Truing method and truing device of grinding stone

Abstract

To provide a truing device and a truing method of a grinding stone in which the variation in shape (quality) is suppressed by shaping the grinding stone having a groove shape with high accuracy and at high quality.SOLUTION: A truing device of a grinding stone 16 includes: a truer movable carriage 25 which fixes a truer 10; a shape measurement unit 35 which measures the shapes of the truer 10 and the grinding stone; a displacement evaluation unit 31 which measures the displacement between the truer 10 and the grinding stone 16; a vibration measurement unit 32 which measures the vibration between the truer 10 and the grinding stone 16; a processing heat evaluation unit 33 which measures temperature and heat flow; a control unit 30 which controls the cut amount, rotation speed, and position of the truer 10 on the basis of the measurement results of the displacement evaluation unit 31, the vibration measurement unit 32, and the processing heat evaluation unit 33; a processing condition database 37-1 which stores the measurement results of the displacement evaluation unit 31, the vibration measurement unit 32 and the processing heat evaluation unit 33, and the shapes of the truer 10 and the grinding stone 16 measured after the truing in association with each other; and a processing learning model 37-2.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a truing method and a truing device for a grinding wheel having a groove shape used in a chamfering device for the edge surface of a semiconductor wafer. [Background technology]

[0002] In recent years, the trend toward small-lot, multi-product production of semiconductor wafers and the like has been progressing. There is an increasing demand for higher precision and quality improvement in grinding wheels with groove shapes used in wafer chamfering for the purposes of small-lot, multi-product production, improved wafer quality, and improved yield.

[0003] In addition, semiconductors using materials that have a large ultra-wide band gap (UWBG) and strong bonds between the atoms that make up the crystal, such as SiC (silicon carbide), GaN (gallium nitride), gallium oxide, AlGaN, and diamond, are expected to be smaller than silicon semiconductors, have low power consumption, are highly efficient power elements, high frequency elements, and have excellent radiation resistance, and are being put into practical use. However, UWBG materials such as 4H-SiC are difficult to process, so there is a strong demand for high precision and quality improvements in the groove shape of grinding wheels.

[0004] Chamfering in the manufacturing process of semiconductor wafers requires repeating the steps of truing the grinding wheel with a truer and measuring the edge shape of the wafer after grinding until the wafer has the desired shape.

[0005] In addition, in the finishing process of the outer peripheral chamfer of a semiconductor wafer, in order to prevent the generation of grinding marks in the circumferential direction, it is known to perform so-called helical grinding, in which a grinding wheel is tilted with respect to the wafer to grind the chamfered portion. However, helical grinding requires delicate adjustments in the formation of the shape by truing the grinding wheel, which is time-consuming and requires a skilled dedicated person.

[0006] Patent Document 1 describes that in truing for helical grinding in which a truer is used to form grooves, in order to improve the transfer rate and machinability as well as the accuracy of the grooves formed by the truer, the upper or lower part of the grooves formed in the grinding wheel is processed by the truer, and then, it describes that the truer is repeatedly lowered or raised in the thickness direction relative to the grinding wheel.

[0007] Truing with laser light is also known. Patent Document 2 describes truing with laser light, and describes that an ultrashort pulse laser such as a femtosecond laser is used to obtain high processing accuracy with little thermal effect on the tool to be formed, and that truing is performed within a predetermined range before and after the traveling direction of the laser light centered on the focal point. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Patent Publication No. 2022-325 [Patent Document 2] JP 2015-98041 A Summary of the Invention [Problem to be solved by the invention]

[0009] In the above-mentioned conventional technology, the one described in Patent Document 1 required adjustments by a skilled, dedicated person in the movement of the truer when truing the grinding wheel used for chamfering. In addition, with materials that are difficult to process, such as SiC, it took a long time to process them, making it difficult to form the desired shape, and there was a large variation in the shape (creation) due to truing of the grinding wheel.

[0010] In addition, in the method described in Patent Document 2, it is difficult to widen the irradiation range, and the area that can be trued at one time is small, so it is not possible to true the entire grinding wheel, and no consideration is given to improving the precision of the overall shape of a grinding wheel having a groove shape.

[0011] The object of the present invention is to solve the problems of the conventional technology described above, and to provide an apparatus and method for truing a grinding wheel that can shape a grooved grinding wheel with high precision and quality while reducing variation in shape (quality). [Means for solving the problem]

[0012] In order to achieve the above-mentioned object, the present invention provides a method for truing a grinding wheel used in a wafer chamfering device, which determines a target shape of the grinding wheel, and trues the grinding wheel to the target shape based on at least the shapes of a truer and the grinding wheel measured before processing, and displacement conditions that indicate the relationship between the force and displacement applied to the truer and the grinding wheel.

[0013] Furthermore, in the above-mentioned method for truing a grinding wheel, it is preferable to monitor the displacement, vibration, and processing heat of the truer and the grinding wheel during the truing.

[0014] Furthermore, in the above-mentioned method for truing a grinding wheel, it is preferable that the displacement condition of the truer is an axial displacement.

[0015] Furthermore, in the above-mentioned method for truing a grinding wheel, it is preferable that the displacement condition of the grinding wheel is displacement due to bending or twisting.

[0016] Furthermore, in the above-mentioned method for truing a grinding wheel, it is preferable that after truing, the shapes of the truer and the grinding wheel are measured, and if they are compared with the target shapes of the truer and the grinding wheel and are within an acceptable range, the wafer is ground with the grinding wheel to determine whether it is good or bad.

[0017] Furthermore, in the above-mentioned grinding wheel truing method, it is preferable to associate the monitoring results with the truer and the shape of the grinding wheel measured after truing and store them as a processing condition database, and to construct a processing learning model from the processing condition database.

[0018] The present invention also provides a truing device for a grinding wheel used in a wafer chamfering device, the device comprising: a truer movable stage to which a truer is fixed and which allows a rotation axis and an X-, Y- and Z-axes to be changed; a shape measuring unit for measuring the shapes of the truer and the grinding wheel; a displacement evaluating unit for measuring the displacement between the truer and the grinding wheel; a vibration measuring unit for measuring the vibration between the truer and the grinding wheel; a processing heat evaluating unit for measuring temperature and heat flow; a control unit for controlling the cutting amount, rotation speed and position of the truer based on measurement results of the displacement evaluating unit, the vibration measuring unit and the processing heat evaluating unit; a processing condition database that stores the measurement results and the shapes of the truer and the grinding wheel measured after truing in association with each other; and a processing learning model constructed from the processing condition database.

[0019] Furthermore, in the above-mentioned grinding wheel truing device, the control unit trues the grinding wheel to a target shape based on at least the shapes of the truer and the grinding wheel measured by the shape measuring unit before processing, the axial displacement of the truer, and the displacement of the grinding wheel due to bending and twisting. Effect of the Invention

[0020] According to the present invention, a target shape of a grinding wheel is determined, and the grinding wheel is trued to the target shape based on at least the shapes of the truer and the grinding wheel measured before processing and the displacement conditions between the truer and the grinding wheel. Therefore, it is possible to obtain an apparatus and method for truing a grinding wheel that has a groove shape and can shape the grinding wheel with high precision and quality, with reduced variation in shape (quality). [Brief description of the drawings]

[0021] [Figure 1] FIG. 1 illustrates force-displacement modeling of a truer and grinding wheel according to one embodiment of the present invention. [Diagram 2] FIG. 1 is a block diagram showing an overall system configuration of a truing device according to an embodiment; [Diagram 3] An explanatory diagram showing the procedure for chamfering the wafer edge [Figure 4] An explanatory diagram of factors related to processing accuracy when truing [Diagram 5] An explanatory diagram showing deformation caused by processing forces when truing a grinding wheel and its measurement [Figure 6] FIG. 1 is an explanatory diagram of alignment of a truer and a grinding wheel according to an embodiment; [Figure 7] 1 is a configuration diagram of an alignment unit according to an embodiment; [Figure 8] 1 is a flow chart of a truing method according to one embodiment; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] Fig. 1 is a diagram showing a model of force-displacement of a truer 10 and a grinding wheel 16 according to an embodiment of the present invention, and Fig. 2 is a block diagram showing the overall system configuration of a truing device according to an embodiment. Fig. 3 is a diagram showing the procedure of chamfering a wafer W in the chamfering device.

[0023] As shown in Fig. 3, the chamfering is performed by the truer 10 performing shape transfer or processing (truing) of the grinding wheel 16, and then grinding the shape of the wafer W with the grinding wheel 16. In Fig. 3, the grinding wheel 16 is attached to a grinding wheel spindle 17 via a quill 18 and rotates. The upper surface angle θ1 and the lower surface angle θ2 of the end face of the truer 10 are often adjusted to angles slightly smaller (specifically, about 2 to 3 degrees) than the upper surface angle θ1' and the lower surface angle θ2' of the target wafer W. In addition, when performing helical grinding, the groove shape (target shape) of the grinding wheel 16 may not be symmetrical up and down, in which case the upper surface angle θ1 and the lower surface angle θ2 of the end face of the truer 10 are also adjusted accordingly.

[0024] A feature of one embodiment is that the shapes of the truer 10 and the grinding wheel 16 measured before machining and the displacement conditions of the modeled truer 10 and grinding wheel 16 are reflected in a truing program 30-1 (FIG. 8) that performs a series of truing processes. For example, the truing conditions include adjustment conditions for the pressing force of the truer 10 against the grinding wheel 16. When the truer 10 is pressed against the grinding wheel 16, the grinding wheel 16 is displaced, and the reaction force from the grinding wheel 16 causes the truer 10 to also be displaced. Since the processing force is determined by the truing conditions, it is preferable that the shape of the truer 10 has a chamfer angle that takes into consideration in advance the displacement of the truer 10 and grinding wheel 16 due to the processing force resulting from the expected truing conditions.

[0025] Fig. 1(a) shows a configuration for modeling the relationship of the displacement condition of the truer 10, and Fig. 1(b) shows a configuration for modeling the relationship of the displacement condition of the grinding wheel 16. In (a), the displacement condition of the truer 10 is measured by installing a laser displacement meter 20 under the truer 10 and applying a known load from above with a tension gauge 40 (a force sensor, which can also be a weight). Then, the displacement δ is measured with the laser displacement meter 20. As a result, the displacement condition (force-displacement relationship) of the truer 10 is found as a displacement in the axial direction.

[0026] In FIG. 1(b), the displacement condition of the grinding wheel 16 is measured by installing a laser displacement meter 20 on the side of the grinding wheel 16, pressing the truer 10 against the groove of the grinding wheel 16 with a known force, measuring the bending rigidity of the grinding wheel 16, and determining the displacement due to bending and twisting of the grinding wheel 16.

[0027] As a result, the displacement condition (force-displacement relationship) of the grinding wheel 16 is obtained as the displacement due to bending and twisting of the grinding wheel 16. Variations in the quality of the truer 10 and the grinding wheel 16 are reflected as other displacement conditions. The grinding wheel 16 is attached to a grinding wheel spindle 17 via a quill 18 and rotates.

[0028] Fig. 4 is an explanatory diagram of factors related to the processing accuracy during truing. Factors related to the processing accuracy include bending, twisting, vibration as indicated by the arrows on the grinding wheel 16, the surface shape of the truer 10, the state of the abrasive grains, the force f1 applied during shape transfer, deformation of the truer 10, processing heat, coefficient of thermal expansion (CTE), alignment of the truer 10 and the grinding wheel 16, etc., as shown in Fig. 4.

[0029] FIG. 5 is an explanatory diagram showing deformation of the truer due to processing force when truing the grinding wheel 16 and its measurement. FIG. 5(a) shows the stress (processing force) applied to the truer 10 when truing the upper surface of the grinding wheel 16 and the associated displacement direction of the grinding wheel 16, and FIG. 5(b) shows the stress (processing force) applied to the truer 10 when truing the lower surface of the grinding wheel 16 and the associated displacement direction of the grinding wheel. When truing the upper surface of the groove, the truer 10 is pressed against the upper surface of the grinding wheel 16, and a stress is applied to the truer 10 in the direction of the arrow as a reaction force. The truer 10 will deform (displace) in the direction of the arrow depending on its material, etc. (rigidity). On the other hand, the axis of the grinding wheel 16, as shown in FIG. 5(a), is displaced in a direction in which the rotation axis tilts from the dashed line to the broken line or escapes to the horizontal direction (X). It should be noted that the drawings are schematic and are exaggerated for the purpose of explanation, and the actual displacement may be smaller than the displacement shown in the drawings.

[0030] The same is true when truing the bottom surface of the groove. Stress is applied to the truer 10 as shown by the arrow, causing it to deform (displace). As the truer 10 is pressed against the axis of one of the grinding wheels 16, the axis tilts from the dashed line to the broken line and escapes to the horizontal direction (X), as shown in Figure 5(b). An eddy current sensor 21 installed below the grinding wheel 16 measures the displacement of the grinding wheel 16 due to the processing force during truing of both the top and bottom surfaces. The relationship between the processing force and deformation (displacement) of the truer 10 and the grinding wheel 16 is determined in advance as a displacement condition as shown in FIG.

[0031] In order to improve the machining accuracy, it is necessary to build a machining control model that analyzes the effect of deformation due to force, heat, etc. on the machining accuracy, identify factors that strongly affect performance, and use machine learning to automate the process. In particular, the alignment of the truer 10 and the grinding wheel 16 is the standard for these. When the device is operated for truing and grinding, grinding waste is generated and coolant, etc. is constantly supplied to the grinding area, creating harsh conditions for sensing, so a robust measurement mechanism is important.

[0032] Fig. 6 is an explanatory diagram of the alignment of the truer 10 and the grinding wheel 16, and Fig. 7 is a configuration diagram of the alignment unit. The laser displacement meter 20 measures the two-dimensional cross-sectional shapes of the truer 10 and the grinding wheel 16. From the two-dimensional cross-sectional shapes measured by the laser displacement meter 20, the center T of the end face of the truer 10 and the center position M of the groove bottom of the grinding wheel 16 are derived. The relative positional relationship between the truer 10 and the grinding wheel 16 such that these coincide is set as a reference position. The alignment is performed by moving the positions of the truer 10 and the grinding wheel 16 to match this reference position.

[0033] As shown in Figure 7, the alignment of the truer 10 and the grinding wheel 16 is performed by embedding a first conductor 23-1 (or magnetic material) in the grinding wheel 16 and a second conductor 23-2 (or magnetic material) in the chuck table 24 that fixes the truer 10, and detecting their positions using eddy current sensors 21-1 and 21-2.

[0034] 7, the truer 10 is fixed to a chuck table 24. The second conductor 23-2 (or magnetic material) is embedded in the chuck table 24. The first conductor 23-1 (or magnetic material) is embedded in the center of the groove bottom of the grinding wheel 16. The moving stage 22 has a length measuring function, and has eddy current sensors 21-1 and 21-2 attached thereto.

[0035] Eddy current sensor 21-1 is attached to moving stage 22 so as to be movable in the Z direction to a position facing first conductor 23-1 (or magnetic material), and determines the position of the groove bottom center of grinding wheel 16 as Z1. Eddy current sensor 21-2 is attached to moving stage 22 so as to be movable in the Z direction to a position facing second conductor 23-2 (or magnetic material), and determines the position of end face center T of truer 10 as Z2. The alignment of end face center T of truer 10 and groove bottom center position M of grinding wheel 16 will coincide with the set reference position if truer 10 is moved so that the difference between Z1 and Z2 becomes a predetermined value.

[0036] 2, the control unit 30 controls the cutting depth, rotation speed, position, etc. of the truer 10 as processing conditions based on evaluations by a displacement evaluation unit 31, a vibration measurement unit 32, and a processing heat evaluation unit 33. The displacement evaluation unit 31 evaluates the deformation (displacement) of the truer 10 and the grinding wheel 16 during processing based on measurements by a force-displacement measurement unit 36.

[0037] The displacement evaluation unit 31 measures and rates (quantifies based on a standard) the deformation (displacement from no load) of the truer 10 and grinding wheel 16 during processing based on the modeled displacement conditions of the truer 10 and grinding wheel 16 due to a known load load shown in Fig. 1 (b). The vibration measurement unit 32 measures the vibration of the truer 10 and grinding wheel 16 during processing.

[0038] The vibration measuring unit 32 may be common to the laser displacement meter 20 and the eddy current sensor 21 shown in Fig. 6. In other words, the vibration may be estimated from the measured values ​​of these. The processing heat evaluation unit 33 evaluates the processing heat of the truer 10 and the grinding wheel 16 using the measured values ​​of temperature and heat flow by the thermocouples and heat flow meters constituting the temperature and heat flow measurement unit 34 .

[0039] The shape measuring unit 35 is composed of the laser displacement meter 20 and the like, and measures the two-dimensional cross-sectional shapes of at least the truer 10 and the grinding wheel 16 . The grinding wheel 16 is attached to a grinding wheel spindle 17. The truer 10 is fixed to a chuck table 24 mounted on a truer moving stand 25, and the rotation axis, X-axis, Y-axis, and Z-axis are variable.

[0040] The processing condition database 37-1 stores the results of monitoring the displacement, vibration, and processing heat of the truer 10 and the grinding wheel 16, and the measurement results of the shape measuring unit 35 after truing in association with each other. The stored results are constructed as a processing learning model 37-2. In addition, the control unit 30 controls the grinding heat by the cooling water system.

[0041] 8 is a flow chart of the truing method. This flow also includes a procedure for optimizing the shape of the truer 10. First, in step S35, the shape of the truer and grinding wheel before machining is measured. The target shape of the truer 10 is determined as shown in Fig. 1(a) by taking into account the axial displacement condition of the truer 10 obtained in advance, and is set to the upper surface angle θ1, the lower surface angle θ2, the chamfer angle, etc. of the end surface shown in Fig. 3.

[0042] Next, the target shape of the grinding wheel 16 is determined and converted into data (step S1). The truing program 30-1 reflects the two-dimensional cross-sectional shapes of the truer 10 and the grinding wheel 16 measured before machining in step S35, the displacement conditions of the truer 10 and the grinding wheel 16 (bending, twisting, etc. of the grinding wheel 16) modeled in step S31, and the target shape. (Step S2)

[0043] Next, in step S3, truing is performed according to a truing program 30-1. In truing, the grinding wheel 16 is machined by the grinding machine 10 so as to have a target shape. In step S3, as shown in FIG. 6, the position where the center T of the end face of the truer 10 coincides with the center position M of the groove bottom of the grinding wheel 16, as measured by the laser displacement meter 20, is set as the reference position.

[0044] During truing, the processing conditions are monitored by the displacement evaluation unit 31, the vibration measurement unit 32, the processing heat evaluation unit 33, the temperature / heat flow measurement unit 34, etc. (Step S4). After truing, the shapes of the truer 10 and the grinding wheel 16 are measured by the laser displacement meter 20 of the shape measuring unit 35 (step S5) and judged as good or bad. If the target shapes of the truer 10 and the grinding wheel 16 are compared and are within the allowable range, the wafer W is then ground by the grinding wheel 16 and judged as good or bad with respect to the design value (target value) of the edge (step S6).

[0045] If the trued truer 10 and the grinding wheel 16 are not within the target shape and the wafer W ground by the grinding wheel 16 with the transferred shape is not within the allowable range of the design value (target value) of the edge, the process returns to step S35 and step S1. The processing conditions and the two-dimensional cross-sectional shape after processing are associated with each other and stored in a database as a processing condition database 37-1, and a processing learning model 37-2 is constructed (step S37).

[0046] The machining condition database 37-1 is stored as a database in association with the results of monitoring by the displacement evaluation unit 31, the vibration measurement unit 32, the machining heat evaluation unit 33, the temperature / heat flow measurement unit 34, etc. as machining conditions during truing. The machining learning model 37-2 is constructed from the databased machining condition database 37-1. In step S3, the truing program 30-1 refers to the machining learning model 37-2.

[0047] The quality judgment in steps S5 and S6 may utilize results stored in advance in the processing condition database 37-1. Also, it is preferable that the quality judgment of the grinding wheel 16 after processing in step S5 utilizes the results stored in the processing condition database 37-1.

[0048] The machining learning model 37-2 is a machine learning model that outputs the results of evaluation and judgment made by a computer for the data that is the result accumulated in the machining condition database 37-1. The truing program 30-1 inputs a query to the machining learning model 37-2 as necessary and obtains the results of evaluation and judgment.

[0049] As described above, in one embodiment, monitoring is performed during truing using the displacement evaluation unit 31, vibration measurement unit 32, processing heat evaluation unit 33, temperature / heat flow measurement unit 34, etc. Furthermore, since truing is performed by the truing program 30-1 using the processing condition database 37-1 and processing learning model 37-2, it is possible to improve the accuracy and quality of the groove shape and suppress variation in the shape.

[0050] The explanation in FIG. 3 has been given of the transfer of the shape of the truer 10, but in order to achieve higher precision, it is also possible to machine the upper or lower part of the groove to be formed in the grinding wheel 16 with the truer 10, and then to grind one side at a time by lowering or raising the truer 10 in the thickness direction relative to the grinding wheel 16.

[0051] During truing, monitoring is performed by the displacement evaluation unit 31, the vibration measurement unit 32, the processing heat evaluation unit 33, the temperature / heat flow measurement unit 34, etc. The construction and use of the processing condition database 37-1 and the processing learning model 37-2 can be applied to the wafer W made of any of the following materials: 4H-SiC, which is a difficult-to-process material, other polytypes (3C-SiC, 6H-SiC, 15R-SiC, etc.), GaN (gallium nitride), gallium oxide, and AlGaN. In one embodiment, even if the wafer W is made of a difficult-to-process material, it is possible to achieve high quality, particularly suitable for later processes (high-precision shape formation, uniform surface condition (waviness / roughness)). [Explanation of symbols]

[0052] 10. Trua 16...Grinding wheel 17…Grinding wheel spindle 18. Quill 20...Laser displacement gauge 21... Eddy current sensor 22...Mobile stage 23-1…First conductor 23-2…Second conductor 24…Chuck table 25…Tsurua mobile stand 30...Control section 30-1… Truing Program 31...Displacement evaluation section 32…Vibration measurement section 33…Heat Processing Evaluation Section 34...Temperature / heat flow measurement section 35...Shape measurement section 36…Displacement measurement section 37-1... Processing condition database 37-2…Processed learning model 40…Tension gauge W: Wafer

Claims

1. A method for truing a grinding wheel used in a wafer chamfering device, comprising: determining a target shape of the grinding wheel; A method for truing a grinding wheel, characterized by controlling the cutting depth, rotational speed, and position of the truer relative to the grinding wheel to true the grinding wheel to the target shape based on at least the shapes of the truer and the grinding wheel measured before processing, and displacement conditions that indicate the relationship between the force and displacement applied to the truer and the grinding wheel in at least one of the axial and horizontal directions measured under load.

2. 2. The method for truing a grinding wheel according to claim 1, further comprising monitoring displacement, vibration, and processing heat of the truer and the grinding wheel during the truing.

3. 3. The method for truing a grinding wheel according to claim 1, wherein the displacement condition of the truer is displacement in the axial direction.

4. 4. The method for truing a grinding wheel according to claim 3, wherein the displacement condition of the grinding wheel is displacement due to bending and twisting.

5. A method for truing a grinding wheel as described in claim 1 or 2, characterized in that after the truing, the shapes of the truer and the grinding wheel are measured, and if they are compared with the target shapes of the truer and the grinding wheel and are within an acceptable range, the wafer is ground with the grinding wheel and a determination of pass / fail is made.

6. The grinding wheel truing method according to claim 2, characterized in that the monitoring results and the shapes of the truer and the grinding wheel measured after the truing are associated and stored as a processing condition database, and a processing learning model is constructed from the processing condition database.

7. In a truing device for grinding wheels used in a wafer chamfering device, a truer moving table that fixes the truer and allows the rotation axis and X, Y, and Z axes to be changed; a shape measuring unit for measuring the shapes of the truer and the grinding wheel; a displacement evaluation unit for measuring a displacement between the truer and the grinding wheel; a vibration measuring unit for measuring vibration between the truer and the grinding wheel; a processing heat evaluation unit that measures temperature and heat flow; a control unit that controls the cutting depth, rotation speed, and position of the truer based on the measurement results of the displacement evaluation unit, the vibration measurement unit, and the processing heat evaluation unit; a processing condition database storing the measurement results and the shapes of the truer and the grinding wheel measured after truing in association with each other; a machining learning model constructed from the machining condition database; Equipped with The control unit uses the processing condition database and the processing learning model to control the cutting depth, rotational speed, and position of the truer relative to the grinding wheel so as to make the grinding wheel have a target shape.

8. The grinding wheel truing device of claim 7, characterized in that the control unit performs the truing so that the grinding wheel has a target shape based on at least the shapes of the truer and the grinding wheel measured by the shape measuring unit before processing, the axial displacement of the truer, and the displacement of the grinding wheel due to bending and twisting.

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