Wafer bonding method

Abstract

To provide a wafer bonding method that can accurately position and bond two wafers together.SOLUTION: A wafer bonding method for bonding a first wafer W1 and a second wafer W2 having a plurality of devices D formed on their surfaces includes a mark forming step for the first wafer W1 of forming a first mark M1 and a second mark M2 at a location on the first wafer W1 that is a predetermined distance away from a specified device D, a mark forming step for the second wafer W2 of forming a third mark M3 and a fourth mark M4 at a location on the second wafer W2 that is a predetermined distance away from the specified device D, and a bonding step of bringing the surfaces of the first wafer W1 and the second wafer W2 face to face and bonding the first wafer W1 and the second wafer W2 together in a state in which the first mark M1 and the third mark M3, and the second mark M2 and the fourth mark M4 in the imaging area of the camera 61 are aligned, respectively, using light of a wavelength that is transparent to the wafers.SELECTED DRAWING: Figure 16

Description

[Technical field]

[0001] The present invention relates to a wafer bonding method for aligning and bonding two wafers, each having a plurality of devices formed on its surface. [Background technology]

[0002] For example, in the manufacturing process of semiconductor chips used in electronic devices such as mobile phones and personal computers, the surface of a disk-shaped semiconductor wafer (hereinafter simply referred to as a "wafer") is divided into a number of device regions by streets (planned division lines) arranged in a grid pattern, and devices such as ICs and LSIs are formed in each device region. Then, a number of semiconductor chips are manufactured by dividing the wafer on which a number of devices are thus formed along the streets.

[0003] In response to recent demands for smaller, thinner electronic devices and larger capacities, multiple wafers are bonded together to form a bonded wafer, but in manufacturing this bonded wafer, it is necessary to stack and bond multiple wafers together so that multiple devices formed on the wafers match each other. For this reason, bonding marks (alignment marks) are formed on each wafer, and the positions of each bonding mark (positions on the XY coordinate system) are optically read, and the wafers are bonded together by aligning the two alignment marks so that they match each other (see, for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2012-134233 A [Patent Document 2] JP 2015-188042 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, there is a problem that the bonding marks cannot be perfectly aligned due to movement errors of the holding tables that hold each wafer, resulting in positional misalignment of the bonded wafers, and that the devices formed on each wafer cannot be perfectly aligned. In addition, since the marks are manufactured at the same time as the devices are formed, there is a problem that the marks cannot be recognized depending on the device used to bond the wafers.

[0006] The present invention has been made in view of the above problems, and an object of the present invention is to provide a wafer bonding method capable of accurately positioning and bonding two wafers. [Means for solving the problem]

[0007] In order to achieve the above-mentioned object, the present invention provides a wafer bonding method for bonding a first wafer and a second wafer, each having devices formed in a plurality of regions on the surface divided by grid-like streets, comprising: a first wafer mark forming step of forming at least two first marks and two second marks at locations on the first wafer that are a predetermined distance away from a specified device; a second wafer mark forming step of forming at least two third marks and two fourth marks at locations on the second wafer that are a predetermined distance away from the specified device; and a bonding step of bringing the front surface of the first wafer into contact with the front surface or the back surface of the second wafer, and bonding the first wafer and the second wafer together in a state in which the first mark and the third mark, and the second mark and the fourth mark, respectively, in an imaging area of ​​a camera are aligned by using light of a wavelength that is transparent to the wafer. Effect of the Invention

[0008] According to the present invention, in the mark forming process, the positional misalignment between the first mark formed on the first wafer and the third mark formed on the second wafer, and between the second mark formed on the first wafer and the fourth mark formed on the second wafer, is visually confirmed by a camera, and the relative positions of the first and second wafers are fine-tuned so that the positional misalignment is zero (so that the first mark and the third mark, and the second mark and the fourth mark are perfectly aligned), and then the first and second wafers are bonded together. This results in a high-quality bonded wafer in which the devices formed on each surface of the first and second wafers are perfectly aligned. [Brief description of the drawings]

[0009] [Figure 1] FIG. 2 is a perspective view of a laser processing device used in the mark forming step of the method of the present invention. [Diagram 2] FIG. 2 is a plan view of a wafer on which a mark is formed in a mark forming step according to a first embodiment of the method of the present invention. [Diagram 3] 3 is a cross-sectional view taken along line AA in FIG. 2. [Figure 4] FIG. 4 is an enlarged detailed view of part B in FIG. [Diagram 5] FIG. 11 is an enlarged partial plan view of a wafer on which marks are formed in a mark forming step according to a second embodiment of the method of the present invention. [Figure 6] 6 is a cross-sectional view taken along line CC in FIG. 5. [Figure 7] FIG. 13 is a plan view of a wafer on which marks are formed in a mark forming step according to a third embodiment of the method of the present invention. [Figure 8] FIG. 8 is an enlarged detailed view of part D in FIG. [Figure 9] 9 is a cross-sectional view taken along line EE in FIG. 8. [Figure 10] 13 is an enlarged partial plan view of a wafer on which marks are formed in mark forming steps according to fourth and fifth embodiments of the method of the present invention. FIG. [Figure 11] 11 is a cross-sectional view taken along the line FF in FIG. 10. [Figure 12]FIG. 13 is a plan view of a wafer on which marks are formed in the mark forming steps according to sixth and seventh embodiments of the method of the present invention. [Figure 13] 13 is a cross-sectional view taken along line GG in FIG. 12. [Figure 14] FIG. 13 is an enlarged detailed view of part H in FIG. [Figure 15] 15 is a cross-sectional view taken along line JJ in FIG. 14. [Figure 16] FIG. 2 is a vertical cross-sectional view showing a bonding step according to the first embodiment of the method of the present invention. [Figure 17] FIG. 2 is a vertical cross-sectional view of a bonded wafer bonded by a bonding step according to a first embodiment of the method of the present invention. [Figure 18] FIG. 4 is a vertical cross-sectional view showing a bonding step according to a second embodiment of the method of the present invention. [Figure 19] FIG. 4 is a vertical cross-sectional view of a bonded wafer bonded by a bonding step according to a second embodiment of the method of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0011] The wafer bonding method according to the present invention comprises the steps of: Mark formation process Lamination process This is a method of stacking and bonding a thin, disk-shaped first wafer W1 and a second wafer W2 as shown in Fig. 2 through the above two steps. Here, the first wafer W1 and the second wafer W2 have the same configuration, and are made of a single crystal silicon base material, and as shown in Fig. 2 and Fig. 3, a plurality of mutually orthogonal streets (planned division lines) L1, L2 are formed in a lattice pattern on the surface (upper surface in Fig. 2 and Fig. 3), and devices D such as ICs and LSIs are mounted in each of a plurality of device regions partitioned by these planned division lines L1, L2.

[0012] The mark forming step in the method of the present invention will be described below, in which alignment marks M1, M2 and M3, M4 are formed on the surfaces of the first wafer W1 and the second wafer W2 by, for example, a laser processing device 1 shown in Fig. 1. The configuration of this laser processing device 1 will be described below with reference to Fig. 1.

[0013] [Laser processing equipment] FIG. 1 is a perspective view of a laser processing device 1, and in the following description, the directions of the arrows shown in FIG. 1 are the X-axis direction (front-back direction), the Y-axis direction (left-right direction), and the Z-axis direction (up-down direction), respectively.

[0014] The laser processing apparatus 1 shown in FIG. 1 has as its main components a holding table 10 that holds a first wafer W1 (second wafer W2) and a laser beam oscillator 20 that emits a laser beam toward the first wafer W1 (second wafer W2).

[0015] Here, the holding table 10 is a disk-shaped member, and is rotatably supported by a rectangular plate-shaped slider 31 described below. The holding table 10 can be rotated around a vertical central axis by a rotation mechanism (not shown). Clampers 11 for fixing the first wafer W1 (second wafer W2) at four circumferential positions on the holding table 10 are disposed at equal angular pitches (90° pitches) in the circumferential direction.

[0016] The holding table 10 can be moved in the X-axis direction by the X-axis moving mechanism 30, and can be moved in the Y-axis direction by the Y-axis moving mechanism 40. Here, the X-axis moving mechanism 30 is composed of guide rails 32 laid parallel to each other along the X-axis direction on a rectangular plate-shaped slider 44, a rotatable ball screw 33 extending along the X-axis direction between these guide rails 32, and a servo motor 34 connected to one axial end of the ball screw 33, and the slider 31 that rotatably supports the holding table 10 is supported so as to be movable in the X-axis direction along the pair of guide rails 32. A nut member (not shown) is provided on the lower surface of the slider 31 so as to protrude downward, and the ball screw 33 is screwed into and inserted into the nut member. A linear scale 35 is provided on the slider 44 along the X-axis direction.

[0017] Therefore, when the servo motor 34 is started to rotate the ball screw 33 forward or backward, the slider 31 having a protruding nut member (not shown) that screws into the ball screw 33 and the holding table 10 supported thereby move along the X-axis direction, and the feed amount of the holding table 10 in the X-axis direction is measured by the linear scale 35.

[0018] The Y-axis moving mechanism 40 is composed of a pair of guide rails 41 laid parallel to each other along the Y-axis direction on the base 100, a rotatable ball screw 42 extending along the Y-axis direction between the guide rails 41, and a servo motor 43 connected to one axial end of the ball screw 42. A slider 44, which supports the slider 31 and the holding table 10 supported thereon so as to be movable along the Y-axis direction, is supported so as to be movable in the Y-axis direction along the pair of guide rails 41. A nut member (not shown) protrudes downward from the lower surface of the slider 44, and the ball screw 42 is screwed into and inserted into the nut member. A linear scale 45 for measuring the feed amount of the holding table 10 in the Y-axis direction is arranged on the base 100 along the Y direction.

[0019] Therefore, when servo motor 43 is started to rotate ball screw 42 forward and backward, slider 44 having a protruding nut member (not shown) that screws onto ball screw 42, slider 31 supported by slider 44 via X-axis movement mechanism 30, and holding table 10 supported by slider 44 move along the Y-axis direction, and the feed amount of holding table 10 in the Y-axis direction is measured by linear scale 45. Therefore, X-axis movement mechanism 30 and Y-axis movement mechanism 40 allow holding table 10 to move in the X-axis and Y-axis directions.

[0020] Furthermore, the laser beam oscillator 20 irradiates a laser beam toward the first wafer W1 (second wafer W2) held on the holding table 10, and is attached horizontally to the upper end of a column 101 that is vertically erected on a base 100. Attached to the tip of this laser beam oscillator 20 are a laser head 21 that collects a laser beam emitted from a laser light source (not shown) and irradiates the laser beam toward the first wafer W1 (second wafer W2) held on the holding table 10, and an imaging means 22 that detects the processing area of ​​the first wafer W1 (second wafer W2) on the holding table 10.

[0021] Here, the imaging means 22 includes, in addition to an ordinary imaging element such as a CCD that captures images using visible light, an infrared irradiation means that irradiates infrared rays toward the first wafer W1 (second wafer W2), an optical system that captures the infrared rays irradiated onto the first wafer W1 (second wafer W2) by the infrared irradiation means, and an infrared CCD that outputs an electrical signal corresponding to the infrared rays captured by this optical system.

[0022] [Wafer bonding method] Next, an embodiment of 1) the mark forming step in the method for bonding the first wafer W1 and the second wafer W2 according to the present invention will be described.

[0023] 1) Mark formation process: <First embodiment> (One modified layer is used as a mark) In the mark forming step according to the first embodiment, modified layers g (see FIG. 4) for alignment are formed inside two outer periphery portions on the front side of the first wafer W1 (second wafer W2) by modified layer forming processing using the laser processing device 1 shown in FIG. 1, and these modified layers g are designated as the first mark M1 and the second mark M2 for the first wafer W1, and the third mark M3 and the fourth mark M4 for the second wafer W2 (see FIGS. 2 and 3). Here, the locations where the modified layers g are formed on the first wafer W (second wafer W2) are two locations facing each other at a predetermined distance r in the radial direction from a specified device D, for example, the central device D shown with diagonal lines in FIG. 2.

[0024] When the first mark M1 and the second mark M2 (the third mark M3 and the fourth mark M4) are formed on the first wafer W1 (the second wafer W2) by the modified layer forming process, the first wafer W1 (the second wafer W2) is placed on the holding table 10 of the laser processing device 1 shown in Fig. 1 and fixed by four clampers 11. When the first wafer W1 (the second wafer W2) is fixed on the holding table 10 in this manner, the surface of the first wafer W1 (the second wafer W2) is imaged by the imaging means 22, and the position of the first wafer W1 (the second wafer W2) in the XY axis direction is adjusted by the X-axis moving mechanism 30 and the Y-axis moving mechanism 40, respectively, so that the location where the first mark M1 (the third mark M3) of the first wafer W1 (the second wafer W2) is to be formed is located directly under the laser head 21.

[0025] When the position of the first wafer W1 (second wafer W2) where the first mark M1 (third mark M3) is to be formed is located directly under the laser head 21 by the above position adjustment, a modified layer g (see FIG. 4) is formed inside one part of the outer periphery of the first wafer W1 (second wafer W2) by modified layer forming processing using a laser beam emitted from the laser head 21 of the laser processing device 1 shown in FIG. 1. That is, the laser head 21 irradiates a laser beam having a wavelength that is transparent to the first wafer W1 (second wafer W2) toward the surface of the first wafer W1 (second wafer W2). Then, a modified layer g is formed inside one part of the outer periphery of the first wafer W1 (second wafer W2), and this modified layer g is made the first mark M1 (third mark M3). The modified layer g is a layer whose density, refractive index, mechanical strength, and other physical properties are different from those of the surroundings.

[0026] As described above, a modified layer g is formed at one location on the outer periphery of the first wafer W1 (second wafer W2) and this modified layer g is made into the first mark M1 (third mark M3).Then, the holding table 10 moves in the X-axis direction, and a modified layer g is formed at another location on the first wafer W1 (second wafer W2) by a laser beam irradiated from the laser head 21 toward the first wafer W1 (second wafer W2) in the same manner as above, and this modified layer g is made into the second mark M2 (fourth mark M4) of the first wafer W1 (second wafer W2).

[0027] Second embodiment (modified layer formed in a cross shape) In the second embodiment, similarly to the first embodiment, a laser beam is irradiated from the laser head 21 of the laser processing device 1 shown in Fig. 1 toward two outer periphery portions of the surface of the first wafer W1 (second wafer W2) by the modified layer forming process, and a plurality of modified layers g (nine each in the illustrated example) are formed in a cross shape in a plan view inside the two outer periphery portions of the surface of the first wafer W1 (second wafer W2) as shown in Fig. 5 and Fig. 6, and these modified layers g are the first mark M1 (third mark M3) and the second mark M2 and fourth mark M4 (not shown) of the first wafer W1 (second wafer W2). Note that in the first and second embodiments, the size of the modified layer may be changed by adjusting the output of the laser beam and defocusing it.

[0028] <Third embodiment> (Dotted cross recess by ablation) In the third embodiment, as shown in Figures 7 to 9, a laser beam having an absorbent wavelength is irradiated from the laser head 21 of the laser processing apparatus 1 shown in Figure 1 toward two outer periphery locations on the surface of the first wafer W1 (second wafer W2) to perform recess formation processing, thereby forming a plurality of recesses h (five each in the illustrated example) forming a cross shape in a planar view at two outer periphery locations on the surface of the first wafer W1 (second wafer W2), and these recesses h become the first mark M1 and the second mark M2 (shown in Figure 7) of the first wafer M1, and the third mark M3 and the fourth mark M4 (shown in Figure 7) of the second wafer W2.

[0029] Here, the laser head 21 emits a laser beam having a wavelength that is absorbed by the first wafer W1 (second wafer W2), so that, as shown in Figures 8 and 9, five recesses h that are rectangular in plan view and form a cross shape in plan view are formed in two locations (only one location is shown in Figures 8 and 9) on the outer periphery of the first wafer W1 (second wafer W2).

[0030] <Fourth embodiment> In the fourth embodiment, recess formation processing is performed in the same manner as in the third embodiment. That is, a laser beam having a wavelength absorbed by the first wafer W1 (second wafer W2) is irradiated toward two locations on the outer periphery of the surface of the first wafer W1 (second wafer W2) by the laser head 21 of the laser processing device 1 shown in Fig. 1, so that continuous recesses h (only one of which is shown in Figs. 10 and 11) are formed in a cross shape in a plan view at two locations on the outer periphery of the surface of the first wafer W1 (second wafer W2), as shown in Figs. 10 and 11.

[0031] 10 and 11 show only a cross-shaped recess h in a plan view formed at one location on the outer periphery of the front surface of the first wafer W1 (second wafer W2), and this recess h is defined as the first mark M1 (third mark M3) of the first wafer W1. Note that, although not shown in FIGS. 10 and 11 is a cross-shaped recess h in a plan view formed at another location on the outer periphery of the front surface of the first wafer W1 (second wafer W2), this recess h is defined as the second mark M2 of the first wafer W1 and the fourth mark M4 of the second wafer W2.

[0032] <Fifth embodiment> In the fifth embodiment, recess formation processing is performed in the same manner as in the third and fourth embodiments. That is, a laser beam having a wavelength absorbed by the first wafer W1 (second wafer W2) is irradiated by the laser head 21 of the laser processing device 1 shown in Fig. 1 to form a mark (M1 to M4) by one recess on the surface of the first wafer W1 (second wafer W2). In the third to fifth embodiments, the size of the processing mark may be changed by adjusting the output of the laser beam, defocusing, or LCOS.

[0033] Sixth Embodiment In the sixth embodiment, as shown in Figs. 12 to 15, in the same manner as in the fourth embodiment, two cross-shaped recesses h in plan view are formed at two locations on the outer periphery of the surface of the first wafer W1 (second wafer W2). These recesses h are formed by lowering the cutting blade 15 from above the locations where the marks M1 to M4 are to be formed using a disk-shaped cutting blade 15 rotating in the direction of the arrow in Fig. 13, cutting into the wafers W1 and W2 to form arc-shaped cut grooves in the depth direction (cut groove processing). These recesses h are the first mark M1 and the second mark M2 for the first wafer W1, and the third mark M3 and the fourth mark M4 for the second wafer W2. The cross-shaped recesses h in plan view are formed by moving the holding table 10 and the first wafer W1 (second wafer W2) held thereon in the X-axis direction and the Y-axis direction by the X-axis moving mechanism 30 and the Y-axis moving mechanism 40 in the laser processing apparatus 1 shown in Fig. 1.

[0034] Seventh embodiment In the seventh embodiment, similarly to the sixth embodiment, the marks M1 to M4 are formed by lowering the disk-shaped cutting blade 15 rotating in the direction of the arrow in Fig. 13 from above the places where the marks M1 to M4 are to be formed, thereby forming linear recesses h. Note that in the sixth and seventh embodiments, the size of the recesses h may be changed by changing the depth to which the cutting blade 15 is cut.

[0035] Next, an embodiment of 2) bonding step in the wafer bonding method according to the present invention will be described.

[0036] 2) Lamination process: First Embodiment In the bonding process according to this embodiment, as shown in FIG. 16, the surface of the first wafer W is faced to the surface of the second wafer W2, and the first wafer W1 and the second wafer W2 are bonded together in a state in which the first mark M1 of the first wafer W1 and the third mark M3 of the second wafer W2, and the second mark M2 of the first wafer W1 and the fourth mark M4 of the second wafer W2, which are in the imaging area of ​​the camera 61, are aligned using light of a wavelength that is transparent to the first wafer W1 and the second wafer W2.

[0037] The first wafer W1 is held by the first bonding stage 50 with its back surface (the upper surface on which the device D is not formed in FIG. 16) in close contact with the flat lower surface of the first bonding stage 50. A permanent bonding resin j is applied to the front surface (the lower surface in FIG. 16) of the first wafer W1.

[0038] On the other hand, the second wafer W2 is held by the second bonding stage 60 with its back surface (the lower surface on which the device D is not formed in FIG. 16) in close contact with the flat upper surface of the second bonding stage 60. A permanent bonding resin j is applied to the front surface (the upper surface in FIG. 16) of the second wafer W2. The second bonding stage 60 can be moved in the Z-axis direction (up and down direction) by the lifting mechanism 70, and can be moved in the XY-axis directions (left and right and front and back directions) by the horizontal movement mechanism 80.

[0039] Here, at two locations on the first bonding stage 50 and the second bonding stage 60 (the location where the first mark M1 and the second mark M2 of the first wafer W1 are formed and the location where the third mark M3 and the fourth mark M4 of the second wafer W2 are formed), light-transmitting holes 50a and 60a are formed vertically. Above each light-transmitting hole 50a of the first bonding stage 50, a light source 51 is disposed, which emits infrared light having a wavelength that is transparent to the first wafer W1 and the second wafer W2 toward each transparent hole 50a. Also, below each light-transmitting hole 60a of the second bonding stage 60, a camera 61 is disposed as an imaging means.

[0040] 16, in the bonding process according to the present embodiment, the first wafer W1 and the second wafer W2 are held so that their surfaces (surfaces on which the devices D are formed) face each other at a predetermined distance in the vertical direction, and, for example, infrared light is emitted from two light sources 51 toward the light-transmitting hole 50a of the first bonding stage 50. Then, the infrared light passes through two light-transmitting holes 60a of the first wafer W1 and the second wafer W2 and the second bonding stage 60 and reaches each camera 61, so that the first mark M2 formed on the first wafer M1, the third mark M3 formed on the second wafer W2, the second mark M2 formed on the first wafer W1, and the fourth mark M4 formed on the second wafer W2 are each imaged by the camera 61.

[0041] As described above, when the first mark M1, the third mark M3, the second mark M2, and the fourth mark M4 formed at positions overlapping each other vertically are imaged by the camera 61, the positional deviation on the XY plane between the first mark M1, the third mark M3, the second mark M2, and the fourth mark M4 is detected, and the second bonding stage 60 and the second wafer W2 held thereon are finely adjusted in the XY direction by the positional deviation amount relative to the first wafer W1 by the horizontal movement mechanism 80 so that the positional deviation becomes zero (so that the first mark M1, the third mark M3, and the second mark M2, and the fourth mark M4 completely overlap each other vertically). As a result, the multiple devices D formed on the surfaces of the first wafer W1 and the second wafer W2, respectively, completely coincide with each other in the vertical direction.

[0042] As described above, when the first mark M2 formed on the first wafer W1 and the third mark M3 formed on the second wafer W2, and the second mark M2 formed on the first wafer W1 and the fourth mark M4 formed on the second wafer W2, completely coincide with each other on the XY plane (in a planar view), the second bonding stage 60 and the second wafer W2 held thereon are raised by the lifting mechanism 70, and the surfaces of the second wafer W2 and the first wafer W1 are bonded together by the permanent bonding resin j, thereby obtaining a bonded wafer W in which the first wafer W1 and the second wafer W2 are bonded together, as shown in FIG. 17. In the bonded wafer W formed by bonding the first wafer W1 and the second wafer W2 in this manner, the first wafer W1 and the second wafer W2 are bonded together in a precisely positioned state as described above. Therefore, the devices D mounted on the respective surfaces of the first wafer W1 and the second wafer W2 are bonded in a perfectly aligned state, and a high-quality bonded wafer W as shown in FIG. 17 is obtained.

[0043] <Second embodiment> Next, a second embodiment of the method of the present invention will be described with reference to Figures 18 and 19. In Figures 18 and 19, the same elements as those shown in Figures 16 and 17 are denoted by the same reference numerals, and further description thereof will be omitted below.

[0044] The method according to this embodiment is a method of bonding a first wafer W1 thinned by grinding to a second wafer W2, in which the thin first wafer W1 is supported by a thick support wafer W3 by bonding its front surface (the surface (upper surface) on which the device D is formed) to the lower surface of the thick support wafer W3 with a temporary bonding resin j1. Here, the upper surface of the support wafer W3 is bonded to the lower surface of the first bonding stage 50. Therefore, a first mark M1 and a second mark M2 are formed on two outer periphery portions of the rear surface (lower surface) of the first wafer W1.

[0045] In this embodiment, the first wafer W1 and the second wafer W2 are bonded together in the same manner as in the first embodiment to obtain a bonded wafer W as shown in Fig. 19. That is, in the bonding step according to this embodiment, as shown in Fig. 18, the back surface (lower surface) of the first wafer W1 and the front surface (upper surface) of the second wafer W2 are held to face each other at a predetermined distance in the vertical direction, and infrared light, for example, is emitted from two light sources 51 toward the light-transmitting hole 50a of the first bonding stage 50. Then, the infrared light passes through the support wafer W3, the first wafer W1, the second wafer W2, and each of the light-transmitting holes 60a of the second bonding stage 60 to reach each of the cameras 61, so that the first mark M1 formed on the first wafer W1, the third mark M3 formed on the second wafer W2, the second mark M2 formed on the first wafer W1, and the fourth mark M4 formed on the second wafer W2 are each imaged by the camera 61.

[0046] As described above, when the first mark M1, the third mark M3, the second mark M2, and the fourth mark M4 formed at positions overlapping each other vertically are imaged by the camera 61, the positional deviation on the XY plane between the first mark M1, the third mark M3, the second mark M2, and the fourth mark M4 is detected, and the second bonding stage 60 and the second wafer W2 held thereon are finely adjusted in the XY direction by the positional deviation amount relative to the first wafer W1 by the horizontal movement mechanism 80 so that the positional deviation becomes 0 (so that the first mark M1, the third mark M3, and the second mark M2, and the fourth mark M4 completely overlap each other vertically). As a result, the multiple devices D formed on each surface of the first wafer W1 and the second wafer W2, respectively, completely coincide with each other in the vertical direction via the first wafer W1.

[0047] The marks M1 to M4 formed on the first wafer W1 and the second wafer W2 do not have to have the same shape. For example, the first mark M1 and the second mark M2 may be formed on the first wafer W1 according to the first embodiment, and the third mark M3 and the fourth mark M4 may be formed on the second wafer W2 according to the sixth embodiment.

[0048] Moreover, the first mark M1 and the second mark M2 do not have to have the same shape. That is, in the bonding process, the center of the mark M1 and the center of the mark M2 may be aligned. Furthermore, the marks M1 to M4 formed on the first wafer W1 and the second wafer W2 are not limited to two each. For example, four marks may be formed, two marks spaced apart in the X-axis direction and two marks spaced apart in the Y-axis direction perpendicular to the X-axis direction.

[0049] As described above, when the first mark M1 formed on the first wafer W1 and the third mark M3 formed on the second wafer W2, and the second mark M2 formed on the first wafer W1 and the fourth mark M4 formed on the second wafer W2 completely coincide with each other on the XY plane (in a plan view), the second bonding stage 60 and the second wafer W2 held thereon are raised by the lifting mechanism 70, and the front surface (upper surface) of the second wafer W2 and the back surface (lower surface) of the first wafer W1 are bonded together by the permanent bonding resin j. Thereafter, the support wafer W3 temporarily bonded to the first wafer W1 by the temporary bonding resin j1 is peeled off from the first wafer W1, and a bonded wafer W in which the first wafer W1 and the second wafer W2 are bonded together is obtained, as shown in FIG. In the bonded wafer W formed by bonding the first wafer W1 and the second wafer W2 in this manner, the first wafer W1 and the second wafer W2 are bonded together in a precisely positioned state as described above. Therefore, the devices D formed on the respective surfaces of the first wafer W1 and the second wafer W2 are bonded together in a perfectly aligned state, and a high-quality bonded wafer W as shown in FIG. 19 is obtained.

[0050] It should be noted that the present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims and the technical ideas described in the specification and drawings. [Explanation of symbols]

[0051] 1: laser processing device, 10: holding table, 11: clamper, 15: cutting blade, 20: laser beam oscillator, 21: laser head, 22: imaging means, 30: X-axis movement mechanism, 31: slider, 32: guide rail, 33: ball screw, 34: servo motor, 35: linear scale, 40: Y-axis movement mechanism, 41: guide rail, 42: ball screw, 43: servo motor, 44: slider, 45: Linear scale, 50: First bonding stage, 51: Light source, 60: second bonding stage, 61: camera, 70: lifting mechanism, 80: horizontal movement mechanism, 100: base, 101: column, D: device, g: modified layer, h: recess, j: permanent bonding resin, ji: temporary bonding resin, L1, L2: street M1: 1st mark, M2: 2nd mark, M3: 3rd mark, M4: 4th mark, r: distance from the specified device, W: bonded wafer, W1: first wafer, W2: Second wafer, W3: Support wafer

Claims

1. 1. A wafer bonding method for bonding a first wafer and a second wafer, the first wafer and the second wafer having devices formed in a plurality of regions on the surfaces of the first wafer and the regions being divided by lattice-like streets, the method comprising the steps of: a mark forming step of forming at least two marks, a first mark and a second mark, at a location on the first wafer that is a predetermined distance away from the designated device; a mark forming step of forming at least two third marks and a fourth mark at a location on the second wafer that is a predetermined distance away from the designated device; a bonding process in which a front surface of the first wafer is brought into contact with a front surface or a back surface of the second wafer, and the first wafer is bonded to the second wafer in a state in which the first mark and the third mark, and the second mark and the fourth mark in an imaging area of ​​a camera are aligned with each other by using light having a wavelength that is transparent to the wafer; A wafer bonding method comprising the steps of:

2. 2. The method for bonding wafers according to claim 1, wherein the first mark or the second mark is formed on the back surface of the first wafer.

3. The first mark, the second mark, the third mark, and the fourth mark, A modified layer is formed by irradiating a laser beam having a wavelength that is transparent to the wafer. A recess is formed on the wafer by irradiating the wafer with an absorbent laser beam. Cutting grooves by cutting blades, 2. The method of claim 1, wherein the wafer is bonded by any one of the following methods.

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