Wafer grinding method

Abstract

To suppress thickness differences from occurring on a ground wafer partially.SOLUTION: In a holding surface correction processing step, an etching mechanism 40 corrects a shape of a holding surface 22 so that the shape has a surface shape similar to a surface shape of an upper surface of a wafer for trial-grinding ground in a trial-grinding step. This enables a holding part 21 of a chuck table 20 to be communicated with a suction source 201, in a grinding step, so that when the holding surface 22 suctions and holds a product wafer, the holding surface 22 becomes a substantially flat surface and a radial part of the holding surface 22 becomes parallel to a lower surface of a wafer grinding stone, which can suppress thickness differences from occurring partially on the product wafer ground by the wafer grinding stone. This enables the product wafer to be ground in an equal thickness.SELECTED DRAWING: Figure 7

Description

[Technical field]

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

[0002] In the wafer grinding method disclosed in Patent Documents 1 and 2, the tilt of the chuck table is adjusted to make the holding surface of the chuck table parallel to the bottom surface of the grinding wheel, thereby preventing thickness differences in the radial direction of the ground wafer. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2008-264913 A [Patent Document 2] JP 2013-119123 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, there are cases where the ground wafer has a small thickness difference in its circumferential direction, and such a thickness difference in the circumferential direction of the wafer is difficult to eliminate by adjusting the inclination of the chuck table.

[0005] One of the causes of the minute local thickness differences in the circumferential direction of the wafer is thought to be the self-grinding process, in which the holding surface is formed by grinding the chuck table with a table grinding wheel used for table grinding.

[0006] Self grinding is performed without connecting the chuck table to a suction source, whereas when grinding a wafer, the chuck table is connected to a suction source and the wafer is held by the holding surface, which is pressed by atmospheric pressure.

[0007] In other words, when comparing self-grinding with grinding a wafer, the chuck table is deformed, and this deformation may result in local thickness differences in the ground wafer.

[0008] Therefore, an object of the present invention is to suppress the occurrence of local thickness differences in a ground wafer. [Means for solving the problem]

[0009] The method for grinding a wafer according to the present invention (the present grinding method) is a method for grinding a wafer by connecting a chuck table attached to a table base to a suction source and grinding a wafer held by a holding surface of the chuck table with a wafer grinding wheel for wafer grinding, the method including a holding surface forming step of forming the holding surface by grinding the upper surface of the chuck table with the wafer grinding wheel or a table grinding wheel for table grinding in a state in which the chuck table is not connected to a suction source, a holding step of connecting the holding surface to a suction source and holding a wafer for test grinding by the holding surface, and a step of grinding the test grinding wafer held by suction on the holding surface in the holding step. the test grinding process includes a test grinding step of grinding a test wafer to a prescribed thickness by the wafer grinding wheel; a distribution measuring step of measuring a thickness distribution over the entire surface of the test grinding wafer ground in the test grinding step or an upper surface height distribution over the entire upper surface of the test grinding wafer; a holding surface correction processing step of correcting the holding surface used in the test grinding step based on the thickness distribution or upper surface height distribution measured in the distribution measuring step so as to obtain a holding surface having a surface shape similar to that of the upper surface of the test grinding wafer after grinding; and a grinding step of, after the holding surface correction processing step, holding a product wafer by suction onto the holding surface and grinding the product wafer to the prescribed thickness by the wafer grinding wheel.

[0010] In this grinding method, the holding surface of the chuck table may be formed from silicon, and in the holding surface correction processing step, etching gas that has been partially converted into plasma may be sprayed from an etching gas spray nozzle onto the holding surface, and correction processing may be performed on the holding surface by atmospheric pressure plasma etching.

[0011] In the holding surface correction processing step of the present grinding method, the holding surface may be corrected by grinding the holding surface with a small diameter grinding wheel having a diameter smaller than the radius of the holding surface. Effect of the Invention

[0012] In this grinding method, in the holding surface correction processing step, the shape of the holding surface 22 is corrected so that it has a surface shape similar to that of the upper surface of the trial grinding wafer ground in the trial grinding step. As a result, when the chuck table is connected to the suction source during the grinding step and the product wafer is suction-held by the holding surface, the holding surface becomes a substantially flat surface, and the radius portion of the holding surface becomes parallel to the lower surface of the wafer grinding wheel. This makes it possible to suppress the occurrence of partial thickness differences in the product wafer ground by the wafer grinding wheel. Therefore, it becomes possible to grind the product wafer to a uniform thickness. [Brief description of the drawings]

[0013] [Figure 1] 4A to 4C are explanatory diagrams showing the configuration of a grinding device and a holding surface forming process. [Diagram 2] FIG. [Diagram 3] FIG. 2 is a perspective view showing a chuck table and a table base of the table portion. [Figure 4] 11 is an explanatory diagram showing a holding step and a test grinding step. FIG. [Diagram 5] FIG. 11 is an explanatory diagram showing a distribution measurement process. [Figure 6] FIG. 6(a) is an explanatory diagram showing a wafer for test grinding after the test grinding, and FIG. 6(b) is an explanatory diagram showing the upper surface height distribution of the wafer for test grinding after the test grinding. [Figure 7] FIG. 11 is an explanatory diagram showing a holding surface correction processing step. [Figure 8] FIG. [Figure 9] 13 is an explanatory diagram showing another holding surface correction processing step. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] The grinding apparatus 1 shown in FIG. 1 includes a table unit 2 including a chuck table 20 that holds a product wafer 100 or a test grinding wafer 105 (see FIG. 2), a grinding mechanism 10 that grinds the product wafer 100 or the test grinding wafer 105, a grinding feed mechanism 80 that feeds the grinding mechanism 10 for grinding, and a control unit 7 that controls each component of the grinding apparatus 1.

[0015] 2 is a circular semiconductor wafer that is an object to be processed (workpiece) in the grinding apparatus 1. The product wafer 100 has an upper surface 101 that is the surface to be ground. The product wafer 100 is held on the chuck table 20 of the table unit 2 shown in FIG. 1 with the upper surface 101 facing upward, for example, via a protective tape (not shown).

[0016] In this embodiment, in addition to the product wafer 100, a trial grinding wafer 105 is used in the trial grinding process. The trial grinding wafer 105 has an upper surface 106 which is the surface to be ground. The trial grinding wafer 105 may be the same wafer as the product wafer 100.

[0017] As shown in FIG. 1, the grinding mechanism 10 includes a spindle 11 extending along the Z-axis direction, a spindle motor 12 that rotates the spindle 11, a wheel mount 13 connected to the lower end of the spindle 11, and a grinding wheel 15 that is removably attached to the lower surface of the wheel mount 13.

[0018] The spindle 11 is driven by the spindle motor 12 to rotate as indicated by an arrow 501. The wheel mount 13 is formed in a disk shape, is fixed to the lower end of the spindle 11, and is rotated by the rotation of the spindle 11. The wheel mount 13 supports a grinding wheel 15.

[0019] The grinding wheel 15 is formed to have approximately the same diameter as the wheel mount 13. The grinding wheel 15 includes an annular wheel base 16 made of a metal material. A plurality of wafer grinding wheels 17, each having an approximately rectangular parallelepiped shape, are arranged in an annular shape on the underside of the wheel base 16 all around the circumference.

[0020] The wafer grinding wheel 17 is rotated by the rotation of the spindle 11, and grinds the product wafer 100 or the test grinding wafer 105 held on the holding surface 22 of the chuck table 20. The wafer grinding wheel 17 is also used to form the holding surface of the chuck table 20, which will be described later.

[0021] The grinding feed mechanism 80 moves the grinding mechanism 10 having such a configuration along the Z-axis direction, which is the grinding feed direction.

[0022] The table portion 2 includes a chuck table 20 that holds a product wafer 100 or a test grinding wafer 105 by means of a holding surface 22 , and a table base 30 that supports the chuck table 20 .

[0023] 3, the chuck table 20 has a substantially disk-shaped frame 23, and a holding portion 21 made of a porous material is provided in a recess provided in the frame 23. The upper surface of the holding portion 21 serves as a holding surface 22 that suction-holds the product wafer 100 or the test grinding wafer 105. The holding surface 22 is formed by grinding the upper surface of the holding portion 21 of the chuck table 20 in a holding surface forming step described later. For example, the holding surface 22 is formed in a conical shape with the apex at the center, as shown in Fig. 1. In addition, a frame surface 24, which is the upper surface of the frame 23, surrounds the holding surface 22 and is formed to be on the same plane (flush) as the holding surface 22.

[0024] In this embodiment, the holding portion 21 is a porous member made of silicon. Therefore, the holding surface 22, which is the upper surface of the holding portion 21, is also made of silicon. Note that the holding portion 21 is not limited to a porous member made of silicon, and may be made of a dense body of silicon having a plurality of through holes. In this case, the holding surface 22 is also a surface made of silicon. Also, in the chuck table 20 made of a dense body of silicon having a plurality of through holes, the holding portion 21 and the frame body 23 may be integrally formed.

[0025] 1, the holding unit 21 is connected to a suction source 201 via a suction valve 35. When the holding unit 21 is in communication with the suction source 201 and a suction force from the suction source 201 is transmitted to a holding surface 22, which is the upper surface of the holding unit 21, the chuck table 20 can suction-hold the product wafer 100 or the test grinding wafer 105 by the holding surface 22. In this manner, in this embodiment, when the chuck table 20 (holding unit 21) is in communication with the suction source 201, the product wafer 100 or the test grinding wafer 105 can be held by the holding surface 22.

[0026] 3, the chuck table 20 includes an annular flange 25 fixed to the lower part of the frame body 23 and having an outer diameter larger than that of the frame body 23. The annular flange 25 has a plurality of through holes 26 formed at predetermined intervals in the circumferential direction for inserting the male screws 300 therethrough.

[0027] The table base 30 is a disk-shaped body configured to support the chuck table 20 by a support surface 31, which is its upper surface. A suction groove 32 and a suction port 33 penetrating the table base 30 are formed in the support surface 31 of the table base 30. The suction groove 32 and the suction port 33 are configured to face the bottom surface 27 of the chuck table 20 supported by the support surface 31. The suction groove 32 and the suction port 33 are used to transmit the suction force from the suction source 201 to the holding part 21 via a table suction path 29 (see FIG. 1) that penetrates the frame 23 of the chuck table 20 and leads to the holding part 21. In this embodiment, the suction port 33 is provided in the suction groove 32 at the center of the support surface 31.

[0028] Furthermore, a plurality of screw holes (female threads) 34 are formed in the support surface 31 of the table base 30 at positions corresponding to the through holes 26 of the chuck table 20. The bottom surface 27 of the chuck table 20 is abutted against the support surface 31 of the table base 30, and screws 300 are inserted into the through holes 26 from above the annular flange 25 and screwed into the screw holes 34 of the table base 30, thereby fixing the chuck table 20 to the table base 30. The bottom surface 27 of the chuck table 20 is brought into close contact with the support surface 31 of the table base 30 by tightening the screws 300 with a predetermined torque pressure.

[0029] 1, the grinding apparatus 1 is equipped with a table rotation mechanism 91. The table portion 2 including the chuck table 20 is rotated by the table rotation mechanism 91 around a table rotation axis 301 as shown by an arrow 502.

[0030] The grinding apparatus 1 also includes an inclination adjustment mechanism 93. The inclination adjustment mechanism 93 is for adjusting the inclination of the table portion 2 including the chuck table 20 (the inclination of the table rotation axis 301). The inclination adjustment mechanism 93 adjusts the inclination of the table rotation axis 301 so that, for example, a radius portion of the holding surface 22 of the chuck table 20 (or a wafer held on the holding surface 22) becomes parallel to the lower surface of the wafer grinding wheel 17.

[0031] Furthermore, the grinding apparatus 1 includes a table moving mechanism 95. This table moving mechanism 95 moves the chuck table 20 of the table portion 2 and the wafer grinding wheel 17 of the grinding mechanism 10 relatively in the Y-axis direction, which is a direction parallel to the holding surface 22. In this embodiment, the table moving mechanism 95 moves the table portion 2 including the chuck table 20 in the Y-axis direction relative to the grinding mechanism 10.

[0032] As shown in FIG. 4, the grinding apparatus 1 is also provided with a thickness measuring mechanism 60 having a first height measuring device 61, a second height measuring device 62, and a calculating unit 63.

[0033] The first height measuring device 61 can be disposed above the frame surface 24 of the chuck table 20, and is used to measure the height of the frame surface 24 (ie, the height of the holding surface 22). The second height measuring device 62 is used to come into contact with the upper surface of the wafer (product wafer 100 or test grinding wafer 105) held on the holding surface 22 and measure the height of the wafer. Then, the calculation unit 63 can calculate the thickness of the wafer based on the difference between the measured height of the wafer and the height of the holding surface 22.

[0034] The second height measuring device 62 can move along the radial direction of the wafer, and can also measure the height distribution of the upper surface of the wafer. When no wafer is held on the holding surface 22 of the chuck table 20, the second height measuring device 62 can also measure the height and height distribution of the holding surface 22 by coming into contact with the holding surface 22.

[0035] The control unit 7 of the grinding apparatus 1 includes a CPU that performs arithmetic processing according to a control program, and a storage medium such as a memory. The control unit 7 controls each of the above-mentioned members of the grinding apparatus 1 to comprehensively control each of the components of the grinding apparatus 1. For example, the control unit 7 controls each of the above-mentioned members of the grinding apparatus 1 to execute the wafer grinding method according to this embodiment.

[0036] The wafer grinding method is described below. This wafer grinding method involves connecting the chuck table 20 attached to the table base 30 to a suction source 201, and grinding the product wafer 100 held by the holding surface 22 of the chuck table 20 with a wafer grinding wheel 17 for wafer grinding.

[0037] [Holding surface forming process] In this process, the wafer grinding wheel 17 of the grinding mechanism 10 is used to grind the upper surface of the chuck table 20 (the upper surface of the holding portion 21 and the frame body 23) without connecting the chuck table 20 to the suction source 201, thereby forming the holding surface 22.

[0038] Specifically, as shown in FIG. 1, the control unit 7 closes the suction valve 35 to cut off communication between the holding unit 21 of the chuck table 20 and the suction source 201.

[0039] Thereafter, the control unit 7 uses the table moving mechanism 95 to place the table unit 2 including the chuck table 20 at a processing position below the grinding mechanism 10. At this processing position, the wafer grinding stone 17 of the grinding wheel 15 in the grinding mechanism 10 passes through the center of the holder 21 in the chuck table 20. In addition, the control unit 7 uses the tilt adjustment mechanism 93 to set the tilt of the table rotation axis 301, which is the rotation axis of the chuck table 20, to a predetermined value.

[0040] Then, while rotating the wafer grinding wheel 17 and the chuck table 20, the control unit 7 causes the grinding mechanism 10 to descend using the grinding feed mechanism 80, bringing the wafer grinding wheel 17 into contact with the upper surfaces of the holder 21 and frame 23 on the chuck table 20, and grinding these surfaces with the wafer grinding wheel 17. This grinding is performed so that the upper surface of the holder 21 becomes a conical holding surface 22 having a predetermined height and an apex at the center, and so that it is flush with the frame surface 24, which is the upper surface of the frame 23. As a result, the holding surface 22 is formed having a radius portion parallel to the lower surface of the wafer grinding wheel 17.

[0041] [Holding process] Next, a holding step is performed. In this step, the holding surface 22 of the chuck table 20 formed in the holding surface forming step is connected to the suction source 201, and the test grinding wafer 105 (see FIG. 2) is held by suction using the holding surface 22.

[0042] Specifically, the control unit 7 uses the table moving mechanism 95 to place the table unit 2 including the chuck table 20 at a predetermined holding position away from below the grinding mechanism 10. Next, the control unit 7 or an operator places the test grinding wafer 105 on the holding surface 22 of the chuck table 20 with the upper surface 106 facing upward. Thereafter, the control unit 7 opens the suction valve 35 to connect the holding unit 21 of the chuck table 20 to the suction source 201. As a result, the test grinding wafer 105 is suction-held by the holding surface 22, which is the upper surface of the holding unit 21, as shown in FIG.

[0043] [Trial grinding process] Next, a test grinding step is performed in which the test grinding wafer 105, which has been suction-held on the holding surface 22 in the holding step, is ground to a predetermined thickness by the wafer grinding wheel 17.

[0044] Specifically, the control unit 7 places the table unit 2 including the chuck table 20 that suction-holds the test grinding wafer 105 at the above-mentioned processing position below the grinding mechanism 10 by the table moving mechanism 95. At this processing position, the wafer grinding wheel 17 of the grinding mechanism 10 passes through the center of the holding surface 22 of the chuck table 20. Then, while rotating the wafer grinding wheel 17 and chuck table 20 of the grinding mechanism 10, the control unit 7 lowers the grinding mechanism 10 by the grinding feed mechanism 80, and brings the wafer grinding wheel 17 into contact with the radius portion of the upper surface 106 of the test grinding wafer 105 held on the holding surface 22, and grinds this upper surface 106 with the wafer grinding wheel 17. At this time, the control unit 7 uses the thickness measuring mechanism 60 to measure the thickness of the test grinding wafer 105 being ground, and continues this test grinding until the thickness of the test grinding wafer 105 reaches a predetermined thickness.

[0045] [Distribution measurement process] Next, a distribution measurement step is performed, in which the thickness distribution over the entire surface of the test grinding wafer 105 ground in the test grinding step is measured.

[0046] In this step, a non-contact thickness measuring mechanism 70 as shown in Fig. 5 is used. The non-contact thickness measuring mechanism 70 is provided in the grinding apparatus 1, and has a non-contact thickness measuring device 71 and a moving unit 72 that moves the non-contact thickness measuring device 71 in the horizontal and vertical directions.

[0047] The non-contact thickness gauge 71 measures, in a non-contact manner, the thickness of a wafer (product wafer 100 or test grinding wafer 105) held on the chuck table 20. For example, the non-contact thickness gauge 71 irradiates the wafer with measurement light having a wavelength that is transparent to the wafer from above, receives the upper surface reflected light reflected from the upper surface of the wafer and the lower surface reflected light reflected from the lower surface of the wafer through the wafer, and measures the thickness of the wafer by spectral interference.

[0048] Then, in the distribution measuring step, the control unit 7 uses the non-contact thickness measuring mechanism 70 to measure the thickness distribution over the entire surface of the test grinding wafer 105 ground in the test grinding step.

[0049] Specifically, the control unit 7 measures the thickness of the test grinding wafer 105 with the non-contact thickness gauge 71 while gradually rotating the chuck table 20 with the table rotation mechanism 91 and gradually moving the non-contact thickness gauge 71 in the radial direction of the test grinding wafer 105 with the movement unit 72. This allows the control unit 7 to calculate the thickness distribution over the entire surface of the test grinding wafer 105.

[0050] In addition, when measuring the thickness distribution of the test grinding wafer 105, the control unit 7 may control the inclination of the chuck table 20 using the inclination adjustment mechanism 93 to make the portion of the upper surface 106 of the test grinding wafer 105 below the non-contact thickness measurement mechanism 70 (the portion where the thickness is measured) horizontal.

[0051] [Holding surface modification process] Next, a holding surface correction process is carried out. In this process, correction processing is performed on the holding surface 22 used in the trial grinding process so as to obtain a holding surface 22 having a surface shape (similar shape) similar to that of the upper surface 106 of the trial grinding wafer 105 after grinding, based on the thickness distribution measured in the distribution measurement process.

[0052] Specifically, the control unit 7 first obtains the height distribution of the upper surface 106 of the test grinding wafer 105 after the test grinding step based on the thickness distribution of the test grinding wafer 105 measured in the distribution measuring step.

[0053] 6(a) shows the height distribution (top surface height distribution) of the top surface 106 of the test grinding wafer 105 after the test grinding process. In this figure, the top surface height distribution is shown by contour lines L. As shown in this figure, minute height differences (corresponding to thickness differences of the test grinding wafer 105) occur partially in the circumferential and radial directions on the top surface 106 of the test grinding wafer 105 after grinding.

[0054] One of the causes is considered to be that, for example, when the chuck table 20 is connected to the suction source 201 in the trial grinding step and the trial grinding wafer 105 is suction-held by the holding surface 22, the holding surface 22 is pressed by atmospheric pressure, causing partial deformation (uneven portion) of the holding surface 22 formed in the holding surface forming step, resulting in a portion in the radius portion of the holding surface 22 that is not parallel to the lower surface of the wafer grinding wheel 17. In other words, it is considered that a thickness difference (height difference) occurred in the trial grinding wafer 105 after grinding because the trial grinding wafer 105 was held by the uneven holding surface 22 and trial grinding was performed.

[0055] Therefore, in the holding surface correction processing step, the control unit 7 corrects the holding surface 22 so that the holding surface 22 becomes a substantially flat surface when the product wafer 100 is later held by suction. That is, as shown in Fig. 6(b), the holding surface 22 is corrected to match the upper surface height distribution H of the test grinding wafer 105, thereby correcting the shape of the holding surface 22 to a surface shape similar to that of the upper surface 106 of the test grinding wafer 105 (a shape having the same upper surface height distribution as the upper surface 106). As a result, when the chuck table 20 is connected to the suction source 201 and the product wafer 100 is suction-held by the holding surface 22, the holding surface 22 can be made a substantially flat surface.

[0056] For this correction process, for example, an etching mechanism 40 provided in the grinding device 1 as shown in FIG. 7 is used. The etching mechanism 40 has an injection nozzle (etching gas injection nozzle) 41 that injects an etching gas, a lifting unit 42 that raises and lowers the injection nozzle 41 along the Z-axis direction, and a horizontal movement unit 43 that moves the injection nozzle 41 and the lifting unit 42 in the horizontal direction. In this embodiment, an etching gas (SF6 or CF4) that has been converted into plasma is injected from the injection nozzle 41.

[0057] In the holding surface correction processing step, the control unit 7 first uses the table moving mechanism 95 to place the table unit 2 including the chuck table 20 in a correction processing position (which may be the same position as the holding position) away from the processing position below the grinding mechanism 10. Thereafter, the control unit 7 or an operator removes the test grinding wafer 105 from the holding surface 22 of the chuck table 20.

[0058] Next, the control unit 7 controls the lifting unit 42 and horizontal movement unit 43 of the etching mechanism 40 to position the jet nozzle 41 above the holding surface 22 of the chuck table 20. Then, the control unit 7 changes the position of the jet nozzle 41 by the horizontal movement unit 43 and the lifting unit 42 in accordance with the upper surface height distribution of the test grinding wafer 105, while jetting the etching gas that has been converted into plasma from the jet nozzle 41 partially onto the holding surface 22, thereby performing correction processing on the holding surface 22 by atmospheric pressure plasma etching.

[0059] By such correction processing, the shape of the holding surface 22 is corrected to a surface shape similar to that of the upper surface 106 of the test grinding wafer 105. In other words, the holding surface 22 has a height distribution as shown in FIG.

[0060] [Grinding process] Next, a grinding step is performed on the workpiece, that is, the product wafer 100. In this step, after the holding surface correction processing step, the product wafer 100 is sucked and held on the holding surface 22, and the product wafer 100 is ground to a predetermined thickness by the wafer grinding wheel 17.

[0061] Specifically, the control unit 7 places the table unit 2 including the chuck table 20 at the above-mentioned predetermined holding position using the table moving mechanism 95. Next, the control unit 7 or an operator places the product wafer 100 on the holding surface 22 of the chuck table 20 with the upper surface 101 facing upward. Thereafter, the control unit 7 opens the suction valve 35 to connect the holding surface 22 to the suction source 201. As a result, the product wafer 100 is suction-held by the holding surface 22, as shown in FIG.

[0062] Next, the control unit 7 places the table unit 2 including the chuck table 20 holding the product wafer 100 by suction at the above-mentioned processing position by the table moving mechanism 95. Then, while rotating the wafer grinding wheel 17 and the chuck table 20 of the grinding mechanism 10, the control unit 7 lowers the grinding mechanism 10 by the grinding feed mechanism 80, and brings the wafer grinding wheel 17 into contact with the radius portion of the upper surface 101 of the product wafer 100 held on the holding surface 22, and grinds the upper surface 101 with the wafer grinding wheel 17. At this time, the control unit 7 measures the thickness of the product wafer 100 being ground by the thickness measuring mechanism 60, and continues grinding until the thickness of the product wafer 100 reaches a predetermined thickness.

[0063] As described above, in this embodiment, in the holding surface correction processing step, the shape of the holding surface 22 is corrected to have a surface shape similar to that of the upper surface 106 of the trial grinding wafer 105 ground in the trial grinding step. As a result, during the grinding step, when the holding portion 21 of the chuck table 20 is connected to the suction source 201 and the product wafer 100 is suction-held by the holding surface 22, the holding surface 22 becomes a substantially flat surface, and the radius portion of the holding surface 22 becomes parallel to the lower surface of the wafer grinding wheel 17. Therefore, it is possible to suppress the occurrence of partial thickness differences in the product wafer 100 ground by the wafer grinding wheel 17. Therefore, it is possible to grind the product wafer 100 to a uniform thickness.

[0064] In the above-mentioned distribution measuring step, the thickness distribution of the entire surface of the trial grinding wafer 105 ground in the trial grinding step is measured. In this regard, in the distribution measuring step in this embodiment, the height distribution of the entire surface of the upper surface 106 of the trial grinding wafer 105 ground in the trial grinding step may be measured.

[0065] In this case, after the test grinding process, the control unit 7 or an operator removes the test grinding wafer 105 from the chuck table 20 and holds it on a flat table (not shown) equipped with a height gauge such as the second height gauge 62 of the thickness measurement mechanism 60. Then, the control unit 7 measures the height of the upper surface 106 of the test grinding wafer 105 by using the height gauge while gradually rotating the table holding the test grinding wafer 105 and gradually moving the height gauge in the radial direction. This allows the control unit 7 to obtain the height distribution (upper surface height distribution) of the entire surface of the upper surface 106 of the test grinding wafer 105.

[0066] In this case, in the holding surface correction processing step, the control unit 7 performs correction processing on the holding surface 22 used in the trial grinding process so as to obtain a holding surface 22 having a surface shape similar to that of the upper surface 106 of the trial grinding wafer 105 after grinding, based on the upper surface height distribution measured in the distribution measurement process.

[0067] In this manner, in the distribution measuring step, the thickness distribution over the entire surface of the trial grinding wafer 105 ground in the trial grinding step or the height distribution over the entire surface of the upper surface 106 may be measured. Also, in the holding surface correcting process step, based on the thickness distribution or upper surface height distribution measured in the distribution measuring step, correction processing may be performed on the holding surface 22 used in the trial grinding step so as to obtain a holding surface 22 having a surface shape (similar shape) similar to the upper surface 106 of the trial grinding wafer 105 after grinding.

[0068] 7, or in addition to the etching mechanism 40, the grinding device 1 may include a holding surface correction grinding mechanism 50 as shown in FIG. 9. The holding surface correction grinding mechanism 50 includes a small diameter grinding wheel unit 51, a lifting unit 52 that lifts and lowers the small diameter grinding wheel unit 51 along the Z-axis direction, and a horizontal movement unit 53 that moves the small diameter grinding wheel unit 51 and the lifting unit 52 horizontally. The small diameter grinding wheel unit 51 includes a small diameter grinding wheel 511 and a motor 512 that rotates the small diameter grinding wheel 511. The small diameter grinding wheel 511 has a diameter smaller than the radius of the holding surface 22 of the chuck table 20.

[0069] In this case, the control unit 7 may use the holding surface correction grinding mechanism 50 to perform correction processing on the holding surface 22 of the chuck table 20 in the correction processing step. In this case, in the holding surface correction processing step, after the test grinding wafer 105 is removed from the holding surface 22, the control unit 7 controls the lifting unit 52 and the horizontal movement unit 53 of the holding surface correction grinding mechanism 50 to place the small diameter grinding wheel unit 51 on the holding surface 22 of the chuck table 20. Then, the control unit 7 performs correction processing on the holding surface 22 by, for example, partially grinding the holding surface 22 with the small diameter grinding wheel 511 of the small diameter grinding wheel unit 51 while changing the position of the small diameter grinding wheel unit 51 by the lifting unit 52 and the horizontal movement unit 53 in accordance with the upper surface height distribution of the test grinding wafer 105 (see FIGS. 6(a) and (b)).

[0070] By such correction processing, the shape of the holding surface 22 is corrected to the same surface shape as the upper surface 106 of the test grinding wafer 105, in the same way as in the case where the etching mechanism 40 is used.

[0071] In addition, when the holding surface 22 is modified using the holding surface modification grinding mechanism 50, the holding surface 22 (holding portion 21) of the chuck table 20 may be formed from silicon or from other materials (such as alumina-based porous ceramics).

[0072] In addition, when the holding surface is modified in the holding surface modification process, the control unit 7 may control the inclination of the chuck table 20 using the inclination adjustment mechanism 93 to make the portion of the holding surface 22 located below the etching mechanism 40 or the holding surface modification grinding mechanism 50 horizontal.

[0073] In the above-described embodiment, the holding surface 22 of the chuck table 20 is formed using the wafer grinding wheel 17 of the grinding mechanism 10 in the holding surface forming step. In this regard, in the holding surface forming step, a table grinding wheel 18 (see FIG. 1) for table grinding, which is a grinding wheel for grinding the chuck table 20, may be used instead of the wafer grinding wheel 17. In this case, in the holding surface forming step, the worker attaches a table grinding wheel 19 including the table grinding wheel 18 to the wheel mount 13 instead of the grinding wheel 15.

[0074] Therefore, in the holding surface forming process of this embodiment, the holding surface 22 may be formed by grinding the upper surface of the chuck table 20, including the holding portion 21, using the wafer grinding wheel 17 or the table grinding wheel 18 of the grinding mechanism 10 without connecting the chuck table 20 to the suction source 201. [Explanation of symbols]

[0075] 1: grinding device, 2: table unit, 7: control unit, 10: grinding mechanism, 11: spindle, 12: spindle motor, 13: wheel mount, 15: grinding wheel, 16: wheel base, 17: wafer grinding wheel, 18: Table grinding wheel, 19: Table grinding wheel, 20: Chuck table, 21: holding portion, 22: holding surface, 23: frame, 24: frame surface, 25: annular flange, 26: through hole, 27: bottom surface, 29: table suction passage, 30: table base, 31: support surface, 32: suction groove, 33: suction port, 34: screw hole, 35: suction valve, 40: etching mechanism, 41: injection nozzle, 42: lifting unit, 43: horizontal movement unit, 50: retaining surface correction grinding mechanism, 51: small diameter grinding wheel unit, 52: lifting unit, 53: horizontal movement unit, 60: thickness measurement mechanism, 61: first height measurement device, 62: second height measuring device, 63: calculation unit, 70: non-contact thickness measuring mechanism, 71: non-contact thickness measuring device, 72: moving unit, 80: grinding feed mechanism, 91: table rotation mechanism, 93: tilt adjustment mechanism, 95: table movement mechanism, 100: product wafer, 101: top surface, 105: wafer to be ground, 106: top surface, 201: suction source, 300: screw, 301: table rotation axis, 511: Small diameter grinding wheel, 512: Motor, H: Top surface height distribution, L: Contour line

Claims

1. A method for grinding a wafer, comprising: connecting a chuck table attached to a table base to a suction source; and grinding a wafer held by a holding surface of the chuck table through suction with a wafer grinding wheel for grinding the wafer, the method comprising the steps of: a holding surface forming step of forming the holding surface by grinding an upper surface of the chuck table using the wafer grinding wheel or a table grinding wheel for table grinding in a state where the chuck table is not connected to a suction source; a holding step of connecting the holding surface to a suction source and holding the test grinding wafer by the holding surface; a test grinding step of grinding the test grinding wafer held by suction on the holding surface in the holding step to a predetermined thickness by the wafer grinding wheel; a distribution measuring step of measuring a thickness distribution over the entire surface of the test grinding wafer ground in the test grinding step, or a top surface height distribution over the entire top surface of the test grinding wafer; a holding surface correction process for performing correction processing on the holding surface used in the test grinding process so as to obtain the holding surface having a surface shape similar to that of the upper surface of the test grinding wafer after grinding, based on the thickness distribution or upper surface height distribution measured in the distribution measurement process; a grinding step in which, after the holding surface correction processing step, a product wafer is sucked and held on the holding surface, and the product wafer is ground to a predetermined thickness by the wafer grinding wheel; A method for grinding a wafer, comprising:

2. the holding surface of the chuck table is made of silicon; In the holding surface correction process, an etching gas that has been converted into plasma is sprayed from an etching gas spray nozzle onto a part of the holding surface, and the holding surface is corrected by atmospheric pressure plasma etching.

2. The method for grinding a wafer according to claim 1.

3. In the holding surface correction processing step, the holding surface is ground with a small diameter grinding wheel having a diameter smaller than the radius of the holding surface, thereby performing correction processing on the holding surface.

2. The method for grinding a wafer according to claim 1.

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