Substrate treatment device and substrate treatment method

Abstract

This substrate treatment device is for treating a superimposed substrate formed by laminating a first substrate, an interface layer which includes at least a laser absorption layer, and a second substrate. In the superimposed substrate, an outer circumferential region which includes an unjoined region of the first substrate and the second substrate and an inner circumferential region which is disposed in a joined region of the first substrate and the second substrate inside the outer circumferential region in the radial direction are set. A control unit executes: control for rotating the superimposed substrate, applying a laser beam to the superimposed substrate while moving the laser beam in the radial direction, and causing detachment at the interface between the first substrate and the laser absorption layer or at the interface between the interface layer and the laser absorption layer; and control for applying, in at least the outer circumferential region, the laser beam while moving the laser beam from inside to outside in the radial direction.

Description

Substrate processing apparatus and substrate processing method

[0001] The present disclosure relates to a substrate processing apparatus and a substrate processing method.

[0002] Patent Document 1 discloses a method for transferring a semiconductor element formed on a surface of a semiconductor substrate having a separation oxide film and a semiconductor element to a destination substrate. The method described in Patent Document 1 includes a step of irradiating the back surface of the semiconductor substrate with light to locally heat the separation oxide film, and a step of causing separation in the separation oxide film and / or at the interface between the separation oxide film and the semiconductor substrate, thereby transferring the semiconductor element to the destination substrate.

[0003] Japanese Patent Application Publication No. 2007-220749

[0004] The technique according to the present disclosure appropriately separates the laser absorption layer from the first substrate in a laminated substrate in which the laser absorption layer is formed at the interface between the first substrate and the second substrate.

[0005] One aspect of the present disclosure is a substrate processing apparatus that processes a laminated substrate formed by stacking a first substrate, an interface layer including at least a laser absorption layer, and a second substrate, the substrate processing apparatus comprising: a substrate holding unit that holds the laminated substrate; a laser irradiation unit that irradiates the laminated substrate held by the substrate holding unit with laser light; a movement mechanism that moves the substrate holding unit and the laser irradiation unit relatively in a horizontal direction; a rotation mechanism that rotates the substrate holding unit; and a control unit. The laminated substrate has an outer circumferential region that includes an unbonded region of the first substrate and the second substrate, and an inner circumferential region that is radially inward of the outer circumferential region and is disposed in a bonded region of the first substrate and the second substrate, and the control unit rotates the laminated substrate and irradiates the laminated substrate with the laser light while moving it in the radial direction, thereby causing peeling at the interface between the first substrate and the laser absorption layer, or at the interface between the interface layer and the laser absorption layer, and controls irradiating the laser light while moving it from the radially inner side to the radially outer side, at least in the outer circumferential region.

[0006] According to the present disclosure, in a laminated substrate in which a laser absorption layer is formed at the interface between a first substrate and a second substrate, the first substrate and the laser absorption layer can be appropriately separated.

[0007] 1 is a side view showing an example of the configuration of an overlapped wafer according to an embodiment; FIG. 2 is a plan view showing an outline of the configuration of a wafer processing system; FIG. 3 is a plan view showing an outline of the configuration of a laser irradiation device; FIG. 4 is a side view showing an outline of the configuration of a laser irradiation device; FIG. 5 is a side view showing an operation of a separation device; FIG. 6 is an explanatory diagram showing the appearance of an overlapped wafer irradiated with laser light; FIG. 7 is a flow diagram showing main steps of wafer processing in a wafer processing system; FIG. 8 is an explanatory diagram showing the appearance of heat generated in the overlapped wafer; FIG. 9 is an explanatory diagram showing the appearance of an overlapped wafer irradiated with laser light; FIG. 10 is an explanatory diagram showing the appearance of a first wafer and a laser absorption layer; FIG. 11 is an explanatory diagram showing the appearance of a first wafer and a laser absorption layer; FIG. 12 is a flow diagram showing main steps of wafer processing in a wafer processing system; FIG. 13 is an explanatory diagram showing regions of an overlapped wafer, the rotation speed of a chuck in each region, and the frequency of laser light in each region; FIG. 14 is a side view showing an outer peripheral region and a first inner peripheral region; FIG. 15 is an explanatory diagram showing the appearance of an overlapped wafer whose outer peripheral region is irradiated with laser light; FIG. 16 is an explanatory diagram showing the appearance of an overlapped wafer whose outer peripheral region is irradiated with laser light; FIG. 1 is an explanatory diagram showing the state of an overlapped wafer in which a second inner peripheral region and a first inner peripheral region are irradiated with laser light. FIG. 2 is an explanatory diagram showing the state of an overlapped wafer in which a first inner peripheral region is irradiated with laser light. FIG. 3 is an explanatory diagram showing the state of an overlapped wafer in which a central region is irradiated with laser light. FIG. 4 is an explanatory diagram showing the state of an overlapped wafer in which laser light is irradiated in another embodiment. FIG. 5 is an explanatory diagram showing the state of an overlapped wafer in which laser light is irradiated in another embodiment. FIG. 6 is an explanatory diagram showing the state of an overlapped wafer in which laser light is irradiated in another embodiment. FIG. 7 is an explanatory diagram showing the state of peeling of a peeling promoting layer and a laser absorbing layer. FIG. 8 is a flow chart showing main steps of wafer processing according to another embodiment.

[0008] In a semiconductor device manufacturing process, a device layer formed on a surface of a first semiconductor substrate (hereinafter referred to as "wafer") is transferred to a second wafer in an overlapped wafer formed by bonding two semiconductor substrates (hereinafter referred to as "wafers"). The transfer of the device layer to the second wafer is performed by irradiating a laser absorption layer formed between the first wafer and the device layer with laser light to peel the first wafer from the laser absorption layer. Specifically, for example, the overlapped wafer is rotated and the laser light is moved from the outer side to the inner side in the radial direction, and the laser absorption layer is irradiated with the laser light in pulses.

[0009] Here, the peripheral edge of the overlapped wafer has a chamfered portion (bevel portion), and this peripheral edge is not bonded. That is, the outer peripheral region of the overlapped wafer includes an unbonded region, and the bonding strength of the interface between the first wafer (including the device layer) and the second wafer is low at the boundary between the unbonded region and the bonded region. In such a case, when the outer peripheral region is irradiated with laser light, peeling occurs at the interface between the first wafer and the second wafer, where the bonding strength is low.

[0010] In this state, if the laser beam is irradiated in the outer peripheral region while moving radially inward, in the bonded region adjacent to the unbonded region in the radial direction, delamination tends to progress from the interface between the delaminated first wafer and the second wafer. That is, in the bonded region of the outer peripheral region, delamination does not occur at the desired interface between the first wafer and the laser absorption layer. As a result, it may be impossible to transfer the device layer of the first wafer to the second wafer.

[0011] The technology disclosed herein appropriately separates a first substrate and a second substrate from each other in a laminated substrate in which a laser absorption layer is formed at the interface between the first substrate and the second substrate. Hereinafter, a wafer processing system including a laser irradiation device as a substrate processing apparatus according to this embodiment, and a wafer processing method as a substrate processing method, will be described with reference to the drawings. Note that in this specification and the drawings, elements having substantially the same functional configurations are designated by the same reference numerals, and redundant description will be omitted.

[0012] 1 , a wafer processing system 1 according to this embodiment performs processing on a laminated wafer T, which is a laminated substrate formed by bonding a first wafer W and a second wafer S together. Hereinafter, the surface of the first wafer W that is bonded to the second wafer S will be referred to as the front surface Wa, and the surface opposite the front surface Wa will be referred to as the back surface Wb. Similarly, the surface of the second wafer S that is bonded to the first wafer W will be referred to as the front surface Sa, and the surface opposite the front surface Sa will be referred to as the back surface Sb.

[0013] The first wafer W as the first substrate is a semiconductor wafer such as a silicon substrate. In one embodiment, the first wafer W has a substantially circular disk shape. A laminated film in which a plurality of films are stacked is formed on the front surface Wa of the first wafer W. The laminated film includes, in order from the front surface Wa side, a laser absorption layer P, a device layer Dw, and a surface film Fw. The device layer Dw includes a plurality of devices. The surface film Fw may be, for example, an oxide film (THOX film, SiO ２ Examples of the surface film Fw include a silicon dioxide film, a TEOS film, a SiC film, a SiCN film, and an adhesive. The first wafer W is bonded to the second wafer S via this surface film Fw. Note that the device layer Dw and the surface film Fw may not be formed on the surface Wa. In this case, the laser absorption layer P is formed on the second wafer S side, and the device layer Ds on the second wafer S side, which will be described later, is transferred to the first wafer W side.

[0014] The laser absorption layer P absorbs the laser light irradiated from the laser irradiation unit 110, as will be described later. The laser absorption layer P may be formed of, for example, an oxide film (SiO ２ However, there is no particular limitation as long as it absorbs laser light. The laser absorption layer P is formed by a CVD (Chemical Vapor Deposition) process, for example, outside the wafer processing system 1 described later. An oxide film (SiO ２ The composition of the silicon dioxide film (SiO 2 film, TEOS film) can be changed as desired depending on the type and mixture ratio of the processing gas used in the CVD process.

[0015] The second wafer S serving as the second substrate is a semiconductor wafer such as a silicon substrate. A laminated film is formed on the surface Sa of the second wafer S. The laminated film has a device layer Ds and a surface film Fs, in this order, from the surface Sa side. The device layer Ds and the surface film Fs are the same as the device layer Dw and the surface film Fw of the first wafer W, respectively. The surface film Fw of the first wafer W and the surface film Fs of the second wafer S are bonded together. Note that the device layer Ds and the surface film Fs may not be formed on the surface Sa in some cases.

[0016] In the technology of the present disclosure, the laminated film formed at the interface between the first wafer W and the second wafer S, specifically the laser absorption layer P, the device layers Dw, Ds, and the surface films Fw, Fs, may be collectively referred to as the "interface layer." In the technology of the present disclosure, the interface layer includes at least the laser absorption layer P. The type of laminated film formed at the interface between the first wafer W and the second wafer S is not limited to the example shown in FIG. 1 . For example, the laminated film may include a "peeling-promoting film" (described later) for appropriately peeling the first wafer W and the laser absorption layer P. In this case, the above-mentioned interface layer includes the peeling-promoting film.

[0017] 2, the wafer processing system 1 has a configuration in which a load / unload block 10, a transfer block 20, and a processing block 30 are integrally connected. The load / unload block 10 and the processing block 30 are provided around the transfer block 20. Specifically, the load / unload block 10 is disposed on the negative Y-axis side of the transfer block 20. A laser irradiation device 31 (described later) and a separation device 32 (described later) of the processing block 30 are disposed on the negative X-axis side of the transfer block 20, and a first cleaning device 33 (described later) and a second cleaning device 34 (described later) are disposed on the positive X-axis side of the transfer block 20.

[0018] The carry-in / out block 10 carries in and out cassettes Ct, Cw, and Cs, each capable of accommodating a plurality of overlapping wafers T, a plurality of first wafers W, and a plurality of second wafers S, for example, between the outside and the block 10. A cassette mounting table 11 is provided in the carry-in / out block 10. In the illustrated example, a plurality of cassettes Ct, Cw, and Cs, for example, three cassettes Ct, Cw, and Cs, can be mounted on the cassette mounting table 11 in a line in the X-axis direction. The number of cassettes Ct, Cw, and Cs mounted on the cassette mounting table 11 is not limited to that in this embodiment and can be determined arbitrarily.

[0019] The transfer block 20 is provided with a wafer transfer device 22 that is movable on a transfer path 21 extending in the X-axis direction. The wafer transfer device 22 has, for example, two transfer arms 23, 23 that hold and transfer the overlapped wafer T, the first wafer W, or the second wafer S. Each transfer arm 23 is configured to be movable horizontally, vertically, around a horizontal axis, and around a vertical axis. Note that the configuration of the transfer arm 23 is not limited to this embodiment and may have any configuration. The wafer transfer device 22 is configured to transfer the overlapped wafer T, the first wafer W, or the second wafer S to the cassettes Ct, Cw, and Cs on the cassette mounting table 11, the laser irradiation device 31, the separation device 32, the first cleaning device 33, and the second cleaning device 34.

[0020] The processing block 30 has a laser irradiation device 31, a separation device 32, a first cleaning device 33, and a second cleaning device 34. In one example, the laser irradiation device 31 and the separation device 32 are stacked on the negative side of the X-axis of the transport block 20. The first cleaning device 33 and the second cleaning device 34 are stacked on the positive side of the X-axis of the transport block 20. Note that the number and arrangement of the laser irradiation device 31, the separation device 32, the first cleaning device 33, and the second cleaning device 34 are not limited to this.

[0021] The laser irradiation device 31 irradiates laser light onto the inside of the overlapped wafer T, more specifically onto the laser absorption layer P formed on the surface Wa of the first wafer W, thereby reducing the bonding strength at the interface between the first wafer W and the laser absorption layer P.

[0022] 3, a delivery position A1 and a processing position A2 are set inside the laser irradiation device 31. The delivery position A1 is a position where the overlapped wafer T can be delivered from the transfer arm 23 to a chuck 100 (described later) and where an image of the overlapped wafer T (laser absorbing layer P) can be captured by a camera 120 (described later). The processing position A2 is a position where the overlapped wafer T (laser absorbing layer P) can be irradiated with laser light from a laser irradiation unit 110 (described later).

[0023] 3 and 4 , the laser irradiation device 31 has a chuck 100 as a substrate holder that holds the overlapped wafer T on its upper surface. The chuck 100 has a holding surface for the overlapped wafer T on its upper surface, and adsorbs and holds the entire back surface Sb of the second wafer S or a radially inner portion of the back surface Sb. The chuck 100 is, for example, an electrostatic chuck (ESC) or a vacuum chuck. The chuck 100 is provided with lifting pins (not shown) for supporting and elevating the overlapped wafer T from below. The lifting pins are inserted through through-holes (not shown) formed through the chuck 100 and are configured to be able to move up and down.

[0024] The chuck 100 is supported by a slider table 102 via an air bearing 101. A rotation mechanism 103 is provided on the underside of the slider table 102. The rotation mechanism 103 incorporates, for example, a motor as a drive source. The chuck 100 is configured to be rotatable around the θ-axis (vertical axis) via the air bearing 101 by the rotation mechanism 103. The slider table 102 is configured to be movable between the transfer position A1 and the processing position A2 by a movement mechanism 104 provided on the underside of the slider table 102 along rails 106 provided on a base 105 and extending in the Y-axis direction. The drive source of the movement mechanism 104 is not particularly limited, but a linear motor, for example, is used.

[0025] A laser irradiation unit 110 is provided above the chuck 100 at the processing position A2. The laser irradiation unit 110 has a laser head 111, an optical system 112, and a lens 113. The laser irradiation unit 110 can scan a laser beam. In the following description, scanning a laser beam means moving the laser beam irradiated from the lens 113 of the laser irradiation unit 110 relative to the laser absorption layer P.

[0026] The laser head 111 has a laser oscillator (not shown) that oscillates a laser beam in pulses. This laser beam is a so-called pulse laser. In this embodiment, the laser beam is a CO ２ Laser light, CO ２ The wavelength of the laser light is, for example, 8.9 μm to 11 μm. The laser head 111 may also include other devices in addition to the laser oscillator, such as an amplifier.

[0027] The optical system 112 includes an optical element (not shown) that controls the intensity and position of the laser light, an attenuator (not shown) that attenuates the laser light to adjust its output, and a laser scanning unit (not shown) that scans the laser light. The laser scanning unit may be, for example, a rotary wedge scanner or a galvano scanner. The optical system 112 may also be configured to be able to control the branching of the laser light.

[0028] The lens 113 irradiates the laser light onto the laminated wafer T held by the chuck 100. The laser light emitted from the laser irradiation unit 110 passes through the first wafer W and is irradiated onto the laser absorption layer P. The lens 113 may be configured to be movable in the horizontal direction by a movement mechanism (not shown), or may be configured to be movable up and down in the vertical direction by a lifting mechanism (not shown).

[0029] Furthermore, a camera 120 is provided above the chuck 100 at the transfer position A1. The camera 120 has one or more cameras selected from a macro camera, a micro camera, etc. The camera 120 may be configured to be movable in the horizontal direction by a moving mechanism (not shown), or may be configured to be movable up and down in the vertical direction by a lifting mechanism (not shown).

[0030] The camera 120 captures an image of the laminated wafer T held by the chuck 100. The camera 120 includes, for example, a coaxial lens, irradiates infrared light (IR), and receives reflected light from an object. Image data captured by the camera 120 is output to the control device 40, which will be described later.

[0031] As will be described later, the wafer processing system 1 includes a control device 40 , which is provided in the laser irradiation device 31 and also functions as a control unit for controlling the laser irradiation device 31 .

[0032] The separation device 32 as a separation section peels the first wafer W from the second wafer S (overlapped wafer T) using the interface between the first wafer W and the laser absorption layer P as the peeled portion, where the bonding strength has been reduced by the laser irradiation device 31, as a base point.

[0033] 5, the separation device 32 has a suction chuck 200 that suction-holds the back surface Sb of the second wafer S from below, and a suction pad 210 that suction-holds the back surface Wb of the first wafer W from above. In the separation device 32, the suction chuck 200 suction-holds the second wafer S, and the suction pad 210 suction-holds the first wafer W, as shown in FIG. 5, the suction pad 210 is raised to peel off the first wafer W from the laser absorption layer P.

[0034] The configuration of the separating device 32 is not limited to this, and any configuration may be used as long as the first wafer W can be separated from the second wafer S.

[0035] The first cleaning device 33 cleans the front surface Sa side of the second wafer S separated by peeling in the separating device 32. For example, a brush is brought into contact with the laser absorbing layer P on the front surface Sa side of the second wafer S to clean the laser absorbing layer P. Note that a pressurized cleaning liquid may be used to clean the second wafer S. Furthermore, the first cleaning device 33 may be configured to clean the back surface Sb of the second wafer S as well as the front surface Sa side.

[0036] The second cleaning device 34 cleans the front surface Wa of the first wafer W separated by peeling in the separation device 32. For example, a brush is brought into contact with the front surface Wa of the first wafer W to clean the front surface Wa. Note that a pressurized cleaning liquid may be used to clean the first wafer W. The second cleaning device 34 may also be configured to clean the back surface Wb of the first wafer W as well as the front surface Wa.

[0037] In this embodiment, as described above, the first cleaning apparatus 33 for cleaning the second wafer S and the second cleaning apparatus 34 for cleaning the first wafer W are disposed independently, but the cleaning of the first wafer W and the cleaning of the second wafer S may be performed using the same cleaning apparatus. In this case, the cleaning of the first wafer W and the second wafer S may be performed simultaneously or independently.

[0038] Furthermore, in this embodiment, the first wafer W is separated from the second wafer S using the separation device 32, but such separation may also be performed inside the laser irradiation device 31. For example, a liftable transfer pad (not shown) is provided at the transfer position A1 of the laser irradiation device 31. Then, while the chuck 100 is holding the second wafer S by suction, the transfer pad holds the first wafer W by suction, and the transfer pad is then raised, thereby separating the first wafer W from the second wafer S.

[0039] The wafer processing system 1 described above is provided with a control device 40 as a control unit. The control device 40 is, for example, a computer, and has a program storage unit (not shown). The program storage unit stores a program for controlling the processing of the laminated wafer T in the wafer processing system 1. The program storage unit also stores a program for controlling the operation of the drive systems of the various processing devices and transport devices described above to realize the wafer processing described below in the wafer processing system 1. The program may be recorded on a computer-readable storage medium H and installed into the control device 40 from the storage medium H. The storage medium H may be temporary or non-temporary.

[0040] Next, a description will be given of wafer processing performed using the thus configured wafer processing system 1. In this embodiment, the first wafer W and the second wafer S are bonded together in a bonding device (not shown) external to the wafer processing system 1 to form an overlapped wafer T in advance.

[0041] First, a cassette Ct containing a plurality of overlapping wafers T is placed on the cassette placement table 11 of the carry-in / out block 10 .

[0042] Next, the overlapped wafer T is removed from the cassette Ct by the wafer transfer device 22 and transferred to the laser irradiation device 31. In the laser irradiation device 31, the overlapped wafer T is transferred from the transfer arm 23 to the chuck 100 arranged at the transfer position A1, and the back surface Sb of the second wafer S is attracted and held by the chuck 100. Next, the moving mechanism 104 moves the chuck 100 to the processing position A2.

[0043] Next, as shown in FIG. 6, the laser irradiation unit 110 focuses on the laser absorption layer P, more specifically, on the interface between the first wafer W and the laser absorption layer P, and irradiates the laser beam L(CO ２ The first wafer W is irradiated with pulsed laser light (laser light). At this time, the laser light L passes through the first wafer W from the rear surface Wb side of the first wafer W and is absorbed in the laser absorbing layer P. The laser light L reduces the bonding strength between the first wafer W and the laser absorbing layer P. In the embodiment, "reduced bonding strength" refers to a state in which the bonding strength is reduced compared to at least that before the irradiation of the laser light L, and includes peeling between the first wafer W and the laser absorbing layer P. The mechanism by which the bonding strength between the first wafer W and the laser absorbing layer P is reduced by the irradiation of the laser light L will be described in detail later.

[0044] When irradiating the laser absorbing layer P with the laser light L at the processing position A2, first, an image of the overlapped wafer T (first wafer W) is taken by the camera 120. Image data taken by the camera 120 is output to the control device 40. The control device 40 determines the irradiation start position of the laser absorbing layer P with the laser light L based on the image data.

[0045] Subsequently, at the processing position A2, the laser irradiation unit 110 irradiates the entire surface of the laser absorbing layer P in plan view with laser light L at desired intervals, thereby reducing the bonding strength over the entire surface of the interface between the first wafer W and the laser absorbing layer P. The method of irradiating the laser light L onto the laser absorbing layer P will be described in detail later.

[0046] After the laser light L is irradiated onto the entire surface of the laser absorption layer P and the bonding strength between the first wafer W and the entire surface of the laser absorption layer P is reduced, the chuck 100 (superimposed wafer T) is then moved to the transfer position A1 by the moving mechanism 104.

[0047] Next, the laminated wafer T on the chuck 100 is transferred to the transfer arm 23 of the wafer transfer device 22 and transferred to the separation device 32. In the separation device 32, as shown in FIG. 5( a), the suction chuck 200 suction-holds the back surface Sb of the second wafer S, and the suction pad 210 suction-holds the back surface Wb of the first wafer W. Thereafter, as shown in FIG. 5( b), while the suction pad 210 suction-holds the first wafer W, the suction pad 210 is raised to peel the first wafer W from the laser absorbing layer P. At this time, since the bonding strength at the interface between the first wafer W and the laser absorbing layer P has been reduced by the irradiation of the laser light L as described above, the first wafer W can be separated from the laser absorbing layer P without applying a large load.

[0048] The separated first wafer W is transferred from the suction pad 210 to the transfer arm 23 of the wafer transfer device 22 and transferred to the second cleaning device 34. At this time, the first wafer W transferred from the separation device 32 may be reversed upside down by the operation of, for example, an inverting device (not shown) or the suction pad 210 so that the front surface Wa faces upward, and then transferred to the second cleaning device 34.

[0049] In the second cleaning device 34, the front surface Wa of the first wafer W, which is the surface separated by the separation device 32, is cleaned. Note that in the second cleaning device 34, the back surface Wb may also be cleaned in addition to the front surface Wa. Alternatively, separate cleaning units may be provided for cleaning the front surface Wa and the back surface Wb, respectively. Thereafter, the first wafer W cleaned by the second cleaning device 34 is transferred to the cassette Cw on the cassette mounting table 11 by the wafer transfer device 22.

[0050] On the other hand, the second wafer S held by the suction chuck 200 is transferred to the transfer arm 23 and transferred to the first cleaning device 33. In the first cleaning device 33, the front surface Sa of the second wafer S, which is the surface separated by the separating device 32, specifically the front surface of the laser absorbing layer P, is cleaned. Note that in the first cleaning device 33, the back surface Sb of the second wafer S may be cleaned in addition to the front surface of the laser absorbing layer P. Furthermore, separate cleaning units may be provided for cleaning the front surface of the laser absorbing layer P and the back surface Sb of the second wafer S, respectively. Thereafter, the second wafer S cleaned by the first cleaning device 33 is transferred to the cassette Cs of the cassette mounting table 11 by the wafer transfer device 22.

[0051] Thus, a series of wafer processing steps in the wafer processing system 1 is completed.

[0052] Next, the mechanism of the reduction in the bonding strength between the first wafer W and the laser absorption layer P caused by the irradiation of the laser light L at the processing position A2 of the laser irradiation device 31 will be described in detail.

[0053] As described above, at the processing position A2 of the laser irradiation device 31, the overlapped wafer T held by the chuck 100 is irradiated with the laser light L from the back surface Wb side of the first wafer W (step St11 in FIG. 7 ). The laser light L output from the lens 113 of the laser irradiation unit 110 passes through silicon (first wafer W) and is absorbed by the laser absorption layer P (step St12 in FIG. 7 ), as shown in FIG.

[0054] The laser light L absorbed by the laser absorbing layer P is converted into heat in accordance with its energy distribution (step St13 in FIG. 7 ). In other words, the absorption of the laser light L causes the temperature of the laser absorbing layer P to rise. The temperature of the laser absorbing layer P is highest in the region directly under the irradiation of the laser light L. Most of the heat (Ht in the figure) generated in the laser absorbing layer P by the absorption of the laser light L diffuses toward the first wafer W, as shown in FIG. 8 (step St14 in FIG. 7 ). In other words, the temperature of the interface between the laser absorbing layer P and the first wafer W (silicon) rises due to thermal diffusion from the laser absorbing layer P.

[0055] When the heat generated in the laser absorbing layer P diffuses toward the first wafer W, the effect of this heat, i.e., an increase in the temperature at the interface between the laser absorbing layer P and the first wafer W, causes the first wafer W to locally expand in the portion irradiated with the laser light L in accordance with the temperature distribution (plastically deformed downward into a convex shape with respect to the laser absorbing layer P side) as shown in FIG. 9 (step St15 in FIG. 7 ). Hereinafter, the region affected by the heat generated by irradiation with the laser light L may be referred to as the "irradiation region R" of the laser light L. In other words, the first wafer W locally expands in the irradiated region R of the laser light L.

[0056] Here, when the first wafer W expands, the laser absorbing layer P is pressed from above (the first wafer W side) in accordance with the expansion of the first wafer W, and as a result, a compressive stress σ1 is generated in the laser absorbing layer P at the irradiation position of the laser light L, as shown in FIG. 9 . The generated compressive stress σ1 acts in a direction that peels the first wafer W and the laser absorbing layer P (the downward direction in the figure, toward the laser absorbing layer P) to generate a peeling stress σ2, as shown in FIG. 9 . In other words, in the irradiation region R of the laser light L, the silicon (first wafer W) expands in the region directly below the irradiation of the laser light L (the central part of the irradiation region R), generating a compressive stress σ1, and at the same time, a peeling stress σ2, which is a stress in the peeling direction due to the compressive stress σ1, is generated at the end Re of the irradiation region R (see FIG. 9 ). This peeling stress σ2 is a tensile stress generated at the end Re of the irradiation region R.

[0057] The generated compressive stress σ1 and peeling stress σ2 are accumulated inside the laser absorption layer P. At this time, at the end Re of the irradiation region R, the peeling stresses σ2 generated in the multiple irradiation regions R act synergistically (overlappedly).

[0058] Then, when the total accumulated amount (synergistic amount) of peeling stress σ2 at the end Re of the irradiation region R exceeds the adhesion force Σ between the first wafer W and the laser absorption layer P per unit area at the end Re (n × σ2 > Σ (where n is a natural number and is the number of irradiations of laser light L)), peeling occurs at the interface between the first wafer W and the laser absorption layer P at the end Re of the irradiation region R as shown in FIG. 10, and as a result, the bonding strength between the laser absorption layer P and the first wafer W decreases (step St16 in FIG. 7).

[0059] The stress σ (compressive stress σ1 and peeling stress σ2) accumulated inside the laser absorption layer P is released by the peeling of the first wafer W and the laser absorption layer P.

[0060] 11 , at the processing position A2 of the laser irradiation device 31, by causing delamination across the entire surface of the interface between the first wafer W and the laser absorbing layer P in a plan view, in other words, by connecting the delamination that occurred at the end Re of the irradiation region R across the entire surface of the interface between the first wafer W and the laser absorbing layer P, the bonding strength between the first wafer W and the laser absorbing layer P is reduced across the entire surface, and thus the first wafer W and the laser absorbing layer P can be appropriately separated in the separation device 32 (step St17 in FIG. 7 ). Note that, in the laminated wafer T after being irradiated with the laser light L at the processing position A2, ideally, delamination from the laser absorbing layer P occurs across the entire surface of the first wafer W, in other words, after delamination occurs at the end Re of the irradiation region R, the first wafer W and the laser absorbing layer P are delaminated also in the central part of the irradiation region R including the region directly below the irradiation due to the delamination stress σ2. 10 , however, in the central part of the irradiation region R (the region directly under the irradiation of the laser light L), the first wafer W and the laser absorbing layer P may remain connected (not peeled) even after peeling occurs at the end part Re of the irradiation region R. For this reason, in the wafer processing system 1 according to the technique of the present disclosure, in order to reliably separate the first wafer W from the overlapped wafer T (laser absorbing layer P) in the overlapped wafer T after being irradiated with the laser light L, it is preferable to provide a separation device 32 and to provide a step of separating the first wafer W from the overlapped wafer T in the separation device 32.

[0061] Here, when the separation of the first wafer W from the overlapped wafer T is performed in the separating device 32 in this manner, if the overlapped wafer T is transported to the separating device 32 in the ideal state described above, i.e., in a state in which peeling from the laser absorbing layer P occurs over the entire surface of the first wafer W, there is a risk that the first wafer W will fall off the second wafer S due to inertial force or the like associated with this transport. Furthermore, if peeling from the laser absorbing layer P occurs over the entire surface of the first wafer W in this manner, even if there is no need to transport the overlapped wafer T after irradiation with the laser light L to the separating device 32, there is a risk that the first wafer W will fly off the second wafer S due to centrifugal force or the like associated with the rotation of the chuck 100 during the irradiation of the laser light L to the laser absorbing layer P at the processing position A2.

[0062] In view of this, in order to prevent the first wafer W from scattering or falling during irradiation of the laser light L onto the laser absorbing layer P and during transport of the laminated wafer T, it is preferable to control the irradiation conditions (irradiation position, output, etc.) of the laser light L at the processing position A2 so that at least a part of the interface between the first wafer W and the laser absorbing layer P remains connected (is not peeled off). This allows the first wafer W to be completely separated from the laser absorbing layer P during irradiation of the laser light L, transport to the separating device 32, etc., and prevents the first wafer W from scattering or falling from the second wafer S.

[0063] The reduction in the bonding strength between the first wafer W and the laser absorbing layer P at the processing position A2 of the laser irradiation device 31 is performed as described above. That is, in the laser irradiation device 31 in this embodiment, the first wafer W is expanded by heat generated by irradiation with the laser light L, and a compressive stress σ1 is generated in the laser absorbing layer P, thereby generating a peel stress σ2 in the peel direction at the interface between the first wafer W and the laser absorbing layer P, which causes peeling at the interface between the first wafer W and the laser absorbing layer P and reduces the bonding strength.

[0064] 9 , the laser absorbing layer P is irradiated with the laser light L multiple times, and when the total accumulated amount of the peel stress σ2 generated thereby exceeds the adhesion force Σ between the first wafer W and the laser absorbing layer P, peeling occurs at the end Re of the irradiated region R, but the number of times of irradiation with the laser light L until such peeling occurs is not limited to multiple times. For example, when the peel stress σ2 generated by a single irradiation (one time) of the laser light L exceeds the adhesion force Σ of the end Re, peeling may occur at the interface between the first wafer W and the laser absorbing layer P at the end Re of the irradiated region R by the irradiation of the single laser light L.

[0065] Next, a method for irradiating the laser absorption layer P with the laser light L at the processing position A2 of the laser irradiation device 31 will be described in detail.

[0066] First, as shown in FIG. 13 , the regions of the overlapped wafer T (laser absorption layer P) in a planar view are set as an outer peripheral region Z0, a first inner peripheral region Z1, a second inner peripheral region Z2, and a central region Z3 (step St20 in FIG. 12 ). Specifically, for example, an operator sets the outer peripheral region Z0, the first inner peripheral region Z1, the second inner peripheral region Z2, and the central region Z3, and these outer peripheral region Z0, the first inner peripheral region Z1, the second inner peripheral region Z2, and the central region Z3 are stored in the control device 40. The outer peripheral region Z0, the first inner peripheral region Z1, the second inner peripheral region Z2, and the central region Z3 are arranged in this order from the outside to the inside in the radial direction. Furthermore, the outer peripheral region Z0, the first inner peripheral region Z1, and the second inner peripheral region Z2 are arranged in a concentric ring shape with the overlapped wafer T, and the central region Z3 is arranged in a concentric circle shape with the overlapped wafer T.

[0067] 13 and 14 , the outer peripheral region Z0 is a peripheral region of the overlapped wafer T, and includes an unbonded region Q where the first wafer W (surface film Fw) and the second wafer S (surface film Fs) are not bonded, and a bonded region B radially inward of the unbonded region Q. The unbonded region Q includes a chamfered portion (bevel portion) where the peripheral edge is chamfered. The unbonded region Q also includes a region where the first wafer W and the second wafer S are not bonded due to, for example, misalignment of the bonding position or other factors.

[0068] The first inner peripheral region Z1, the second inner peripheral region Z2, and the central region Z3 are regions disposed in the bonding region B of the first wafer W and the second wafer S, respectively.

[0069] In this embodiment, the overlapped wafer T is rotated and the laser light L is moved in the radial direction while the laser light L is irradiated in pulses. At this time, in order to uniformly peel the first wafer W and the laser absorption layer P across the wafer surface, it is preferable to keep the interval at which the laser light L is irradiated, i.e., the pulse interval, constant. To keep the irradiation interval of the laser light L constant, for example, the rotation speed of the overlapped wafer T is increased as the laser light L moves from the outer side to the inner side in the radial direction. Furthermore, when the rotation speed of the overlapped wafer T reaches its upper limit, the frequency of the laser light L when irradiating the laser light L in pulses is decreased, for example, as the laser light L moves from the outer side to the inner side in the radial direction. When the rotation speed of the overlapped wafer T reaches its upper limit and the frequency of the laser light reaches its lower limit, for example, the irradiation interval of the laser light decreases as the laser light L moves from the outer side to the inner side in the radial direction, and the laser light L may overlap in the central region of the overlapped wafer T.

[0070] Therefore, in this embodiment, the overlapped wafer T is rotated while being irradiated with the laser light L in the outer peripheral region Z0, the first inner peripheral region Z1, and the second inner peripheral region Z2. Meanwhile, the laser light L is scanned in the central region Z3 while the rotation of the overlapped wafer T is stopped.

[0071] In the outer peripheral region Z0 and the first inner peripheral region Z1, the frequency of the laser light L is kept constant, and the rotation speed of the overlapped wafer T is varied in accordance with the radial movement of the laser light L, thereby irradiating the laser light L in pulses. Specifically, the rotation speed of the overlapped wafer T is increased when the laser light L moves from the outer side to the inner side in the radial direction, and the rotation speed of the overlapped wafer T is decreased when the laser light L moves from the inner side to the outer side in the radial direction.

[0072] In the second inner peripheral region Z2, the rotation speed of the overlapped wafer T is kept constant, and the frequency of the laser light L is varied in accordance with the radial movement of the laser light L to irradiate the laser light L in pulses. Specifically, the frequency of the laser light L is decreased when the laser light L moves from the outer side to the inner side in the radial direction, and the frequency of the laser light L is increased when the laser light L moves from the inner side to the outer side in the radial direction.

[0073] The boundary position between the first inner peripheral region Z1 and the second inner peripheral region Z2 is set at a position where the rotation speed of the overlapped wafer T reaches an upper limit, and the boundary position between the second inner peripheral region Z2 and the central region Z3 is set at a position where the frequency of the laser light L reaches a lower limit.

[0074] Next, the laser absorption layer P is irradiated with laser light L. At this time, the processing conditions of the laser processing are changed for each of the regions Z0 to Z3. In this embodiment, irradiation of the outer circumferential region Z0 with laser light L (step St21 in FIG. 12), irradiation of the second inner circumferential region Z2 with laser light L (step St22 in FIG. 12), irradiation of the first inner circumferential region Z1 with laser light L (step St23 in FIG. 12), and irradiation of the central region Z3 with laser light L (step St24 in FIG. 12) are performed in this order.

[0075] In step St21, in the outer peripheral region Z0, as shown in FIG. 15 , the chuck 100 (the overlapped wafer T held by the chuck 100) is rotated counterclockwise by the rotation mechanism 103, and the chuck 100 is moved in the positive direction of the Y axis by the movement mechanism 104, while the laser light L is irradiated in pulses. At this time, the laser light L is fixed without being scanned. As a result, in the outer peripheral region Z0, the laser light L is irradiated in a spiral pattern from the inside to the outside in the radial direction. Furthermore, due to the peeling mechanism of the first wafer W and the laser absorption layer P caused by the irradiation of the laser light L described above, peeling occurs at the interface between the first wafer W and the laser absorption layer P in the outer peripheral region Z0, as shown in FIG. 16 .

[0076] Since the outer peripheral region Z0 includes the unbonded region Q, the bonding strength between the first wafer W and the second wafer S, i.e., the bonding strength between the surface film Fw and the surface film Fs, is low at the boundary between the unbonded region Q and the bonding region B. In such a case, when the outer peripheral region Z0 is irradiated with laser light L, as shown in FIG. 17 , peeling does not occur between the first wafer W and the laser absorbing layer P in the outer peripheral region Z0 unless the peel stress σ2 exceeds the adhesion force Σ between the first wafer W and the laser absorbing layer P. The convex shape of the interface between the first wafer W and the laser absorbing layer P is transmitted to the surface film Fw, and stress acts on the interface between the surface film Fw and the surface film Fs. This stress may cause peeling at the interface between the surface film Fw and the surface film Fs, where the bonding strength is low, at the boundary between the unbonded region Q and the bonding region B. In this state, when the laser beam L is irradiated by moving it from the radially outer side to the radially inner side in the outer peripheral region Z0, peeling tends to progress from the interface between the peeled surface film Fw and the surface film Fs as the leading edge in the bonding region B adjacent to the radially inner side of the unbonded region Q. That is, in the bonding region B of the outer peripheral region Z0, peeling may not occur at the desired interface between the first wafer W and the laser absorption layer P.

[0077] Therefore, in this embodiment, the laser light L is irradiated from the radially inner side to the radially outer side in the outer peripheral region Z0. As a result, as shown in FIG. 16 , peeling E1 occurs at the interface between the first wafer W and the laser absorption layer P in the bonding region B. At this time, stress σ is generated in each irradiation region R so that peeling E1 occurs from the center to the edge Re. To generate such a large stress σ, for example, the frequency of the laser light L may be increased (the pitch of the laser light L may be shortened) or the irradiation intensity of the laser light L may be increased. Furthermore, at the boundary between the bonding region B and the unbonded region Q, the bonding strength at the interface between the surface film Fw and the surface film Fs is low, so peeling E2 occurs extending from the interface between the first wafer W and the laser absorption layer P toward the interface between the surface film Fw and the surface film Fs. Even if peeling E2 occurs, there is no impact on the device layer Dw radially outside of the peeling E2 because it is a device that will not be commercialized.

[0078] Next, in step St22, in the second inner peripheral region Z2, as shown in FIG. 18 , the chuck 100 is rotated counterclockwise by the rotation mechanism 103, and the chuck 100 is moved in the positive direction of the Y axis by the movement mechanism 104, while the laser light L is irradiated in pulses. At this time, the laser light L is fixed without scanning. As a result, in the second inner peripheral region Z2, the laser light L is irradiated in a spiral pattern from the inside to the outside in the radial direction. Furthermore, in the second inner peripheral region Z2, peeling occurs at the interface between the first wafer W and the laser absorption layer P, as shown in FIG.

[0079] Next, in step St23, the first inner peripheral region Z1 is irradiated with the laser light L, and the second inner peripheral region Z2 is irradiated with the laser light L in succession in step St22, as shown in Fig. 18. That is, the laser light L is irradiated in pulses while the chuck 100 is rotated counterclockwise by the rotation mechanism 103 and moved in the positive direction of the Y axis by the movement mechanism 104. At this time, the laser light L is fixed without scanning.

[0080] Then, in step St23, the laser light L is irradiated in a spiral shape from the radially inner side to the radially outer side in the first inner circumferential region Z1. The spiral shape of the laser light L in the first inner circumferential region Z1 is continuous with the spiral shape of the laser light L in the second inner circumferential region Z2 and the spiral shape of the laser light L in the outer circumferential region Z0. That is, in the outer circumferential region Z0, the first inner circumferential region Z1, and the second inner circumferential region Z2, the rotation direction of the chuck 100 is the same counterclockwise, and the irradiation direction (movement direction) of the laser light L is the same from the radially inner side to the radially outer side, so the spiral shape of the laser light L is continuous.

[0081] 19, in step St23, peeling occurs at the interface between the first wafer W and the laser absorption layer P in the first inner peripheral region Z1. This peeling at the interface between the first wafer W and the laser absorption layer P in the first inner peripheral region Z1 continues to peeling at the interface between the first wafer W and the laser absorption layer P in the second inner peripheral region Z2 and to peeling at the interface in the outer peripheral region Z0.

[0082] In the second inner peripheral region Z2 of step St22 and the first inner peripheral region Z1 of step St23, in each irradiation region R, the first wafer W and the laser absorption layer P are peeled off or the bonding strength is weak at the edge Re, and the first wafer W and the laser absorption layer P are connected at the center. That is, compared to the outer peripheral region Z0, the stress σ accumulated inside the laser absorption layer P is smaller in the second inner peripheral region Z2 and the first inner peripheral region Z1. To generate such a small stress σ, for example, the frequency of the laser light L may be reduced (the pitch of the laser light L may be increased) or the irradiation intensity of the laser light L may be reduced. Increasing the pitch of the laser light L shortens the time required for laser processing, thereby improving throughput. Furthermore, reducing the irradiation intensity of the laser light L allows for more efficient laser processing.

[0083] Here, if a large stress σ is generated in the second inner peripheral region Z2 and the first inner peripheral region Z1 such that the interface between the first wafer W and the laser absorption layer P completely peels off, and if this stress σ accumulates, there is a risk of cracking the first wafer W. Therefore, as described above, in the second inner peripheral region Z2 and the first inner peripheral region Z1, peeling occurs while at least a portion of the interface between the first wafer W and the laser absorption layer P remains connected, thereby suppressing cracking of the first wafer W.

[0084] 19 , when peeling E3 at the interface between the first wafer W and the laser absorption layer P in the first inner peripheral region Z1 connects to peeling E1 in the outer peripheral region Z0, the entire interface between the first wafer W and the laser absorption layer P is peeled off in the first inner peripheral region Z1 and the second inner peripheral region Z2. Note that the above-mentioned "weak bonding strength between the first wafer W and the laser absorption layer P at the edge Re" refers to a bonding strength that is strong enough to cause peeling at the edge Re when peeling E3 at the interface between the first wafer W and the laser absorption layer P in the first inner peripheral region Z1 connects to peeling E1 in the outer peripheral region Z0.

[0085] Next, in step St24, the rotation of the chuck 100 is stopped in the central region Z3. Then, pulsed laser light L is emitted from the laser irradiation unit 110. The central region Z3 is scanned with the laser light L. At this time, as shown in FIG. 20 , scanning irradiation of the laser light L in the X-axis direction and movement of the chuck 100 (superimposed wafer T) in the Y-axis direction are alternately repeated. Alternatively, scanning irradiation of the laser light L in the X-axis direction and movement of the chuck 100 in the negative Y-axis direction may be synchronized. To improve the throughput of wafer processing, the laser light L may be branched by the optical system 112, and multiple points on the laser absorbing layer P may be simultaneously irradiated with the laser light L. Furthermore, due to the peeling mechanism between the first wafer W and the laser absorbing layer P caused by the irradiation of the laser light L, peeling occurs at the interface between the first wafer W and the laser absorbing layer P in the central region Z3.

[0086] According to this embodiment, by performing steps St20 to St24, it is possible to cause delamination at the interface between the first wafer W and the laser absorption layer P. As a result, the first wafer W and the laser absorption layer P can be separated, and the device layer Dw of the first wafer W can be transferred to the second wafer S.

[0087] Furthermore, in step St21, in the outer peripheral region Z0, the laser light L is irradiated by moving from the inside to the outside in the radial direction, so that delamination can occur at the interface between the first wafer W and the laser absorbing layer P. This can reduce the bonding strength at the interface between the first wafer W and the laser absorbing layer P, and the first wafer W and the laser absorbing layer P can be delaminated.

[0088] Furthermore, in the second inner peripheral region Z2 of step St22 and the first inner peripheral region Z1 of step St23, the laser light L is continuously irradiated from the radial inside to the outside, so that the peeling at the interface between the first wafer W and the laser absorption layer P can be properly continued.

[0089] As described above, in consideration of appropriately transporting the overlapped wafer T after irradiation with the laser light L in the laser irradiation device 31, it is preferable that at least a part of the interface between the first wafer W and the laser absorption layer P remains connected. Therefore, it is preferable to maintain the connected state of at least a part of the interface between the first wafer W and the laser absorption layer P in at least one of the first inner peripheral region Z1, the second inner peripheral region Z2, and the central region Z3.

[0090] In order to obtain the effects of the above embodiment, that is, to delaminate the interface between the first wafer W and the laser absorption layer P at least in the outer peripheral region Z0, it is sufficient to irradiate the outer peripheral region Z0 with the laser light L from the inside to the outside in the radial direction. Other processing conditions are not limited to those in the above embodiment.

[0091] Specifically, the processing conditions for the laser processing can be changed arbitrarily for each of the zones Z0 to Z3, such as the rotation speed of the chuck 100, the frequency of the laser light L, the rotation direction of the chuck 100, and the processing order of the zones Z0 to Z3 (the order of irradiation with the laser light L).

[0092] For example, as shown in FIG. 21, irradiation of the laser light L onto the second inner peripheral region Z2, irradiation of the laser light L onto the first inner peripheral region Z1, irradiation of the laser light L onto the outer peripheral region Z0, and irradiation of the laser light L onto the central region Z3 may be performed in this order.

[0093] In such a case, as shown in FIG. 21(a), in the second inner peripheral region Z2 and the first inner peripheral region Z1, as in steps St22 and St23, the chuck 100 is rotated counterclockwise by the rotation mechanism 103 and the chuck 100 is moved in the positive direction of the Y axis by the movement mechanism 104, while the laser light L is irradiated in pulses.

[0094] In the second inner peripheral region Z2 and the first inner peripheral region Z1, in each irradiation region R, the first wafer W and the laser absorption layer P are separated or the bonding strength is weak at the edge Re, and the first wafer W and the laser absorption layer P are connected at the center. That is, in the second inner peripheral region Z2 and the first inner peripheral region Z1, the stress σ accumulated inside the laser absorption layer P is reduced. If a large stress σ is generated and accumulated as described above, the first wafer W may crack. In this regard, by reducing the stress σ as in this embodiment, cracking of the first wafer W can be suppressed. Note that the above-mentioned "weak bonding strength between the first wafer W and the laser absorption layer P at the edge Re" refers to a bonding strength that is strong enough to cause separation of the edge Re when the separation E3 at the interface between the first wafer W and the laser absorption layer P in the first inner peripheral region Z1 connects to the separation E1 in the outer peripheral region Z0.

[0095] 21B, in the outer peripheral region Z0, as in step St21, the chuck 100 is rotated counterclockwise by the rotation mechanism 103 and the chuck 100 is moved in the positive direction of the Y axis by the movement mechanism 104, while the laser light L is irradiated in pulses. In the outer peripheral region Z0, a large stress σ is generated in each irradiation region R so that peeling E1 occurs from the center to the end portions Re.

[0096] Next, in the central region Z3, similarly to step St24, the laser light L is scanned while the rotation of the chuck 100 is stopped. Then, in the central region Z3, peeling occurs at the interface between the first wafer W and the laser absorption layer P.

[0097] In this embodiment, the same effect as in the above embodiment can be obtained. That is, peeling can be caused at the interface between the first wafer W and the laser absorption layer P.

[0098] 22, the laser beam L may be irradiated to the first inner circumferential region Z1 and the second inner circumferential region Z2 while moving from the outer side to the inner side in the radial direction. In this case, the laser beam L is irradiated to the outer circumferential region Z0, the first inner circumferential region Z1, the second inner circumferential region Z2, and the central region Z3 in this order.

[0099] 22A, in the outer peripheral region Z0, as in step St21, the chuck 100 is rotated counterclockwise by the rotation mechanism 103 and the chuck 100 is moved in the positive direction of the Y axis by the movement mechanism 104 while the laser light L is irradiated in pulses. As a result, the laser light L is irradiated in a spiral pattern from the inside to the outside in the radial direction in the outer peripheral region Z0. In the outer peripheral region Z0, a large stress σ is generated in each irradiation region R so that peeling E1 occurs from the center to the end Re.

[0100] 22(b), in the first inner peripheral region Z1, the chuck 100 is rotated clockwise by the rotation mechanism 103 and moved in the negative direction of the Y axis by the movement mechanism 104, while the laser light L is irradiated in a pulsed manner. As a result, the laser light L is irradiated in a spiral pattern from the radially outer side toward the inner side in the first inner peripheral region Z1.

[0101] In this case, the rotation direction of the chuck 100 is opposite in the adjacent outer peripheral region Z0 and the first inner peripheral region Z1, and the irradiation direction of the laser light L is also opposite. In this way, the spiral shape of the laser light L can be made continuous in the outer peripheral region Z0 and the first inner peripheral region Z1. In other words, when the irradiation directions of the laser light L differ in adjacent regions, the spiral shape of the laser light L can be made continuous by reversing the rotation direction of the chuck 100 in the adjacent regions.

[0102] Next, in the second inner peripheral region Z2, the chuck 100 is rotated clockwise by the rotation mechanism 103 and moved in the negative direction of the Y axis by the movement mechanism 104, while the laser light L is irradiated in a pulsed manner. As a result, the laser light L is irradiated in a spiral pattern from the radially outer side toward the inner side in the second inner peripheral region Z2.

[0103] Note that there is no limitation on the magnitude of the stress σ accumulated inside the laser absorption layer P in the first inner peripheral region Z1 and the second inner peripheral region Z2. When the first inner peripheral region Z1 is irradiated with laser light L, peeling at the interface between the first wafer W and the laser absorption layer P due to the laser light L leads to peeling E1 in the outer peripheral region Z0. Therefore, in the first inner peripheral region Z1, peeling occurs appropriately at the interface between the first wafer W and the laser absorption layer P. Then, this peeling is transmitted to the second inner peripheral region Z2, and peeling also occurs appropriately at the interface between the first wafer W and the laser absorption layer P in the second inner peripheral region Z2.

[0104] Next, in the central region Z3, similarly to step St24, the laser light L is scanned while the rotation of the chuck 100 is stopped. Then, in the central region Z3, peeling occurs at the interface between the first wafer W and the laser absorption layer P.

[0105] In this embodiment, the same effect as in the above embodiment can be obtained. That is, peeling can be caused at the interface between the first wafer W and the laser absorption layer P.

[0106] In the above embodiment, in step St20, two inner peripheral regions, a first inner peripheral region Z1 and a second inner peripheral region Z2, are set. However, there may be only one inner peripheral region. In this inner peripheral region, the frequency of the laser light L may be kept constant, while the rotation speed of the overlapped wafer T may be varied in accordance with the radial movement of the laser light L, to irradiate the laser light L in pulses. Alternatively, the rotation speed of the overlapped wafer T may be kept constant, while the frequency of the laser light L may be varied in accordance with the radial movement of the laser light L, to irradiate the laser light L in pulses. In either case, the processing conditions are controlled so that the irradiation interval of the laser light L is constant in the inner peripheral region.

[0107] In the above embodiment, the chuck 100 is moved horizontally when performing the laser processing, but the lens 113 of the laser irradiation unit 110 may be moved horizontally, or both the chuck 100 and the lens 113 may be moved horizontally. By moving the chuck 100 and the lens 113 relatively in the horizontal direction, the laser processing using the laser light L can be performed.

[0108] In the above embodiment, in step St24, the laser beam L is scanned and irradiated onto the central region Z3 while the rotation of the chuck 100 is stopped, but as shown in Fig. 23, the laser beam L may be scanned and irradiated from the laser irradiation unit 110 while the chuck 100 is rotating. In this case, the rotation speed of the chuck 100 may be lower in the central region Z3 than in the outer circumferential region Z0, the first inner circumferential region Z1, and the second inner circumferential region Z2.

[0109] In the above-described embodiment, the laser beam L is irradiated in a spiral pattern in the outer peripheral region Z0, the first inner peripheral region Z1, and the second inner peripheral region Z2, but it may be irradiated in a concentric ring pattern. Also, in the embodiment shown in FIG. 23, the laser beam L is irradiated in a spiral pattern in the central region Z3, but it may be irradiated in a concentric ring pattern.

[0110] 8 to 11, delamination occurs at the interface between the first wafer W and the laser absorbing layer P. However, as described above, a delamination-promoting film may be formed on the front surface Wa of the first wafer W to appropriately delaminate the first wafer W and the laser absorbing layer P, and in this case, delamination may occur at the interface between the delamination-promoting film and the laser absorbing layer P.

[0111] 24( a), a peeling-promoting film Pe, a laser absorbing layer P, a device layer Dw, and a surface film Fw may be formed as laminated films in this order on the surface Wa of the first wafer W. The peeling-promoting film Pe is formed to facilitate peeling of the first wafer W from the second wafer S, and is made of a material that has lower adhesion to the first wafer W (silicon) than to the laser absorbing layer P and is transparent to the laser light L, such as silicon nitride (SiN).

[0112] When separating the first wafer W from the second wafer S, first, the laser absorption layer P is irradiated with laser light L (step St31 in FIG. 25). The laser light L passes through the first wafer W and the peeling-promoting film Pe and is absorbed by the laser absorption layer P (step St32 in FIG. 25).

[0113] The laser light L absorbed by the laser absorbing layer P is converted into heat in accordance with its energy distribution (step St33 in FIG. 25 ), thereby increasing the temperature of the laser absorbing layer P. Most of the heat generated in the laser absorbing layer P by absorbing the laser light L diffuses to the peeling-promoting film Pe on the first wafer W side (step St34 in FIG. 25 ), and this thermal diffusion increases the temperature of the interface between the laser absorbing layer P and the peeling-promoting film Pe.

[0114] When the heat generated in the laser absorbing layer P diffuses toward the first wafer W, the effect of this heat, i.e., the increase in the interface temperature between the laser absorbing layer P and the peeling promoting film Pe, causes the peeling promoting film Pe to expand locally in accordance with the temperature distribution, as shown in Fig. 24(b) (step St35 in Fig. 25). At this time, the thermal effect at the interface between the laser absorbing layer P and the peeling promoting film Pe may affect the first wafer W, and the first wafer W may also expand locally in accordance with the temperature distribution, as shown in Fig. 24(b).

[0115] Thereafter, when the peeling-promoting film Pe (and the first wafer W) expands locally, stress caused by this expansion causes peeling at the interface between the laser absorbing layer P and the peeling-promoting film Pe, which has low adhesion, as shown in Fig. 24(c), resulting in a decrease in the bonding strength between the laser absorbing layer P and the peeling-promoting film Pe (step St36 in Fig. 25). Then, by continuing the peeling over the entire surface of the interface between the peeling-promoting film Pe and the laser absorbing layer P, the bonding strength between the peeling-promoting film Pe and the laser absorbing layer P is decreased over the entire surface, and this allows the peeling-promoting film Pe and the laser absorbing layer P (the first wafer W and the second wafer S) to be properly separated in the separation device 32 (step St37 in Fig. 25).

[0116] In this way, by forming a peeling-promoting film Pe on the surface Wa of the first wafer W, which has lower adhesion to the first wafer W (silicon) than to the laser absorption layer P, and expanding the peeling-promoting film Pe instead of or together with the first wafer W, the transfer of the device layer Dw formed on the surface Wa of the first wafer W can be properly carried out.

[0117] In the example shown in FIG. 24, the peel-promoting film Pe is formed at the interface between the first wafer W and the laser absorption layer P, but for example, the peel-promoting film Pe may be formed at the interface between the laser absorption layer P and the device layer Dw, and peeling may occur at the interface between the laser absorption layer P and the peel-promoting film Pe, so that the peel-promoting film Pe remains on the second wafer S side to which the device layer Dw is transferred.

[0118] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The above-described embodiments may be omitted, substituted, or modified in various ways without departing from the scope and spirit of the appended claims. For example, the components of the above-described embodiments may be arbitrarily combined. Such an arbitrary combination naturally provides the functions and effects of each of the components involved in the combination, and also provides other functions and effects that are apparent to those skilled in the art from the description of this specification.

[0119] Furthermore, the effects described herein are merely descriptive or exemplary and are not limiting. In other words, the technology according to the present disclosure may achieve other effects that are apparent to those skilled in the art from the description of this specification, in addition to or in place of the above-described effects.

[0120] 31 Laser irradiation device 40 Control device 100 Chuck 103 Rotation mechanism 104 Movement mechanism 110 Laser irradiation unit L Laser light P Laser absorption layer S Second wafer T Overlapped wafer W First wafer

Claims

1. A substrate processing apparatus for processing a laminated substrate formed by laminating a first substrate, an interface layer including at least a laser absorption layer, and a second substrate, comprising: a substrate holding unit for holding the laminated substrate; a laser irradiation unit for irradiating the laminated substrate held by the substrate holding unit with laser light; a movement mechanism for horizontally moving the substrate holding unit and the laser irradiation unit relatively; a rotation mechanism for rotating the substrate holding unit; and a control unit, wherein the laminated substrate has an outer circumferential region including an unbonded region of the first substrate and the second substrate, and an inner circumferential region radially inward of the outer circumferential region and disposed in a bonded region of the first substrate and the second substrate, and the control unit performs the following control operations: rotates the laminated substrate and irradiates the laminated substrate with the laser light while moving it in the radial direction, to cause delamination at the interface between the first substrate and the laser absorption layer, or at the interface between the interface layer and the laser absorption layer; and irradiates at least the outer circumferential region with the laser light while moving it from the inner side toward the outer side in the radial direction.

2. The substrate processing apparatus of claim 1, wherein the inner peripheral region is defined as a first inner peripheral region on the radially outer side and a second inner peripheral region on the radially inner side, and the control unit performs the following control in the first inner peripheral region: keeping the frequency of the laser light constant while varying the rotation speed of the laminated substrate in accordance with the movement of the laser light, thereby irradiating the laser light in pulses; and keeping the rotation speed of the laminated substrate constant while varying the frequency of the laser light in accordance with the movement of the laser light, thereby irradiating the laser light in pulses in the second inner peripheral region.

3. The substrate processing apparatus according to claim 1 or 2, wherein the control unit executes control to irradiate the inner peripheral region with the laser light while moving it from the inside to the outside in the radial direction.

4. The substrate processing apparatus according to claim 3, wherein the control unit controls the irradiation of the laser light so that the stress generated in the outer peripheral region by the laser light is greater than the stress generated in the inner peripheral region by the laser light.

5. The substrate processing apparatus according to claim 1 or 2, wherein the control unit executes control to irradiate the inner peripheral region with the laser light while moving it from the outside to the inside in the radial direction.

6. A substrate processing apparatus according to claim 1 or 2, wherein the control unit executes control to reverse the rotation direction of the laminated substrate in adjacent regions when the movement direction of the laser light in the adjacent regions is different.

7. The substrate processing apparatus according to claim 1 or 2, wherein the control unit executes control to irradiate the laser light in the inner peripheral region after irradiating the laser light in the outer peripheral region.

8. The substrate processing apparatus according to claim 1 or 2, wherein the control unit executes control to irradiate the inner peripheral region with the laser light, and then irradiate the outer peripheral region with the laser light.

9. A substrate processing apparatus as described in claim 1 or 2, wherein a central region is set in the overlapping substrate radially inside the inner peripheral region and located in the bonding region of the first substrate and the second substrate, and the control unit executes control to irradiate the central region with the laser light while scanning it, while stopping the rotation of the overlapping substrate.

10. The substrate processing apparatus according to claim 1 or 2, wherein the interface layer includes a peeling-promoting film, and peeling at the interface between the interface layer and the laser absorbing layer occurs at the interface between the peeling-promoting film and the laser absorbing layer.

11. A substrate processing method for processing an overlapped substrate formed by laminating a first substrate, an interface layer including at least a laser absorption layer, and a second substrate, the substrate processing method comprising: defining, in the overlapped substrate, an outer circumferential region including an unbonded region of the first substrate and the second substrate, and an inner circumferential region radially inward of the outer circumferential region and disposed in a bonded region of the first substrate and the second substrate; holding the overlapped substrate with a substrate holding unit; rotating the overlapped substrate held by the substrate holding unit, and irradiating the overlapped substrate with a laser beam from a laser irradiation unit while moving the laser beam in the radial direction, to cause peeling at the interface between the first substrate and the laser absorption layer, or at the interface between the interface layer and the laser absorption layer; and irradiating at least the outer circumferential region with the laser beam while moving it from the inner side toward the outer side in the radial direction.

12. A substrate processing method as described in claim 11, comprising: defining a first inner peripheral region on the radially outer side and a second inner peripheral region on the radially inner side in the inner peripheral region; irradiating the laser light in pulses in the first inner peripheral region by varying the rotation speed of the overlapped substrate in accordance with the movement of the laser light while keeping the frequency of the laser light constant; and irradiating the laser light in pulses in the second inner peripheral region by varying the frequency of the laser light in accordance with the movement of the laser light while keeping the rotation speed of the overlapped substrate constant.

13. The substrate processing method according to claim 11 or 12, wherein the laser light is irradiated onto the inner peripheral region while moving from the inside to the outside in the radial direction.

14. A substrate processing method according to claim 13, wherein the laser light is applied so that the stress generated in the outer peripheral region by the laser light is greater than the stress generated in the inner peripheral region by the laser light.

15. The substrate processing method according to claim 11 or 12, wherein the laser light is irradiated onto the inner peripheral region while moving from the outer side to the inner side in the radial direction.

16. A substrate processing method according to claim 11 or 12, wherein when the moving directions of the laser light in adjacent regions are different, the rotation directions of the laminated substrate in the adjacent regions are reversed.

17. The substrate processing method according to claim 11 or 12, wherein the laser light is irradiated onto the outer peripheral region and then onto the inner peripheral region.

18. The substrate processing method according to claim 11 or 12, wherein the laser light is irradiated onto the inner peripheral region and then onto the outer peripheral region.

19. A substrate processing method as described in claim 11 or 12, comprising: setting a central region in the overlapping substrate radially inside the inner peripheral region and disposed in the bonding region of the first substrate and the second substrate; and irradiating the central region with the laser light while scanning it, while the rotation of the overlapping substrate is stopped.

20. A substrate processing method according to claim 11 or 12, wherein the interface layer includes a peeling-promoting film, and peeling at the interface between the interface layer and the laser absorbing layer occurs at the interface between the peeling-promoting film and the laser absorbing layer.