JP7636945B2 - Method for grinding a workpiece - Google Patents

Description

The present invention relates to a grinding method for grinding bonded workpieces such as bonded wafers.

In grinding machines, a method is used in which the inclination of the holding surface and the grinding wheel is adjusted based on the thickness distribution of the wafer after grinding so that the next wafer can be ground flat. However, wafers ground before this adjustment cannot be ground flat and have thickness variations, which may result in defects. Therefore, a method known as regrind is used in which grinding is stopped once during finish grinding to measure the thickness distribution of the workpiece, the inclination of the holding surface and the grinding wheel is adjusted, and grinding is then resumed (see, for example, Patent Document 1).

JP 2013-119123 A

However, pausing grinding to regrind is inefficient. In addition, in the case of a workpiece in which a second plate-like object to be ground is stacked on a first plate-like object that serves as a support substrate such as glass or silicon, if the shape of the support substrate has thickness variations, the second plate-like object cannot be ground uniformly even if the finished thickness of the entire workpiece is finished to be flat. Therefore, a processing method has been proposed in which the radial thickness distribution of the first plate-like object that serves as the support substrate in the bonded workpieces is measured after rough grinding, the inclination of the grinding surface and holding surface of the grinding wheel for finish grinding is adjusted according to the shape, and finish grinding is performed to make the thickness of the second plate-like object uniform. However, depending on the bonded workpieces, there is a problem that the thickness distribution of the first plate-like object cannot be measured by a non-contact measurement unit because the bonded surface of the bonded workpieces has devices or circuits including metal patterns formed on it, which does not transmit light.

The present invention was made in consideration of these problems, and its purpose is to provide a method for grinding a workpiece that can grind a second plate-like object attached to a first plate-like object to a uniform thickness without reducing processing efficiency.

In order to solve the above-mentioned problems and achieve the object, the present invention provides a method for grinding a workpiece, which is a method for grinding a second plate-like object of a workpiece in which a first plate-like object is stacked on top of a second plate-like object, to a finish thickness, and which is a method for grinding a plurality of workpieces one by one in sequence so that the second plate-like object in the workpiece has a uniform thickness. The method for grinding a workpiece includes a holding step of holding the first plate-like object on a holding surface of a holding table, a rough grinding step of grinding the second plate-like object with a rough grinding wheel, and a grinding step of grinding the second plate-like object with a rough grinding wheel after the rough grinding step. a post-rough grinding measurement step of measuring the thickness of the second plate-like object at a plurality of locations in the radial direction and measuring the thickness distribution of the second plate-like object; a finish grinding step of grinding the second plate-like object on which the rough grinding step and the post-rough grinding measurement step have been performed with a finish grinding wheel; a post-finish grinding measurement step of measuring the thickness of the second plate-like object at a plurality of locations in the radial direction after the finish grinding step has been performed and measuring the thickness distribution of the second plate-like object; and an inclination adjustment step of relatively adjusting the inclination between the holding surface and the grinding surface of the finish grinding wheel so that the thickness distribution of the second plate-like object becomes uniform. When grinding the first workpiece, the finish grinding step and the post-finish grinding measurement step are performed twice each, and the first finish grinding step is performed such that the grinding amount does not reach the final planned finish grinding thickness, the first post-finish grinding measurement step is performed after the first finish grinding step is performed, the inclination adjustment step is performed to adjust the inclination in accordance with the thickness distribution of the second plate-like object measured in the first post-finish grinding measurement step, the second finish grinding step is performed after the inclination is adjusted in the inclination adjustment step, and the second finish grinding step is performed. When the second post-finish grinding measurement step is subsequently performed to grind the second or subsequent workpieces, the inclination adjustment step calculates a difference between the thickness distribution of the second plate-like object measured in the post-rough grinding measurement step of the workpiece that has already undergone the finish grinding step and the thickness distribution of the second plate-like object measured in the post-rough grinding measurement step of the workpiece that will soon undergo the finish grinding step, adjusts the inclination of the workpiece that has already undergone the finish grinding step during the finish grinding step to a new inclination in accordance with the difference, and adjusts the inclination so that the upcoming finish grinding step is performed with the new inclination.

When grinding the second or subsequent workpiece, the inclination adjustment step may take into account the thickness distribution of the second plate-like object measured in the measurement step after finish grinding of the workpiece that has been subjected to the finish grinding step, and adjust the inclination so that the thickness of the second plate-like object becomes more uniform.

The present invention can grind a second plate-like object attached to a first plate-like object to a uniform thickness without reducing processing efficiency.

FIG. 1 is a perspective view showing an example of the configuration of a processing device for carrying out a method for grinding a workpiece according to an embodiment. FIG. 2 is a cross-sectional view showing a rough grinding unit and a finish grinding unit of the processing apparatus of FIG. FIG. 3 is a cross-sectional view showing a non-contact measuring unit of the processing apparatus of FIG. FIG. 4 is a flowchart showing an example of a processing procedure of the method for grinding a workpiece according to the embodiment. FIG. 5 is an explanatory diagram for explaining the process of the method for grinding a workpiece according to the embodiment. FIG. 6 is an explanatory diagram for explaining the process of the method for grinding a workpiece according to the embodiment.

The following describes in detail the form (embodiment) for carrying out the present invention with reference to the drawings. The present invention is not limited to the contents described in the following embodiment. The components described below include those that a person skilled in the art can easily imagine and those that are substantially the same. Furthermore, the configurations described below can be combined as appropriate. Various omissions, substitutions, or modifications of the configuration can be made without departing from the spirit of the present invention.

[Embodiment]
A method for grinding a workpiece according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view showing a configuration example of a processing device 1 for carrying out the method for grinding a workpiece according to the embodiment. FIG. 2 is a cross-sectional view showing a rough grinding unit 30 and a finish grinding unit 40 of the processing device of FIG. 1. FIG. 3 is a cross-sectional view showing a non-contact measurement unit 60 of the processing device 1 of FIG. 1. As shown in FIG. 1, the processing device 1 includes a device body 10, a holding table 20, a turntable 25, a rough grinding unit 30, a finish grinding unit 40, a contact measurement unit 50, a non-contact measurement unit 60, a control unit 70, cassettes 81 and 82, an alignment unit 83, a carry-in unit 84, a carry-out unit 85, a cleaning unit 86, and a carry-in/out unit 87.

In this embodiment, the workpiece 100 to be processed by the processing device 1 includes a first plate-like object 110 and a second plate-like object 120 stacked on the first plate-like object 110, as shown in Fig. 1. In addition, in this embodiment, the workpiece 100 further includes a bonding member that bonds the first plate-like object 110 and the second plate-like object 120 at an interface 130 between the first plate-like object 110 and the second plate-like object 120. In this embodiment, the first plate-like object 110 and the second plate-like object 120 are wafers such as disk-shaped semiconductor wafers and optical device wafers that use, for example, silicon, sapphire, silicon carbide (SiC), gallium arsenide, lithium tantalate ( _LiTaO3 , LT), glass, or the like as a base material. In this embodiment, the laminating member is, for example, an oxide film, polyvinyl alcohol (PVA), or a resin such as epoxy.

As shown in FIG. 1, the turntable 25 is a disk-shaped table provided on the upper surface of the device body 10, and is rotatable in a horizontal plane parallel to the XY plane, and is rotated at a predetermined timing. On this turntable 25, for example, three holding tables 20 are arranged at equal intervals, for example at a phase angle of 120°. These three holding tables 20 are moved sequentially to a loading/unloading position 201, a rough grinding position 202, a finish grinding position 203, and a loading/unloading position 201 by the rotation of the turntable 25.

As shown in Figs. 2 and 3, each of the three holding tables 20 includes a disk-shaped frame 22 with a recess formed therein and a disk-shaped suction section 23 fitted into the recess. The frame 22 is formed in a disk shape from stainless steel or the like. The suction section 23 is formed from a porous ceramic containing alumina with a large number of porous holes. The suction section 23 is connected to a suction source 27 via a suction path 26. The upper surface of the suction section 23 of each of the three holding tables 20 is a holding surface 21 on which the workpiece 100 is placed and which suction-holds the placed workpiece 100. The holding surface 21 suction-holds the first plate-shaped object 110 side (lower side) of the placed workpiece 100, for example, on which the workpiece 100 is placed with the second plate-shaped object 120 side, which is the surface to be processed (surface to be ground), facing upward.

In this embodiment, as shown in FIG. 2, the holding surface 21 and the upper surface of the frame 22 of these three holding tables 20 are formed into a conical surface with a slightly lower outer periphery and a vertex at the center 28, which is the center of rotation of the holding table 20. In the example shown in FIG. 2 and FIG. 3, the holding surface 21 is inclined by an inclination angle θ1 with respect to the bottom surface of the cone that forms the holding surface 21. Note that the holding surface 21 is not limited to this in the present invention, and may be formed flat.

These three holding tables 20 are connected to a rotary drive source (not shown) on the turntable 25, independently of the turntable 25, and are provided so as to be rotatable about a predetermined rotation axis passing through the center 28 of the holding table 20 by the rotary drive source (not shown). In addition, below these three holding tables 20, a rotary axis adjustment unit 29 is provided that tilts the rotation axis of the holding table 20 with respect to the Z-axis direction parallel to the vertical direction. The rotary axis adjustment unit 29 is used to adjust the inclination of the holding surface 21 of the holding table 20 when rough grinding is performed by the rough grinding unit 30 described later, or when finish grinding is performed by the finish grinding unit 40. In the example shown in Figures 2 and 3, the rotary axis adjustment unit 29 tilts the entire holding table 20 by an inclination angle θ2 with respect to the horizontal plane. In this embodiment, as shown in Figures 2 and 3, the tilt angle θ2 is treated as a positive value when the direction of the center 28 of the rotation axis of the holding table 20 is tilted away from the rotation axis of the rough grinding wheel 33 of the rough grinding unit 30 and the finish grinding wheel 43 of the finish grinding unit 40, which will be described later, and is treated as a negative value when the direction is tilted toward the center 28.

As shown in Figs. 1 and 2, the rough grinding unit 30 is attached to the lower end of the spindle 31, and rotates the rough grinding wheel 33, which has rough grinding stones 32 arranged in a ring shape. While rotating the rough grinding wheel 33, the rough grinding feed unit 34 presses the second plate-like object 120 side of the workpiece 100 held on the holding table 20 positioned at the rough grinding position 202 along the grinding feed direction (Z-axis direction parallel to the vertical direction), thereby roughly grinding the second plate-like object 120 side of the workpiece 100 with the rough grinding wheel 33. The rough grinding wheel 33 roughly grinds the workpiece 100 along the rough grinding surface 35, forming the processed surface (ground surface) of the workpiece 100 parallel to the rough grinding surface 35.

As shown in Figs. 1 and 2, the finish grinding unit 40 is attached to the lower end of the spindle 41, and while rotating the finish grinding wheel 43 on which the finish grinding stones 42 are arranged in a ring shape, the finish grinding wheel 43 presses the finish grinding feed unit 44 along the grinding feed direction against the second plate-like object 120 side of the roughly ground workpiece 100 held on the holding table 20 positioned at the finish grinding position 203, thereby finish-grinding the second plate-like object 120 side of the workpiece 100 with the finish grinding wheel 43. The finish grinding wheel 43 finish-grinds the workpiece 100 along the finish grinding surface 45, forming the workpiece 100's workpiece surface (grinding surface) parallel to the finish grinding surface 45.

The rough grinding wheel 33 uses the rough grinding wheel 32, which is made of abrasive grains with a larger grain size than the finish grinding wheel 42, to grind the second plate-like object 120 side of the workpiece 100 more roughly than the finish grinding wheel 43. The finish grinding wheel 43 uses the finish grinding wheel 42, which is made of abrasive grains with a smaller grain size than the rough grinding wheel 32, to grind the second plate-like object 120 side of the workpiece 100 more finely and flatly than the rough grinding wheel 33.

In this embodiment, the rough grinding unit 30 and the finish grinding unit 40 both grind the second plate-like object 120 side of the workpiece 100 on the holding table 20 while supplying a grinding fluid such as pure water to the second plate-like object 120 side of the workpiece 100.

In this embodiment, the contact measurement unit 50 is provided at two locations, near the rough grinding position 202 and near the finish grinding position 203. As shown in Figure 1, the contact measurement unit 50 is equipped with two contact probes 51 and 52 that measure the height of the contact position. Note that the contact measurement unit 50 is not shown in Figures 2 and 3. In the contact measurement unit 50, one probe 51 measures the height of the holding surface 21 of the holding table 20 positioned at the rough grinding position 202 or the finish grinding position 203, and the other probe 52 measures the height of the upper surface of the area slightly inside the outer edge of the workpiece 100 on the second plate-like object 120 side held on the holding surface 21 of the holding table 20, and measures the thickness of the area slightly inside the outer edge of the workpiece 100 based on the difference between the height measured by one probe 51 and the height measured by the other probe 52, that is, the total value of the thickness of the first plate-like object 110 and the thickness of the second plate-like object 120, and transmits the thickness measurement result to the control unit 70.

The non-contact measurement unit 60 includes a plurality of optical sensors 61 (three in the example shown in FIG. 3) arranged radially above the holding surface 21 of the holding table 20 positioned at the rough grinding position 202 and facing the holding surface 21, as shown in FIG. 3. The optical sensor 61 irradiates light such as laser light of a wavelength that is reflected by the upper surface of the second plate-like object 120 and the lower surface of the second plate-like object 120 toward the workpiece 100, receives the interference wave of this light, and measures the thickness of the second plate-like object 120 at the position where the optical sensor 61 emits and receives the light based on the received interference wave. In this embodiment, reflection by the lower surface of the second plate-like object 120 refers to reflection by the boundary surface 130 between the first plate-like object 110 and the second plate-like object 120, which does not include the layer of the bonding material. The non-contact measurement unit 60 can measure the radial thickness distribution of the second plate-like object 120 using multiple optical sensors 61.

The control unit 70 controls the operation of various components of the processing device 1 to cause the processing device 1 to perform the rough grinding process and the finish grinding process on the second plate-like object 120 side of the workpiece 100, thereby causing the processing device 1 to perform the grinding method for the workpiece according to the embodiment.

In this embodiment, the control unit 70 includes a computer system. The computer system included in the control unit 70 includes an arithmetic processing device having a microprocessor such as a CPU (Central Processing Unit), a storage device having a memory such as a ROM (Read Only Memory) or a RAM (Random Access Memory), and an input/output interface device. The arithmetic processing device of the control unit 70 performs arithmetic processing according to a computer program stored in the storage device of the control unit 70, and outputs control signals for controlling the processing device 1 to each component of the processing device 1 via the input/output interface device of the control unit 70.

As shown in FIG. 1, the cassettes 81 and 82 are containers for storing multiple workpieces 100. The alignment unit 83 is a table on which the workpiece 100 removed from the cassette 81 is temporarily placed and its center is aligned.

The carry-in unit 84 has a suction pad, and adsorbs and holds the workpiece 100 before grinding that has been aligned by the alignment unit 83, and carries it onto the holding table 20 positioned at the carry-in/carry-out position 201. The carry-out unit 85 adsorbs and holds the workpiece 100 after grinding that is held on the holding table 20 positioned at the carry-in/carry-out position 201, and carries it out to the cleaning unit 86. The cleaning unit 86 cleans the workpiece 100 after grinding, and removes contamination such as grinding debris adhering to the ground workpiece surface (grinding surface).

As shown in FIG. 1, the carry-in/out unit 87 is, for example, a robot pick equipped with a circular hand, and transports the workpiece 100 by suction and holding it with the circular hand. Specifically, the carry-in/out unit 87 carries the workpiece 100 before grinding from the cassettes 81 and 82 to the alignment unit 83, and carries the workpiece 100 after grinding from the cleaning unit 86 to the cassettes 81 and 82.

Next, this specification describes the processing of the grinding method of the workpiece according to the embodiment with reference to the drawings. The processing of the grinding method of the workpiece according to the embodiment is performed by the processing device 1. FIG. 4 is a flowchart showing an example of the processing procedure of the grinding method of the workpiece according to the embodiment. FIG. 5 and FIG. 6 are explanatory diagrams explaining the processing of the grinding method of the workpiece according to the embodiment.

The grinding method of the workpiece according to the embodiment is a method in which the processing device 1 sequentially grinds the second plate-like object 120 in the workpiece 100 one by one of the same type of workpieces 100 stored in the cassettes 81 and 82 so that the thickness is uniform, and the grinding process of the first workpiece 100 and the grinding process of the second and subsequent workpieces 100 have different processing procedures. The grinding process of the first workpiece 100 is Yes in step 1004 of FIG. 4, and after performing each of the processes of the finish grinding step 1006 (semi-finish grinding step) in which the grinding amount is approximately halved and the post-finish grinding measurement step 1007 (post-semi-finish grinding step) once each, the process goes through Yes in step 1008 of FIG. 4 and performs the processes from the tilt adjustment step 1005 onwards. The grinding process of the second and subsequent workpieces 100 is No in steps 1004 and 1008 in FIG. 4, and the processes of the finish grinding step 1006 (semi-finish grinding step) in which the grinding amount is reduced by about half and the post-finish grinding measurement step 1007 (post-semi-finish grinding step) are not performed, and the processes of the inclination adjustment step 1005 and subsequent steps are performed. The grinding process of the first workpiece 100 is shown in FIG. 5. The grinding process of the second and subsequent workpieces 100 is shown in FIG. 6. In the grinding method of the workpiece according to the embodiment, the grinding process (steps 1001 to 1003, 1005 to 1007) of the second plate-like object 120 in the second and subsequent workpieces 100 is repeatedly performed until the grinding process of all the workpieces 100 is completed (No in step 1009), and when the grinding process of all the workpieces 100 is completed (Yes in step 1009), the process is terminated.

First, the grinding process of the first workpiece 100 will be described with reference to Figures 4 and 5. The grinding process of the first workpiece 100 in the grinding method of the workpiece according to the embodiment includes a holding step 1001, a rough grinding step 1002, a measurement step after rough grinding 1003, an inclination adjustment step 1005, a finish grinding step 1006, and a measurement step after finish grinding 1007, as shown in Figures 4 and 5. In the grinding process of the first workpiece 100, the finish grinding step 1006 includes a semi-finish grinding step in which the grinding amount performed before the inclination adjustment step 1005 is set to about half the thickness of the final finish grinding planned thickness, and a main finish grinding step performed after the semi-finish grinding step and the inclination adjustment step 1005. In addition, the post-finish grinding measurement step 1007 includes a post-semi-finish grinding measurement step that is performed after the semi-finish grinding step and before the inclination adjustment step 1005, and a post-finish grinding measurement step that is performed after the inclination adjustment step 1005 and after the final grinding step.

The holding step 1001 is a step of holding the first plate-like object 110 side of the workpiece 100 on the holding surface 21 of the holding table 20. In the holding step 1001, the control unit 70 places the workpiece 100 with the second plate-like object 120 side facing upward on the holding surface 21 of the holding table 20 positioned at the loading/unloading position 201 by the loading unit 84, and introduces negative pressure from the suction source 27 through the suction path 26 to the holding surface 21 of the holding table 20, thereby suction-holding the first plate-like object 110 side of the workpiece 100 on the holding surface 21 of the holding table 20.

In the rough grinding step 1002, the second plate-like object 120 is roughly ground with the rough grinding wheel 33. In the rough grinding step 1002, the control unit 70 first moves the holding table 20, which has been suction-held on the holding surface 21 of the workpiece 100 by the holding step 1001, from the loading/unloading position 201 to the rough grinding position 202 by rotating the turntable 25. In the rough grinding step 1002, the control unit 70 then measures the overall approximate thickness of the workpiece 100 with the contact measurement unit 50, and then rotates the spindle 31 to rotate the rough grinding wheel 33, as shown in Fig. 2, and presses the rough grinding wheel 33 along the grinding feed direction against the second plate-like object 120 side of the workpiece 100 held on the holding table 20 positioned at the rough grinding position 202 and inclined by a predetermined inclination angle (in the example shown in Fig. 2, the inclination angle θ2) relative to the horizontal plane by the rotation axis adjustment unit 29, thereby roughly grinding the second plate-like object 120 with the rough grinding wheel 33. By rough grinding the second plate-like object 120 in this way in the rough grinding step 1002, the processing device 1 reduces the overall thickness of the second plate-like object 120 as shown in Fig. 5. In the rough grinding step 1002, in this embodiment, the second plate-like object 120 is thinned to a thickness of, for example, about 90 to 100 μm.

The post-rough grinding measurement step 1003 is a step in which the thickness of the second plate-like object 120 is measured at multiple locations in the radial direction after the rough grinding step 1002 and before the finish grinding step 1006 described below is performed, and the thickness distribution of the second plate-like object 120 is measured. In the post-rough grinding measurement step 1003, the control unit 70 first moves the holding table 20, which holds by suction the workpiece 100 whose second plate-like object 120 side has been roughly ground in the rough grinding step 1002, from the rough grinding position 202 to the finish grinding position 203 by rotating the turntable 25. In the post-rough grinding measurement step 1003, the control unit 70 then uses the non-contact measurement unit 60 to irradiate light onto the upper surface and the lower surface of the second plate-like object 120, and measures the thickness of the second plate-like object 120 at multiple locations in the radial direction (three locations in the example of FIG. 3) by interference of light reflected from the upper and lower surfaces, thereby measuring the radial thickness distribution of the second plate-like object 120. By performing the post-rough grinding measurement step 1003 in this manner, the control unit 70 obtains the radial thickness distribution 201 of the second plate-like object 120 after the rough grinding step 1002 of the first workpiece 100 is performed, as shown in FIG. 5.

The finish grinding step 1006 is a step in which the second plate-like object 120 is finish-ground with the finish grinding wheel 43. Both the semi-finish grinding step and the main finish grinding step are similar steps in which the second plate-like object 120 is finish-ground with the finish grinding wheel 43. In the finish grinding step 1006, the control unit 70 rotates the spindle 41 to rotate the finish grinding wheel 43, as shown in FIG. 2, while pressing the second plate-like object 120 side of the workpiece 100 held on the holding table 20 positioned at the finish grinding position 203 and inclined by the rotation axis adjustment unit 29 at a predetermined inclination angle (in the example shown in FIG. 2, the inclination angle θ2) with respect to the horizontal plane with the finish grinding wheel 43 by the finish grinding feed unit 44 along the grinding feed direction, thereby finishing grinding the second plate-like object 120 with the finish grinding wheel 43.

The post-finish grinding measurement step 1007 is a step in which, after the finish grinding step 1006 is performed, the thickness of the second plate-like object 120 is measured at multiple locations in the radial direction to measure the thickness distribution of the second plate-like object 120. The post-semi-finish grinding measurement step and the post-finish grinding measurement step are both steps in which the thickness distribution of the second plate-like object 120 is similarly measured. In the post-finish grinding measurement step 1007, the control unit 70 measures the radial thickness distribution of the second plate-like object 120 using the non-contact measurement unit 60 in a manner similar to that in the post-coarse grinding measurement step 1003.

In the semi-finish grinding step, as shown in FIG. 5, the thickness of the second plate-like object 120 is reduced by about half the planned final finish grinding thickness, and in this embodiment, the second plate-like object 120 is ground, for example, by about 15 to 25 μm. Note that the amount of grinding in the semi-finish grinding step is not limited to about half the planned grinding thickness, and it is sufficient that the amount of grinding remaining is sufficient to eliminate the variation in the radial thickness distribution of the second plate-like object 120 in the main finish grinding step after the semi-finish measurement step, and may be adjusted appropriately. In the semi-finish grinding measurement step, as shown in FIG. 5, the radial thickness distribution 202 of the second plate-like object 120 after the semi-finish grinding step is obtained.

The inclination adjustment step 1005 in the grinding process of the first workpiece 100 is a step in which the control unit 70 relatively adjusts the inclination between the holding surface 21 and the finish grinding surface 45 of the finish grinding wheel 43 based on the radial thickness distribution 202 of the second plate-like object 120 after the semi-finish grinding step obtained in the semi-finish grinding measurement step so that the radial thickness distribution of the second plate-like object 120 after the final grinding step to be performed later becomes uniform, that is, in a direction that cancels (eliminates) this thickness distribution 202. In this inclination adjustment step 1005, first, the control unit 70 calculates the inclination angle θ3 of the thickness distribution 202 shown in FIG. 5 based on this thickness distribution 202. In this embodiment, the control unit 70 treats the inclination angle θ3 as a positive value when the thickness distribution 202 is convex at the center, and as a negative value when the thickness distribution 202 is concave at the center. In this tilt adjustment step 1005, the control unit 70 then adjusts the tilt angle θ2 of the entire holding table 20 to the tilt angle (θ2-θ3) using the rotation axis adjustment unit 29, as shown in FIG. 5, thereby canceling the tilt angle θ3 of the thickness distribution 202.

This finish grinding step is performed after the inclination between the holding surface 21 and the finish grinding surface 45 of the finish grinding wheel 43 is relatively adjusted in the inclination adjustment step 1005. Therefore, in this finish grinding step, the radial thickness distribution of the second plate-like object 120 becomes uniform, as shown in FIG. 5. In this finish grinding step, in this embodiment, the second plate-like object 120 is thinned to a thickness of, for example, about 50 μm. In this post-finish grinding measurement step, the radial thickness distribution 203 of the second plate-like object 120 after this finish grinding step is obtained, as shown in FIG. 5.

Next, the grinding process of the second and subsequent workpieces 100 will be described with reference to Figures 4 and 6. As shown in Figures 4 and 6, the grinding process of the second and subsequent workpieces 100 in the grinding method of the workpiece according to the embodiment includes a holding step 1001, a rough grinding step 1002, a post-rough grinding measurement step 1003, an inclination adjustment step 1005, a finish grinding step 1006, and a post-finish grinding measurement step 1007.

The grinding process for the second and subsequent workpieces 100 is the same as the grinding process for the first workpiece 100, except that the semi-finish grinding step and the post-semi-finish grinding measurement step are omitted and the inclination adjustment step 1005 is changed. Since the processing in the other steps is the same, only the inclination adjustment step 1005 will be described and the processing in the other steps will be omitted. As shown in FIG. 6, the inclination adjustment step 1005 in the grinding process for the second and subsequent workpieces 100 includes an individual difference calculation step 1005-1 and an adjustment step 1005-2.

The individual difference calculation step 1005-1 is a step in which the control unit 70 calculates the relative difference 111 in the thickness distribution of the first plate-like object 110 between the ground workpiece 100 and the workpiece 100 being ground, which is the individual difference between the ground workpiece 100 and the workpiece 100 being ground, based on the rough distribution of the ground workpiece 100 and the rough distribution of the workpiece 100 being ground, as shown in FIG. 6. Here, the ground workpiece 100 refers to the workpiece 100 that has undergone the finish grinding step 1006 (the first workpiece 100 in the example shown in FIG. 6), and the workpiece 100 being ground refers to the workpiece 100 that has undergone the rough grinding step 1002 and will undergo the finish grinding step 1006 (the second workpiece 100 in the example shown in FIG. 6). Furthermore, the rough distribution refers to the thickness distribution of the second plate-like object 120 measured in the post-rough grinding measurement step 1003 (in the example shown in FIG. 6, the first thickness distribution 201 for the ground workpiece 100, and the thickness distribution 204 for the workpiece 100 being ground).

In the individual difference calculation step 1005-1, specifically, the control unit 70 calculates the relative difference 111 in the thickness distribution of the first plate-like object 110 by subtracting the rough distribution, which is the radial thickness distribution of the first plate-like object 110 measured in the post-rough grinding measurement step 1003 of the workpiece 100 being ground, from the rough distribution, which is the radial thickness distribution of the first plate-like object 110 measured in the post-rough grinding measurement step 1003 of the ground workpiece 100. In the individual difference calculation step 1005-1, the control unit 70 then calculates the inclination angle θ6 of the relative difference 111 in the thickness distribution of the first plate-like object 110, as shown in FIG. In this embodiment, the inclination angle θ6 calculated in the individual difference calculation step 1005-1 is simply the inclination angle θ4 of the rough distribution of the ground workpiece 100 minus the inclination angle θ5 of the rough distribution of the workpiece 100 being ground, since the inclination angle θ2 of the holding table 20 in the rough grinding step 1002 of the ground workpiece 100 is the same as the inclination angle θ2 of the holding table 20 in the rough grinding step 1002 of the workpiece 100 being ground. Note that the positive and negative of the inclination angles θ4, θ5, and θ6 are defined in the same way as the positive and negative of the inclination angle θ3 described above. If the inclination angle θ2 of the holding table 20 in the rough grinding step 1002 is changed for each workpiece 100, the inclination angle θ6 calculated in the individual difference calculation step 1005-1 is calculated taking into account the change in the inclination angle θ2.

In the adjustment step 1005-2, after the individual difference calculation step 1005-1 is performed, the control unit 70 adjusts the inclination of the holding surface 21 and the finish grinding surface 45 of the finish grinding wheel 43 relatively in such a way that the radial thickness distribution of the second plate-like object 120 after the finish grinding step 1006 is uniform, that is, in the direction of canceling (eliminating) the inclination angle θ5 of the rough distribution of the workpiece 100 being ground, based on the difference 111 calculated in the individual difference calculation step 1005-1 and taking into account the feedback of the finish distribution of the ground workpiece 100, as shown in FIG. 6. Here, the finish distribution refers to the thickness distribution of the second plate-like object 120 measured in the measurement step after finish grinding 1007 (in the example shown in FIG. 6, the thickness distribution 203 of the first piece of the ground workpiece 100).

In adjustment step 1005-2, first, the control unit 70 calculates the inclination angle θ7 of the finish distribution (thickness distribution 203 in the example shown in FIG. 6) of the ground workpiece 100, as shown in FIG. 6. In adjustment step 1005-2, the inclination of the holding surface 21 and the finish grinding surface 45 of the finish grinding wheel 43 is then relatively adjusted in a direction that adds the inclination angle θ6 of the difference 111 and in a direction that cancels (eliminates) the inclination angle θ7 of the thickness distribution 203. In adjustment step 1005-2, as shown in FIG. 6, the control unit 70 adjusts the tilt angle of the entire holding table 20 by the rotation axis adjustment unit 29 from the tilt angle (θ2-θ3) during finish grinding step 1006 of the workpiece 100 that has been finished grinding step 1006 to a tilt angle (θ2-θ3+θ6-θ7), thereby feeding back the tilt angle θ4 of the rough distribution of the ground workpiece 100 and the tilt angle θ7 of the finish distribution, and canceling out the tilt angle θ5 of the rough distribution of the workpiece 100 being ground.

Here, the ground workpiece 100 in the individual difference calculation step 1005-1 and the adjustment step 1005-2 may always be the first workpiece 100, or may be the workpiece 100 that was ground immediately before the workpiece 100 being ground.

The inclination adjustment step 1005 in the grinding process of the first workpiece 100 is essentially the same as the inclination adjustment step 1005 in the grinding process of the second or subsequent workpieces 100, since the individual difference calculation step 1005-1 for calculating the individual difference between the first workpiece 100 and the first workpiece 100 is omitted, and instead of canceling the inclination angle of the finishing distribution of the ground workpiece 100, adjustment step 1005-2 is performed to cancel the thickness distribution 202 of the workpiece 100 after the semi-finish grinding step.

As described above, in the grinding method for the workpiece according to the embodiment, the control unit 70 stops grinding of the first workpiece 100, measures the thickness distribution of the workpiece, adjusts the inclination between the holding surface and the grinding wheel, and then performs a regrind to resume grinding. For the second and subsequent workpieces 100, the previously ground workpiece 100 is used as a reference to subtract the coarse distribution during grinding from the coarse distribution after grinding to calculate the relative difference 111 in the thickness distribution of the first plate-like object 110, and the inclination between the holding surface 21 and the finish grinding surface 45 of the finish grinding wheel 43 is relatively adjusted in the direction of adding the inclination angle θ6 of this difference 111, so that the second plate-like object 120 can be ground to a uniform thickness in a finish grinding process that is performed subsequently. Therefore, the method for grinding a workpiece according to the embodiment has the effect of being able to grind a second plate-like object 120, which is attached to a first plate-like object 110 whose thickness cannot be directly measured, to a uniform thickness without reducing the processing efficiency of the second and subsequent workpieces 100.

If the first workpiece 100 can be sacrificed for thickness adjustment, regrind may not be performed on the first workpiece 100. In that case, for the second workpiece 100, the inclination of the holding surface 21 may be calculated from the difference 111 between the radial thickness distribution of the first plate-like object 110 measured in the measurement step 1003 after rough grinding of the second workpiece 100 and the radial thickness distribution of the first plate-like object 110 measured in the measurement step 1003 after rough grinding performed on the first workpiece 100, and the thickness distribution of the second plate-like object 120 measured in the measurement step 1007 after finish grinding of the first workpiece 100, so that the radial thickness distribution of the second plate-like object 120 becomes flat after the finish grinding step 1006, and the inclination adjustment step 1005 may be performed.

In addition, in the grinding method of the workpiece according to the embodiment, the control unit 70 feeds back the inclination angle θ7 of the finish distribution of the previously ground workpiece 100, and adjusts the relative inclination between the holding surface 21 and the finish grinding surface 45 of the finish grinding wheel 43 in a direction that cancels the inclination angle θ7. Therefore, the grinding method of the workpiece according to the embodiment has the effect of being able to grind the second plate-like object 120 to a more uniform thickness by taking into account physical factors such as the condition of the processing device 1, the rough grinding wheel 33, and the finish grinding wheel 43, which change during the grinding process of the multiple workpieces 100.

The present invention is not limited to the above embodiment. In other words, the present invention can be implemented in various modifications without departing from the gist of the invention.

REFERENCE SIGNS LIST 1 Processing device 20 Holding table 21 Holding surface 30 Rough grinding unit 33 Rough grinding wheel 40 Finish grinding unit 43 Finish grinding wheel 45 Finish grinding surface 50 Contact measurement unit 60 Non-contact measurement unit 100 Workpiece 110 First plate-like object 120 Second plate-like object 130 Boundary surface 201, 202, 203, 204, 205 Thickness distribution

Claims (2)

A method for grinding a workpiece, in which a first plate-like object is stacked on a second plate-like object, and the second plate-like object is ground to a finish thickness, comprising the steps of:
a method for sequentially grinding the second plate-like object in the plurality of workpieces one by one so that the thickness of the second plate-like object in the workpieces is uniform;
The method for grinding a workpiece comprises the steps of:
a holding step of holding the first plate-like object on a holding surface of a holding table;
a rough grinding step of grinding the second plate-like object with a rough grinding wheel;
a post-rough-grinding measurement step of measuring a thickness of the second plate-like object at a plurality of points in a radial direction after the rough grinding step is performed, and measuring a thickness distribution of the second plate-like object;
a finish grinding step of grinding the second plate-shaped object, which has been subjected to the rough grinding step and the post-rough grinding measurement step, with a finish grinding wheel;
a post-finish grinding measurement step of measuring a thickness of the second plate-like object at a plurality of points in a radial direction after the finish grinding step is performed, and measuring a thickness distribution of the second plate-like object;
and a tilt adjustment step of relatively adjusting the tilt between the holding surface and the grinding surface of the finish grinding wheel so that the thickness distribution of the second plate-like object becomes uniform,
When grinding a first workpiece, the finish grinding step and the post-finish grinding measurement step are performed twice each, a first finish grinding step is performed such that the grinding amount does not reach the final planned finish grinding thickness, a first post-finish grinding measurement step is performed after the first finish grinding step is performed, a tilt adjustment step is performed to adjust the tilt in accordance with the thickness distribution of the second plate-like object measured in the first post-finish grinding measurement step, a second finish grinding step is performed after the tilt adjustment step, and a second post-finish grinding measurement step is performed after the second finish grinding step is performed,
When grinding the second or subsequent workpiece, the tilt adjustment step calculates a difference between the thickness distribution of the second plate-like object measured in a measurement step after rough grinding of the workpiece that has already been finished grinding and the thickness distribution of the second plate-like object measured in a measurement step after rough grinding of the workpiece that will be subjected to the finish grinding step, adjusts the tilt of the workpiece that has already been finished grinding during the finish grinding step to a new tilt in accordance with the difference, and adjusts the tilt so that the upcoming finish grinding step is performed with the new tilt. The method for grinding a workpiece as described in claim 1, characterized in that, when grinding a second or subsequent workpiece, the inclination adjustment step adjusts the inclination so that the thickness of the second plate-like object becomes more uniform by taking into account the thickness distribution of the second plate-like object measured in a measurement step after finish grinding of the workpiece that has been subjected to the finish grinding step.

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