Grinding apparatus, grinding method for workpiece, and program

Abstract

To provide a grinding apparatus that grinds one surface side of a workpiece such that the deviation of the finished thickness of the workpiece from a predetermined thickness is reduced.SOLUTION: A grinding apparatus comprises: a chuck table; a spindle having a grinding wheel with a plurality of grinding stones at its tip; a thickness measuring device; and a controller. The controller includes a processor configured to control the chuck table, the spindle, and the thickness measuring device such that the one surface side of the workpiece is ground until the thickness of the workpiece measured by the thickness measuring device reaches a predetermined thickness by pressing the plurality of grinding stones against the one surface side of the workpiece while rotating both the chuck table holding the workpiece on the holding surface with the one surface side exposed and the spindle. The processor controls the thickness measuring device to perform thickness measurement of the workpiece after it is determined that the flatness on the one surface side of the workpiece has been improved on the basis of the comparison between an actual value of a physical quantity and a threshold.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a grinding device for grinding a workpiece, a method for grinding a workpiece to be ground in the grinding device, and a program for causing a computer included in the grinding device to execute the method for grinding the workpiece.

Background Art

[0002] Chips of semiconductor devices are manufactured using wafers made of single crystals such as silicon (Si), silicon carbide (SiC), gallium nitride (GaN), lithium tantalate (LiTaO3:LT), or lithium niobate (LiNbO3:LN). Generally, this wafer is obtained by separating a portion located on one side of the ingot from the ingot.

[0003] Separation of the wafer from the ingot is performed, for example, using a wire saw. Alternatively, this separation may be performed by forming a separation layer including a modified portion and a crack extending from the modified portion inside the ingot using a laser beam having a wavelength that penetrates the material of the ingot, and then splitting the ingot in this separation layer (see, for example, Patent Document 1).

[0004] However, one side of this wafer (specifically, the side newly exposed by separation from the ingot) becomes rough or has an uneven shape, and it is often difficult to use this wafer for chip manufacturing. Therefore, the wafer is often separated from the ingot so as to be thicker than a thickness suitable as the thickness of the wafer to be used for chip manufacturing, and then one side thereof is flattened and the thickness of the wafer is ground to the suitable thickness.

[0005] Similarly, one side of the ingot remaining after separating the wafer also becomes rough or has an uneven shape. Therefore, this ingot is often ground so as to flatten one side thereof prior to separating a new wafer from the ingot.

Prior Art Documents

Patent Document

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] Grinding of workpieces such as wafers or ingots is generally performed in a grinding apparatus including a chuck table for holding the workpiece on a holding surface, a spindle having a grinding wheel with a plurality of grinding wheels provided discretely in a ring shape attached to its tip, and a thickness measuring device for measuring the thickness of the workpiece held on the holding surface of the chuck table.

[0008] Specifically, in this grinding apparatus, while rotating both the chuck table and the spindle that hold the workpiece so that one side is exposed on the holding surface, the plurality of grinding wheels are pressed against one side of the workpiece, whereby one side of the workpiece is ground. And in this grinding apparatus, generally, when the thickness of the workpiece measured by the thickness measuring device reaches a predetermined thickness, the grinding of one side of the workpiece is terminated.

[0009] However, as described above, if one side of the workpiece is rough or has an uneven shape, it is difficult to accurately measure the thickness of the workpiece using the thickness measuring device. Further, when this thickness measuring device is a contact type, there is a risk that a malfunction may occur in the thickness measuring device when measuring the thickness of the workpiece.

[0010] Specifically, if one side of the workpiece is rough, the probe (measuring element) of the thickness measuring device that moves while contacting the rough surface may be worn. Also, if one side of the workpiece has an uneven shape, the measuring element of the thickness measuring device may bounce and break when moving from a convex part to a concave part, etc.

[0011] Therefore, in a grinding apparatus, one side of a workpiece may be ground without measuring the thickness of the workpiece. Specifically, in a grinding apparatus, for example, when the chuck table and the spindle are brought close to each other by a predetermined distance (grinding feed amount), grinding of one side of the workpiece may be terminated.

[0012] However, as described above, if one side of the workpiece is rough or has an uneven shape, the wear of a plurality of grinding wheels becomes severe. Therefore, when grinding one side of the workpiece so as to end at the time when the chuck table and the spindle are brought close to each other by a predetermined grinding feed amount, the thickness (finished thickness) of the workpiece after grinding may deviate from a predetermined thickness.

[0013] In view of these points, an object of the present invention is to grind one side of the workpiece so that the deviation of the finished thickness of the workpiece from a predetermined thickness is reduced.

Means for Solving the Problems

[0014] According to one aspect of the present invention, there is provided a grinding apparatus for grinding a workpiece, comprising: a chuck table for holding the workpiece on a holding surface; a spindle having a grinding wheel with a plurality of grinding wheels provided annularly and discretely mounted at a tip portion thereof; a thickness measuring device for measuring the thickness of the workpiece held on the holding surface of the chuck table; and a controller for controlling the chuck table, the spindle, and the thickness measuring device so as to grind the workpiece. The controller includes: a memory for storing a threshold value of a physical quantity that changes depending on a load when grinding one surface side of the workpiece; and a processor for controlling the chuck table, the spindle, and the thickness measuring device so as to grind the one surface side of the workpiece until the thickness of the workpiece measured by the thickness measuring device reaches a predetermined thickness, while rotating both the chuck table and the spindle that hold the workpiece on the holding surface so that the one surface side is exposed, and pressing the plurality of grinding wheels against the one surface side of the workpiece. The processor controls the thickness measuring device to perform measurement of the thickness of the workpiece after it is determined that the flatness of the one surface side of the workpiece has been improved based on a comparison between the actual value of the physical quantity and the threshold value. A grinding apparatus is provided.

[0015] According to another aspect of the present invention, there is provided a method for grinding a workpiece in a grinding apparatus including a chuck table for holding the workpiece on a holding surface, a spindle having a grinding wheel with a plurality of grinding wheels provided annularly and discretely mounted at a tip end thereof, and a thickness measuring device for measuring a thickness of the workpiece held on the holding surface of the chuck table, the method comprising: a holding step of holding the workpiece on the holding surface of the chuck table so that one surface side is exposed; a grinding step of grinding the one surface side of the workpiece by pressing the plurality of grinding wheels against the one surface side of the workpiece while rotating both the chuck table and the spindle after the holding step; the grinding step including a first grinding step of grinding the one surface side of the workpiece until it is determined that flatness of the one surface side of the workpiece is improved by referring to an actual value of a physical quantity that changes depending on a load when grinding the one surface side of the workpiece, without performing measurement of the thickness of the workpiece using the thickness measuring device; and a second grinding step of grinding the one surface side of the workpiece while performing the measurement until the measured thickness of the workpiece reaches a predetermined thickness, after the first grinding step.

[0016] According to still another aspect of the present invention, there is provided a program for causing a computer to execute a method for grinding a workpiece in a grinding apparatus including: a chuck table for holding the workpiece on a holding surface; a spindle having a grinding wheel with a plurality of grinding wheels provided annularly and discretely mounted at a tip portion thereof; a thickness measuring device for measuring a thickness of the workpiece held on the holding surface of the chuck table; and a controller for controlling the chuck table, the spindle, and the thickness measuring device so as to grind the workpiece. The method for grinding the workpiece includes: a holding step of holding the workpiece on the holding surface of the chuck table so that one surface side thereof is exposed; and a grinding step of grinding the one surface side of the workpiece by pressing the plurality of grinding wheels against the one surface side of the workpiece while rotating both the spindle and the chuck table. The grinding step includes: a first grinding step of grinding the one surface side of the workpiece until it is determined that the flatness of the one surface side of the workpiece has been improved by referring to an actual value of a physical quantity that changes depending on a load when grinding the one surface side of the workpiece, without performing measurement of the thickness of the workpiece using the thickness measuring device; and a second grinding step of grinding the one surface side of the workpiece while performing the measurement until the measured thickness of the workpiece reaches a predetermined thickness.

[0017] In the present invention, preferably, the physical quantity is an electric current supplied to a motor for rotating the chuck table or the spindle. Alternatively, in the present invention, preferably, the physical quantity is a load applied to the chuck table or the spindle. Further, in the present invention, preferably, the thickness measuring device is a contact type thickness measuring device.

Advantages of the Invention

[0018] In the present invention, after it is determined that the flatness on one side of the workpiece has been improved, the workpiece is ground on one side until the thickness of the workpiece measured while measuring the thickness of the workpiece using a thickness measuring instrument reaches a predetermined thickness. Therefore, in the present invention, one side of the workpiece can be ground so that the deviation from the predetermined thickness of the finished thickness of the workpiece is reduced.

Brief Description of the Drawings

[0019]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Embodiments for Carrying Out the Invention

[0020] Embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a perspective view schematically showing an example of a grinding apparatus, and FIG. 2 is a cross-sectional view schematically showing an example of the grinding apparatus shown in FIG. 1. The X-axis direction (front-rear direction) and Y-axis direction (left-right direction) shown in FIGS. 1 and 2 are directions orthogonal to each other on a horizontal plane, and the Z-axis direction (up-down direction) is a direction (vertical direction) orthogonal to the X-axis direction and Y-axis direction.

[0021] The grinding device 2 shown in FIGS. 1 and 2 has a base 4 that supports each component. On the upper surface of this base 4, a rectangular parallelepiped-shaped depression 4a extending along the X-axis direction is formed. And inside the depression 4a, an X-axis direction movement mechanism 6 for moving a chuck table 24, which will be described later, along the X-axis direction is provided.

[0022] This X-axis direction movement mechanism 6 has a pair of guide rails 8 each extending along the X-axis direction. Above the pair of guide rails 8, a rectangular parallelepiped-shaped X-axis movement plate 10 is attached in a slidable manner along the X-axis direction. Also, between the pair of guide rails 8, a screw shaft 12 extending along the X-axis direction is arranged.

[0023] And at the rear end of the screw shaft 12, a motor 14 for rotating the screw shaft 12 is connected. Also, on the outer peripheral surface of the screw shaft 12 where the screw thread is formed, a nut 16 for accommodating a large number of balls that circulate in response to the rotation of the screw shaft 12 is provided, and a ball screw is configured.

[0024] Also, the nut 16 is fixed to the lower surface side of the X-axis movement plate 10. Therefore, if the screw shaft 12 is rotated by the motor 14, the X-axis movement plate 10 moves along the X-axis direction together with the nut 16. Also, on the X-axis movement plate 10, a rotating body with a driven pulley 18 connected to the lower end and a motor (not shown) connected to a driving pulley (not shown) are provided.

[0025] Also, an endless belt (not shown) is wound around the driven pulley 18 and the driving pulley. Further, on the X-axis movement plate 10, an inclination adjustment mechanism having one fixed shaft (not shown) and two movable shafts 20 with variable lengths along their respective Z-axis directions is provided. And the fixed shaft and the two movable shafts 20 are connected to the lower surface side of the table base 22 and support the table base 22.

[0026] Further, a through hole (not shown) is formed in the center of the table base 22, and a rotating body with a driven pulley 18 connected to its lower end is passed through this through hole. The upper end of the rotating body is connected to the lower surface side of the disk-shaped chuck table 24. The table base 22 supports the chuck table 24 via a bearing (not shown), and a load measuring device 26 for measuring the load applied to the chuck table 24 is provided inside it.

[0027] When the motor connected to the driving pulley is operated to rotate the endless belt wound around the driven pulley 18, the chuck table 24 rotates along the circumferential direction of the chuck table 24 without the table base 22 rotating. Also, when the lengths of the two movable shafts 20 along the Z-axis direction in the tilt adjustment mechanism are adjusted, not only the tilt of the table base 22 but also the tilt of the chuck table 24 is adjusted.

[0028] The chuck table 24 has a disk-shaped frame body 24a made of ceramics or the like. This frame body 24a has a disk-shaped bottom wall and a cylindrical side wall standing upright from this bottom wall. And on the upper surface side of the frame body 24a, a disk-shaped recess defined by the bottom wall and the side wall is formed.

[0029] Note that the inner diameter of the side wall of the frame body 24a is smaller than the diameter of the workpiece 11 to be described later, and its outer diameter is larger than the diameter of the workpiece 11. Also, a flow path (not shown) that opens at the bottom surface of the recess is formed in the bottom wall of the frame body 24a, and this flow path communicates with a suction source (not shown) such as an ejector.

[0030] Furthermore, a disk-shaped porous plate 24b having a diameter approximately equal to the diameter of this recess is fixed to the recess formed on the upper surface side of the frame body 24a. This porous plate 24b is made of, for example, porous ceramics. Also, the upper surface of the porous plate 24b and the upper surface of the side wall of the frame body 24a have a shape corresponding to the side surface of a cone (a shape where the center protrudes more than the outer circumference).

[0031] When an aspiration source communicating with the flow path formed inside the frame body 24a is operated, a suction force acts on the space near the upper surface of the porous plate 24b. Therefore, the upper surface of the porous plate 24b and the upper surface of the side wall of the frame body 24a function as the holding surface 28 of the chuck table 24 (see FIG. 1).

[0032] For example, when the aspiration source is operated with the workpiece 11 placed on the holding surface 28 of the chuck table 24, the workpiece 11 is held on the holding surface 28 of the chuck table 24. The workpiece 11 is made of, for example, a semiconductor material such as silicon.

[0033] This workpiece 11 is manufactured, for example, by separating a portion located on one surface side of the ingot from the ingot using a laser beam having a wavelength that penetrates the material of the wire saw or ingot. Therefore, one surface 11a side of the workpiece 11 (specifically, the surface side newly exposed by separation from the ingot) becomes rough or has an uneven shape.

[0034] The arithmetic mean roughness (Ra) of the one surface 11a side of the workpiece 11 is, for example, 3.0 μm or more and 10.0 μm or less. The other surface 11b side of the workpiece 11 may be flatter than the one surface 11a side, or may be as rough as that side, or may have the same uneven shape as that side.

[0035] Furthermore, around the chuck table 24, a rectangular parallelepiped table cover 30 that surrounds the chuck table 24 so that its holding surface 28 is exposed is provided. The width of this table cover 30 (the length along the Y-axis direction) is approximately equal to the width of the depression 4a formed on the upper surface of the base 4. Also, dust and splash covers 32 that can expand and contract along the X-axis direction are provided in front of and behind the table cover 30.

[0036] Further, a square columnar support structure 34 is provided in a region of the upper surface of the base 4 that is located behind the depression 4a. A Z-axis direction movement mechanism 36 is provided on the front surface of this support structure 34. This Z-axis direction movement mechanism 36 has a pair of guide rails 38 that each extend along the Z-axis direction. And a slider 40 is provided on the front side of each of the pair of guide rails 38 in a slidable manner along the Z-axis direction (see FIG. 2).

[0037] Also, the front end portion of the slider 40 is fixed to the rear surface side of a rectangular parallelepiped-shaped Z-axis movement plate 42. Further, a screw shaft 44 that extends along the Z-axis direction is disposed between the pair of guide rails 38. And a motor 46 for rotating the screw shaft 44 is connected to the upper end portion of the screw shaft 44.

[0038] Also, a nut 48 that houses a large number of balls that circulate in response to the rotation of the screw shaft 44 is provided on the outer peripheral surface of the screw shaft 44 where the thread is formed, and a ball screw is configured. Also, the nut 48 is fixed to the rear surface side of the Z-axis movement plate 42. Therefore, if the screw shaft 44 is rotated by the motor 46, the Z-axis movement plate 42 moves along the Z-axis direction together with the nut 48.

[0039] A grinding unit 50 is provided on the front side of the Z-axis movement plate 42. This grinding unit 50 has a cylindrical support member 52 that is fixed to the front surface of the Z-axis movement plate 42. And a cylindrical spindle housing 54 that extends along the Z-axis direction is provided inside the support member 52.

[0040] Also, a cylindrical spindle 56 that extends along the Z-axis direction is provided inside the spindle housing 54 (see FIG. 2). This spindle 56 is supported by the spindle housing 54 in a rotatable manner, and its upper end portion (base end portion) is connected to a motor 58.

[0041] Further, the spindle 56 projects downward through a through-hole formed at the bottom of the spindle housing 54, and the lower end portion (tip portion) thereof is a disc-shaped mount 60. And an annular grinding wheel 62 having an outer diameter approximately equal to the diameter of the mount 60 is mounted on the lower surface side of the mount 60 using a fixing member (not shown) such as a bolt.

[0042] This grinding wheel 62 includes a plurality of grinding grains 62a and a wheel base 62b having a lower surface on which the plurality of grinding grains 62a are discretely arranged in an annular shape. When the motor 58 is operated, the mount 60 and the grinding wheel 62 rotate together with the spindle 56 with a straight line along the Z-axis direction as the rotation axis.

[0043] The plurality of grinding grains 62a have abrasive grains such as diamond or cBN dispersed in a binder such as vitrified bond or resin bond. The wheel base 62b is made of a metal material such as stainless steel or aluminum, for example.

[0044] Furthermore, a nozzle of a grinding fluid supply unit is provided in the vicinity of the grinding wheel 62. This nozzle supplies a liquid (grinding fluid) such as pure water at a predetermined flow rate to the contact point (processing point) between the plurality of grinding grains 62a and the one surface 11a of the workpiece 11 when grinding one surface 11a side of the workpiece 11 with the plurality of grinding grains 62a.

[0045] Also, in a region located on the side of the depression 4a on the upper surface of the base 4 and close to the grinding unit 50, a thickness measuring device 64 for measuring the thickness of the workpiece 11 held on the holding surface 28 of the chuck table 24 is provided. This thickness measuring device 64 is, for example, a contact type thickness measuring device and has a pair of height gauges 64a, 64b for measuring the height of the position where each measuring element contacts.

[0046] And the measuring element of the height gauge 64a can be arranged to contact one surface 11a of the workpiece 11 held on the holding surface 28 of the chuck table 24. Also, the measuring element of the height gauge 64b can be arranged to contact the holding surface 28 of the chuck table 24 (specifically, the upper surface of the side wall of the frame body 24a).

[0047] Therefore, prior to or during the grinding of one surface 11a side of the workpiece 11, by arranging the measuring elements of the respective height gauges 64a and 64b in this way, the thickness of the workpiece 11 can be measured by the thickness measuring device 64.

[0048] Furthermore, the grinding device 2 includes a computer for controlling each component of the grinding device 2 described above. FIG. 3 is a block diagram schematically showing the hardware included in this computer. The computer 66 shown in FIG. 3 includes an output device 70, a controller 72, an input device 74, and a communication interface 76 that are connected via a bus 68 so as to be able to exchange electrical signals with each other.

[0049] The output device 70 outputs information and the like regarding the workpiece 11 to be ground in the grinding device 2. This output device 70 includes at least one of a display, a printer, or a speaker, and is used, for example, when notifying the operator of the thickness of the workpiece 11 measured by the thickness measuring device 64.

[0050] The controller 72 controls each component of the grinding device 2 described above. This controller 72 includes a processor 78 and a memory 80. Furthermore, the memory 80 includes a main storage device 80a with excellent rewriting speed and an auxiliary storage device 80b with a large storage capacity.

[0051] Note that the processor 78 is composed of, for example, a CPU (Central Processing Unit) or the like. The main memory device 80a is composed of, for example, a volatile memory such as a DRAM (Dynamic Random Access Memory) or an SRAM (Static Random Access Memory). The auxiliary storage device 80b is composed of, for example, a non-volatile memory such as an SSD (Solid State Drive) (NAND-type flash memory) or an HDD (Hard Disk Drive) (magnetic storage device).

[0052] The main memory device 80a stores data that is frequently rewritten by the processor 78. The auxiliary storage device 80b stores a program for causing the processor 78 to execute a specific process and data used in the operations of the processor 78. For example, the auxiliary storage device 80b stores data used to determine whether or not the flatness of one surface 11a side of the workpiece 11 has been improved.

[0053] Note that if the flatness of one surface 11a side of the workpiece 11 is improved, the contact area between the plurality of grinding wheels 62a and the one surface 11a of the workpiece 11 when grinding the one surface 11a side of the workpiece 11 increases. When the contact area between the two increases, the load when grinding the one surface 11a side of the workpiece 11 increases.

[0054] Therefore, whether or not the flatness of one surface 11a side of the workpiece 11 has been improved can be determined by comparing, for example, a physical quantity that changes depending on the load when grinding the one surface 11a side of the workpiece 11 (for example, the current supplied to the motor 58 or the load applied to the chuck table 24 measured by the load measuring device 26) with a threshold value of this physical quantity. The auxiliary storage device 80b can store, for example, the threshold value of the physical quantity as data used for this determination.

[0055] The processor 78 reads and executes various programs stored in the auxiliary storage device 80b. For example, the processor 78 reads and executes a program for grinding the one surface 11a side of the workpiece 11 from the auxiliary storage device 80b so that the deviation from a predetermined thickness of the finish thickness of the workpiece 11 becomes small. Note that a method for grinding a workpiece for grinding the workpiece 11 according to this program will be described later.

[0056] The input device 74 inputs information and the like regarding the workpiece 11 to be ground in the grinding device 2 to the controller 72. This input device 74 includes at least one of a keyboard, a mouse, a touch pad, or a microphone, and is used, for example, when inputting data (for example, the threshold value of the above physical quantity) used for determining whether or not the flatness of the one surface 11a side of the workpiece 11 has been improved to the controller 72.

[0057] The communication interface 76 includes at least one of a communication circuit (such as an analog-digital conversion circuit (ADC) and a digital-analog conversion circuit (DAC)) and an input / output (I / O) port. This communication interface 76 is used, for example, when inputting a program (for example, a program for grinding the one surface 11a side of the workpiece 11 so that the deviation from a predetermined thickness of the finish thickness of the workpiece 11 becomes small) recorded on a non-temporary recording medium such as a portable USB (Universal Serial Bus) flash drive to the controller 72.

[0058] FIG. 4 is a flowchart schematically showing an example of a method for grinding a workpiece for grinding the one surface 11a side of the workpiece 11 so that the deviation from a predetermined thickness of the finish thickness of the workpiece 11 becomes small. In this method, first, the workpiece 11 is held on the holding surface 28 of the chuck table 24 so that the one surface 11a side is exposed (holding step S1).

[0059] In the holding step S1, the workpiece 11 is placed on the holding surface 28 of the chuck table 24 such that one surface 11a faces upward. Then, the processor 78 operates a suction mechanism that communicates with the porous plate 24b. As a result, a suction force acts on the workpiece 11, and the workpiece 11 is held on the holding surface 28 of the chuck table 24 with one surface 11a side exposed.

[0060] After the holding step S1, while rotating both the chuck table 24 and the spindle 56, a plurality of grinding wheels 62a are pressed against one surface 11a side of the workpiece 11 to grind one surface 11a side of the workpiece 11 (grinding step S2). FIG. 5 is a flowchart schematically showing a specific example of the grinding step S2.

[0061] In the grinding step S2 shown in FIG. 5, first, without measuring the thickness of the workpiece 11 using the thickness measuring device 64, one surface 11a side of the workpiece 11 is ground (first grinding step S21). In this first grinding step S21, the processor 78 operates the motor 14 so as to position the center of one surface 11a of the workpiece 11 directly below the locus when the grinding wheel 62 is rotated together with the spindle 56.

[0062] Next, the processor 78 operates the motor for rotating the driven pulley 18 and the motor 58 so as to rotate both the chuck table 24 and the grinding wheel 62. Next, while rotating both the chuck table 24 and the grinding wheel 62, the processor 78 controls the motor 46 and the grinding fluid supply unit so as to lower the grinding wheel 62 and supply the grinding fluid to one surface 11a of the workpiece 11.

[0063] Thereby, one surface 11a side of the workpiece 11 is ground. If it is determined that the flatness of one surface 11a side of the workpiece 11 has not been improved (step S22: NO), this grinding, that is, the first grinding step S21 is continued.

[0064] Here, this determination is made by the processor 78 comparing a physical quantity that changes depending on the load when grinding one surface 11a side of the workpiece 11 (for example, the current supplied to the motor 58 or the load applied to the chuck table 24 measured by the load measuring device 26) with a threshold value of the physical quantity stored in the memory 80 (specifically, the auxiliary storage device 80b).

[0065] For example, when the physical quantity is the current supplied to the motor 58, the processor 78 determines that the flatness of one surface 11a side of the workpiece 11 has improved when the actual value of this current becomes equal to or greater than the threshold value. Also, when the physical quantity is the load applied to the chuck table 24 measured by the load measuring device 26, the processor 78 determines that the flatness of one surface 11a side of the workpiece 11 has improved when the actual value of this load becomes equal to or greater than the threshold value.

[0066] And if it is determined that the flatness of one surface 11a side of the workpiece 11 has improved (step S22: YES), while measuring the thickness of the workpiece 11 using the thickness measuring device 64, the one surface 11a side of the workpiece 11 is ground until the measured thickness of the workpiece 11 reaches a predetermined thickness (second grinding step S23).

[0067] In this second grinding step S23, for example, while grinding one surface 11a side of the workpiece 11 in the same manner as in the first grinding step S21, the processor 78 operates the thickness measuring device 64 so that the measuring element of the height gauge 64a contacts one surface 11a of the workpiece 11 and the measuring element of the height gauge 64b contacts the holding surface 28 of the chuck table 24.

[0068] Thereby, while measuring the thickness of the workpiece 11 by the thickness measuring device 64, one surface 11a side of the workpiece 11 is ground. Also, the thickness of the workpiece 11 measured by the thickness measuring device 64 is input to the controller 72.

[0069] Then, when the measured thickness of the workpiece 11 reaches a predetermined thickness, the processor 78 stops the operations of the motor and the motor 46 for rotating the driven pulley 18 so as to stop the grinding on the one surface 11a side of the workpiece 11, and operates the motor 46 so as to separate the plurality of grinding wheels 62a from the workpiece 11.

[0070] In the grinding apparatus 2, after it is determined that the flatness on the one surface 11a side of the workpiece 11 has been improved, the one surface 11a side of the workpiece 11 is ground while measuring the thickness of the workpiece 11 using the thickness measuring device 64 until the measured thickness of the workpiece 11 reaches a predetermined thickness. Therefore, in the grinding apparatus 2, the one surface 11a side is ground so that the deviation from the predetermined thickness of the workpiece 11 is reduced, and the probability that the contact type thickness measuring device 64 is damaged can be reduced.

[0071] Note that the above-described content is one aspect of the present invention, and the present invention is not limited to the above-described content. For example, the thickness measuring device in the present invention is not limited to the contact type thickness measuring device 64, and a non-contact type thickness measuring device may be used.

[0072] Also, the workpiece in the present invention is not limited to a wafer, and for example, an ingot may be used. That is, in the present invention, for example, one surface side of the ingot remaining after separating the wafer (specifically, the surface side newly exposed by separating the wafer) may be ground.

[0073] Further, the above-described physical quantity in the present invention is not limited to the current supplied to the motor 58 or the load applied to the chuck table 24, and for example, the current supplied to the motor for rotating the driven pulley 18 or the load applied to the spindle 56 may be used.

[0074] In addition, the structures and methods according to the above-described embodiments can be appropriately changed and implemented without departing from the scope of the object of the present invention.

Explanation of Reference Numerals

[0075] 2: Grinding apparatus 4: Base (4a: Depression) 6: X-axis movement mechanism 8: Guide rail 10: X-axis moving plate 11: Workpiece (11a: One surface, 11b: The other surface) 12: Screw shaft 14: Motor 16: Nut 18: Driven pulley 20: Movable shaft 22: Table base 24: Chuck table (24a: Frame body, 24b: Porous plate) 26: Load measuring device 28: Holding surface 30: Table cover 32: Dust and splash-proof cover 34: Support structure 36: Z-axis movement mechanism 38: Guide rail 40: Slider 42: Z-axis moving plate 44: Screw shaft 46: Motor 48: Nut 50: Grinding unit 52: Support member 54: Spindle housing 56: Spindle 58: Motor 60: Mount 62: Grinding wheel (62a: Grinding stone, 62b: Wheel base) 64: Thickness measuring device (64a, 64b: Height gauge) 66: Computer 68: Bus 70: Output device 72: Controller 74: Input device 76: Communication interface 78: Processor 80: Memory (80a: Main memory device, 80b: Auxiliary memory device)

Claims

1. A grinding apparatus for grinding a workpiece, comprising: a chuck table for holding the workpiece on a holding surface; a spindle having a grinding wheel with a plurality of grinding wheels provided annularly and discretely mounted at a tip; a thickness measuring device for measuring the thickness of the workpiece held on the holding surface of the chuck table; a controller for controlling the chuck table, the spindle, and the thickness measuring device so as to grind the workpiece; The controller includes: a memory for storing a threshold value of a physical quantity that changes depending on a load when grinding one surface side of the workpiece; while rotating both the chuck table and the spindle that hold the workpiece on the holding surface so that one surface side is exposed, by pressing the plurality of grinding wheels against one surface side of the workpiece, a processor for controlling the chuck table, the spindle, and the thickness measuring device so as to grind one surface side of the workpiece until the thickness of the workpiece measured by the thickness measuring device reaches a predetermined thickness; The processor controls the thickness measuring device to measure the thickness of the workpiece after it is determined that the flatness of one surface side of the workpiece has been improved based on a comparison between the actual value of the physical quantity and the threshold value. A grinding apparatus.

2. The grinding apparatus according to claim 1, wherein the physical quantity is an electric current supplied to a motor for rotating the chuck table or the spindle.

3. The grinding apparatus according to claim 1, wherein the physical quantity is a load applied to the chuck table or the spindle.

4. The grinding apparatus according to any one of claims 1 to 3, wherein the thickness measuring device is a contact type thickness measuring device.

5. A method for grinding a workpiece in a grinding apparatus comprising a chuck table for holding the workpiece on a holding surface, a spindle having a grinding wheel with a plurality of grinding wheels provided annularly and discretely mounted at a tip, and a thickness measuring device for measuring the thickness of the workpiece held on the holding surface of the chuck table, the method comprising: a holding step of holding the workpiece on the holding surface of the chuck table so that one surface side is exposed; After the holding step, while rotating both the chuck table and the spindle, a grinding step of grinding one surface side of the workpiece by pressing the plurality of grinding wheels against the one surface side of the workpiece is provided. The grinding step includes: A first grinding step of grinding one surface side of the workpiece until it is determined that the flatness of the one surface side of the workpiece is improved by referring to the actual value of a physical quantity that changes depending on the load when grinding the one surface side of the workpiece without performing measurement of the thickness of the workpiece using the thickness measuring device. After the first grinding step, a second grinding step of grinding one surface side of the workpiece while performing the measurement until the measured thickness of the workpiece reaches a predetermined thickness is provided. A method for grinding a workpiece.

6. A program for causing a computer to execute a method for grinding a workpiece in a grinding apparatus including a chuck table for holding the workpiece on a holding surface, a spindle having a grinding wheel with a plurality of grinding wheels provided annularly and discretely attached to a tip portion, a thickness measuring device for measuring the thickness of the workpiece held on the holding surface of the chuck table, and a computer including a controller for controlling the chuck table, the spindle, and the thickness measuring device so as to grind the workpiece, The method for grinding the workpiece includes: A holding step of holding the workpiece on the holding surface of the chuck table so that one surface side is exposed; After the holding step, while rotating both the spindle and the chuck table, a grinding step of grinding one surface side of the workpiece by pressing the plurality of grinding wheels against the one surface side of the workpiece is provided. The grinding step includes: A first grinding step of grinding one surface side of the workpiece until it is determined that the flatness of the one surface side of the workpiece is improved by referring to the actual value of a physical quantity that changes depending on the load when grinding the one surface side of the workpiece without performing measurement of the thickness of the workpiece using the thickness measuring device. After the first grinding step, a second grinding step of grinding one surface side of the workpiece while performing the measurement until the measured thickness of the workpiece reaches a predetermined thickness is included.

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