Stacked substrate processing method and stacked substrate processing system

Abstract

The present invention relates to a method for processing an overlapping substrate formed by bonding a first substrate and a second substrate, comprising the following steps: forming a peripheral modification layer along the boundary between the peripheral portion of the first substrate to be removed and the central portion of the first substrate; forming an unbonded area in the peripheral portion where the bonding strength between the first substrate and the second substrate is weakened; forming a reference modification layer on the surface of the side of the first substrate not bonded to the second substrate as a reference for determining the formation position of either the peripheral modification layer or the unbonded area; and removing the peripheral portion with the peripheral modification layer as a reference point.

Description

[Technical Field]

[0001] This invention relates to a processing method and a processing system. [Previous Technology]

[0002] Patent Document 1 discloses a substrate processing system comprising a modifier layer forming apparatus for forming a modifier layer inside a first substrate formed by bonding a first substrate and a second substrate, along the boundary between the peripheral and central portions of the first substrate to be removed, and a peripheral removal apparatus for removing the peripheral portion of the first substrate based on the modifier layer. [Prior Art Documents] [Patent Documents]

[0003] [Patent Document 1] International Publication No. 2019 / 176589 [Summary of the Invention]

[0004] [The problem the invention aims to solve]

[0005] According to the technology of the present invention, in an overlapping substrate formed by bonding a first substrate and a second substrate, the laser irradiation section is appropriately positioned relative to the laser irradiation target position of the first substrate. [Means for Solving the Problem]

[0006] One aspect of the present invention is a method for processing an overlapping substrate formed by bonding a first substrate and a second substrate, comprising the following steps: forming a peripheral modification layer along the boundary between the peripheral portion of the first substrate to be removed and the central portion of the first substrate; forming an unbonded area in the peripheral portion where the bonding strength between the first substrate and the second substrate is weakened; forming a reference modification layer on the surface of the first substrate on the side not bonded to the second substrate, serving as a reference for determining the formation position of either the peripheral modification layer or the unbonded area; and removing the peripheral portion using the peripheral modification layer as a base point. [Effects of the Invention]

[0007] Through the present invention, the laser irradiation section can be appropriately positioned relative to the laser irradiation target position in the first substrate in an overlapping substrate formed by bonding the first substrate and the second substrate.

Implementation Method

[0009] In the manufacturing process of semiconductor devices, sometimes the periphery of the first wafer is removed from an overlapping substrate formed by bonding a first substrate (a silicon substrate such as a semiconductor substrate) on the surface of which a plurality of electronic circuits and other components are formed thereon with a second substrate, and so-called edge cutting is performed.

[0010] Edge cutting of the first substrate is performed, for example, using the substrate processing system disclosed in Patent Document 1. That is, a modified layer is formed by irradiating the interior of the first substrate with laser light (first laser light), and the peripheral portion is removed from the first substrate using the modified layer as a base. Furthermore, using the substrate processing system described in Patent Document 1, a modified surface is formed by irradiating the interface where the first substrate and the second substrate are joined with laser light (second laser light), thereby reducing the bonding force between the first substrate and the second substrate in the peripheral portion of the object to be removed, so as to properly remove the peripheral portion.

[0011] However, the first laser light and the second laser light mentioned above are generally selected from different types of laser light. Therefore, in the substrate processing system, sometimes multiple laser modules are configured to independently irradiate the first laser light and the second laser light.

[0012] Typically, the irradiation position of the laser light on the target of the laser light, i.e., the substrate, is determined by a camera identifying the end (edge) of the substrate and adjusted by eccentric control (adjustment). However, as described above, when using multiple laser modules, there is a concern that the irradiation position of the laser light may shift between the laser modules. Furthermore, in this case, the formation position of the modified layer, which serves as the peeling base point, and the formation position of the bonding strength reduction area may shift, resulting in concerns that the peripheral portion of the first substrate may not be properly removed. Therefore, conventional edge cutting techniques still have room for improvement.

[0013] The present invention was made in view of the above circumstances, and its object is to properly position the laser irradiation section relative to the laser irradiation target position of the first substrate in an overlapping substrate formed by bonding the first substrate and the second substrate. Hereinafter, a wafer processing system as a processing system according to the present embodiment and a wafer processing method as a processing method will be described with reference to the drawings. Furthermore, in this specification and drawings, elements having substantially the same functional configuration are marked with the same symbols and repeated descriptions are omitted.

[0014] In the wafer processing system 1 described later according to this embodiment, as shown in FIG1, a superimposed wafer T, which is formed by bonding a first wafer W, which serves as a first substrate, and a second wafer S, which serves as a second substrate, is processed. Hereinafter, in the first wafer W, the side that is bonded to the second wafer S is called surface Wa, and the side opposite to surface Wa is called back surface Wb. Similarly, in the second wafer S, the side that is bonded to the first wafer W is called surface Sa, and the side opposite to surface Sa is called back surface Sb.

[0015] The first wafer W is, for example, a semiconductor wafer such as a silicon substrate, and a device layer Dw containing a plurality of devices is formed on the surface Wa side. Furthermore, a bonding film Fw, serving as a surface film, is formed in the device layer Dw, and the second wafer S is bonded via this bonding film Fw. The bonding film Fw is, for example, an oxide film (THOX film, SiO2 film, TEOS film), a SiC film, a SiCN film, or an adhesive. Furthermore, the peripheral portion We of the first wafer W is chamfered, and the cross-section of the peripheral portion We has a thickness that decreases towards its leading edge. Furthermore, the peripheral portion We is the portion removed during edge cutting, described later, and is, for example, a range of 0.5 mm to 3 mm radially from the outer end of the first wafer W.

[0016] The second wafer S, for example, has the same structure as the first wafer W, with a device layer Ds and a bonding film Fs forming the surface Sa, and the periphery is chamfered. Furthermore, the second wafer S does not need to be a device wafer with the device layer Ds formed; for example, it can be a support wafer supporting the first wafer W. In this case, the second wafer S functions as a protective material protecting the device layer Dw of the first wafer W.

[0017] As shown in FIG2, the wafer processing system 1 has a configuration that connects the loading / unloading station 2 and the processing station 3 into one unit. In the loading / unloading station 2, for example, a cassette C capable of accommodating multiple overlapping wafers T is loaded and unloaded between the station and the outside. The processing station 3 is equipped with various processing devices for performing desired processing on the overlapping wafers T.

[0018] The loading / unloading station 2 is equipped with a cassette loading platform 10 that holds a plurality of cassettes C (e.g., 3). Furthermore, a wafer transport device 20 is provided adjacent to the cassette loading platform 10 on the negative X-axis side. The wafer transport device 20 can move along a transport path 21 extending in the Y-axis direction and transports overlapping wafers T, etc., between the cassettes C of the cassette loading platform 10 and the transfer device 30 described later.

[0019] In the loading and unloading station 2, on the negative X-axis side of the wafer handling device 20, there is a transfer device 30 adjacent to the wafer handling device 20 for transferring overlapping wafers T and the like between the processing station 3.

[0020] For example, the processing station 3 has three processing blocks B1 to B3. The first processing block B1, the second processing block B2, and the third processing block B3 are arranged in this order from the positive X-axis direction side (the side of the transfer station 2) to the negative direction side.

[0021] The first processing block B1 includes an etching device 40 for etching the polished surface of the first wafer W that has been polished in the processing apparatus 80 described later, a cleaning device 41 for cleaning the first wafer W after etching by the etching device 40, and a wafer transport device 50. The etching device 40 and the cleaning device 41 are arranged in a stacked configuration. Furthermore, the number and arrangement of the etching device 40 and the cleaning device 41 are not limited thereto.

[0022] The cleaning apparatus 41 irradiates the first wafer W, after etching by the etching apparatus 40, with cleaning laser light (e.g., UV femtosecond laser) to remove residues (deposits, etc.) remaining on the first wafer W. Furthermore, the cleaning apparatus 41 irradiates the bonding films Fw and Fs (hereinafter referred to as "residual films") remaining on the surface Sa of the second wafer S after the peripheral portion We has been removed, thereby removing the residual films through laser etching. In other words, by removing the bonding films Fw and Fs remaining after the peripheral portion We has been removed, the surface Sa of the second wafer S is exposed, thereby completely removing the peripheral portion We of the first wafer W.

[0023] The wafer transport device 50 is disposed on the negative X-axis side of the transfer device 30. The wafer transport device 50 holds and transports the overlapping wafer T, and for example has two transport arms 51, 51. Each transport arm 51 can move freely in the horizontal direction, the vertical direction, or around the horizontal axis and the vertical axis. Furthermore, the wafer transport device 50 can transport the overlapping wafer T to the transfer device 30, the etching device 40, the cleaning device 41, the interface modification device 60 (described later), the internal modification device 61 (described later), and the separation device 62 (described later), that is, to the devices in the wafer processing system 1 other than the processing device 80 (described later).

[0024] The second processing block B2 includes an interface modification device 60 for forming the unbonded region Ae and the reference modification layer M1 (described later), an internal modification device 61 for forming the peripheral modification layer M2 and the dividing modification layer M3 as the base point for peeling off the first wafer W, a separation device 62 for removing the peripheral portion We of the first wafer W, and a wafer transport device 70. The interface modification device 60, the internal modification device 61, and the separation device 62 are arranged in a stacked configuration. Furthermore, the number and arrangement of the interface modification device 60, the internal modification device 61, and the separation device 62 are not limited thereto. For example, at least any one of the interface modification device 60, the internal modification device 61, and the separation device 62 can be arranged adjacent to each other in the horizontal direction, rather than in a stacked configuration.

[0025] The interface modification apparatus 60, for example, irradiates the element layer Dw and the bonding film Fw formed on the first wafer W with interface laser light L1 (e.g., CO2 laser) to form an unbonded region Ae where the bonding force between the first wafer W and the second wafer S is reduced. Furthermore, the interface modification apparatus 60, for example, irradiates the back surface Wb of the first wafer W with interface laser light L1 to form a reference modification layer M1, which serves as a reference mark for alignment when the peripheral modification layer M2 is formed in the internal modification apparatus 61.

[0026] As shown in Figures 3 and 4, the interface modification apparatus 60 has a chuck 100 that holds the overlapping wafer T on its top surface. The chuck 100 adsorbs and holds the side (back side Sb) of the second wafer S that is not bonded to the first wafer W.

[0027] The suction cup 100 is supported by the sliding table 102 via the air bearing 101. A rotating mechanism 103 is provided on the bottom side of the sliding table 102. The rotating mechanism 103 is driven by, for example, a built-in motor. The suction cup 100 can rotate freely about the θ axis (vertical axis) via the air bearing 101 through the rotating mechanism 103. The sliding table 102 can move along the track 105 extending in the Y-axis direction via the horizontal moving mechanism 104 provided on its bottom side. The track 105 is provided on the base 106. Furthermore, the driving source of the horizontal moving mechanism 104 is not particularly limited, for example, a linear motor can be used.

[0028] A laser irradiation system 110 is provided above the suction cup 100. The laser irradiation system 110 has a laser head 111 and a lens 112. The lens 112 can be freely raised and lowered through a lifting mechanism (not shown).

[0029] The laser head 111 has a laser oscillator (not shown) that emits pulsed laser light. That is, the laser light irradiating the superimposed wafer T held on the chuck 100 from the laser irradiation system 110 is a pulsed laser, and its power alternates between 0 (zero) and its maximum value. Furthermore, the laser head 111 may also have a device other than a laser oscillator, such as an amplifier. The lens 112 is a cylindrical component that irradiates the interface with laser light L1 onto the superimposed wafer T held on the chuck 100.

[0030] The laser head 111 is supported by a support member 113. The laser head 111 can be freely raised and lowered along a track 114 extending in the vertical direction via a lifting mechanism 115. Furthermore, the laser head 111 can be freely moved in the Y-axis direction via a moving mechanism 116. Both the lifting mechanism 115 and the moving mechanism 116 are supported by support columns 117.

[0031] Above the suction cup 100, a first imaging mechanism 120 is provided on the positive Y-axis side of the laser irradiation system 110. The first imaging mechanism 120 includes, for example, a macro camera with a magnification of 2x, and has a numerical aperture capable of detecting at least the outer edge of the first wafer W as described later. The first imaging mechanism 120 is freely raised and lowered via a lifting mechanism 121, and further freely moved in the Y-axis direction via a moving mechanism 122. The moving mechanism 122 is supported by a support column 117.

[0032] The first imaging unit 120 photographs the outer end of the first wafer W (overlapping wafer T). The image captured by the first imaging unit 120 is used, for example, for the alignment of the first wafer W described later, and for determining the irradiation position of the interface laser light described later (alignment of the laser irradiation system 110). The first imaging unit 120 is, for example, equipped with a coaxial lens and irradiates infrared (IR) light, and also receives reflected light from the object.

[0033] As shown in FIG1, when the peripheral portion We of the first wafer W is chamfered (rounded), it is difficult to accurately detect the outer end of the first wafer W using a camera with a high numerical aperture. However, in this embodiment, by using a macro camera with a lower numerical aperture as the first imaging mechanism 120 for photographing the outer end of the first wafer W (overlapping wafer T), the outer end can still be detected even when the peripheral portion We of the first wafer W is chamfered (rounded). However, if the first imaging mechanism 120 can properly focus on the outer peripheral end of the first wafer W by using a super macro camera with a higher numerical aperture than the macro camera due to factors such as the shape of the first wafer W, a super macro camera (not shown) can be added in addition to the macro camera, or the super macro camera can replace the macro camera. The super macro camera has a magnification of 10x, and its field of view is approximately 1 / 5 of that of the first imaging mechanism 120, while its pixel size is also approximately 1 / 5 of that of the first imaging mechanism 120. When using the super macro camera to photograph the outer periphery of the first wafer W, the alignment of the first wafer W and the determination of the laser illumination position at the interface can be performed with higher precision.

[0034] Furthermore, in the illustrated example, the suction cup 100 can be rotated and moved horizontally relative to the laser head 111 by means of the rotating mechanism 103 and the horizontal moving mechanism 104, but the laser head 111 can also be rotated and moved horizontally relative to the suction cup 100. Additionally, both the suction cup 100 and the laser head 111 can be rotated and moved horizontally relative to each other.

[0035] The internal modification apparatus irradiates the interior of the first wafer W with an internal laser light L2 (e.g., NIR light such as YAG laser). In the internal modification apparatus 61, the first wafer W is modified at the spotting point of the internal laser light L2, and a peripheral modification layer M2 is formed as the base point for removing the peripheral portion We of the first wafer W, and a segmentation modification layer M3 is formed as the base point for miniaturizing the peripheral portion We to be removed.

[0036] The internal modification device 61 has a configuration substantially the same as that of the interface modification device 60. That is, the internal modification device 61 has a chuck 200 for holding the superimposed wafer T, a laser irradiation system 210, and a second imaging mechanism 220. The chuck 200 has an air bearing 201, a sliding stage 202, a rotation mechanism 203, a horizontal movement mechanism 204, a track 205, and a base 206, and can move about the θ axis (vertical axis) and in the horizontal direction. The laser irradiation system 210 has a laser head 211, a lens 212, a support member 213, a track 214, a lifting mechanism 215, and a moving mechanism 216. The lifting mechanism 215 and the moving mechanism 216 are each supported by a support column 217. The laser irradiation system 210 irradiates the superimposed wafer T held in the chuck 200 with internal laser light L2. The second imaging mechanism 220 moves freely through the lifting mechanism 221 and the moving mechanism 222. The moving mechanism 222 is supported by the support column 217.

[0037] Furthermore, the second imaging unit 220 includes, for example, a super macro camera with a magnification of 10x. The second imaging unit 220 images the reference modified layer M1 formed on the back surface Wb of the first wafer W (overlapping wafer T). The image captured by the second imaging unit 220 is used, for example, to determine the irradiation position of the internal laser light L2 (adjustment of the laser irradiation system 210) as described later. The second imaging unit 220, for example, has a coaxial lens and irradiates infrared (IR) light, and also receives reflected light from the object.

[0038] In this embodiment, the reference modification layer M1 formed on the back surface Wb (plane) of the first wafer W is photographed instead of the outer end of the first wafer W with rounded corners. Therefore, a high numerical aperture super macro camera can be used as the second imaging mechanism 220. Furthermore, by using a super macro camera as the second imaging mechanism 220, compared to photographing the reference modification layer M1 with a macro camera with a lower numerical aperture, a higher precision determination of the irradiation position of the internal laser light L2 can be achieved. However, the imaging mechanism of the second imaging mechanism 220 is not limited to a super macro camera. A macro camera (not shown) may also be provided in addition to the super macro camera, or a macro camera may replace the super macro camera.

[0039] The separation device 62 uses the peripheral modified layer M2 formed through the internal modified device 61 as a base point to remove at least the peripheral portion We of the first wafer W from the second wafer S, i.e., to perform edge cutting. The edge cutting method can be chosen arbitrarily. In one example, a wedge-shaped plate can be inserted into the separation device 62. For another example, air or water can be sprayed onto the peripheral portion We to apply an impact to it.

[0040] The wafer transport device 70 is, for example, disposed on the positive Y-axis side of the interface modification device 60 and the internal modification device 61. The wafer transport device 70 holds and transports the overlapping wafer T through an adsorption holding surface (not shown), and for example has two transport arms 71, 71. Each transport arm 71 is supported by a multi-jointed arm member 72 and can move freely in the horizontal direction, the vertical direction, and around the horizontal and vertical axes. Furthermore, the wafer transport device 70 can transport the overlapping wafer T to the etching device 40, the cleaning device 41, the interface modification device 60, the internal modification device 61, the separation device 62, and the processing device 80 described later.

[0041] A processing device 80 is provided in the third processing block B3.

[0042] The processing apparatus 80 includes a rotary table 81. The rotary table 81 rotates freely about a vertical rotation centerline 82 via a rotation mechanism (not shown). Two chucks 83 are provided on the rotary table 81 to hold and hold the superimposed wafer T. The chucks 83 are evenly arranged on the same circumference as the rotary table 81. The two chucks 83 can be moved to the transfer position A0 and the processing position A1 by rotating the rotary table 81. Furthermore, the two chucks 83 can be rotated about a vertical axis by the rotation mechanism (not shown).

[0043] The overlapping wafer T is transferred at transfer position A0. A polishing unit 84 is arranged at processing position A1, which polishes the first wafer W while the second wafer S is held in place by a suction cup 83. The polishing unit 84 has a polishing part 85, which has an annular and rotatable polishing whetstone (not shown). Furthermore, the polishing part 85 can move vertically along the support column 86.

[0044] The wafer processing system 1 described above includes a control device 90. The control device 90 is, for example, a computer equipped with a CPU and memory, and has a program storage unit (not shown). The program storage unit stores a program for controlling the processing of the overlapping wafer T in the wafer processing system 1. Alternatively, the program may be recorded on a computer-readable recording medium H and installed from that recording medium H onto the control device 90.

[0045] Next, the wafer processing performed using the wafer processing system 1 configured as described above will be described. In this embodiment, a superimposed wafer T is formed in advance in a bonding device (not shown) outside the wafer processing system 1.

[0046] First, a cassette C containing multiple overlapping wafers T is placed on the cassette placement stage 10 of the loading / unloading station 2. Next, the overlapping wafers T in the cassette C are removed by the wafer transport device 20 and transported to the transfer device 30. The overlapping wafers T transported to the transfer device 30 are then transported to the interface modification device 60 by the wafer transport device 50.

[0047] In the interface modification apparatus 60, the overlapping wafer T, held in the chuck 100, is first moved to the first imaging position. The first imaging position is the position where the first imaging mechanism 120 can photograph the outer end (edge) of the first wafer W. In the first imaging position, while the chuck 100 is rotated, the first imaging mechanism 120 photographs an image of the outer end of the first wafer W in a 360-degree circumferential direction (step St1 in Figure 5). The photographed image is output from the first imaging mechanism 120 to the control device 90.

[0048] In the control device 90, the eccentricity between the center of the suction cup 100 and the center of the first wafer W is calculated from the image of the first imaging mechanism 120. Furthermore, in the control device 90, based on the calculated eccentricity, the movement amount of the suction cup 100 is calculated to correct the Y-axis component of the eccentricity. Based on this calculated movement amount, the control device 90 moves the suction cup 100 horizontally along the Y-axis direction to correct the eccentricity between the center of the suction cup 100 and the center of the first wafer W. Also, in the control device 90, the position of the outer end of the first wafer W is identified from the image of the first imaging mechanism 120. Furthermore, in the control device 90, based on the identified position of the outer end of the first wafer W, an irradiation area for the interface laser light L1 used to form the unbonded region Ae is set. The area irradiated by the laser light L1 on the interface is, for example, set as an annular region with a desired radial width d1 (see Figure 6(a)) extending from the outer end of the first wafer W.

[0049] After correcting the eccentricity between the chuck 100 and the first wafer W and setting the irradiation area of ​​the interface laser light L1, the interface laser light L1 is pulsed onto the bonding interface between the first wafer W and the second wafer S in the irradiation area set in step St1 (step St2 in FIG5) while the chuck 100 and the laser head 111 are rotated relative to each other and moved relative to each other in the horizontal direction along the Y-axis. This modifies the bonding interface between the first wafer W and the second wafer S (in the illustrated example, the interface between the first wafer W and the bonding film Fw). Furthermore, in the embodiment, the modification of the bonding interface includes, for example, amorphization of the bonding film Fw at the irradiation position of the interface laser light L1 and peeling of the first wafer W and the second wafer S.

[0050] In the interface modification apparatus 60, the interface between the first wafer W and the second wafer S is modified by irradiation of laser light L1, as shown in Figures 6(a) and 7, forming an unbonded region Ae with reduced bonding strength between the first wafer W and the second wafer S. In the edge cutting described later, the peripheral portion We of the first wafer W, which is the target of removal, is removed. Because of the existence of the unbonded region Ae with reduced bonding strength, the peripheral portion We can be appropriately removed.

[0051] After forming the unbonded region Ae, the spot position of the interface laser light L1 (the irradiation position of the interface laser light L1) is moved to the back surface Wb of the first wafer W in the interface modification apparatus 60. Then, while rotating the chuck 100 relative to the laser head 111, the interface laser light L1 is pulsed onto the back surface Wb of the first wafer W (step St3 in FIG. 5). In this way, as shown in FIG. 6(b) and FIG. 7, the back surface Wb of the first wafer W is modified.

[0052] In the interface modification apparatus 60, interface laser light L1 is irradiated onto the back surface Wb of the first wafer W to modify it, thereby forming a reference modified layer M1, which serves as a reference for the adjustment of the laser irradiation system 210 when forming the peripheral modified layer M2 described later. Furthermore, the formation position of the reference modified layer M1 in the radial direction of the first wafer W is preferably set at a position slightly offset radially from the inner end (hereinafter referred to as "inner end") of the unbonded region Ae, and preferably, as shown in FIG. 6(b), is set slightly further radially outward than the inner end of the unbonded region Ae, so that the interior laser light L2 described later appropriately irradiates the target position inside the first wafer W. However, the formation position of the reference modified layer M1 may also be radially inward in the back surface Wb of the first wafer W than the inner end of the unbonded region Ae.

[0053] The superimposed wafer T, having formed the unbonded region Ae and the reference modification layer M1, is then transported to the internal modification device 61 via the wafer transport device 70. In the internal modification device 61, the superimposed wafer T, held in the chuck 200, is first moved to the second imaging position. The second imaging position is where the second imaging mechanism 220 can photograph the reference modification layer M1 formed on the first wafer W. At the second imaging position, while rotating the chuck 200, an image of the reference modification layer M1 at a circumferential 360-degree angle on the first wafer W is photographed via the second imaging mechanism 220 (step St4 in Figure 5). The photographed image is output from the second imaging mechanism 220 to the control device 90.

[0054] In the control device 90, the eccentricity between the center of the suction cup 200 and the center of the first wafer W is calculated from the image of the second imaging mechanism 220. Furthermore, based on the calculated eccentricity, the control device 90 calculates the movement amount of the suction cup 200 to correct the Y-axis component of the eccentricity. Based on this calculated movement amount, the control device 90 moves the suction cup 200 horizontally along the Y-axis and corrects the eccentricity between the center of the suction cup 200 and the center of the first wafer W. Also, the control device 90 identifies the formation position of the reference modified layer M1 from the image of the second imaging mechanism 220. Furthermore, based on the identified formation position of the reference modified layer M1, the control device 90 sets the irradiation position (radial position) of the laser light L2 used to form the peripheral modified layer M2. The irradiation position of the internal laser light L2 is, for example, set at a position that moves a desired radial distance d2 from the formation position of the reference modified layer M1 (see Figure 6(c)), specifically at the position corresponding to the inner end of the unbonded region Ae.

[0055] After correcting the eccentricity between the chuck 200 and the first wafer W and setting the irradiation position of the internal laser light L2, then, as shown in Figures 6(c) and 7, the internal laser light L2 is irradiated into the interior of the first wafer W, and a peripheral modification layer M2 and a segmentation modification layer M3 are formed sequentially (step St5 in Figure 5). The peripheral modification layer M2 becomes the base point when removing the peripheral portion We in the edge cutting process described later. The segmentation modification layer M3 becomes the base point when miniaturizing the removed peripheral portion We. Furthermore, in the figures used in the following description, the illustration of the segmentation modification layer M3 may be omitted to avoid making the illustration too complex. Also, the formation order of the peripheral modification layer M2 and the segmentation modification layer M3 is not particularly limited.

[0056] In the conventional internal modification apparatus 61, the irradiation position of the internal laser light L2 (the formation position of the peripheral modification layer M2) is determined based on the outer end of the first wafer W, similar to step St1 described above. In this case, as shown in FIG1, the peripheral portion We of the first wafer W is chamfered, so as mentioned above, an optical system with a low numerical aperture (NA) (e.g., a macro camera) must be used as the imaging mechanism, resulting in low detection accuracy at the outer end of the first wafer W. Furthermore, when the irradiation positions of both the interface laser light L1 and the internal laser light L2 are determined based on the outer end of the first wafer W, the detection accuracy deviations between the interface modification apparatus 60 and the internal modification apparatus 61 are superimposed, resulting in a concern that the formation position of the peripheral modification layer M2 may deviate more significantly from the target position. Specifically, for example, when the detection accuracy of each apparatus has a deviation of approximately ±10 μm, there is a concern that the superposition of these accuracy deviations may result in a deviation of up to approximately 20 μm. Therefore, there is concern that the peripheral part We cannot be properly removed.

[0057] Regarding this point, by using the technology of the present invention, the irradiation position of the internal laser light L2 is determined based on the reference modified layer M1 formed on the back surface Wb (plane) of the first wafer W, rather than the outer end of the first wafer W (adjustment of the laser irradiation system 210). Therefore, compared to using the outer end of the first wafer W (which has undergone chamfering) as the reference, a higher numerical aperture (NA) optical system (super macro camera) can be used to perform more precise adjustment of the laser irradiation system 210. More specifically, the formation position of the peripheral modified layer M2 and the formation area of ​​the unbonded area Ae can be more appropriately controlled, resulting in the appropriate removal of the peripheral portion We of the first wafer W.

[0058] Furthermore, in this embodiment, as described above, an ultra-macro camera is used as the second imaging mechanism 220. However, compared to the case where the formation position of the peripheral modified layer M2 is determined based on the outer end of the first wafer W, the case where a macro camera is used as the second imaging mechanism 220 can still appropriately determine the formation position of the peripheral modified layer M2 relative to the formation area of ​​the unbonded region Ae. However, by using an ultra-macro camera with a numerical aperture higher than that of a macro camera as the second imaging mechanism 220, the detection accuracy of the reference modified layer M1 can be improved. As a result, the formation position of the peripheral modified layer M2 relative to the formation area of ​​the unbonded region Ae can be determined more appropriately.

[0059] Furthermore, within the first wafer W, crack C2 extends from the peripheral modified layer M2 in the thickness direction. The extension of crack C2 is controlled, for example, by adjusting the formation position of the peripheral modified layer M2 in the thickness direction of the first wafer W, or, for example, by adjusting the output and defocusing degree of the laser light during the formation of the peripheral modified layer M2. In the edge cutting process described later, in addition to the peripheral modified layer M2, the peripheral portion We is also removed from the second wafer S using crack C2 as a reference point.

[0060] An overlapping wafer T with a peripheral modification layer M2 and a dividing modification layer M3 is formed, and then transported to a separation device 62 via a wafer transport device 50. In the separation device 62, as shown in FIG6(d), the peripheral portion We of the first wafer W is removed, that is, edge cutting is performed (step St6 in FIG5). At this time, the peripheral portion We is peeled off from the center of the first wafer W (inside the radial direction of the peripheral portion We) with the peripheral modification layer M2 as the base point, and is completely peeled off from the second wafer S with the unbonded area Ae as the base point. At this time, the removed peripheral portion We is further miniaturized with the dividing modification layer M3 as the base point.

[0061] When removing the peripheral portion We, a wedge-shaped plate B can be inserted, for example, at the interface between the first wafer W and the second wafer S forming the overlapping wafer T (see Figure 6(d)).

[0062] After removing the overlapping wafer T at the periphery We of the first wafer W, it is then transported by the wafer transport device 70 to the chuck 83 of the processing device 80. Next, the chuck 83 is moved to the processing position A1, and as shown in FIG8(a), the back surface Wb of the first wafer W is ground by the grinding unit 84 (step St7 in FIG5). Through this grinding process, the first wafer W (overlapping wafer T) is reduced to the desired target thickness. Furthermore, the ground surface of the first wafer W can then be cleaned with cleaning fluid using a cleaning fluid nozzle (not shown).

[0063] Next, the overlapping wafer T is transported by the wafer transport device 70 to the etching device 40. In the etching device 40, as shown in FIG8(b), the polishing surface of the first wafer W is wet-etched by the chemical solution E (step St8 in FIG5). Polishing marks may be formed on the polishing surface after being polished by the aforementioned processing device 80. In this step St8, the first wafer W (overlapping wafer T) is made thinner by wet etching, and polishing marks are removed to smooth the polishing surface.

[0064] Next, the overlapping wafer T is transported from the wafer transport device 50 to the cleaning device 41. In the cleaning device 41, a cleaning laser L3 is used to irradiate the residual film (bonding films Fw, Fs) on the surface Sa of the second wafer S exposed by the removal of the peripheral portion We, as shown in FIG8(c), to remove the residual film and particles P and expose the surface Sa of the second wafer S (step St9 in FIG5).

[0065] In this step St9, as described above, in order to completely remove the peripheral portion We of the first wafer W, the entire surface of the second wafer S corresponding to the peripheral portion We is irradiated with cleaning laser light L3. Specifically, while rotating the overlapping wafer T, the irradiation position of the cleaning laser light L3 is moved radially through an electrical scanner (not shown), and the cleaning laser light L3 is periodically irradiated from the laser head. In this way, the entire surface of the residual film can be irradiated with cleaning laser light L3, that is, the residual film on the surface Sa can be completely removed.

[0066] Furthermore, in the cleaning apparatus 41, the polishing surface of the first wafer W and the back surface Sb of the second wafer S can be further cleaned by using a cleaning liquid nozzle (not shown) through the cleaning liquid.

[0067] Here, in this embodiment, after wet etching (step St8) is performed on the polished surface of the first wafer W, the residual film on the surface Sa of the second wafer S is removed (step St9). The order of wet etching and residual film removal is not particularly limited. Specifically, the residual film can be removed after removing the peripheral portion We of the first wafer W (step St6) and before polishing (step St7), or it can be removed after polishing (step St7) and before wet etching (step St8).

[0068] However, when removing residual film before wet etching (step St8), there is concern that the solution supplied during wet etching may affect the device layers Dw and Ds. Specifically, in the case of wet etching after removing residual film using a cleaning laser L3 as shown in FIG9(a) and FIG9(b), as shown in FIG9(c), due to the influence of the supplied solution E, the sides of the bonding films Fw and Fs exposed by removing residual film will be removed, which raises concerns about damaging the device layers Dw and Ds. In view of this, it is preferable to perform wet etching (step St8) on the polished surface of the first wafer W and removal of residual film on the surface Sa of the second wafer S (step St9) in this order.

[0069] Then, the overlapping wafer T, after all processing has been performed, is transported by the wafer transport device 50 to the transfer device 30, and then by the wafer transport device 20 to the cassette C of the cassette stage 1. Thus, the series of wafer processing in the wafer processing system 1 is completed.

[0070] Through the above embodiment, before forming the peripheral modification layer M2 inside the first wafer W as the base point when removing the peripheral portion We, a reference modification layer M1 is formed on the back surface Wb of the first wafer W as the reference for the irradiation position of the internal laser light L2. Furthermore, when forming the peripheral modification layer M2 inside the first wafer W, the irradiation position of the internal laser light L2 is determined with the reference modification layer M1 formed on the back surface Wb of the first wafer W as the target. In this way, by detecting the target formed on the back surface Wb of the first wafer W, i.e., the plane, with a camera, compared to the conventional method of detecting the outer end (edge ​​portion) after chamfering with a camera, an optical system with a higher numerical aperture (NA) (super macro camera) can be used. As a result, the irradiation position of the internal laser light L2 can be adjusted with higher precision and accuracy (adjustment of the laser irradiation system 210). Therefore, when the wafer processing system 1 is equipped with a plurality of laser irradiation devices (interface modification device 60 and internal modification device 61 in this embodiment), the shift of the laser light irradiation position between the laser irradiation devices can be suppressed.

[0071] Furthermore, in the above embodiment, the target base modification layer M1 is formed at a position slightly offset radially outward from the incident position of the laser light L2 inside the back surface Wb of the first wafer W (the formation position of the peripheral modification layer M2). Normally, when silicon is modified by laser etching of the first wafer W, there is a concern that the internal laser light L2 cannot properly penetrate the modified portion (the base modification layer M1 in this embodiment), and the peripheral modification layer M2 cannot be properly formed. Regarding this point, in the above embodiment, the base modification layer M1 is formed at a position slightly offset from the incident position of the internal laser light L2, so the incident position of the internal laser light L2 is not obstructed when forming the peripheral modification layer M2, and the peripheral modification layer M2 can be properly formed.

[0072] Furthermore, as described above, when a reference modifier layer M1 is formed on the back surface Wb of the first wafer W, the internal laser light L2 cannot properly penetrate the interior of the first wafer W. In this case, if the reference modifier layer M1 is formed radially outward from the incident position of the internal laser light L2, there is a concern that the segmented modifier layer M3 shown in FIG. 6(c) cannot be properly formed. In view of this, the formation position of the reference modifier layer M1 is preferably determined to be slightly radially outward from the incident position of the internal laser light L2, and not overlapping with the formation position of the segmented modifier layer M3 when viewed from above, or slightly radially inward from the incident position of the internal laser light L2.

[0073] Furthermore, in the above embodiment, the crack C2 that extends in the thickness direction when the peripheral modified layer M2 is formed reaches Wa and the back surface Wb of the first wafer W in a slightly perpendicular manner, but the method of extending the crack C2 is not limited to this.

[0074] Specifically, as shown in FIG10, the formation position of the peripheral modification layer M2 can be controlled to be slightly more radially inward than the inner end of the unbonded region Ae, so that the crack C2 extending downward from the lowermost peripheral modification layer M2 can be connected with the crack C4 extending obliquely upward from the inner end of the unbonded region Ae. In this case, compared to the case where the crack C2 reaches the surface Wa slightly perpendicularly, the crack can be stably extended from the surface Wa of the first wafer W to the back surface Wb, that is, the removal of the peripheral portion We can be stably and appropriately performed.

[0075] Furthermore, in this case, the reference modified layer M1 can also be formed at a position slightly offset from the formation position of the peripheral modified layer M2 on the back surface Wb, as shown in FIG10, and the irradiation position of the internal laser light L2 can be appropriately determined in the same manner as in the above embodiment. Furthermore, in this case, as shown in FIG10, the formation position of the reference modified layer M1 does not need to be offset from the position corresponding to the inner end of the unbonded region Ae.

[0076] Alternatively, as shown in Figure 11, adjacent peripheral modified layers M2 can be staggered in the thickness and radial directions on the surface Wa side inside the first wafer W, i.e., arranged in an inclined direction, instead of simply allowing the crack C4 to extend obliquely upward from the inner end of the unbonded region Ae as shown in Figure 10. In this case, compared to the case shown in Figure 10, it is easier to make the crack C4 advance obliquely upward.

[0077] Furthermore, in this case, the formation position of the reference modified layer M1 is preferably determined as shown in FIG11, to be slightly more radially outward than the peripheral modified layer M2 low which is formed most radially outward among the plurality of peripheral modified layers M2, or slightly more radially inward than the peripheral modified layer M2 high which is formed most radially inward.

[0078] For example, as shown in FIG12, the peripheral modification layer M2 can be arranged in an inclined direction along the entire thickness direction of the first wafer W, instead of arranging adjacent peripheral modification layers M2 in an inclined direction only on the surface Wa side inside the first wafer W as shown in FIG11. In this case, the generation of gaps in the removed peripheral portion We and the central portion of the first wafer W after removing the peripheral portion We is suppressed. Furthermore, this suppresses the generation of particles inside the wafer processing system 1 and suppresses the degradation of the quality of the first wafer W (device wafer) as a product.

[0079] Furthermore, in this case, the preferred formation position of the reference modified layer M1 is as shown in FIG12, which is determined to be slightly more radially outward than the peripheral modified layer M2 low, which is formed most radially outward among the plurality of peripheral modified layers M2, or slightly more radially inward than the peripheral modified layer M2 high, which is formed most radially inward.

[0080] Furthermore, in the above embodiment, the first wafer W is thinned after edge cutting through the grinding process of the processing apparatus 80, but the thinning method of the first wafer W is not limited to this. Specifically, for the overlapping wafer T with the unbonded region Ae and the reference refining layer M1 formed, as shown in FIG13(a), in the internal refining apparatus 61, in addition to the peripheral refining layer M2 which serves as the base point for peeling the peripheral portion We, an inner surface refining layer M4 which serves as the base point for separating and thinning the first wafer W is formed. A crack C5 extending toward the surface of the first wafer W is formed from the inner surface refining layer M4, and the crack C5 is connected to the peripheral refining layer M2 or to the top end of the crack C2 extending from the peripheral refining layer M2 in the thickness direction. Then, in the separation apparatus 62, as shown in FIG13(b), the first wafer W is held by adsorption and holding surface of the separation arm ARM, and the second wafer S is held by a suction cup (not shown). Then, with the first wafer W held by adsorption and holding surface, the separation arm ARM is raised, thereby separating and thinning the first wafer W based on the internal surface modification layer M4. At this time, the peripheral portion We of the first wafer W and the back surface Wb side of the first wafer W are integrally peeled off from the second wafer S.

[0081] In this case, as shown in FIG13(a), a reference modified layer M1 can also be formed at a position slightly offset from the formation position of the peripheral modified layer M2 on the back surface Wb, thereby appropriately determining the irradiation position of the internal laser light L2 in the same manner as in the above embodiment. Furthermore, in this case, in order to properly form an internal surface modified layer M4 inside the first wafer W, the formation position of the reference modified layer M1 is preferably determined to be slightly offset radially outward from the formation position of the peripheral modified layer M2.

[0082] Furthermore, even when the peripheral portion We of the first wafer W is removed integrally with the back side Wb of the first wafer, the peripheral modification layers M2 can still be arranged in an inclined direction. In this case, the formation position of the reference modification layer M1 is preferably determined to be slightly further outward in the radial direction than the peripheral modification layer M2 low formed most radially outward among the plurality of peripheral modification layers M2.

[0083] Furthermore, in the above embodiment, after the unbonded region Ae is formed in the interface modification device 60, the peripheral modification layer M2 is formed in the internal modification device 61, but the formation order of the unbonded region Ae and the peripheral modification layer M2 is not limited to this.

[0084] In this case, in the internal modification apparatus 61, a macro camera (not shown) is used to align the first wafer W with the outer end of the first wafer W as a reference, and to determine the irradiation position of the internal laser light L2. In other words, the formation position of the peripheral modification layer M2 is determined with the outer end of the first wafer W as a reference. Furthermore, in the internal modification apparatus 61, after the peripheral modification layer M2 and the segmentation modification layer M3 are formed, the spot position of the internal laser light L2 (the irradiation position of the internal laser light L2) is moved to the back surface Wb of the first wafer W, and a reference modification layer M1 is formed as a reference for determining the irradiation position of the interface laser light L1 (the formation position of the unbonded region Ae).

[0085] Furthermore, in the interface modification apparatus 60, a super macro camera (not shown) is used to align the first wafer W with reference to the reference modification layer M1, and to determine the irradiation position of the interface laser light L1. In other words, the formation position of the unbonded region Ae is determined with reference to the reference modification layer M1 formed on the back surface Wb of the first wafer W.

[0086] Through the technology of the present invention, if the peripheral modification layer M2 is formed before the unbonded region Ae is formed, the reference modification layer M1 formed on the back surface Wb of the first wafer W can still be used as a reference to determine the irradiation position of the interface laser light L1. In this way, by using a camera to detect the reference mark formed on the back surface Wb of the first wafer W, that is, formed on the plane, as the target, compared with the conventional case of using a camera to detect the outer end (edge) after chamfering, an optical system with a higher numerical aperture (NA) (super macro camera) can be used. As a result, the irradiation position of the interface laser light L1 can be adjusted with higher precision and accuracy (adjustment of the laser irradiation system 110). Furthermore, by means of this, when the wafer processing system 1 is equipped with a plurality of laser irradiation devices (interface modification device 60 and internal modification device 61 in this embodiment), the shift in the formation position of the peripheral modification layer M2 and the formation area of ​​the unbonded area Ae can be appropriately suppressed, and as a result, the peripheral portion We of the first wafer W can be appropriately removed.

[0087] Furthermore, in the above embodiment, the peripheral portion We of the first wafer W is peeled off (edge ​​cutting) in the separation device 62, but the peripheral portion We can also be removed by the processing device 80, replacing the separation device 62 for edge cutting in the wafer processing system 1. Specifically, in the case of independently removing the peripheral portion We of the first wafer W, the peripheral portion We can be removed from the second wafer S by utilizing the grinding resistance generated during the grinding process in the processing device 80. Also, in the case of removing the peripheral portion We of the first wafer W integrally with the back surface Wb of the first wafer W, the separation of the first wafer W can also be performed in the processing device 80 when the overlapping wafer T is transferred from the wafer transport device 70 to the chuck 83. In these cases, the processing device 80 functions as a "peripheral removal device" according to the technology of the present invention.

[0088] It should be understood that all embodiments of the present invention are illustrative and not intended to limit. The above embodiments may be omitted, substituted, or modified in various forms without departing from the scope and spirit of the appended patent applications. [Simplified Explanation of the Diagram]

[0008] Figure 1 is a side view showing an example of the configuration of an overlapping wafer processed by a wafer processing system. Figure 2 is a top view showing the configuration of the wafer processing system according to the present embodiment. Figure 3 is a top view showing the configuration of the interface modification apparatus and the internal modification apparatus. Figure 4 is a longitudinal sectional view showing the configuration of the interface modification apparatus and the internal modification apparatus. Figure 5 is a flowchart showing the main steps of wafer processing according to the present embodiment. Figures 6(a) to (d) are schematic diagrams showing the main steps of wafer processing according to the present embodiment. Figure 7 is a cross-sectional view showing the state of the unbonded area, the reference modification layer, the peripheral modification layer, and the partition modification layer formed on the first wafer. Figures 8(a) to (c) are schematic diagrams showing the main steps of wafer processing according to the present embodiment. Figures 9(a) to (c) are schematic diagrams showing the effect of wet etching on the device layer. Figure 10 is a schematic diagram showing other removal examples of the peripheral portion of the first wafer. Figure 11 is a schematic diagram showing other examples of removal of the peripheral portion of the first wafer. Figure 12 is a schematic diagram showing other examples of removal of the peripheral portion of the first wafer. Figures 13(a) to (b) are schematic diagrams showing other examples of removal of the peripheral portion of the first wafer.

Claims

1. A method for processing an overlapping substrate, comprising the steps of: forming a peripheral modification layer along the boundary between the peripheral portion of the first substrate to be removed and the central portion of the first substrate; forming an unbonded area in the peripheral portion where the bonding strength between the first substrate and the second substrate is weakened; forming a reference modification layer on the surface of the first substrate on the side not bonded to the second substrate, serving as a reference for determining the formation position of either the peripheral modification layer or the unbonded area; and removing the peripheral portion using the peripheral modification layer as a reference point.

2. The overlapping substrate processing method as described in claim 1, wherein, The unbonded area, the reference modified layer, and the peripheral modified layer are formed in this order; the formation position of the unbonded area and the formation position of the reference modified layer are determined with the outer end of the first substrate as a reference; the reference modified layer is formed in a manner that offsets radially from the position corresponding to the inner end of the unbonded area.

3. The overlapping substrate processing method as described in claim 1, wherein, The unbonded area, the reference modified layer, and the peripheral modified layer are formed in this order; the formation position of the unbonded area and the formation position of the reference modified layer are determined with the outer end of the first substrate as a reference; the reference modified layer is formed in a manner that offsets radially from the position corresponding to the predetermined formation position of the peripheral modified layer.

4. The overlapping substrate processing method as described in claim 2 or 3 further includes the following steps: detecting the reference modified layer formed on the non-bonded side surface of the first substrate from the non-bonded side surface of the first substrate using a photographic mechanism; and forming the peripheral modified layer by irradiating laser light from the non-bonded side surface of the first substrate during the formation of the peripheral modified layer.

5. The overlapping substrate processing method as described in claim 2 or 3 further includes the following steps: detecting the outer end of the first substrate with a first imaging mechanism; and detecting the reference modified layer formed on the non-bonding side surface of the first substrate with a second imaging mechanism; and setting the numerical aperture of the second imaging mechanism to be higher than the numerical aperture of the first imaging mechanism.

6. The overlapping substrate processing method as described in claim 1, wherein, The peripheral modified layer, the reference modified layer, and the unbonded area are formed in this order; the formation positions of the peripheral modified layer and the reference modified layer are determined with the outer end of the first substrate as a reference; the reference modified layer is formed in a manner that offsets radially from the position corresponding to the formation position of the peripheral modified layer.

7. The overlapping substrate processing method as described in claim 6 further includes the following steps: detecting the outer end of the first substrate with a first imaging mechanism; and detecting the reference modified layer formed on the non-bonding side surface of the first substrate with a second imaging mechanism; and setting the numerical aperture of the first imaging mechanism to be higher than the numerical aperture of the second imaging mechanism.

8. The overlapping substrate processing method as described in any one of claims 1 to 3, 6 and 7 further includes the following steps: wet etching the first substrate after the peripheral portion has been removed; and removing the surface film remaining on the surface of the second substrate exposed after the peripheral portion has been removed by irradiation with laser light.

9. The overlapping substrate processing method as described in claim 8, wherein, The removal of the surface film is performed after wet etching of the first substrate.

10. The overlapping substrate processing method as described in any one of claims 1 to 3, 6, and 7 further includes the following steps: forming an internal surface modification layer as a base point when separating the first substrate; and removing the peripheral portion integrally with the non-bonding side of the first substrate when removing the peripheral portion.

11. The overlapping substrate processing method as described in any one of claims 1 to 3, 6, and 7, wherein, A plurality of peripheral modified layers are formed inside the first substrate; adjacent peripheral modified layers are formed in a manner that offsets them in the thickness direction and radial direction of the first substrate.

12. A composite substrate processing system for processing a composite substrate formed by bonding a first substrate and a second substrate, comprising: an internal modification device for forming a peripheral modification layer along the boundary between the peripheral portion of the first substrate to be removed and the central portion of the first substrate; an interface modification device for forming an unbonded region in the peripheral portion where the bonding strength between the first substrate and the second substrate is weakened; a reference forming device for forming a reference modification layer on the surface of the first substrate on the side not bonded to the second substrate, serving as a reference for determining the formation position of either the peripheral modification layer or the unbonded region; a peripheral removal device for removing the peripheral portion using the peripheral modification layer as a base point; and a control device.

13. The overlapping substrate processing system as described in claim 12, wherein, The reference forming apparatus and the interface modification apparatus are integrated; the control device performs the following control: using the outer end of the first substrate as a reference, determining the formation position of the unbonded area and the formation position of the reference modification layer; and forming the reference modification layer in a manner that offsets radially from the position corresponding to the inner end of the unbonded area.

14. The overlapping substrate processing system as described in claim 12, wherein, The reference forming apparatus and the interface modification apparatus are integrated; the control device performs the following control: using the outer end of the first substrate as a reference, determining the formation position of the unbonded area and the formation position of the reference modification layer; and forming the reference modification layer in a manner that offsets radially from a position corresponding to the predetermined formation position of the peripheral modification layer.

15. The overlapping substrate processing system as described in claim 13 or 14, wherein, The internal modification device includes a photographic mechanism that detects the reference modification layer formed on the non-bonded surface of the first substrate from the non-bonded surface side of the first substrate; the internal modification device forms the peripheral modification layer by irradiating laser light from the non-bonded surface side of the first substrate.

16. The overlapping substrate processing system as described in claim 13 or 14, wherein, The interface modification device includes a first imaging mechanism that detects the outer end of the first substrate; the internal modification device includes a second imaging mechanism that detects the reference modification layer formed on the non-bonded side surface of the first substrate; the second imaging mechanism has a higher numerical aperture than the first imaging mechanism.

17. The overlapping substrate processing system as described in claim 12, wherein, The reference forming apparatus and the internal modification apparatus are integrated; the control device performs the following control: using the outer end of the first substrate as a reference, determining the formation position of the peripheral modification layer and the formation position of the reference modification layer; and forming the reference modification layer in a manner that offsets radially from the position corresponding to the formation position of the peripheral modification layer.

18. The overlapping substrate processing system as described in claim 17, wherein, The interface modification device includes a first imaging mechanism that detects the outer end of the first substrate; the internal modification device includes a second imaging mechanism that detects the reference modification layer formed on the non-bonded side surface of the first substrate; the first imaging mechanism has a higher numerical aperture than the second imaging mechanism.

19. The overlapping substrate processing system as described in any one of claims 12 to 14, 17, and 18 further comprises: an etching apparatus for wet etching the first substrate after the peripheral portion has been removed; and a cleaning apparatus for removing the surface film remaining on the surface of the second substrate exposed after the peripheral portion has been removed by irradiation with laser light.

20. The overlapping substrate processing system as described in claim 19, wherein, The control device further performs the following control: after wet etching of the first substrate in the etching apparatus, the surface film is removed in the cleaning apparatus.

21. The overlapping substrate processing system as described in any one of claims 12-14, 17, and 18, wherein, The control device further performs the following controls: In the internal modification device, an internal surface modification layer is formed as a base point when the first substrate is separated; When the peripheral portion is removed in the peripheral removal device, the peripheral portion is removed integrally with the non-bonded side of the first substrate.

22. The overlapping substrate processing system as described in any one of claims 12-14, 17, and 18, wherein, The control device further performs the following control: in the internal modification device, a plurality of peripheral modification layers are formed inside the first substrate; and adjacent peripheral modification layers are formed in a manner that offsets them in the thickness direction and radial direction of the first substrate.

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