Edge trimming method and edge trimming apparatus

Abstract

To provide an edge trimming method and an edge trimming apparatus, by which grinding accuracy in trimming an edge of an outer peripheral portion of a grinding-object wafer bonded to a support wafer may be improved.SOLUTION: There is provided an edge trimming method for removing a chamfered portion (W13) on a bonded wafer(W), which is formed by bonding a grinding-object wafer (W1) having the chamfered portion on an outer periphery thereof and a support wafer (W2) together, by grinding with a rough grindstone (54) and thereafter grinding with a finishing grindstone (56). The method comprises: lowering the finishing grindstone from above the outer peripheral portion of the grinding-object wafer, forming a finishing-grindstone mark (W15) in the grinding-object wafer, and measuring the height (h2) of the bottom surface of the finishing-grindstone mark; then, calculating the height (h6) of the finishing grindstone to be located when grinding the grinding-object wafer based on the height of the bottom surface of the measured finishing-grindstone mark; forming a rough-ground surface (W17) by grinding, with the rough grindstone, the outer peripheral portion of the grinding-object wafer; and then, lowering the finishing grindstone to the calculated height, and grinding, with the finishing grindstone, the upper portion of the rough-ground surface from above to form a finish-ground surface (W18).SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to an edge trimming method and an edge trimming apparatus for trimming the outer periphery of a bonded wafer. [Background technology]

[0002] When a wafer is ground and thinned with a grinding wheel, a sharp edge is formed by the chamfer on the outer periphery of the wafer, and this sharp edge can cause cracks or chips on the outer periphery of the wafer. To prevent this cracking or chipping, a method has been proposed in which the chamfer on the outer periphery of the wafer is trimmed (edge ​​trimming) before grinding (see, for example, Patent Documents 1 and 2).

[0003] Furthermore, Patent Document 3 proposes a method of edge trimming the ground wafer of the bonded wafer obtained by bonding two wafers, a ground wafer and a support wafer. In this type of edge trimming, the outer periphery of the ground wafer is ground into a ring shape, and then the ground outer periphery is removed by etching, thereby completely removing the chamfered portion of the ground wafer and preventing the formation of a sharp edge in subsequent processing. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-149822 [Patent Document 2] Japanese Patent Publication No. 2020-040181 [Patent Document 3] Japanese Patent Application Laid-Open No. 2017-004989 Summary of the Invention [Problem to be solved by the invention]

[0005] When removing the ground peripheral portion by etching as described above, if the amount of the peripheral portion removed by grinding before etching is small, the height of the peripheral portion increases, which poses a problem of prolonging the etching time of the peripheral portion of the wafer to be ground.

[0006] On the other hand, in order to shorten the etching time, it is conceivable to increase the amount of removal of the outer peripheral portion by grinding before etching. However, if the amount of removal by grinding is increased, there is a high possibility that not only the wafer to be ground but also the support wafer will be ground if a processing error or the like occurs, which not only damages the support wafer but also interrupts the processing, resulting in a decrease in processing efficiency.

[0007] The present invention has been made in view of the above points, and one of its objects is to provide an edge trimming method and an edge trimming device that can improve the grinding accuracy in edge trimming of the outer peripheral portion of a wafer to be ground that is bonded to a support wafer, for example, before etching. [Means for solving the problem]

[0008] An edge trimming method according to one aspect of the present invention is an edge trimming method for bonding a support wafer to a ground wafer having a chamfered portion on its outer periphery, and then grinding the chamfered portion of the ground wafer with a rough grindstone and then removing the chamfered portion with a finish grindstone, the edge trimming method including a holding step of holding the support wafer of the bonded wafer on a chuck table, a finishing grindstone mark forming step of lowering the finishing grindstone to a predetermined height from above the outer periphery of the ground wafer of the bonded wafer, and measuring the height of the bottom surface of the finishing grindstone mark formed in the finishing grindstone mark forming step with a height measuring device. a finishing grindstone height calculation step of calculating the height of the finishing grindstone when grinding with the finishing grindstone from the height of the bottom surface of the finishing grindstone marks measured in the finishing grindstone mark height measurement step; a rough grinding step of rotating the bonded wafer while lowering the rough grindstone from above the outer periphery of the wafer to be ground of the bonded wafer to roughly grind the wafer to be ground; and a finish grinding step of rotating the bonded wafer while lowering the finishing grindstone from above the grinding surface of the wafer to be ground that has been ground with the rough grindstone to the height calculated in the finishing grindstone height calculation step to finish grind the wafer to be ground.

[0009] An edge trimming device according to one aspect of the present invention includes a chuck table having a holding surface for holding a bonded wafer formed by bonding a support wafer and a wafer to be ground, the support wafer having a chamfered portion on its outer periphery; a rotation mechanism for rotating the chuck table about an axis at the center of the holding surface; a rough grinding mechanism for roughly grinding the outer periphery of the support wafer to be ground of the bonded wafer held on the chuck table into a ring shape with a rough grindstone; a finish grinding mechanism for grinding the outer periphery of the support wafer to be ground with a finish grindstone having a grindstone grain size smaller than that of the rough grindstone; and a grinding mechanism for grinding the outer periphery of the support wafer ground with the finish grindstone. An edge trimming device comprising a height measuring device that measures the height of the grinding surface of a wafer to be ground, and a control unit, wherein the control unit comprises a processing mark formation control unit that forms processing marks on the outer periphery of the wafer to be ground with the finishing grindstone, a calculation unit that measures the height of the processing marks with the height measuring device and calculates the height of the finishing grindstone when finish grinding, a rough grinding control unit that brings the rough grindstone into contact with the outer periphery of the wafer to be ground and performs rough grinding, and a finish grinding control unit that positions the finishing grindstone at the height calculated by the calculation unit and finish grinds the grinding surface that has been rough ground with the rough grindstone. [Effects of the Invention]

[0010] According to the present invention, when edge trimming is performed by grinding with a roughing grindstone and a finishing grindstone, finishing grindstone marks are formed, their heights are measured, and the heights are calculated, and the finishing grindstone is then lowered to the calculated finishing grindstone height to perform finish grinding. This makes it possible to improve the grinding accuracy in the height direction of edge trimming during finish grinding. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a perspective view of an edge trimming device according to an embodiment of the present invention; [Figure 2] 2A and 2B are explanatory views of the holding step. [Figure 3] FIG. 10 is an explanatory diagram of a finishing grindstone mark forming step in the first adjustment step. [Figure 4] 4A and 4B are explanatory diagrams of the finishing grindstone mark height measuring step in the first adjustment step. [Figure 5]FIG. 10 is an explanatory diagram of a finishing stone height calculation step in the first adjustment step. [Figure 6] FIG. 10 is an explanatory diagram of a rough grindstone mark forming step in the second adjustment step. [Figure 7] 7A and 7B are explanatory diagrams of the rough grindstone mark height measuring step in the second adjustment step. [Figure 8] FIG. 10 is an explanatory diagram of a roughing grindstone height calculation step in the second adjustment step. [Figure 9] 9A and 9B are explanatory diagrams of the rough grinding step. [Figure 10] 10A and 10B are explanatory diagrams of the finish grinding step. [Figure 11] FIG. 10 is a plan view schematically showing the state after the finish grinding process is completed. [Figure 12] FIG. 10 is an explanatory diagram of a third adjustment step. [Figure 13] FIG. 2 is a block diagram showing a control system of the edge trimming device. [Figure 14] FIG. 10 is an explanatory diagram of a first adjustment step in a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, an edge trimming device 1 according to this embodiment will be described with reference to the accompanying drawings. Note that the edge trimming device 1 according to this embodiment is not limited to the configuration shown below and can be modified as appropriate. For the sake of convenience of explanation, some components are omitted in FIG. 1.

[0013] First, the overall configuration of an edge trimming device 1 will be described with reference to Fig. 1. Fig. 1 is a perspective view of the edge trimming device of this embodiment. The X-axis direction, Y-axis direction, and Z-axis direction shown in Fig. 1 are perpendicular to each other. The X-axis direction and Y-axis direction are approximately horizontal directions, and the Z-axis direction is the up-down direction (vertical direction).

[0014] As shown in FIG. 1, the edge trimming device 1 is configured to perform edge trimming on the outer periphery of a wafer to be ground W1 of a bonded wafer W held on a chuck table 21 by a rough grinding mechanism 51 and a finish grinding mechanism 52.

[0015] The grinding wafer W1 shown in FIG. 1 is, for example, a semiconductor wafer with a circular outer shape made of silicon. Its front surface W11 is partitioned into a grid pattern, with ICs and other devices (not shown) formed in each area. The grinding wafer W1 has a chamfered portion W13 (see FIG. 2B) at its outer periphery, which is roughly semicircular in cross section, or roughly quarter-circular on the front surface W11 side and the back surface W12 side. The chamfered portion W13 prevents cracking and dust generation during the manufacturing process of the grinding wafer W1. The grinding wafer W1 may be made of gallium arsenide, sapphire, gallium nitride, ceramics, resin, silicon carbide, or the like, in addition to silicon, and may not have any devices formed thereon.

[0016] The bonded wafer W is formed by bonding a ground wafer W1 and a support wafer W2 together. The support wafer W2 is formed in a disk shape with approximately the same diameter as the ground wafer W1. The support wafer W2 is made of any suitable material, including an inorganic material substrate such as glass or ceramics, a semiconductor substrate such as silicon, or a metal substrate such as stainless steel. In the bonded wafer W, the surface W11 of the ground wafer W1 is bonded to the entire upper surface of the support wafer W2 in FIG. 2B via an adhesive layer. Processing the ground wafer W1 as the bonded wafer W improves the handleability of the ground wafer W1 and also prevents warping and damage to the ground wafer W1 during processing.

[0017] An X-axis movement mechanism 15 that moves the chuck table 21 in the X-axis direction is disposed on the base 11 of the edge trimming device 1. The X-axis movement mechanism 15 has a pair of guide rails 16 that are arranged on the base 11 and are parallel to the X-axis direction, and a motor-driven X-axis table 17 that is slidably mounted on the pair of guide rails 16. A nut portion (not shown) is formed on the back side of the X-axis table 17, and a feed screw 18 is threadedly engaged with this nut portion. A drive motor 19 connected to one end of the feed screw 18 is rotated, whereby the chuck table 21 is fed for cutting along the pair of guide rails 16 in the X-axis direction.

[0018] A chuck table 21 for holding the bonded wafer W and a rotation mechanism 22 are provided on the X-axis table 17. The chuck table 21 has a holding surface 211 formed of a porous ceramic material, and the bonded wafer W is held by suction due to negative pressure generated on the holding surface 211. The rotation mechanism 22 is made up of a motor disposed below the chuck table 21 and a rotating shaft whose axial direction is in the Z-axis direction (vertical direction), and rotates the chuck table 21 around the center of the holding surface 211. In addition, a gate-shaped upright wall portion 12 is provided on the upper surface of the base 11 so as to straddle the movement path of the chuck table 21.

[0019] The standing wall portion 12 is provided with a Y-axis movement mechanism 31 that moves the rough grinding mechanism 51 and the finish grinding mechanism 52 in the Y-axis direction. The standing wall portion 12 is also provided with a first Z-axis movement mechanism 41 that moves the rough grinding mechanism 51 in the Z-axis direction and a second Z-axis movement mechanism 42 that moves the finish grinding mechanism 52 in the Z-axis direction.

[0020] The Y-axis movement mechanism 31 has a pair of guide rails 34 that are parallel to the Y-axis direction and are arranged on the front surface of the upright wall portion 12, and a pair of Y-axis tables 35 that are slidably installed on the pair of guide rails 34. A nut portion (not shown) is formed on the rear side of the Y-axis table 35, and a feed screw 36 is threadedly engaged with the nut portion. A drive motor 37 is connected to one end of the feed screw 36 for the Y-axis table 35. When the drive motor 37 rotates the feed screw 36, the Z-axis movement mechanisms 41, 42 and the grinding mechanisms 51, 52 are moved in the Y-axis direction along the guide rails 34.

[0021] Each of the Z-axis movement mechanisms 41, 42 has a pair of guide rails 44 that are arranged on the Y-axis table 35 and are parallel to the Z-axis direction, and a Z-axis table 45 that is slidably installed on the pair of guide rails 44. A nut portion (not shown) is formed on the back side of the Z-axis table 45, and a feed screw 46 is threadedly engaged with the nut portion. A drive motor 47 is connected to one end of the feed screw 46 for the Z-axis table 45. The drive motor 47 rotates the feed screw 46, causing each of the grinding mechanisms 51, 52 to move (up and down) along the guide rails 44 in the Z-axis direction.

[0022] The rough grinding mechanism 51 has a rough grinding stone 54 attached to the tip of a rotatably supported spindle 53 (see FIG. 2). The rough grinding stone 54 is formed in the shape of a circular blade, and can be, for example, a resin blade made of abrasive grains such as diamonds solidified with a resin bond. The rough grinding mechanism 51 rotates the spindle 53 during trimming, thereby rotating the rough grinding stone 54, and grinding water is sprayed from a spray nozzle (not shown) onto the portion being processed by the rough grinding stone 54.

[0023] The finish grinding mechanism 52 has a finishing stone 56 attached to the tip of a rotatably supported spindle 55 (see FIG. 2). The finishing stone 56 is also formed in the shape of a circular blade, and can be, for example, a resin blade made of abrasive grains such as diamonds solidified with a resin bond, and the abrasive grain size used is smaller than that of the coarse grinding stone 54. The finish grinding mechanism 52 rotates the spindle 55 (see FIG. 2) during edge trimming processing, thereby rotating the finishing stone 56, and grinding water is sprayed from a spray nozzle (not shown) onto the portion processed by the finishing stone 56.

[0024] A support frame 58 is erected on the upper surface of the base 11 in front of the gate-shaped upright wall portion 12 so as to straddle the movement path of the chuck table 21, and a height measuring device 59 is provided at the center of the support frame 58 in the Y-axis direction. The height measuring device 59 can be, for example, configured by a laser displacement meter equipped with a light-projecting unit and a light-receiving unit (not shown) that use a spot laser beam. The height measuring device 59 measures the height (position in the Z-axis direction) of the top surface of the wafer to be ground W1 in the bonded wafer W supported on the chuck table 21 in a non-contact manner.

[0025] The edge trimming apparatus 1 is provided with a control unit 70 that controls each unit of the apparatus (see FIGS. 1 and 13). The control unit 70 is composed of a processor, memory, etc. that execute various processes. The control unit 70 controls various operations such as forming the finishing grindstone marks W15 and the rough grindstone marks W16 (see FIG. 10), rough grinding by the rough grinding mechanism 51, finish grinding by the finish grinding mechanism 52, and measuring the height of the top surface of the wafer W1 to be ground, in accordance with a control program stored in the memory.

[0026] In the following description, unless a control entity is specified for the operation of each part of the edge trimming device 1, the operation is assumed to be controlled by a control signal sent from the control unit .

[0027] In the edge trimming apparatus 1 configured as described above, edge trimming is performed by grinding the chamfered portion W13 of the wafer to be ground W1 in the bonded wafer W with the rough grindstone 54 and then grinding and removing the chamfered portion W13 with the finish grindstone 56. The edge trimming method in this embodiment will be described below with reference to Figures 2 to 12. The edge trimming method in this embodiment is performed in the order of a holding step, a first adjustment step, a second adjustment step, a rough grinding step, a finish grinding step, and a third adjustment step.

[0028] [Holding process] In the edge trimming method of this embodiment, a holding step is first performed as shown in Figures 2A and 2B. Figures 2A and 2B are explanatory views of the holding step, with Figure 2A being a schematic plan view and Figure 2B being a schematic front view. In the holding step, the bonded wafer W is held so that its center coincides with the rotation axis of the chuck table 21. Specifically, the lower surface of the support wafer W2 of the bonded wafer W is suction-held by negative pressure generated on the holding surface 211 of the chuck table 21.

[0029] [First adjustment process] After the holding process step is performed, the first adjustment process is performed as shown in Figures 3 to 5. The first adjustment process is performed in the order of a finishing grindstone mark forming process, a finishing grindstone mark height measuring process, and a finishing grindstone height calculation process.

[0030] [First adjustment process: finishing grindstone mark formation process] 3 is a schematic front view illustrating the finishing grindstone mark forming step in the first adjustment step. As shown in Fig. 3, in the finishing grindstone mark forming step, the bonded wafer W held on the chuck table 21 is positioned below the finishing grindstone 56 of the finish grinding mechanism 52 by driving the X-axis movement mechanism 15 (see Fig. 1). Then, the finishing grindstone 56 is positioned at a position radially inward by a predetermined distance from the chamfered portion W13 of the wafer W1 to be ground by driving the Y-axis movement mechanism 31 (see Fig. 1).

[0031] Next, the finishing grindstone 56 is rotated at high speed by the high-speed rotation of the spindle 55 in the finish grinding mechanism 52. Furthermore, the second Z-axis movement mechanism 42 is driven to lower the finishing grindstone 56 of the finish grinding mechanism 52 from above the outer periphery of the wafer W1 to be ground of the bonded wafer W to a predetermined height. The lowering of the finishing grindstone 56 is controlled based on a set height h1 (see FIG. 5) at which the lower end surface of the finishing grindstone 56 should be positioned in the Z-axis direction, and the set height h1 is stored in advance in the control unit 70 (see FIG. 1). The set height h1 is set, for example, to a position higher than a rough grindstone height h6 (see FIG. 8) of the rough grindstone 54 in the rough grinding step described below.

[0032] As the rotating finishing wheel 56 descends, the outer peripheral portion of the wafer W1 to be ground is ground so as to cut downward from the back surface W12. In this control, the finishing wheel 56 is lowered according to the set height h1, and then the finishing wheel 56 is raised to separate from the wafer W1 to be ground. Finishing wheel marks W15, which become processing marks on the portion (ground surface) ground by the rotating finishing wheel 56, are left on the outer peripheral portion (chamfered portion W13) of the wafer W1 to be ground. At this time, rotation of the chuck table 21 around the Z axis is restricted, and the finishing wheel marks W15 are left in a narrow range on the outer peripheral portion of the wafer W1 to be ground.

[0033] In the edge trimming apparatus 1 of this embodiment, the rough grinding mechanism 51 and the finish grinding mechanism 52 are arranged side by side in the Y-axis direction (left and right direction in FIG. 3). Therefore, in the finish grinding stone mark forming step, the bonded wafer W is positioned below the finish grinding stone 56 of the finish grinding mechanism 52, and at the same time, the bonded wafer W is also positioned below the rough grinding stone 54 of the rough grinding mechanism 51. However, in the first adjustment step including the finish grinding stone mark forming step, the rough grinding stone 54 is maintained in a standby state above the wafer W1 to be ground.

[0034] [First adjustment process: Finishing grindstone mark height measurement process] 4A and 4B are explanatory diagrams of the finishing grindstone mark height measuring step in the first adjustment step, with FIG. 4A being a schematic plan view and FIG. 4B being a schematic front view. After the finishing grindstone mark forming step is performed, the finishing grindstone mark height measuring step is performed as shown in FIGS. 4A and 4B. In the finishing grindstone mark height measuring step, after the above-described finishing grindstone marks W15 are formed, the chuck table 21 is rotated approximately 90° clockwise in FIG. 4A by driving the rotation mechanism 22 (see FIG. 1) and positioned. This positions the finishing grindstone marks W15 on the ground wafer W1 below the height measuring device 59. In this state, the height h2 of the bottom surface of the finishing grindstone marks W15 formed in the finishing grindstone mark forming step is measured by the height measuring device 59, and the measurement result is output to the control unit 70.

[0035] [First adjustment process: Finishing stone height calculation process] 5 is a schematic front view illustrating the finishing stone height calculation step in the first adjustment step. After the finishing stone mark height measurement step is performed, the finishing stone height calculation step is performed as shown in FIG. 5. In the finishing stone height calculation step, the height of the bottom surface of the finishing stone 56 when grinding with the finishing stone 56 (when performing the finish grinding step) is calculated from the height h2 of the bottom surface of the finishing stone mark W15 measured as described above. Here, the height of the bottom surface of the finishing stone 56 is set to the finishing stone height h3, and it is assumed that the finishing stone height h3 is stored in advance in the control unit 70 as past data, an initial value, or the like.

[0036] In calculating the finishing stone height h3, the difference d1 between the height h2 of the bottom surface of the finishing stone marks W15 and the set height h1 stored in the control unit 70 is calculated. Then, a height position lower by the difference d1 from the finishing stone height h3 stored in the control unit 70 is calculated, and this calculation result is updated as the new finishing stone height h3. The updated (calculated) finishing stone height h3 is stored in the control unit 70. Completion of the finishing stone height calculation step completes the first adjustment step.

[0037] [Second adjustment process] After the first adjustment step is performed, the second adjustment step is performed as shown in Figures 6 to 8. The second adjustment step is performed in the order of a coarse grindstone mark forming step, a coarse grindstone mark height measuring step, and a coarse grindstone height calculating step. In the second adjustment step, the finishing grindstone 56 is maintained in a standby state above the wafer W1 to be ground.

[0038] [Second adjustment process: Rough grinding wheel mark formation process] 6 is a schematic front view illustrating the rough grindstone mark forming step in the second adjustment step. Before the start of the rough grindstone mark forming step, as shown in FIG. 4B, the bonded wafer W held on the chuck table 21 is positioned below the rough grindstone 54 of the rough grinding mechanism 51 by the first adjustment step. In this state, as shown in FIG. 6, the rough grindstone 54 is positioned at a position radially inward by a predetermined distance from the chamfered portion W13 of the wafer W1 to be ground by driving the Y-axis movement mechanism 31 (see FIG. 1).

[0039] Next, the rough grinding wheel 54 is rotated at high speed by the high-speed rotation of the spindle 53 in the rough grinding mechanism 51. Furthermore, the first Z-axis movement mechanism 41 is driven to lower the rough grinding wheel 54 of the rough grinding mechanism 51 from above the outer periphery of the wafer W1 to be ground of the bonded wafer W to a predetermined height. The lowering of the rough grinding wheel 54 is controlled based on a set height h4 (see FIG. 8) at which the lower end surface of the rough grinding wheel 54 should be positioned in the Z-axis direction, and the set height h4 is stored in advance in the control unit 70 (see FIG. 1). The set height h4 is set to, for example, the same height position as or approximately the same as the set height h1.

[0040] As the rotating rough grinding wheel 54 descends, the outer peripheral portion of the wafer W1 to be ground is ground so as to cut downward from the back surface W12. In this control, the rough grinding wheel 54 is lowered according to the set height h4, and then the rough grinding wheel 54 is controlled to rise and separate from the wafer W1 to be ground. On the outer peripheral portion of the wafer W1 to be ground, rough grinding wheel marks W16, which become processing marks, are formed in the portion ground by the rotating rough grinding wheel 54. At this time, because the rotation of the chuck table 21 around the Z axis is restricted, the rough grinding wheel marks W16 are formed in a narrow range on the outer peripheral portion of the wafer W1 to be ground.

[0041] [Second adjustment process: rough grindstone mark height measurement process] 7A and 7B are explanatory diagrams of the rough grindstone mark height measuring step in the second adjustment step, with FIG. 7A being a schematic plan view and FIG. 7B being a schematic front view. After the finish grindstone mark forming step is performed, the rough grindstone mark height measuring step is performed as shown in FIGS. 7A and 7B. In the rough grindstone mark height measuring step, after the rough grindstone marks W16 described above are formed, the chuck table 21 is rotated approximately 90° counterclockwise in FIG. 7A by driving the rotation mechanism 22 (see FIG. 1) and positioned. This positions the rough grindstone marks W16 on the ground wafer W1 below the height measuring device 59. In this state, the height h5 of the bottom surface of the rough grindstone marks W16 formed in the rough grindstone mark forming step is measured by the height measuring device 59, and the measurement result is output to the control unit 70.

[0042] [Second adjustment process: rough grindstone height calculation process] 8 is a schematic front view illustrating the roughing grindstone height calculation step in the second adjustment step. After the roughing grindstone mark height measurement step is performed, the roughing grindstone height calculation step is performed as shown in FIG. 8. In the roughing grindstone height calculation step, the height of the bottom end face of the roughing grindstone 54 when grinding with the roughing grindstone 54 (when performing the rough grinding step) is calculated from the height h5 of the bottom face of the roughing grindstone mark W16 measured as described above. Here, the height of the bottom end face of the roughing grindstone 54 is set to the roughing grindstone height h6, and it is assumed that the roughing grindstone height h6 is stored in advance in the control unit 70 as past data, an initial value, or the like.

[0043] In calculating the roughing wheel height h6, the difference d2 between the height h5 of the bottom surface of the roughing wheel marks W16 and the set height h4 stored in the control unit 70 is calculated. Then, a height position lower than the roughing wheel height h6 stored in the control unit 70 by the difference d2 is calculated, and this calculation result is updated as the new roughing wheel height h6. The updated (calculated) roughing wheel height h6 is stored in the control unit 70. Completion of the roughing wheel height calculation step completes the second adjustment step.

[0044] [Rough grinding process] 9A and 9B are explanatory views of the rough grinding step, where Fig. 9A is a schematic plan view and Fig. 9B is a schematic front view. After the second adjustment step is performed, the rough grinding step is performed as shown in Fig. 9A and 9B.

[0045] Before the start of the rough grinding step, the bonded wafer W held on the chuck table 21 is positioned below the rough grinding wheel 54 of the rough grinding mechanism 51 in the second adjustment step, and the rough grinding wheel 54 is positioned at a predetermined distance radially inward from the chamfered portion W13 of the wafer W1 to be ground. For example, the rough grinding wheel 54 is positioned so that approximately two-thirds of the lower end surface of the rough grinding wheel 54 comes into contact with the chamfered portion W13 of the wafer W1 to be ground.

[0046] With the rough grinding wheel 54 positioned in this manner, the rough grinding wheel 54 is rotated at high speed by the high-speed rotation of the spindle 53 in the rough grinding mechanism 51. Next, the first Z-axis movement mechanism 41 is driven to lower the rough grinding wheel 54 of the rough grinding mechanism 51 from above the outer periphery of the wafer to be ground W1 of the bonded wafer W to the rough grinding wheel height h6 (see FIG. 8) calculated and updated in the rough grinding wheel height calculation step.

[0047] After the rough grinding wheel 54 is lowered to the above-mentioned height, the rough grinding wheel 54 is maintained at that height while continuing to rotate, and the chuck table 21 is rotated counterclockwise as viewed from above. As a result, rough grinding by the rough grinding wheel 54 proceeds along the outer periphery of the wafer W1 to be ground while rotating the chuck table 21 and the held bonded wafer W, and a roughly ground surface (ground surface) W17 is formed. Then, after the chuck table 21 is rotated approximately 180°, the finish grinding step is started while the rough grinding step is continued, and the rough grinding step and the finish grinding step are carried out simultaneously.

[0048] [Finishing grinding process] 10A and 10B are explanatory diagrams of the finish grinding step, with Fig. 10A being a schematic plan view and Fig. 10B being a schematic front view. Fig. 11 is a schematic plan view showing the state after the finish grinding step is completed. During the rough grinding step, the finish grinding step is carried out as shown in Figs. 10A and 10B.

[0049] Before the start of the finish grinding process, the bonded wafer W held on the chuck table 21 is positioned below the finish grinding stone 56 of the finish grinding mechanism 52. The finish grinding stone 56 is positioned at a predetermined distance radially inward from the chamfered portion W13 of the wafer W1 to be ground. For example, the finish grinding stone 56 is positioned so that approximately two-thirds of the bottom end surface of the finish grinding stone 56 comes into contact with the chamfered portion W13 of the wafer W1 to be ground.

[0050] With the finishing wheel 56 positioned in this manner, the finishing wheel 56 is rotated at high speed by the high-speed rotation of the spindle 55 in the finish grinding mechanism 52. Then, the rotation of the chuck table 21 in the rough grinding step proceeds by approximately 180 degrees, and when the roughly ground surface W17 reaches below the finishing wheel 56, the second Z-axis movement mechanism 42 is driven. By driving the second Z-axis movement mechanism 42 in this manner, the finishing wheel 56 of the finish grinding mechanism 52 is lowered from above the roughly ground surface W17 of the wafer W1 to the finishing wheel height h3 (see FIG. 5) calculated and updated in the finishing wheel height calculation step.

[0051] After the finishing grindstone 56 is lowered to the above-mentioned height, the roughing grindstone 54 and the finishing grindstone 56 are rotated while the chuck table 21 continues to rotate counterclockwise while maintaining the height position of the finishing grindstone 56. As a result, as shown in FIG. 10A , rough grinding by the roughing grindstone 54 and finish grinding by the finishing grindstone 56 are simultaneously performed along the outer periphery of the wafer W1 to be ground, while the chuck table 21 and the held bonded wafer W are rotated. Here, the ground surface that has been subjected to both the rough grinding process and the finish grinding process is referred to as the finish grinding surface (ground surface) W18. In FIG. 10A , the finish grinding surface W18 is illustrated with narrower hatching intervals than the rough grinding surface W17.

[0052] During the finish grinding step, after the chuck table 21 has rotated approximately 360 degrees since the start of grinding in the rough grinding step, the rough grindstone 54 is raised and separated from the wafer W1 to be ground by driving the first Z-axis movement mechanism 41. As a result, the entire circumference of the chamfered portion W13 (outer periphery) of the wafer W1 to be ground is roughly ground into a ring shape by the rough grindstone 54, and the rough grinding step is completed. While the rough grindstone 54 is raised, finish grinding by the finish grindstone 56 continues.

[0053] Then, after the chuck table 21 has rotated approximately 360 degrees from the start of grinding in the finish grinding step, the second Z-axis movement mechanism 42 is driven to raise the finish grindstone 56 and move it away from the wafer W1 to be ground. As a result, the entire circumference of the chamfered portion W13 of the wafer W1 to be ground is finish-ground into a ring shape by the finish grindstone 56, and a finish-ground surface W18 is formed around the entire outer periphery of the wafer W1 to be ground, as shown in FIG. 11, and the finish grinding step is completed.

[0054] [Third adjustment process] After the second adjustment step is performed, the third adjustment step is performed as shown in Fig. 12. Fig. 12 is a schematic front view illustrating the third adjustment step. The third adjustment step is performed in the order of a finish-ground surface height measurement step, a calculation step, and a correction step.

[0055] [Third adjustment process: Finish grinding surface height measurement process] In the finish grinding surface height measurement process, the height measuring device 59 measures the height h7 of the finish grinding surface W18, which becomes the finish grinding surface ground in the above-mentioned finish grinding process, and the measurement result is output to the control unit 70.

[0056] [Third adjustment process: calculation process] In the third adjustment step, after the finish-ground surface height measurement step is performed, a calculation step is performed. In the calculation step, a difference d3 between the height h7 of the finish-ground surface W18 measured as described above and the upper surface height h8 of the support wafer W2 is calculated. The upper surface height h8 of the support wafer W2 is assumed to be stored in advance in the control unit 70 as past data, an initial value, or the like.

[0057] [Third adjustment process: correction process] In the third adjustment step, after the calculation step, a correction step is carried out. In the correction step, the finishing stone height h3 (see FIG. 5) calculated in the finishing stone height calculation step in the first adjustment step described above is corrected in a direction lowering the finishing stone height h3 by the difference d3 calculated in the calculation step. The corrected finishing stone height h3 is stored in the control unit 70. Completion of the correction step completes the third adjustment step.

[0058] By carrying out each of the above steps, a series of edge trimming processes for the wafer W1 to be ground in the edge trimming apparatus 1 is completed. After the edge trimming process is completed, the finish-ground surface W18 (see FIG. 11) of the wafer W1 to be ground is etched. In this etching, an etching solution is sprayed onto the finish-ground surface W18 from above the wafer W1 to be ground via a nozzle while the bonded wafer W is rotated by a spinner table. This removes all of the thickness portion that forms the finish-ground surface W18 by the chemical action of the etching solution, preventing the formation of a sharp edge in subsequent processing.

[0059] Fig. 13 is a diagram showing an example of functional blocks of a control unit in the edge trimming device. As shown in Fig. 13, the control unit 70 of the edge trimming device 1 functions as a machining mark formation control unit 71, a calculation unit 72, a rough grinding control unit 73, and a finish grinding control unit 74. These functional blocks are realized by the control unit 70 executing a program stored in the memory of the control unit 70, and do not mean that these functional blocks exist separately. The control unit 70 shown in Fig. 13 may include other functional blocks in addition to the above functional blocks.

[0060] The processing mark formation control unit 71 controls each part of the device, such as the X-axis moving mechanism 15, the Y-axis moving mechanism 31, the first Z-axis moving mechanism 41, the second Z-axis moving mechanism 42, the rough grinding mechanism 51, and the finish grinding mechanism 52, in the first and second adjustment steps described above. To give a specific example, the processing mark formation control unit 71 executes control to form finish grinding stone marks W15 on the outer periphery of the ground wafer W1 with the finishing grindstone 56, and control to form rough grinding stone marks W16 on the outer periphery of the ground wafer W1 with the rough grindstone 54.

[0061] In the first to third adjustment steps described above, the calculation unit 72 controls the measurement by the height measuring device 59 of the height h2 of the bottom surface of the finish grinding stone marks W15, the height h5 of the bottom surface of the rough grinding stone marks W16, and the height h7 of the finish-ground surface W18. In addition, in the first to third adjustment steps, the calculation unit 72 calculates, updates, and corrects the finish grinding stone height h3 and the rough grinding stone height h6, and outputs these heights h3 and h6 to the rough grinding control unit 73 and the finish grinding control unit 74.

[0062] The rough grinding control unit 73 controls each part of the device in the rough grinding step described above, such as the X-axis moving mechanism 15, the Y-axis moving mechanism 31, the first Z-axis moving mechanism 41, and the rough grinding mechanism 51. The rough grinding control unit 73 executes control to place the rough grinding wheel 54 at the rough grinding wheel height h6 calculated by the calculation unit 72, and to bring the rough grinding wheel 54 into contact with the outer periphery of the wafer W1 to be ground and perform rough grinding to form a roughly ground surface W17.

[0063] The finish grinding control unit 74 controls each unit of the device in the above-mentioned finish grinding process, such as the X-axis moving mechanism 15, the Y-axis moving mechanism 31, the second Z-axis moving mechanism 42, and the finish grinding mechanism 52. The finish grinding control unit 74 executes control to position the finish grinding wheel 56 at the finish grinding wheel height h3 calculated by the calculation unit 72, and control to bring the finish grinding wheel 56 into contact with the rough-ground surface W17 of the wafer W1 to be ground and perform finish grinding to form a finish-ground surface W18.

[0064] As described above, in the above embodiment, before the finish grinding step is performed, the formation of the finish grindstone marks W15 on the wafer W1 to be ground and the height h2 are measured, and the finish grindstone height h3 (the height of the bottom end face of the finish grindstone 56 when grinding with the finish grindstone 56) is calculated. This makes it possible to improve the accuracy in the height direction of the finish ground surface W18 formed in the finish grinding step.

[0065] By improving the grinding accuracy of the finish-ground surface W18 in this way, it is possible to prevent the etching time required to remove the entire thickness of the finish-ground surface W18 from becoming too long. Moreover, it is possible to prevent the support wafer W2 from being ground by passing through the entire thickness of the wafer W1 to be ground during grinding with the finishing grindstone 56. This makes it possible to prevent damage to the support wafer W2 and to prevent interruptions to processing and a decrease in processing efficiency.

[0066] Furthermore, in the above embodiment, edge trimming is performed using two types of grinding stones, the rough grinding stone 54 and the finishing grinding stone 56, which have different grinding grain sizes, so uneven wear of the finishing grinding stone 56 can be prevented and edge trimming can be completed in a short time.

[0067] Furthermore, in the above embodiment, after the finish grinding step is performed, the height of the finish-ground surface W18 is measured in the third adjustment step, and the finishing wheel height h3 is corrected when grinding with the finishing wheel 56 in the next edge trimming of the wafer W1 to be ground. This makes it possible to correct the finishing wheel height h3 in the finish grinding step in the next edge trimming by the amount of wear of the finishing wheel 56 in the finish grinding step, thereby improving the accuracy in the height direction of the finish-ground surface W18.

[0068] Furthermore, in the above embodiment, before the rough grinding step is performed, the formation of the rough grinding stone marks W16 on the ground wafer W1 and the height h5 are measured, and the rough grinding stone height h6 (the height of the bottom end face of the rough grinding stone 54 when grinding with the rough grinding stone 54) is calculated. This makes it possible to improve the accuracy in the height direction of the roughly ground surface W17 formed in the rough grinding step, and to maintain a constant amount of wear on the finishing stone 56 in the finish grinding step.

[0069] In the first adjustment step of the above embodiment, the finishing stone mark forming step and the finishing stone mark height measuring step are each performed once, but they may also be performed twice. In this case, the finishing stone mark forming step and the finishing stone mark height measuring step are each performed once, as in the above embodiment, and then the second finishing stone mark forming step is performed. In the second finishing stone mark forming step, second finishing stone marks W152 are formed at positions that overlap with the finishing stone marks W15 of the first finishing stone mark forming step, as shown in FIG. 12. The height of the finishing stone 56 for the first finishing stone marks W15 is controlled based on the set height h1, and the height of the finishing stone 56 for the second finishing stone marks W152 is controlled based on the set height h12. The set height h12 is set lower than the set height h1, so that the bottom of the second finishing stone marks W152 is lower than the bottom of the first finishing stone marks W15.

[0070] After the second finishing stone mark forming process is performed, a second finishing stone mark height measuring process is performed. In the second finishing stone mark height measuring process, the height h22 of the bottom surface of the second finishing stone mark W152 is measured by the height measuring device 59. Then, after the second finishing stone mark height measuring process is performed, a finishing stone height calculating process is performed.

[0071] In the finishing stone height calculation process, the difference d5 between the set height h1 and the set height h12 is calculated. Also, the difference d6 between the height h2 of the bottom surface of the first finishing stone mark W15 and the height h22 of the bottom surface of the second finishing stone mark W152 is calculated, and the difference d7 between the differences d5 and d6 is calculated. Then, a height position lower by the difference d7 from the finishing stone height h3 during the finish grinding process is calculated, and this calculation result is updated as the new finishing stone height h3.

[0072] In the edge trimming method of the above embodiment, at least one of the second adjustment step and the third adjustment step may be omitted. When edge trimming a plurality of bonded wafers W, all of the above steps may be performed for all of the bonded wafers W, or at least one of the second adjustment step and the third adjustment step may be omitted for every predetermined number of bonded wafers W (for example, every five wafers).

[0073] Furthermore, in the first adjustment process in the above embodiment, when edge trimming is performed on multiple bonded wafers W, it may be performed on all of the bonded wafers W, or it may be performed on every predetermined number of bonded wafers W (for example, every five wafers).

[0074] Furthermore, in the third adjustment step, the height h7 of the finish-ground surface W18 may be measured continuously in the circumferential direction of the wafer W1 to be ground by performing measurements using the height measuring device 59 while rotating the chuck table 21. By such measurements, for example, the height h7 of the finish-ground surface W18, which changes in accordance with the increase in the amount of wear of the finish grinding stone 56 in the finish grinding step, can be measured, and the height h3 of the finish grinding stone in the next finish grinding step can be changed in accordance with this change. This makes it possible to make the height h7 uniform in the circumferential direction of the ring-shaped finish-ground surface W18, further improving the accuracy of the height direction of the finish-ground surface W18.

[0075] Furthermore, the embodiments of the present invention are not limited to the above-described embodiments and modifications, and may be variously changed, substituted, or modified within the scope of the spirit of the technical idea of ​​the present invention. Furthermore, if the technical idea of ​​the present invention can be realized in a different way due to technological advances or other derived technologies, it may be implemented using that method. Therefore, the claims cover all embodiments that may fall within the scope of the technical idea of ​​the present invention. [Industrial Applicability]

[0076] As described above, the present invention has the effect of improving grinding accuracy by edge trimming the outer peripheral portion of the wafer to be ground before etching. [Explanation of symbols]

[0077] 1: Edge trimming device 21: Chuck table 211: Holding surface 22: Rotation mechanism 51: Rough grinding mechanism 52: Finish grinding mechanism 54: Coarse whetstone 56: Finishing stone 59: Height measuring instrument 70: Control unit 71: Processing mark formation control unit 72: Calculation section 73: Rough grinding control section 74: Finish grinding control unit W: Bonded wafer W1: Wafer to be ground W13: Chamfered part W15: Finishing stone marks W16: Rough whetstone marks W17: Surface to be roughly ground (surface to be ground) W18: Finished ground surface (ground surface) W2: Support wafer

Claims

1. 1. An edge trimming method for a bonded wafer, which is formed by bonding a support wafer to a wafer to be ground, the chamfered portion of the wafer to be ground is ground with a rough grindstone, and then removed by grinding with a finish grindstone, comprising the steps of: a holding step of holding the supporting wafer of the bonded wafer on a chuck table; a finishing grindstone mark forming step of lowering the finishing grindstone to a predetermined height from above the outer periphery of the ground wafer of the bonded wafer to form finishing grindstone marks on the ground wafer; a finishing grindstone mark height measuring step of measuring the height of the bottom surface of the finishing grindstone mark formed in the finishing grindstone mark forming step with a height measuring device; a finishing stone height calculation step of calculating the height of the finishing stone when grinding with the finishing stone from the height of the bottom surface of the finishing stone mark measured in the finishing stone mark height measurement step; a rough grinding step of roughly grinding the wafer to be ground by rotating the bonded wafer while lowering the rough grindstone from above the outer periphery of the wafer to be ground of the bonded wafer; a finish grinding step of lowering the finishing grindstone from above the grinding surface of the grinding wafer ground with the rough grindstone to the height calculated in the finishing grindstone height calculation step while rotating the bonded wafer to finish grind the grinding wafer.

2. a finish-grinding surface height measuring step of measuring the height of the finish-grinding surface by the height measuring device; a calculating step of calculating a difference between the ground surface height measured in the finish ground surface height measuring step and the upper surface height of the support wafer; 2. The edge trimming method according to claim 1, further comprising a correction step of correcting the height of the finishing stone calculated in the finishing stone height calculation step in a direction lowering the height of the finishing stone by the difference calculated in the calculation step.

3. a coarse grindstone mark forming step of lowering the coarse grindstone to a predetermined height from above the outer periphery of the ground wafer of the bonded wafer to form a coarse grindstone mark on the ground wafer; a coarse grindstone mark height measuring step of measuring the bottom surface of the coarse grindstone mark formed in the coarse grindstone mark forming step with the height measuring device; A rough grindstone height calculation step of calculating the height of the rough grindstone when grinding with the rough grindstone from the height of the rough grindstone marks measured in the rough grindstone mark height measurement step, 2. The edge trimming method according to claim 1, wherein in the rough grinding step, the rough grindstone is lowered to the height calculated in the rough grindstone height calculation step.

4. an edge trimming apparatus including: a chuck table having a holding surface for holding a bonded wafer formed by bonding a support wafer and a grinding target wafer having a chamfered portion on an outer periphery thereof; a rotation mechanism for rotating the chuck table about an axis of a center of the holding surface; a rough grinding mechanism for roughly grinding an outer periphery of the grinding target wafer of the bonded wafer held on the chuck table into a ring shape with a rough grinding stone; a finish grinding mechanism for grinding an outer periphery of the grinding target wafer with a finish grinding stone having a grinding grain size smaller than that of the rough grinding stone; a height measuring device for measuring a height of a ground surface of the grinding target wafer ground with the finish grinding stone; and a control unit, The control unit a processing mark formation control unit that forms a processing mark on an outer periphery of the ground wafer by the finishing grindstone; a calculation unit that measures the height of the machining mark by the height measuring device and calculates the height of the finishing grindstone when finishing grinding; a rough grinding control section for bringing the rough grindstone into contact with an outer peripheral portion of the wafer to be ground and rough grinding the outer peripheral portion of the wafer to be ground; and a finish grinding control unit that places the finishing grindstone at the height calculated by the calculation unit and finish-grinds the surface to be ground that has been roughly ground with the rough grindstone.

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