GRINDING DEVICE
Patent Information
- Authority / Receiving Office
- DE · DE
- Patent Type
- Patents
- Current Assignee / Owner
- DISCO CORP
- Filing Date
- 2021-02-04
- Publication Date
- 2026-07-23
Smart Images
Figure 00000000_0000_ABST
Abstract
Description
BACKGROUND OF THE INVENTION AREA OF THE INVENTION
[0001] The present invention relates to a grinding device for grinding a workpiece and a grinding method for grinding a workpiece. DESCRIPTION OF THE RELATED STATE OF THE ART
[0002] Grinding devices for grinding a surface of semiconductor wafers are used in the process of manufacturing semiconductor chips. A grinding device comprises a clamping table for holding the other surface of a semiconductor wafer, which faces the surface to be ground. A rotary actuator, such as an electric motor, for rotating the clamping table about its central axis, also referred to as the "shaft," is located under a lower section of the clamping table. The rotary actuator has a shaft that is coupled to the lower section of the clamping table. The clamping table has an upper surface that is a protruding conical surface, which serves as a holding surface for attracting the semiconductor wafer under suction.
[0003] A grinding unit is arranged above the clamping table. The grinding unit has a cylindrical spindle with a lower end to which an upper surface of a disc-shaped holder is attached. The disc-shaped holder has a lower surface with an annular grinding wheel mounted to it. The grinding wheel comprises an annular base made of metal and several grinding stones arranged on a lower surface of the annular base. Each grinding stone is block-shaped. The grinding stones each have lower surfaces that together define a grinding surface for grinding the semiconductor wafer.
[0004] To grind one face of a semiconductor wafer on the grinding device, a resin-based protective strip is attached to the other face of the wafer. The other face is then held against the clamping table's holding surface by suction, with the protective strip inserted between them. At this point, the wafer is elastically deformed into a protruding conical shape that matches the protruding conical shape of the clamping table's holding surface. The clamping table's shaft is tilted at a predetermined angle relative to the spindle, so that the grinding surface of the grinding wheels is essentially parallel to a local curved region of one face of the wafer.To grind one surface of the semiconductor wafer, the grinding wheel is fed downwards towards the semiconductor wafer on the clamping table, while the clamping table and the grinding wheel are rotated in their respective directions. When the grinding surface comes into contact with the locally curved area of that one surface of the semiconductor wafer, that surface is ground by the grinding stones.
[0005] Semiconductor wafers that have been ground can exhibit varying thicknesses depending on the type of protective tape used, the diameter of the semiconductor wafers, etc. A process is known in which data on such thickness variations are collected in advance, and when a semiconductor wafer is to be ground, the angle of the spindle relative to the rotational axis of the clamping table is automatically adjusted based on the collected data (see, for example, the published Japanese patent number 2009-90389). However, in a conventional grinding device, the spindle is essentially parallel to vertical directions and cannot be tilted with respect to them. Therefore, it is common practice to tilt the rotational axis of the clamping table instead of the spindle.
[0006] A tilt adjustment unit for adjusting the tilt of the clamping table's axis of rotation is located beneath the clamping table. The tilt adjustment unit comprises a fixed support mechanism, a first movable support mechanism, and a second movable support mechanism, each supporting the clamping table at three points. When a semiconductor wafer is ground by the grinding device, a curved local area of one face of the semiconductor wafer to be ground is positioned by the grinding surface over a region between the fixed support mechanism and the first movable support mechanism. Therefore, a relatively large load is applied to both the fixed and first movable support mechanisms by the grinding surface.However, the load applied to the second movable support mechanism is relatively small compared to the load applied to the fixed support mechanism and the first movable support mechanism. SUMMARY OF THE INVENTION
[0007] As the semiconductor wafer is ground by the grinding device, the inclination of the clamping table consequently tends to change, resulting in larger thickness variations of the semiconductor wafer.
[0008] The present invention was developed in consideration of the problems mentioned above. It is an object of the present invention to provide a grinding device that prevents thickness variations of a semiconductor wafer being ground from worsening, even when a high grinding load is applied locally to a clamping table that holds the semiconductor wafer.
[0009] In accordance with one aspect of the present invention, a grinding device for grinding a workpiece is provided, comprising a clamping table for holding the workpiece thereon, a plate-shaped table base supporting the clamping table, a grinding unit for grinding the workpiece held on the clamping table with a grinding wheel, the grinding unit comprising a spindle and the grinding wheel mounted at one end of the spindle, a load sensing unit with load measuring devices for sensing a load applied by the grinding unit to the table base, a tilt adjustment unit supporting the table base for adjusting a tilt of the table base, and a memory for storing a correlation relationship between loads applied to the table base and changes in the tilt of the table base caused by the loads.and a controller with a processor for controlling the tilt adjustment unit based on the load detected by the load sensing unit and the correlation relationship to adjust the tilt of the table base so that a change in the tilt of the table base corresponding to the detected load is compensated.
[0010] Preferably, the tilt adjustment unit has a fixed support mechanism and several movable support mechanisms, the correlation relationship represents a correlation relationship between loads applied to the fixed support mechanism and the movable support mechanisms and changes in the tilt of the table base caused by respective shortenings of the fixed support mechanism and the movable support mechanisms on which the loads are applied, and the control adjusts respective lengths of the movable support mechanisms based on the correlation relationship in order to adjust the tilt of the table base.
[0011] In accordance with another aspect of the present invention, a grinding method for grinding a workpiece is provided, comprising a first inclination adjustment step involving the adjustment of an inclination of a table base supporting a clamping table to align a grinding surface, defined by respective lower surfaces of grinding stones of a grinding wheel arranged on a surface of a wheel base and lined up along circumferential directions of the surface of the wheel base, and a local area of a holding surface of the clamping table parallel to each other, overlapping a contact area between the grinding stones and the workpiece held on the clamping table; following the first inclination adjustment step, a first grinding step involving grinding the workpiece with the grinding wheel and capturing a load applied to the table base;After the first grinding step, a second tilt adjustment step is performed, adjusting the tilt of the table base to compensate for changes in the tilt of the table base based on the correlation between loads applied to the table base and changes in the tilt of the table base caused by the loads, and the load detected in the first grinding step, in order to compensate for changes in the tilt of the table base corresponding to the load detected in the first grinding step; and after the second tilt adjustment step, a second grinding step is performed, grinding the workpiece to a predetermined finished thickness.
[0012] Preferably, the correlation relationship represents a correlation relationship between loads applied to a fixed support mechanism and several movable support mechanisms, and changes in the inclination of the table base caused by respective shortenings of the fixed support mechanism and the movable support mechanisms on which the loads are applied. The fixed support mechanism and the several movable support mechanisms are configured to adjust the inclination of the table base, and the second inclination adjustment step comprises a step of adjusting respective lengths of the movable support mechanisms based on the loads applied to the fixed support mechanism and the movable support mechanisms, and the correlation relationship.
[0013] Preferably, the grinding process further comprises, after the second grinding step, a third grinding step in which a different workpiece is held and the other workpiece is ground with the grinding wheel, while the lengths of the movable support mechanisms retain the lengths that were set in the second inclination adjustment step.
[0014] Preferably, the third grinding step comprises a step involving the detection of a load applied to the table base, just as the other workpiece is ground with the grinding wheel, wherein the grinding method further comprises a third inclination adjustment step involving the adjustment of the inclination of the table base in order to compensate for a change in the inclination of the table base that corresponds to the load detected in the third grinding step, based on the load detected in the third grinding step and the correlation relationship.
[0015] The grinding device, in accordance with the present invention, includes a memory for storing the correlation relationship between loads applied to the table base and changes in the table base's inclination. The grinding device also includes a control unit for controlling the inclination adjustment unit based on the load detected by the load sensing unit and the correlation relationship stored in the memory. The control unit adjusts the table base's inclination to compensate for any changes in the table base's inclination corresponding to the detected load. Consequently, it prevents workpiece thickness variations from worsening compared to a situation where the table base's inclination is not adjusted.
[0016] The above and other problems, features and advantages of the present invention, as well as the manner of its implementation, will best become clearer by studying the following description and attached claims, with reference to the attached drawings, which show some preferred embodiments of the invention, and the invention itself will be best understood thereby. List of characters Fig. Figure 1 is a perspective view illustrating a structural example of a grinding device in accordance with a preferred embodiment of the present invention; Fig. 2 is a partial sectional side view of a clamping table and other components of the grinding device; Fig. 3A is a partial sectional side view of the clamping table and other components; Fig. 3B is a top view of the clamping table at the time when a workpiece held on the clamping table is being ground; Fig. Figure 4 is a graph that illustrates, using an example, the correspondence relationship between loads applied to the support mechanisms and shortenings of the support mechanisms; Fig. 5 is a partial sectional side view of the clamping table and other components; Fig. Figure 6A is a diagram illustrating a cross-section of a profile of the back of a workpiece that has been ground under a grinding load of 30 N; Fig. Figure 6B is a diagram illustrating a cross-sectional profile of the back of a workpiece that has been ground under a grinding load of 60 N; Fig. Figure 7 is a partial sectional side view illustrating the way in which a workpiece is ground by the grinding device; Fig. Figure 8 is a flowchart of a grinding process in accordance with a first embodiment of the present invention; Fig. Figure 9A is a lateral partial sectional view illustrating the way in which another workpiece is ground by the grinding device; Fig. Figure 9B is a partial sectional side view illustrating how the tilt of a table base is further adjusted; and Fig. Figure 10 is a flowchart of a grinding process in accordance with a second embodiment of the present invention. DETAILED EXPLANATION OF THE PREFERRED EXECUTION FORMS
[0017] A grinding device in accordance with a preferred embodiment of the present invention is described in detail below with reference to the accompanying drawings. Fig. Figure 1 illustrates a structural example of the grinding device, characterized by Figure 2, in a perspective view. Fig. 1. Some components of the grinding device 2 illustrated as function blocks. In Fig. 1. The X-axis, Y-axis, and Z-axis directions represent directions that are perpendicular to each other. The Z-axis directions are also referred to as vertical directions, directions upwards and downwards, or grinding feed directions.
[0018] The grinding device 2 closes a base 4 one, on which the components of the grinding device 2 are mounted. The base 4 has a right-angled opening 4a on, which is defined in an upper surface of it and extends longitudinally along the X-axis directions. The opening 4aIt incorporates a ball screw-like X-axis motion mechanism. 8 The X-axis movement mechanism 8 The diagram features a pair of guide rails (not illustrated) extending along the X-axis directions and a ball screw (not illustrated) positioned between the guide rails and extending along the X-axis directions. A stepper motor (not illustrated) is coupled to one end of the ball screw to rotate it about its central axis.
[0019] The ball screw is operated via a threaded nut (not illustrated) mounted on a lower surface of a table (not illustrated) that is movable in the X-axis direction. When the stepper motor is energized, it rotates the ball screw about its central axis, causing the nut to move the table along the X-axis. A table cover 8ais arranged on the table which can be moved in the X-axis direction, and a clamping table 10 is used as a holding table on the table cover 8a assembled.
[0020] Structural details of the clamping table 10 will be discussed below with reference to Fig. 2 described. Fig. Figure 2 illustrates the clamping table in a partial sectional side view. 10 and other components of the grinding device 2 The clamping table 10 has a disc-shaped frame 12 on, which is made of ceramic. The frame 12 It has a defined disc-shaped recess that is open at the top. The frame 12features a suction channel (not illustrated) defined in the base of the recess, with one end exposed at the base of the recess and another end connected to a suction source (not illustrated), such as an ejector. A porous plate 14 is firmly positioned in the recess. The porous plate 14 It has a substantially flat lower surface and a conical upper surface, including a central area that protrudes slightly upwards compared to an outer circumferential area. When the suction source is activated, it creates a negative pressure that is drawn through the suction channel and the porous plate. 14 on whose conical upper surface it acts, which serves as a holding surface 14a serves.
[0021] A cylindrical shaft 16 It has an upper section that connects to a lower section of the clamping table. 10 is coupled. The wave16 This is provided by the output shaft of a rotary actuator (not illustrated), such as a servo motor. When the rotary actuator is energized, it rotates the shaft. 16 around its central axis, which is the clamping table 10 around the central axis of the shaft 16 rotates. The clamping table 10 It rotates on a ring-shaped bearing 18 supported by a lower surface of the clamping table around the shaft 16 is arranged. A ring-shaped support plate 20 is on a lower surface of the bearing 18 around the wave 16 attached.
[0022] A ring-shaped, plate-shaped table base 22 is under the support plate 20 around the wave 16 arranged. A load sensing unit 24 is between a flat lower surface of the support plate 20 and a flat upper surface of the table base 22arranged. The load detection unit 24 features three load measuring devices 24a on, which run circumferentially along the upper surface of the table base 22 are spaced apart from each other. The load measuring devices 24a They each have upper surfaces that align with the lower surface of the support plate. 20 be kept in contact. Each of the load measuring devices 24a For example, a diaphragm load cell is a load cell, although it can also be a column-type load cell. The load cell includes a sensor for converting a load into an electrical signal. The load sensor includes a piezoelectric sensor, which may, for example, have a piezoelectric device, although it could also have a strain gauge, an electrostatic capacitance sensor, or something similar.
[0023] The clamping table 10 will be with the warehouse 18 , the support plate 20 and the load recording unit 24inserted between at the table base 22 supported. If the holding surface 14a When pressed downwards, the load, that is, the grinding load, which passes through the holding surface 14a on the table base 22 is applied, consequently by the load detection unit 24 measured. Three support mechanisms that form a fixed support mechanism 26a , a first movable support mechanism 26b and a second movable support mechanism 26c include those in circumferential directions of the table base 22 are spaced apart from each other and are located on a lower surface of the table base. 22 arranged. Each of the support mechanisms is located directly below one of the load measuring devices. 24a positioned. These three support mechanisms are referred to together in this description as a “tilt adjustment unit 26”.
[0024] The table base 22is provided by the fixed support mechanism 26a supported at one point. The fixed support mechanism 26a It features a support post, that is, a fixed shaft, of a predetermined length. The support post has an upper section that is attached to an upper support body, which is located on the lower surface of the table base. 22 is attached, and has a lower section that is attached to a support base. The table base 22 is also achieved at two other points by the first movable support mechanism 26b or the second movable support mechanism 26c supported. The first movable support mechanism 26b and the second movable support mechanism 26c Each has a support post 28 , that is, a movable shaft, which has a distal upper end section with an external thread.
[0025] The distal upper end sections with external threads of the support posts 28 are rotatable with their respective upper support bodies 30 coupled, which are attached to the lower surface of the table base 22 are attached. In particular, the upper support bodies 30 Designed as column-shaped elements made of metal, such as rods with defined holes and internal threads. The distal upper end sections of the support posts have external threads. 28 are rotatable with the internal threaded holes in the upper support bodies 30 in thread engagement. The support posts 28 of the first movable support mechanism 26b and the second movable support mechanism 26c have outer circumferential surfaces that are attached to respective ring-shaped bearings 34 are attached with a predetermined diameter. The bearings 34 are attached to the respective stepped support plates 26supported. Consequently, the first movable support mechanism will be 26b and the second movable support mechanism 26c through the support plates 36 supports.
[0026] The support posts 28 Each has lower sections equipped with stepper motors. 32 are coupled, which are the support posts 28 rotate around their central axes. When the stepper motors 32 When turned over, they rotate the support posts. 28 around their central axes in one direction, which forms the upper support bodies 30 lifts. When the stepper motors 32 When turned over, they rotate the support posts. 28 around their central axis in the other direction, which forms the upper support bodies 30 lowers. The upper support bodies 30 They are thus raised or lowered to adjust the tilt of the table base. 22 , that is, the clamping table 10, to adjust. The lengths in the Z-axis directions of the fixed support mechanism. 26a of the first movable support mechanism 26b and the second movable support mechanism 26c can be reduced or shortened under a load directed downwards towards the table base 22 is applied. For example, the distance between the support post and the upper support body of the fixed support mechanism can be adjusted. 26a be reduced and the distances between the support posts 28 and the upper support structures 30 of the first movable support mechanism 26b and the second movable support mechanism 26c can be reduced, so that the support mechanisms 26a , 26b and 26c They can be shortened elastically.
[0027] Referring again to Fig. 1. Other components of the grinding device will be described below. 2described. The opening 4a is equipped with a pair of bellows-shaped, dustproof, drip-proof covers 40 covered, each in the X-axis directions on both sides of the table cover 8a are arranged. The dustproof, drip-proof covers 40 They are extendable and retractable in the X-axis directions, while the table, which is movable in the X-axis direction, moves in the X-axis directions. A control panel 42 The input of grinding conditions, etc., is located on the upper surface of the base. 4 at one end of this, arranged in the X-axis directions. A support structure. 6 in the form of a rectangular cuboid, it stands from the base 4 at its other end, it protrudes upwards in the X-axis directions.
[0028] The supporting structure 6 supports a Z-axis movement mechanism 44 on their front surface, which is the control panel 42is facing the Z-axis movement mechanism. 44 includes a pair of Z-axis guide rails 46 , extending along the Z-axis directions, and a plate movable in the Z-axis direction 48 one that is attached to the Z-axis guide rails 46 It is mounted so that it can be moved along the Z-axis. A nut (not illustrated) is attached to a rear surface of the plate, which is movable in the Z-axis direction. 48 assembled, which the support structure 6 is turned towards.
[0029] The mother is operational with a Z-axis ball screw. 50 in the threaded engagement, which is between the Z-axis guide rails 46 is arranged and extends along the Z-axis directions. The Z-axis ball screw 50 It can be rotated around its central axis. A Z-axis stepper motor. 52 is connected to one end of the Z-axis ball screw 50coupled in the Z-axis directions. When the Z-axis stepper motor 52 When excited, it rotates the Z-axis ball screw. 50 around its central axis, which causes the mother to move the plate in the Z-axis direction 48 along the Z-axis guide rails 46 to move in the Z-axis directions. A support block 54 is located on a front surface of the plate that can be moved in the Z-axis direction 48 mounted, which is attached to the control panel 42 is turned towards.
[0030] The support block 54 This is supported by a grinding unit 56 The grinding unit 56 features a hollow cylindrical spindle housing 58 up, which is attached to the support block 54 is attached. A cylindrical spindle. 60 , which extends along the Z-axis directions, has a section that is rotatable in the spindle housing 58 is recorded and located under the spindle housing 58protrudes. The spindle 60 has an upper end with which a servo motor can be attached. 62 for turning the spindle 60 is coupled around its central axis. The spindle 60 has a lower end that is separated from the spindle housing 58 is exposed and attached to an upper surface of a disc-shaped disc holder 64 is attached, which is made of a metallic material, such as stainless steel.
[0031] The disc holder 64 It has a lower surface on which a ring-shaped grinding wheel is attached. 66 , which has essentially the same diameter as the disc holder 64 , is mounted. As in Fig. As illustrated in 2, the grinding wheel 66 a ring-shaped disc base 68 , which is made of a metallic material, such as stainless steel, and contains several grinding stones 70on, which are attached to a lower surface of the disc base 68 The grinding stones are arranged and spaced apart from each other in their circumferential directions. 70 have lower surfaces that are essentially in the same vertical positions relative to each other in the Z-axis directions and together form a grinding surface 70a for grinding a workpiece 11 define (see Fig. 3A and Fig. 3B).
[0032] The workpiece 11 , which is achieved through a suction effect on the holding surface 14a held by the grinding wheel 66 polished. As in Fig. As illustrated in 1, the workpiece 11 For example, a semiconductor wafer, primarily made of silicon carbide (SiC), with a diameter of approximately 150 mm. Components, such as integrated circuits (ICs), are attached to one end face. 11a of the workpiece 11arranged. The workpiece 11 can be made from any material other than silicon carbide, such as gallium arsenide (GaAs), gallium nitride (GaN), silicon (Si), sapphire, etc.
[0033] A protective strip (not illustrated) to protect the components is located on the front. 11a of the workpiece 11 attached. For sanding a back side 11b of the workpiece 11 its front side 11a via suction effect on the holding surface 14a of the clamping table 10 held. Since the holding surface 14a The upwardly protruding conical shape is achieved through suction on the holding surface. 14a held workpiece 11 elastically deformed into a protruding conical shape that matches the protruding conical shape of the holding surface 14a matches. If the back 11b of the workpiece 11 at the holding surface 14athrough the grinding unit 56 When the shaft is ground, it becomes smooth. 16 inclined so that the grinding surface 70a and a local area 14b the holding surface 14a , which of the grinding surface 70a facing each other, they lie parallel to each other. Fig. Figure 3A illustrates the clamping table in a partial sectional side view. 10 and other components that illustrate the way in which the workpiece 11 at the holding surface 14a through the grinding stones 70 is being sanded while the grinding surface 70a and the local area 14b the holding surface 14a essentially lie parallel to each other. Fig. 3B illustrates the clamping table 10 at the time when the workpiece 11 The grinding process is shown in top view.
[0034] While the grinding wheel 66 and the clamping table 10The grinding wheel is rotated around its respective central axes in a predetermined direction, for example counterclockwise when viewed from above. 66 fed for grinding, that is, it is moved downwards in the direction of the workpiece. 11 at the holding surface 14a moved. Then the back is turned. 11b of the workpiece 11 , a local curved area that is attached to the local area 14b the holding surface 14a is positioned, that is, a local curved area of the back 11b , which is connected to the local area 14b the holding surface 14a overlapping, with the grinding surface 70a brought into contact and thereby polished. In Fig. 3B is applied to a contact area 13 between the grinding surface 70a and the reverse 11b of the workpiece 11, that is, a grinding area, indicated by the curved, thick, dashed line. Furthermore, in Fig. 3B to the load measuring devices 24a indicated by dashed circles.
[0035] As in Fig. 3B illustrated in top view, is the contact area 13 directly above an area between the fixed support mechanism 26a and the first movable support mechanism 26b positioned. When the grinding wheel 66 the workpiece 11 on the clamping table 10 When pressed, it exerts more force compared to the second movable support mechanism. 26c consequently a greater load on the fixed support mechanism 26a and the first movable support mechanism 26b out of. Fig. Figure 4 is a graph that uses an example to illustrate the correspondence relationship between loads acting on the support mechanisms. 26a , 26b and 26cto be applied, and shortening of the support mechanisms 26a , 26b and 26c illustrated. In Fig. 4. The correspondence relationship is considered the same for the different support mechanisms. 26a , 26b and 26c Illustrated for the sake of simplicity. However, the correspondence relationship can be used for the different support mechanisms. 26a , 26b and 26c They can differ. The correspondence relationship can be, for example, achieved by grinding a wafer for test processing without any components attached to it on the grinding device. 2 be recorded.
[0036] If the grinding wheel 66 with the workpiece 11 at the clamping table 10 When the workpiece is brought into contact during the grinding feed, it is 11 through the grinding wheel 66 pressed and ground. Since the contact area 13, as described above, directly above the area between the fixed support mechanism 26a and the first movable support mechanism 26b is positioned, is in Fig. 4 loads indicated by A1, which are applied to the fixed support mechanism 26a and the first movable support mechanism 26b is applied, larger than the one in Fig. 4 loads indicated by A2, which are placed on the second movable support mechanism 26c is applied. Consequently, the effect of B1 in Fig. 4. Indicated shortening of the fixed support mechanism 26a and the first movable support mechanism 26b greater than the one caused by B2 in Fig. 4. Indicated shortening of the second movable support mechanism 26c The table base 22 is thus inclined from its state, which is the state directly related to grinding the workpiece 11 through the grinding wheel 6The inclination of the table base changes accordingly. 22 due to the shortening of the support mechanisms 26a , 26b and 26c .
[0037] If the workpiece 11 for example, by the grinding wheel 66 When pressure is applied and grinding is carried out, it is assumed that the fixed support mechanism 26a and the first movable support mechanism 26b in one direction downwards, that is, in one of the Z-axis directions, shortened by 2 µm due to the applied loads, and that the second movable support mechanism 26c The table base is shortened by 1 µm in the same Z-axis direction due to the applied load. In this case, the table base changes. 22 to a first inclined state from its state, which is the state immediately before grinding the workpiece 11 is. If, on the other hand, the fixed support mechanism 26aThe applied load shortens it by 1 µm in the Z-axis direction, and the first movable support mechanism 26b The table base changes when the load applied to it shortens the Z-axis direction by 2 µm. 22 then from its state, which is the state immediately before grinding the workpiece 11 is, to a second inclined state. In this way, the inclination of the table base changes. 22 due to the shortening of the support mechanisms 26a , 26b and 26c different.
[0038] To change the inclination of the table base 22 to examine those that occur while the workpiece 11 As the grinding process progresses, the loads acting on the support mechanisms will be reduced. 26a , 26b and 26c are applied by the load measuring devices 24ameasured. Information regarding the measured loads is provided by the load measuring devices. 24a to a control device 72 sent (see Fig. 1 and Fig. 3A). The control unit 72 is set up as a computer that includes, for example, a processing unit, such as a processor, typically a Central Processing Unit (CPU), a main memory unit, such as a Dynamic Random Access Memory (DRAM), a Static Random Access Memory (SRAM) or a Read Only Memory (ROM), and an auxiliary storage unit, such as a Flash Memory, a hard disk drive or a Solid State Drive.
[0039] The control unit 72 Its functions are realized by operating the processing unit, etc., in accordance with software stored, for example, in the auxiliary storage unit. Part of the auxiliary storage unit serves as a memory. 74to store the corresponding relationship between loads measured by the load measuring devices 24a be recorded, and shortenings of the support mechanisms 26a , 26b and 26c , that is, the correlation relationship between recorded loads and changes in the inclination of the table base 22 The corresponding relationship between the recorded loads and the shortenings of the support mechanisms 26a , 26b and 26c is stored in memory in the form of an equation, a table, or similar 74 saved. The memory 74 Alternatively, it may be provided as a storage medium whose stored information is measured by a non-illustrated measuring unit of the control device. 72 can be read. The storage medium can be a Compact Disc (CD), a Digital Versatile Disc (DVD), a Universal Serial Bus (USB) storage device, a magnetoresistive storage device, or similar.
[0040] The control unit 72 indicates a control 76 for controlling the operating mechanisms etc. of the grinding device 2 up. The control 76 controls the operation of the X-axis movement mechanism 8 , the suction source and the rotary actuator for the clamping table 10 , the tilt adjustment unit 26 , the Z-axis movement mechanism 44 , the servo motor 62 etc. After receiving measurement signals from the load measuring devices 24a , the control system intervenes 76 in a predetermined time sequence to the storage 74 Then the controller reads 76 It extracts shortenings that correspond to the measured loads, or calculates shortenings from the correspondence relationship between loads and shortenings stored in the memory. 74 is stored. After that, the controller controls 76 operation of the stepper motor 32of the first movable support mechanism 26b and the second movable support mechanism 26c the tilt adjustment unit 26 , to the grinding surface 70a and the local area 14b the holding surface 14a to align parallel to each other.
[0041] A grinding process for grinding the workpiece 11 on the grinding device 2 will be discussed below with reference to the Fig. 3A and Fig. 5 to Fig. 8 described. Fig. Figure 8 is a flowchart of a grinding process in accordance with a first embodiment of the present invention. In the grinding process in accordance with the first embodiment, the control system controls 76 , while the holding surface 14a the front 11a of the workpiece 11 which adheres to the tilt adjustment unit 26 , to the grinding surface 70a and the local area14b the holding surface 14a to align parallel to each other (first tilt adjustment step) S10 ).
[0042] After the first tilt adjustment step S10 controls the steering 76 the Z-axis movement mechanism 44 , to the grinding unit 56 to feed downwards for grinding, that is, along one of the Z-axis directions, to the back side 11b of the workpiece 11 with the grinding wheel 66 to sand while the table base 22 as in Fig. 3A illustrates that it is inclined (first grinding step) S20 For example, the control unit rotates 76 the spindle 60 at 4000 rpm around its central axis and the shaft 16 at 300 rpm around its central axis and guides the grinding unit 56in the Z-axis direction at a machining feed rate of 0.2 µm per second for grinding. During the first grinding step S20 grinds the grinding wheel 66 the back 11b of the workpiece 11 , and the load sensing unit 24 captures the table base 22 applied loads. While the grinding continues, the load current of the servo motor remains constant. 62 unchanged, however, the grinding unit 56 on the clamping table 10 Increase the applied load.
[0043] In this case, the grinding stones slide 70 on the back 11b of the workpiece 11 , and although the rotational speed of the spindle 60 If it remains unchanged, the load on the area increases. 13 or the area 13 on. When the load is applied to the contact surface 13increases, compared to the second movable support mechanism 26c a greater load on the fixed support mechanism 26a and the first movable support mechanism 26b applied. Due to the increased load applied, the shortening of the fixed support mechanism occurs. 26a and the first movable support mechanism 26b greater than the shortening of the second movable support mechanism 26c , which causes the tilt of the table base 22 changes in such a way that the grinding surface 70a and the upper surface of the table base 22 , such as in Fig. 5 illustrates that they are parallel to each other. Fig. Figure 5 illustrates a partial sectional view of the clamping table on the side. 10 and other components the way in which the grinding surface 70a and the upper surface of the table base 22 essentially lie parallel to each other.
[0044] If the back 11b of the workpiece 11 continuously sanding while the grinding surface 70a and the upper surface of the table base 22 essentially lying parallel to each other, the thickness of the middle area of the workpiece will be 11 due to the protruding conical shape of the holding surface 14a Reduced too much. An experimental example where the thickness of the middle section of the workpiece 11 The reduction process is described below. Fig. 6A illustrates a cross-sectional profile of the back. 11b of the workpiece ground under a grinding load of 30 N 11 , and Fig. 6B illustrates a cross-sectional profile of the back. 11b of the workpiece ground under a grinding load of 60 N 11 The grinding loads in the Fig. 6A and Fig. 6B represent on the clamping table 10 Loads applied.
[0045] In the Fig. 6A and Fig. Figure 6B shows the horizontal axis radial positions on the workpiece 11 in a cross-sectional plane across the workpiece 11 through its center and the vertical axis the height (µm) of the back. 11b measured by a thickness measuring device of the grinding device 2 The zero point on the vertical axis is at a predetermined height from the holding surface. 14a positioned out. As in Fig. As illustrated in 6A, this is the middle area of the workpiece. 11 Under a grinding load of 30 N, the value is higher than its outer circumference. In accordance with the [reference to be added]. Fig. The cross-sectional profile illustrated in 6A was the difference between the highest and lowest points on the back. 11b 0.94 µm.
[0046] On the other hand, the local area or local region decreases. 14b the holding surface 14adirectly below the contact surface 13 , as in Fig. Figure 6B illustrates the grinding load of 60 N, which affects the middle area of the workpiece. 11 lower than the in Fig. 6A illustrates the height. In accordance with the in Fig. The cross-sectional profile illustrated in 6B was the difference between the highest and lowest points on the back. 11b 0.64 µm. The thickness of the middle section of the workpiece. 11 is therefore reduced, while the load on the holding surface 14a increases. When the thickness of the middle area of the workpiece is reduced. 11 It is assumed that it is caused by the fact that the upper surface of the table base 22 , as in Fig. 5 illustrates, essentially parallel to the grinding surface 70a lies.
[0047] To prevent the thickness of the middle area of the workpiece from increasing 11The locally reduced effect follows the first grinding step in accordance with the present embodiment. S20 an adjustment of the tilt of the table base 22 based on the loads applied during the first grinding step S20 be recorded (second inclination adjustment step) S30 ). In the second tilt adjustment step S30 The controller calculates or reads 76 Shortening of the support mechanisms 26a , 26b and 26c , corresponding to the loads encountered during the first grinding step S20 have been recorded, using the data stored in the memory 74 stored correspondence relationship.
[0048] After that, the control system takes over. 76 the stepper motors 32 , to determine the lengths of the support mechanisms 26a , 26b and 26c to adjust so that the change in the tilt of the table base 22This compensates for the tilt of the table base. 22 adjusted to change the tilt of the table base to that at the time of the first tilt adjustment step S10 to restore. In a case where the fixed support mechanism 26a and the first movable support mechanism 26b for example, the loads applied to it shorten it by 2 µm downwards in the Z-axis direction, and the second movable support mechanism 26c The control system is excited when the load applied to it shortens the Z-axis by 1 µm downwards. 76 the stepper motor 32 the second movable support mechanism 26c , to the second movable support mechanism 26c to contract further downwards by 1 µm in the Z-axis direction.
[0049] In a case where the fixed support mechanism 26aThe load applied to it shortens it by 1 µm downwards in the Z-axis direction, and the first movable support mechanism 26b The control system extends the distance from the Z-axis to the surface by 2 µm due to the applied load. 76 the first movable support mechanism 26b in the Z-axis direction by 1 µm upwards and shortens the second movable support mechanism 26c in the Z-axis direction downwards by 1 µm. During the second tilt adjustment step S30 can the lengths of the first movable support mechanism 26b and the second movable support mechanism 26c in the Z-axis directions while the workpiece 11 is being ground or while the workpiece 11 is not ground or the grinding wheel 66 from the workpiece 11 is spaced apart.
[0050] After the second tilt adjustment step S30will the back 11b of the workpiece 11 ground under the same conditions as those used in the first grinding step S20 , in order to process the workpiece 11 to grind to a predetermined finished thickness (second grinding step) S40 ). Fig. Figure 7 illustrates the way in which the workpiece 11 through the grinding device 2 sanding is carried out after the inclination of the table base has been adjusted. 22 The setting has been adjusted. When the workpiece is ground to the predetermined finished thickness, the material of the workpiece has been adjusted. 11 from its back 11b compared to the state in which it is unpolished, for example by a thickness of 10 µm.
[0051] In accordance with the present embodiment, the inclination of the table base 22adjusted to account for the change in its inclination during the second inclination adjustment step S30 to compensate for the loads that occur during the first grinding step S20 have been recorded. This protects against variations in the thickness of the workpiece. 11 prevented that, compared to a case where the inclination of the table base 22 during the second tilt adjustment step S30 If it is not adjusted, it will not get worse. The correlation relationship between loads measured by the load sensing unit. 24 be recorded, and changes in the inclination of the table base 22 is not based on the correspondence relationship between the loads that act on the support mechanisms 26a , 26b and 26c to be applied, and the shortening of the support mechanisms 26a , 26b and 26climited. Instead, the correlation relationship can, for example, be the correspondence relationship between the loads acting on the support mechanism. 26a , 26b and 26c to be applied, and three-dimensional inclinations of the upper surface of the table base 22 reproduce the three-dimensional inclinations of the upper surface of the table base. 22 can be determined, for example, by a displacement sensor (not illustrated) with a built-in camera that automatically detects the tilt of the table base. 22 detected using an image, a laser distance meter, a contact distance sensor or similar.
[0052] A grinding method in accordance with a second embodiment of the present invention is described below with reference to the Fig. 9A, Fig. 9B and Fig. 10 described. In accordance with the second embodiment, a different workpiece is used. 11, which is derived from a previously ground workpiece 11 differentiates, using the inclination of the table base 22 , which occurs during the second tilt adjustment step S30 has been adjusted in the same way as the ground workpiece 11 ground. In accordance with the second embodiment, in particular the first inclination adjustment step S10 through the second grinding step S40 on the ground workpiece 11 in accordance with the first embodiment, carried out in the manner described. After the second grinding step S40 The ground workpiece is then 11 from the clamping table 10 unloaded.
[0053] Although the lengths of the movable support mechanisms 26b and 26c Stay with it, which is the case during the second tilt adjustment step. S30 to exhibit the set lengths, the front face 11aof the other workpiece 11 under suction effect on the holding surface 14a of the clamping table 10 held. Then the grinding wheel is 66 for grinding with the workpiece 11 brought into contact and grinds the back. 11b of the workpiece 11 (third grinding step) S50 ). Fig. 9A illustrates the way in which the other workpiece 11 through the grinding device 2 is being sanded.
[0054] Since the lengths of the movable support mechanisms 26b and 26c , which occurs during the second tilt adjustment step S30 as they are set, it is in accordance with the second embodiment for the tilt adjustment unit. 26 simple or not necessary, the tilt of the table base 22 during the third grinding step S50 to adjust. During the third grinding stepS50 grinds the grinding wheel 66 the other workpiece 11 , and the load sensing unit 24 captures the table base 22 applied load. If the inclination of the table base 22 deviates from the inclination that was determined in the second inclination adjustment step S30 Once the tilt of the table base has been adjusted, it will be... 22 adjusted (third tilt adjustment step) S60 ).
[0055] If the inclination of the table base 22 not from the second tilt adjustment step S30 If the set inclination has changed, then the third inclination adjustment step can be used. S60 be omitted. In the third tilt adjustment step S60 The correlation relationship between the loads and the changes in the inclination of the table base will also be examined. 22 used. The control 76 activates the tilt adjustment unit 26, in order to base the correlation relationship and the third grinding step S50 The recorded load changes the inclination of the table base 22 to compensate for the load that occurs during the third grinding step S50 The data is recorded and corresponds to the inclination of the table base. 22 to adjust. This prevents variations in the thickness of the workpiece. 11 get worse.
[0056] Fig. 9B illustrates the way in which the inclination of the table base 22 after the third grinding step S50 The adjustment continues. After the third tilt adjustment step S60 will the other workpiece 11 to the same finished thickness as the previously ground workpiece 11 polished. Fig.Figure 10 is a flowchart of the grinding process in accordance with the second embodiment. In accordance with the second embodiment, variations in the thickness of the workpiece are prevented. 11 compared to a case where the tilt of the table base 22 during the third tilt adjustment step S60 will not be hired.
[0057] The structural details of the grinding device 2 The grinding processes described above can be modified or adapted without departing from the scope of protection of the present invention. For example, the number of load measuring devices 24a not necessarily limited to three and can be four or more.
[0058] The present invention is not limited to the details of the preferred embodiments described above. The scope of protection of the invention is defined by the appended claims, and all modifications and adaptations that fall within the equivalent scope of protection of the claims are therefore encompassed by the invention. QUOTES INCLUDED IN THE DESCRIPTION
[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature
[0000] JP 200990389
[0005]
Claims
[1] Grinding device for grinding a workpiece, comprising: a clamping table for holding the workpiece; a plate-shaped table base that supports the clamping table; a grinding unit for grinding the workpiece held on the clamping table with a grinding wheel, wherein the grinding unit has a spindle and the grinding wheel mounted at one end of the spindle; a load detection unit with load measuring devices for detecting a load applied to the table base by the grinding unit; a tilt adjustment unit that supports the table for adjusting the tilt of the table base; a memory for storing a correlation relationship between loads applied to the table base and changes in the inclination of the table base caused by the loads; and a controller which has a processor to control the tilt adjustment unit based on the load detected by the load detection unit and the correlation relationship to adjust the tilt of the table base, so that a change in the tilt of the table base corresponding to the detected load is compensated. [2] Grinding device according to claim 1, wherein the tilt adjustment unit has a fixed support mechanism and several movable support mechanisms, The correlation relationship represents a correlation relationship between loads applied to the fixed support mechanism and the movable support mechanisms, and changes in the inclination of the table base caused by respective shortenings of the fixed support mechanism and the movable support mechanisms on which the loads are applied. The control system adjusts the respective lengths of the movable support mechanisms based on the correlation relationship in order to adjust the inclination of the table base. [3] Grinding process for grinding a workpiece, comprising: a first inclination adjustment step involving the adjustment of an inclination of a table base supporting a clamping table to align parallel a grinding surface defined by respective lower surfaces of grinding stones of a grinding wheel arranged on a surface of a wheel base and lined up along circumferential directions of the surface of the wheel base, and a local surface of a holding surface of the clamping table overlapping a contact surface between the grinding stones and the workpiece held on the clamping table; After the first tilt adjustment step, a first grinding step involves grinding the workpiece with the grinding wheel and capturing a load applied to the table base; after the first grinding step, a second tilt adjustment step with an adjustment of the tilt of the table base to compensate for a change in the tilt of the table base corresponding to the load detected in the first grinding step, based on the correlation relationship between loads applied to the table base and changes in the tilt of the table base caused by the loads and the load detected in the first grinding step; and After the second inclination adjustment step, a second grinding step is performed, grinding the workpiece to a predetermined finished thickness. [4] Grinding method according to claim 3, wherein the correlation relationship represents a correlation relationship between loads applied to a fixed support mechanism and several movable support mechanisms, and changes in the inclination of the table base caused by respective shortenings of the fixed support mechanism and the movable support mechanisms on which the loads are applied, wherein the fixed support mechanism and the several movable support mechanisms are configured to adjust the inclination of the table base, and the second inclination adjustment step comprises a step of adjusting respective lengths of the movable support mechanisms based on the loads applied to the fixed support mechanism and the movable support mechanisms, and the correlation relationship. [5] Grinding method according to claim 4, further comprising: After the second grinding step, a third grinding step is performed by holding a different workpiece, which differs from the workpiece being ground, and grinding the other workpiece with the grinding wheel, while the lengths of the movable support mechanisms continue to have lengths that were set in the second inclination adjustment step. [6] Grinding method according to claim 5, wherein the third grinding step comprises a step involving the detection of a load applied to the table base and the grinding of the other workpiece with the grinding wheel, and wherein the grinding method further comprises a third inclination adjustment step involving the adjustment of the inclination of the table base to compensate for a change in the inclination of the table base corresponding to the load detected in the third grinding step, based on the load detected in the third grinding step and the correlation relationship.