Method for grinding laminated wafer

Abstract

To grind one of laminated wafers with a uniform thickness.SOLUTION: In a holding surface correction machining step, a shape of a holding surface 22 is corrected to a surface shape symmetrical to the upper surface of an oxide film in laminated wafers. Thus, in a grinding step, when a holding part 21 of a chuck table 20 is communicated with a suction source 201, and a first wafer of the wafers is sucked and held on the holding surface 22, the upper surface of the oxide film and the upper surface of a second wafer become substantially planar, and parallel with the lower surface of a grindstone. Thus, the occurrence of a partial thickness difference on the second wafer ground by the grindstone can be suppressed well. Therefore, the second wafer can be ground with a uniform thickness.SELECTED DRAWING: Figure 7

Description

[Technical field]

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

[0002] As disclosed in Patent Documents 1 to 3, there is a bonded wafer in which two wafers are bonded together with an oxide film. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2009-176918 A [Patent Document 2] JP 2015-070013 A [Patent Document 3] JP 2016-004799 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the above-mentioned bonded wafer, as disclosed in Patent Document 1, the oxide film does not have a uniform thickness. That is, the oxide film has a uniform thickness in the center of the wafer, while the oxide film has a ring-shaped thickness in the outer periphery of the wafer, which is thicker than the center. When one of the two wafers bonded together with such an oxide film is ground with a grinding wheel, the thickness of the outer periphery of the one wafer becomes thinner than the center, making it difficult to make the ground wafer have a uniform thickness.

[0005] SUMMARY OF THE PRESENT EMBODIMENTS Accordingly, an object of the present invention is to provide one of the wafers of a bonded wafer with a uniform thickness when the one wafer is ground. [Means for solving the problem]

[0006] A first bonded wafer grinding method (first grinding method) of the present invention is a method for grinding a bonded wafer in which a first wafer and a second wafer of uniform thickness are bonded together via an oxide film, the first wafer of the bonded wafer is held on a holding surface of a chuck table, and the second wafer is ground with a grinding wheel, the method including: an oxide film thickness distribution measuring step of measuring a thickness distribution of the entire surface of the oxide film by irradiating the bonded wafer with light having a wavelength that is transparent to the oxide film and the wafer on the light incident side of the first wafer or the second wafer; a holding surface correction processing step of processing the holding surface based on the thickness distribution of the entire surface of the oxide film measured in the oxide film thickness distribution measuring step; and a grinding step of holding the first wafer of the bonded wafer on the holding surface, and grinding the second wafer of the bonded wafer with the grinding wheel after the holding surface correction processing step.

[0007] A second bonded wafer grinding method (second grinding method) of the present invention is a method for grinding a bonded wafer, in which a first wafer and a second wafer of uniform thickness are bonded together via an oxide film, the first wafer of the bonded wafer is held on a holding surface of a chuck table, and the second wafer is ground with a grinding wheel, in which the first wafer is held by the holding surface of the chuck table, and light having a wavelength that is transparent to the second wafer is irradiated onto the bonded wafer to measure the height distribution of the entire top surface of the oxide film. the step of measuring an oxide film upper surface height distribution; a bonded wafer separating step of separating the bonded wafer from the holding surface of the chuck table; a holding surface correction processing step of processing the holding surface exposed by the bonded wafer separating step based on the height distribution of the entire upper surface of the oxide film measured in the oxide film upper surface height distribution measuring step; and a grinding step of holding the first wafer of the bonded wafer on the holding surface and grinding the second wafer of the bonded wafer with the grinding wheel after the holding surface correction processing step.

[0008] In the first grinding method and the second 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.

[0009] In the holding surface correction processing step in the first grinding method and the second 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

[0010] In the first grinding method and the second grinding method, in the holding surface correction processing step, the shape of the holding surface is corrected, for example, to have a surface shape symmetrical to the upper surface of the oxide film based on the thickness distribution or upper surface height distribution of the oxide film on the bonded wafer. As a result, when the first wafer of the bonded wafer is suction-held by the holding surface of the chuck table during the grinding step, the upper surface of the oxide film and the upper surface of the second wafer become substantially flat and parallel to the lower surface of the grinding wheel. This makes it possible to effectively suppress the occurrence of partial thickness differences in the second wafer ground by the grinding wheel.

[0011] Therefore, it is possible to grind the second wafer of the bonded wafer to a uniform thickness. Therefore, by manufacturing a laminated wafer using the bonded wafer, the laminated wafer can be stacked and formed to a uniform thickness. In addition, since it is not necessary to spend time on the polishing process for making the thickness of the oxide film uniform by polishing, it is possible to shorten the processing time for manufacturing the laminated wafer including the bonded wafer, and productivity can be improved. [Brief description of the drawings]

[0012] [Figure 1] FIG. 2 is an explanatory diagram showing a configuration of a grinding device. [Diagram 2]FIG. 2 is an explanatory diagram showing a configuration of a bonded wafer. [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 bonded wafer separating step. FIG. [Diagram 5] FIG. 11 is an explanatory diagram showing an oxide film thickness distribution measuring step. [Figure 6] FIG. 4 is an explanatory diagram showing the height distribution of the upper surface of an oxide film. [Figure 7] FIG. 11 is an explanatory diagram showing a holding surface correction processing step. [Figure 8] FIG. 11 is an explanatory diagram showing an oxide film upper surface height distribution measuring step. [Figure 9] 13 is an explanatory diagram showing another holding surface correction processing step. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] The grinding apparatus 1 shown in FIG. 1 includes a table unit 2 including a chuck table 20 for holding a workpiece, a grinding mechanism 10 for grinding the workpiece, a grinding feed mechanism 80 for feeding the grinding mechanism 10 for grinding, and a control unit 7 for controlling each component of the grinding apparatus 1.

[0014] In this embodiment, the grinding apparatus 1 processes a bonded wafer 100 as shown in Fig. 2. The bonded wafer 100 is an example of a workpiece, and is a bonded wafer in which a first wafer 110 and a second wafer 120 of uniform thickness are bonded together via an oxide film 105. That is, in the bonded wafer 100, the first wafer 110, the oxide film 105, and the second wafer 120 are laminated in this order. The oxide film 105 has an upper surface 106 that faces the second wafer 120, and a lower surface 107 that faces the first wafer 110.

[0015] 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.

[0016] 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.

[0017] 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 grinding stones 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.

[0018] The grinding wheel 17 is rotated by the rotation of the spindle 11 and grinds the bonded wafer 100 held on the holding surface 22 of the chuck table 20 .

[0019] 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.

[0020] The table portion 2 includes a chuck table 20 that holds the bonded wafer 100 by a holding surface 22 , and a table base 30 that supports the chuck table 20 .

[0021] 3, the chuck table 20 has a substantially disk-shaped frame 23, and has a holding portion 21 made of a porous material in a recess provided in the frame 23. The upper surface of the holding portion 21 serves as a holding surface 22 that holds the bonded wafer 100 by suction.

[0022] The holding surface 22 is formed by grinding the upper surface of the holding portion 21 of the chuck table 20. 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.

[0023] 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. In addition, 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.

[0024] 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 bonded wafer 100 by the holding surface 22. In this embodiment, the chuck table 20 holds the first wafer 110 of the bonded wafer 100 such that the second wafer 120 is on the upper side.

[0025] 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.

[0026] 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.

[0027] 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 the second wafer 120 of the bonded wafer 100 held on the holding surface 22) becomes parallel to the lower surface of the grinding wheel 17.

[0031] Furthermore, the grinding device 1 includes a table movement mechanism 95. This table movement mechanism 95 moves the chuck table 20 of the table portion 2 and the 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 movement 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. 1, 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).

[0034] The second height measuring device 62 is used to come into contact with the upper surface of the second wafer 120 of the bonded wafer 100 held on the holding surface 22 and measure the height of the bonded wafer 100 .

[0035] Then, the calculation unit 63 can calculate the thickness of the bonded wafer 100 based on the difference between the measured height of the bonded wafer 100 and the height of the holding surface 22.

[0036] The second height measuring device 62 can move along the radial direction of the bonded wafer 100, and can also measure the height distribution of the upper surface of the second wafer 120 in the bonded wafer 100. When the bonded wafer 100 is not 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.

[0037] 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 grinding method for a bonded wafer according to this embodiment.

[0038] The first bonded wafer grinding method (first grinding method) according to this embodiment will be described below. This grinding method is a method for grinding a bonded wafer in which the first wafer 110 of a bonded wafer 100, in which a first wafer 110 and a second wafer 120 of uniform thickness are bonded together with an oxide film 105 interposed therebetween, is held on the holding surface 22 of a chuck table 20, and the second wafer 120 is ground by a grinding wheel 17.

[0039] [First grinding method] [Oxide film thickness distribution measurement process] In the first grinding method, first, an oxide film thickness distribution measuring step is performed. In this step, the bonded wafer 100 is irradiated with light having a wavelength that is transparent to the second wafer 120 and the oxide film 105 of the bonded wafer 100, and the thickness distribution of the entire surface of the oxide film 105 is measured.

[0040] In this process, first, a holding step is performed. In the holding step, the holding surface 22 of the chuck table 20 is connected to the suction source 201, and the first wafer 110 of the bonded wafer 100 (see FIG. 2) is held by the holding surface 22.

[0041] Specifically, the control unit 7 places the table unit 2 including the chuck table 20 at a predetermined holding position away from below the grinding mechanism 10 by the table moving mechanism 95. Next, the control unit 7 places the bonded wafer 100 on the holding surface 22 of the chuck table 20 by using the transfer device 45 as shown in FIG.

[0042] The transport device 45 is provided in, for example, the grinding device 1, and includes a transport pad 46 capable of holding the bonded wafer 100, and a moving mechanism 47 for moving the transport pad 46. The control unit 7 uses the transport device 45 to place the first wafer 110 of the bonded wafer 100 on the holding surface 22 of the chuck table 20 so that the second wafer 120 faces 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 first wafer 110 is suction-held by the holding surface 22, which is the upper surface of the holding unit 21, as shown in FIG. 5.

[0043] Next, a measuring step is performed to measure the thickness distribution of the oxide film 105 on the bonded wafer 100. In the measuring step, the thickness distribution of the entire surface of the oxide film 105 on the bonded wafer 100 held on the chuck table 20 is measured.

[0044] For this measurement, a non-contact thickness measurement mechanism 70 as shown in Fig. 5 is used. The non-contact thickness measurement mechanism 70 is provided, for example, in the grinding apparatus 1, and has a non-contact thickness measurement device 71 and a moving unit 72 that moves the non-contact thickness measurement device 71 in the horizontal and vertical directions.

[0045] The non-contact thickness gauge 71 measures the thickness of the oxide film 105 of the bonded wafer 100 held on the chuck table 20 in a non-contact manner. The non-contact thickness gauge 71 irradiates the bonded wafer 100 from above the second wafer 120 in the bonded wafer 100, for example, with measurement light having a wavelength that is transparent to the second wafer 120 and the oxide film 105, from the second wafer 120 side. The non-contact thickness gauge 71 then receives the upper surface reflected light reflected by the upper surface 106 of the oxide film 105 through the second wafer 120 and the lower surface reflected light reflected by the lower surface 107 of the oxide film 105 through the second wafer 120 and the oxide film 105, and measures the thickness of the oxide film 105 by spectral interference.

[0046] Then, the control unit 7 uses the non-contact thickness measuring mechanism 70 to measure the thickness distribution over the entire surface of the oxide film 105 .

[0047] Specifically, the control unit 7 measures the thickness of the oxide film 105 by the non-contact thickness gauge 71 while rotating the chuck table 20 little by little by the table rotation mechanism 91 and moving the non-contact thickness gauge 71 little by little in the radial direction of the bonded wafer 100 by the moving unit 72. In this way, the control unit 7 can calculate the thickness distribution of the oxide film 105 over the entire surface.

[0048] When measuring the thickness distribution of the oxide film 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 of the second wafer 120 below the non-contact thickness gauge 71 (the portion where the thickness of the oxide film 105 is measured) horizontal.

[0049] [Bonded Wafer Separation Process] Next, a bonded wafer separating step is performed. In this step, the control unit 7 separates the bonded wafer 100 from the holding surface 22 of the chuck table 20. Specifically, the control unit 7 closes the suction valve 35 and releases the suction of the bonded wafer 100 by the holding surface 22 by, for example, supplying water and / or air to the holding surface 22. Thereafter, the control unit 7 holds the bonded wafer 100 on the holding surface 22 using the transfer device 45 shown in FIG. 4, and separates (transports) it from the holding surface 22. This exposes the holding surface 22.

[0050] [Holding surface modification process] Next, a support surface correction process is performed, in which the support surface 22 is corrected based on the thickness distribution of the oxide film 105 over the entire surface measured in the oxide film thickness distribution measurement process.

[0051] Specifically, the control unit 7 first obtains the height distribution over the entire surface of the upper surface 106 of the oxide film 105 based on the thickness distribution over the entire surface of the oxide film 105 measured in the oxide film thickness distribution measuring process.

[0052] 6 shows an example of the height distribution (top surface height distribution) H of the top surface 106 of the oxide film 105. In the example shown in this figure, the height of the top surface 106 of the oxide film 105 is higher in the outer periphery compared to near the center of the bonded wafer 100. This is because the oxide film 105 has a uniform thickness in the center of the first wafer 110, but is ring-shaped and thicker in the outer periphery of the first wafer 110 than in the center.

[0053] Therefore, in the holding surface correction process, the control unit 7 corrects the holding surface 22 so that the upper surface 106 of the oxide film 105 and the upper surface of the upper second wafer 120 become substantially flat when the bonded wafer 100 is suction-held by the holding surface 22. That is, as shown in FIG. 6, the holding surface 22 is corrected based on the upper surface height distribution H of the oxide film 105 to correct the shape of the holding surface 22, for example, to a surface shape symmetrical to the upper surface 106 of the oxide film 105 (a shape having a height distribution symmetrical to the upper surface 106). For example, the holding surface 22 is corrected by lowering the outer peripheral portion of the holding surface 22 corresponding to the ring-shaped thick outer peripheral portion of the oxide film 105 so that the sum of the height of the holding surface 22 and the height of the upper surface 106 of the oxide film 105 is substantially equal over the entire surface of the oxide film 105. As a result, when the chuck table 20 is connected to the suction source 201 and the first wafer 110 of the bonded wafer 100 is held by suction by the holding surface 22, the upper surface 106 of the oxide film 105 and the upper surface of the second wafer 120 can be made substantially flat.

[0054] For this correction process, for example, an etching mechanism 40 provided in the grinding device 1 as shown in FIG. 7 is used.

[0055] The etching mechanism 40 is provided in, for example, the grinding device 1, and 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 made into plasma is injected from the injection nozzle 41.

[0056] Then, in the holding surface correction processing process, the control unit 7 first uses the table moving mechanism 95 to position the table portion 2 including the chuck table 20 at a correction processing position (which may be the same position as the holding position) away from the processing position below the grinding mechanism 10.

[0057] Next, the control unit 7 controls the lifting unit 42 and horizontal movement unit 43 of the etching mechanism 40 to position the injection nozzle 41 above the holding surface 22 of the chuck table 20. Then, the control unit 7 changes the position of the injection nozzle 41 using the horizontal movement unit 43 and the lifting unit 42 based on the upper surface height distribution of the oxide film 105, while injecting the etching gas that has been converted into plasma from the injection nozzle 41 partially onto the holding surface 22, thereby correcting the holding surface 22 by atmospheric pressure plasma etching.

[0058] By such correction processing, the shape of the support surface 22 is corrected to a surface shape symmetrical with respect to the upper surface 106 of the oxide film 105. That is, the support surface 22 comes to have a height distribution as shown in FIG.

[0059] [Grinding process] Next, a grinding step is performed on the bonded wafer 100. In this step, after the holding surface correction processing step, the first wafer 110 of the bonded wafer 100 is held on the holding surface 22, and the second wafer 120 of the bonded wafer 100 is ground by the grinding wheel 17.

[0060] Specifically, the control unit 7 uses the table moving mechanism 95 to place the table unit 2 including the chuck table 20 at the above-mentioned predetermined holding position. Next, the control unit 7 uses the transfer device 45 shown in FIG. 4 to place the first wafer 110 of the bonded wafer 100 on the holding surface 22 of the chuck table 20 so that the second wafer 120 faces up. This bonded wafer 100 may be the one used in the oxide film thickness distribution measuring process, or may be a different one. Thereafter, the control unit 7 opens the suction valve 35 to communicate the holding surface 22 with the suction source 201. As a result, the first wafer 110 of the bonded wafer 100 is suction-held by the holding surface 22 as shown in FIG. 1.

[0061] Next, the control unit 7 places the table unit 2 including the chuck table 20 that suction-holds the bonded wafer 100 at a processing position below the grinding mechanism 10 by the table moving mechanism 95. Then, while rotating the 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 grinding wheel 17 into contact with the radius portion of the upper surface of the second wafer 120 in the bonded wafer 100 held on the holding surface 22, thereby grinding the second wafer 120 with the grinding wheel 17. At this time, the control unit 7 measures the thickness of the bonded wafer 100 being ground using the thickness measuring mechanism 60, and performs grinding, for example, until the thickness of the bonded wafer 100 reaches a predetermined thickness (i.e., until the second wafer 120 reaches a predetermined thickness).

[0062] As described above, in the present embodiment, in the holding surface correction processing step, the shape of the holding surface 22 is corrected based on the thickness distribution of the oxide film 105 in the bonded wafer 100 so as to have a surface shape symmetrical to the upper surface 106 of the oxide film 105 in the bonded wafer 100. As a result, in the grinding step, when the holding portion 21 of the chuck table 20 is connected to the suction source 201 and the first wafer 110 of the bonded wafer 100 is suction-held by the holding surface 22, the upper surface 106 of the oxide film 105 and the upper surface of the second wafer 120 become substantially flat and parallel to the lower surface of the grinding wheel 17. Therefore, it is possible to effectively suppress the occurrence of partial thickness differences in the second wafer 120 ground by the grinding wheel 17.

[0063] Therefore, it becomes possible to grind the second wafer 120 to a uniform thickness. Therefore, by manufacturing a laminated wafer using the bonded wafer 100, the laminated wafer can be stacked and formed to a uniform thickness. In addition, since it is not necessary to spend time on the polishing process for making the thickness of the oxide film 105 uniform by polishing, it is possible to shorten the processing time for manufacturing the laminated wafer including the bonded wafer 100, and productivity can be improved.

[0064] In the oxide film thickness distribution measuring step in the above-described embodiment, the first wafer 110 of the bonded wafer 100 is held by the holding surface 22 of the chuck table 20 so that the second wafer 120 is on the upper side. In relation to this, in the oxide film thickness distribution measuring step, the second wafer 120 of the bonded wafer 100 may be held by the holding surface 22 of the chuck table 20 so that the first wafer 110 is on the upper side.

[0065] In this case, in the oxide film thickness distribution measurement process, light having a wavelength that is transparent to the first wafer 110 and oxide film 105 of the bonded wafer 100 is irradiated onto the bonded wafer 100 from the first wafer 110 side to measure the thickness of the entire surface of the oxide film 105. Therefore, the oxide film thickness distribution measurement process is a process of measuring the thickness of the entire oxide film by irradiating the bonded wafer 100 with light having a wavelength that is transparent to the wafer on the light incident side (either the first wafer 110 or the second wafer 120) and the oxide film.

[0066] The oxide film thickness distribution measuring step may be performed in a state where the bonded wafer 100 is not held by the chuck table 20 of the grinding apparatus 1 .

[0067] In this case, for example, in the oxide film thickness distribution measuring step, the control unit 7 or an operator holds one of the first wafer 110 or the second wafer 120 of the bonded wafer 100 by a holding surface of a table (not shown) equipped with a non-contact thickness measuring mechanism 70 (see FIG. 5). Then, the control unit 7 measures the thickness of the oxide film 105 by the non-contact thickness measuring device 71 while gradually rotating the table holding the bonded wafer 100 and gradually moving the non-contact thickness measuring device 71 in the radial direction of the bonded wafer 100 by the moving unit 72. In this way, the control unit 7 can obtain the thickness distribution of the entire surface of the oxide film 105. In this case, the above-mentioned holding step and the subsequent separating step in the oxide film thickness distribution measuring step are not necessary.

[0068] Next, a second bonded wafer grinding method (second grinding method) according to this embodiment will be described. Like the first grinding method, this grinding method is a bonded wafer grinding method in which the first wafer 110 of the bonded wafer 100, in which the first wafer 110 and the second wafer 120 of uniform thickness are bonded together via an oxide film 105, is held on the holding surface 22 of the chuck table 20, and the second wafer 120 is ground by a grinding wheel 17.

[0069] [Second grinding method] [Oxide film top surface height distribution measurement process] In the second grinding method, first, an oxide film upper surface height distribution measuring step is performed. In this step, the first wafer 110 of the bonded wafer 100 is held by the holding surface 22 of the chuck table 20, and light having a wavelength that is transparent to the second wafer 120 is irradiated onto the bonded wafer 100 to measure the height distribution of the entire surface of the upper surface 106 of the oxide film 105.

[0070] In this step, a holding step is first performed in the same manner as in the oxide film thickness distribution measuring step of the first grinding method. In the holding step, the holding surface 22 of the chuck table 20 is connected to the suction source 201, and the first wafer 110 of the bonded wafer 100 (see FIG. 2) is held by the holding surface 22.

[0071] 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 uses the transfer device 45 shown in FIG. 4 to place the first wafer 110 of the bonded wafer 100 on the holding surface 22 of the chuck table 20 so that the second wafer 120 faces 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 first wafer 110 is suction-held by the holding surface 22, which is the upper surface of the holding unit 21, as shown in FIG. 8.

[0072] Next, a measurement step is performed to measure the height distribution over the entire surface of the upper surface 106 of the oxide film 105 on the bonded wafer 100. In the measurement step, the height distribution over the entire surface of the upper surface 106 of the oxide film 105 on the bonded wafer 100 held on the chuck table 20 is measured.

[0073] For this measurement, a non-contact height measurement mechanism 75 as shown in Fig. 8 is used. The non-contact height measurement mechanism 75 is provided in the grinding apparatus 1, and has a non-contact height measurement device 76 and a moving unit 77 that moves the non-contact height measurement device 76 in the horizontal and vertical directions.

[0074] The non-contact height measuring device 76 measures the height of the oxide film 105 of the bonded wafer 100 held on the chuck table 20 in a non-contact manner. The non-contact height measuring device 76 irradiates the bonded wafer 100 from above the second wafer 120 in the bonded wafer 100, from the second wafer 120 side, with measurement light having a wavelength that is transparent to the second wafer 120. The non-contact height measuring device 76 then receives the top surface reflected light reflected by the top surface 106 of the oxide film 105 through the second wafer 120, and measures the height of the top surface 106 of the oxide film 105.

[0075] Then, the control unit 7 uses the non-contact height measuring mechanism 75 to measure the height distribution over the entire surface of the upper surface 106 of the oxide film 105 .

[0076] Specifically, the control unit 7 measures the height of the top surface 106 of the oxide film 105 by the non-contact height gauge 76 while rotating the chuck table 20 little by little by the table rotation mechanism 91 and moving the non-contact height gauge 76 little by little in the radial direction of the bonded wafer 100 by the moving unit 77. In this way, the control unit 7 can obtain the height distribution of the entire top surface 106 of the oxide film 105.

[0077] When measuring the thickness distribution of the oxide film 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 of the second wafer 120 below the non-contact height measuring device 76 (the portion where the height of the upper surface 106 of the oxide film 105 is measured) horizontal.

[0078] [Bonded Wafer Separation Process] Next, a bonded wafer separating step is performed. In this step, the control unit 7 separates the bonded wafer 100 from the holding surface 22 of the chuck table 20. Specifically, the control unit 7 closes the suction valve 35 and releases the suction of the bonded wafer 100 by the holding surface 22 by, for example, supplying water and / or air to the holding surface 22. Thereafter, the control unit 7 holds the bonded wafer 100 on the holding surface 22 using the transfer device 45 shown in FIG. 4, and separates (transports) it from the holding surface 22. This exposes the holding surface 22.

[0079] [Holding surface modification process] Next, a holding surface correction processing step is performed. In this step, the holding surface 22 exposed by the bonded wafer separation step is processed based on the overall height distribution of the upper surface 106 of the oxide film 105 measured in the oxide film upper surface height distribution measurement step.

[0080] Specifically, similarly to the holding surface correction processing step in the first grinding method, the control unit 7 uses the etching mechanism 40 shown in FIG. 5 to partially inject plasmatized etching gas from an injection nozzle 41 onto the holding surface 22 based on the overall height distribution of the upper surface 106 of the oxide film 105, and performs correction processing on the holding surface 22 by atmospheric pressure plasma etching.

[0081] By such correction processing, the shape of the holding surface 22 is corrected to, for example, a surface shape symmetrical to the upper surface 106 of the oxide film 105 (a shape having an upper surface height distribution symmetrical to the upper surface 106). As a result, when the chuck table 20 is connected to the suction source 201 and the first wafer 110 of the bonded wafer 100 is suction-held by the holding surface 22, the upper surface 106 of the oxide film 105 and the upper surface of the second wafer 120 can be made substantially flat.

[0082] [Grinding process] After the holding surface correction processing step, a grinding step is carried out on the bonded wafer 100. This step is the same as the grinding step in the first grinding method. That is, the control unit 7 causes the holding surface 22 to hold the first wafer 110 of the bonded wafer 100, and the grinding wheel 17 of the grinding mechanism 10 grinds the second wafer 120 of the bonded wafer 100 to, for example, a predetermined thickness.

[0083] In this way, in the second grinding method, in the holding surface correction processing step, the shape of the holding surface 22 is corrected to have a surface shape symmetrical to the upper surface 106 of the oxide film 105 of the bonded wafer 100, for example, based on the height distribution of the upper surface 106 of the oxide film 105 of the bonded wafer 100. As a result, during the grinding step, when the holding part 21 of the chuck table 20 is connected to the suction source 201 and the first wafer 110 of the bonded wafer 100 is suction-held by the holding surface 22, the upper surface 106 of the oxide film 105 and the upper surface of the second wafer 120 become substantially flat and parallel to the lower surface of the grinding wheel 17. For this reason, it is possible to effectively suppress the occurrence of partial thickness differences in the second wafer 120 ground by the grinding wheel 17. Therefore, it is possible to grind the second wafer 120 to a uniform thickness.

[0084] 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.

[0085] 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 holding surface correction processing step in the first grinding method and the second grinding method. In this case, in the holding surface correction processing step, 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 based on the height distribution of the entire surface of the upper surface 106 of the oxide film 105 of the bonded wafer 100.

[0086] By such correction processing, the shape of the holding surface 22 is corrected to a surface shape symmetrical to the upper surface 106 of the oxide film 105, for example, in the same way as in the case where the etching mechanism 40 is used.

[0087] 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).

[0088] 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 injection nozzle 41 of the etching mechanism 40 or the small diameter grinding wheel unit 51 of the holding surface modification grinding mechanism 50 horizontal.

[0089] Moreover, the table unit 2 may have a pin chuck type holding table (pin chuck table) instead of the chuck table 20. The pin chuck type holding table has, for example, a frame body similar to the frame body 23 shown in FIG. 3 and a plurality of support pins made of silicon provided in the recesses of the frame body. The upper end surfaces of the plurality of support pins form a holding surface. Even in the case of such a pin chuck type holding table, the holding surface can be corrected into a desired shape by the etching mechanism 40 or the holding surface correction grinding mechanism 50.

[0090] In the above-described embodiment, a holding surface forming step may be performed before the oxide film thickness distribution measuring step or the oxide film upper surface height distribution measuring step. In this holding surface forming step, the control unit 7 uses the grinding wheel 17 of the grinding mechanism 10 to grind the upper surface of the holding portion 21 and the upper surface of the frame 23 of the chuck table 20, thereby forming (regenerating) the holding surface 22 and the frame surface 24. In addition, in the holding surface forming step, a table grinding wheel for table grinding, which is a grinding wheel for grinding the chuck table 20, may be used instead of the grinding wheel 17. In this case, in the holding surface forming step, the operator attaches a table grinding wheel including a table grinding wheel to the wheel mount 13 instead of the grinding wheel 15. [Explanation of symbols]

[0091] 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: 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, 45: conveying device, 46: conveying pad, 47: moving mechanism, 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, 75: non-contact height measuring mechanism, 76: non-contact height measuring device, 77: moving unit, 80: grinding feed mechanism, 91: table rotation mechanism, 93: tilt adjustment mechanism, 95: Table moving mechanism, 100: bonded wafer, 105: oxide film, 106: upper surface, 107: lower surface, 110: first wafer, 120: second wafer, 201: suction source, 300: screw, 301: table rotation axis, 511: small diameter grinding wheel, 512: Motor, H: Top height distribution

Claims

1. A method for grinding a bonded wafer, comprising: holding a first wafer of a bonded wafer, which is formed by bonding a first wafer and a second wafer having a uniform thickness together via an oxide film, on a holding surface of a chuck table; and grinding the second wafer with a grinding wheel, the method comprising the steps of: an oxide film thickness distribution measuring step of irradiating the bonded wafer with light having a wavelength that is transparent to the first wafer or the second wafer, which is a wafer on the light incident side, and the oxide film, to measure a thickness distribution of the entire surface of the oxide film; a support surface correction processing step of processing the support surface based on the thickness distribution of the oxide film over the entire surface measured in the oxide film thickness distribution measuring step; a grinding step of holding the first wafer of the bonded wafer on the holding surface after the holding surface correction processing step, and grinding the second wafer of the bonded wafer with the grinding wheel; Including, A method for grinding bonded wafers.

2. A method for grinding a bonded wafer, comprising: holding a first wafer of a bonded wafer, which is formed by bonding a first wafer and a second wafer having a uniform thickness together via an oxide film, on a holding surface of a chuck table; and grinding the second wafer with a grinding wheel, the method comprising the steps of: an oxide film upper surface height distribution measuring step of holding the first wafer by the holding surface of the chuck table and irradiating the bonded wafer with light having a wavelength that is transparent to the second wafer, thereby measuring a height distribution of the entire upper surface of the oxide film; a bonded wafer separating step of separating the bonded wafer from the holding surface of the chuck table; a holding surface correction processing step of processing the holding surface exposed by the bonded wafer separation step based on the height distribution of the entire upper surface of the oxide film measured in the oxide film upper surface height distribution measuring step; a grinding step of holding the first wafer of the bonded wafer on the holding surface after the holding surface correction processing step, and grinding the second wafer of the bonded wafer with the grinding wheel; Including, A method for grinding bonded wafers.

3. 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.

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

4. 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.

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

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