Self-grind method

Abstract

To propose a novel art which can control conditions of self-grinding in a constant manner.SOLUTION: In a self-grinding method, a holding surface of a holding table is processed in a processing device. The self-grinding method includes, at least, an exposure step in which the holding surface of the holding table is exposed, a self-grinding step in which the holding surface is processed with the processing tool, and a self-grinding time load centroid calculation step in which a self-grinding time load centroid which is a load centroid of a processing unit during self-grinding is calculated from processing loads measured by a plurality of load sensors during the self-grinding step.SELECTED DRAWING: Figure 9

Description

[Technical Field]

[0001] The present invention relates to a self-grinding method in which a holding surface of a holding table that holds a workpiece is ground with a grinding wheel. [Background technology]

[0002] Silicon wafers, which have multiple IC, LSI, and other devices formed on their surface, have their backsides ground to a specified thickness, and then are separated into individual devices using a cutting machine for use in electrical equipment such as mobile phones and personal computers.

[0003] The process of grinding the back surface of the wafer uses a known grinding device, and a grinding wheel is attached to the spindle of the grinding device to perform rough grinding and finish grinding to a predetermined thickness (see, for example, Patent Document 1).

[0004] In recent years, due to the miniaturization and high integration of semiconductor devices, there has been a demand for thinner wafers and higher precision in the finished thickness of wafers. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-288881 [Patent Document 2] Japanese Patent Application Publication No. 2020-199597 Summary of the Invention [Problem to be solved by the invention]

[0006] The above-mentioned grinding process is carried out by bringing a grinding wheel attached to the tip of the spindle of the grinding device into contact with the back surface of the wafer, which is the workpiece, and feeding the wheel downward while applying a predetermined processing load, thereby thinning the wafer to a predetermined thickness.

[0007] Here, even if grinding is performed by applying an appropriate processing load to the workpiece, if the center of gravity of the load at that time is shifted from the desired position, variations will occur in the thickness accuracy of the workpiece.

[0008] On the other hand, in this type of grinding device, as described in Patent Document 2, for example, self-grinding is performed in which the holding surface of the holding table that holds the workpiece is periodically ground with a grinding wheel to form the holding surface into an appropriate shape.

[0009] In the past, the center of gravity of the load during self-grinding was not known, so it was not possible to maintain a consistent self-grinding state.

[0010] In view of the above problems, the present invention focuses on the position of the processing load acting on the grinding wheel during self-grinding, and proposes a new technology that makes it possible to consistently manage the self-grinding conditions. [Means for solving the problem]

[0011] The problem to be solved by the present invention is as described above, and the means for solving this problem will now be described.

[0012] According to one aspect of the present invention, a self-grinding method for machining the holding surface of a holding table in a machining apparatus comprising at least a holding table having a holding surface for holding a workpiece, a spindle, a machining unit for machining the workpiece held on the holding surface of the holding table by a machining tool attached to the tip of the spindle, a plurality of load sensors disposed in the machining unit for measuring the machining load applied to the holding surface depending on the machining feed amount of the machining tool, and a tilt adjustment unit for adjusting the relative tilt between the machining unit and the holding table, the self-grinding method including at least an exposure step for exposing the holding surface of the holding table, a self-grinding step for machining the holding surface with the machining tool, and a self-grinding load center of gravity calculation step for calculating the load center of gravity of the machining unit during self-grinding, which is the load center of gravity of the machining unit during self-grinding, from the machining load measured by the plurality of load sensors during the self-grinding step.

[0013] Furthermore, according to one aspect of the present invention, the method includes at least a center of gravity position correction step of correcting the self-grinding load center of gravity calculated in the self-grinding load center of gravity calculation step so that it coincides with a target load center of gravity, which is a specified load center of gravity.

[0014] According to another aspect of the present invention, the tilt adjustment unit adjusts the tilt of the processing unit.

[0015] According to another aspect of the present invention, the tilt adjustment unit adjusts the tilt of the holding table. [Effects of the Invention]

[0016] The present invention provides the following effects. In other words, according to one aspect of the present invention, during self-grinding, the position of the load center of gravity during self-grinding is corrected to the target load center of gravity, making it possible to maintain a constant state of self-grinding, and enabling stable self-grinding under specified conditions. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a diagram showing a grinding apparatus as an example of a processing apparatus in which the present invention can be implemented; [Figure 2] 3A and 3B are diagrams illustrating the configuration of a holding table, etc. FIG. [Figure 3] 3A and 3B are diagrams illustrating the configuration of a rough grinding means, etc. FIG. [Figure 4] 10A and 10B are diagrams illustrating the position of the center of gravity of the load during processing, etc. FIG. [Figure 5] 1 is a flowchart showing steps constituting a processing method. [Figure 6] FIG. 10 is a diagram illustrating an example of processed data. [Figure 7] FIG. 10 is a diagram illustrating a dressing method. [Figure 8] 1 is a flowchart showing steps constituting a dressing method. [Figure 9] FIG. 10 is a diagram illustrating a self-grinding method. [Figure 10] 1 is a flowchart showing steps constituting a self-grinding method. DETAILED DESCRIPTION OF THE INVENTION

[0018] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a diagram showing a grinding apparatus 1 which is an example of a processing apparatus in which the present invention can be implemented.

[0019] The grinding apparatus 1 shown in FIG. 1 is equipped with rough grinding means 30 and finish grinding means 31, and is an apparatus for grinding a wafer W as a workpiece held on a holding table 5 disposed below each of the means.

[0020] The grinding apparatus 1 is configured, for example, by connecting a first apparatus base 10 and a second apparatus base 11 to the rear (+Y direction side) of the first apparatus base 10. The area above the first apparatus base 10 is a loading / unloading area A where wafers W are loaded and unloaded. The area above the second apparatus base 11 is a grinding area B where the wafers W are ground by rough grinding means 30 and finish grinding means 31.

[0021] The wafer W is a circular semiconductor wafer made of, for example, a silicon base material, and a plurality of devices are formed on the front surface Wa of the wafer W, which faces downward in FIG. 1, and is protected by a protective tape T. The back surface Wb of the wafer W is the processing surface that is subjected to the grinding process. Note that the wafer W may be made of gallium arsenide, sapphire, gallium nitride, ceramics, resin, silicon carbide, or the like, in addition to silicon, or may be a package substrate, or the like.

[0022] A first cassette loading section 150 and a second cassette loading section 151 are provided on the front side (-Y direction side) of the first device base 10, and a first cassette 150a that contains unprocessed wafers W is loaded on the first cassette loading section 150, and a second cassette 151a that contains processed wafers W is loaded on the second cassette loading section 151.

[0023] A robot 155 is disposed behind the opening of the first cassette 150a for carrying out unprocessed wafers W from the first cassette 150a and carrying processed wafers W into the second cassette 151a. A temporary placement area 152 is provided adjacent to the robot 155, and an alignment means 153 is disposed in the temporary placement area 152. The alignment means 153 aligns (centers) the wafers W carried out from the first cassette 150a and placed in the temporary placement area 152 at a predetermined position using alignment pins with a decreasing diameter.

[0024] A loading arm 154a that rotates while holding a wafer W is disposed adjacent to the alignment means 153. The loading arm 154a holds the wafer W that has been aligned by the alignment means 153, and transports it to one of the holding tables 5 disposed in the grinding processing area B. An unloading arm 154b that rotates while holding a processed wafer W is disposed next to the loading arm 154a. A cleaning means 156 that cleans the processed wafer W transported by the unloading arm 154b is disposed in a position close to the unloading arm 154b. The wafer W cleaned by the cleaning means 156 is carried into the second cassette 151a by a robot 155.

[0025] A first column 12 is erected at the rear (+Y direction side) of the second device base 11, and a rough grinding feed means 20 is arranged in front of the first column 12, and the rough grinding feed means 20 moves the rough grinding means 30 back and forth in the Z axis direction.

[0026] The rough grinding means 30 includes a grinding wheel 304 that is rotated by a spindle motor 302, and below the grinding wheel 304, a plurality of grinding stones containing relatively large abrasive grains are arranged in the circumferential direction.

[0027] Further, at the rear of the second device base 11, a second column 13 is erected alongside the first column 12 in the X-axis direction, and a finish grinding feed means 21 is disposed in front of the second column 13. The finish grinding feed means 21 causes the finish grinding means 31 to move back and forth in the Z-axis direction.

[0028] The finish grinding means 31 includes a grinding wheel 314 that is rotated by a spindle motor 312, and below the grinding wheel 314, a plurality of finish grinding stones containing relatively small abrasive grains are arranged in the circumferential direction.

[0029] 1, a turntable 6 is disposed on the second device base 11, and three holding tables 5 are disposed on the upper surface of the turntable 6 at equal intervals in the circumferential direction. A rotation means 66 for rotating the turntable 6 is disposed below the turntable 6, and the rotation means 66 can rotate the turntable 6 about its axis in the Z-axis direction. The rotation of the turntable 6 causes the three holding tables 5 to revolve, and the holding tables 5 can be sequentially positioned from near the temporary placement area 152, below the rough grinding means 30, and below the finish grinding means 31.

[0030] The holding table 5 has, for example, a circular outer shape and includes an adsorption portion 510 made of a porous material or the like that adsorbs the wafer W, and a frame 511 that supports the adsorption portion 510. The adsorption portion 510 is connected to a suction source (not shown) such as a vacuum generator, and the suction force generated by the suction source is transmitted to a holding surface 510a, which is the exposed surface of the adsorption portion 510, causing the holding table 5 to adsorb and hold the wafer W on the holding surface 510a. The holding table 5 is fixed on, for example, a table base 55 that is circular in plan view, and is rotatable on a turntable 6 about an axis in the Z-axis direction.

[0031] A support base 60 is disposed adjacent to the holding table 5 located below the rough grinding means 30 or the finish grinding means 31. In this embodiment, the support base 60 is disposed in the center of the turntable 6, and is provided with measuring units 38A, 38B (commonly known as height gauges) for measuring the height position of the holding surface of the holding table 5.

[0032] The grinding device 1 is equipped with a control means 9 that is composed of a CPU, a storage unit 90 such as a memory, and the like. The control means 9 is electrically connected to, for example, the rough grinding feed means 20, the finish grinding feed means 21, the rough grinding means 30, and the rotation means 66, and under the control of the control means 9, the rough grinding feed operation of the rough grinding means 30 by the rough grinding feed means 20, the finish grinding feed operation of the finish grinding means 31 by the finish grinding feed means 21, the rotation operation of the rough grinding wheel 304b in the rough grinding means 30, and the rotation operation of the turntable 6 by the rotation means 66 are controlled.

[0033] As will be described in detail later, the control means 9 has a storage unit 90 for storing the position of the target load center of gravity, and a center of gravity calculation unit 91 for calculating the position of the load center of gravity during machining.

[0034] The grinding device 1 is provided with a touch panel 70 for inputting processing conditions, displaying the processing state, etc. The input contents on the touch panel 70 are stored in a storage unit 90 and are referred to as appropriate.

[0035] 2 shows the configuration of the rough grinding means 30. The finish grinding means 31 has a similar configuration, so its description will be omitted. The spindle 300 of the rough grinding means 30 rotates around a spindle rotation axis 300a in the vertical direction (Z-axis direction), and a grinding wheel 304 is fixed to a wheel mount 303 provided at the bottom end of the spindle 300.

[0036] The holding table 5 includes an adsorption portion 510 made of a disc-shaped porous member or the like that adsorbs the wafer W, and a frame 511 that supports the adsorption portion 510. A motor 512 that rotates the holding table 5 about a table rotation shaft 513 is provided below the holding table 5. The holding table 5, motor 512, and table rotation shaft 513 constitute a holding means 51. The adsorption portion 510 is connected to a suction source (not shown), and a suction force generated by the suction source is transmitted to a holding surface 510a, which is the exposed surface of the adsorption portion 510, thereby adsorbing and holding the wafer W on the holding surface 510a.

[0037] The holding table 5 is supported by a tilt adjustment unit 56 that adjusts the tilt of a table rotation axis 513 that passes through the center of the holding surface 510a. The tilt adjustment unit 56 has at least three support parts, at least two of which are movable support parts 52 and 53, and the remaining part is a fixed support part 54. In this embodiment, the tilt adjustment unit 56 has two movable support parts 52 and 53 and one fixed support part 54, which are arranged at a regular interval in the circumferential direction on the bottom side of the frame body 511. Note that a configuration in which three movable support parts and no fixed support part are arranged may also be used, with all parts being movable support parts. Furthermore, a total of four or more movable support parts and fixed support parts may also be arranged.

[0038] 2, the movable support part 52 is composed of a motor 520 disposed on a base 55 inside the grinding device 1, a rotatable adjustment shaft 521 connected to the motor 520, a support part 522 that rotatably supports the adjustment shaft 521, and a housing part 523 that protrudes downward from the bottom of the frame body 511 and houses the adjustment shaft 521. The motor 520 is connected to the control means 9 and operates under the control of the control means 9.

[0039] Male thread 521a is formed at the tip of adjustment shaft 521, and female thread 523a that screws onto male thread 521a is formed on the inner surface of housing portion 523. Furthermore, origin sensor 523b that detects the position of the tip of adjustment shaft 521 is disposed on the inner surface of housing portion 523. Control means 9 recognizes the position of the tip of adjustment shaft 521 in a relative relationship with origin sensor 523b.

[0040] On the other hand, the fixed support portion 54 is provided with a fixed shaft 541 whose lower end is fixed onto the base 55 and whose upper end is fixed to the lower part of the frame body 511 .

[0041] In the movable support part 52, the motor 520 rotates the adjustment shaft 521 under the control of the control means 9, whereby the male screw 521a advances and retreats relative to the female screw 523a, raising and lowering the accommodation part 523, and changing the relative height of the frame body 511 with respect to the base 55. The same is true for the movable support part 53. On the other hand, in the fixed support part 54, the height position of the frame body 511 with respect to the base 55 does not change. Therefore, the height of the adjustment shaft 521 with respect to the accommodation part 523 rises and falls relative to the accommodation part 523, or the height of the adjustment shaft 531 with respect to the accommodation part 533 rises and falls relative to the accommodation part 533, changing the inclination of the table rotation axis 513 with respect to the spindle rotation axis 300a.

[0042] The holding surface 510a is a conical surface, and is adjusted by the tilt adjustment unit 56 so that a partial radial area of ​​the conical surface is parallel to the lower surface (grinding surface) of the grinding wheel 304b.

[0043] 3 shows the configuration of the rough grinding means 30. The finish grinding means 31 has the same configuration, so a description thereof will be omitted.

[0044] The holding table 5, positioned below the rough grinding means 30, holds a wafer W as a workpiece. The holding table 5 has a disk shape with a holding surface 510a made of porous ceramic or the like. The holding table 5 is connected to a vacuum suction source (not shown) via a vacuum suction path (not shown). The front surface of the wafer W is placed on the holding surface 510a of the holding table 5 via a protective tape T. The holding table 5 holds the wafer W placed on the holding surface 510a by suction via the protective tape T. The holding table 5 rotates the suction-held wafer W around the Z axis.

[0045] The rough grinding means 30 grinds the exposed surface of the wafer W held on the holding table 5. The rough grinding means 30 includes a spindle housing 32a, a spindle 300 rotatably supported by the spindle housing 32a, and a grinding wheel 304 attached to the lower end of the spindle 300. The grinding wheel 304 can rotate around the central axis of the rough grinding means 30 as the spindle 300 rotates using a rotary drive mechanism. A plurality of grinding stones 304b are arranged at intervals in the circumferential direction below the ring-shaped grinding wheel 304, and the grinding stones 304b are arranged opposite the holding surface 510a of the holding table 5. While the grinding wheel 304 is rotating, the back surface Wb of the wafer W held on the holding surface 510a of the holding table 5 is pressed with a predetermined processing load and fed for processing, whereby the back surface Wb of the wafer W is ground and thinned by the grinding stones 304b.

[0046] The spindle housing 32a is provided with an annular ring 33, a flange 34 extending along the circumferential direction of the spindle housing 32a, and a cover 35, which are coaxially arranged.

[0047] The ring 33 is disposed below the cover 35. The ring 33 receives a grinding load from the spindle 300. A plurality of female threads 33a are formed on the inner peripheral surface of the ring 33, penetrating the ring 33 in the thickness direction and engaging with the male threads 36b of the load sensor 36. The female threads 33a are formed at equal intervals around the circumference of the ring 33, at the same distance from the rotation center, i.e., on the same circumference centered on the rotation center. In this embodiment, three female threads 33a are formed at 120° intervals around the circumference of the ring 33. A plurality of female threads 33b are formed on the inner peripheral surface of the ring 33, penetrating the ring 33 in the thickness direction and engaging with the male threads 45a of the inclination adjustment unit 45. The female threads 33b are formed on the same circumference and engaging with the male threads 45a of the inclination adjustment unit 45 at equal intervals around the circumference of the ring 33. In this embodiment, three female threads 33b are formed at 120° intervals around the circumference of the ring 33.

[0048] The flange 34 is formed coaxially and integrally with the spindle housing 32a. The flange 34 has a plurality of female threads 34a formed on its inner circumferential surface, which penetrate the flange 34 in the thickness direction and into which the male threads 45a of the inclination adjustment unit 45 are threadedly engaged. The female threads 34a are formed on the same circumference at equal intervals in the circumferential direction of the flange 34. In this embodiment, three female threads 34a are formed at 120° intervals in the circumferential direction of the flange 34. The female threads 34a are formed at positions that overlap and communicate with the female threads 33b of the ring 33 when viewed in the axial direction when the ring 33 is fixed to the spindle housing 32a.

[0049] The cover 35 is disposed to cover the outer periphery of the spindle housing 32a. The cover 35 is attached to a Z-axis plate 20a that is raised and lowered by the rough grinding feed means 20 (FIG. 1). The cover 35 has a plurality of recesses 35a formed on its underside, into which the male threads 36b of the load sensor 36 can be inserted. The recesses 35a are formed on the same circumference at equal intervals in the circumferential direction of the cover 35. In this embodiment, three recesses 35a are formed at 120° intervals in the circumferential direction of the cover 35. The recesses 35a are formed at positions that overlap and communicate with the female threads 33a of the ring 33, as viewed in the axial direction, when the ring 33 is fixed to the spindle housing 32a. The ring 33 and the cover 35 are fastened with screws at a plurality of positions that are equally spaced in the circumferential direction (not shown).

[0050] The rough grinding feed means 20 (Figure 1) adjusts the distance between the holding table 5 and the rough grinding means 30, thereby adjusting the force (processing load (grinding load)) with which the grinding wheel 304 presses the wafer held on the holding surface 510a of the holding table 5.

[0051] The load sensor 36 detects the processing load applied to the wafer W held on the holding surface 510a of the holding table 5 due to the grinding feed of the grinding wheel 304. The load sensors 36 are arranged at equal intervals in the circumferential direction between the ring 33 and the cover 35 of the rough grinding means 30. In this embodiment, three load sensors 36 are arranged at intervals of 120° in the circumferential direction.

[0052] The load sensor 36 is a sensor capable of detecting a processing load, including, for example, a strain sensor, and includes a ring-shaped sensor 36a and a male screw 36b that penetrates the sensor 36a. The sensor 36a outputs the detected processing load to the control means 9. The male screw 36b secures the sensor 36a. The male screw 36b is inserted into the female screw 33a of the ring 33 and into the recess 35a of the cover 35. When the male screw 36b is tightened, the sensor 36a is sandwiched between the ring 33 and the cover 35 of the rough grinding means 30. In other words, the sensor 36a is positioned between the ring 33 and the cover 35 of the rough grinding means 30 and pressed along the axial direction of the rough grinding means 30. As a result, the processing load is transmitted to the sensor 36a via the grinding wheel 304, the spindle 300, the spindle housing 32a, the flange 34, and the ring 33.

[0053] As shown in FIG. 4, when viewed in the Z-axis direction, the load sensors 36 are arranged at positions P1 (x1, y1), P2 (x2, y2), and P3 (x3, y3), and detect the processing loads F1, F2, and F3 at the respective positions.

[0054] 3, in this embodiment, the inclination adjustment unit 45 is configured to adjust the angle of the grinding wheel 304. The inclination adjustment units 45 are arranged at equal intervals in the circumferential direction between the ring 33 and the flange 34 of the rough grinding means 30. In this embodiment, three inclination adjustment units 45 are arranged at 120° intervals in the circumferential direction. The inclination adjustment units 45 adjust the angle of the grinding wheel 304 by moving the ring 33 and the flange 34 of the rough grinding means 30 closer to or farther apart from each other.

[0055] The inclination adjustment unit 45 includes a male screw 45a and a nut 47 having a female screw formed on its inner circumferential surface to which the male screw 45a is threaded. The male screw 45a is inserted into the female screw 33b of the ring 33 and threadably engages with the female screw 34a of the flange 34. The male screw 45a is inserted into a pair of nuts 47 disposed on either side of the ring 33. When the male screw 45a of the inclination adjustment unit 45 configured in this manner is loosened, the ring 33 and the flange 34 move apart. When the male screw 45a of the inclination adjustment unit 45 is tightened, the ring 33 and the flange 34 move closer to each other. In this manner, the inclination adjustment unit 45 adjusts the angle of the grinding wheel 304 of the rough grinding means 30 by tightening and loosening each male screw 45a. The inclination adjustment unit 45 is configured to include a motor (not shown) that rotates the male screw 45a.

[0056] 3 and 4, the center of gravity calculation unit 91 of the control means 9 calculates the position G1(xG1, yG1) of the center of gravity of the load during machining in real time, as will be described in detail later. Here, the position G1(xG1, yG1) is calculated from the machining loads F1, F2, and F3 placed at positions P1(x1, y1), P2(x2, y2), and P3(x3, y3), and specifically, can be calculated using the following formula 1.

[0057]

number

[0058] 3 and 4, when the position G1 (xG1, yG1) of the center of gravity of the load during processing does not correspond to the position G2 (xG2, yG2) of the target center of gravity of the load, the control means 9 controls the tilt adjustment unit 45 to position the center of gravity G1 at position G2, as will be described in detail later. More specifically, the control means 9 adjusts the angle of the grinding wheel 304 of the rough grinding means 30 by tightening or loosening the male screws 45a of the tilt adjustment unit 45 so that the position G1 of the center of gravity of the load during processing corresponds to the position G2 of the target center of gravity of the load. The position G2 of the target center of gravity of the load is defined by a method that will be described in detail later, and is the position of the center of gravity of the load that achieves good thickness accuracy (TTV: Total Thickness Variation).

[0059] As described above, as shown in FIGS. 1 to 3, a holding table 5 having a holding surface 510a for holding a wafer W, which is a workpiece; a spindle 300; and a rough grinding means 30 as a processing unit for processing a wafer W held on a holding surface 510a of a holding table 5 by a grinding wheel 304 as a processing tool attached to the tip of the spindle 300; a plurality of load sensors 36 disposed in the rough grinding means 30 and measuring processing loads F1, F2, F3 (FIG. 4) applied to the holding surface 510a according to the processing feed amount of the grinding wheel 304; an inclination adjustment unit 45 for adjusting the relative inclination between the rough grinding means 30 and the holding table 5; The grinding device 1 is configured as a processing device equipped with the above.

[0060] Next, a method for processing a workpiece using the processing device having the above configuration will be described. Fig. 5 is a flowchart showing each step of the processing method.

[0061] <Center of gravity regulation step> The center of gravity determination step is a step for determining the target load center of gravity, which will be described later, and is performed in advance in preparation for processing. In this embodiment, the center of gravity determination step includes the following determination processing step, thickness measurement step, processing data acquisition step, and determination step. Note that the present invention is not limited to the following embodiment, and the target load center of gravity for achieving good thickness accuracy may be determined by another method.

[0062] <Regular processing steps> This is a step of processing at least one workpiece while calculating the center of gravity of the load during processing. Specifically, as shown in Figure 3, grinding is performed on a wafer W. At this time, the position G1 (xG1, yG1) of the center of gravity of the load during processing shown in Figure 4 is calculated in real time.

[0063] <Thickness measurement step> This is a step of measuring the thickness precision (TTV) of the wafer after processing the wafer W. Specifically, a thickness measuring device (not shown) is used to measure the thickness precision of the processed wafer W. The thickness precision is, for example, on a five-level scale from precision 1 to precision 5, with precision 1 being the highest precision.

[0064] <Processing data acquisition step> This is a step of acquiring processing data including at least one set of the center of gravity of the load during processing and the thickness accuracy. Specifically, for example, as shown in the example of processing data in Fig. 6, seven wafers are processed, and seven sets of data, which are combinations of the center of gravity of the load during processing and the thickness accuracy at that time, are acquired and stored in the storage unit 90 (Fig. 3).

[0065] <Regular Steps> This is a step of identifying the center of gravity of the load during machining when the best thickness accuracy is obtained from the machining data, and defining the center of gravity of the load during machining as the target center of gravity of the load. Specifically, in the example of FIG. 6, the control means 9 (FIG. 3) identifies the center of gravity of the load during machining (X3, Y3) of set number 3 which has the highest thickness accuracy, and defines the center of gravity of the load during machining (X3, Y3) as the target center of gravity of the load. The target center of gravity of the load is stored in the memory unit 90 (FIG. 3).

[0066] <Holding step> 3, this is a step in which the wafer W is held by the holding table 5. At this time, the control means 9 is in a state in which it can acquire a predetermined target load center of gravity.

[0067] <Processing steps> As shown in FIG. 3, this is a step in which the wafer W is processed by a grinding wheel 304.

[0068] <Steps for calculating the center of gravity of the load during machining> As shown in Figures 3 and 4, this is a calculation step in which the center of gravity calculation unit 91 calculates the position G1 (xG1, yG1) of the processing load center of gravity, which is the load center of gravity of the processing unit during processing, from the processing loads F1, F2, and F3 measured by the multiple load sensors 36 during the processing step.

[0069] <Center of gravity position correction step> As shown in Figures 3 and 4, during the processing step, the tilt adjustment unit 45 corrects the position G1 (xG1, yG1) of the load gravity center during processing so that it matches the position G2 (xG2, yG2) of the target load gravity center, which is the specified load gravity center.

[0070] Specifically, as shown in FIG. 3, the control means 9 calculates and monitors the position G1 (xG1, yG1) of the center of gravity of the load during processing using the center of gravity calculation unit 91, and compares the position G1 (xG1, yG1) with the position G2 (xG2, yG2) stored in the memory unit 90. If the position G1 is misaligned with the position G2, the control means 9 controls the tilt adjustment unit 45 to align the position G1 with the position G2.

[0071] In the above embodiment, as shown in FIG. 3, the position G1 of the center of gravity is corrected by adjusting the inclination of the grinding wheel 314 using the inclination adjustment unit 45 provided in the rough grinding means 30. However, the position G1 of the center of gravity may also be corrected by adjusting the inclination of the holding table 5 using the adjustment unit 56 shown in FIG. 2, which adjusts the inclination of the holding surface 510a of the holding table 5.

[0072] In this way, the position G1 of the center of gravity of the load during processing, which is calculated in real time during processing, is corrected to the position G2 of the target center of gravity of the load that achieves good thickness accuracy, making it possible to achieve high thickness accuracy and suppress variation in thickness accuracy.

[0073] Next, the dressing method will be described. As shown in FIG. 7, when dressing (sharpening, truing) the grinding stone 304b of the grinding wheel 304 that has worn down due to use, the center of gravity of the load is monitored and dressing is performed under certain conditions.

[0074] Specifically, as shown in FIGS. 7 and 8, the dressing method is as follows: a holding step of holding the dresser board DB with a holding table 5; a dressing step in which the dresser board DB is dressed with a grinding wheel as a processing tool; The method includes a step of calculating a dressing load center of gravity, which is the load center of gravity of the machining unit at the time of dressing, from the machining load measured by the plurality of load sensors during the dressing step.

[0075] As shown in Figure 7, the dresser board DB is formed in a circular plate shape similar to the wafer W (Figure 3) and is composed of a combination of abrasive grains such as white alundum (WA) and green carbon (GC) and a bond (binding material) for fixing the abrasive grains, such as a vitrified bond or a resin bond.

[0076] In the dressing load gravity center calculation step, the position of the dressing load gravity center (position G1) is calculated in real time by the gravity center calculation unit 91, similar to the position G1 (xG1, yG1) of the processing load gravity center in the above-mentioned processing method (FIG. 4). This makes it possible to monitor the gravity center acting on the grinding wheel during dressing, and manage the dressing status.

[0077] Furthermore, the method includes a center of gravity position correction step of correcting the dressing load center of gravity measured during the dressing step so that it coincides with the target load center of gravity, which is a specified load center of gravity.

[0078] Here, the target load center of gravity may be the position G2 (xG2, yG2) (Figure 4) of the target load center of gravity stored in the memory unit 90 by the center of gravity determination step described above, or it may be a load center of gravity that is set in advance specifically for dressing.

[0079] In the above, if the position of the dressing load center of gravity (position G1) calculated in real time is deviated from, for example, the position G2 (xG2, yG2) (Figure 4) of the target load center of gravity, the tilt adjustment unit 45 is controlled to align the dressing load center of gravity with the target load center of gravity.

[0080] According to this, during dressing, the position of the load center of gravity during dressing (position G1) is corrected to the target load center of gravity G2, making it possible to maintain the dressing conditions at a constant level and performing stable dressing under specified conditions.

[0081] In the center of gravity position correction step, as shown in FIG. 3, the position of the center of gravity of the load during dressing (position G1) is corrected by adjusting the inclination of the grinding wheel 314 using the inclination adjustment unit 45 provided in the rough grinding means 30. Alternatively, the position of the center of gravity of the load during dressing (position G1) may be corrected by adjusting the inclination of the holding table 5 using the adjustment unit 56 that adjusts the inclination of the holding surface 510a of the holding table 5 shown in FIG. 2.

[0082] Next, the self-grinding method according to the present invention will be described. As shown in FIG. 9, in order to periodically shape the holding surface 510a of the holding table 5 into an appropriate shape, self-grinding is performed in which the holding surface 510a is ground with a grinding wheel 304b.

[0083] Specifically, as shown in FIGS. 9 and 10, the self-grinding method is as follows: an exposing step of exposing the holding surface 510a of the holding table 5; a self-grinding step of processing the holding surface 510a with a grinding wheel as a processing tool; The method includes a self-grinding load center of gravity calculation step for calculating the self-grinding load center of gravity, which is the load center of gravity of the processing unit during self-grinding, from the processing load measured by multiple load sensors during the self-grinding step.

[0084] In the self-grinding load gravity center calculation step, similar to the position G1 (xG1, yG1) of the load gravity center during machining in the above-described machining method (FIG. 4), the gravity center calculation unit 91 calculates the load gravity center (position G1) during self-grinding in real time. This makes it possible to monitor the gravity center acting on the grinding wheel during self-grinding and manage the dressing status.

[0085] Furthermore, the method includes a center of gravity position correction step of correcting the center of gravity of the load during self-grinding measured during the self-grinding step so that it coincides with the target center of gravity of the load, which is a specified center of gravity of the load.

[0086] Here, the target load center of gravity may be the position G2 (xG2, yG2) (FIG. 4) of the target load center of gravity stored in the memory unit 90 by the center of gravity determination step described above, or it may be a load center of gravity that is set in advance specifically for self-grinding.

[0087] In the above, if the position of the load center of gravity during self-grinding (position G1) calculated in real time is deviated from, for example, the position G2 (xG2, yG2) (Figure 4) of the target load center of gravity stored in the memory unit 90, the tilt adjustment unit 45 is controlled so that the load center of gravity during self-grinding coincides with the target load center of gravity.

[0088] According to this, during self-grinding, the position of the load center of gravity during self-grinding (position G1) is corrected to the target load center of gravity G2, making it possible to maintain a constant state of self-grinding and enabling stable self-grinding under specified conditions.

[0089] In the center of gravity position correction step, as shown in FIG. 3, the position of the center of gravity of the load during dressing (position G1) is corrected by adjusting the inclination of the grinding wheel 314 using the inclination adjustment unit 45 provided in the rough grinding means 30. Alternatively, the position of the center of gravity of the load during self-grinding (position G1) may be corrected by adjusting the inclination of the holding table 5 using the adjustment unit 56 that adjusts the inclination of the holding surface 510a of the holding table 5 shown in FIG. 2.

[0090] The present invention is not limited to the above-described embodiment, and may be embodied in various different forms within the scope of the technical concept thereof. Furthermore, the embodiments shown in the accompanying drawings are not limited to these, and may be modified as appropriate within the scope of the effects of the present invention. [Explanation of symbols]

[0091] 1 Grinding equipment 5 Holding table 9. Control Measures 20 Rough grinding feed means 21 Finish grinding feed means 30 Rough grinding means 31 Finish grinding means 36 Load sensor 45 Tilt adjustment unit 56 Tilt adjustment unit 90 Memory section 91 Center of gravity calculation part 300 spindles 303 Wheel Mount 304 grinding wheel 304b Grinding Wheel 510a retaining surface DB Dresser Board F1 Processing load G1 Position of the center of gravity of the load during processing G2 Target load center of gravity position W wafer

Claims

1. a holding table having a holding surface for holding a workpiece; a spindle; and a processing unit that processes the workpiece held on the holding surface of the holding table by a processing tool attached to the tip of the spindle; a plurality of load sensors disposed in the machining unit and measuring a machining load applied to the holding surface according to a machining feed amount of the machining tool; an inclination adjustment unit that adjusts the relative inclination of the processing unit and the holding table; In a processing device comprising at least A self-grinding method for processing a holding surface of the holding table, comprising: an exposing step of exposing a holding surface of the holding table; a self-grinding step of processing the holding surface with the processing tool; a self-grinding load gravity center calculation step of calculating a self-grinding load gravity center, which is the load gravity center of the machining unit during self-grinding, from the machining loads measured by the plurality of load sensors during the self-grinding step; A self-grinding method that includes at least:

2. a center of gravity position correcting step of correcting the center of gravity of the load during self-grinding calculated in the center of gravity of the load during self-grinding calculation step so that it coincides with a target center of gravity of the load, which is a specified center of gravity of the load; The self-grinding method according to claim 1, comprising at least the steps of:

3. The tilt adjustment unit adjusts the tilt of the processing unit.

3. The self-grinding method according to claim 1 or 2.

4. the tilt adjustment unit adjusts the tilt of the holding table; 3. The self-grinding method according to claim 1 or 2.

Images