Processing apparatus and wafer manufacturing method
The processing apparatus stabilizes the load center of gravity using load sensors and control units to achieve uniform wafer surface condition and thickness, addressing uneven polishing and prolonged grinding issues.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- DISCO CORP
- Filing Date
- 2024-12-04
- Publication Date
- 2026-06-16
Smart Images
Figure 2026097035000001_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a processing apparatus for processing a wafer and a method for manufacturing a wafer.
Background Art
[0002] As disclosed in Patent Documents 1 and 2, wafer polishing involves bringing a rotating polishing pad into contact with the entire upper surface of the wafer and polishing the upper surface of the rotating wafer. Since the rotation center of the polishing pad is offset from the rotation center of the wafer and the polishing pad is pressed against the wafer with a predetermined load for polishing, an action of tilting the spindle that rotates the polishing pad acts.
[0003] Therefore, depending on the rotation speed of the polishing pad, the rotation speed of the chuck table holding the wafer, the polishing load, or the roughness or shape of the polishing surface of the polishing pad, etc., the position of the center of gravity of the polishing load where the polishing pad is in contact with the wafer moves toward the center side of the wafer, and for example, the central portion of the wafer is polished greatly while the outer peripheral portion is not polished. In such a case, there are problems such as the central portion of the polished surface of the wafer after polishing being in a state of being polished and burned, and the problem that the in-plane thickness of the wafer does not become uniform because the central portion of the wafer is polished greatly and the thickness of the central portion becomes thin.
[0004] In wafer grinding, a grinding wheel is brought into contact with the radius portion of the wafer. That is, since a part of the grinding wheel is in contact with the wafer for grinding, the inclination of the grinding wheel is different between when grinding and when not grinding. Also, depending on conditions such as the grinding feed rate, the rotation speed of the grinding wheel, and the film on the wafer surface, the magnitude of the inclination of the grinding wheel is different.
[0005] Since the inclination of the grinding wheel changes in this way, as disclosed in Patent Documents 3 and 4, before grinding a product wafer, a similar wafer is subjected to trial grinding, and the inclination of the chuck table with respect to the grinding wheel is adjusted so that the wafer subjected to trial grinding has a uniform thickness. However, there is a problem that the trial grinding takes time.
[0006] Furthermore, when the wafer is thick, the grinding feed rate is increased to bring the grinding wheel closer to the wafer for rough grinding, and when the wafer thickness approaches the set thickness, the grinding feed rate is decreased for fine grinding. Due to these differences in at least two grinding feed rates, the inclination of the grinding wheel relative to the chuck table that holds the wafer and the position of the center of gravity of the grinding load are different, which leads to the problem that fine grinding to remove damage marks on the wafer caused by rough grinding takes a long time. [Prior art documents] [Patent Documents]
[0007] [Patent Document 1] Japanese Patent Publication No. 2024-097550 [Patent Document 2] Japanese Patent Publication No. 2023-178694 [Patent Document 3] Japanese Patent Publication No. 2008-264913 [Patent Document 4] Japanese Patent Publication No. 2013-119123 [Overview of the project] [Problems that the invention aims to solve]
[0008] Therefore, in wafer polishing, there is a challenge to be overcome: ensuring uniformity in the surface condition (roughness) and thickness of the polished wafer after the polishing process.
[0009] In wafer grinding, there is a challenge in shortening the grinding time. Another challenge is to detect earlier than before when grinding becomes impossible due to changes in spindle tilt and the center of gravity of the grinding load caused by dulling of the grinding surface of the grinding wheel, and then either temporarily suspend grinding or dress the grinding wheel to resume normal wafer grinding.
[0010] The problems described above in wafer polishing and grinding stem from the fact that the center of gravity of the load applied to the wafer by the rotating workpiece, such as the polishing pad or grinding wheel, changes during processing. Therefore, suppressing the change in the center of gravity of the load while the workpiece is pressed against the wafer is a common challenge in processing, including polishing and grinding. [Means for solving the problem]
[0011] One aspect of the present invention is a processing apparatus comprising: a chuck table that holds a wafer on a holding surface and rotates on a chuck axis passing through the center of the holding surface; a processing mechanism that rotates a spindle fitted with an annular processing tool to process the wafer on the lower surface of the processing tool; and a processing feed mechanism that raises and lowers the processing mechanism, the apparatus comprising: at least three load sensors arranged at equal intervals in a circle centered on the rotation axis of the spindle or the chuck table to measure the force with which the processing tool is pressed against the wafer; and a control unit that controls the rotation speed of the spindle or the rotation speed of the chuck axis so as to maintain a preset ratio between the values of the three load sensors and the processing tool, while pressing the processing tool against the wafer so that the sum of the values of the three load sensors becomes a preset load.
[0012] One aspect of the present invention is a processing apparatus comprising: a chuck table that holds a wafer on a holding surface and rotates on a chuck axis passing through the center of the holding surface; a processing mechanism that rotates a spindle fitted with an annular processing tool to process the wafer on the lower surface of the processing tool; and a processing feed mechanism that raises and lowers the processing mechanism, the apparatus comprising: at least three load sensors arranged at equal intervals in a circle centered on the rotation axis of the spindle or the chuck table to measure the force with which the processing tool is pressed against the wafer; and a control unit that controls the rotation speed of the spindle or the rotation speed of the chuck axis so that the sum of the values of the three load sensors is a preset load, while the processing tool is pressed against the wafer, and the value of at least one of the load sensors is maintained within a preset range.
[0013] In a preferred embodiment, the control unit includes a rotation ratio setting unit for setting the ratio between the rotation speed of the spindle and the rotation speed of the chuck shaft, and the control unit includes maintaining the rotation ratio set in the rotation ratio setting unit.
[0014] The processing tool is, for example, a polishing pad or a grinding wheel.
[0015] As one form of the processing apparatus, the processing mechanism comprises a grinding mechanism equipped with the grinding wheel as the processing tool, and a polishing mechanism equipped with the polishing pad as the processing tool, and includes a turntable that positions one chuck table over the grinding wheel and the polishing pad, with at least two chuck tables.
[0016] One aspect of the present invention is a method for manufacturing a wafer by processing it with the above-described processing apparatus, wherein the processing tool is pressed against the wafer so that the sum of the values of at least three load sensors becomes a preset load, and the rotation speed of the spindle or the rotation speed of the chuck axis is controlled so that the ratio of the values of the three load sensors maintains a preset ratio, thereby processing the wafer held on the holding surface with the processing tool.
[0017] One aspect of the present invention is a method for manufacturing a wafer by processing it with the above-described processing apparatus, wherein the processing tool is pressed against the wafer so that the sum of the values of at least three load sensors becomes a preset load, and the rotation speed of the spindle or the rotation speed of the chuck axis is controlled so that the value of at least one of the load sensors remains within a preset range, thereby processing the wafer held on the holding surface with the processing tool.
[0018] In each embodiment of the wafer manufacturing method, the rotation direction of the spindle and the rotation direction of the chuck shaft are rotated in the same direction. Alternatively, the rotation direction of the spindle and the rotation direction of the chuck shaft are rotated in opposite directions. [Effects of the Invention]
[0019] According to each of the above aspects, it is possible to prevent the change in the position of the center of gravity of the force acting on the wafer from the machining tool. When the machining mechanism is a polishing mechanism, an effect of making the state (roughness) and thickness of the polished surface of the wafer after polishing uniform can be obtained. When the machining mechanism is a grinding mechanism, an effect of shortening the grinding time and an effect of normally grinding the wafer can be obtained.
Brief Description of the Drawings
[0020] [Figure 1] It is a plan view of the processing apparatus. [Figure 2] It is a cross-sectional view of the chuck table and the polishing mechanism. [Figure 3] It is a plan view showing the relationship between the wafer and the polishing pad in the polishing area of the processing apparatus. [Figure 4] In the control of the first form, it is a table showing the values measured by the three load sensors and the normal and abnormal ratios thereof. [Figure 5] In the control of the second form, it is a table showing the values measured by the three load sensors and the normal and abnormal ratios thereof. [Figure 6] In the control of the second form, it is a graph showing a method of controlling so that the value of the load sensor is maintained within a set range.
Embodiments for Carrying Out the Invention
[0021] Hereinafter, the processing apparatus and the method for manufacturing a wafer according to the present embodiment will be described with reference to the drawings. The X-axis direction, Y-axis direction, and Z-axis direction shown in each drawing are in a mutually perpendicular relationship. The X-axis direction and the Y-axis direction are substantially horizontal directions, and the Z-axis direction is the vertical direction.
[0022] The processing apparatus 10 shown in Figure 1 is a device that performs grinding and polishing as processing steps on the wafer W to be processed. Grinding in the processing apparatus 10 is performed in the order of rough grinding and finish grinding, followed by polishing. The processing apparatus 10 is controlled by the control unit 11 and performs a series of processes such as wafer transport, processing, and cleaning on the wafer W fully automatically. The control unit 11 is equipped with a processor and memory, and the processor processes according to the program stored in the memory and controls each part of the processing apparatus 10. The operation of the processing apparatus 10 described below is performed under the control of the control unit 11.
[0023] A turntable 13, which can rotate about an axis in the Z-axis direction, is mounted on the base 12 of the processing apparatus 10. Four chuck tables 14 are supported on the turntable 13 at equal intervals in the direction of rotation of the turntable 13. As shown in Figure 2, the holding surface 141 of the chuck table 14 is conical in shape with the center of rotation as its apex. The inclination angle of the holding surface 141 is very gentle, to the point that it cannot be discerned with the naked eye. The wafer W is held by suction on the holding surface 141 in a state that conforms to the shape of the holding surface 141.
[0024] The turntable 13 is rotated by 90° increments by a turntable rotation mechanism 15 equipped with a motor (not shown), thereby sequentially moving the four chuck tables 14 to the loading / unloading area Ea, the rough grinding area Eb, the finish grinding area Ec, and the polishing area Ed. Each chuck table 14 is rotatably supported by a chuck table support mechanism 32 shown in Figure 2, with a rotation axis passing through the center of the holding surface 141. Details of the chuck table support mechanism 32 will be described later.
[0025] The loading / unloading area Ea is the area where wafers W are loaded into and unloaded from the chuck table 14. The rough grinding area Eb is the area where wafers W held on the chuck table 14 are roughly ground by the rough grinding mechanism 16. The finish grinding area Ec is the area where wafers W held on the chuck table 14 are finish ground by the finish grinding mechanism 17. The polishing area Ed is the area where wafers W held on the chuck table 14 are polished by the polishing mechanism 18. The rough grinding mechanism 16, the finish grinding mechanism 17, and the polishing mechanism 18 constitute the processing mechanism in the processing apparatus 10. The grinding wheel 163 of the rough grinding mechanism 16, the grinding wheel 173 of the finish grinding mechanism 17, and the polishing pad 183 of the polishing mechanism 18 constitute the annular processing tool in the processing apparatus 10.
[0026] Furthermore, the rough grinding mechanism 16 and the finish grinding mechanism 17 may not be separated, and only one grinding mechanism may be provided. In addition, the processing apparatus 10 is equipped with four chuck tables 14 corresponding to the four areas Ea to Ed on the turntable 13 in order to improve work efficiency by loading and unloading wafers W in the loading / unloading area Ea during processing, but the number of chuck tables is not limited to four.
[0027] The base 12 is provided with two cassette stages 19 at its -Y-direction end. One cassette stage 19 holds a cassette 20 containing the wafer W before processing, and the other cassette stage 19 holds a cassette 20 containing the wafer W after processing. The number of cassette stages 19 is not limited to two; there may be one, three or more.
[0028] The wafers W, which are unprocessed and stored in the cassette 20, are removed from the cassette 20 by the transport robot 21 and transported to the alignment mechanism 22. The transport robot 21 includes a robot hand 211 capable of holding and adsorbing the wafers W, a robot arm 212 to which the robot hand 211 is attached, and an X-axis movement unit 213 that moves the robot arm 212 in the X-axis direction. The transport robot 21 transports the wafers W by moving the robot hand 211 through the operation of the robot arm 212 and the X-axis movement unit 213. The alignment mechanism 22 places the wafers W on the alignment table 221 and aligns the wafers W so that the center of the wafers W coincides with the center of the chuck table 14.
[0029] The first transport mechanism 24 transports the wafer W from the alignment mechanism 22 to the chuck table 14 in the loading / unloading area Ea. The first transport mechanism 24 includes a transport pad 241 that holds the upper surface of the wafer W by suction, a lifting unit 242 that moves the transport pad 241 in the Z-axis direction, and a Y-axis moving unit 243 that moves the transport pad 241 in the Y-axis direction. The first transport mechanism 24 holds the upper surface of the wafer W on the alignment table 221 by suction with the transport pad 241, raises the transport pad 241 with the lifting unit 242, moves the transport pad 241 in the +Y direction with the Y-axis moving unit 243, and lowers the transport pad 241 with the lifting unit 242, thereby placing the wafer W on the chuck table 14 in the loading / unloading area Ea.
[0030] When an unprocessed wafer W is held in the chuck table 14 in the loading / unloading area Ea, the turntable 13 is rotated 90 degrees clockwise in Figure 1. This positions the chuck table 14 holding the unprocessed wafer W in the rough grinding area Eb. In the rough grinding area Eb, the rough grinding mechanism 16 is operated to roughly grind the upper surface of the wafer W held in the chuck table 14. The rough grinding mechanism 16 is equipped with a grinding wheel 162 at the lower end of a spindle 161, which is a rotating shaft extending in the Z-axis direction, and a grinding wheel 163 is attached to the lower surface of the grinding wheel 162. The spindle 161 is rotated by a spindle motor. The grinding wheel 163 is arranged in an annular shape on the lower surface near the outer edge of the grinding wheel 162. The rough grinding mechanism 16 moves up and down in the Z-axis direction by the operation of the processing feed mechanism 25.
[0031] As shown in Figure 1, the rough grinding mechanism 16 is positioned such that the grinding wheel 163 passes above the rotation axis Ca of the chuck table 14 (i.e., the rotation axis of the wafer W on the chuck table 14) and the rotation axis Da of the spindle 161 are offset, with the grinding wheel 163 passing above the rotation axis Ca of the chuck table 14. The chuck table support mechanism 32 (Figure 2) rotates the chuck table 14, the spindle motor rotates the spindle 161 and the grinding wheel 162, and the processing feed mechanism 25 lowers the grinding wheel 162. As a result, the wafer W rotates around the rotation axis Ca, the grinding wheel 163 rotates around the rotation axis Da, the lower surface of the grinding wheel 163 is pressed against the upper surface of the wafer W, and the upper surface (workpiece surface) of the wafer W is roughly ground by the grinding wheel 163. During rough grinding, the wafer W on the chuck table 14 rotates in the rotational direction Rc shown in Figure 1, and the grinding wheel 163 rotates in the rotational direction Rd shown in Figure 1. The rotational directions of the wafer W and the grinding wheel 163 on the chuck table 14 are not limited to rotational directions Rc and Rd. They may be in the opposite directions. The control unit 11 controls the processing feed operation of the processing feed mechanism 25 so as to press the grinding wheel 163 against the wafer W with a predetermined force.
[0032] The grinding wheel 163 contacts the wafer W, which is held on the chuck table 14 following the holding surface 141, along an arc-shaped processing line Qa in the radial portion from the contact start point Pa on the outer circumference of the wafer W to the rotation axis Ca of the chuck table 14, thereby rough grinding the wafer W. Once the wafer W has been roughly ground to the desired thickness, the processing feed mechanism 25 is operated to raise the grinding wheel 162, separating the grinding wheel 163 from the upper surface of the wafer W, and rough grinding is completed. As shown in Figure 1, when the wafer W is roughly ground, saw marks M1, which are radial grinding marks along the processing line Qa, are formed.
[0033] Once rough grinding of the wafer W is completed in the rough grinding area Eb, the turntable 13 is rotated 90 degrees clockwise as shown in Figure 1. This positions the chuck table 14, which holds the roughly processed wafer W, in the finish grinding area Ec. In the finish grinding area, the finish grinding mechanism 17 is operated to finish grind the upper surface of the wafer W held in the chuck table 14. Similar to the rough grinding mechanism 16 described above, the finish grinding mechanism 17 is equipped with a grinding wheel 172 at the lower end of a spindle 171, which is a rotating axis extending in the Z-axis direction, and a grinding wheel 173 is attached to the lower surface of the grinding wheel 172. The spindle 171 is rotated by a spindle motor. The grinding wheel 173 is arranged in an annular shape on the lower surface near the outer edge of the grinding wheel 172. The abrasive grains of the grinding wheel 173 have a smaller particle size than the abrasive grains of the grinding wheel 163. The finishing grinding mechanism 17 moves up and down in the Z-axis direction by the operation of the machining feed mechanism 26.
[0034] As shown in Figure 1, the finish grinding mechanism 17 is positioned such that the grinding wheel 173 passes above the rotation axis Cb of the chuck table 14 (i.e., the rotation axis of the wafer W on the chuck table 14) located in the finish grinding region Ec, and the rotation axis Db of the spindle 171 are offset. The chuck table support mechanism 32 (Figure 2) rotates the chuck table 14, the spindle motor rotates the spindle 171 and the grinding wheel 172, and the processing feed mechanism 26 lowers the grinding wheel 172. As a result, the wafer W rotates around its rotation axis Cb, the grinding wheel 173 rotates around its rotation axis Db, and the lower surface of the grinding wheel 173 is pressed against the upper surface of the wafer W, and the upper surface (workpiece surface) of the wafer W is finish-ground by the grinding wheel 173. During finish grinding, the wafer W on the chuck table 14 rotates in the rotational direction Re shown in Figure 1, and the grinding wheel 173 rotates in the rotational direction Rf shown in Figure 1. The rotational directions of the wafer W and the grinding wheel 173 on the chuck table 14 are not limited to rotational directions Re and Rf. They may be in the opposite directions. The control unit 11 controls the processing feed operation of the processing feed mechanism 26 so as to press the grinding wheel 173 against the wafer W with a predetermined force.
[0035] The grinding wheel 173 makes contact with the wafer W, which is held on the chuck table 14 following the holding surface 141, along an arc-shaped processing line Qb in the radial portion from the contact start point Pb on the outer circumference of the wafer W to the rotation axis Cb of the chuck table 14, thereby performing finish grinding on the wafer W. Once the wafer W has been finished grinding to the desired thickness, the processing feed mechanism 26 is operated to raise the grinding wheel 172, separating the grinding wheel 173 from the upper surface of the wafer W, and the finish grinding is completed. As shown in Figure 1, when the wafer W is finished grinding, saw marks M2, which are radial grinding marks along the processing line Qb, are formed.
[0036] Once the finish grinding of the wafer W is completed in the finish grinding area Ec, the turntable 13 is rotated 90 degrees clockwise as shown in Figure 1. This positions the chuck table 14, which holds the finished-ground wafer W, in the polishing area Ed. In the grinding area, the polishing mechanism 18 is operated to polish the upper surface of the wafer W held in the chuck table 14.
[0037] Polishing by the polishing mechanism 18 brings the wafer W to the desired thickness after grinding and removes saw marks M2 formed on the upper surface (polished surface) of the wafer W.
[0038] As shown in Figure 2, the polishing mechanism 18 is equipped with a polishing wheel 182 at the lower end of a spindle 181, which is a rotating shaft extending in the Z-axis direction, and an annular polishing pad 183 is attached to the lower surface of the polishing wheel 182. A circular opening 184 is formed in the center of the polishing pad 183. The spindle 181 is rotated by a spindle motor 185. The polishing mechanism 18 has a slurry supply source 186 that supplies a slurry containing an abrasive. The slurry discharged from the slurry supply source 186 is supplied to the lower side of the polishing wheel 182 through a flow path 187 in the spindle 181 and flows toward the wafer W from the opening 184.
[0039] The polishing mechanism 18 moves up and down in the Z-axis direction by the operation of the machining feed mechanism 27. The machining feed mechanism 27 includes a guide rail 271 and a ball screw 272 extending in the Z-axis direction, and a machining feed motor 273 that rotates the ball screw 272. The lifting and lowering section 274 to which the housing 188 of the polishing mechanism 18 is attached is supported so as to be movable in the Z-axis direction via the guide rail 271, and the ball screw 272 is screwed into the threaded section 275 of the lifting and lowering section 274. When the ball screw 272 rotates due to the drive of the machining feed motor 273, the lifting and lowering section 274 moves in the Z-axis direction together with the polishing mechanism 18.
[0040] Furthermore, the machining feed mechanism 25, which moves the rough grinding mechanism 16 in the Z-axis direction, and the machining feed mechanism 26, which moves the finish grinding mechanism 17 in the Z-axis direction, are each composed of a ball screw mechanism that moves in the Z-axis direction by rotating a ball screw with a motor, similar to the machining feed mechanism 27 shown in Figure 2.
[0041] As shown in Figure 1, the polishing mechanism 18 is positioned with a rotational axis Cc of the chuck table 14 located in the polishing region Ed (i.e., the rotational axis of the wafer W on the chuck table 14) offset from the rotational axis Dc of the spindle 181. The chuck table support mechanism 32 (Figure 2) rotates the chuck table 14, the spindle motor 185 rotates the spindle 181 and the polishing wheel 182, and the processing feed mechanism 27 lowers the polishing wheel 182. As a result, the wafer W and the polishing pad 183 rotate respectively, and the lower surface of the polishing pad 183 is pressed against the upper surface of the wafer W. For example, the wafer W on the chuck table 14 rotates in the rotational direction Ra shown in Figures 1 and 3, and the polishing pad 183 rotates in the rotational direction Rb shown in Figures 1 and 3. The control unit 11 controls the processing feed operation of the processing feed mechanism 27 so as to press the polishing pad 183 against the wafer W with a predetermined force. Furthermore, slurry is supplied from the slurry supply source 186 towards the area where the polishing pad 183 contacts the wafer W. The polishing mechanism 18 polishes the upper surface (surface to be polished) of the wafer W by CMP (Chemical Mechanical Polishing) polishing, which involves the mechanical action of the polishing pad 183 contacting the wafer W and the chemical action of the components contained in the slurry supplied from the slurry supply source 186. The polishing mechanism 18 may also perform dry polishing by the mechanical action of the polishing pad contacting the wafer W without using slurry.
[0042] As shown in Figure 1, the diameters of the polishing wheel 182 and the polishing pad 183 are larger than the diameter of the wafer W, and the polishing wheel 182 is positioned to cover the entire upper surface of the wafer W. The polishing pad 183 polishes the wafer W by pressing it firmly against the processing area Fa that extends radially from the rotation axis Cc to the wafer W, which is held on the chuck table 14 following the holding surface 141, and contacting the entire upper surface of the wafer W with its lower surface (polishing surface). Once the wafer W has been polished to the desired thickness, the processing feed mechanism 27 is operated to raise the polishing wheel 182 and separate the polishing pad 183 from the upper surface of the wafer W.
[0043] Once the polishing of the wafer W is complete in the polishing area Ed, the turntable 13 is rotated 90 degrees clockwise as shown in Figure 1, or 270 degrees counterclockwise. This positions the chuck table 14, which holds the polished wafer W, in the loading / unloading area Ea. In other words, the unprocessed wafer W is loaded onto the chuck table 14 in the loading / unloading area Ea, and then the rotation of the turntable 13 performs rough grinding, finish grinding, and polishing on the wafer W, and the processed wafer W returns to the loading / unloading area Ea.
[0044] The second transport mechanism 28 transports the processed wafer W from the chuck table 14 in the loading / unloading area Ea to the spin cleaning mechanism 29. The second transport mechanism 28 includes a transport pad 281 that holds the upper surface of the wafer W by suction, a swivel unit 282 that rotates the transport pad 281 about an axis in the Z-axis direction, a lifting unit 283 that moves the transport pad 281 in the Z-axis direction, and a Y-axis moving unit 284 that moves the transport pad 281 in the Y-axis direction. The second transport mechanism 28 holds the upper surface of the wafer W on the chuck table 14 located in the loading / unloading area Ea by suction with the transport pad 281, and raises the transport pad 281 with the lifting unit 283 to separate the wafer W from the chuck table 14. The second transport mechanism 28 further rotates the transport pad 281 with the swivel section 282, moves the transport pad 281 in the -Y direction with the Y-axis movement section 284, and lowers the transport pad 281 with the lifting section 283, thereby placing the wafer W onto the spinner table 291 of the spin cleaning mechanism 29.
[0045] The spin cleaning mechanism 29 cleans the wafer W by rotating a spinner table 291 holding the wafer W with a motor, and spraying cleaning water onto the wafer W from a cleaning nozzle 292. After cleaning, air is sprayed onto the wafer W from the cleaning nozzle 292 to dry the wafer W.
[0046] The wafer W, which has been cleaned and dried in the spin cleaning mechanism 29, is held by the transport pad 281 of the second transport mechanism 28 and transported from the spinner table 291 to the alignment table 221 of the alignment mechanism 22. The wafer W, which has been aligned on the alignment table 221, is held by the robot arm 212 of the transport robot 21 and transported from the alignment table 221 to the cassette 20 by the operation of the robot arm 212 and the X-axis movement unit 213, and stored in the cassette 20. Alternatively, the wafer W may be transported from the spin cleaning mechanism 29 to the cassette 20 without going through the alignment mechanism 22 and stored in the cassette 20.
[0047] As described above, the processing apparatus 10 performs a series of processes on the wafer W, including rough grinding, finish grinding, polishing, and cleaning. The unprocessed wafer W removed from the cassette 20 is then subjected to rough grinding, finish grinding, polishing, and cleaning before being stored back in the cassette 20. The series of processes can be performed fully automatically under the control of the control unit 11. The above description describes the processing flow for one wafer W, but the processing apparatus 10 can simultaneously perform at least two processes on multiple wafers W: rough grinding in the rough grinding area Eb, finish grinding in the finish grinding area Ec, and polishing in the polishing area Ed. Furthermore, during these processes, the apparatus can also perform loading and unloading of wafers W to and from the chuck table 14 in the loading / unloading area Ea, and cleaning of wafers W using the spin cleaning mechanism 29.
[0048] Next, the structure of the chuck table 14 and the chuck table support mechanism 32 will be explained with reference to Figure 2. Figure 2 shows the chuck table 14 positioned in the grinding area Ed, but the chuck table 14 and the chuck table support mechanism 32 have the same structure as in Figure 2 in the loading / unloading area Ea, the rough grinding area Eb, and the finish grinding area Ec.
[0049] The chuck table 14 comprises a frame 30 and a disc-shaped porous plate 31 mounted in a recess on the upper side of the frame 30. With the porous plate 31 mounted in the recess of the frame 30, the upper surface of the frame 30 and the upper surface of the porous plate 31 are flush, and the upper surface of the porous plate 31 constitutes a holding surface 141 for holding the wafer W.
[0050] The chuck table support mechanism 32, which rotatably supports the chuck table 14, includes a chuck shaft 35, which is a rotation axis whose axis of rotation passes through the center of the holding surface 141. The chuck shaft 35 is rotatably supported via a bearing 36 inside a support frame 34 supported on the turntable 13. A driven pulley 37 is provided on the outer surface of the chuck shaft 35, and a drive pulley 39 is provided which is rotated by a table drive motor 38. An endless transmission belt 40 is wrapped around the driven pulley 37 and the drive pulley 39. When the drive pulley 39 is rotated by the table drive motor 38, the rotation is transmitted to the driven pulley 37 via the transmission belt 40, causing the chuck shaft 35 to rotate. The frame 30 of the chuck table 14 is detachable from a table base 41 provided at the upper end of the chuck shaft 35, and when the chuck table 14 is attached to the table base 41, the chuck table 14 rotates together with the chuck shaft 35.
[0051] A flow path 42 is formed inside the chuck table 14 and the chuck shaft 35. The flow path 42 communicates with the bottom of the porous plate 31 and extends axially inside the chuck shaft 35 to a rotary joint 43 provided at the lower end of the chuck shaft 35. A suction source 44, an air supply source 45, and a water supply source 46 are connected to the flow path 42 of the rotary joint 43 via on-off valves 441, 451, and 461, respectively.
[0052] When the on-off valve 441 is opened and the suction source 44 is activated, air is drawn from the porous plate 31 through the flow path 42, creating negative pressure on the holding surface 141 and causing the wafer W to be held in place by suction. When the on-off valve 451 is opened and the air supply source 45 is activated, air supplied from the air supply source 45 is sent to the porous plate 31 via the flow path 42, and air is ejected from the holding surface 141. When the on-off valve 461 is opened and the water supply source 46 is activated, water supplied from the water supply source 46 is sent to the porous plate 31 via the flow path 42, and water is ejected from the holding surface 141. When the air supply source 45 and the water supply source 46 are operated simultaneously, a mixture of air and water is ejected from the holding surface 141.
[0053] When loading and holding a wafer W onto the chuck table 14 in the loading / unloading area Ea, the suction source 44 is activated to apply negative pressure to the holding surface 141, thereby holding the wafer W by suction. The wafer W is held by suction on the holding surface 141 throughout the series of processes performed on the wafer W, including rough grinding, finish grinding, and polishing. When the processing of the wafer W is completed and the wafer W is to be unloaded from the chuck table 14 in the loading / unloading area Ea, air, water, or one of the two fluids is ejected from the holding surface 141 to separate the wafer W from the holding surface 141. In addition, by ejecting air, water, or one of the two fluids from the holding surface 141, foreign matter stuck in the pores of the porous plate 31 can be pushed out and removed.
[0054] The processing device 10 is equipped with a notification unit 47 (Figure 1). The notification unit 47 consists of a display monitor, a lamp that lights up or flashes, and a speaker that emits sound, all of which are located on the outside of the processing device 10, and it notifies the operator of the status of the processing device 10. Alternatively, the notification unit may be provided in an external device (such as a personal computer or tablet terminal) that the processing device 10 can communicate with.
[0055] Figure 3 shows the state of the load acting on the wafer W when polishing the wafer W using the polishing mechanism 18 of the processing apparatus 10. When the polishing pad 183 is properly pressed against the wafer W, the polishing pad 183 makes strong contact with the processing region Fa, which has the polishing load centroid Ga as its center of gravity. The polishing load centroid Ga is located approximately half the radius of the wafer W.
[0056] During polishing, the rotation axis Cc of the chuck table 14 (the rotation center Cc of the wafer W) and the rotation axis Dc of the spindle 181 (the rotation center Dc of the polishing pad 183) are offset, and the polishing pad 183 is pressed against the wafer W with a predetermined load. This causes the spindle 181, which rotates the polishing pad 183, to tilt. Therefore, depending on the rotation speed of the spindle 181, the rotation speed of the chuck table 14, and the polishing load set in the polishing processing conditions, the position of the load centroid may shift from the polishing load centroid Ga towards the center of the wafer W. For example, the position of the load centroid where the polishing pad 183 is in contact with the wafer W shifts to the polishing load centroid Gb towards the center of the wafer W, and the processing area Fb becomes the area with the polishing load centroid Gb as its center of gravity. In this case, compared to normal conditions, the central part of the wafer W is polished more extensively, while the outer edge is not polished. This can lead to problems such as the central part of the wafer W becoming discolored after polishing, and the thickness of the wafer W becoming uneven due to the thinner thickness in the central part of the polished wafer W.
[0057] The processing apparatus 10 measures the force with which the processing tool is pressed against the wafer W using a load sensor consisting of a piezoelectric element, and the control unit 11 controls the processing feed mechanism so that the value measured by the load sensor becomes the set polishing load. This prevents the above-mentioned problems and enables accurate and efficient processing of the wafer W. The details are described below.
[0058] The polishing mechanism 18 is equipped with a load sensor 50 that measures the force with which the polishing pad 183 is pressed against the wafer W. As shown in Figure 2, the load sensor 50 is positioned between the flange 189 supporting the spindle unit 180 and the housing 188. As shown in Figure 3, three load sensors 50 are arranged at equal intervals in a circle centered on the rotation axis Dc of the spindle 181. These three load sensors 50 are designated as the first load sensor 501, the second load sensor 502, and the third load sensor 503. The first load sensor 501 and the second load sensor 502 are positioned on either side of the wafer W such that, in the plan view shown in Figure 3, their distances from the rotation axis Cc of the chuck table 14 are approximately equal. The third load sensor 503 is positioned furthest from the rotation axis Cc of the chuck table 14 in the plan view shown in Figure 3. The values measured by each load sensor 50 are transmitted to the control unit 11.
[0059] The polishing mechanism 18 only needs to be equipped with at least three load sensors 50 at equal intervals in a circle centered on the rotation axis Dc of the spindle 181, and may also have four or more load sensors 50.
[0060] As a variation of the arrangement of the load sensors, as shown in Figure 3, at least three load sensors 51 may be arranged at equal intervals in a circle centered on the rotation axis Cc of the chuck table 14. These three load sensors 51 are designated as the first load sensor 511, the second load sensor 512, and the third load sensor 513. The load sensors 51 are arranged, for example, between the frame 30 of the chuck table 14 and the table base 41 of the chuck table support mechanism 32. When the polishing pad 183 is pressed against the wafer W, the load acting on the wafer W on the holding surface 141 of the chuck table 14 can be measured by the load sensors 51. The following explanation uses the case of using the load sensor 50 of the polishing mechanism 18 as an example, but by replacing the description of the load sensor 50 (first load sensor 501, second load sensor 502, third load sensor 503) with the load sensor 51 (first load sensor 511, second load sensor 512, third load sensor 513), it can also be applied when using the load sensor 51 provided on the chuck table 14 side.
[0061] Common to both the first and second forms of control performed by the control unit 11 described below, the control unit 11 controls the lifting speed and direction of the polishing mechanism 18 by the processing feed mechanism 27. When the polishing mechanism 18 polishes the wafer W, the control unit 11 continuously monitors the values measured by the three load sensors 50 while the polishing pad 183 is pressed against the wafer W, and controls the pressing operation of the polishing pad 183 so that the sum of the values from the three load sensors 50 falls within a set load range (e.g., 299N to 301N), including a preset set load (e.g., 300N). For example, in the example shown in the tables of Figures 4 and 5, the sum of the values from the three load sensors 50 under normal conditions is 300.6N.
[0062] As will be explained in more detail later, the rotational speed of the spindle 181 in the polishing mechanism 18 and the rotational speed of the chuck shaft 35 in the chuck table 14 affect the position of the center of gravity of the load that presses the polishing pad 183 against the wafer W. When the position of the center of gravity of the load changes, the ratio of the values of the three load sensors 50 and the value of each load sensor 50 change.
[0063] As mentioned earlier, the position of the center of gravity of the load changes depending on the rotational speed of the spindle 181 or the rotational speed of the chuck shaft 35. Specifically, increasing the rotational speed of the chuck shaft 35 or decreasing the rotational speed of the spindle 181 changes the position of the center of gravity of the load away from the center of the wafer W (third load sensor 503). Conversely, decreasing the rotational speed of the chuck shaft 35 or increasing the rotational speed of the spindle 181 changes the position of the center of gravity of the load closer to the center of the wafer W (third load sensor 503).
[0064] During polishing, the position of the load center of gravity changes (an abnormal condition occurs), so it is necessary to monitor the values of the three load sensors 50 to prevent the load center of gravity from changing. As shown in Figure 3, the polishing load center of gravity Gb during an abnormal condition is shifted to a position closer to the third load sensor 503 (closer to the rotation center Cc of the wafer W) compared to the polishing load center of gravity Ga during a normal condition. Therefore, by controlling the control unit 11 to increase the rotation speed of the chuck shaft 35 or decrease the rotation speed of the spindle 181, the load center of gravity moves away from the center of the wafer W (third load sensor 503), and the polishing load center of gravity Gb during an abnormal condition moves to the polishing load center of gravity Ga during a normal condition.
[0065] Furthermore, the tilt of the spindle 181 is also related to the processing feed speed of the polishing mechanism 18 by the processing feed mechanism 27. In other words, when the processing feed speed of the polishing mechanism 18 by the processing feed mechanism 27 changes, the position of the center of gravity of the load pressing the polishing pad 183 against the wafer W changes. When the processing feed speed that lowers the polishing pad 183 increases, the position of the center of gravity of the load changes in a direction away from the center of the wafer W (third load sensor 503). When the processing feed speed that lowers the polishing pad 183 decreases, the position of the center of gravity of the load changes in a direction closer to the center of the wafer W (third load sensor 503).
[0066] As a first form of load center of gravity adjustment based on this operating principle, the control unit 11 controls the machining feed mechanism 27 so that the sum of the load values measured by the three load sensors 50 falls within the set load range, and also controls the rotational speed of the spindle 181 or the rotational speed of the chuck shaft 35 so that the ratio of the load values measured by the three load sensors 50 maintains a preset ratio.
[0067] The table in Figure 4 shows the load values measured by the first load sensor 501, the second load sensor 502, and the third load sensor 503, and their ratios, for the control of the first embodiment. In the case of a normal polishing load centroid Ga, the values of the first load sensor 501 and the second load sensor 502 are 167.0 N each, and the value of the third load sensor 503 is -33.4 N, and the ratio of the values of these three load sensors 50 is 5:5:-1. The sum of the values of the three load sensors 50 is 300.6 N. This normal load ratio "5:5:-1" is stored in the memory of the control unit 11 as the set ratio.
[0068] In the abnormal case shown in the table in Figure 4 (for example, the center of gravity of the polishing load Gb), the values of the first load sensor 501 and the second load sensor 502 are 165.0 N, and the value of the third load sensor 503 is -30.0 N, with a ratio of 5.5:5.5:-1. The sum of the values of the three load sensors 50 is 300.0 N. Since the ratio of the measured values of the three load sensors 50 (5.5:5.5:-1) differs from the set ratio (5:5:-1) stored in the memory of the control unit 11, the control unit 11 determines that the position of the center of gravity of the load is not normal. Specifically, based on the difference between the ratio of the values measured by the three load sensors 50 and the set ratio, the control unit 11 determines that the center of gravity of the load has moved towards the center of the wafer W (i.e., towards the third load sensor 503) compared to normal conditions, and controls the rotation speed of the chuck shaft 35 to increase, or the rotation speed of the spindle 181 to decrease. As a result, the center of gravity of the load shifts toward the outer edge of the wafer W (i.e., away from the third load sensor 503). The control unit 11 detects that the ratio of the load values of the three load sensors 50 has reached a set ratio, and determines that the center of gravity of the polishing load has reached the normal position Ga (approximately half the radius of the wafer W).
[0069] If the ratio of the load values of the three load sensors 50 deviates from the set ratio, the control unit 11 may notify the operator via the notification unit 47. Notification by the notification unit 47 is performed by displaying information on the display monitor, lighting or flashing a lamp, or emitting a notification sound from a speaker. Upon receiving the notification, the operator may, if necessary, check the condition (roughness) of the surface of the wafer W to be polished, or check and revise the processing conditions in the polishing mechanism 18.
[0070] Thus, in this first form of load center of gravity adjustment, the control unit 11 controls the rotation speed of the spindle 181 or the rotation speed of the chuck shaft 35 so that the ratio of the load values measured by the three load sensors 50 maintains a preset ratio. By continuously performing the above control during polishing, displacement of the load center of gravity can be suppressed, preventing problems such as the central part of the wafer W being polished excessively while the outer edge remains unpolished, and the wafer W not having a uniform thickness.
[0071] Furthermore, regarding the setting ratio of the values of the three load sensors 50, it is also possible to set a range that allows for a width in the ratio of the values of each load sensor 50, for example, (4.9~5.1):(4.9~5.1):(-1~-1.1).
[0072] As a second form of load center of gravity adjustment, the control unit 11 controls the rotational speed of the spindle 181 or the rotational speed of the chuck shaft 35 so that the value of at least one load sensor 50 remains within a preset range. In this second form, the control unit 11 controls the machining feed mechanism 27 so that the sum of the load values measured by the three load sensors 50 falls within the set load range, while also controlling the value of the third load sensor 503 to fall within the set range, or monitoring the value of the third load sensor 503.
[0073] The table in Figure 5 shows the load values measured by the first load sensor 501, the second load sensor 502, and the third load sensor 503, and their ratios, for the second form of control. In the case of the normal polishing load centroid Ga, the values of the first load sensor 501 and the second load sensor 502 are 167.0 N each, and the value of the third load sensor 503 is -33.4 N, with a ratio of 5:5:-1. The sum of the values of the three load sensors 50 is 300.6 N.
[0074] The graph in Figure 6 shows the relationship between the load value measured by the third load sensor 503 and the rotational speed of the spindle 181. The vertical axis in Figure 6 represents the value (load) of the third load sensor 503, and the horizontal axis represents the passage of time. The range of -30.0N to -34.0N shown in the graph in Figure 6 is the load control range of the third load sensor 503 under normal conditions, and this normal load control range "-30.0N to -34.0N" is stored in the memory of the control unit 11 as the set range.
[0075] In the abnormal case shown in the table in Figure 5 (for example, the center of gravity of the polishing load Gb), the load values of the first load sensor 501 and the second load sensor 502 are 167.6N each, and the load value of the third load sensor 503 is -35.2N, with a ratio of 5.0:5.0:-1.05. The combined value of the three load sensors 50 is 300.0N. The control unit 11 monitors only the load value of the third load sensor 503 among the three load sensors 50, and if it falls outside the set range of -30.0N to -34.0N, it determines that the position of the center of gravity of the load is not normal and that the tilt of the spindle 181 has changed. Specifically, as shown in the table in Figure 5, when the load value of the third load sensor 503, -35.2N, falls below the set range (-30.0N to -34.0N), the control unit 11 determines that the center of gravity of the load has moved towards the center of the wafer W (i.e., towards the third load sensor 503) compared to normal conditions, and controls the rotation speed of the chuck shaft 35 to increase or the rotation speed of the spindle 181 to decrease. As a result, the tilt of the spindle 181 decreases, and the center of gravity of the load moves towards the outer circumference of the wafer W (i.e., away from the third load sensor 503). As described above, when the value of the third load sensor 503 increases in the negative direction, the values of the first load sensor 501 and the second load sensor 502 increase in the positive direction to maintain the set polishing load of 300N. Therefore, since the change in the value of the third load sensor 503 is large, in this embodiment the value of the third load sensor 503 is monitored and the change in the tilt of the spindle can be quickly responded to.
[0076] Referring to the graph in Figure 6, the details of the control that maintains the value of the third load sensor 503 within a preset range will be explained. In the graph in Figure 6, the period Ta to Te along the horizontal axis is a period divided by the change in the rotational speed of the spindle 181. The starting point Sa of period Ta indicates the time when the polishing pad 183 is pressed against the upper surface (polished surface) of the wafer W.
[0077] During period Ta, the rotation speed of the spindle 181 is set to a preset polishing speed (for example, 1500 rpm), and the polishing pad 183 is pressed against the wafer W. As the polishing pad 183 is pressed against the wafer W, the value of the third load sensor 503 gradually decreases from the starting point Sa, entering the target set range for polishing (-30.0N to -34.0N). If polishing continues in this state, it approaches the first point Sb. When the value of the third load sensor 503 reaches the first point Sb, the rotation speed of the spindle 181 is increased to, for example, 1800 rpm (period Tb). As a result, the values of the first load sensor 501 and the second load sensor 502 decrease, and the sum of the three load sensors 50 also decreases, so the polishing mechanism 18 is lowered by the processing feed mechanism 27, and the sum of the three load sensors 50 is maintained at 300N. As a result, the value of the third load sensor 503 begins to increase.
[0078] When the value of the third load sensor 503 reaches the upper limit of the set range, -30.0N, at the second point Sc, the control unit 11 reduces the rotation speed of the spindle 181 to, for example, 1500 rpm (period Tc). During period Tc, as the rotation speed of the spindle 181 decreases, the value of the third load sensor 503 begins to decline, and the position of the center of gravity of the load moves to a position at half the radius of the wafer W. If the decrease in the value of the third load sensor 503 is slow, or if it is desired to decrease the value of the third load sensor 503 more quickly, the rotation speed of the spindle 181 may be further reduced (for example, to 1200 rpm).
[0079] When the value of the third load sensor 503 reaches the lower limit of the set range, -34.0N, at the third point Sd, the control unit 11 controls the rotation speed of the spindle 181 to increase (period Td). This prevents the value of the third load sensor 503 from falling outside the set range, as shown in the abnormal load value of -35.2N (in the case of polishing load centroid Gb) in the table of Figure 5. During period Td, the control unit 11 sets the rotation speed of the spindle 181 to 1800 rpm. As a result, the tilt of the spindle 181 decreases, the position of the load centroid moves to a position half the radius of the wafer W, and the value of the third load sensor 503 begins to rise. If the value of the third load sensor 503 does not rise as shown in period Td in Figure 6, or if it is desired to shorten period Td, the control unit 11 controls the rotation speed of the spindle 181 to increase further.
[0080] When the value of the third load sensor 503 reaches the upper limit of the set range, -30.0N, at the fourth point Se, the control unit 11 reduces the rotational speed of the spindle 181 to 1500 rpm (period Te). Similar to period Tc described earlier, in period Te, the value of the third load sensor 503 begins to decline as the rotational speed of the spindle 181 decreases (reaches the set rotational speed). If the value of the third load sensor 503 does not decrease as shown in period Te in Figure 6, or if it is desired to shorten period Te, the control unit 11 controls the rotational speed of the spindle 181 to decrease further.
[0081] When the value of the third load sensor 503 reaches the lower limit of the set range, -34.0N, at the fifth point Sf, the control unit 11 controls the rotation speed of the spindle 181 to increase (period Tf). During period Tf, the rotation speed of the spindle 181 is set to 1800 rpm. As a result, the value of the third load sensor 503 begins to rise.
[0082] As in the embodiment described above, by maintaining the sum of the values of the three load sensors 50 at a set load of 300N and managing the rotation speed of the spindle 181 so that the value of the third load sensor 503 falls within the set range, the load applied to the wafer W and the position of the load's center of gravity can be controlled. Note that a change in the value of the third load sensor 503 as in the embodiment described above means that the inclination of the spindle 181 with respect to the rotation axis of the chuck table 14 is changing.
[0083] If the value of the third load sensor 503 exceeds the set range, the control unit 11 may notify the operator via the notification unit 47. For example, if the value of the third load sensor 503 exceeds the lower limit of the set range (-34.0N) during period Tc, the control unit 11 will have the notification unit 47 provide notification. Notification by the notification unit 47 is provided by displaying information on the display monitor, lighting or flashing a lamp, or emitting a notification sound from a speaker. Upon receiving the notification, the operator may, if necessary, check the condition (roughness) of the surface of the wafer W to be polished, or check and revise the processing conditions in the polishing mechanism 18.
[0084] Thus, in this second form of load center of gravity adjustment, the control unit 11 controls, for example, the rotation speed of the spindle 181 so that the value of the third load sensor 503, which is at least one load sensor 50, is maintained within a preset range. By continuously performing the above control during polishing, the inclination of the spindle 181 is maintained at a predetermined inclination, and the position of the load center of gravity that presses the polishing pad 183 against the wafer W is maintained at the position of the polishing load center of gravity Ga under normal conditions (approximately half the radius of the wafer W), thereby preventing problems such as the central part of the wafer W being polished excessively while the outer periphery remains unpolished, and the wafer W not having a uniform thickness.
[0085] It is preferable to select at least one load sensor 50, which is monitored to ensure that the load value remains within a set range, that exhibits a larger change in load value when the center of gravity of the load acting from the polishing pad 183 to the wafer W changes compared to the other load sensors 50. As shown in the table in Figure 5, the third load sensor 503 exhibits a larger change in load value when the system goes from normal to abnormal compared to the first load sensor 501 and the second load sensor 502. By monitoring the third load sensor 503 and performing the above control, the tilt suppression of the spindle 181 and the movement of the load center of gravity can be managed with high precision.
[0086] Although the graph in Figure 6 shows an example of controlling the rotational speed of the spindle 181, the control unit 11 may also control the rotational speed of the chuck shaft 35 so that the value of the third load sensor 503 remains within a preset range. Furthermore, in controlling the value of the third load sensor 503 to remain within the set range, the control unit 11 may change both the rotational speed of the spindle 181 and the rotational speed of the chuck shaft 35.
[0087] To summarize the control content of the control unit 11 regarding the adjustment of the state in which the polishing pad 183 is pressed against the wafer W for processing, the control unit 11 controls the pressing operation of the polishing mechanism 18 by the polishing mechanism 18 so that the sum of the values of the three load sensors 50 becomes a preset load when the polishing mechanism 18 polishes the wafer W. Furthermore, in the first embodiment, the control unit 11 controls the rotation speed of the spindle 181 or the rotation speed of the chuck shaft 35 so that the ratio of the load values measured by the three load sensors 50 maintains a preset ratio. In the second embodiment, the control unit 11 controls the rotation speed of the spindle 181 or the rotation speed of the chuck shaft 35 so that the value of at least one load sensor 50 (for example, the third load sensor 503) remains within a preset range.
[0088] In the above embodiment, the rotational speed control of the chuck shaft 35 and spindle 181 based on the value of the load sensor 50 is applied to adjusting the position of the load center of gravity when the polishing pad 183 is pressed against the wafer W. However, it can also be applied as a control to manage the tilt of the spindle 181. When reducing the tilt of the spindle 181 from a state where the tilt is large, for example, the control unit 11 controls the rotational speed of the spindle 181 to increase or the rotational speed of the chuck shaft 35 to decrease.
[0089] Conversely, if it is required to increase the tilt of the spindle 181, the control unit 11 controls the rotation speed of the spindle 181 to decrease or the rotation speed of the chuck shaft 35 to increase. For example, this type of control can be selected when intentionally increasing the polishing rate of the central part of the wafer W (setting it to a configuration like the polishing load centroid Gb in Figure 3).
[0090] In both the first and second forms of control, the control unit 11 may change the machining feed rate of the polishing mechanism 18 by the machining feed mechanism 27, independently of changes in the rotational speed of the spindle 181 and the rotational speed of the chuck shaft 35. By increasing the machining feed rate that lowers the polishing pad 183, the effect of reducing the tilt of the spindle 181 can be obtained. Therefore, when changing the polishing load center of gravity Gb in an abnormal state to the polishing load center of gravity Ga in a normal state (changing the position of the load center of gravity in a direction away from the third load sensor 503), control to increase the machining feed rate by the machining feed mechanism 27 can be applied. Also, when intentionally increasing the tilt of the spindle 181, control to decrease the machining feed rate by the machining feed mechanism 27 can be applied.
[0091] In Figure 3, the rotation direction Ra of the wafer W (chuck axis 35) and the rotation direction Rb of the polishing pad 183 (spindle 181) are rotated in the same direction. However, even when the rotation direction of the wafer W (chuck axis 35) and the rotation direction of the polishing pad 183 (spindle 181) are rotated in opposite directions, the control methods of the first and second embodiments described above can be applied.
[0092] The above application examples concern the adjustment of the load center of gravity and the tilt of the spindle 181 when the polishing pad 183 of the polishing mechanism 18 polishes the wafer W. As another application example, the control unit 11 may be made to perform the same control as in the first and second embodiments described above regarding the adjustment of the load center of gravity and the tilt of the spindle 161 when the grinding wheel 163 of the rough grinding mechanism 16 roughly grinds the wafer W, and the adjustment of the load center of gravity and the tilt of the spindle 171 when the grinding wheel 173 of the finish grinding mechanism 17 finish grinds the wafer W. The content of the control when applied to the rough grinding mechanism 16 and the finish grinding mechanism 17 is the same as the content of the control described earlier for the polishing mechanism 18, so a detailed explanation will be omitted and a brief explanation will be given.
[0093] The wafer W is ground by bringing the grinding wheels 163 and 173 into contact with the radial portion of the wafer W (processing lines Qa and Qb shown in Figure 1). Because a portion of the grinding wheels 163 and 173 is in contact with the wafer W during grinding, the inclination of the spindles 161 and 171 that rotate the grinding wheels 163 and 173 changes slightly between grinding and non-grinding states. The magnitude of the inclination of the spindles 161 and 171 relative to the chuck shaft 35 differs depending on conditions such as the rotational speed of the spindles 161 and 171, the rotational speed of the chuck shaft 35, and the processing feed rate provided by the processing feed mechanisms 25 and 26.
[0094] At least three load sensors are placed at equal intervals in a circle centered on the rotational axes Da and Db of the spindles 161 and 171, or the rotational axes Ca and Cb of the chuck table 14 (i.e., the rotational axis of the wafer W on the chuck table 14), and these load sensors are used to measure the force with which the grinding wheels 163 and 173 press against the wafer W.
[0095] In a first configuration, the control unit 11 presses the grinding wheels 163 and 173 against the wafer W so that the sum of the values from the three load sensors becomes a preset load, while controlling the rotational speed of the spindles 161 and 171 or the rotational speed of the chuck shaft 35 so that the ratio of the values from the three load sensors maintains a preset ratio. The control unit 11 may also change the processing feed speed of the grinding wheels 163 and 173 using the processing feed mechanisms 25 and 26.
[0096] In a second embodiment, the control unit 11 presses the grinding wheels 163 and 173 against the wafer W so that the sum of the values from the three load sensors becomes a preset load, while controlling the rotational speed of the spindles 161 and 171 or the rotational speed of the chuck shaft 35 so that the value from at least one load sensor remains within a preset range. The control unit 11 may further change the processing feed speed of the grinding wheels 163 and 173 using the processing feed mechanisms 25 and 26.
[0097] Conventionally, in order to understand the grinding results due to changes in the inclination of the grinding wheels 163 and 173, a similar wafer was test-ground before grinding the wafer W for the product, and the inclination of the chuck table 14 relative to the grinding wheels 163 and 173 was adjusted so that the ground wafer had a uniform thickness. In contrast, in the processing apparatus 10 of this disclosure, the control unit 11 performs the first or second form of control described above (control of the rotational speed of the spindles 161 and 171 or the rotational speed of the chuck shaft 35), making adjustments as needed during grinding to prevent changes in the inclination of the spindles 161 and 171 (grinding wheels 163 and 173), so that the wafer W can be ground to a uniform thickness. As a result, the time required for test grinding is eliminated, and the grinding time can be shortened.
[0098] Furthermore, when the wafer W is thick, the processing feed rate is increased to bring the grinding wheel closer to the wafer W, and the processing feed rate may be decreased when the wafer W becomes thin enough to approach the finish thickness. Conventionally, due to the difference in these at least two processing feed rates, the inclination of the grinding wheels 163 and 173 with respect to the chuck table 14 that holds the wafer W and the position of the center of gravity of the grinding load are different, resulting in the problem that finish grinding to remove damage marks caused by grinding at a high processing feed rate takes a long time. In contrast, in the processing apparatus 10 of this disclosure, the control unit 11 performs the control of the first or second embodiment described above (control of the rotational speed of the spindles 161 and 171 or the rotational speed of the chuck shaft 35), thereby suppressing the change in the inclination of the grinding wheels 163 and 173 due to the difference in processing feed rates of the processing feed mechanisms 25 and 26. As a result, it becomes possible to shorten the time required for finish grinding to remove damage marks.
[0099] Furthermore, due to dulling of the grinding surface (bottom surface) of the grinding wheels 163 and 173, the tilt of the spindles 161 and 171 and the position of the center of gravity of the grinding load may change, making it impossible to grind normally. In the processing apparatus 10 of this disclosure, in the first form of control, if the ratio of the load values of the three load sensors deviates from the set ratio, or in the second form of control, if the value of at least one load sensor exceeds the set range, the control unit 11 may notify the operator via the notification unit 47. By providing such notification, the operator can detect abnormalities such as dulling of the grinding surface of the grinding wheels 163 and 173 earlier than before, and quickly return to a state where the wafer W can be ground normally by temporarily stopping grinding to check the condition of the grinding wheels 163 and 173, or by performing dressing to eliminate the dulling of the grinding wheels 163 and 173.
[0100] The control unit 11 includes a rotation ratio setting unit 111 (Figure 1) that sets the ratio between the rotation speed of the spindles 161 and 171 and the rotation speed of the chuck shaft 35. When performing the first or second form of control described above, the control unit may also perform control to maintain the rotation ratio set in the rotation ratio setting unit 111. In other words, when increasing either the rotation speed of the spindles 161 and 171 or the rotation speed of the chuck shaft 35, the rotation speed of the other is also increased to maintain the rotation ratio. When decreasing either the rotation speed of the spindles 161 and 171 or the rotation speed of the chuck shaft 35, the rotation speed of the other is also decreased to maintain the rotation ratio.
[0101] The shape and number of saw marks M1 and M2 (Figure 1), which are grinding marks when grinding a wafer W, are determined by the ratio of the rotational speed of the spindles 161 and 171 to the rotational speed of the chuck shaft 35. Changes in the shape and number of saw marks M1 and M2 can affect the quality of the device (chip) formed on the wafer W. Therefore, it is necessary to maintain the shape and number of saw marks M1 and M2. By maintaining the ratio of the rotational speed of the spindles 161 and 171 to the rotational speed of the chuck shaft 35 set in the rotational ratio setting unit 111, it is possible to control the tilt of the spindles 161 and 171 and the position of the center of gravity of the grinding load without changing the shape and number of saw marks M1 and M2.
[0102] The position of the center of gravity of the grinding load changes within the trajectory of the grinding wheels along the processing line Qa where the rough grinding wheel (grinding wheel 163) contacts the wafer W, and the processing line Qb where the finish grinding wheel (grinding wheel 173) contacts the wafer W. Under normal conditions, the position of the center of gravity of the grinding load is midway between processing line Qa and processing line Qb.
[0103] In the above embodiment, the processing apparatus 10 performs rough grinding by the rough grinding mechanism 16 and finish grinding by the finish grinding mechanism 17, but it can also be applied to a processing apparatus that performs grinding using only one type of grinding mechanism. Furthermore, the technology disclosed herein may be applied to a single-function processing apparatus that performs either grinding or polishing. In addition, the mechanism for positioning a single chuck table over the grinding wheel and the polishing pad is not limited to a turntable, but may be positioned using, for example, a linear slider.
[0104] Furthermore, the embodiments of the present invention are not limited to the embodiments and modifications described above, and may be modified, substituted, or altered in various ways without departing from the spirit of the technical idea of the present invention. Moreover, if the technical idea of the present invention can be realized in a different way by advances in the art or by other derived arts, it may be implemented by that method. Accordingly, the claims cover all embodiments that may fall within the scope of the technical idea of the present invention. [Industrial applicability]
[0105] By applying the processing apparatus and wafer manufacturing method of the present invention, it is possible to prevent changes in the position of the center of gravity of the force pressing the processing tool against the wafer, thereby improving processing results and shortening processing time in processes such as polishing and grinding. [Explanation of Symbols]
[0106] 10: Processing equipment 11: Control Unit 13: Turntable 14: Chuck Table 16: Rough grinding mechanism (processing mechanism) 17: Finishing grinding mechanism (machining mechanism) 18: Polishing mechanism (processing mechanism) 19: Cassette Stage 20: Cassette 21: Transport robot 22: Alignment mechanism 24: First conveying mechanism 25: Machining feed mechanism 26: Machining feed mechanism 27: Machining feed mechanism 28: Second conveying mechanism 29: Spin cleaning mechanism 32: Chuck table support mechanism 35: Chuck shaft 38: Table drive motor 44: Suction source 45: Air supply source 46 :Water supply source 47: Hochi Department 50: Load sensor 51: Load sensor 111: Rotation ratio setting section 141: Holding surface 161: Spindle 162: Grinding Wheel 163: Grinding wheel (working tool) 171: Spindle 172: Grinding Wheel 173: Grinding wheel (working tool) 181: Spindle 182: Polishing Wheel 183: Polishing pad (working tool) 185: Spindle motor 186: Slurry source 188: Housing 273: Machining feed motor 501: First load sensor 502: Second load sensor 503: Third load sensor 511: First load sensor 512: Second load sensor 513: Third load sensor Ca: Rotation axis of the chuck table Cb: Rotation axis of the chuck table Cc: Rotation axis of the chuck table Da: Spindle rotation axis Db: Spindle rotation axis Dc: Spindle rotation axis Ea: Loading / unloading area Eb:Rough grinding area Ec: Finishing grinding area Ed: Polishing area Fa: Machining area Fb: Machining area Ga: Center of gravity of polishing load under normal conditions Gb: Center of gravity of polishing load under normal conditions M1: Sawmark M2: Sawmark Qa: Processing line Qb: Processing line W: wafer
Claims
1. A processing apparatus comprising: a chuck table that holds a wafer on a holding surface and rotates on a chuck axis passing through the center of the holding surface; a processing mechanism that rotates a spindle fitted with an annular processing tool to process the wafer on the lower surface of the processing tool; and a processing feed mechanism that raises and lowers the processing mechanism, A load sensor is provided, which measures the force applied to the wafer by pressing the workpiece against it, and which is arranged at least three times at equal intervals in a circle centered on the rotation axis of the spindle or the chuck table. The system includes a control unit that presses the workpiece against the wafer so that the sum of the values from the three load sensors becomes a preset load, and controls the rotation speed of the spindle or the rotation speed of the chuck shaft so that the ratio of the values from the three load sensors maintains a preset ratio, Processing equipment.
2. A processing apparatus comprising: a chuck table that holds a wafer on a holding surface and rotates on a chuck axis passing through the center of the holding surface; a processing mechanism that rotates a spindle fitted with an annular processing tool to process the wafer on the lower surface of the processing tool; and a processing feed mechanism that raises and lowers the processing mechanism, A load sensor is provided, which measures the force applied to the wafer by pressing the workpiece against it, and which is arranged at least three times at equal intervals in a circle centered on the rotation axis of the spindle or the chuck table. The system includes a control unit that controls the rotation speed of the spindle or the rotation speed of the chuck axis so that the sum of the values of the three load sensors is a preset set load, while pressing the workpiece against the wafer, and maintaining the value of at least one of the load sensors within a preset set range. Processing equipment.
3. The machining apparatus according to claim 1 or 2, comprising a rotation ratio setting unit for setting the ratio between the rotation speed of the spindle and the rotation speed of the chuck shaft, wherein the control unit maintains the rotation ratio set in the rotation ratio setting unit.
4. The processing device according to claim 1 or 2, wherein the processing tool is an abrasive pad.
5. The processing device according to claim 1 or 2, wherein the processing tool is a grinding wheel.
6. The processing mechanism comprises a grinding mechanism equipped with the grinding wheel as the processing tool, and a polishing mechanism equipped with the polishing pad as the processing tool. The processing apparatus according to claim 1 or 2, comprising a turntable that positions one of the chuck tables on the grinding wheel and the polishing pad, with at least two of the chuck tables arranged thereon.
7. A method for manufacturing a wafer by processing it with the processing apparatus described in claim 1, A method for manufacturing a wafer, comprising pressing the processing tool against the wafer so that the sum of the values of at least three load sensors becomes a preset load, and controlling the rotation speed of the spindle or the rotation speed of the chuck axis so that the ratio of the values of the three load sensors maintains a preset ratio, thereby processing the wafer held on the holding surface with the processing tool.
8. A method for manufacturing a wafer by processing it with the processing apparatus described in claim 2, A method for manufacturing a wafer, comprising pressing the processing tool against the wafer so that the sum of the values of at least three load sensors becomes a preset load, and controlling the rotation speed of the spindle or the chuck axis so that the value of at least one load sensor remains within a preset range, thereby processing the wafer held on the holding surface with the processing tool.
9. A method for manufacturing a wafer according to claim 7 or 8, wherein the rotation direction of the spindle and the rotation direction of the chuck shaft are rotated in the same direction.
10. A method for manufacturing a wafer according to claim 7 or 8, wherein the rotation direction of the spindle and the rotation direction of the chuck shaft are rotated in opposite directions.