Wafer processing method and processing device

Abstract

To provide a wafer processing method and a processing device, capable of removing an outer peripheral region while suppressing damages to a wafer in a grinding step of a bonded wafer.SOLUTION: A wafer processing method comprises: a bonded wafer formation step 101 of forming a bonded wafer by bonding a first wafer and a second wafer; a modification layer formation step 102 of radiating a laser beam in an annular shape along a position on the side by a predetermined distance inner from an outer peripheral edge and forming an annular modified layer inside the first wafer and a crack extended to a front surface side from the modified layer to generate wrapping in an outer peripheral region; a detection step 103 of detecting a wrapping amount of the outer peripheral region; a determination step 104 of determining whether or not the bonding of the first wafer and the second wafer is cancelled on the basis of the wrapping amount of the outer peripheral region, and deciding whether or not the grinding step 105 is executed; and a grinding step 105 that grinds the first wafer from a back surface side.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a wafer processing method and processing apparatus. [Background technology]

[0002] In recent years, the development of 3D stacked semiconductor wafers has progressed in line with the trend toward lower profile and higher integration of device chips. For example, TSV (Through-Silicon Via) wafers enable the connection of electrodes between two chips by bonding them together using through-hole electrodes.

[0003] Such wafers are ground and thinned while bonded to a support wafer (silicon, glass, ceramics, etc.) that serves as a base. Normally, the outer edge of a wafer is chamfered, so when the wafer is ground to an extremely thin thickness, the outer edge becomes a so-called knife edge, and the edge is likely to chip during grinding. This may cause the chip to extend to the device, leading to damage to the device.

[0004] As a countermeasure to the knife edge, an edge trimming method has been devised in which wafers are bonded together and then a laser beam is irradiated along the outer edge of the device to form an annular modified layer, thereby preventing chipping of the wafer edge that occurs during grinding from extending into the device (see Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2020-057709 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the method of Patent Document 1, when the modified layer is formed radially inward of the joining region, there is a possibility that the end material in the outer circumferential region will not peel off and will remain.

[0007] The present invention has been made in consideration of such problems, and its object is to provide a wafer processing method and processing apparatus that can remove the outer peripheral region while suppressing damage to the wafer in the grinding process of a bonded wafer. [Means for solving the problem]

[0008] In order to solve the above-mentioned problems and achieve the object, the wafer processing method of the present invention includes a bonded wafer forming step of bonding the front side of a first wafer having a chamfered outer periphery to a second wafer to form a bonded wafer, and an annular irradiation step of a laser beam having a wavelength that transmits the first wafer along a position a predetermined distance inside the outer periphery to form an annular modified layer inside the first wafer and a crack extending from the modified layer to the bonding surface side with the second wafer, thereby generating a warp in an outer periphery region on the outer periphery side from the modified layer and the crack. the first wafer is bonded to the second wafer by grinding the first wafer from the surface opposite to the bonding surface with the second wafer to thin the first wafer to a finish thickness, based on the amount of warpage of the outer circumferential region detected in the detection step, and further comprising a judgment step of judging whether or not the bonding between the first wafer and the second wafer in the outer circumferential region has been released based on the amount of warpage of the outer circumferential region detected in the detection step, and deciding whether or not to carry out the grinding step.

[0009] In addition, in the wafer processing method of the present invention, if it is determined in the judgment step that the amount of warpage in the outer peripheral region is equal to or greater than a predetermined value, the grinding step is carried out, and if it is determined that the amount of warpage in the outer peripheral region is less than the predetermined value, the modified layer formation step may be carried out again.

[0010] In addition, the wafer processing method of the present invention further includes a pre-detection step of detecting the amount of warpage in the outer peripheral region before performing the modified layer formation step, and a comparison step of comparing the amount of warpage detected in the pre-detection step with the amount of warpage detected in the detection step, and in the judgment step, it may be judged based on the comparison result in the comparison step whether or not the bond between the first wafer and the second wafer in the outer peripheral region has been released, and it may be determined whether or not to perform the grinding step.

[0011] In the wafer processing method of the present invention, the detection step may include measuring the height of the outer circumferential region and detecting the amount of warpage of the outer circumferential region based on the measured value of the height of the outer circumferential region.

[0012] In addition, in the wafer processing method of the present invention, the detection step may include irradiating the outer peripheral region with light and acquiring interference fringes, and detecting the amount of warping of the outer peripheral region based on the interference fringes generated in the outer peripheral region.

[0013] Furthermore, the processing apparatus of the present invention is a processing apparatus that performs at least the detection step in the wafer processing method, and is characterized in that it comprises a warpage detection unit that measures the amount of warpage in the outer peripheral region of the first wafer, and a control unit that judges whether or not the bond between the first wafer and the second wafer has been released based on the amount of warpage detected by the warpage detection unit, and determines whether or not to perform the grinding step. Effect of the Invention

[0014] The present invention can remove the outer circumferential region while suppressing damage to the wafer in a grinding process of a bonded wafer. [Brief description of the drawings]

[0015] [Figure 1] FIG. 1 is a perspective view showing an example of a wafer to be processed by the wafer processing method according to the embodiment. [Diagram 2]FIG. 2 is a cross-sectional view taken along the line II-II shown in FIG. [Diagram 3] FIG. 3 is a flowchart showing a flow of the wafer processing method according to the embodiment. [Figure 4] FIG. 4 is a perspective view showing one state of the bonded wafer forming step shown in FIG. [Diagram 5] FIG. 5 is a side view, partly in section, showing one state of the modified layer forming step shown in FIG. [Figure 6] FIG. 6 is an enlarged cross-sectional view showing a part of the bonded wafer after the modified layer forming step shown in FIG. [Figure 7] FIG. 7 is an enlarged cross-sectional view showing a part of the bonded wafer after the modified layer forming step shown in FIG. [Figure 8] FIG. 8 is a schematic diagram showing an example of the detection step shown in FIG. [Figure 9] FIG. 9 is a diagram showing an example of a measurement result of the amount of warpage in the detection step shown in FIG. [Figure 10] FIG. 10 is a side view, partially in section, showing one state of the thinning step shown in FIG. [Figure 11] FIG. 11 is a flow chart showing the flow of a wafer processing method according to a modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] The form (embodiment) for carrying out the present invention will be described in detail with reference to the drawings. The present invention is not limited to the contents described in the following embodiment. Furthermore, the components described below include those that a person skilled in the art can easily imagine and those that are substantially the same. Furthermore, the configurations described below can be appropriately combined. Furthermore, various omissions, substitutions, or modifications of the configurations can be made without departing from the gist of the present invention.

[0017] [Embodiment] A processing method for a wafer 10 and a processing apparatus 30 according to an embodiment of the present invention will be described with reference to the drawings. First, the wafer 10 to be processed will be described. Fig. 1 is a perspective view showing an example of the wafer 10 to be processed by the processing method for a wafer 10 according to the embodiment. Fig. 2 is a cross-sectional view taken along the line II-II shown in Fig. 1.

[0018] 1 and 2 is a wafer such as a disk-shaped semiconductor wafer or an optical device wafer, with a substrate 11 made of silicon (Si), sapphire (Al2O3), gallium arsenide (GaAs), silicon carbide (SiC), or the like, and in the embodiment, is a silicon wafer. The wafer 10 in the embodiment has a diameter of 300 mm and a thickness of 775 μm. As shown in FIG. 2, the wafer 10 has a chamfered outer periphery 12 such that the center in the thickness direction protrudes most toward the outer periphery, and the cross section of the wafer 10 is arc-shaped from the front surface 13 to the back surface 14 of the substrate 11.

[0019] 1, the wafer 10 has a device layer including a central region 15 on the surface 13 side of the substrate 11 and an outer periphery region 16 surrounding the central region 15. The central region 15 has a plurality of planned division lines 17 set in a lattice pattern on the surface 13 of the substrate 11, and devices 18 formed in each region partitioned by the planned division lines 17. The outer periphery region 16 is a region surrounding the central region 15 all around and in which no devices 18 are formed.

[0020] In the embodiment, the device 18 constitutes a 3D NAND flash memory and includes an electrode pad and a through electrode connected to the electrode pad. The through electrode penetrates the back surface 14 side of the substrate 11 when the substrate 11 is thinned and the devices 18 are individually separated from the wafer 10. That is, the wafer 10 of the embodiment is a so-called TSV wafer in which the individually separated devices 18 have through electrodes. Note that the wafer 10 of the present invention is not limited to a TSV wafer having through electrodes as in the embodiment, and may be a device wafer without through electrodes.

[0021] Next, the flow of the processing method of the wafer 10 will be described. FIG. 3 is a flow chart showing the flow of the processing method of the wafer 10 according to the embodiment. As shown in FIG. 3, the processing method of the wafer 10 according to the embodiment includes a bonded wafer forming step 101, a modified layer forming step 102, a detection step 103, a judgment step 104, and a grinding step 105. The processing method of the wafer 10 according to the embodiment is a method of bonding the front surface 13 side of one wafer 10 (first wafer 10-1) to the other wafer 10 (second wafer 10-2) by bonding them, forming a division starting point for removing the outer peripheral region 16, and then thinning the one wafer 10 (first wafer 10-1) to a predetermined finishing thickness 19.

[0022] In the following description, when distinguishing between the wafers 10 of the pair of wafers 10, one wafer 10 will be referred to as a first wafer 10-1 and the other wafer 10 will be referred to as a second wafer 10-2 (see FIG. 4), and when no distinction is required, the wafers will be simply referred to as wafers 10. The other, second wafer 10-2, which is not thinned, will be described as a TSV wafer similar to the first wafer 10-1 in the embodiment, but in the present invention, it may be a simple substrate wafer without a pattern.

[0023] (Bonded wafer formation step 101) Fig. 4 is a perspective view showing one state of the bonded wafer forming step 101 shown in Fig. 3. The bonded wafer forming step 101 is a step of forming a bonded wafer 20 by bonding the front surface 13 side of a first wafer 10-1 to a second wafer 10-2.

[0024] In the bonded wafer forming step 101, first, the surface 13 of the first wafer 10-1 and the surface 13 of the second wafer 10-2 are opposed to each other with a gap therebetween, as shown in Fig. 4. Next, the surface 13 of the first wafer 10-1 and the surface 13 of the second wafer 10-2 are bonded together. In this way, the bonded wafer 20 is formed.

[0025] In this case, when a bonding layer is provided between the first wafer 10-1 and the second wafer 10-2, the bonding layer is laminated on one of the front surface 13 of the first wafer 10-1 and the front surface 13 of the second wafer 10-2, and then the front surface 13 of the first wafer 10-1 and the front surface 13 of the second wafer 10-2 are bonded together via the bonding layer. The bonding layer may be a double-sided tape having an adhesive layer laminated on the front and back surfaces of a base layer, an oxide film, or a layer formed by applying an adhesive containing a resin or the like.

[0026] Alternatively, the first wafer 10-1 and the second wafer 10-2 may be directly bonded together without using a bonding layer. In this case, for example, at least one of the surface 13 of the first wafer 10-1 and the surface 13 of the second wafer 10-2 may be subjected to plasma treatment to activate them, and then temporarily bonded together, and then annealed to increase the bonding strength. In the plasma treatment, in a vacuum chamber, high-frequency power is supplied while a process gas such as argon (Ar), nitrogen (N2), or oxygen (O2) is being supplied, to supply a plasma-like gas to the surface to be treated with the plasma treatment.

[0027] The annealing method may be, for example, a single-wafer RTA in which the wafers are rapidly heated one by one in a chamber, or a batch method in which a plurality of bonded wafers 20 placed in a quartz furnace tube are heated from the outside by a heater and simultaneously heat-treated, or may be a method of heating with a hot plate without being limited to infrared heating. Note that the annealing may be performed after the modified layer forming step 102 or the detection step 103, as long as it is performed before the grinding step 105 described later is performed.

[0028] In the embodiment, the front surface 13 side of the first wafer 10-1 and the front surface 13 side of the second wafer 10-2 are bonded together, but if the second wafer 10-2 is a substrate wafer, either side of the second wafer 10-2 may be bonded together.

[0029] (Modified layer forming step 102) Fig. 5 is a side view, partially in cross section, showing one state of the modified layer forming step 102 shown in Fig. 3. Figs. 6 and 7 are enlarged cross-sectional views showing a part of the bonded wafer 20 after the modified layer forming step 102 shown in Fig. 3. The modified layer forming step 102 is a step of forming an annular modified layer 21 and cracks 22 extending from the modified layer 21 along a position a predetermined distance inside the outer circumferential edge 12 of the first wafer 10-1.

[0030] In the modified layer forming step 102, a modified layer 21 and cracks 22 are formed inside the first wafer 10-1 by stealth dicing using a laser processing device 40. The laser processing device 40 includes a holding table 41 and a laser beam irradiation unit 42. The holding table 41 holds the wafer 10 on a holding surface and is rotatable around a vertical axis. The laser beam irradiation unit 42 irradiates a laser beam 43 onto the wafer 10 (first wafer 10-1) held on the holding table 41. The laser processing device 40 further includes a moving unit (not shown) that moves the holding table 41 and the laser beam irradiation unit 42 relatively, an imaging unit (not shown) that images the wafer 10 held on the holding table 41, and the like.

[0031] In the modified layer forming step 102, a laser beam 43 is irradiated from the back surface 14 side of the first wafer 10-1 along a position a predetermined distance inside the outer circumferential edge 12 of the first wafer 10-1, thereby forming an annular modified layer 21 inside the first wafer 10-1. Specifically, the position a predetermined distance inside the outer circumferential edge 12 is the boundary between the central region 15 and the outer circumferential region 16. The laser beam 43 is a laser beam with a wavelength that passes through the first wafer 10-1, for example, infrared rays (IR).

[0032] The modified layer 21 refers to a region in which the density, refractive index, mechanical strength or other physical properties are different from those of the surrounding area as a result of irradiation with the laser beam 43. The modified layer 21 is, for example, a melting process region, a crack region, a dielectric breakdown region, a refractive index change region, a region in which these regions are mixed, etc. The modified layer 21 has a lower mechanical strength, etc. than other parts of the first wafer 10-1.

[0033] In the modified layer forming step 102, first, the back surface 14 of the second wafer 10-2 is sucked and held on the holding surface (upper surface) of the holding table 41. Next, the first wafer 10-1 and the condenser of the laser beam irradiation unit 42 are aligned. Specifically, the holding table 41 is moved to an irradiation area below the laser beam irradiation unit 42 by a moving unit (not shown). Next, the first wafer 10-1 is photographed and aligned by an imaging unit (not shown), so that the irradiation part of the laser beam irradiation unit 42 is vertically opposed to a position a predetermined distance inside the outer circumferential edge 12 of the first wafer 10-1, and then the focusing point 44 of the laser beam 43 is set inside the first wafer 10-1.

[0034] In the modified layer forming step 102, next, while rotating the holding table 41 about a vertical axis, a pulsed laser beam 43 is emitted from a laser beam irradiation unit 42 to the back surface 14 of the first wafer 10-1. That is, the laser beam 43 is annularly irradiated along a position a predetermined distance inside the outer circumferential edge 12 of the first wafer 10-1.

[0035] As a result, an annular modified layer 21 is formed on the first wafer 10-1 along a position a predetermined distance inside the outer circumferential edge 12, and cracks 22 extend from the modified layer 21. As shown in Fig. 6, in the modified layer forming step 102, it is preferable to form the modified layer 21 by irradiating the laser beam 43 so that the cracks 22 extending from the modified layer 21 are exposed on the front surface 13 (the bonding surface with the second wafer 10-2) side of the first wafer 10-1. Note that, as shown in Fig. 7, the cracks 22 may be exposed not only on the front surface 13 side of the first wafer 10-1 but also on the back surface 14 side.

[0036] In the modified layer forming step 102, the height of the focal point 44 of the laser beam 43 may be changed and the laser beam 43 may be irradiated multiple times, or a laser beam 43 having multiple focal points 44 spaced apart in the thickness direction of the first wafer 10-1 may be irradiated to form multiple modified layers 21 along the direction perpendicular to the surface 13 of the first wafer 10-1. A laser beam 43 branched in the traveling direction of the laser beam 43 may be used, a laser beam 43 branched in a direction perpendicular to the traveling direction may be used, or an elliptical laser beam 43 having a major axis in the traveling direction and a minor axis in a direction perpendicular to the traveling direction may be used.

[0037] When the laser beam 43 is irradiated multiple times from the back surface 14 side of the first wafer 10-1, the modified layer 21 is formed in sequence from the front surface 13 side toward the back surface 14 side. Moreover, "perpendicular to the front surface 13 of the first wafer 10-1" means that the inclination of an approximation plane obtained by approximating the entire extended crack 22 to a plane relative to the vertical plane is within ±5 degrees, preferably within ±2 degrees.

[0038] 6 and 7, the first wafer 10-1 is warped in a convex shape on the front surface 13 side in the outer peripheral region 16 on the outer periphery 12 side of the modified layer 21 and the cracks 22 due to the formation of the modified layer 21 and the cracks 22. When the modified layer 21 and the cracks 22 are formed in an annular shape along the entire circumference of the first wafer 10-1, the modified layer forming step 102 is completed.

[0039] In the present invention, in order to promote warping of the outer peripheral region 16, in the modified layer forming step 102, in addition to the modified layer 21 and the cracks 22, an auxiliary modified layer and auxiliary cracks extending from the auxiliary modified layer may be formed in the outer peripheral region 16. The auxiliary modified layer may be formed, for example, in one or more rings concentric with the modified layer 21, or in a plurality of straight lines (stripes) along one direction parallel to the surface 13, or in a plurality of straight lines (grids) along two directions parallel to the surface 13.

[0040] (Detection step 103) Fig. 8 is a schematic diagram showing an example of the detection step 103 shown in Fig. 3. The detection step 103 is performed after the modified layer forming step 102. The detection step 103 is a step for detecting the amount of warpage in the outer circumferential region 16 of the first wafer 10-1.

[0041] In the detection step 103 of the embodiment, the amount of warpage in the outer circumferential region 16 of the first wafer 10-1 is detected by a warpage detection unit 31 of a processing device 30 shown in Fig. 8. The processing device 30 includes the warpage detection unit 31 and a control unit 32. The warpage detection unit 31 detects the amount of warpage in the outer circumferential region 16 and outputs the detection result to the control unit 32. The control unit 32 includes an arithmetic processing device, a storage device, and an input / output interface, and executes various types of arithmetic processing based on programs stored in the storage device.

[0042] The warpage detection unit 31 of the embodiment includes a height measuring device that detects the amount of warpage in the outer circumferential region 16 by measuring the height of the outer circumferential region 16. The height measuring device may be of either a contact type or a non-contact type, and includes a laser length measuring device, a line scanner, a three-dimensional scanner, etc. The height measuring device measures the height of a predetermined measurement point on the back surface 14 in the outer circumferential region 16 of the first wafer 10-1 in the bonded wafer 20 held in a horizontal position.

[0043] By using a height measuring device to obtain measurement values ​​at multiple measurement points along the radial direction of the first wafer 10-1, such as the central region 15, the position where the modified layer 21 is formed, and the outer peripheral region 16, the amount of warpage, which is the relative height at each measurement point based on the height in the central region 15, can be detected.

[0044] In the present invention, the height of the outer peripheral region 16 may be measured using an IR camera instead of a height measuring device. The IR camera irradiates the outer peripheral region 16 with light and captures an image of the bonded wafer 20 within a planar field of view. Interference fringes are formed by interference between the light reflected from the front surface 13 side of the first wafer 10-1 and the light reflected from the front surface 13 side of the second wafer 10-2. The IR camera identifies the height of each region based on the brightness and darkness of the interference fringes on the captured image and their position information. This makes it possible to detect the amount of warpage, which is the relative height of each region based on the height of the central region 15.

[0045] In the present invention, instead of the height measuring device, an interferometer may be used to detect the amount of warpage in the outer peripheral region 16. The interferometer includes a white light interferometer, etc. The interferometer irradiates light such as IR illumination light or laser light onto the gap in the outer peripheral region 16 between the first wafer 10-1 and the second wafer 10-2, which is formed by the warpage of the first wafer 10-1, from the radial outside of the bonded wafer 20, and receives the reflected light. The interferometer obtains interference fringes formed by converging (recombining) the reflected light from the measurement surface (outer peripheral region 16) and the reflected light from the reference surface (mirror of the interferometer), and the amount of warpage, which is the size of the gap, can be detected based on the number of interference fringes.

[0046] 5 that performs the modified layer forming step 102. In this case, the warpage detection unit 31 is provided so as to be movable relative to the holding table 41. The control unit 32 may be included in a control device of the laser processing apparatus 40.

[0047] Fig. 9 is a diagram showing an example of the measurement result of the amount of warpage in the detection step 103 shown in Fig. 3. Fig. 9 is a graph showing the relationship between the distance [μm] radially outward from the position where the modified layer 21 is formed and the amount of warpage [μm] at positions 0 degrees, 22.5 degrees, and 45 degrees from a predetermined position in the circumferential direction of the first wafer 10-1.

[0048] In the example shown in Fig. 9, it can be seen that at all measurement positions, the amount of warpage reaches 0.5 µm at a position approximately 200 µm from the position where the modified layer 21 is formed. Note that, in the example shown in Fig. 9, the amount of warpage is detected at a position up to 800 µm from the position where the modified layer 21 is formed, but in the detection step 103 of the present invention, only a narrow region, such as within ±100 µm inside and outside the position where the modified layer 21 is formed, may be detected.

[0049] (Decision step 104) The judgment step 104 is a step for judging whether or not the bonding between the first wafer 10-1 and the second wafer 10-2 in the outer circumferential region 16 has been released based on the amount of warpage in the outer circumferential region 16 of the first wafer 10-1 detected in the detection step 103, and for deciding whether or not to perform the grinding step 105.

[0050] The determination step 104 in the embodiment is performed by the control unit 32 of the processing device 30 shown in Fig. 8. In the determination step 104, for example, if the amount of warpage is less than a predetermined value at a position radially outwardly a predetermined distance from the position where the modified layer 21 is formed, it is determined that the bonding between the first wafer 10-1 and the second wafer 10-2 is not released, and it is decided not to perform the grinding step 105.

[0051] For example, in the embodiment, if the amount of warpage at a position 250 μm radially outward from the position where the modified layer 21 is formed is less than 0.5 μm, it is determined that the bonding between the first wafer 10-1 and the second wafer 10-2 is not released. In the detection step 103, if the amount of warpage of the outer peripheral region 16 is detected at multiple points in the circumferential direction of the first wafer 10-1, for example, the average value, the median value, the lower limit value, etc. may be used as the measured value of the amount of warpage. For example, in the example shown in FIG. 9, since the amount of warpage at a position 250 μm radially outward from the position where the modified layer 21 is formed is 0.5 μm or more, it is determined that the bonding between the first wafer 10-1 and the second wafer 10-2 is released.

[0052] In the processing method of the wafer 10 of the embodiment, if it is determined in the judgment step 104 that the amount of warpage in the outer peripheral region 16 is equal to or greater than a predetermined value (judgment step 104; Yes), the grinding step 105 is performed. Also, in the processing method of the wafer 10 of the embodiment, if it is determined in the judgment step 104 that the amount of warpage in the outer peripheral region 16 is less than a predetermined value (judgment step 104; No), the modified layer forming step 102 is performed.

[0053] In the processing method of the wafer 10 according to the embodiment, the modified layer forming step 102, the detection step 103, and the judgment step 104 are repeatedly performed until the amount of warpage in the outer peripheral region 16 is determined to be equal to or greater than a predetermined value in the judgment step 104 (judgment step 104; Yes). In the present invention, for example, after the modified layer forming step 102 is performed again, it may be considered that the bonding between the first wafer 10-1 and the second wafer 10-2 in the outer peripheral region 16 has been released, and the grinding step 105 may be performed.

[0054] For example, in the first modified layer forming step 102, the modified layer 21 may be formed so that the cracks 22 are exposed on the front surface 13 side of the first wafer 10-1 as shown in Fig. 6, and in the modified layer forming step 102 performed a second time, the modified layer 21 may be formed so that the cracks 22 are exposed on the back surface 14 side of the first wafer 10-1 as shown in Fig. 7. Furthermore, in the modified layer forming step 102 performed a third time, the above-mentioned auxiliary modified layer and auxiliary cracks may be formed in the outer circumferential region 16.

[0055] (Grinding step 105) 3. The grinding step 105 is performed based on the result of the determination in the determination step 104. The grinding step 105 of the embodiment is performed when it is determined in the determination step 104 that the amount of warpage in the outer circumferential region 16 of the first wafer 10-1 is equal to or greater than a predetermined value. The grinding step 105 is a step in which the first wafer 10-1 of the bonded wafer 20 is ground from the back surface 14 side to be thinned to a finishing thickness 19.

[0056] In the grinding step 105 of the embodiment, the back surface 14 (the surface opposite to the bonding surface with the second wafer 10-2) of the first wafer 10-1 is ground by a grinding device 50 to thin the first wafer 10-1 to a predetermined finish thickness 19. The grinding device 50 includes a holding table 51, a spindle 52 which is a rotating shaft member, a grinding wheel 53 attached to the lower end of the spindle 52, a grinding stone 54 attached to the lower surface of the grinding wheel 53, and a grinding fluid supply unit (not shown). The grinding wheel 53 rotates on an axis parallel to the axis of the holding table 51.

[0057] In the grinding step 105, first, the back surface 14 side of the second wafer 10-2 is suction-held on the holding surface of the holding table 51. Next, while the holding table 51 is rotated about its axis, the grinding wheel 53 is rotated about its axis. Grinding fluid is supplied to the processing point by a grinding fluid supply unit (not shown), and the grinding wheel 54 of the grinding wheel 53 is brought closer to the holding table 51 at a predetermined feed speed, whereby the back surface 14 of the first wafer 10-1 is ground by the grinding wheel 54 to be thinned down to a predetermined finishing thickness 19.

[0058] At this time, the grinding wheel 54 applies an external force to press the grinding surface of the first wafer 10-1, and the end material of the outer peripheral region 16 of the first wafer 10-1 is removed starting from the modified layer 21, with the modified layer 21 and the crack 22 serving as the interface.

[0059] [Modifications] A processing method for a wafer 10 according to a modified example of the present invention will be described with reference to the drawings. Fig. 11 is a flow chart showing the flow of the processing method for a wafer 10 according to the modified example. As shown in Fig. 11, the processing method for a wafer 10 according to the modified example includes a bonded wafer forming step 201, a pre-detection step 202, a modified layer forming step 203, a detection step 204, a comparison step 205, a judgment step 206, and a grinding step 207.

[0060] In addition, the bonded wafer forming step 201, the modified layer forming step 203, and the grinding step 207 in the modified example are similar to the bonded wafer forming step 101, the modified layer forming step 102, and the grinding step 105 in the embodiment, so their explanations are omitted.

[0061] (Pre-detection step 202) The pre-detection step 202 is performed before performing the modified layer formation step 203. The pre-detection step 202 is a step for detecting the amount of warpage in the outer circumferential region 16 of the first wafer 10-1 in advance. The pre-detection step 202 is performed in the same manner with the same equipment and conditions as the detection steps 103 and 204. The measured value of the amount of warpage in the outer circumferential region 16 detected in the pre-detection step 202 is output to the control unit 32 and stored in a storage device of the control unit 32.

[0062] (Comparison step 205 and decision step 206) The comparison step 205 is a step of comparing the amount of warpage in the outer circumferential region 16 of the first wafer 10-1 detected in the pre-detection step 202 with the amount of warpage in the outer circumferential region 16 of the first wafer 10-1 detected in the detection step 204. Then, in the judgment step 206 of the modified example, it is judged based on the comparison result in the comparison step 205 whether or not the bonding between the first wafer 10-1 and the second wafer 10-2 in the outer circumferential region 16 has been released, and it is determined whether or not to perform the grinding step 207.

[0063] In the embodiment, the outer circumferential region 16 of the first wafer 10-1 is not curved before the modified layer forming step 102 is performed, and the height of the outer circumferential region 16 before the modified layer forming step 102 is performed is considered to be the same as the height of the central region 15 detected in the detection step 103. In contrast, in the modified example, the actual measurement value detected in the pre-detection step 202 is used as the reference value.

[0064] As described above, the processing method and processing device 30 for the wafer 10 according to the embodiment and the modified example form the annular modified layer 21 along the outer peripheral edge 12 of the first wafer 10-1, and then check whether the bonding between the first wafer 10-1 and the second wafer 10-2 has been released in the outer peripheral region 16 on the outer peripheral edge 12 side of the modified layer 21. This makes it possible to detect processing defects and perform additional processing before performing the subsequent grinding steps 105 and 207, thereby preventing edge materials from remaining without peeling during grinding, and preventing processing defects such as cracking of the wafer 10 and damage to the device 18 from occurring, thereby improving the yield.

[0065] It should be noted that the present invention is not limited to the above-described embodiment and modifications, and can be practiced in various forms without departing from the spirit of the present invention.

[0066] For example, in the pre-detection step 202 and the detection steps 103 and 204, height measurement may be performed not only on the outer peripheral region 16 of the first wafer 10-1 but also on the entire surface. This makes it possible to reduce noise such as debris attached to the back surface 14 of the first wafer 10-1 and unevenness of the holding table 41 (see FIG. 5) from the difference in height before and after the modified layer formation step 203.

[0067] Furthermore, the outer circumferential region 16 may be removed in advance by applying an external force before performing the grinding step 105. Specifically, for example, a method of pressing the outer circumferential region 16 from above to apply an external force in the shear direction, a method of lifting the outer circumferential region 16 to apply an external force in the shear direction, or a method of crushing the outer circumferential region 16 with a roller may be used. Furthermore, the external force is not limited to a mechanical external force, and may be ultrasonic vibration or an external force in the radial direction caused by attaching an expandable tape to the back surface 14 of the first wafer 10-1 and expanding the expandable tape.

[0068] In the present invention, the first wafer 10-1 may be a simple substrate wafer on which the devices 18 are not formed. That is, the present invention is also applicable to a case where the modified layer 21 is formed on a wafer 10 that does not have a device layer. In this case, the second wafer 10-2 is limited to a wafer on which the devices 18 are formed. [Explanation of symbols]

[0069] 10 wafers 10-1 First wafer 10-2 Second wafer 11 Substrate 12 Outer rim 13 Surface 14 Back side 15 Central area 16 Outer area 17 Division line 18 Devices 19 Finished thickness 20 Bonded wafer 21 Modification layer 22 Crack 30 Processing equipment 31 Warpage detection unit 32 Control Unit 43 Laser Beam 44 Focus point

Claims

1. A wafer processing method comprising the steps of: a bonded wafer forming step of bonding a front surface side of a first wafer having a chamfered outer periphery to a second wafer to form a bonded wafer; a modified layer forming step of annularly irradiating a laser beam having a wavelength that transmits through the first wafer along a position a predetermined distance inside the outer periphery to form an annular modified layer inside the first wafer and a crack extending from the modified layer to the bonding surface side with the second wafer, thereby causing warping in an outer periphery region on the outer periphery side due to the modified layer and the crack; a detection step of detecting an amount of warpage of the outer circumferential region of the first wafer after the modified layer forming step is performed; a grinding step of grinding the first wafer of the bonded wafer from a surface side opposite to a bonding surface with the second wafer to thin the first wafer to a finish thickness; Equipped with The method further includes a determination step of determining whether or not the bonding between the first wafer and the second wafer in the outer circumferential region is released based on the amount of warpage in the outer circumferential region detected in the detection step, and determining whether or not to perform the grinding step. A wafer processing method comprising the steps of:

2. In the determination step, When it is determined that the amount of warpage in the outer peripheral region is equal to or greater than a predetermined value, the grinding step is carried out; When it is determined that the amount of warpage in the outer peripheral region is less than a predetermined value, the modified layer forming step is carried out again.

2. The wafer processing method according to claim 1 .

3. a pre-detection step of detecting the amount of warpage of the outer peripheral region before the modified layer forming step is performed; a comparison step of comparing the amount of warpage detected in the pre-detection step with the amount of warpage detected in the detection step; Further comprising: In the determining step, it is determined whether or not the bonding between the first wafer and the second wafer in the outer circumferential region is released based on the comparison result in the comparing step, and it is determined whether or not to perform the grinding step.

3. The wafer processing method according to claim 1 or 2.

4. In the detection step, a height of the outer peripheral region is measured, and an amount of warping of the outer peripheral region is detected based on the measured value of the height of the outer peripheral region.

3. The wafer processing method according to claim 1 or 2.

5. In the detection step, light is irradiated onto the outer peripheral region, interference fringes are obtained, and the amount of warping of the outer peripheral region is detected based on the interference fringes generated in the outer peripheral region.

3. The wafer processing method according to claim 1 or 2.

6. 2. The wafer processing method according to claim 1, further comprising a processing device for performing at least the detection step, a warpage detection unit for detecting the amount of warpage in an outer peripheral region of the first wafer; a control unit that judges whether or not the bonding between the first wafer and the second wafer has been released based on the amount of warpage detected by the warpage detection unit and determines whether or not to perform the grinding step; Equipped A processing device comprising:

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