the side surface of the workpiece 21. Specifically, while the grinding wheel 54 is rotated about the rotation axis 60 by the motor 64, the chuck table 6 is moved along the X-axis direction by the moving mechanism 20 (see FIG. 1 ) to approach the grinding wheel 54. As a result, the grinding stone 58 is brought into contact with the side surface of the workpiece 21 (see FIG. 11 (A) and FIG. 11 (B)).

Then, the grinding device 2 detects that the grinding stone 58 contacts the side surface of the workpiece 21. For example, the motor 64 and the load measuring devices 66 and 68 provided in the grinding device 2 function as a detector that detects that the grinding stone 58 contacts the side surface of the workpiece 21.

Specifically, if the grinding stone 58 contacts the side surface of the workpiece 21, a load is applied to the grinding stone 58. As a result, the torque of the spindle 50 required to maintain the rotation of the grinding wheel 54 increases, and the current value of the motor 64 also increases. Therefore, the controller 62 (see FIG. 1 ) can detect that the grinding stone 58 contacts the side surface of the workpiece 21 by comparing the current value of the motor 64 with a preset reference value (threshold value).

Furthermore, if the grinding stone 58 contacts the side surface of the workpiece 21, a load is applied to the chuck table 6 and the spindle 50, and the load measured by the load measuring device 66, 68 increases. Therefore, the controller 62 (see FIG. 1) compares the load value measured by the load measuring device 66 or the load measuring device 68 with a preset reference value (threshold value), thereby detecting that the grinding stone 58 contacts the side surface of the workpiece 21.

However, there is no limitation on the method for detecting the contact between the workpiece 21 and the grinding stone 58. For example, a photo sensor or the like may be used to detect that the grinding stone 58 contacts the side surface of the workpiece 21. In addition, the operator may directly visually check the workpiece 21 and the grinding wheel 54 to check whether the grinding stone 58 contacts the workpiece 21.

If it is detected that the grinding stone 58 contacts the workpiece 21, the movement of the chuck table 6 stops. Thereby, the positional relationship between the chuck table 6 and the grinding wheel 54 is set so that the grinding stone 58 contacts the side surface of the workpiece 21.

Next, the chuck table 6 is rotated while the grinding wheel 54 is kept rotating, so that the grinding stone 58 grinds a part of the workpiece 21. Specifically, when the chuck table 6 is rotated, the grinding stone 58 contacts the first area (peripheral area) 23 corresponding to the area near the four corners of the workpiece 21. Thereby, the second surface 21b side of the first area 23 of the workpiece 21 is ground, and the first area 23 is thinned. On the other hand, the grinding stone 58 does not contact the circular second area (central area) 25 including the center of the workpiece 21. Therefore, the second area 25 is not ground and thinned, and the original thickness is maintained as a circular unground area. As a result, a step portion 21c corresponding to the side surface of the second area 25 is formed at the boundary between the first area 23 and the second area 25.

For example, the number of rotations of the chuck table 6 is set to be greater than 10 rpm and less than 300 rpm, and the number of rotations of the grinding wheel 54 is set to be greater than 1000 rpm and less than 7000 rpm. In addition, the number of rotations _n1 of the chuck table 6 in the first grinding step S2' is preferably smaller than the number of rotations _n2 of the chuck table 6 in the second grinding step S3' described later. For example, the number of rotations _n1 is set to be less than 90% of the number of rotations _n2 , preferably less than 80%, and more preferably less than 70%. Thereby, the first area 23 of the workpiece 21 becomes easy to be ground uniformly by the grinding stone 58, and it is difficult to produce thickness deviation of the workpiece 21 in the first area 23.

Next, the second area 25 of the workpiece 21 is ground, and after it is detected that the first area 23 and the second area 25 have the same thickness, the grinding of the workpiece 21 is stopped (second grinding step S3'). FIG. 12 (A) is a perspective view of the grinding device 2 in the second grinding step S3', and FIG. 12 (B) is a top view of the workpiece 21 and the grinding wheel 54 in the second grinding step S3'.

In the second grinding step S3', first, the positional relationship between the chuck table 6 and the grinding wheel 54 is adjusted. Specifically, in a state where the grinding unit 44 is arranged above the chuck table 6, the chuck table 6 is moved along the X-axis direction by the moving mechanism 20 (refer to FIG. 1), and the chuck table 6 is positioned in such a manner that the rotation trajectory of the grinding stone 58 overlaps with the center of the workpiece 21 in the Z-axis direction. Thereby, the grinding stone 58 is arranged to overlap with the second area 25 (unground area) of the workpiece 21. In addition, the diameter of the rotation trajectory of the grinding stone 58 is at least larger than the radius of the second area 25. Therefore, the grinding stone 58 is arranged to overlap with the arc-shaped area from the center of the second area 25 to the step portion 21c.

Next, the chuck table 6 is rotated around the rotation axis 12, and the grinding wheel 54 is rotated around the rotation axis 60. For example, the rotation speed of the chuck table 6 is set to 100 rpm or more and 900 rpm or less, and the rotation speed of the grinding wheel 54 (the rotation speed of the spindle 50) is set to 1000 rpm or more and 7000 rpm or less.

Then, the grinding unit 44 is lowered in the Z-axis direction by the moving mechanism 32 (see FIG. 1 ). As a result, the chuck table 6 and the grinding wheel 54 move relative to each other in the direction parallel to the rotation axis 60 (Z-axis direction), and the grinding stone 58 approaches and contacts the workpiece 21 while rotating. In addition, the processing feed speed is set to, for example, 1 μm/s or more and 6 μm/s or less.

The grinding stone 58 is in contact with the second surface 21b of the second region 25 of the workpiece 21 while rotating through the rotation shaft 12. Thus, the second region 25 of the workpiece 21 is ground and thinned. Then, when the second region 25 is ground until the thickness is the same as that of the first region 23, the step portion 21c disappears and the overall thickness of the workpiece 21 is uniform.

As described above, in the second grinding step S3', the disk-shaped unground area remaining in the second area 25 of the workpiece 21 is ground by performing the first grinding step S2'. Thus, the second area 25 of the workpiece 21 can be ground and thinned in the same manner as the disk-shaped workpiece.

Here, if the first grinding step S2' is not performed and the entire rectangular workpiece 21 is ground at once, the workpiece 21 is prone to thickness deviation. Specifically, in the area (diagonal area) overlapping the diagonal of the second surface 21b in the workpiece 21, the distance from the center to the outer periphery of the workpiece 21 is longer than that of other areas of the workpiece 21. Then, when grinding the diagonal area of the workpiece 21, the contact area between the workpiece 21 and the grinding stone 58 becomes wider than that of grinding other areas of the workpiece 21. As a result, the load applied to the grinding stone 58 increases, and the area closer to the diagonal area of the workpiece 21 becomes more difficult to grind. As a result, the grinding amount of the workpiece 21 varies, and the workpiece 21 after grinding tends to have a shape in which the second surface 21b is laterally bent.

On the other hand, in the present embodiment, after the first area 23 of the workpiece 21 is ground in the first grinding step S2', the disc-shaped unground area remaining in the second area 25 of the workpiece 21 is ground in the second grinding step S3'. In the first grinding step S2', since only the first area 23 of the workpiece 21 is ground, the grinding area is small, and it is difficult for the thickness deviation to occur in the first area 23. In addition, in the second grinding step S3', since the second area 25 having a fixed length from the center to the outer periphery is ground, it is also difficult for the thickness deviation to occur in the second area 25. As a result, the entire workpiece 21 is ground roughly uniformly.

In the second grinding step S3', similarly to the second grinding step S3 of the first embodiment (see Fig. 7 (A) and Fig. 7 (B)), after detecting that the first region 23 and the second region 25 have the same thickness, the grinding of the workpiece 21 is stopped. For example, as described above, based on the load corresponding value (the current value of the motor 64, the load measured by the load measuring devices 66 and 68) or the value measured by the thickness measuring device 76 (see Fig. 9), it is detected that the first region 23 and the second region 25 have the same thickness.

After detecting that the first area 23 and the second area 25 have the same thickness, a control signal is output from the controller 62 (see FIG. 1 ) to the moving mechanism 32 (see FIG. 1 ), and the grinding unit 44 rises. As a result, the grinding stone 58 is separated from the workpiece 21 , and the grinding of the workpiece 21 by the grinding stone 58 is stopped.

In addition, similar to the second grinding step S3 of the first embodiment, even in the second grinding step S3', after the first region 23 and the second region 25 are detected to have the same thickness, the grinding of the workpiece 21 may be stopped after the entire workpiece 21 (the first region 23 and the second region 25) is ground by a predetermined amount. For example, the grinding amount of the entire workpiece 21 after the first region 23 and the second region 25 are detected to have the same thickness is set to 10 μm or less, preferably 5 μm or less.

Furthermore, in the present embodiment, the first grinding step S2' (see Fig. 11 (A) and Fig. 11 (B)) is described in which the chuck table 6 is rotated in a state where the grinding stone 58 of the grinding wheel 54 is in contact with the side surface of the workpiece 21 to grind the first area 23 of the workpiece 21. However, the grinding method of the first area 23 of the workpiece 21 is not limited. For example, in the first grinding step S2', similarly to the second grinding step S3' (see Fig. 12 (A) and Fig. 12 (B)), the grinding wheel 54 positioned above the workpiece 21 may be lowered to bring the grinding stone 58 into contact with the second surface 21b side of the workpiece 21, thereby grinding the first area 23.

In addition, the structure and method of this embodiment can be appropriately modified and implemented as long as they do not deviate from the purpose of the present invention. In addition, the grinding method of the workpiece of the first embodiment and the grinding method of the workpiece of the second embodiment can be appropriately combined.

11: Workpiece 11a: First surface (front) 11b: Second surface (back) 11c: Step-down section 13: First area (peripheral area) 15: Second area (central area) 21: Workpiece 21a: First surface (front) 21b: Second surface (back) 21c: Step-down section 23: First area (peripheral area) 25: Second area (central area) 27: Support member 2: Grinding device 4: Base 4a: Opening 6: Chuck table (holding table) 6a: Holding surface 6b: Holding area 8: Frame (main body) 8a: Upper surface 8b: Recess 8c: Flow path 10: Holding member 10a: Suction surface 12: Rotating axis 14: Tilt adjustment mechanism 16: Workbench base 18A: Fixed support member 18B: Movable support member 20: Moving mechanism (moving unit) 22: Ball screw 24: Pulse motor 26: Support platform 28: Nut part 30: Support structure (column) 32: Moving mechanism (moving unit) 34: Guide rail 36: Retaining member 38: Nut part 40: Ball screw 42: Pulse motor 44: Grinding unit 46: Housing 48: Buffer member 50: Spindle 52: Wheel seat 54: Grinding wheel 56: Wheel base 58: Grinding stone 60: Rotating shaft 62: Controller (control unit, control part, control device) 64: Motor 66,68: Load measuring device 70: Measuring unit 72: Rotating support part 74: Support arm 76: Thickness measuring device S1,S1´: Holding step S2,S2´: First grinding step S3,S3´: Second grinding step

FIG. 1 is a partial cross-sectional side view of the grinding device. FIG. 2 is a cross-sectional view of the chuck table. FIG. 3 is a flow chart of the grinding method of the workpiece. FIG. 4 is a perspective view of the grinding device in the holding step. FIG. 5 (A) is a perspective view of the grinding device in the first grinding step, and FIG. 5 (B) is a cross-sectional view of the grinding device in the first grinding step. FIG. 6 is a perspective view of the grinding device in the second grinding step. FIG. 7 (A) is a cross-sectional view of the grinding device in the initial stage of the second grinding step, and FIG. 7 (B) is a cross-sectional view of the grinding device in the final stage of the second grinding step. FIG8 is a graph showing the relationship between the grinding time and the load corresponding value in the second grinding step. FIG9 is a cross-sectional view showing a grinding device for measuring the thickness of a workpiece. FIG10 is a perspective view showing the grinding device in the holding step of the modified example. FIG11 (A) is a perspective view showing the grinding device in the first grinding step of the modified example, and FIG11 (B) is a top view showing the workpiece and the grinding wheel in the first grinding step of the modified example. FIG12 (A) is a perspective view showing the grinding device in the second grinding step of the modified example, and FIG12 (B) is a top view showing the workpiece and the grinding wheel in the second grinding step of the modified example.

S1: Keep step

S2: First grinding step

S3: Second grinding step

Claims (4)

A method for grinding a workpiece, wherein the workpiece includes a first surface and a second surface, and is characterized in that the method comprises: a holding step, wherein the first surface side of the workpiece is held by a holding surface of a chuck table; a first grinding step, wherein after the holding step, a portion of the second surface side of the workpiece is ground to thin the first area of the workpiece while leaving an unground second area on the workpiece; and a second grinding step, wherein after the first grinding step, the second area of the workpiece is ground, and the grinding of the workpiece is stopped after it is detected that the first area and the second area have the same thickness. A method for grinding a workpiece as claimed in claim 1, wherein, in the second grinding step, the workpiece is ground while measuring a value corresponding to a grinding load applied when grinding the workpiece, and based on a change in the value corresponding to the grinding load, it is detected that the first region and the second region have the same thickness. A method for grinding a workpiece as claimed in claim 1, wherein, in the second grinding step, the workpiece is ground while the thickness of the workpiece in the first area and the second area is measured by a thickness gauge, and based on the value measured by the thickness gauge, it is detected that the first area and the second area have the same thickness. A method for grinding a workpiece as claimed in any one of claims 1 to 3, wherein in the second grinding step, after detecting that the first area and the second area have become the same thickness and then grinding the first area and the second area by a predetermined amount, the grinding of the workpiece is stopped.