Wafer grinding method and wafer manufacturing method

Abstract

To improve thickness accuracy of a ground wafer, in a grinding device having one grinding mechanism.SOLUTION: A wafer grinding method for grinding a wafer (W) held on a chuck table (20) by a grinding wheel (62) includes: a first grinding step of grinding the upper surface of the wafer held by the holding surface (32) of the chuck table with the grinding wheel by a first grinding amount (Kb) less than a predetermined grinding amount (Ka); a separation step of separating the grinding wheel from the upper surface of the wafer, and releasing a load applied to the wafer; and a second grinding step of bringing the grinding wheel into contact with the upper surface of the wafer again, and grinding the wafer by a value obtained by subtracting the first grinding amount from the predetermined grinding amount.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a wafer grinding method and a wafer manufacturing method. [Background technology]

[0002] As disclosed in Patent Documents 1 and 2, both sides of sliced ​​wafers sliced ​​from an ingot by a cutting device such as a wire saw are ground to produce product wafers of a predetermined thickness. In the grinding process performed on sliced ​​wafers, one side of the wafer is ground and then the other side is ground to reduce the wafer to a predetermined thickness while removing slice marks and waviness on each side of the wafer.

[0003] As disclosed in Patent Document 3, a grinding device and a grinding method are known in which, in grinding one side and then the other side of a wafer, after a first grinding is performed by a first grinding mechanism, a turntable is rotated to change the position of a chuck table that holds the wafer, and a second grinding is performed by a second grinding mechanism.

[0004] Furthermore, as disclosed in Patent Document 4, there are cases where a grinding device having a single grinding mechanism is used for grinding one side and the other side of a wafer. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2009-272557 A [Patent Document 2] JP 2006-269761 A [Patent Document 3] JP 2010-069549 A [Patent Document 4] JP 2015-199158 A Summary of the Invention [Problem to be solved by the invention]

[0006] When a wafer is ground by a grinding device, the grinding wheel and the wafer are rotated relative to each other while the grinding wheel is pressed against the wafer, and a load is applied from the grinding wheel to the wafer. When a wafer is ground by a grinding device with a single grinding mechanism, if grinding is performed continuously until a predetermined grinding amount, which is a target value for grinding, is reached and a load is applied to the wafer, a load may be applied to the chuck table that holds the wafer, causing a change in inclination. In this case, the wafer that has been ground to the predetermined grinding amount is affected by the change in inclination of the chuck table, and the amount of grinding by the grinding wheel varies in parts, which is a problem in that it is difficult to grind the wafer to a uniform thickness.

[0007] When the tilt of the chuck table changes, the grinding mechanism to which the grinding wheel is attached may also tilt. The tilt of the grinding mechanism also prevents the wafer from being ground to a uniform thickness.

[0008] When wafers are ground using a grinding device equipped with a first grinding mechanism and a second grinding mechanism, any change in tilt of the chuck table caused by the first grinding by the first grinding mechanism is eliminated while the turntable supporting the chuck table is rotating after the first grinding, and the second grinding by the second grinding mechanism is performed without any change in tilt of the chuck table, making it easy to grind wafers to a uniform thickness.

[0009] Thus, a grinding device with one grinding mechanism has a problem that thickness accuracy is more likely to deteriorate than a grinding device with multiple grinding mechanisms (two or more).On the other hand, a grinding device with multiple grinding mechanisms has problems such as large size, high costs for introduction and operation, and heavy maintenance burden, so the use of a grinding device with one grinding mechanism is often chosen.

[0010] Therefore, there is a problem to be solved, which is to improve the thickness accuracy of ground wafers in a grinding apparatus having a single grinding mechanism. [Means for solving the problem]

[0011] One aspect of the present invention is a wafer grinding method for grinding a wafer held on a chuck table with a grinding wheel, the method comprising: a first grinding step in which the upper surface of the wafer held by the holding surface of the chuck table is ground with the grinding wheel a first grinding amount that is less than a predetermined grinding amount; a separating step in which the grinding wheel is separated from the upper surface of the wafer to release the load on the wafer; and a second grinding step in which the grinding wheel is again brought into contact with the upper surface of the wafer to grind the wafer by the predetermined grinding amount minus the first grinding amount.

[0012] One aspect of the present invention is a method for manufacturing a wafer by grinding both sides of a sliced ​​wafer sliced ​​from an ingot, the method including a protective member forming step of forming a protective member on the entire surface of one side of the wafer, a first holding step of holding the wafer on a chuck table via the protective member, a first grinding step of grinding the other side of the wafer held on the chuck table with a grinding wheel by a first grinding amount that is less than a predetermined grinding amount, a first separating step of moving the grinding wheel away from the other side of the wafer to release a load applied to the wafer, and a second grinding step of grinding the other side of the wafer by the grinding wheel to the predetermined grinding amount. the second grinding step of grinding a second grinding amount which is the grinding amount minus the first grinding amount; a peeling step of peeling the protective member from the one side of the wafer; a second holding step of holding the other side of the wafer on the chuck table; a third grinding step of grinding the one side of the wafer held on the chuck table with the grinding wheel a third grinding amount which is less than a predetermined grinding amount; a second separating step of separating the grinding wheel from the one side of the wafer to release the load applied to the wafer; and a fourth grinding step of grinding the one side of the wafer with the grinding wheel a fourth grinding amount which is the predetermined grinding amount minus the third grinding amount. Effect of the Invention

[0013] According to the wafer grinding method and wafer manufacturing method of the present invention, when the surface of a wafer is ground using a single grinding mechanism, a predetermined grinding amount is ground in multiple steps, and the load applied to the wafer is relieved during the intermediate separation process, thereby improving the thickness accuracy of the ground wafer. [Brief description of the drawings]

[0014] [Figure 1] FIG. [Diagram 2] FIG. 2 is a cross-sectional view of a portion of the grinding device. [Diagram 3] FIG. 11 is a diagram showing the relationship between the change in height position of a grinding wheel and the passage of time when grinding a wafer. [Figure 4] 11A and 11B are diagrams illustrating a sheet supplying step in the protective member forming step. [Diagram 5] 11A and 11B are diagrams illustrating a liquid resin supplying step in the protective member forming step. [Figure 6] 11A and 11B are diagrams illustrating a wafer holding step in the protective member forming step. [Figure 7] 11A and 11B are diagrams illustrating a spreading step in the protective member forming step. [Figure 8] 11A and 11B are diagrams illustrating a curing step in the protective member forming step. [Figure 9] 11A and 11B are diagrams illustrating a sheet cutting step in the protective member forming step. [Figure 10] FIG. 13 is a diagram showing a state in which a protective member forming step is completed. [Figure 11] FIG. 2 is a diagram showing a grinding device which performs a first holding step, a first grinding step, a first separating step and a second grinding step. [Figure 12] FIG. [Figure 13] FIG. [Figure 14] FIG. [Figure 15] 13 is a diagram showing a grinding device which performs a second holding step, a third grinding step, a second separating step, and a fourth grinding step. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] A method for grinding a wafer according to this embodiment will be described with reference to Fig. 1 to Fig. 3. Fig. 1 and Fig. 2 show a grinding apparatus 1 for grinding a wafer W, in which the X-axis direction, the Y-axis direction, and the Z-axis direction are perpendicular to each other. The X-axis direction and the Y-axis direction are substantially horizontal, and the Z-axis direction is a vertical direction.

[0016] The grinding apparatus 1 is an apparatus that grinds a wafer W held on a chuck table 20 with a grinding wheel 62. The wafer W is a semiconductor wafer made of, for example, silicon. The material and type of the wafer W are not limited to these. The wafer W is carried into the grinding apparatus 1 in a state of being accommodated in a cassette C. The inside of the cassette C is formed with a plurality of wafer accommodation sections partitioned in the Z-axis direction, and one cassette C can accommodate a plurality of wafers W.

[0017] The grinding apparatus 1 includes a control unit 2 that is configured with a processor that executes various processes, a memory that stores programs, etc. The grinding apparatus 1 is configured to fully automatically perform a series of operations such as loading, grinding, cleaning, and unloading of the wafer W under the control of the control unit 2.

[0018] As shown in Fig. 1, two cassette stages 11 aligned in the X-axis direction are provided at the end of the -Y direction side of a base 10 of the grinding apparatus 1. A cassette C is placed on each cassette stage 11. The cassette C placed on the cassette stage 11 on the +X direction side contains wafers W before grinding. The cassette C placed on the cassette stage 11 on the -X direction side contains wafers W after grinding.

[0019] A robot hand 12 that puts and takes out a wafer W from the cassette C is provided near each cassette stage 11. A temporary placement table 13 and a cleaning unit 14 are provided within a range in which the robot hand 12 can transport the wafer W. The robot hand 12 can transport the wafer W between the cassette C, the temporary placement table 13, and the cleaning unit 14.

[0020] The temporary placement table 13 is a table on which the wafer W is temporarily placed before being transported to the chuck table 20, and has a holding surface 15 on which the wafer W is placed and held. A plurality of positioning pins 16 that are movable in the radial direction of the temporary placement table 13 are provided around the temporary placement table 13. With the wafer W held on the holding surface 15 of the temporary placement table 13, the plurality of positioning pins 16 are moved so as to abut against the outer periphery of the wafer W, whereby the wafer W is set at a predetermined position relative to the temporary placement table 13.

[0021] The cleaning unit 14 cleans the wafer W after grinding. The cleaning unit 14 includes a spinner cleaning table 17 that can rotate about an axis extending in the Z-axis direction, and a nozzle 18 that sprays cleaning water and dry air toward the spinner cleaning table 17. The spinner cleaning table 17 has a holding surface on which the wafer W is placed and held. The spinner cleaning table 17 is also connected to a suction mechanism (not shown), and the suction mechanism can apply a suction force to the holding surface to suck and hold the wafer W.

[0022] When the wafer W is cleaned in the cleaning unit 14, the spinner cleaning table 17 is rotated with the wafer W held on the holding surface of the spinner cleaning table 17, and cleaning water is sprayed from the nozzle 18 onto the wafer W on the spinner cleaning table 17. After the wafer W is cleaned, dry air is blown onto the wafer W from the nozzle 18 to dry the wafer W.

[0023] Between the temporary placement table 13 and the cleaning unit 14 in the X-axis direction, there are provided a first transport mechanism 21 that transports the unground wafer W from the temporary placement table 13 to the chuck table 20, and a second transport mechanism 22 that transports the ground wafer W from the chuck table 20 to the cleaning unit 14. The first transport mechanism 21 and the second transport mechanism 22 each include a suction pad that suction-holds the upper surface side of the wafer W, and a transport arm that supports the suction pad, and while the wafer W is suction-held by the suction pad, the transport arm is raised and lowered in the Z-axis direction and rotated about an axis extending in the Z-axis direction to transport the wafer W.

[0024] A rectangular opening extending in the Y-axis direction is formed on the upper surface of the base 10, and this opening is covered by a movable plate 23 that can move in the Y-axis direction together with the chuck table 20, and a bellows-shaped waterproof cover 24 provided on both sides of the movable plate 23.

[0025] 2, a structure relating to the support and operation of the chuck table 20 will be described. Inside the base 10, a table moving mechanism 25 that moves the chuck table 20 in the Y-axis direction is provided.

[0026] The table moving mechanism 25 includes a guide rail 26 and a ball screw 27 extending in the Y-axis direction, and a slide portion 28 supporting the chuck table 20 is supported so as to be movable in the Y-axis direction along the guide rail 26. The ball screw 27 is screwed into a screw portion of the slide portion 28, and when the ball screw 27 is rotated by a motor 29 connected to one end of the ball screw 27, the chuck table 20 and the moving plate 23 move in the Y-axis direction together with the slide portion 28. The table moving mechanism 25 can move the chuck table 20 in the Y-axis direction to position the chuck table 20 at a transfer position on the -Y-axis side (a position adjacent to the temporary placement table 13 and the cleaning unit 14) and a processing position on the +Y-axis side (a position adjacent to the grinding mechanism 50 described later).

[0027] The chuck table 20 includes a frame 30 and a disk-shaped porous plate 31 attached in a recess on the upper surface side of the frame 30. The porous plate 31 is made of a porous material such as ceramics, and has fine pores formed all over. With the porous plate 31 attached 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 with each other. The upper surface of the frame 30 and the upper surface of the porous plate 31 form a holding surface 32 on which the wafer W is placed and held.

[0028] The chuck table 20 is formed with a suction passage 33 that communicates with the bottom of the porous plate 31. The suction passage 33 is connected to a suction source 34 via an open / close valve. When the open / close valve is opened to operate the suction source 34, air in the porous plate 31 is sucked through the suction passage 33, and a suction force acts on the holding surface 32. The wafer W can be sucked and held on the holding surface 32 by this suction force.

[0029] The chuck table 20 is configured to be rotatable by a table rotation mechanism 35. A frame 30 of the chuck table 20 is connected to a chuck spindle 36. The chuck spindle 36 is rotatably supported via a bearing disposed inside a cylindrical support base 37. The table rotation mechanism 35 transmits the rotation of an output shaft of a motor (not shown) to the chuck spindle 36 via a transmission member such as a belt, and rotates the chuck table 20 by the rotation of the chuck spindle 36.

[0030] The inclination of the chuck table 20 can be adjusted by the inclination adjustment mechanism 38. The inclination adjustment mechanism 38 includes a position adjustment unit 39 and a fixed support unit (not shown) connected to the slide portion 28 and the support base 37. The position adjustment unit 39 is provided at two or more locations at different positions in the circumferential direction of the support base 37. The fixed support unit supports the support base 37 at a constant height position with respect to the slide portion 28. The two or more position adjustment units 39 can operate individually to change the height position of the support base 37. The inclination adjustment mechanism 38 adjusts the inclination of the chuck table 20 connected to the chuck spindle 36 by operating the position adjustment unit 39 to incline the support base 37 around the fixed support unit as a fulcrum.

[0031] A height detection unit 40 is provided near the chuck table 20. The height detection unit 40 includes two measurement probes, a probe 41 and a probe 42. The probe 41 is provided at a position where it can come into contact with the top surface of the wafer W held on the chuck table 20 and measure the height of the top surface of the wafer W. The probe 42 is provided at a position where it can come into contact with the top surface of the frame 30 that constitutes the holding surface 32 of the porous plate 31 and measure the height of the holding surface 32.

[0032] One of the functional blocks of the control unit 2 is a thickness calculation unit 43. The thickness calculation unit 43 calculates the thickness of the wafer W based on the difference between the height of the top surface of the wafer W measured by the probe 41 and the height of the holding surface 32 measured by the probe 42.

[0033] 1 and 2, a grinding mechanism 50 that grinds the wafer W in the grinding apparatus 1 will be described. The grinding apparatus 1 is a single-axis type grinding apparatus equipped with only one grinding mechanism 50. A column 51 erected on the upper surface of the base 10 is provided with a lifting mechanism 52 that moves the grinding mechanism 50 in a direction (Z-axis direction) to approach and move away from the chuck table 20.

[0034] The lifting mechanism 52 includes a pair of guide rails 53 disposed on the front side of the column 51 and extending in the Z-axis direction, a lifting table 54 supported movably in the Z-axis direction via the pair of guide rails 53, a ball screw 55 extending in the Z-axis direction and screwed into a screwing portion of the lifting table 54, and a motor 56 that rotates the ball screw 55. The drive amount of the motor 56 is detected by the encoder 44.

[0035] When the ball screw 55 is rotated by the drive of the motor 56, the lift table 54 moves in the Z-axis direction. The grinding mechanism 50 is attached to the front surface of the lift table 54 via a housing 57, and the grinding mechanism 50 moves up and down in the Z-axis direction together with the lift table 54. The rotation of the ball screw 55 that lowers the grinding mechanism 50 (moves it in the -Z direction) is defined as the first rotation direction, and the rotation of the ball screw 55 that raises the grinding mechanism 50 (moves it in the +Z direction) is defined as the second rotation direction.

[0036] In the grinding mechanism 50, a grinding wheel 60 is rotatably supported relative to a housing 57, and the grinding wheel 60 is rotationally driven by a spindle unit 58. The spindle unit 58 is, for example, an air spindle, and rotatably supports a spindle shaft 59 via high-pressure air inside the casing. The spindle shaft 59 is an axis extending in the Z-axis direction. A mount 61 is connected to the lower end of the spindle shaft 59, and the grinding wheel 60 is attached to the mount 61. A plurality of grinding stones 62 are arranged in an annular shape on the lower surface of the grinding wheel 60.

[0037] The holding surface 32 of the chuck table 20 is a gentle cone shape with the rotation center of the chuck table 20 as its apex, and the wafer W is held on the chuck table 20 in a cone shape following the holding surface 32. When the chuck table 20 is positioned at the processing position in the Y-axis direction, the center of rotation of the chuck table 20 and the center of rotation of the grinding wheel 60 are shifted so that the grinding wheel 62 passes over the rotation center of the chuck table 20. With this arrangement, when the grinding wheel 60 is rotated, the grinding wheels 62 arranged in an annular shape move along a radial portion extending from the outer periphery of the wafer W held on the chuck table 20 to the rotation center. The tilt adjustment mechanism 38 sets the chuck table 20 at a predetermined tilt so that the grinding wheel 62 abuts against the radial portion of the wafer W.

[0038] With the chuck table 20 set in this manner, the grinding wheel 60 is rotated by the spindle unit 58, the chuck table 20 is rotated by the table rotation mechanism 35, the grinding mechanism 50 is lowered by the lifting mechanism 52, and the lower surface of the grinding wheel 62 is brought into contact with the upper surface of the wafer W held by suction on the holding surface 32 of the chuck table 20, thereby grinding the wafer W with the grinding wheel 62. By rotating the chuck table 20 to change the position of the upper surface of the wafer W that is in contact with the grinding wheel 62, the entire upper surface of the wafer W can be ground with the grinding wheel 62.

[0039] The grinding mechanism 50 includes a grinding fluid supply unit (not shown), and performs grinding while supplying grinding fluid to the portion where the grinding wheel 62 contacts the upper surface of the wafer W. The supplied grinding fluid is used to cool the portion where the wafer W and the grinding wheel 62 contact each other, and to wash away grinding chips generated by grinding.

[0040] A series of steps for grinding the wafer W using the grinding apparatus 1 configured as above will be described. Note that, unless a control entity is specified for the operation of each part of the grinding apparatus 1, the operation is assumed to be controlled by a control signal sent from the control unit 2.

[0041] When a cassette C containing wafers W before grinding is placed on the cassette stage 11, a robot hand 12 removes the wafers W from the cassette C and transports them to the temporary placement table 13, where they are held on the holding surface 15. A plurality of positioning pins 16 are moved toward the center of the temporary placement table 13, and each positioning pin 16 is brought into contact with the outer periphery of the wafer W. By the movement of the positioning pins 16, the position of the wafer W is determined so that the center of the wafer W coincides with the center of the temporary placement table 13.

[0042] Next, the chuck table 20 is positioned at a delivery position on the -Y direction side, and the first transport mechanism 21 transports the wafer W from the temporary placement table 13 to the chuck table 20. The first transport mechanism 21 rotates the transport arm supporting the suction pad while suction-holding the upper surface of the wafer W with the suction pad, to position the suction pad above the chuck table 20. Then, the suction pad is lowered to bring the lower surface of the wafer W close to the holding surface 32 of the chuck table 20.

[0043] The suction source 34 is operated to open the on-off valve, and a suction force is applied to the holding surface 32 of the chuck table 20. When the lower surface of the wafer W is placed on the holding surface 32, the lower surface of the wafer W is held in close contact with the holding surface 32 by the suction force acting on the holding surface 32.

[0044] In this manner, the wafer W transported by the first transport mechanism 21 is delivered to the chuck table 20. The suction force acting on the holding surface 32 causes the entire wafer W to conform to the holding surface 32, preventing the wafer W from floating up from the holding surface 32. The chuck table 20 holding the wafer W by suction is moved in the +Y direction by the table moving mechanism 25, and is positioned at a processing position below the grinding mechanism 50.

[0045] Next, the grinding wheel 60 is rotated by the spindle unit 58, and the grinding mechanism 50 is lowered by the lifting mechanism 52 so that the lower surface of the grinding stone 62 comes into contact with the upper surface of the wafer W. In addition, the table rotation mechanism 35 rotates the chuck table 20, causing the wafer W on the chuck table 20 and the grinding wheel 60 to rotate relatively. In this manner, the upper surface of the wafer W is ground while the grinding stone 62 is pressed against the wafer W.

[0046] When the wafer W has been ground to the desired thickness, the rotation of the grinding wheel 60 is stopped, the grinding mechanism 50 is raised by the lifting mechanism 52, and the grinding stone 62 is moved away from the wafer W on the chuck table 20, thereby completing the grinding process.

[0047] After the grinding process, the table moving mechanism 25 moves the chuck table 20 to a transfer position on the -Y direction side. In addition, the open / close valve is closed to release communication between the suction source 34 and the porous plate 31, so that the suction force is not applied to the wafer W from the holding surface 32 of the chuck table 20. This makes it possible to transfer the wafer W from the chuck table 20 to the second transfer mechanism 22.

[0048] The ground wafer W is transported from the chuck table 20 to the cleaning unit 14 by the second transport mechanism 22. With the upper surface of the wafer W held by the suction pad, the second transport mechanism 22 rotates the transport arm supporting the suction pad to position the suction pad above the spinner cleaning table 17 of the cleaning unit 14. Then, the suction pad is lowered to place the lower surface of the wafer W on the spinner cleaning table 17. A suction force is applied to the holding surface of the spinner cleaning table 17 by a suction mechanism (not shown) provided in the cleaning unit 14, causing the spinner cleaning table 17 to hold the lower surface of the wafer W by suction.

[0049] In this manner, when the wafer W transported by the second transport mechanism 22 is delivered to the spinner cleaning table 17, the wafer W is cleaned in the cleaning section 14. The spinner cleaning table 17 holding the wafer W is rotated, and cleaning water is sprayed from the nozzle 18 onto the wafer W on the spinner cleaning table 17. Air is sprayed from the nozzle 18 onto the cleaned wafer W to dry it.

[0050] Subsequently, the cleaned wafer W is carried out from the cleaning section 14 by the robot hand 12 and stored in the cassette C. Alternatively, the cleaned wafer W may be carried to the temporary placement table 13 and positioned using the positioning pins 16 before being stored in the cassette C.

[0051] Incidentally, when the chuck table 20 is positioned at a specific processing position and the wafer W is ground by a single grinding mechanism 50, as in the grinding apparatus 1, the wafer W that has been ground to a target thickness by continuously applying a load from the grinding wheel 62 is affected by the change in inclination of the chuck table 20 due to the load, and there is a problem that it is difficult to grind the wafer W to a uniform thickness.

[0052] The tilt of the chuck table 20 can be adjusted by the tilt adjustment mechanism 38. If the load from the grinding wheel 62 continues to be applied to the wafer W during grinding of the wafer W, the load may cause a load on the chuck table 20 and its support structure (such as the tilt adjustment mechanism 38), which may cause a change in tilt of the chuck table 20. If the tilt of the chuck table 20 changes, the grinding wheel 62 may come into contact with the upper surface of the wafer W held on the holding surface 32 of the chuck table 20 unevenly, and the amount of grinding of the wafer W in each radial region becomes non-uniform. In addition, when the tilt of the chuck table 20 changes, the grinding mechanism 50 to which the grinding wheel 62 is attached may also become tilted. If the grinding mechanism 50 becomes tilted, the amount of grinding of the wafer W in each radial region becomes non-uniform.

[0053] The wafer grinding method according to this embodiment solves the above problems in a grinding apparatus 1 having a single grinding mechanism 50, and improves the thickness accuracy of the ground wafer W, and details thereof will be described below. FIG. 3 is a diagram showing an example of an operation performed by the grinding apparatus 1 in the wafer grinding method according to this embodiment. The vertical axis in FIG. 3 indicates the height position of the grinding wheel 62 in the Z-axis direction, and the horizontal axis indicates the passage of time. A predetermined grinding amount of the upper surface of the wafer W for grinding the wafer W to a target thickness by the grinding apparatus 1 is set as a target grinding amount Ka.

[0054] 3, the grinding process of the wafer W is composed of eight steps divided into eight periods from period TA to period TH. The eight steps are roughly divided into a grinding preparation step carried out in periods TA and TB, a grinding process carried out in periods TC and TE, a separation step carried out in period TD during the grinding process, and a grinding completion step carried out in periods TF, TG, and TH.

[0055] The first step is an initial lowering step in which the grinding mechanism 50, which is in a standby position above the wafer W, is lowered at high speed to move the lower surface of the grinding wheel 62 to the air-cut start position, and is performed during a period TA. The control unit 2 drives the motor 56 of the lifting mechanism 52 to rotate the ball screw 55 in a first rotation direction, and lowers the grinding mechanism 50 at a constant speed VA to near the air-cut start position. The speed VA at which the grinding mechanism 50 descends in the initial lowering step is greater than the speed VB of the lowering in the air-cut step described below and the speeds VC and VE of the lowering in the grinding step, and the high speed lowering of the grinding mechanism 50 allows the grinding wheel 62 to quickly approach the wafer W.

[0056] The end of the initial lowering process can be identified by various methods. For example, the drive amount of the motor 56 corresponding to the lowering amount of the grinding mechanism 50 in the initial lowering process is stored in advance in the memory of the control unit 2, and when the drive amount of the motor 56 detected by the encoder 44 reaches the stored value, it can be determined that the initial lowering process has ended. Alternatively, the elapsed time from the start of the initial lowering process can be counted, and when a preset predetermined time has elapsed, it can be determined that the initial lowering process has ended.

[0057] The second step is an air-cut step, which is performed during the period TB. In the air-cut step, the control unit 2 lowers the grinding mechanism 50 by the lifting mechanism 52 at a speed VB slower than the speed VA in the previous period TA, and moves the grinding mechanism 50 to a position where the lower surface of the grinding wheel 62 abuts on the upper surface of the wafer W. In detail, the control unit 2 controls the motor 56 of the lifting mechanism 52 so as to reduce the rotation speed of the ball screw 55 in the first rotation direction to be lower than that in the initial lowering step, thereby lowering the grinding mechanism 50. By lowering the speed of the lowering of the grinding mechanism 50 in the air-cut step, it is possible to prevent the grinding wheel 62 from colliding with the wafer W with force and damaging the wafer W. In the grinding preparation step from the period TA to the period TB, the grinding wheel 62 is not abutting on the wafer W, and the wafer W is not ground.

[0058] Various methods can be adopted to specify the end of the air cutting process, that is, the state in which the lower surface of the grinding wheel 62 abuts against the wafer W. For example, the grinding mechanism 50 is provided with a load sensor capable of detecting the load in the Z-axis direction applied to the grinding wheel 60 or the like, and the load sensor can detect the change in the load when the lower surface of the grinding wheel 62 abuts against the upper surface of the wafer W. Alternatively, the driving amount of the motor 56 corresponding to the lowering amount of the grinding mechanism 50 in the air cutting process is stored in advance in the memory of the control unit 2, and when the driving amount of the motor 56 detected by the encoder 44 reaches the stored value, it can be determined that the air cutting process has ended. Alternatively, the elapsed time from the start of the air cutting process is counted, and when a preset predetermined time has elapsed, it can be determined that the air cutting process has ended. Alternatively, a non-contact thermometer capable of measuring the temperature near the portion where the grinding wheel 62 and the wafer W abut against each other is provided, and when a rise in temperature resulting from friction between the grinding wheel 62 and the wafer W is detected, it can be determined that the air cutting process has ended.

[0059] The third step is a first grinding step, which is performed during a period TC. In the first grinding step, the upper surface of the wafer W held by the holding surface 32 of the chuck table 20 is ground by a first grinding amount Kb, which is less than a target grinding amount Ka (predetermined grinding amount), using a grinding wheel 62. In other words, the first grinding step is performed under the condition that the target grinding amount Ka>the first grinding amount Kb.

[0060] When the control unit 2 detects the end of the air cutting step (a state in which the lower surface of the grinding wheel 62 abuts against the upper surface of the wafer W), it executes the operation of the first grinding step. In the first grinding step, the control unit 2 causes the lifting mechanism 52 to lower the grinding mechanism 50 at a constant speed VC, while rotating the chuck table 20 with the table rotation mechanism 35 and rotating the grinding wheel 60 with the spindle unit 58, so that the upper surface of the wafer W is ground by the grinding wheel 62. The speed VC of descent of the grinding mechanism 50 in the first grinding step may be the same as the speed VB of descent of the grinding mechanism 50 in the air cutting step, or may be a speed different from the speed VB.

[0061] The control unit 2 measures the thickness of the wafer W using the height detection unit 40, and causes the grinding mechanism 50 to grind the upper surface of the wafer W until the thickness of the wafer W reaches the thickness of the wafer W before the start of the first grinding process minus the first grinding amount Kb.

[0062] The fourth step is a separation step, which is performed during the period TD. In the separation step, the grinding wheel 62 is separated from the upper surface of the wafer W to release the load applied to the wafer W.

[0063] When the control unit 2 detects by the height detection unit 40 that the grinding amount of the wafer W reaches the first grinding amount Kb in the first grinding step, it executes the operation of the separating step. More specifically, the control unit 2 controls the motor 56 of the lifting mechanism 52 to change the rotation of the ball screw 55 from the first rotation direction to the second rotation direction. Then, the grinding mechanism 50 rises at a speed VDa, and the grinding wheel 62 separates from the upper surface of the wafer W. This operation of separating the grinding wheel 62 from the wafer W releases the load applied to the wafer W from the grinding mechanism 50, and suppresses changes in the inclination of the chuck table 20 that holds the wafer W.

[0064] In the separating step, the control unit 2 controls the length of time that the grinding wheel 62 is separated from the wafer W so as to reliably release the load applied to the wafer W and the chuck table 20. As an example, in a grinding device equipped with a plurality of grinding mechanisms, the grinding wheel 62 is maintained separated from the wafer W for a time equal to or longer than the time required to move the chuck table from a grinding position by one grinding mechanism to a grinding position by the next grinding mechanism.

[0065] After the grinding wheel 62 is separated from the upper surface of the wafer W, the control unit 2 controls the motor 56 of the lifting mechanism 52 to change the rotation of the ball screw 55 from the second rotation direction to the first rotation direction. Then, the grinding mechanism 50 descends at a speed VDb, and the grinding wheel 62 approaches the wafer W. The control unit 2 descends the grinding mechanism 50 at the speed VDb until the grinding wheel 62 abuts against the upper surface of the wafer W again.

[0066] 3, in the separating step, the grinding wheel 62 is raised to a position higher than the position of the grinding wheel 62 at the start of the first grinding step. By raising the grinding wheel 62 to this position, a sufficiently long time is ensured before the grinding wheel 62 is lowered and brought into contact with the upper surface of the wafer W again, and the load on the wafer W can be reliably released.

[0067] The distance by which the grinding wheel 62 is separated from the wafer W in the separating step is not limited to the example in Fig. 3, and can be selected arbitrarily. Since the load applied to the wafer W can be released when the contact of the grinding wheel 62 with at least the upper surface of the wafer W is released, the amount of separation of the grinding wheel 62 from the wafer W may be set smaller than that in the example in Fig. 3. In this case, in order to ensure the length of time that the grinding wheel 62 is separated from the wafer W, the rotation of the ball screw 55 of the lifting mechanism 52 may be stopped after separation, and the height of the grinding wheel 62 may be controlled to be kept constant for a predetermined time.

[0068] In addition, the speed VDa at which the grinding mechanism 50 ascends and the speed VDb at which it descends in the separating step can also be selected arbitrarily. When the distance by which the grinding wheel 62 is separated upward from the wafer W is constant, the period TD becomes longer when the speed VDa or the speed VDb is slowed down, and the period TD becomes shorter when the speed VDa or the speed VDb is fasted down.

[0069] 3, the speed VDa of the grinding mechanism 50 when it ascends and the speed VDb of the grinding mechanism 50 when it descends in the separating step are substantially the same in terms of positive and negative relationship, but the speeds VDa and VDb may be different. For example, in the separating step, the grinding mechanism 50 may be raised at high speed to quickly separate the grinding wheel 62 from the wafer W, and the grinding mechanism 50 may then be lowered at a low speed to reduce the impact when the grinding wheel 62 comes into contact with the wafer W again. Also, the speed VDa of the grinding mechanism 50 when it ascends and the speed VDb of the grinding mechanism 50 when it descends may change midway.

[0070] In this manner, in the separating step, by appropriately setting the distance by which the grinding wheel 62 is separated from the wafer W, and the ascending speed VDa and descending speed VDb, it is possible to optimize the length of the separating step and the ascending and descending operation of the grinding wheel 62. Therefore, the operation of the separating step shown in Fig. 3 is one example, and the operation of the grinding mechanism 50 may be performed in a form other than this one example.

[0071] The fifth step is a second grinding step, which is performed during a period TE. In the second grinding step, the grinding wheel 62 is again brought into contact with the upper surface of the wafer W held by the holding surface 32 of the chuck table 20, and the second grinding amount Kc, which is the target grinding amount Ka-the first grinding amount Kb, is ground by the grinding wheel 62.

[0072] The control unit 2 executes the operation of the second grinding process when it detects that the lower surface of the grinding wheel 62 has come into contact with the upper surface of the wafer W again in the final stage of the separating process. As a method for identifying the state in which the lower surface of the grinding wheel 62 has come into contact with the wafer W again, various methods can be adopted, similar to the method for identifying the end of the air cutting process described above.

[0073] In the second grinding step, the control unit 2 causes the lifting mechanism 52 to lower the grinding mechanism 50 at a constant speed VE, while rotating the chuck table 20 with the table rotation mechanism 35 and rotating the grinding wheel 60 with the spindle unit 58, thereby grinding the wafer W with the grinding stone 62. The speed VE of descent of the grinding mechanism 50 in the second grinding step may be the same as the speed VC of descent of the grinding mechanism 50 in the first grinding step, or may be different from the speed VC.

[0074] The control unit 2 measures the thickness of the wafer W using the height detection unit 40, and causes the grinding mechanism 50 to grind the wafer W until the thickness of the wafer W before the start of the second grinding process is reduced by the second grinding amount Kc. In other words, the control unit 2 causes the grinding of the wafer W in the second grinding process to be performed until the thickness of the wafer W before grinding (before the start of the first grinding process) is reduced by the target grinding amount Ka.

[0075] Therefore, when the process goes from the first grinding process through the separation process to the second grinding process, the sum of the first grinding amount Kb in the first grinding process and the second grinding amount Kc in the second grinding process results in grinding of a predetermined grinding amount, that is, a target grinding amount Ka, and the wafer W reaches the target thickness.

[0076] The sixth step is a spark-out step, which is performed during the period TF. When the control unit 2 detects the end of the second grinding step (a state in which the wafer W has reached the target thickness through the first grinding and the second grinding), it stops driving the motor 56 of the lifting mechanism 52, and causes the grinding mechanism 50 to maintain a constant position in the Z-axis direction without further lowering. In other words, it sets the speed VF to 0. The control unit 2 continues the rotation of the grinding wheel 60 by the spindle unit 58 and the rotation of the chuck table 20 by the table rotation mechanism 35. As a result, the grinding wheel 62 rubs the upper surface of the wafer W without applying a load pressing it in the Z-axis direction, making the grinding marks remaining on the upper surface of the wafer W less noticeable.

[0077] The length of the spark-out process can be set arbitrarily. For example, the time elapsed from the start of the spark-out process can be counted, and it can be determined that the spark-out process has ended when a preset time has elapsed. Alternatively, a non-contact thermometer capable of measuring the temperature in the vicinity of the contact area between the grinding wheel 62 and the wafer W can be provided, and the end of the spark-out process can be determined when the temperature, which has risen in the second grinding process, drops in the spark-out process, and becomes equal to or lower than a preset temperature.

[0078] The seventh step is an escape cut step, which is performed during the period TG. When the control unit 2 detects the end of the spark-out step, it controls the motor 56 of the lifting mechanism 52 to rotate the ball screw 55 in the second rotation direction. Then, the grinding mechanism 50 rises at a speed VG, and the grinding wheel 62 moves away from the upper surface of the wafer W. Even while the grinding mechanism 50 is rising, deformation due to the load remaining on the wafer W is released, and the grinding wheel 62 may come into contact with the wafer W to continue grinding. Therefore, the control unit 2 raises the grinding mechanism 50 at a low speed VG to separate the grinding wheel 62 from the wafer W without applying a load or impact to the wafer W.

[0079] The eighth step is a final lifting step in which the grinding mechanism 50 is moved to the standby position at high speed, and is performed during the period TH. When the escape cut step is completed, the control unit 2 controls the driving of the motor 56 of the lifting mechanism 52 to rotate the ball screw 55 in the second rotation direction at a speed faster than that in the escape cut step. Then, the lifting mechanism 52 lifts the grinding mechanism 50 at a speed VH faster than the speed VG at which the grinding mechanism 50 was lifted in the escape cut step. When the grinding mechanism 50 reaches the standby position, the control unit 2 stops the motor 56 of the lifting mechanism 52.

[0080] The end of the escape cut process and the final ascent process can be determined by various methods. For example, the drive amount of the motor 56 corresponding to the elevation amount of the grinding mechanism 50 in the escape cut process and the final ascent process can be stored in advance in the memory of the control unit 2, and when the drive amount of the motor 56 detected by the encoder 44 reaches the stored value, it can be determined that the escape cut process or the final ascent process has ended. Alternatively, the elapsed time from the start of the escape cut process and the final ascent process can be counted, and when a preset predetermined time has elapsed, it can be determined that the escape cut process or the final ascent process has ended.

[0081] In addition, instead of the encoder 44 associated with the motor 56 of the lifting mechanism 52 or a load sensor that detects the load applied to the grinding mechanism 50, it is also possible to provide a height detection sensor that directly detects the height position of the grinding mechanism 50, and control the operation of the lifting mechanism 52 in each of the above-mentioned processes based on the detection results of the height detection sensor.

[0082] As described above, according to the wafer grinding method of this embodiment, when a predetermined grinding amount (target grinding amount Ka) is ground on the upper surface of the wafer W by one grinding mechanism 50, the grinding is divided into two grinding amounts (first grinding amount Kb and second grinding amount Kc) smaller than the predetermined grinding amount, and a separation step is performed between the first grinding step and the second grinding step to release the load on the wafer W. This prevents the load from being continuously applied to the wafer W, suppresses changes in the inclination of the chuck table 20 caused by the continuous load, and improves the thickness accuracy of the wafer W after grinding.

[0083] When the first grinding step and the second grinding step are performed, it is preferable that the first grinding amount Kb of the wafer W in the first grinding step is larger than the second grinding amount Kc of the wafer W in the second grinding step. As an example, when the target grinding amount Ka is 50 μm, the first grinding amount Kb is 40 μm and the second grinding amount Kc is 10 μm.

[0084] In the above embodiment, two grinding steps (first grinding step and second grinding step) are performed on the upper surface of the wafer W with one separating step in between, but the number of grinding steps to be performed in a divided manner is not limited to two, and three or more grinding steps may be performed with two or more separating steps in between. In other words, the above embodiment is an example showing a case where the number of grinding steps (two) and separating steps (one) when grinding the upper surface of the wafer W is minimum, and the number of grinding steps and the number of separating steps are not limited to this example. When grinding a predetermined grinding amount, by increasing the number of separating steps to increase the frequency of dividing the grinding steps, it becomes easier to suppress the change in the inclination of the chuck table 20 in each grinding step. On the other hand, the more the number of separating steps is, the longer the time required to complete grinding of the predetermined grinding amount. Therefore, it is preferable to set an appropriate number of grinding steps and separating steps in consideration of the balance between the improvement of the thickness accuracy of the ground wafer W and the efficiency of the grinding process.

[0085] Unlike the grinding device 1 of the above embodiment, a grinding device is known that has a configuration in which a plurality of grinding mechanisms with grinding stones having different roughness are provided, and the first grinding mechanism performs rough grinding on the upper surface of the wafer W, and the second grinding mechanism performs finish grinding on the upper surface of the wafer W. In such a grinding device, in the grinding by the first grinding mechanism and the grinding by the second grinding mechanism, it is also possible to apply a grinding process divided into a plurality of steps including a separation step, as in the above embodiment. In particular, it is preferable to apply a grinding process divided into a plurality of steps including a separation step to the grinding mechanism that is more likely to cause a change in the inclination of the chuck table before a predetermined grinding amount is reached, between the first grinding mechanism and the second grinding mechanism.

[0086] The above embodiment of the wafer grinding method described with reference to Figures 1 to 3 is directed to the case where one of the two sides of the wafer W (the upper surface facing upward when held on the chuck table 20) is ground, but it can also be applied to the case where both sides of the wafer W are ground.

[0087] In the embodiment of the wafer manufacturing method shown in Figs. 4 to 15, both sides of the wafer W are ground in the same manner as in the above embodiment to manufacture the wafer W. The wafer manufacturing method of this embodiment is applied to the case where the wafer W is manufactured by grinding both sides of a sliced ​​wafer sliced ​​from an ingot using a wire saw or the like. The wafer W has one side Wa and the other side Wb on the front and back sides. Note that the operation of grinding one side Wa of the wafer W and the operation of grinding the other side Wb are performed in the same manner as the operation described in Fig. 3 of the above embodiment, so the explanation of each grinding step will be made with reference to Fig. 3.

[0088] The wafer manufacturing method of this embodiment is performed in the following order: protective member forming step, first holding step, first grinding step, first separating step, second grinding step, peeling step, second holding step, third grinding step, second separating step, and fourth grinding step. The protective member forming step is performed by a protective member forming device 3, the peeling step is performed by a peeling device 5, and the other steps are performed by a grinding device 4. The grinding device 4 grinds both sides of the wafer W with one grinding mechanism 92, grinds the other side Wb in the first grinding step and the second grinding step, and grinds one side Wa in the third grinding step and the fourth grinding step.

[0089] The protective member forming device 3, the grinding device 4, and the peeling device 5 may be independent devices, or may be configured as sections of a single integrated processing device. The operation of each part in each process described below is performed under the control of a control unit (not shown) provided in the protective member forming device 3, the grinding device 4, and the peeling device 5.

[0090] [Protective material formation process] In the protective member forming process shown in Figures 4 to 10, a protective member H is formed over the entire surface of one side Wa of a wafer W. The protective member forming process includes a sheet supplying process (Figure 4), a liquid resin supplying process (Figure 5), a wafer holding process (Figure 6), a spreading process (Figure 7), a curing process (Figure 8), and a sheet cutting process (Figure 9), and the state of the protective member H that is completed through each of these processes is shown in Figure 10.

[0091] 4, a light-transmitting sheet S is placed on the upper surface of a transparent table 70 provided in the protective member forming apparatus 3. The sheet S is gripped by a sheet gripper 69 and pulled out onto the table 70. The area of ​​the sheet S placed on the table 70 is larger than the area of ​​the wafer W.

[0092] The table 70 is supported by a box-shaped table support stage 71 that is open at the top. An ultraviolet ray irradiation unit 72 is provided below the table 70 inside the table support stage 71. The ultraviolet ray irradiation unit 72 is composed of a plurality of lamps or LEDs that irradiate the table 70 with ultraviolet ray UV (FIG. 8).

[0093] In the liquid resin supplying step shown in FIG. 5, an ultraviolet-curable liquid resin L is supplied from a supply nozzle 73 positioned above a table 70 toward the center of a sheet S on the table 70.

[0094] In the wafer holding process shown in FIG. 6, the other side Wb of the wafer W is suction-held on the lower surface of the holding pad 75, and the holding pad 75 is moved to above the table 70 by the moving mechanism 76. The moving mechanism 76 is composed of a well-known ball screw mechanism, an air cylinder mechanism, a rotary drive mechanism, etc., and can move the holding pad 75 in the horizontal direction and the vertical direction (Z-axis direction). A porous plate 77 connected to a suction source 78 via a suction path is provided on the lower surface side of the holding pad 75, and the suction force acts on the lower surface of the porous plate 77 by sucking air with the suction source 78, thereby holding the wafer W. The wafer W, whose other side Wb is suction-held by the holding pad 75, is positioned above the sheet S and liquid resin L on the table 70 with one side Wa facing downward.

[0095] 7, the holding pad 75 is lowered by the moving mechanism 76 to press one surface Wa of the wafer W against the liquid resin L. The liquid resin L, which receives the force pressing the wafer W, is spread from the center toward the outer periphery between the wafer W and the sheet S. When the liquid resin L is spread to cover the entire surface Wa of the wafer W, the lowering of the holding pad 75 by the moving mechanism 76 is stopped.

[0096] In the curing step shown in Fig. 8, ultraviolet rays UV are irradiated from an ultraviolet irradiator 72. The ultraviolet rays UV irradiated from the ultraviolet irradiator 72 penetrate the table 70 and the sheet S to reach the liquid resin L and cure the ultraviolet-curable liquid resin L. As shown in Figs. 9 and 10, a protective member H that covers the entire surface of one side Wa of the wafer W is formed by the cured resin R in which the liquid resin L is cured and the sheet S.

[0097] The liquid resin L may be thermosetting. In this case, in order to harden the thermosetting liquid resin L, a heater is disposed on the table 70, and the liquid resin L is hardened by applying heat from the heater through the sheet S. Alternatively, a heater may be disposed on the holding pad 75, and the liquid resin L may be hardened by applying heat from the heater through the wafer W.

[0098] 9, the wafer W on which the protective member H has been formed is transported and placed on a cutting stage 79 provided in the protective member forming apparatus 3. The sheet S is placed on the upper surface of the cutting stage 79, and the wafer W is held on the cutting stage 79 via the protective member H. An annular cutter entrance groove 80 is formed on the upper surface of the cutting stage 79, and the sheet S is positioned so as to cover the cutter entrance groove 80.

[0099] A cutter arm 82 that is rotated by a motor 81 is disposed above the cutting stage 79, and a cutter 83 is supported on the tip side of the cutter arm 82. The cutter 83 is caused to cut into the cutter entrance groove 80 to a position where it enters the cutter entrance groove 80, and the cutter arm 82 is rotated by the motor 81, whereby the cutter 83 moving along the cutter entrance groove 80 cuts the outer periphery of the sheet S, and the sheet S becomes circular.

[0100] 10 shows a state in which the outer peripheral portion of the sheet S is cut by a cutter 83 to form a protective member H consisting of the cured resin R and the sheet S. The area of ​​the sheet S cut by the cutter 83 is larger than the area of ​​the wafer W, and the sheet S has a protruding portion Sa that protrudes beyond the outer peripheral side of the wafer W.

[0101] The wafer W having the protective member H formed on the entire surface of one side Wa by the above protective member forming process is transferred to a grinding device 4, as shown in Fig. 11, and a first holding process, a first grinding process, a first separating process, and a second grinding process are performed. In the first grinding process and the second grinding process, the other side Wb of the wafer W, on which the protective member H is not formed, is ground.

[0102] [First holding step] In the first holding step, the wafer W is held on the chuck table 85 of the grinding device 4 via the protective member H. That is, the protective member H is placed on the chuck table 85 with one surface Wa of the wafer W facing downward. The chuck table 85 has a configuration similar to that of the chuck table 20 in the grinding device 1 of the above embodiment. The chuck table 85 includes a frame 86 and a disk-shaped porous plate 87 attached in a recess on the upper surface side of the frame 86. When the suction source 88 is operated, air is sucked from the porous plate 87, and a suction force acts on the holding surface 89 of the chuck table 85. In the first holding step, the protective member H placed on the holding surface 89 is held by the suction force.

[0103] The chuck table 85 is rotatably supported by a table rotation mechanism 90, and the tilt can be adjusted by a tilt adjustment mechanism 91. The table rotation mechanism 90 and the tilt adjustment mechanism 91 have the same configuration as the table rotation mechanism 35 and the tilt adjustment mechanism 38 in the grinding device 1 of the above embodiment, and detailed description thereof will be omitted.

[0104] [First grinding process] In the first grinding process, a grinding wheel 93 of a grinding mechanism 92 is used to grind the other surface Wb of the wafer W held on the chuck table 85 by a first grinding amount that is less than a target grinding amount (first predetermined grinding amount) for the other surface Wb.

[0105] The grinding mechanism 92 has the same configuration as the grinding mechanism 50 of the above embodiment. A mount 95 is connected to the lower end of a spindle shaft 94 constituting a spindle unit, a grinding wheel 96 is attached to the mount 95, and a plurality of grinding stones 93 are arranged in an annular shape on the lower surface of the grinding wheel 96. The grinding wheel 96 is rotated by the spindle unit including the spindle shaft 94. In addition, the grinding mechanism 92 is moved up and down (in the Z-axis direction) by an elevation mechanism 97.

[0106] The height detection unit 98 has a configuration similar to that of the height detection unit 40 in the above embodiment, and detects the height of the top surface of the wafer W using one of two probes, and detects the height of the holding surface 89 of the chuck table 85 using the other probe, thereby measuring the thickness of the wafer W (the total thickness of the wafer W and the protective member H before the protective member H is peeled off).

[0107] The first grinding step is the same as the first grinding step in the period TC in Fig. 3 of the above embodiment. As in the above embodiment, the process starts with the grinding mechanism 92 in a standby position above the wafer W, and then an initial lowering step in a period TA and an air cutting step in a period TB are performed, and the first grinding step is performed following the air cutting step.

[0108] In the first grinding step, with the grinding wheel 93 in contact with the other surface Wb of the wafer W, the grinding mechanism 92 is lowered at a constant speed by the lifting mechanism 97, while the chuck table 85 is rotated by the table rotation mechanism 90 and the grinding wheel 96 is rotated by the spindle unit, so that the other surface Wb of the wafer W is ground by the grinding wheel 93. The height detection unit 98 is used to measure the total thickness of the wafer W and protective member H, and the other surface Wb of the wafer W is ground until it reaches a thickness obtained by subtracting the first grinding amount from the thickness of the wafer W and protective member H before the start of the first grinding step.

[0109] [First separation process] When the first grinding amount is completed for the other surface Wb of the wafer W, a first separation step is performed. The first separation step is the same as the separation step during the period TD in Fig. 3 of the above embodiment. In the first separation step, the grinding mechanism 92 is raised by the lifting mechanism 97, and the grinding wheel 93 is separated from the other surface Wb of the wafer W to release the load on the wafer W.

[0110] [Second grinding process] Following the first separating step, a second grinding step is performed. The second grinding step is the same as the second grinding step during the period TE in FIG. 3 of the above embodiment. In the second grinding step, the grinding wheel 93 of the grinding mechanism 92 is brought into contact with the other surface Wb of the wafer W again, and the other surface Wb of the wafer W held on the chuck table 85 is ground by the grinding wheel 93 by a second grinding amount, which is the first predetermined grinding amount (the target grinding amount of the other surface Wb)-the first grinding amount.

[0111] In the second grinding step, similarly to the first grinding step, with the grinding wheel 93 in contact with the other surface Wb of the wafer W, the grinding mechanism 92 is lowered at a constant speed by the lifting mechanism 97, the chuck table 85 is rotated by the table rotation mechanism 90, and the grinding wheel 96 is rotated by the spindle unit, so that the other surface Wb of the wafer W is ground by the grinding wheel 93. The height detection unit 98 is used to measure the total thickness of the wafer W and the protective member H, and the other surface Wb of the wafer W is ground until the total thickness is equal to the thickness of the wafer W and the protective member H before the start of the second grinding step minus the second grinding amount.

[0112] When the first grinding process, through the first separation process, and then to the second grinding process, is performed, the other surface Wb is ground with a first predetermined grinding amount (target grinding amount for the other surface Wb) which is the sum of the first grinding amount in the first grinding process and the second grinding amount in the second grinding process.

[0113] After the second grinding step, a spark-out step in a period TF, an escape cut step in a period TG, and a final rising step in a period TH are performed, similar to Fig. 3 of the above embodiment. At the stage where the final rising step is performed, the grinding mechanism 92 returns to the standby position above the wafer W, and grinding of the other surface Wb of the wafer W is completed.

[0114] [Peeling process] After the grinding of the other surface Wb of the wafer W is completed, a peeling step shown in Fig. 12 to Fig. 14 is performed. In the peeling step, the protective member H is peeled off from one surface Wa of the wafer W.

[0115] First, the wafer W with the protective member H is transported to the peeling device 5. The peeling device 5 is equipped with a transport mechanism 100. The transport mechanism 100 transports the wafer W by suction-holding the other side Wb of the wafer W on the lower surface of a holding pad 101. A porous plate 103 connected to a suction source 102 via a suction path is provided on the lower surface side of the holding pad 101, and by sucking air with the suction source 102, a suction force acts on the lower surface of the porous plate 103 to hold the wafer W.

[0116] The holding pad 101 is supported by a support arm 104, and the support arm 104 is moved in a horizontal direction by a slide mechanism 105. The slide mechanism 105 supports the support arm 104 movably along a guide rail 106 extending in the horizontal direction, and moves the support arm 104 along the guide rail 106 by a well-known ball screw mechanism or air cylinder mechanism. The direction in which the support arm 104 is moved by the slide mechanism 105 when peeling the protective member H from the wafer W is referred to as a peeling movement direction P (see FIGS. 13 and 14).

[0117] The peeling device 5 includes a peeling roller 107 extending approximately perpendicular to the direction of movement of the holding pad 101 by the slide mechanism 105. The peeling device 5 also includes a clamp unit 108 capable of gripping a protruding portion Sa of the sheet S of the protection member H. The clamp unit 108 grips the protruding portion Sa of the sheet S between a pair of claws 109.

[0118] The clamp unit 108 is supported so as to be rotatable around a support shaft 110, and can be rotated by a motor (not shown). The support shaft 110 is supported so as to be movable in the horizontal and vertical directions (Z-axis direction), and its horizontal and vertical positions can be changed by a movement mechanism (not shown).

[0119] 12, the clamp portion 108 is located near the peeling roller 107 and is positioned on the peeling movement direction P side of the peeling roller 107. A pair of claw portions 109 of the clamp portion 108 are positioned at approximately the same height as the sheet S, and their tips face horizontally (opposite the peeling movement direction P).

[0120] 13, the clamp portion 108 is rotated downward by approximately 90° with respect to the first gripping position, and the tips of the pair of claw portions 109 face upward. Also, at the second gripping position, the support shaft 110 has moved downward from the first gripping position and in the opposite direction to the peeling movement direction P, and the clamp portion 108 is located below the peeling roller 107.

[0121] 14, the clamp portion 108 is rotated approximately 180° with respect to the first gripping position, and the tips of the pair of claw portions 109 face the horizontal direction (peeling movement direction P) in the opposite direction to the first gripping position. Also, in the third gripping position, the support shaft 110 has moved lower than the second gripping position and in the opposite direction to the peeling movement direction P, and the clamp portion 108 is significantly separated from the peeling roller 107.

[0122] In the initial stage of the peeling process, as shown in FIG. 12, while the other side Wb of the wafer W is held by suction on the underside of the holding pad 101, the protruding portion Sa of the sheet S is gripped by a pair of claws 109 of the clamp portion 108 at the first gripping position, and the peeling roller 107 is brought into contact with the underside of the sheet S at a position close to the gripped portion.

[0123] 13, the clamp unit 108 is moved to the second gripping position, and the slide mechanism 105 moves the holding pad 101 and the support arm 104 in the peeling movement direction P. By these operations, the protruding portion Sa of the sheet S gripped by the clamp unit 108 is pulled downward, and a part of the outer periphery of the protective member H is peeled off from one surface Wa of the wafer W and bent downward along the peeling roller 107.

[0124] 14, the clamp unit 108 is moved to the third gripping position, and the slide mechanism 105 further moves the holding pad 101 and the support arm 104 in the peeling movement direction P. By these operations, the sheet S gripped by the clamp unit 108 is pulled diagonally downward while being guided by the peeling roller 107, and peeling of the protective member H progresses in the diameter direction of the wafer W.

[0125] As described above, the peeling process is performed to peel off the protective member H from one side Wa of the wafer W. The wafer W from which the protective member H has been peeled off is transported to the grinding device 4 as shown in Fig. 15, where the second holding process, the third grinding process, the second separating process, and the fourth grinding process are performed. In the third grinding process and the fourth grinding process, the one side Wa of the wafer W is ground. Note that the target grinding amount of the one side Wa of the wafer W and the target grinding amount of the other side Wb may be different or the same.

[0126] [Second holding process] In the second holding step, the other side Wb of the wafer W is held on the chuck table 85 of the grinding device 4. That is, the wafer W is placed on the chuck table 85 with the other side Wb that has been ground in the first grinding step facing downward. The suction source 88 is operated to apply a suction force to the holding surface 89 of the porous plate 87, and the other side Wb placed on the holding surface 89 is held by receiving the suction force.

[0127] [Third grinding process] In the third grinding process, a grinding wheel 93 of a grinding mechanism 92 is used to grind one side Wa of the wafer W held on the chuck table 85 by a third grinding amount that is less than the target grinding amount (second specified grinding amount) for the one side Wa.

[0128] The third grinding step is the same as the first grinding step in the period TC in Fig. 3 of the above embodiment. As in the above embodiment, the process starts with the grinding mechanism 92 in a standby position above the wafer W, and then an initial lowering step in a period TA and an air cutting step in a period TB are performed, and the third grinding step is performed following the air cutting step.

[0129] In the third grinding step, with the grinding wheel 93 in contact with one side Wa of the wafer W, the grinding mechanism 92 is lowered at a constant speed by the lifting mechanism 97, while the chuck table 85 is rotated by the table rotation mechanism 90 and the grinding wheel 96 is rotated by the spindle unit, so that the one side Wa of the wafer W is ground by the grinding wheel 93. The thickness of the wafer W is measured using the height detection unit 98, and the one side Wa of the wafer W is ground until the thickness of the wafer W before the start of the third grinding step is reduced by the third grinding amount.

[0130] The third grinding amount of one surface Wa of the wafer W in the third grinding step may be different from or the same as the first grinding amount of the other surface Wb of the wafer W in the first grinding step.

[0131] [Second separation process] When the grinding of the third grinding amount is completed for one surface Wa of the wafer W, a second separation step is performed. The second separation step is the same as the separation step during the period TD in Fig. 3 of the above embodiment. In the second separation step, the grinding mechanism 92 is raised by the lifting mechanism 97, and the grinding wheel 93 is separated from the one surface Wa of the wafer W to release the load applied to the wafer W.

[0132] [Fourth grinding process] Following the second separating step, a fourth grinding step is performed. The fourth grinding step is the same as the second grinding step during the period TE in FIG. 3 of the above embodiment. In the fourth grinding step, the grinding wheel 93 of the grinding mechanism 92 is brought into contact with one side Wa of the wafer W again, and the one side Wa of the wafer W held on the chuck table 85 is ground by the grinding wheel 93 by a fourth grinding amount, which is the second predetermined grinding amount (the target grinding amount of the one side Wa) minus the third grinding amount.

[0133] In the fourth grinding step, similarly to the third grinding step, with the grinding wheel 93 in contact with one side Wa of the wafer W, the grinding mechanism 92 is lowered at a constant speed by the lifting mechanism 97, the chuck table 85 is rotated by the table rotation mechanism 90, and the grinding wheel 96 is rotated by the spindle unit, so that the one side Wa of the wafer W is ground by the grinding wheel 93. The thickness of the wafer W is measured using the height detection unit 98, and the one side Wa of the wafer W is ground until it reaches a thickness obtained by subtracting the fourth grinding amount from the thickness of the wafer W before the fourth grinding step is started.

[0134] The fourth grinding amount of one surface Wa of the wafer W in the fourth grinding step may be different from or the same as the second grinding amount of one surface Wa of the wafer W in the second grinding step.

[0135] When the third grinding process, through the second separating process, and up to the fourth grinding process are performed, one of the faces Wa is ground with a second predetermined grinding amount (target grinding amount for one of the faces Wa) which is the sum of the third grinding amount in the third grinding process and the fourth grinding amount in the fourth grinding process.

[0136] After the fourth grinding step, a spark out step in a period TF, an escape cut step in a period TG, and a final rising step in a period TH are performed, similar to Fig. 3 of the above embodiment. At the stage where the final rising step is performed, the grinding mechanism 92 returns to the standby position above the wafer W, and grinding of one surface Wa of the wafer W is completed.

[0137] As described above, according to the wafer manufacturing method of this embodiment, in grinding one side Wa and the other side Wb of the wafer W, a separation step (first separation step, second separation step) is performed in which the grinding wheel 93 is separated from the wafer W midway to release the load applied to the wafer W, and a predetermined grinding amount (target grinding amount) is ground in two separate steps, thereby preventing the load from being continuously applied to the wafer W from the grinding wheel 93 and suppressing changes in the inclination of the chuck table 85. Therefore, it is possible to improve the thickness accuracy of the wafer W manufactured by grinding both sides of a sliced ​​wafer sliced ​​from an ingot.

[0138] In this embodiment, one side Wa and the other side Wb of the wafer W are ground in two separate steps, each with a specified grinding amount, but three or more grinding steps may be performed with two or more separation steps in between.

[0139] In addition, the number of grinding steps separately performed on one side Wa of the wafer W and the number of grinding steps separately performed on the other side Wb of the wafer W may be different. For example, when the target grinding amount (first predetermined grinding amount) of the other side Wb is greater than the target grinding amount (second predetermined grinding amount) of the one side Wa, it is possible to set the other side Wb to perform three grinding steps with two separation steps therebetween, and the one side Wa to perform two grinding steps with one separation step therebetween. By setting the number of grinding steps and separation steps on each side of the wafer W in this way, it is possible to prevent the grinding wheel 93 from continuously applying a load to the wafer W for a long period of time in grinding the other side Wb having a larger target grinding amount, suppress the inclination change of the chuck table 85, and improve the thickness accuracy of the wafer W after grinding.

[0140] The embodiments of the present invention are not limited to the above-mentioned embodiments and modifications, and may be modified, substituted, or altered in various ways without departing from the spirit of the technical idea of ​​the present invention. Furthermore, if the technical idea of ​​the present invention can be realized in a different way due to technological progress or a different derived technology, the present invention may be implemented using that method. Therefore, the claims cover all embodiments that may be included within the scope of the technical idea of ​​the present invention. [Industrial Applicability]

[0141] As described above, the wafer grinding method and wafer manufacturing method of the present invention can improve the thickness accuracy of wafers when grinding wafers with a single grinding mechanism, contributing to improvements in the quality and yield of manufactured wafers. [Explanation of symbols]

[0142] 1: Grinding device 2: Control section 3: Protective member forming device 4: Grinding equipment 5: Peeling device 10: Foundation 11: Cassette Stage 12: Robot Hand 13: Temporary table 14: Cleaning section 20: Chuck table 21: First conveying mechanism 22: Second conveying mechanism 25: Table movement mechanism 30: Frame 31:Porous plate 32: Holding surface 34: Suction source 35: Table rotation mechanism 38: Tilt adjustment mechanism 39:Position adjustment section 40: Height detection unit 50: Grinding mechanism 52: Lifting mechanism 53: Guide rail 54: Lift table 55: Ball screw 56: Motor 58: Spindle unit 59: Spindle shaft 60: Grinding wheel 61: Mount 62: Grinding wheel 70: Table 71: Table support stage 72: Ultraviolet irradiation section 73: Supply nozzle 75: Holding pad 76: Movement mechanism 77: Porous plate 78: Suction source 79: Cutting stage 80: Cutter entrance groove 81: Motor 82: Cutter arm 83: Cutter 85: Chuck table 86: Frame 87: Porous plate 88: Suction source 89: Holding surface 90: Table rotation mechanism 91: Tilt adjustment mechanism 92: Grinding mechanism 93: Grinding wheel 94: Spindle shaft 95: Mount 96: Grinding wheel 97: Lifting mechanism 98: Height detection unit 100: Transport mechanism 101: Holding pad 102 :Suction source 103:Porous plate 104: Support arm 105: Slide mechanism 106: Guide rail 107: Peeling roller 108: Clamp section 109: Claw part 110: Support shaft C: Cassette H: Protective material Ka: Target grinding amount Kb: 1st grinding amount Kc: Second grinding amount L: Liquid resin R: Resin after curing S: Seat W: Wafer Wa: One side of the wafer Wb: the other side of the wafer

Claims

1. A method for grinding a wafer by using a grinding wheel to grind a wafer held on a chuck table, comprising the steps of: a first grinding step of grinding an upper surface of the wafer held by the holding surface of the chuck table with the grinding wheel by a first grinding amount less than a predetermined grinding amount; a separating step of separating the grinding wheel from the upper surface of the wafer to release a load applied to the wafer; a second grinding step of grinding the wafer by bringing the grinding wheel into contact with the upper surface of the wafer again and grinding the wafer by the predetermined grinding amount minus the first grinding amount; A method for grinding a wafer comprising the steps of:

2. A method for manufacturing a wafer, comprising the steps of: grinding both surfaces of a sliced ​​wafer obtained by slicing an ingot; a protective member forming step of forming a protective member on the entire surface of one surface of the wafer; a first holding step of holding the wafer on a chuck table via the protective member; a first grinding step of grinding the other surface of the wafer held on the chuck table with a grinding wheel by a first grinding amount less than a predetermined grinding amount; a first separating step of separating the grinding wheel from the other surface of the wafer to release a load applied to the wafer; a second grinding step of grinding the other surface of the wafer with the grinding wheel by a second grinding amount equal to the predetermined grinding amount minus the first grinding amount; a peeling step of peeling the protective member from the one surface of the wafer; a second holding step of holding the other surface of the wafer on the chuck table; a third grinding step of grinding the one surface of the wafer held on the chuck table with the grinding wheel by a third grinding amount less than a predetermined grinding amount; a second separating step of separating the grinding wheel from one surface of the wafer to release the load applied to the wafer; a fourth grinding step of grinding one surface of the wafer with the grinding wheel by a fourth grinding amount, which is the predetermined grinding amount minus the third grinding amount; The method for manufacturing a wafer comprises:

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