Grinding apparatus and wafer grinding method

Abstract

To provide a grinding device for performing grinding by a first grindstone and a second grindstone which uniformizes grinding time and grinding amounts for respective chuck tables at the time of grinding by the second grindstone, and achieves efficient wafer grinding.SOLUTION: A grinding device includes a turntable (30) where a plurality of chuck tables (31) are arranged, wherein a control part (80) positions the chuck tables at a first grinding position where a wafer (90) is ground by a first grindstone (51) and a second grinding position where the wafer is ground by a second grindstone (61), a first inclination control part (81) controls an inclination adjustment mechanism (33), sets a chuck spindle (312) of the chuck table positioned at the first grinding position at an angle previously set relative to a first spindle (52), and a second inclination control part (82) controls the inclination adjustment mechanism, and sets the chuck spindle of the chuck table positioned at the second grinding position at an angle previously set relative to a second spindle (62).SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a grinding device and a method for grinding a wafer.

Background Art

[0002] In a grinding device, a chuck table holding a wafer rotates, and a grindstone disposed annularly on a grinding wheel rotates and contacts the wafer, thereby grinding the wafer. Conventionally, as this type of grinding device, there is known one that checks the thickness tendency of the wafer in the radial direction and corrects the inclination of the rotation axis of the chuck table with respect to the rotation axis of the grindstone (for example, Patent Documents 1 and 2). For example, in the radial direction of the wafer, the thickness tendency of the wafer can be checked by measuring the thickness of the wafer at three locations: near the center, near the outer periphery, and an intermediate position therebetween.

[0003] In addition, some grinding devices include a rough grinding unit that grinds a wafer with a rough grindstone and a finish grinding unit that grinds a wafer with a finish grindstone, and rotate a turntable on which two or more chuck tables are arranged to position each chuck table at a grinding position with a rough grindstone and a grinding position with a finish grindstone (for example, Patent Document 2).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] Conventionally, in grinding equipment equipped with a rough grinding unit and a finish grinding unit, the tilt adjustment of the rotation axis of the chuck table to correct the wafer thickness trend was performed at the grinding position of the finish grinding wheel, based on the idea that it would suffice to make the wafer thickness trend uniform during the finish grinding stage. As a result, there were cases where the wafers on each chuck table did not have a uniform thickness trend at the stage of grinding with the rough grinding wheel. In this case, in order to eliminate the variation in thickness trend, the amount of grinding performed with the finish grinding wheel differed for each chuck table, leading to the problem of variations in grinding time. If the time required for finish grinding differs for each chuck table, the wafer production efficiency will decrease.

[0006] The present invention has been made in view of the above, and aims to achieve efficient wafer grinding by making the grinding time and amount of material removed from each chuck table uniform when grinding with the second grinding wheel, in a grinding apparatus and wafer grinding method that performs grinding with a first grinding wheel and a second grinding wheel. [Means for solving the problem]

[0009] One aspect of the present invention is a wafer grinding method comprising: rotating a turntable on which a plurality of chuck tables for holding wafers are arranged, grinding a wafer held on the chuck tables with a first grinding wheel, and then grinding it to a predetermined thickness with a second grinding wheel, the method comprising: a holding step of holding a wafer on the chuck tables; a tilt adjustment step of adjusting the chuck spindle of the chuck tables holding the wafer to a predetermined angle with respect to a first spindle on which the first grinding wheel is mounted; a first grinding step of grinding the wafer held on the chuck tables adjusted in the tilt adjustment step with the first grinding wheel; a second tilt adjustment step of adjusting the chuck spindle of the chuck tables holding the wafer ground in the first grinding step to a predetermined angle with respect to a second spindle on which the second grinding wheel is mounted; and a second grinding step of grinding the wafer held on the chuck tables adjusted in the second tilt adjustment step with the second grinding wheel. the law of nature,Prior to the first grinding step, the process includes an initial grinding step in which the wafer is ground with the first grinding wheel, a thickness measuring step in which the thickness of the wafer ground in the initial grinding step is measured at least three times in the radial direction, and a thickness trend calculation step in which the thickness trend of the wafer is calculated from the at least three thickness values ​​measured in the thickness measuring step, wherein the tilt adjustment step adjusts the tilt of the chuck spindle of each chuck table with respect to the first spindle so that the thickness trend calculated in the thickness trend calculation step matches a preset thickness trend. ru.

[0010] The wafer ground in the initial grinding step may be ground in the first grinding step. [Effects of the Invention]

[0011] According to the grinding apparatus and wafer grinding method of the present invention, by adjusting the tilt of the chuck table at the position where grinding is performed with the first grinding wheel (first grinding position) and then grinding with the first grinding wheel, the amount of grinding performed by the second grinding wheel can be made uniform, thereby achieving efficient wafer grinding. It is possible. [Brief explanation of the drawing]

[0012] [Figure 1] This is a perspective view of the grinding machine. [Figure 2] This is a cross-sectional view showing the chuck table, thickness measuring instrument, and second grinding mechanism. [Figure 3] This is a side view showing the chuck table and tilt adjustment mechanism. [Figure 4] This is a cross-sectional view showing a chuck table and part of the tilt adjustment mechanism. [Figure 5] This is a plan view showing an example of the arrangement of the tilt adjustment mechanism. [Figure 6] This is a perspective view showing the chuck table, tilt adjustment mechanism, and chuck rotation part. [Figure 7] This diagram illustrates an example of the thickness trend of a pre-set wafer and the thickness trend of a ground wafer. [Figure 8]This diagram illustrates an example where the thickness trend of a pre-set wafer differs from that of a ground wafer. [Figure 9] This is a control system diagram for a grinding machine. [Figure 10] This is a cross-sectional view showing a modified example of a thickness measuring instrument. [Modes for carrying out the invention]

[0013] The grinding apparatus and wafer grinding method will be described below with reference to the attached drawings. Figure 1 is a perspective view of the grinding apparatus according to this embodiment. The grinding apparatus to which the present invention is applied only needs to perform grinding on the wafer with a first grinding wheel and grinding with a second grinding wheel, and is not limited to the configuration shown in Figure 1.

[0014] The grinding apparatus 1 shown in Figure 1 is a fully automatic type processing apparatus and is configured to perform a series of operations, including loading the wafer 90 (the workpiece), rough grinding, finish grinding, cleaning, and unloading, all automatically.

[0015] The wafer 90 is formed in a roughly disc shape and is loaded into the grinding apparatus 1 with protective tape (not shown) attached to its underside. The wafer 90 may be a semiconductor substrate such as silicon or gallium arsenide, an inorganic material substrate such as ceramic, glass, or sapphire, or even a semiconductor product packaging substrate. The wafer 90 may also be loaded into the grinding apparatus 1 without protective tape attached to its underside.

[0016] In the grinding device 1, the X-axis, Y-axis, and Z-axis directions are perpendicular to each other. The X-axis and Y-axis directions are approximately horizontal, while the Z-axis direction is vertical. Of the two arrows indicating the X-axis direction, the side with the letter X is considered the front, and the side without the letter X is considered the rear. Of the two arrows indicating the Y-axis direction, the side with the letter Y is considered the left, and the side without the letter Y is considered the right. Of the two arrows indicating the Z-axis direction, the side with the letter Z is considered the top, and the side without the letter Z is considered the bottom.

[0017] On the front side of the base 10 of the grinding device 1, a pair of cassettes 11 containing a plurality of wafers 90 are placed. Behind the pair of cassettes 11, a robot hand 12 for loading and unloading the wafers 90 with respect to the cassettes 11 is provided. The robot hand 12 is configured by providing a hand portion 14 at the tip of a robot arm 13 composed of multi-joint links.

[0018] On the right rear diagonal of the robot hand 12, a positioning mechanism 15 for positioning the wafer 90 before grinding is provided. The positioning mechanism 15 is configured by arranging a plurality of positioning pins 17 that can advance and retreat in the radial direction of the temporary placement table 16 around the temporary placement table 16. In the positioning mechanism 15, the plurality of positioning pins 17 are abutted against the outer peripheral edge of the wafer 90 placed on the temporary placement table 16, so that the center of the wafer 90 is positioned to coincide with the center of the temporary placement table 16.

[0019] On the left rear diagonal of the robot hand 12, a cleaning mechanism 18 for cleaning the processed wafer 90 is provided. The cleaning mechanism 18 is configured by providing various nozzles (not shown) for injecting cleaning water and drying air toward a spinner table (not shown). In the cleaning mechanism 18, the spinner table holding the wafer 90 is lowered into the base 10, cleaning water is injected in the base 10 to perform spinner cleaning on the wafer 90, and then drying air is blown to dry the wafer 90.

[0020] The robot hand 12 transports the wafer 90 before grinding from the cassette 11 to the positioning mechanism 15, and transports the processed wafer 90 from the cleaning mechanism 18 to the cassette 11.

[0021] Between the positioning mechanism 15 and the cleaning mechanism 18, a loading mechanism 20 for loading the wafer 90 before grinding onto the chuck table 31 and an unloading mechanism 23 for unloading the processed wafer 90 from the chuck table 31 are provided.

[0022] The loading mechanism 20 is configured with a support arm 21 that can rotate on the base 10 around an axis in the Z-axis direction, and a holding pad 22 is provided at the tip of the support arm 21. In the loading mechanism 20, the wafer 90 is held by suction using the holding pad 22, the wafer 90 is lifted from the temporary storage table 16, and the holding pad 22 is rotated by the support arm 21, thereby loading the wafer 90 onto the chuck table 31.

[0023] The unloading mechanism 23 is configured with a support arm 24 that can rotate on the base 10 around an axis in the Z-axis direction, and a holding pad 25 is provided at the tip of the support arm 24. In the unloading mechanism 23, the wafer 90 is held by suction using the holding pad 25, lifting the wafer 90 from the chuck table 31, and the holding pad 25 is rotated by the support arm 24, so that the wafer 90 is unloaded from the chuck table 31 to the cleaning mechanism 18.

[0024] Behind the loading mechanism 20 and the unloading mechanism 23, there is a turntable 30 with three chuck tables 31 arranged at equal intervals in the circumferential direction. The turntable 30 is rotatable about a rotation axis in the Z-axis direction and is driven to rotate by a table drive mechanism (not shown).

[0025] As shown in Figure 2, each chuck table 31 is equipped with a porous member 32 on its upper part, and the porous member 32 is in communication with a suction source (not shown). The upper surface of the porous member 32 is a holding surface 321 that holds the wafer 90 by suction. Each chuck table 31 is supported so as to be rotatable about a central axis 311 that passes through the center of the holding surface 321. The structure supporting the chuck table 31 will be described later.

[0026] As shown in Figure 2, the holding surface 321 of each chuck table 31 is formed as a conical surface with its apex located on the central axis 311 and gradually sloping downwards toward the outer circumference of the chuck table 31. The wafer 90 placed on the chuck table 31 is held in a state that conforms to the conical shape of the holding surface 321. If protective tape is attached to the wafer 90 to be held by suction, the holding surface 321 will suction hold the protective tape and then suction hold the wafer 90 through the protective tape. Note that in Figure 2, the inclination of the holding surface 321 with respect to the horizontal direction and the inclination of the central axis 311 with respect to the vertical direction are exaggerated; in reality, the inclination is so slight that it is not discernible to the naked eye.

[0027] The three chuck tables 31 are positioned in the following order by the intermittent rotation of the turntable 30 at 120-degree intervals: the loading / unloading position where the wafer 90 is loaded and unloaded by the loading mechanism 20 and the unloading mechanism 23; the first grinding position where the first grinding wheel 51 of the first grinding mechanism 50 grinds the wafer 90; and the second grinding position where the second grinding wheel 61 of the second grinding mechanism 60 grinds the wafer 90. In the first grinding position, the wafer 90 on the chuck table 31 is roughly ground to a predetermined thickness by the first grinding wheel 51. In the second grinding position, the wafer 90 on the chuck table 31 is finish ground to a finish thickness by the second grinding wheel 61.

[0028] The first grinding mechanism 50 is equipped with a disc-shaped mount 53 at the lower end of a first spindle 52 extending in the Z-axis direction, and a grinding wheel 54 is mounted on the lower part of the mount 53. A first grinding wheel 51 is arranged in an annular shape on the lower surface of the grinding wheel 54.

[0029] The second grinding mechanism 60 is equipped with a disc-shaped mount 63 at the lower end of a second spindle 62 extending in the Z-axis direction, and a grinding wheel 64 is mounted on the lower part of the mount 63. A second grinding wheel 61 is arranged in an annular shape on the lower surface of the grinding wheel 64.

[0030] The first spindle 52 and the second spindle 62 are, for example, air spindles, and are rotatably supported about an axis in the Z-axis direction via high-pressure air.

[0031] The first grinding wheel 51 and the second grinding wheel 61 are composed of diamond grinding wheels, for example, in which diamond abrasive grains are bonded together with a binder such as a metal bond or a resin bond. The second grinding wheel 61 is formed of abrasive grains with a finer particle size than the first grinding wheel 51.

[0032] Behind the first and second grinding positions on the turntable 30, a column 101 supporting the first grinding mechanism 50 and a column 102 supporting the second grinding mechanism 60 are erected.

[0033] A first lifting mechanism for moving the first grinding mechanism 50 up and down is provided on the front of the column 101. The first lifting mechanism has a pair of parallel guide rails 55 (only one shown) extending in the Z-axis direction on the front of the column 101, and a ball screw 56 extending in the Z-axis direction between the pair of guide rails 55. A lifting table 57 is supported on the pair of guide rails 55 so as to be slidable in the Z-axis direction. The first grinding mechanism 50 is supported on the front of the lifting table 57 via a housing 58. A ball screw 56 is screwed into the back side of the lifting table 57, and a motor 59 is connected to one end of the ball screw 56. The motor 59 rotates the ball screw 56, causing the first grinding mechanism 50 to move in the Z-axis direction along the guide rails 55.

[0034] A second lifting mechanism for moving the second grinding mechanism 60 up and down is provided on the front of column 102. The second lifting mechanism has a pair of parallel guide rails 65 (only one shown) extending in the Z-axis direction on the front of column 102, and a ball screw 66 extending in the Z-axis direction between the pair of guide rails 65. A lifting table 67 is supported on the pair of guide rails 65 so as to be slidable in the Z-axis direction. The second grinding mechanism 60 is supported on the front of the lifting table 67 via a housing 68. A ball screw 66 is screwed into the back of the lifting table 67, and a motor 69 is connected to one end of the ball screw 66. The motor 69 rotates the ball screw 66, causing the second grinding mechanism 60 to move in the Z-axis direction along the guide rails 65.

[0035] A thickness measuring gauge 70 and a thickness measuring gauge 71 are provided near the turntable 30. The thickness measuring gauge 70 measures the thickness of the wafer 90 held on the chuck table 31 located at the first grinding position below the first grinding mechanism 50. The thickness measuring gauge 71 measures the thickness of the wafer 90 held on the chuck table 31 located at the second grinding position below the second grinding mechanism 60.

[0036] Each thickness measuring gauge 70 and 71 comprises a reference height gauge 701 and 711 for measuring the height position of the holding surface 321 of the chuck table 31, and a wafer height gauge 702 and 712 for measuring the height position of the top surface of the wafer 90. The reference height gauges 701 and 711 are contact-type height gauges that detect the height position of the holding surface 321 by bringing a contact probe into contact with the holding surface 321 and measuring the height of the contact position. Similarly, the wafer height gauges 702 and 712 are contact-type height gauges that detect the height position of the top surface of the wafer 90 by bringing a contact probe into contact with the top surface of the wafer 90 and measuring the height of the contact position. The thickness of the wafer 90 is then measured based on the difference between the measured values ​​of the reference height gauges 701 and 711 and the measured values ​​of the wafer height gauges 702 and 712.

[0037] Furthermore, a non-contact thickness measuring device 72 is provided near the thickness measuring gauge 71. The thickness measuring device 72 measures the thickness of the wafer 90 held on the chuck table 31, which is positioned at the second grinding position below the second grinding mechanism 60.

[0038] As shown in Figure 2, the thickness measuring device 72 comprises a stand 721 erected on the outer circumference of the turntable 30 and a support arm 722 extending upward from the stand 721 towards the chuck table 31. Three sensors 723, 724, and 725 are attached to the support arm 722. The three sensors 723, 724, and 725 are positioned at different locations in the radial direction of the wafer 90 held on the chuck table 31.

[0039] The sensors 723, 724, and 725 of the thickness measuring device 72 measure the thickness of the wafer 90 by irradiating it with laser light from above.

[0040] For example, the thickness measuring instrument 72 receives the top reflected light from the top surface of the wafer 90 and the bottom reflected light from the bottom surface of the wafer 90 using sensors 723, 724, and 725, and measures the thickness of the wafer 90 using a spectral interference method that utilizes the principle of interference between the top reflected light and the bottom reflected light.

[0041] As another example of the thickness measuring device 72, the top surface reflected light from the top surface of the wafer 90 is received by sensors 723, 724, and 725 to measure the height position of the top surface of the wafer 90, and the holding surface reflected light from the holding surface 321 of the chuck table 31 is received by sensors 723, 724, and 725 to measure the height position of the holding surface 321, and the thickness of the wafer 90 is measured by the difference between the height of the top surface of the wafer 90 and the height of the holding surface 321.

[0042] The thickness measuring device 72 can measure the thickness at three locations in the radial portion of the wafer 90 using three sensors 723, 724, and 725. More specifically, the sensor 723 located at the tip of the support arm 722 measures the thickness near the center of the wafer 90, the sensor 725 located at the base of the support arm 722 measures the thickness near the outer edge of the wafer 90, and the sensor 724 located in the middle of the support arm 722 measures the thickness at the midpoint of the radial portion of the wafer 90.

[0043] As shown in Figures 3 to 6, each chuck table 31 is equipped with a cylindrical chuck spindle 312 with a central axis 311 below the porous member 32. The tilt of the chuck spindle 312 can be adjusted by the tilt adjustment mechanism 33. Specifically, the tilt of the chuck spindle 312 is adjusted using the tilt adjustment mechanism 33 so that the portion of the wafer 90 that contacts the first grinding wheel 51 and the second grinding wheel 61, which is shaped to follow the conical holding surface 321, is parallel to the lower surface of the first grinding wheel 51 and the lower surface of the second grinding wheel 61 when viewed from the side.

[0044] The tilt adjustment mechanism 33 comprises a support base 34, a position adjustment unit 35 connected to the support base 34, and a fixed support part 36 (see Figure 6). The support base 34 comprises a cylindrical support cylinder part 341 and a disc-shaped flange 342 with an enlarged diameter at the lower part of the support cylinder part 341. The tilt adjustment mechanism 33 adjusts the tilt of the chuck spindle 312 by operating the position adjustment unit 35 to tilt the flange 342 using the fixed support part 36 as a fulcrum.

[0045] As shown in Figure 4, the chuck spindle 312 is inserted into the support cylinder portion 341 of the support base 34. A bearing 343, positioned inside the support cylinder portion 341, contacts the outer surface of the chuck spindle 312, and the chuck spindle 312 is rotatably supported via the bearing 343.

[0046] The position adjustment units 35 are provided at two or more locations on the support base 34 at different positions in the circumferential direction, and each position adjustment unit 35 is connected to the flange 342. Figure 5 shows an example of the arrangement of the position adjustment units 35 and the fixed support unit 36. In the configuration of Figure 5, two position adjustment units 35 and one fixed support unit 36 ​​are arranged at 120-degree intervals (equal intervals) in the circumferential direction. The fixed support unit 36 ​​supports the flange 342 at a fixed height position. The two position adjustment units 35 can operate independently to change the height position of the flange 342.

[0047] As shown in Figure 6, each position adjustment unit 35 comprises a cylindrical portion 351 fixed to the turntable 30, a movable shaft 352 passing through the cylindrical portion 351, a motor 353 connected to the lower end of the movable shaft 352, and a clamping nut 354 that clamps the flange 342 from above and below. The cylindrical portion 351 passes through a hole in the turntable 30 in the Z-axis direction. A threaded portion (not shown) formed on the upper end side of the movable shaft 352 passes through the flange 342 and is screwed into the clamping nut 354. The motor 353 rotates the movable shaft 352, causing the clamping nut 354 to change position along the movable shaft 352, and the flange 342 clamped by the clamping nut 354 changes its height position in the Z-axis direction.

[0048] The tilt adjustment mechanism 33 is not limited to the above configuration. For example, it may be configured to have three or more position adjustment units 35 instead of two. Alternatively, the movable shaft 352 may slide in the Z-axis direction without rotating to change the height of the flange 342.

[0049] The chuck spindle 312 is rotated by the chuck rotating unit 37. The chuck rotating unit 37 comprises a motor 371, a belt pulley 372 provided on the output shaft of the motor 371, and a transmission belt 373 wrapped around the belt pulley 372 and the chuck spindle 312. When the motor 371 rotates the belt pulley 372, the rotational force is transmitted to the chuck spindle 312 via the transmission belt 373. As the chuck spindle 312, which passes through the center (central axis 311) of the holding surface 321, rotates, the chuck table 31 rotates.

[0050] The grinding apparatus 1 is equipped with a control unit 80 that provides overall control of each part of the apparatus (see Figures 1 and 9). The control unit 80 consists of a processor and memory that perform various processes. The control unit 80 controls various operations such as the transport of wafers 90 between parts of the grinding apparatus 1, rough grinding by the first grinding wheel 51, finish grinding by the second grinding wheel 61, thickness measurement of wafers 90, and cleaning of wafers 90, according to a control program stored in the memory. Processing-related data such as the target finish thickness of the wafer 90, the amount of rough grinding on the wafer 90, the amount of finish grinding on the wafer 90, and a preset thickness trend of the wafer 90 are temporarily stored in the memory of the control unit 80.

[0051] In addition, unless otherwise specified, the operation of each part of the grinding apparatus 1 described below is controlled by a control signal sent from the control unit 80.

[0052] In the grinding apparatus 1 configured as described above, the tilt of the chuck table 31 is adjusted at both the first and second grinding positions when grinding the wafer 90. Specifically, the first tilt control unit 81 (see Figure 9) of the control unit 80 controls the tilt adjustment mechanism 33 so that the chuck spindle 312 of the chuck table 31, positioned at the first grinding position by the rotation of the turntable 30 by the control unit 80, is at a preset angle relative to the first spindle 52. Similarly, the second tilt control unit 82 (see Figure 9) of the control unit 80 controls the tilt adjustment mechanism 33 so that the chuck spindle 312 of the chuck table 31, positioned at the second grinding position by the rotation of the turntable 30 by the control unit 80, is at a preset angle relative to the second spindle 62. The various work processes in the grinding apparatus 1, including this tilt adjustment of the chuck table 31, will now be described.

[0053] [Holding process] The wafer 90, before grinding, is removed from the cassette 11 by the robot hand 12 and transported to the positioning mechanism 15, where the wafer 90 is centered. Subsequently, the loading mechanism 20 loads the wafer 90 into the chuck table 31 at the loading / unloading position, and the wafer 90 is held on the holding surface 321.

[0054] [Initial grinding process] Once the wafer 90 is held in place by the chuck table 31 at the loading / unloading position, the control unit 80 rotates the turntable 30 to position the chuck table 31 at the first grinding position. The control unit 80 then executes an initial grinding process in which the upper surface of the wafer 90 is ground by the first grinding wheel 51 of the first grinding mechanism 50.

[0055] In the initial grinding process, the first grinding mechanism 50 is lowered by the first lifting mechanism to bring the first grinding wheel 51 into contact with the upper surface of the wafer 90, and the grinding wheel 54 is rotated by the first spindle 52. At the same time, the chuck spindle 312 is rotated by the chuck rotating part 37 on the chuck table 31 positioned at the first grinding position. In this way, the upper surface of the wafer 90 is ground by the first grinding wheel 51 while the first grinding wheel 51 and the wafer 90 on the chuck table 31 are rotated respectively. When a predetermined grinding amount set in advance for the initial grinding is reached, that is, when the wafer 90 is ground to a predetermined thickness, the rotation of the grinding wheel 54 and the rotation of the chuck spindle 312 are stopped, and the first grinding mechanism 50 is raised by the first lifting mechanism to separate the first grinding wheel 51 from the wafer 90 on the chuck table 31, thereby ending the initial grinding process.

[0056] [Thickness measurement process] Once the initial grinding process is complete, the control unit 80 rotates the turntable 30 to position the chuck table 31, which holds the wafer 90 after initial grinding, at the second grinding position. The control unit 80 then uses the thickness measuring instrument 72 to perform a thickness measurement process, measuring the thickness of the wafer 90 ground in the radial direction at at least three locations.

[0057] [Thickness trend calculation process] Next, the control unit 80 executes a thickness trend calculation process, which calculates the thickness trend of the wafer 90 from at least three thickness values ​​measured in the thickness measurement process (performs shape calculations for the wafer 90).

[0058] For example, the thickness of a wafer 90 measured by three sensors 723, 724, and 725 of the thickness measuring instrument 72 can be measured. The height positions of the wafer 90's upper surface at three locations—near the outer edge, midway in the radial direction, and near the center—can be coordinated in the Z-axis direction, and the thickness trend can be represented as a curved shape smoothly connecting these three points.

[0059] Furthermore, the thickness measuring device 72 may be equipped with four or more sensors, and the thickness may be measured at four or more locations in the radial direction of the wafer 90 during the thickness measurement process. In this case, the thickness trend may be represented by an approximation curve based on the four or more thickness values ​​measured in the thickness measurement process.

[0060] [Tilt adjustment process] Next, the control unit 80 compares the thickness trend of the wafer 90 calculated in the thickness trend calculation step with the thickness trend that has been set in advance and stored in memory, and finds the difference. If there is a difference between these thickness trends, it calculates the tilt adjustment amount so that the thickness trend of the wafer 90 calculated in the thickness trend calculation step matches the pre-set thickness trend (eliminates the difference), and executes a tilt adjustment step at the first grinding position to adjust the tilt of the chuck spindle 312 of each chuck table 31 relative to the first spindle 52.

[0061] Figure 7 shows an example of the thickness trend of wafer 90. Figure 7(A) shows the set thickness trend Ta, which is a predetermined thickness trend of wafer 90 set in advance. The data for the set thickness trend Ta is included in the grinding recipe and is stored in the memory of the control unit 80. In Figures 7(B) and 7(C), the grinding thickness trends Tb and Tc, which are the thickness trends of wafer 90 calculated in the thickness trend calculation process after initial grinding, are shown as solid lines. S in Figure 7 is the thickness measurement location where the thickness of wafer 90 is measured by the thickness measuring gauge 70 and thickness measuring gauge 71 during grinding.

[0062] In the initial grinding process, grinding is performed so that the thickness of the wafer 90 at the thickness measurement point S matches the pre-set thickness of the wafer 90 (set thickness). In other words, grinding is performed so that the difference between the post-grinding thickness and the set thickness at the thickness measurement point S is 0. Then, by performing data processing to superimpose the shapes of the set thickness trend Ta and the grinding thickness trends Tb and Tc so that the height position of the upper surface of the wafer 90 matches at the thickness measurement point S, the difference between the set thickness trend Ta and the grinding thickness trends Tb and Tc can be identified. In the grinding thickness trends Tb and Tc shown in Figure 7(B) and Figure 7(C), it can be seen that the thickness trend is mountain-shaped, with the thickness of the central part in the radial direction of the wafer 90 being larger and the thickness of the outer part being smaller, compared to the set thickness trend Ta, and that it does not match the set thickness trend Ta.

[0063] More specifically, in the grinding thickness trend Tb in Figure 7(B), as you move from the thickness measurement point S towards the outer circumference, the post-grinding thickness becomes smaller than the set thickness, and at the outer circumference of wafer 90, the difference between the set thickness and the post-grinding thickness is Ma (the difference value is negative). Also, as you move from the thickness measurement point S towards the inner circumference (center), the post-grinding thickness becomes larger than the set thickness, and at the center of wafer 90, the difference between the set thickness and the post-grinding thickness is Na (the difference value is positive).

[0064] The control unit 80 calculates the amount of tilt adjustment needed to match the grinding thickness trend Tb to the set thickness trend Ta, based on the difference between the set thickness trend Ta and the grinding thickness trend Tb. Based on the calculated amount of tilt adjustment, the control unit 80 operates the motors 353 of each position adjustment unit 35 that support the chuck table 31 at the first grinding position, and the tilt adjustment mechanism 33 adjusts the angle of the chuck spindle 312 to a preset appropriate angle relative to the first spindle 52. As a result, the thickness trend of the wafer 90 being ground by the first grinding wheel 51 of the first grinding mechanism 50 matches the set thickness trend Ta.

[0065] In the grinding thickness tendency Tc of (C) in FIG. 7, as moving from the thickness measurement location S toward the outer peripheral side, the post-grinding thickness becomes smaller than the set thickness. At the outer peripheral portion of the wafer 90, the difference between the post-grinding thickness and the set thickness is Mb (the value of the difference is negative). Also, as moving from the thickness measurement location S toward the inner peripheral side (center), the post-grinding thickness becomes larger than the set thickness. At the center of the wafer 90, the difference between the post-grinding thickness and the set thickness is Nb (the value of the difference is positive). Thus, although the overall thickness tendency of the grinding thickness tendency Tc is similar to the grinding thickness tendency Tb of (B) in FIG. 7, in the grinding thickness tendency Tc, the difference between the set thickness and the post-grinding thickness is small on the outer peripheral side and large on the inner peripheral side (center side). That is, Ma > Mb and Na < Nb, and in the grinding thickness tendency Tc, particularly on the center side of the wafer 90, the deviation amount from the set thickness is large.

[0066] Therefore, the inclination adjustment amount for making the grinding thickness tendency Tc coincide with the set thickness tendency Ta is different from the inclination adjustment amount for making the grinding thickness tendency Tb coincide with the set thickness tendency Ta. Regarding the calculation of the inclination adjustment amount related to the grinding thickness tendency Tc and the inclination adjustment operation based on the calculated inclination adjustment amount, since it is performed in the same manner as in the case of the above-described grinding thickness tendency Tb, the description is omitted.

[0067] FIG. 8 shows an example with different thickness tendencies of the wafer 90. (A) in FIG. 8 shows a set thickness tendency Td which is a predetermined thickness tendency of the wafer 90 set in advance. The data regarding the set thickness tendency Td is included in the grinding recipe and stored in the memory of the control unit 80.

[0068] In the grinding thickness tendency Te which is the thickness tendency after the initial grinding shown in (B) of FIG. 8, as moving from the thickness measurement location S (the position where the difference between the post-grinding thickness and the set thickness is 0) toward the outer peripheral side, the post-grinding thickness becomes larger than the set thickness. At the outer peripheral portion of the wafer 90, the difference between the post-grinding thickness and the set thickness is Mc (the value of the difference is positive). Also, as moving from the thickness measurement location S toward the inner peripheral side (center), the post-grinding thickness with respect to the set thickness becomes smaller. At the center of the wafer 90, the difference between the post-grinding thickness and the set thickness is Nc (the value of the difference is negative).

[0069] In the grinding thickness trend Tf shown in Figure 8(C), which represents the thickness trend after initial grinding, the post-grinding thickness becomes larger than the set thickness as you move from the thickness measurement point S (the position where the difference between the post-grinding thickness and the set thickness is 0) towards the outer circumference, and at the outer circumference of wafer 90, the difference between the post-grinding thickness and the set thickness is Md (the difference value is positive). Also, as you move from the thickness measurement point S towards the inner circumference (center), the post-grinding thickness becomes larger than the set thickness, and at the center of wafer 90, the difference between the post-grinding thickness and the set thickness is Nd (the difference value is positive). In other words, in the grinding thickness trend Tf, the post-grinding thickness is generally larger than the set thickness except at the thickness measurement point S.

[0070] The control unit 80 calculates the tilt adjustment amount to match the grinding thickness trends Te and Tf to the set thickness trend Td, based on the difference between the set thickness trend Td and the grinding thickness trends Te and Tf. Then, based on the calculated tilt adjustment amount, it operates the motors 353 of each position adjustment unit 35 that support the chuck table 31 at the first grinding position, and the tilt adjustment mechanism 33 adjusts the angle of the chuck spindle 312 to an appropriate angle set in advance with respect to the first spindle 52. As a result, the thickness trend of the wafer 90 being ground by the first grinding wheel 51 of the first grinding mechanism 50 matches the set thickness trend Td.

[0071] As described above, by performing a tilt adjustment process based on the thickness trends (grinding thickness trends Tb, Tc, Te, Tf) of the wafer 90 obtained in the thickness measurement process and thickness trend calculation process after the initial grinding process, the chuck spindle 312 of the chuck table 31 at the first grinding position is adjusted to a preset appropriate angle with respect to the first spindle 52, and the thickness trend of the wafer 90 being ground by the first grinding wheel 51 of the first grinding mechanism 50 matches the set thickness trends Ta and Td.

[0072] Therefore, since each of the multiple chuck tables 31 arranged on the turntable 30 is adjusted so that the chuck spindle 312 is at a preset appropriate angle relative to the first spindle 52 in the first grinding position, the wafers 90 held by each chuck table 31 and ground by the first grinding wheel 51 will have the same thickness tendency.

[0073] Furthermore, if there is no difference between the thickness trend of the wafer 90 calculated in the thickness trend calculation process and the thickness trend that is pre-set and stored in memory, the tilt adjustment amount in the tilt adjustment process will be 0, and the tilt adjustment operation by the tilt adjustment mechanism 33 will not be performed.

[0074] [First grinding process] Next, the control unit 80 causes the wafer 90 held on the chuck table 31, which was adjusted in the tilt adjustment step, to perform a first grinding step, in which the first grinding wheel 51 of the first grinding mechanism 50 grinds the wafer 90. In the first grinding step, the wafer 90 is roughly ground. Similar to the initial grinding step described above, in the first grinding step, the first grinding mechanism 50 is lowered by the first lifting mechanism, and the grinding wheel 54 is rotated by the first spindle 52. The chuck spindle 312 is also rotated by the chuck rotating unit 37. The upper surface of the wafer 90 is then ground with the first grinding wheel 51. When it is confirmed by the thickness measuring gauge 70 that the wafer 90 has reached the set thickness for rough grinding, the rotation of the grinding wheel 54 and the rotation of the chuck spindle 312 are stopped, and the first grinding mechanism 50 is raised by the first lifting mechanism to end the first grinding step.

[0075] In the first grinding process, not only is the unground wafer 90 transported from the cassette 11 ground, but the wafer 90 ground in the initial grinding process may also be repositioned at the first grinding position and ground again with the first grinding wheel 51 in the first grinding process. This allows the wafer 90 ground in the initial grinding process to be used without waste. In this case, the finished thickness of the wafer 90 ground in the first grinding process is set to be smaller than the thickness of the wafer ground in the initial grinding process.

[0076] [Second tilt adjustment process] Next, the control unit 80 rotates the turntable 30 to position the chuck table 31 at the second grinding position and controls the tilt adjustment mechanism 33 to adjust the chuck spindle 312 so that it is at a preset angle relative to the second spindle 62, thereby executing the second tilt adjustment process.

[0077] The tilt angle of the chuck spindle 312 of each chuck table 31 relative to the second spindle 62 in the second tilt adjustment process is stored in memory. For example, in advance, as in the case of the first grinding mechanism 50, the wafer 90 on the chuck table 31 positioned at the second grinding position is initially ground by the second grinding wheel 61 of the second grinding mechanism 60. Next, the control unit 80 uses a thickness measuring instrument 72 to measure the thickness of the wafer 90 that has been initially ground by the second grinding mechanism 60 at at least three locations in the radial direction and calculates the thickness trend of the wafer 90. Then, based on the difference between the calculated thickness trend of the wafer 90 and the thickness trend that has been set in advance and stored in memory, the control unit 80 calculates the tilt angle of the chuck spindle 312 of each chuck table 31 relative to the second spindle 62 and stores it in memory. The second tilt adjustment process is executed to adjust the tilt of each chuck spindle 312 to the tilt angle of each chuck spindle 312 stored in memory.

[0078] By performing the second tilt adjustment process, all of the chuck tables 31 arranged on the turntable 30 are adjusted so that at the second grinding position, the chuck spindle 312 is at a preset appropriate angle relative to the second spindle 62. As a result, the wafers 90 held by each chuck table 31 and ground by the second grinding wheel 61 tend to have the same thickness.

[0079] [Second grinding process] Next, the control unit 80 causes the wafer 90 on the chuck table 31, which is positioned at the second grinding position, to be ground by the second grinding wheel 61 of the second grinding mechanism 60 in a second grinding process. In the second grinding process, the wafer 90 is finished grinding.

[0080] In the second grinding process, the second grinding mechanism 60 is lowered by the second lifting mechanism, and the grinding wheel 64 is rotated by the second spindle 62. Also, the chuck spindle 312 is rotated by the chuck rotating part 37 on the chuck table 31 positioned at the second grinding position. In this way, the upper surface of the wafer 90 is ground by the second grinding wheel 61 while the second grinding wheel 61 and the wafer 90 on the chuck table 31 are rotated respectively. When it is confirmed by the thickness measuring gauge 71 that the wafer 90 has reached the finish thickness, the rotation of the grinding wheel 64 and the rotation of the chuck spindle 312 are stopped, and the second grinding mechanism 60 is raised by the second lifting mechanism to end the second grinding process.

[0081] [Washing process, unloading process] Next, the control unit 80 rotates the turntable 30 to position the chuck table 31, which holds the wafer 90 ground in the second grinding process, at the loading / unloading position. Then, the loading mechanism 23 loads the wafer 90 from the chuck table 31 to the cleaning mechanism 18, where the ground wafer 90 is cleaned. After cleaning, the wafer 90 is transported by the robot hand 12 and placed in the cassette 11.

[0082] After completing the above steps, the series of operations on the wafer 90 in the grinding machine 1 is finished.

[0083] Figure 9 is a block diagram conceptually showing a part of the control system of the grinding apparatus 1, including the control unit 80. The tilt adjustment of the chuck spindles 312 of each chuck table 31 at the first grinding position is controlled by the first tilt control unit 81, which is a functional block of the control unit 80. The tilt adjustment of the chuck spindles 312 of each chuck table 31 at the second grinding position is controlled by the second tilt control unit 82, which is a functional block of the control unit 80.

[0084] The process of measuring the thickness of the wafer 90 ground in the initial grinding process using a thickness measuring instrument 72 and calculating the thickness trend of the wafer 90 is performed by the thickness trend calculation unit 83, which is a functional block of the control unit 80.

[0085] Furthermore, the process of determining the difference between the thickness trend of the wafer 90 calculated by the thickness trend calculation unit 83 and a predetermined thickness trend set in advance (calculating the tilt adjustment amount) is performed by the calculation unit 84, which is a functional block included in the first tilt control unit 81.

[0086] It should be noted that the first tilt control unit 81, the second tilt control unit 82, the thickness trend calculation unit 83, and the calculation unit 84 in the control unit 80 are conceptual functional blocks, and this does not mean that each of these parts exists individually. The functions of each part in the control unit 80 are realized by the operation of the processor, memory, and other components that make up the control unit 80.

[0087] As described above, in the grinding apparatus 1 of this embodiment, the chuck spindle 312 of the chuck table 31 positioned at the first grinding position is tilted to a preset angle relative to the first spindle 52 of the first grinding mechanism 50. As a result, the wafers 90 for each chuck table 31 ground by the first grinding wheel 51 of the first grinding mechanism 50 tend to have a uniform thickness, and the amount of grinding for each wafer 90 ground by the second grinding wheel 61 of the second grinding mechanism 60 is made uniform, eliminating differences in grinding time.

[0088] Furthermore, when adjusting the tilt of the chuck spindle 312, the thickness trend of the wafer 90 is calculated (shape calculation) from the thickness values ​​at three or more locations in the radial direction, and the difference from a pre-set thickness trend is compared. By using shape calculation data for the overall thickness trend of the wafer 90, it is possible to perform tilt adjustment with higher accuracy than when using only data for thickness values ​​measured spot at specific locations in the radial direction of the wafer 90.

[0089] A different thickness measuring instrument than the one shown in Figure 2 (thickness measuring instrument 72) may be used. In the modified thickness measuring instrument 73 shown in Figure 10, a stand 731 erected on the outer circumference of the turntable 30 is configured to rotate about an axis in the Z-axis direction. A support arm 732 extending from the stand 731 upwards toward the chuck table 31 is fitted with a sensor 733. The sensor 733 is a non-contact type sensor that measures the thickness of the wafer 90 by irradiating it with laser light from above.

[0090] The rotating part 74 of the measuring instrument performs the rotational movement of the support arm 732. The rotating part 74 of the measuring instrument comprises a motor 741, a belt pulley 742 provided on the output shaft of the motor 741, and a transmission belt 743 wrapped around the belt pulley 742 and the stand 731. When the motor 741 rotates the belt pulley 742, the rotational force is transmitted to the stand 731 via the transmission belt 743. As a result, the support arm 732 rotates around the stand 731.

[0091] When the support arm 732 rotates, the position of the sensor 733 in the radial direction of the chuck table 31 changes. This allows the thickness of the wafer 90 to be measured at multiple locations in the radial direction. In particular, the thickness measuring device 73 allows for the flexible selection of thickness measurement locations in the radial direction of the wafer 90 according to the rotation position of the support arm 732, regardless of the number of sensors. Therefore, thickness values ​​for calculating the thickness trend can be obtained at many locations in the radial direction, improving the accuracy of the thickness trend calculation.

[0092] In the thickness measuring device 73, the support arm 732 is rotated, but as a further modification, it is also possible to use a thickness measuring device in which the support arm 732 slides radially on the chuck table 31.

[0093] The thickness measuring instrument used to calculate the thickness trend of the wafer 90 may be placed in a different position from the thickness measuring instrument 72 of the grinding apparatus 1 in Figure 1. For example, the thickness measuring instrument may be placed in a position on the chuck table 31 at the loading / unloading position on the turntable 30 (a position where transport by the loading mechanism 20 and the unloading mechanism 23 is possible) in which the thickness of the wafer 90 can be measured. Alternatively, the thickness measuring instrument may be placed in a position on the chuck table 31 at the first grinding position (a position where grinding is possible with the first grinding mechanism 50) in which the thickness of the wafer 90 can be measured.

[0094] Alternatively, the thickness trend of the wafer 90 may be calculated using a thickness measuring instrument not located in the grinding apparatus 1. In other words, the thickness of the initially ground wafer may be measured with an external thickness measuring instrument, and the measured thickness value may be input to a thickness value input unit provided in the grinding apparatus 1, thereby allowing the thickness trend calculation unit to calculate the wafer's thickness trend. Alternatively, the calculation of the wafer's thickness trend may be performed outside the grinding apparatus 1, and the grinding apparatus 1 may be equipped with a thickness trend input unit for inputting that thickness trend.

[0095] 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]

[0096] As described above, the grinding apparatus and wafer grinding method of the present invention have the effect of making the shape of the wafers ground by the first grinding wheel uniform (the wafers tending to have the same thickness) on multiple chuck tables, thereby making the grinding time and grinding amount of the second grinding wheel uniform. This is useful in grinding apparatuses and grinding methods that perform grinding at various stages, such as grinding wafers before device formation and grinding wafers on which devices have been formed. [Explanation of symbols]

[0097] 1: Grinding device 15: Positioning mechanism 18: Cleaning mechanism 20: Loading mechanism 23: Unloading mechanism 30: Turntable 31: Chuck Table 33: Tilt adjustment mechanism 35: Position adjustment unit 36:Fixed support part 37: Chuck Rotating Part 50: First Grinding Mechanism 51: First whetstone 52: First spindle 60: Second grinding mechanism 61: Second whetstone 62: Second spindle 70: Thickness measuring gauge 71: Thickness measuring gauge 72: Thickness measuring instrument 73: Thickness measuring instrument 74: Measuring instrument rotating part 80: Control Unit 81: First tilt control unit 82: Second tilt control unit 83: Thickness trend calculation unit 84: Calculation Unit 90: Wafer 312: Chuck Spindle 321: Holding surface 723: Sensor 724: Sensor 725: Sensor 733: Sensor 741: Motor S: Thickness measurement location Ta: Setting thickness tendency Tb: Grinding thickness trend Tc: Grinding thickness trend Td: Setting thickness tendency Te: Grinding thickness trend Tf: Grinding thickness tendency

Claims

1. A wafer grinding method comprising rotating a turntable on which multiple chuck tables for holding wafers are arranged, grinding the wafers held on the chuck tables with a first grinding wheel, and then grinding them to a predetermined thickness with a second grinding wheel, A holding step of holding the wafer in the chuck table, A tilt adjustment step in which the chuck spindle of the chuck table holding the wafer is adjusted to a predetermined angle with respect to the first spindle on which the first grinding wheel is mounted, A first grinding step in which the wafer held in the chuck table adjusted in the tilt adjustment step is ground with the first grinding wheel, A second tilt adjustment step involves adjusting the chuck spindle of the chuck table that holds the wafer ground in the first grinding step to a predetermined angle with respect to the second spindle on which the second grinding wheel is mounted, This consists of a second grinding step in which the wafer held in the chuck table, which has been adjusted in the second tilt adjustment step, is ground with the second grinding wheel, Prior to the first grinding step, there is an initial grinding step in which the wafer is ground with the first grinding wheel, A thickness measurement step which measures the thickness of the wafer ground in the radial direction at at least three locations in the initial grinding step, A thickness trend calculation step that calculates the thickness trend of the wafer from at least three thickness values ​​measured in the thickness measurement step, Includes, A wafer grinding method comprising: adjusting the tilt adjustment step to adjust the tilt of each chuck spindle of the chuck table relative to the first spindle so that the thickness trend calculated in the thickness trend calculation step matches a preset thickness trend.

2. A wafer grinding method according to claim 1, wherein the wafer ground in the initial grinding step is ground in the first grinding step.

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