Method and device for processing wafer

Abstract

To address a problem of a damage caused by falling due to insufficient adsorption during delivery of a joined wafer.SOLUTION: This method for processing a wafer comprises: a preparation step of preparing a grinder 1; a wafer holding step of holding a second wafer 20 side of a joined wafer W on a chuck table 6 and exposing a first wafer 10; a grinding step of rotating the joined wafer W held on the chuck table 6 and a grinding wheel 44 to operate grind feeding means 49, and grinding the first wafer 10 by a grindstone 45; a separation step of determining peeling of the first wafer 10 from the second wafer 20 when a sudden change occurs in a value measured by a load meter 64, and operating the grind feeding means 49 to separate the grindstone 45 from the first wafer 10; and a determination step of detecting the peeling state of the first wafer 10 and determining whether the joined wafer W can be delivered from the chuck table 6 by delivery means.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a wafer processing method and processing apparatus for grinding and thinning a first wafer in a bonded wafer formed by bonding a first wafer and a second wafer. [Background technology]

[0002] A wafer having a plurality of devices such as ICs and LSIs formed on its front surface along division lines is ground on its back surface by a grinding device to form it into the desired thickness, and then separated into individual device chips by a cutting device or the like for use in electrical devices such as mobile phones and personal computers.

[0003] In addition, TF-SAW devices, which excite surface acoustic waves using a thin piezoelectric film or a regular comb-shaped electrode formed on a substrate, which are indispensable for communication devices such as mobile phones, are formed by bonding a lithium tantalate (LiTaO3=LT) wafer (hereinafter referred to as an "LT wafer") or a lithium niobate (LiNbO3=LN) wafer (hereinafter referred to as an "LN wafer") used as a piezoelectric material to a wafer such as silicon, sapphire, quartz, or glass, which serves as a supporting substrate, to form a bonded wafer, and then the LT wafer or LN wafer is thinned to a desired thickness (for example, 5 μm) using a grinding device, and then electrodes are formed on the surface and the wafer is divided into individual device chips, which are then mounted in various communication devices.

[0004] Furthermore, as smartphones are becoming more multiband, enabling them to handle multiple frequency bands, attention is being focused on devices made from the above-mentioned LT and LN materials.

[0005] A known processing apparatus for grinding the above-mentioned bonded wafer includes a grinding apparatus including a rotatable chuck table that holds the wafer by suction, a moving means for moving the chuck table to a mounting and demounting area where the wafer is mounted and detached, and a grinding area where the wafer is ground, a loading means for loading the wafer onto the chuck table in the mounting and demounting area, a loading means for unloading the ground wafer from the chuck table, and a grinding means that is disposed in the grinding area and has a rotatable grinding wheel that grinds the wafer held on the chuck table while supplying grinding water to the wafer (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent Publication No. 2021-137909 Summary of the Invention [Problem to be solved by the invention]

[0007] The above-mentioned LT wafers and LN wafers are materials that have high cleavage properties and are very difficult to grind. For example, when a 350 μm-thick LT wafer bonded to a silicon substrate or the like is ground to 5 μm by a grinding device, the LT wafer or LN wafer may crack and may be partially peeled off from the bonded silicon substrate or the like.

[0008] Furthermore, when a bonded wafer in which the LT wafer or LN wafer has been partially peeled off from the silicon substrate or the like during grinding is carried out by a carrying-out means, the thinned LT wafer or LN wafer peels off from the silicon substrate or the like and adheres to the suction pad constituting the carrying-out means, and when the next bonded wafer is carried out, the suction force becomes insufficient and the next bonded wafer cannot be carried out normally, causing the bonded wafer to fall or be damaged when it is being carried out.

[0009] The present invention has been made in view of the above-mentioned circumstances, and its main technical object is to provide a wafer processing method and processing apparatus which can prevent the peeled LT wafer or LN wafer from adhering to the suction pads constituting the carrying-out means even if the LT wafer or LN wafer bonded to a silicon substrate or the like is partially peeled off during grinding of the LT wafer or LN wafer, thereby eliminating the problem that the suction force becomes insufficient when the next bonded wafer is carried out, causing the wafer to drop and be damaged. [Means for solving the problem]

[0010] In order to solve the above-mentioned main technical problem, according to the present invention, there is provided a wafer processing method for grinding and thinning a bonded wafer in which a first wafer and a second wafer are bonded together, the method comprising the steps of: preparing a grinding device including a rotatable chuck table for holding a wafer; grinding means having a rotatable grinding wheel with grinding wheels arranged in an annular shape for grinding the wafer held on the chuck table; grinding feed means for moving the grinding means toward and away from the wafer held on the chuck table; and a load meter for measuring a load when the grinding wheels come into contact with the wafer held on the chuck table; The wafer processing method includes a wafer holding step of holding the second wafer side of the wafer to expose the first wafer, a grinding step of rotating the bonded wafer held on the chuck table, rotating the grinding wheel, and operating the grinding feed means to grind the first wafer with the grinding wheel, a separating step of determining that the first wafer has been peeled off from the second wafer when a value measured by the load meter changes suddenly, and operating the grinding feed means to separate the grinding wheel from the first wafer, and a determination step of detecting the peeled state of the first wafer and determining whether or not it is acceptable to transport the bonded wafer from the chuck table by a transport means.

[0011] It is preferable that the first wafer contains lithium tantalate or lithium niobate, and the second wafer contains any one of silicon, sapphire, quartz, and glass.

[0012] According to the present invention, there is also provided a wafer processing apparatus for grinding and thinning a first wafer in a bonded wafer formed by bonding a first wafer and a second wafer, the apparatus comprising: a rotatable chuck table for holding the second wafer side of the bonded wafer; grinding means for rotatably including a grinding wheel having grinding stones arranged in an annular shape for grinding the first wafer side of the bonded wafer held on the chuck table; grinding feed means for moving the grinding means toward and away from the bonded wafer held on the chuck table; The present invention provides a processing apparatus including: a load meter that measures the load when the grinding wheel comes into contact with the bonded wafer held on the chuck table; detection means that detects the degree of peeling of a first wafer from the bonded wafer held on the chuck table; positioning means that positions the bonded wafer in a load / unload area where the bonded wafer is loaded and unloaded onto the chuck table and in a grinding area where grinding is performed by the grinding means; unloading means that unloads the bonded wafer from the chuck table positioned in the load / unload area; and control means.

[0013] It is preferable that when the value measured by the load meter changes suddenly while the first wafer side of the bonded wafer is being ground with a grinding wheel, the control means determines that the first wafer has been peeled off from the second wafer and operates the grinding feed means to move the grinding means away from the first wafer.

[0014] It is also preferable that the control means detects the peeled state of the first wafer by the detection means, judges whether or not it is OK to transport the bonded wafer from the chuck table by the transporting means, and permits the transport by the transporting means if the first wafer remaining exceeds the size of the suction pad constituting the transporting means, and prohibits the transport by the transporting means if the remaining first wafer is smaller than the size of the suction pad. Further, the grinding means preferably comprises a first grinding means rotatably equipped with a grinding wheel for rough grinding, and a second grinding means rotatably equipped with a grinding wheel for finish grinding, and at least three chuck tables are arranged, and a turntable which positions a first grinding area where processing is performed by the first grinding means, a second grinding area where processing is performed by the second grinding means, and a load / unload area where wafers are loaded and unloaded onto the chuck table, and the control means preferably operates the grinding feed means to move the second grinding means away from the first grinding means and to make the second grinding means wait, and after grinding of the bonded wafer being ground by the first grinding means is completed, rotates the turntable to position the bonded wafer from which the first wafer has been peeled off in the load / unload area. Effect of the Invention

[0015] The wafer processing method of the present invention includes a preparation step of preparing a grinding device including a rotatable chuck table for holding a wafer, grinding means having a rotatable grinding wheel with grinding stones arranged in an annular shape for grinding the wafer held on the chuck table, grinding feed means for moving the grinding means toward and away from the wafer held on the chuck table, and a load meter for measuring a load when the grinding stone comes into contact with the wafer held on the chuck table; a wafer holding step of holding a second wafer side of a bonded wafer on the chuck table to expose a first wafer; and a wafer holding step of rotating the bonded wafer held on the chuck table and feeding the grinding wheel. and a separating step of determining, when a value measured by the load meter changes suddenly, that the first wafer has been peeled off from the second wafer and operating the grinding feed means to separate the grinding wheel from the first wafer. Since this method includes the steps of: a grinding step of rotating the chuck table and operating the grinding feed means to grind the first wafer with the grinding wheel; a separating step of determining, when a value measured by the load meter changes suddenly, that the first wafer has been peeled off from the second wafer and operating the grinding feed means to separate the grinding wheel from the first wafer; and a judgment step of detecting the peeled state of the first wafer and judging whether or not it is OK to carry the bonded wafer off from the chuck table by the carrying-out means, it is possible to prevent the thinned first wafer from peeling off and adhering to the carrying-out means, and the problem of insufficient suction force when carrying out the next bonded wafer is eliminated.

[0016] The processing apparatus of the present invention further comprises a rotatable chuck table for holding the second wafer side of the bonded wafer, grinding means having a rotatable grinding wheel with annularly arranged grinding stones for grinding the first wafer side of the bonded wafer held on the chuck table, grinding feed means for moving the grinding means toward and away from the bonded wafer held on the chuck table, a load meter for measuring a load when the grinding stone comes into contact with the bonded wafer held on the chuck table, and a load meter for moving the first wafer side from the bonded wafer held on the chuck table. Since the system is configured to include a detection means for detecting the degree of peeling of the first wafer, a positioning means for positioning the bonded wafer in a load / unload area where the bonded wafer is loaded and unloaded onto the chuck table and in a grinding area where grinding is performed by the grinding means, an unloading means for unloading the bonded wafer from the chuck table positioned in the load / unloading area, and a control means, it is possible to prevent the thinned first wafer from peeling off and adhering to the unloading means, and the problem of insufficient suction force when unloading the next bonded wafer, causing damage, is eliminated. [Brief description of the drawings]

[0017] [Figure 1] 1 is an exploded perspective view showing a bonded wafer processed by the wafer processing method of the present embodiment. FIG. [Diagram 2] 2 is an overall perspective view of a grinding apparatus for grinding the bonded wafer shown in FIG. 1. [Diagram 3] 3 is a side view showing an internal configuration of the device housing relating to a second grinding unit, with a part of the device housing of the grinding device shown in FIG. 2 in cross section. FIG. [Figure 4] 3 is an enlarged perspective view showing a portion including a suction pad of a carrying-out means of the grinding device shown in FIG. 2. FIG. [Diagram 5] FIG. 13 is a perspective view showing an embodiment of a finish grinding step performed by a second grinding means. [Figure 6] FIG. 2A is a perspective view showing an embodiment of the determination step of the present embodiment, and FIG. 2B is a conceptual diagram showing a peeled state of the first wafer detected by the determination step shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of a wafer processing method and processing apparatus according to the present invention will be described in detail with reference to the accompanying drawings.

[0019] FIG. 1 shows an example of a bonded wafer W processed by the wafer processing method of the present embodiment. As shown in the figure, the bonded wafer W is composed of a first wafer 10 that is ground by a wafer processing method and processing device described later, and a second wafer 20 that is bonded to the first wafer 10 and supports the first wafer 10. The diameter of the bonded wafer W shown in the figure is, for example, 200 mm, and the first wafer 10 is, for example, a LT (lithium tantalate (LiTaO3)) wafer with a thickness of 350 μm. The second wafer 20 is a silicon (Si) wafer that functions as a support substrate that supports the first wafer 10 and has a thickness of 350 mm. The bonded wafer W is formed by bonding a surface 10a of the first wafer 10 and a surface 20a of the second wafer 20 by, for example, well-known room temperature bonding.

[0020] According to the wafer processing method of the present embodiment described below, the back surface 10b of the first wafer 10 is ground to a desired thickness, and then electrodes are formed in each region defined by a division line (not shown) in the first wafer 10, and the first wafer 10 is divided into individual devices along the division lines to form TF-SAW devices. The wafer bonded to the second wafer 20 is not limited to the above-mentioned LT wafer, and an LN (lithium niobate (LiNbO3)) wafer may be adopted, and the second wafer 20 supporting the first wafer 10 is not limited to the above-mentioned silicon wafer, and may be, for example, any of sapphire, quartz, and glass wafers.

[0021] The processing apparatus constructed according to the present invention is a grinding apparatus including a chuck table for holding a wafer, grinding means having a rotatable grinding wheel with grinding wheels arranged in a ring shape for grinding the wafer held on the chuck table, grinding feed means for moving the grinding means toward and away from the wafer held on the chuck table, and a load meter for measuring the load when the grinding wheels come into contact with the wafer held on the chuck table. The grinding apparatus 1 of this embodiment will be described in more detail with reference to FIGS. 2 and 3.

[0022] As shown in Fig. 2, the grinding device 1 includes a roughly rectangular parallelepiped housing 2, and a support wall 2a is erected on the rear end side of the housing 2. Two pairs of guide rails 2b, 2b and 2c, 2c extending in the vertical direction (Z-axis direction) are provided on the inner surface of the support wall 2a. A first grinding means 3 as a rough grinding means is mounted on one of the guide rails 2b, 2b so as to be movable in the vertical direction, and a second grinding means 4 as a finish grinding means is mounted on the other guide rails 2c, 2c so as to be movable in the vertical direction.

[0023] The first grinding means 3 comprises a unit housing 31, a wheel mount 33 arranged at the lower end of a rotating shaft 32 supported rotatably on the unit housing 31, a grinding wheel 34 attached to the wheel mount 33 and having a ring-shaped grinding wheel 35 for rough grinding arranged on its underside, an electric motor 36 attached to the upper end of the unit housing 31 for rotating the wheel mount 33 in the direction indicated by arrow R1, and a movable base 38 supporting the unit housing 31 via a support member 37.

[0024] The movable base 38 is provided with a guided groove that slidably engages with the guide rails 2b, 2b, and supports the first grinding means 3 so as to be movable in the vertical direction. The illustrated grinding device 1 is provided with a grinding feed means 39 that raises and lowers the movable base 38 of the first grinding means 3 along the guide rails 2b, 2b, and moves the first grinding means 3 toward and away from the bonded wafer W held on the chuck table 6 described below. The grinding feed means 39 is provided with a male screw rod 391 that is rotatably supported on the support wall 2a and disposed in parallel with the guide rails 2b, 2b in the vertical direction, a pulse motor 392 for rotating the male screw rod 391, and a female screw block (not shown) that is attached to the movable base 38 and screwed with the male screw rod 391. The male screw rod 391 is driven in the forward and reverse directions by the pulse motor 392 to move the first grinding means 3 in the vertical direction.

[0025] The second grinding means 4 for performing finish grinding is also configured in a manner substantially similar to the first grinding means 3 described above, and includes a unit housing 41, a wheel mount 43 arranged at the lower end of a rotating shaft 42 supported rotatably on the unit housing 41, a grinding wheel 44 attached to the wheel mount 43 and having a plurality of grinding wheels 45 for finish grinding arranged in a ring shape on its underside, an electric motor 46 attached to the upper end of the unit housing 41 for rotating the wheel mount 43 in the direction indicated by arrow R2, and a movable base 48 for supporting the unit housing 41 via a support member 47.

[0026] The movable base 48 is provided with a guided groove that slidably engages with the guide rails 2c, 2c provided on the support wall 2a, and the second grinding means 4 is supported so as to be movable in the vertical direction. The illustrated grinding device 1 is provided with a grinding feed means 49 that raises and lowers the movable base 48 of the second grinding means 4 along the guide rails 2c, 2c, and moves the second grinding means 4 toward and away from the bonded wafer W held on the chuck table 6 described below. The grinding feed means 49 is provided with a male screw rod 491 that is rotatably supported and disposed in parallel with the guide rails 2c, 2c on the support wall 2a in the vertical direction, a pulse motor 492 for rotating the male screw rod 491, and a female screw block (not shown) that is attached to the movable base 48 and screwed with the male screw rod 491. The male screw rod 491 is driven in the forward and reverse directions by the pulse motor 492 to move the second grinding means 4 in the vertical direction.

[0027] The grinding apparatus 1 is provided with a turntable 5 disposed in front of the support wall 2a so as to be substantially flush with the upper surface of the apparatus housing 2. The turntable 5 is formed in a relatively large-diameter disk shape, and is rotated appropriately by a rotary drive mechanism not shown in FIG. 2 in a drain pan 2d that collects grinding water containing grinding chips on the upper surface of the apparatus housing 2. The turntable 5 is provided with three chuck tables 6 disposed as holding means for holding the bonded wafer W at an angle of 120 degrees. Each chuck table 6 is configured to be rotatable in the direction indicated by the arrow R4. The holding surface (upper surface) of the chuck table 6 is formed in a disk shape using a breathable material.

[0028] The three chuck tables 6 arranged on the turntable 5 are moved in sequence from a carry-in / out area A where the bonded wafer W is carried in and out of the chuck table 6, to a first grinding area B where rough grinding is performed by the first grinding means 3, to a second grinding area C where finish grinding is performed by the second grinding means 4, to the carry-in / out area A, by rotating the turntable 5 in the direction indicated by the arrow R3. That is, the turntable 5 functions as a positioning means for positioning the chuck table 6 in the carry-in / out area A, the first grinding area B, and the second grinding area C. Furthermore, optical non-contact thickness detection means 71 and 72 for detecting the thickness (height) of the bonded wafer W held on the chuck table 6 are arranged in positions adjacent to the first grinding area B and the second grinding area C in the above-mentioned drain pan 2d.

[0029] 3 is a side view showing an internal configuration of the device housing 2 relating to the second grinding means 4, with a part of the device housing 2 in cross section. As can be seen from FIG. 3, the chuck table 6 is disposed on a turntable base 52 which rotates together with the turntable 5, and the turntable 5 and the turntable base 52 are rotated by a rotary drive mechanism 51 which rotates the turntable. The chuck table 6 includes a servo motor 61 for rotating the chuck table 6 in the direction indicated by the arrow R4 in FIG. 2, a rotary encoder 62 for detecting the rotation angle of the servo motor 61, and a rotary shaft 63 for transmitting the rotation of the servo motor 61 to the chuck table 6, and further includes a load meter 64 for measuring the load when the grinding wheel 45 contacts the bonded wafer W held on the chuck table 6 by operating the grinding feed means 49 to lower the second grinding means 4 in the direction indicated by the arrow R7. The configuration of the chuck table 6 described above is common to all three chuck tables 6 arranged on the turntable 5, and each chuck table 6 is provided with the servo motor 61, rotary encoder 62, rotating shaft 63, and load meter 64 described above.

[0030] Returning to FIG. 2 , the grinding apparatus 1 includes a first cassette 7 arranged on one side of the loading / unloading area A and accommodating a plurality of bonded wafers W before grinding, a second cassette 8 arranged on the other side of the loading / unloading area A and accommodating a plurality of bonded wafers W after grinding, alignment means 9 arranged between the first cassette 7 and the loading / unloading area A and on which the bonded wafers W are temporarily placed and centered, cleaning means 11 arranged between the loading / unloading area A and the second cassette 8, and a cleaning means 20 for cleaning the bonded wafers W accommodated in the first cassette 7 using the alignment means. 9 and the bonded wafer W cleaned by the cleaning means 11 is transported into the second cassette 8, a transport means 13 which transports the wafer W aligned on the alignment means 9 onto the chuck table 6 positioned in the load / unload area A, and a transport means 14 which adsorbs the ground bonded wafer W, which has been ground by the second grinding means 4 and is held on the chuck table 6 positioned in the load / unload area A, by a suction pad 142, transports it out, and transports it to the cleaning means 11.

[0031] The transport means 13 includes an arm member 131 that rotates in the direction indicated by an arrow R5 in FIG. 2, and a circular suction pad 132 formed at the tip of the arm member 131. The unloading means 14 includes an arm member 141 that rotates in the direction indicated by an arrow R6 in FIG. 2, and a suction pad 142 formed at the tip of the arm member 141. FIG. 4 shows an enlarged perspective view of a part of the area where the suction pad 142 of the unloading means 14 is formed. As shown in the figure, the suction pad 142 has a disk shape with a diameter D1, and a plurality of holes (not shown) are formed in the entire area of ​​the lower surface 142a. A suction means (not shown) is connected to the suction pad 142 via the arm member 141, and by operating the suction means, a negative pressure is generated on the lower surface 142a of the suction pad 142, so that the bonded wafer W can be suctioned. The diameter D1 of the suction pad 142 is set smaller than the diameter (200 mm) of the bonded wafer W, and is, for example, 100 mm.

[0032] A control means 100 including an operation panel for instructing grinding work and specifying processing conditions is disposed on the front side of the device housing 2 where the workpiece carrying-in / out means 12 is disposed. The control means 100 includes a central processing unit (CPU) that performs calculation processing according to a control program, a read-only memory (ROM) that stores the control program, etc., a readable / writable random access memory (RAM) as a storage means for storing calculation results, etc., an input interface, and an output interface (all of which are omitted from the drawing). The control means 100 configured in this manner controls each operating part of the grinding device 1, and also appropriately displays information related to processing, etc. on a display means (not shown).

[0033] The grinding apparatus 1 of this embodiment has roughly the configuration as described above, and the wafer processing method carried out by the grinding apparatus 1 will be described below.

[0034] (preparation process) When carrying out the wafer processing method of this embodiment, first, a preparation step is carried out to prepare the above-mentioned grinding apparatus 1. The grinding apparatus 1 prepared here is a grinding apparatus configured to include at least the rotatable chuck table 6 that holds the above-mentioned bonded wafer W, the second grinding means 4 that is rotatably provided with a grinding wheel 44 having annularly arranged grinding stones 45 that perform finish grinding on the bonded wafer W held on the chuck table 6, a grinding feed means 49 that moves the second grinding means 4 toward and away from the bonded wafer W held on the chuck table 6, and a load meter 64 that measures the load when the grinding stone 45 comes into contact with the bonded wafer W held on the chuck table 6.

[0035] (Wafer holding process) After the above-mentioned preparation step, a wafer holding step is performed in which the above-mentioned bonded wafer W is transported to the chuck table 6 positioned in the load / unload area A, the second wafer 20 side is placed downward and the first wafer 10 side is placed upward, and a suction means (not shown) is operated to hold the bonded wafer W by suction, exposing the first wafer 10 upward. The wafer holding step performed in this embodiment includes a carry-out step in which the workpiece carry-in / out means 12 carries out the unprocessed bonded wafer W from the first cassette 7, a positioning step in which the bonded wafer W carried out by the workpiece carry-in / out means 12 is placed on the positioning means 9 and the center of the bonded wafer W is aligned, and a holding step in which the transport means 13 is operated to transport the bonded wafer W from the positioning means 9 to the chuck table 6 positioned in the load / unload area A, the first wafer 10 is placed upward, and a suction means (not shown) is operated to hold the bonded wafer W by suction.

[0036] (Grinding process) The grinding process of this embodiment, which is performed after the above-mentioned wafer holding process, includes a rough grinding step for performing rough grinding on the first wafer 10 and a finish grinding step for performing finish grinding on the first wafer 10. After performing the wafer holding process as described above, the turntable 5 is rotated 120° in the direction indicated by the arrow R3, and the chuck table 6 holding the bonded wafer W is positioned in the first grinding region B shown in Fig. 2. Next, the chuck table 6 is rotated in the direction indicated by the arrow R4 at a predetermined rotational speed (e.g., 300 rpm) to rotate the bonded wafer W held on the chuck table 6, and the grinding wheel 34 of the first grinding means 3 is rotated at a predetermined rotational speed (e.g., 6000 rpm). Next, the grinding feed means 39 is operated to lower the first grinding means 3 downward, and the grinding wheel 35 is brought into contact with the bonded wafer W while grinding water is supplied to the grinding location where the bonded wafer W and the grinding wheel 35 come into contact by a grinding water supply means (not shown), and then the grinding wheel 35 is fed at a predetermined grinding feed speed (e.g., 1.0 μm / sec) to roughly grind the upper surface of the first wafer 10 with the grinding wheel 35 (rough grinding step). The chuck table 6 is provided with the above-mentioned load meter 64, which can detect that the grinding wheel 35 has come into contact with the bonded wafer W and can manage the load applied to the bonded wafer W during rough grinding. Moreover, this rough grinding step can be performed while detecting the thickness of the bonded wafer W by the non-contact thickness detection means 71 described above, and the rough grinding step is performed until the thickness (350 μm) of the first wafer 10 before processing is reduced to 20 μm.

[0037] When the rough grinding step is completed, the turntable 5 is rotated by 120° in the direction indicated by the arrow R3, and the chuck table 6, which has completed the rough grinding step for the bonded wafer W, is moved from the first grinding area B to the second grinding area C. At this time, the chuck table 6, which is moved from the carry-in / out area A to the first grinding area B, holds the unprocessed bonded wafer W that has been previously subjected to the wafer holding step, and the unprocessed bonded wafer W is positioned in the first grinding area B. Then, when the chuck table 6 is positioned in the second grinding area C, as shown in FIG. 5, the chuck table 6 is rotated in the direction indicated by the arrow R9 at a predetermined rotational speed (e.g., 300 rpm) to rotate the bonded wafer W held on the chuck table 6, and the rotating shaft 42 of the second grinding means 4 is rotated in the direction indicated by the arrow R8 at a predetermined rotational speed (e.g., 6000 rpm) to rotate the grinding wheel 44.

[0038] Next, the above-mentioned grinding feed means 49 is operated to lower the second grinding means 4 in the direction indicated by the arrow R10 in the figure, the above-mentioned load meter 64 detects that the grinding wheel 45 of the second grinding means 4 has come into contact with the bonded wafer W, and while grinding water is supplied to the grinding point by a grinding water supply means (not shown), the grinding is fed at a predetermined grinding feed speed (e.g., 0.05 μm / sec), and the upper surface of the first wafer 10 is finish-ground by the grinding wheel 45 (finish grinding step). Note that this finish grinding step can be performed while detecting the thickness of the bonded wafer W by the above-mentioned non-contact thickness detection means 72, and is performed until the thickness (20 μm) of the first wafer 10 before the finish grinding is reduced to 5 μm. Incidentally, while the finish grinding step is being carried out in the second grinding area C, the above-mentioned rough grinding step is being carried out simultaneously in the first grinding area B, and a wafer holding process is carried out on the chuck table 6 positioned in the loading / unloading area A, where the unprocessed bonded wafer W is transported from the first cassette 7, placed on it, and held by suction.

[0039] (Separation process) During the finish grinding step in the above-mentioned grinding process, when the second grinding means 4 is being fed by the grinding feed means 49, the load applied to the chuck table 6 via the bonded wafer W is measured by the load meter 64 and monitored by the control means 100. As the thickness of the first wafer 10 approaches the desired thickness of 5 μm, the risk of the first wafer 10 peeling off from the second wafer 20 increases. If the first wafer 10 peels off from the second wafer 20 while the first wafer 10 is being ground by the second grinding means 4, the first wafer 10 that was in contact with the polishing wheel 45 will instantly no longer be in contact with the grinding wheel 45, and the load measured by the load meter 64 will suddenly change to a decreasing direction. Therefore, when the control means 100 detects this sudden change in load, it determines that the first wafer 10 has been peeled off from the second wafer 20, stops the execution of the finish grinding step, and operates the grinding feed means 49 to execute a separation step of separating the grinding wheel 45 from the first wafer 10. If the load measured by the load meter 64 does not change suddenly and reaches the desired thickness of 5 μm for the first wafer 10, the above-mentioned separation step is not executed, the finish grinding step ends, and the grinding step for the bonded wafer W is completed. If the separation step is not executed and the first wafer 10 is normally ground to the desired thickness, the turntable 5 is rotated to move the chuck table 6 to the carry-in / out area A, the bonded wafer W is carried out by the carry-out means 14, washed and dried by the cleaning means 11, and the workpiece carry-in / out means 12 is operated to store the cleaned bonded wafer W in the second cassette 8.

[0040] (judgment process) When the separating step is performed as described above, a judgment step is performed in which the peeled state of the first wafer 10 is detected and it is judged whether or not the bonded wafer W can be carried out from the chuck table 6 by the carrying-out means 14. More specifically, as shown in FIG. 6(a), the non-contact type thickness detection means 72 is positioned above the bonded wafer W supported on the chuck table 6 and moved horizontally in the direction indicated by the arrow R11, and the non-contact type thickness detection means 72 scans the bonded wafer W so as to pass through the center while measuring the surface height with the detection portion 72a of the non-contact type thickness detection means 72. Thereby, the height of the upper surface of the bonded wafer W is measured as shown in FIG. 6(b). In FIG. 6(b), the vertical axis indicates the height (μm) detected by the non-contact type thickness detection means 72, and the horizontal axis indicates the length (mm) corresponding to the diameter of the bonded wafer W. According to the detection result shown in FIG. 6(b), the height is detected to be P1 in the central range indicated by D2, and the height is detected to be P2 in the outer region. 6(a), it is detected that the first wafer 10 remains in the central region of the upper surface of the bonded wafer W, and the first wafer 10 is peeled off in the outer peripheral region. Since the path scanned by the detection unit 72a of the non-contact thickness detection means 72 is arc-shaped, the diameter D2 of the region where the first wafer 10 remains is calculated from the length of the region indicating the height P1 detected by the arc. Furthermore, since the region where the first wafer 10 remains does not necessarily have a perfect circular shape, the range determined based on the above D2 is merely the region where the first wafer 10 is estimated to remain.

[0041] Here, as described above, since the diameter of the suction pad 142 of the unloading means 14 for unloading the bonded wafer W from the chuck table 6 positioned in the loading / unloading area A is D1 (= 100 mm), the control means 100 determines whether D2 ≥ D1. If D2 ≥ D1, it is determined that the bonded wafer W can be properly unloaded by the suction pad 142 of the unloading means 14. Also, if D2 < D1, that is, when D2 < D1, it means that the range where the first wafer 10 has been peeled off extends to the area adsorbed by the suction pad 142. When unloading the bonded wafer W from which the first wafer 10 has been peeled off by the unloading means 14, the thin first wafer 10 adheres to the suction pad 142, and when unloading the next bonded wafer W, the suction force becomes insufficient, and there is a risk of damaging the bonded wafer W. Therefore, it is determined that the bonded wafer W should not be unloaded by the unloading means 14.

[0042] Here, after performing the above-described separation step and determination step, the turntable 5 is rotated, and the chuck table 6 holding the bonded wafer W in a state where the first wafer 10 has been peeled off is moved from the second grinding area C to the loading / unloading area A, and it is necessary to unload the bonded wafer W from which the first wafer 10 has been peeled off. However, in the second grinding area C, at the same time as the above-described finish grinding step is performed, in the first grinding area B, the rough grinding step is being performed by the above-described first grinding means 3. Therefore, even when the separation step is performed as described above and the grinding feed means 49 is operated to separate the second grinding means 4 from the chuck table 6, the turntable 5 is not rotated until the rough grinding step of the bonded wafer W with respect to the first wafer 10 performed by the first grinding means 3 is completed, and the second grinding means 4 is left in a state of being separated from the chuck table 6 and waiting. Then, when the rough grinding step is completed, the turntable 5 is rotated, and the chuck table 6 holding the bonded wafer W from which the first wafer 10 has been peeled off is positioned in the loading / unloading area A.

[0043] When it is determined by the above-mentioned determination step that the bonded wafer W should not be carried out by the carrying-out means 14, the control means 100 prohibits the carrying-out means 14 from carrying out the bonded wafer W from the chuck table 6 positioned in the carrying-in / out area A, and notifies the operator of the prohibition. The means for notifying the operator is not particularly limited, but may be, for example, a display on a display means (not shown), a buzzer, or a combination of these. Then, the operator, who has grasped that the carrying-out means 14 is prohibited from carrying out the bonded wafer W from the chuck table 6, manually carries out the bonded wafer W from which the first wafer 10 has been peeled off, from the chuck table 6 positioned in the carrying-in / out area A. This prevents the thinned first wafer 10 from adhering to the suction surface on the lower surface 142a side of the suction pad 142 of the carrying-out means 14. In addition, in the above-mentioned determination step, if it is determined that the bonded wafer W may be unloaded by the unloading means 14, the bonded wafer W is unloaded from the chuck table 6 by the unloading means 14, transported to the cleaning means 11, cleaned and dried, and then stored in the second cassette 8, as in the normal unloading procedure. In this embodiment, as described above, when the separating step is performed, the turntable 5 is not rotated and the second grinding means 4 is kept waiting in a separated state until the rough grinding step performed by the first grinding means 3 is completed. Therefore, after the operator manually unloads the bonded wafer W from the chuck table 6 in the loading / unloading area A, the operation of the grinding apparatus 1 can be resumed as it is.

[0044] According to the embodiment described above, while the grinding process is being performed on the first wafer 10 of the bonded wafer W, it is possible to quickly grasp that the first wafer 10 has peeled off from the second wafer 20 and to determine whether or not it is OK to transport the bonded wafer W by the transporting means 14. This makes it possible to prevent the thinned first wafer 10 from peeling off and adhering to the suction pad 142 constituting the transporting means 14, thereby eliminating the problem of insufficient suction force when transporting the next bonded wafer W, causing damage to the wafer.

[0045] In the determination step described with reference to Fig. 6, the upper surface of the bonded wafer W is scanned in one direction by the detection unit 72a of the non-contact type thickness detection means 72 to detect the peeled state of the first wafer 10, but the present invention is not limited to this. For example, the non-contact type thickness detection means 72 may be swung in the direction indicated by the arrow R11 while rotating the chuck table 6 by a predetermined angle in the direction indicated by the arrow R12 to scan the upper surface of the bonded wafer W by the detection unit 72a to detect the area where the first wafer 10 remains in a plurality of directions. In this way, the area where the first wafer 10 remains can be detected more accurately, and it can be more accurately determined whether the first wafer 10 remains in a range where it can be sucked by the suction pad 142.

[0046] The grinding apparatus 1 of the above embodiment is provided with three chuck tables 6 and is provided with a first grinding means 3 for performing rough grinding and a second grinding means 4 for performing finish grinding, thereby performing a rough grinding step and a finish grinding step, and an example is shown in which the wafer processing method of the present invention is performed using this grinding apparatus 1, but the present invention is not limited to this. For example, the grinding apparatus configured based on the present invention may be provided with three or more chuck tables, or may be a grinding apparatus provided with only one chuck table and grinding means and performing only finish grinding, and in either case, the wafer processing method performed based on the present invention can be performed. [Explanation of symbols]

[0047] 1: Grinding device 2: Device housing 2a: Support wall 2b: Guide rail 2c: Guide rail 2d: Drain pan 3: First grinding method 31: Unit housing 32: Rotation axis 33: Wheel mount 34: Grinding wheel 35: Grinding wheel 36: Electric motor 37: Support member 38: Mobile base 39: Grinding feed means 4: Second grinding method 41: Unit housing 42: Rotation axis 43: Wheel mount 44: Grinding wheel 45: Grinding wheel 46: Electric motor 47: Support member 48: Mobile base 49: Grinding feed means 5: Turntable 51: Rotation drive mechanism 52: Turntable base 6: Chuck table 61: Servo motor 62: Rotary encoder 63: Rotation axis 64:Load cell 7: First Cassette 8: Second Cassette 9: Alignment means 10: First wafer 11: Cleaning method 12: Workpiece loading / unloading means 13: Means of transportation 14:Export means 20: Second Wafer 71, 72: Non-contact thickness detection means A: Loading / unloading area B: First grinding area C: Second grinding area W: Bonded wafer

Claims

1. A wafer processing method for thinning a bonded wafer in which a first wafer and a second wafer are bonded together, the method comprising: a preparation step of preparing a grinding device including a rotatable chuck table for holding a wafer, grinding means having a rotatable grinding wheel with grinding stones arranged in an annular shape for grinding the wafer held on the chuck table, grinding feed means for moving the grinding means toward and away from the wafer held on the chuck table, and a load meter for measuring a load when the grinding stone comes into contact with the wafer held on the chuck table; a wafer holding step of holding the second wafer side of the bonded wafer on the chuck table to expose the first wafer; a grinding step of rotating the bonded wafer held on the chuck table, rotating the grinding wheel, and operating the grinding feed means to grind the first wafer with the grinding wheel; a separating step of determining that the first wafer has been peeled off from the second wafer when a value measured by the load meter changes suddenly, and operating the grinding feed means to separate the grinding wheel from the first wafer; a determination step of detecting a peeled state of the first wafer and determining whether or not the bonded wafer may be unloaded from the chuck table by a unloading means; A wafer processing method comprising the steps of:

2. 2. The wafer processing method according to claim 1, wherein the first wafer is comprised of lithium tantalate or lithium niobate, and the second wafer is comprised of any one of silicon, sapphire, quartz, and glass.

3. A wafer processing apparatus for grinding and thinning a first wafer in a bonded wafer in which a first wafer and a second wafer are bonded together, comprising: a grinding means for moving the grinding means toward and away from the bonded wafer held on the chuck table; a load meter for measuring a load when the grinding wheel comes into contact with the bonded wafer held on the chuck table; a detection means for detecting a degree of peeling of the first wafer from the bonded wafer held on the chuck table; a positioning means for positioning the bonded wafer to a load / unload area where the bonded wafer is loaded and unloaded onto the chuck table and to a grinding area where grinding is performed by the grinding means;

4. 4. The processing apparatus according to claim 3, wherein when the value measured by the load meter changes suddenly when the first wafer side of the bonded wafers is ground with a grinding wheel, the control means determines that the first wafer has been peeled off from the second wafer and operates the grinding feed means to move the grinding means away from the first wafer.

5. 5. The processing apparatus according to claim 4, wherein the control means detects a peeled state of the first wafer by the detection means, judges whether or not it is OK to carry the bonded wafer out of the chuck table by the carrying-out means, and permits the carrying-out means to carry out the first wafer if the first wafer remains in excess of a size of a suction pad constituting the carrying-out means, and prohibits the carrying-out means from carrying out the first wafer if the remaining first wafer is smaller than the size of the suction pad.

6. the grinding means comprises a first grinding means rotatably equipped with a grinding wheel for rough grinding, and a second grinding means rotatably equipped with a grinding wheel for finish grinding, at least three chuck tables are arranged, and a turntable is provided for positioning a first grinding area where processing is performed by the first grinding means, a second grinding area where processing is performed by the second grinding means, and a transfer area where the wafer is transferred to and from the chuck table; 6. The processing apparatus according to claim 5, wherein, when the value measured by the load meter changes suddenly while the first wafer of the bonded wafers is being ground by the second grinding means, the control means operates the grinding feed means to move the second grinding means away and make it wait, and after grinding of the bonded wafer being ground by the first grinding means is completed, the control means rotates the turntable to position the bonded wafer from which the first wafer has been peeled off in the load / unload area.

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