JP2024013315A - grinding equipment - Google Patents

Abstract

An object of the present invention is to extend a measurement range in which measurement accuracy is guaranteed.
[Solution] A holding table, a grinding unit, a first contact height gauge and a second contact height gauge each capable of acquiring displacement information in the thickness direction of a workpiece, and a workpiece that uses the displacement information to a calculation unit that calculates a change in thickness of the workpiece, the calculation unit calculating a change in thickness of the workpiece from an initial thickness before grinding based on displacement information obtained using the first contact height gauge. A change in the thickness of the workpiece is calculated in the first range up to the first thickness, and includes a second thickness thinner than the first thickness based on displacement information obtained using the second contact height gauge. In the second range, the change in the thickness of the workpiece is calculated, the first range is the range where measurement accuracy is guaranteed in the first contact height gauge, and the second range is the range measured in the second contact height gauge. To provide a grinding device whose accuracy is within a guaranteed range.
[Selection diagram] Figure 2

Description

The present invention relates to a grinding device having two contact height gauges.

When grinding a workpiece such as a semiconductor wafer using a grinding device, for example, the workpiece is suction-held on the holding surface of the holding table, and the holding table is rotated around a predetermined rotation axis, and the spindle By lowering the grinding wheel that rotates with the rotation axis, the grinding wheel of the grinding wheel grinds and thins the workpiece.

In such a grinding device, the workpiece is ground while measuring the thickness of the workpiece with a pair of height gauges in a region different from the grinding region where the grinding wheel and the workpiece contact (for example, (See Patent Document 1).

Specifically, during grinding, the height position of the holding surface is measured with a first height gauge, and the height position of the upper surface (i.e., the surface to be ground) of the workpiece that is suction-held by the holding surface is measured with a first height gauge. Measure using height gauge 2. Then, the thickness of the workpiece is calculated from the difference between the height position of the upper surface of the workpiece and the height position of the holding surface.

Incidentally, each height gauge has a predetermined measurement range in which measurement accuracy (also referred to as linearity accuracy) is guaranteed. For example, the measurement range where measurement accuracy is guaranteed is 0 μm or more and 1800 μm or less. Therefore, even if the measurement is performed in a range exceeding the guaranteed measurement range, the thickness of the workpiece cannot be accurately measured.

For example, when thinning a workpiece whose thickness is 3000 μm before grinding to 1000 μm, if the height position of the holding surface is set to 0 μm, the thickness will progress from 3000 μm at the start of grinding to 1800 μm as the thickness progresses. The thickness of the workpiece cannot be accurately measured until the thickness of the workpiece becomes 1800 μm or less.

Japanese Patent Application Publication No. 2014-37045

The present invention has been made in view of the above-mentioned problems, and aims to improve measurement accuracy in order to accurately measure the initial thickness of a relatively thick workpiece and also accurately measure the thickness of the workpiece after thinning. The purpose is to extend the guaranteed measurement range.

According to one aspect of the present invention, a holding table has a holding surface that holds a workpiece by suction, and a spindle, and the workpiece held on the holding surface is moved by a grinding wheel attached to the spindle. a grinding unit that thins the workpiece by grinding; a first contact height gauge capable of acquiring displacement information corresponding to displacement in the thickness direction of the workpiece held by suction on the holding surface; A second contact height gauge capable of acquiring displacement information; and a calculation unit that includes a processor and a memory and calculates a change in the thickness of the workpiece using the displacement information, the calculation unit , based on the displacement information obtained using the first contact height gauge, from the initial thickness of the workpiece before grinding to a predetermined thickness of the workpiece that is thinner than the initial thickness. The change in thickness of the workpiece is calculated in the first range up to a first thickness corresponding to , and the change in thickness of the workpiece is calculated from the first thickness based on the displacement information obtained using the second contact height gauge. A change in the thickness of the workpiece is calculated in a second range including a second thickness of the workpiece, which is thinner, and the first range has a guaranteed measurement accuracy in the first contact height gauge. A grinding device is provided in which the second range is a range in which measurement accuracy is guaranteed in the second contact type height gauge.

Preferably, the lower limit of the first range is greater than or equal to the upper limit of the second range.

Preferably, the first contact portion of the first contact height gauge and the second contact portion of the second contact height gauge are formed on a porous plate of the holding table so as to be able to contact the workpiece. placed above.

In the grinding apparatus according to one aspect of the present invention, the initial thickness of the workpiece before grinding is determined based on the displacement information obtained using the first contact height gauge. A change in the thickness of the workpiece is calculated in a first range of up to a first thickness corresponding to a predetermined thickness of . This first range is a range in which measurement accuracy is guaranteed in the first contact type height gauge.

Further, based on the displacement information obtained using the second contact height gauge, a change in the thickness of the workpiece is calculated in a second range including a second thickness of the workpiece that is thinner than the first thickness. do. This second range is a range in which measurement accuracy is guaranteed in the second contact type height gauge.

In this way, instead of measuring the thickness of the workpiece based on the difference in the height positions measured by two contact height gauges, each contact height gauge measures different ranges of the thickness of the workpiece. By performing measurements using a single contact height gauge, it is possible to grind a workpiece while measuring a wide range of thicknesses that exceeds the range for which the measurement accuracy of a single contact type height gauge is guaranteed.

It is a perspective view of a grinding device. FIG. 2 is a perspective view of the grinding device with the chuck table placed in the grinding position. FIG. 3(A) is a top view showing the arrangement of two height gauges, and FIG. 3(B) is a graph showing a range in which measurement accuracy is guaranteed. FIG. 7 is a diagram showing how the reference height position of the second height gauge is set. FIG. 6 is a diagram showing how the reference height position of the first height gauge is set. FIG. 3 is a diagram showing how a workpiece is ground. FIG. 3 is a diagram showing how a workpiece is ground.

Embodiments according to one aspect of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a perspective view of the grinding device 2. FIG. The X-axis direction, Y-axis direction, and Z-axis direction shown in FIG. 1 are directions orthogonal to each other.

The grinding device 2 has a base 4 that supports a plurality of components. The base 4 has a rectangular parallelepiped shape including a longitudinal portion along the X-axis direction. A rectangular opening 4a whose longitudinal portion is arranged along the X-axis direction is formed on the upper surface of the base 4.

A rectangular table cover 6 is provided in the opening 4a. Bellows-shaped cover members 8 that are expandable and retractable along the X-axis direction are provided on both sides of the table cover 6 in the X-axis direction. An X-axis direction movement mechanism 10 is provided below the table cover 6 and the pair of cover members 8.

In addition, in FIG. 1, the approximate position of the X-axis direction moving mechanism 10 is indicated by an arrow, and the specific structure is omitted. The X-axis direction movement mechanism 10 has a pair of guide rails (not shown) each arranged along the X-axis direction.

A rectangular plate-shaped moving table (not shown) is attached to the pair of guide rails so as to be slidable along the X-axis direction. A nut portion (not shown) is provided on the lower surface side of the movable table.

A screw shaft (not shown) arranged along the X-axis direction is rotatably connected to the nut portion via a plurality of balls (not shown). A driving source (not shown) such as a stepping motor is connected to one end of the screw shaft.

When the drive source is operated, the moving table moves along the X-axis direction. A disk-shaped chuck table (holding table) 12 is provided on the table cover 6. As shown in FIG. 4, the chuck table 12 has a disc-shaped frame 14 made of non-porous ceramics.

A disc-shaped porous plate 16 made of porous ceramics is fixed to the upper surface side of the frame 14. A plurality of first channels are formed radially in the recessed portion of the frame 14. Further, a second flow path is formed at the radial center of the recessed portion, passing through the frame 14 in the thickness direction of the frame 14.

A suction source 18 such as a vacuum pump is connected to the second flow path via a solenoid valve 18a. When the electromagnetic valve 18a is opened while the suction source 18 is operated, negative pressure is transmitted to the upper surface of the porous plate 16 via the first flow path, the second flow path, and the like.

The upper surfaces of the frame body 14 and the porous plate 16 are substantially flush with each other, and function as a holding surface 12a that sucks and holds the workpiece 11 (see FIG. 1). As shown in FIG. 4, the holding surface 12a has a conical shape in which the center part protrudes more than the outer peripheral part. The amount of protrusion is, for example, about 10 μm to 20 μm, but in FIG. 4, the amount of protrusion is exaggerated for convenience of explanation.

An annular table base 20 is fixed to the lower surface of the chuck table 12 with a fixing member (not shown) such as a bolt. Further, an annular support base (not shown) having approximately the same diameter as the table base 20 is provided on the lower surface side of the table base 20 .

An annular bearing (not shown) is provided inside the through hole located in the radial center of the support base, and a cylindrical rotating shaft 22 is fixed inside the bearing. That is, the chuck table 12 is supported by the support base via bearings.

The support base is supported by a tilt adjustment mechanism (not shown). The inclination adjustment mechanism adjusts the inclination of the chuck table 12 by adjusting the spatial inclination of the support base, and makes a part of the holding surface 12a substantially parallel to a grinding surface 50d (see FIG. 6), which will be described later.

The tilt adjustment mechanism includes one fixed shaft (not shown) whose length in the Z-axis direction is constant, and two movable shafts (not shown) whose length in the Z-axis direction is variable. The one fixed shaft and the two movable shafts are arranged at approximately equal intervals along the circumferential direction of the chuck table 12. Further, the tilt adjustment mechanism is supported by a moving plate of the X-axis direction moving mechanism 10.

The upper end portion of the above-mentioned rotating shaft 22 is connected to the lower surface side of the chuck table 12. A third flow path for transmitting negative pressure to the chuck table 12 is formed in the rotating shaft 22 . Note that in FIG. 4, the third flow path of the rotating shaft 22 is briefly shown for convenience of explanation, but the third flow path can achieve both high-speed rotation of about 100 rpm to 300 rpm and prevention of vacuum leaks. Similarly, it is connected to a suction source 18 via a rotary joint.

A driven pulley (not shown) is fixed to the outer circumference of the rotating shaft 22. A rotary drive source (not shown) such as a servo motor is arranged on the moving plate of the X-axis direction moving mechanism 10, and a drive pulley (not shown) is fixed to the output shaft of the rotary drive source. .

An endless belt (not shown) is wrapped around the driven pulley and the drive pulley. When the rotational drive source is operated, the power of the rotational drive source is transmitted, and the chuck table 12 rotates around the rotation axis 22. In FIG. 4, the rotation center 12b of the chuck table 12 is indicated by a chain line. The rotation center 12b passes through the center of the holding surface 12a.

Returning to FIG. 1, on the back side (one side in the X-axis direction) of the base 4, a support column 24 whose longitudinal portion is arranged along the Z-axis direction is provided. A Z-axis direction movement mechanism 26 is provided on one side of the support column 24. The Z-axis direction movement mechanism 26 has a pair of guide rails 28 each arranged substantially parallel to the Z-axis direction.

A movable plate 30 is slidably fixed to the pair of guide rails 28. A nut portion (not shown) is provided on the back side of the movable plate 30, and a screw shaft 32 arranged along the Z-axis direction is inserted into the nut portion through a plurality of balls (not shown). are rotatably connected.

A driving source 34 such as a stepping motor is connected to the upper end of the screw shaft 32 . By rotating the screw shaft 32 with the drive source 34, the movable plate 30 moves along the Z-axis direction.

A grinding unit 40 is provided on the front side of the movable plate 30. The grinding unit 40 has a cylindrical support 42 fixed to the surface side of the movable plate 30. A cylindrical spindle housing 44 whose longitudinal portion is arranged along the Z-axis direction is provided inside the support 42 .

A part of a cylindrical spindle 46 whose longitudinal portion is arranged along the Z-axis direction is rotatably accommodated in the spindle housing 44 . A rotational drive source (not shown) such as a servo motor is provided near the upper end of the spindle 46 .

The lower end of the spindle 46 protrudes below the lower ends of the support 42 and the spindle housing 44 . An upper surface side of a disk-shaped mount 48 made of metal is fixed to the lower end of the spindle 46.

An annular grinding wheel 50 is fixed to the lower surface of the mount 48 using a fixing member (not shown) such as a bolt. In this manner, grinding wheel 50 is mounted to spindle 46 via mount 48.

The grinding wheel 50 has an annular wheel base 50a made of metal such as an aluminum alloy (see FIG. 4). On the lower surface side of the wheel base 50a, a plurality of segment-shaped grinding wheels 50b are arranged at approximately equal intervals along the circumferential direction of the wheel base 50a.

When the spindle 46 is rotated, the grinding wheel 50 rotates with the spindle 46 as the rotation axis. At this time, as shown in FIG. 6, a grinding surface 50d is formed by the trajectory of the lower surface 50c of the plurality of grinding wheels 50b.

Returning to FIG. 1 again, the chuck table 12 is moved between a loading/unloading position A1 located on the front side (the other side in the X-axis direction) of the base 4 and a grinding position A2 by the X-axis direction movement mechanism 10. move between

When the chuck table 12 is placed at the carry-in/out position A1, an unground workpiece 11 is carried into the chuck table 12, or a ground workpiece 11 is carried out from the chuck table 12.

The workpiece 11 to be subjected to the grinding process in this embodiment has a thickness larger than the thickness corresponding to a predetermined diameter of a silicon wafer defined by the SEMI (Semiconductor Equipment and Materials International) standard.

The workpiece 11 of this embodiment has a diameter of 8 inches (200 mm ± 0.2 mm), which is sufficiently thicker than the thickness of an 8 inch silicon wafer (i.e., 725 ± 20 μm) specified by the SEMI standard. It has a thickness of 3600 μm.

However, the thickness of the workpiece 11 may be a predetermined value of 2.0 mm or more and 20.0 mm or less. The workpiece 11 of this embodiment is a disk-shaped substrate made of glass. However, the workpiece 11 may be a so-called stacked wafer in which a plurality of silicon wafers are stacked.

The workpiece 11 has one surface 11a that is attracted by the holding surface 12a, and the other surface 11b that becomes the surface to be ground. The distance between the one surface 11a and the other surface 11b corresponds to the thickness of the workpiece 11. In this embodiment, the direction from one surface 11a to the other surface 11b is conveniently referred to as the thickness direction 11c of the workpiece 11.

When grinding the workpiece 11, first, the chuck table 12, which holds the workpiece 11 under suction with the holding surface 12a, is placed at the grinding position A2 as shown in FIG. FIG. 2 is a perspective view of the grinding device 2 in which the chuck table 12 is placed at the grinding position A2.

Two contact type height gauges are provided near the chuck table 12 located at the grinding position A2. The first height gauge (first contact type height gauge) 52 is arranged closer to the support column 24 than the second height gauge (second contact type height gauge) 54 in the X-axis direction.

However, the positions of the first height gauge 52 and the second height gauge 54 may be exchanged. That is, the second height gauge 54 may be placed closer to the support column 24 than the first height gauge 52.

As shown in FIG. 3(A), the first height gauge 52 has a main body portion 52a fixed to the base 4. As shown in FIG. A base end portion of a cantilever-shaped arm 52b is connected to the main body portion 52a. A cylindrical head portion 52c made of metal is provided at the tip of the arm 52b.

The head portion 52c and the arm 52b are attached to the main body portion 52a so as to fall downward under their own weight and assume a forward-leaning posture. Further, in order to raise and lower the head portion 52c relatively largely as needed, a lifting mechanism (not shown) including a motor (not shown) is provided at the base end of the arm 52b.

A hemispherical contact portion (first contact portion) 52d (see FIG. 4) made of diamond is provided at the lower end of the head portion 52c. When grinding the workpiece 11, the main body portion 52a is placed in the lowered position, and the contact portion 52d is brought into contact with the workpiece 11 that is suction-held by the holding surface 12a (see FIG. 6).

Thereby, the displacement of the height position of the other surface 11b of the workpiece 11 in the thickness direction 11c is obtained. During grinding, the contact portion 52d continuously contacts the other surface 11b, thereby acquiring displacement information of the other surface 11b in real time.

Also when setting the reference height position of the first height gauge 52, the main body portion 52a is placed in the lowered position (see FIG. 5). On the other hand, when the first height gauge 52 does not acquire displacement information of the other surface 11b, the main body portion 52a is placed in the raised position (see FIG. 4).

By the way, the head portion 52c is configured to be rotatable with respect to the arm 52b. The rotational axis of the head portion 52c is arranged along a direction substantially perpendicular to the paper surface of FIG. 3(A). If a portion of the contact portion 52d continues to be in contact with the workpiece 11, only this portion will wear out and the contact portion 52d will wear unevenly.

When the contact portion 52d is unevenly worn, the operator adjusts the rotation angle of the head portion 52c to bring the area that is not unevenly worn into contact with the workpiece 11. This can prevent the metal head portion 52c from coming into contact with the workpiece 11.

Similarly, the second height gauge 54 has a main body portion 54a, an arm 54b, and a head portion 54c. The head portion 54c and the arm 54b are also attached to the main body portion 54a so as to fall downward under their own weight and assume a forward leaning posture.

A hemispherical contact portion (second contact portion) 54d (see FIG. 4) made of diamond is also provided at the lower end of the head portion 54c. By the head portion 54c coming into contact with the other surface 11b, displacement information of the other surface 11b can be acquired in real time similarly to the head portion 52c.

Like the head portion 52c, the head portion 54c is also configured to be movable up and down by a lifting mechanism (not shown). When acquiring displacement information of the other surface 11b with the second height gauge 54, the main body portion 54a is placed in the lowered position, and the contact portion 54d is brought into contact with the workpiece 11 that is suction-held by the holding surface 12a due to its own weight ( (See Figure 7).

Also when setting the reference height position of the second height gauge 54, the main body portion 54a is placed in the lowered position (see FIG. 4). On the other hand, when the second height gauge 54 does not acquire displacement information, the main body part 54a is placed in the raised position so that the contact part 54d is sufficiently separated from the other surface 11b (see FIG. 5).

The head portion 54c is also configured to be rotatable relative to the arm 54b. Therefore, by adjusting the rotation angle of the head portion 54c, the operator can bring the area of the contact portion 54d that is not unevenly worn into contact with the workpiece 11.

FIG. 3(A) is a top view showing the arrangement of the first height gauge 52 and the second height gauge 54. The contact portion 52d and the contact portion 54d are arranged above the porous plate 16 of the chuck table 12 so as to be able to contact the workpiece 11, respectively.

In FIG. 3A, the contact portions 52d and 54d are arranged between the rotation center 12b of the chuck table 12 and the radius of the porous plate 16 (ie, the inner radius of the frame 14). However, the distances from the rotation center 12b to the contact portions 52d, 54d are different.

Specifically, the distance B1 from the contact portion 52d (see the position of the head portion 52c) to the rotation center 12b is smaller than the distance B2 from the contact portion 54d (see the position of the head portion 54c) to the rotation center 12b. (B1<B2). However, the distances from each contact portion 52d, 54d to the rotation center 12b may be the same (B1=B2).

If the distances from each contact portion 52d, 54d to the center of rotation 12b are the same, the influence of in-plane variations in the thickness of the workpiece 11 on displacement information will be greater than when distance B1 is smaller than distance B2. can be reduced.

As shown in FIG. 3(B), the first height gauge 52 has a guaranteed measurement accuracy so that changes in the thickness of the workpiece 11 can be accurately detected in a predetermined thickness range (first range 52e). The specified range is predetermined. The first range 52e of this embodiment is a range of 1800 μm or more and 3600 μm or less.

On the other hand, the second height gauge 54 has a high measurement accuracy so that changes in the thickness of the workpiece 11 can be accurately detected in a predetermined thickness range (second range 54e) different from the first range 52e. A guaranteed range is predetermined. The second range 54e of this embodiment is a range of 0 μm or more and 1800 μm or less.

FIG. 3(B) is a graph showing a range in which measurement accuracy is guaranteed in the first height gauge 52 and the second height gauge 54. Measurement accuracy is evaluated, for example, by linearity when a graph is created in which the horizontal axis is the displacement amount of the height gauge and the vertical axis is the voltage value output from the height gauge.

In this embodiment, the linearity of the first height gauge 52 and the second height gauge 54 is ±0.3%F. S. (Full Scale). That is, in each of the above-mentioned first range 52e and second range 54e, ±0.3%F. S. is guaranteed.

Note that each of the contact portions 52d and 54d is physically movable in a predetermined direction in a range from -1000 μm to +6000 μm with a predetermined height position as a reference (0 μm), but as described above, accurate measurement accuracy is required. The range in which this is guaranteed is limited as shown in the first range 52e and the second range 54e.

In this way, instead of measuring the thickness of the workpiece 11 by the difference in height positions measured by two height gauges, the thickness of the workpiece 11 is measured by each of the first height gauge 52 and the second height gauge 54. By dividing and measuring different thickness ranges, it is possible to grind the workpiece 11 while measuring a wide range of thicknesses that exceeds the range in which the measurement accuracy of one height gauge is guaranteed.

In this embodiment, the lower limit of the first range 52e is equal to the upper limit of the second range 54e. By setting the first range 52e and the second range 54e continuously in this way, a wider range can be continuously measured compared to the case where the first range 52e and the second range 54e overlap in a certain area. can.

Note that as long as the lower limit of the first range 52e is greater than or equal to the upper limit of the second range 54e, the first range 52e does not need to be continuous with the second range 54e. For example, the first range 52e and the second range 54e may be discontinuous. However, in this case, there is a measurement range in which measurement accuracy is not guaranteed between the first range 52e and the second range 54e.

Furthermore, the thickness of the workpiece 11 may be measured using three or more height gauges in each of three or more continuous or discontinuous measurement ranges with guaranteed measurement accuracy. Thereby, the measurement range in which measurement accuracy is guaranteed can be further expanded.

Other elements of the grinding device 2 will be explained with reference to FIGS. 1 and 2. The grinding device 2 includes an X-axis moving mechanism 10, a rotational drive source for the chuck table 12, a suction source 18, a solenoid valve 18a, a Z-axis moving mechanism 26, a grinding unit 40, a first height gauge 52, a second height gauge 54, etc. It has a control section 56 that controls the operation.

The control unit 56 is configured by a computer including, for example, a processor (processing device) 58 represented by a CPU (Central Processing Unit) and a memory (storage device) 60.

The memory 60 includes a main storage device such as DRAM (Dynamic Random Access Memory), SRAM (Static Random Access Memory), and ROM (Read Only Memory), and an auxiliary storage device such as flash memory, hard disk drive, solid state drive, etc. include.

The auxiliary storage device stores software including a predetermined program. The functions of the control unit 56 are realized by operating the processing device and the like according to this software.

By executing a predetermined program with the processor 58, the control unit 56 functions as a calculation unit 62 that calculates a change in the thickness of the workpiece 11 using displacement information from the first height gauge 52 and the second height gauge 54. Function.

Next, with reference to FIGS. 4 to 7, a method of grinding the workpiece 11 while calculating the thickness of the workpiece 11 using the calculation unit 62 will be described. First, as shown in FIG. 4, the reference height position of the second height gauge 54 is set. FIG. 4 is a diagram showing how the reference height position of the second height gauge 54 is set.

Specifically, the chuck table 12, in which the workpiece 11 is not suction-held on the holding surface 12a, is moved to the grinding position A2, and while the chuck table 12 is rotated around the rotation axis 22, the contact portion of the second height gauge 54 is moved. 54d is brought into contact with the holding surface 12a.

Thereby, the reference height position of the second height gauge 54 is set at the holding surface 12a. The second height gauge 54 of this embodiment guarantees measurement accuracy in the Z-axis direction in the range from the thickness of the workpiece 11 of 0 μm (that is, the height position corresponding to the holding surface 12a) to the thickness of 1800 μm. and is responsible for measuring this thickness range.

Next, the chuck table 12 is returned to the loading/unloading position A1, and one surface 64a of the disc-shaped jig plate 64 is suction-held by the holding surface 12a. The jig plate 64 is made of ceramic such as alumina and has a thickness of 1800 μm. After suction and holding, the chuck table 12 is moved to the grinding position A2.

Next, as shown in FIG. 5, the reference height position of the first height gauge 52 is set on the other surface (upper surface) 64b of the jig plate 64. FIG. 5 is a diagram showing how the reference height position of the first height gauge 52 is set.

Specifically, the chuck table 12 holding the jig plate 64 under suction is moved to the grinding position A2, and the contact portion 52d of the first height gauge 52 is moved to the jig plate 64 while rotating the chuck table 12 around the rotation axis 22. It is brought into contact with the other surface 64b. Thereby, the reference height position of the first height gauge 52 is set on the other surface 64b of the jig plate 64.

The first height gauge 52 of this embodiment has a thickness ranging from 1800 μm (i.e., the height position corresponding to the other surface 64b of the jig plate 64) of the workpiece 11 to 3600 μm (i.e., the height position corresponding to the other surface 64b of the jig plate 64) in the Z-axis direction. The measurement accuracy is guaranteed in the range up to the initial thickness of the previous workpiece 11), and is responsible for measuring this thickness range.

Next, the chuck table 12 is returned to the loading/unloading position A1, the jig plate 64 is replaced with the workpiece 11, and the workpiece 11 is suction-held by the holding surface 12a. Then, the chuck table 12 holding the workpiece 11 under suction is moved to the grinding position A2, and grinding is started.

FIG. 6 shows a graph from an initial thickness 11c ₀ (3600 μm in this embodiment) of the workpiece 11 before grinding to a first thickness 11c ₁ (in this embodiment), which is a predetermined thickness thinner than the initial thickness 11c ₀ (3600 μm in this embodiment). FIG. 4 is a diagram showing how the workpiece 11 is ground when the thickness of the workpiece 11 is within the first range 52e (up to 1800 μm in the embodiment).

During grinding, the chuck table 12 that holds the workpiece 11 under suction is rotated around the rotating shaft 22 at a predetermined speed, and the grinding wheel 50, which rotates with the spindle 46 as the rotating shaft, is rotated to perform a predetermined process along the Z-axis direction. Descend at feed speed (infeed grinding).

When the grinding surface 50d contacts the other surface 11b of the workpiece 11, the other surface 11b side is ground. During grinding, the area where the plurality of grinding wheels 50b and the other surface 11b come into contact becomes a predetermined arc-shaped area 50e (see FIG. 2). Grinding water such as pure water is supplied from a nozzle (not shown) at a predetermined flow rate to the vicinity of this arcuate region 50e.

During grinding, both the contact parts 52d and 54d are in contact with the other surface 11b, but only the first height gauge 52, whose measurement accuracy is guaranteed in the first range 52e described above, can accurately measure the thickness. It is.

Therefore, when the workpiece 11 is relatively thick, the calculation unit 62 calculates the change in the thickness of the workpiece 11 based on the displacement information obtained using the first height gauge 52. On the other hand, if the workpiece 11 gradually becomes thinner, the first height gauge 52 will no longer be able to accurately measure the thickness of the workpiece 11.

Therefore, as shown in FIG. 7, in the second range 54e that includes the second thickness _11c2 of the workpiece 11 that is thinner than the first thickness _11c1 (i.e., the target thickness achieved by grinding), the calculation unit 62 calculates a change in the thickness of the workpiece 11 based on displacement information obtained using the second height gauge 54 .

FIG. 7 is a diagram showing how the workpiece 11 is ground when the thickness of the workpiece 11 is within the second range 54e. At this time, both the contact portions 52d and 54d are in contact with the other surface 11b, but only the second height gauge 54, whose measurement accuracy is guaranteed in the second range 54e, can accurately measure the thickness. be.

After grinding the workpiece 11 in this manner and thinning the workpiece 11 to the second thickness _11c2 , the grinding is completed and the chuck table 12 is returned to the loading/unloading position A1.

In this embodiment, the thickness of the workpiece 11 is not measured by the difference between the height positions measured by two height gauges, but the thickness of the workpiece 11 is measured by the first height gauge 52 and the second height gauge 54. By dividing and measuring different ranges of the height gauge, the workpiece 11 can be ground while measuring a wide range of thickness that exceeds the range in which the measurement accuracy of one height gauge is guaranteed.

In addition, the structure, method, etc. according to the above-described embodiments can be modified and implemented as appropriate without departing from the scope of the objective of the present invention. For example, it is also possible to grind a plurality of workpieces 11 by sequentially introducing the workpieces 11 into the grinding device 2.

In this case, since the reference height position set on the second height gauge 54 (see FIG. 4) and the reference height position set on the first height gauge 52 (see FIG. 5) can be used, one There is no need to set the reference height position each time before grinding the workpiece 11.

2: Grinding device, 4: Base, 4a: Opening 6: Table cover, 8: Cover member, 10: X-axis direction movement mechanism 11: Workpiece, 11a: One side, 11b: Other side, 11c: Thickness direction 11c ₀ : Initial thickness, 11c ₁ : First thickness, 11c ₂ : Second thickness 12: Chuck table (holding table), 12a: Holding surface, 12b: Center of rotation 14: Frame, 16: Porous plate , 18: Suction source, 18a: Solenoid valve 20: Table base, 22: Rotating shaft 24: Support column, 26: Z-axis direction movement mechanism, 28: Guide rail, 30: Moving plate 32: Screw shaft, 34: Drive source 40: Grinding unit, 42: Support, 44: Spindle housing, 46: Spindle 48: Mount, 50: Grinding wheel, 50a: Wheel base, 50b: Grinding wheel 50c: Bottom surface, 50d: Grinding surface, 50e: Arc shape Region 52: first height gauge (first contact type height gauge), 52a: main body part, 52b: arm 52c: head part, 52d: contact part (first contact part), 52e: first range 54: second height gauge (second height gauge) 2-contact height gauge), 54a: main body, 54b: arm 54c: head, 54d: contact section (second contact section), 54e: second range 56: control section, 58: processor, 60: memory, 62: Calculation unit 64: jig plate, 64a: one side, 64b: other side A1: loading/unloading position, A2: grinding position B1, B2: distance

Claims (3)

a holding table having a holding surface that holds the workpiece by suction;
a grinding unit that has a spindle and thins the workpiece by grinding the workpiece held by the holding surface with a grinding wheel attached to the spindle;
a first contact height gauge capable of acquiring displacement information corresponding to displacement in the thickness direction of the workpiece held by suction on the holding surface;
a second contact height gauge capable of acquiring the displacement information;
a calculation unit having a processor and a memory and calculating a change in the thickness of the workpiece using the displacement information;
Equipped with
The calculation unit is
Based on the displacement information obtained using the first contact height gauge, the initial thickness of the workpiece before grinding is reduced to a predetermined thickness of the workpiece that is thinner than the initial thickness. calculating a change in thickness of the workpiece in a first range of up to a corresponding first thickness;
A change in the thickness of the workpiece in a second range including a second thickness of the workpiece that is thinner than the first thickness based on the displacement information obtained using the second contact height gauge. Calculate,
The first range is a range in which measurement accuracy is guaranteed in the first contact height gauge,
A grinding device characterized in that the second range is a range in which measurement accuracy is guaranteed in the second contact height gauge. The grinding device according to claim 1, wherein the lower limit of the first range is greater than or equal to the upper limit of the second range. The first contact portion of the first contact height gauge and the second contact portion of the second contact height gauge are arranged above the porous plate of the holding table so as to be able to contact the workpiece. The grinding device according to claim 1 or 2, characterized in that:

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