Substrate processing method, substrate processing apparatus, program, and computer storage medium

Abstract

To appropriately peel a second substrate off from a first substrate in a laminated substrate in which the first substrate and the second substrate are bonded together.SOLUTION: A substrate processing method for processing a laminated substrate formed by bonding a first substrate and a second substrate, the second substrate has a peeling-promoting layer and a laser absorbing layer stacked in this order from the second substrate side, the substrate processing method including radiating laser light from the second substrate side to the laser absorbing layer to generate stress at an interface between the laser absorbing layer and the peeling-promoting layer, and peeling the second substrate from the first substrate along a boundary between the laser absorbing layer and the peeling-promoting layer.SELECTED DRAWING: Figure 10

Description

[Technical Field]

[0001] The present disclosure relates to a substrate processing method, a substrate processing apparatus, a program, and a computer storage medium. [Background technology]

[0002] Patent Document 1 discloses a method for manufacturing a semiconductor device, which includes a heating step of locally heating a separation oxide film by irradiating a CO2 laser from the back surface of a semiconductor substrate, and a transfer step of causing separation in the separation oxide film and / or at the interface between the separation oxide film and the semiconductor substrate, and transferring a semiconductor element to a destination substrate. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2007-220749 Summary of the Invention [Problem to be solved by the invention]

[0004] The technology according to the present disclosure appropriately peels the second substrate from the first substrate in a laminated substrate in which the first substrate and the second substrate are bonded together. [Means for solving the problem]

[0005] One aspect of the present disclosure is a substrate processing method for processing a laminated substrate formed by bonding a first substrate and a second substrate, wherein a peeling-promoting layer and a laser absorption layer are formed on the second substrate by being stacked in this order from the second substrate side, and the substrate processing method includes irradiating laser light onto the laser absorption layer from the second substrate side to generate stress at the interface between the laser absorption layer and the peeling-promoting layer, and peeling the second substrate from the first substrate along the boundary between the laser absorption layer and the peeling-promoting layer. [Effects of the Invention]

[0006] According to the present disclosure, in a laminated substrate in which a first substrate and a second substrate are bonded together, the second substrate can be appropriately peeled off from the first substrate. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 2 is a side view illustrating an example of an overlapping wafer being processed in a wafer processing system. [Figure 2] FIG. 1 is a plan view schematically illustrating an outline of the configuration of a wafer processing system. [Figure 3] FIG. 2 is a side view showing the outline of the configuration of an interface laser irradiation device. [Figure 4] FIG. 2 is a plan view showing the outline of the configuration of an interface laser irradiation device. [Figure 5] 3A to 3C are explanatory views showing the state of forming a release improving layer according to the present embodiment. [Figure 6] 3 is a plan view showing an example of forming a release improving layer according to the present embodiment. FIG. [Figure 7] 1 is an explanatory diagram showing a gas flow inside an overlapping wafer in wafer processing according to the present embodiment. FIG. [Figure 8] FIG. 10 is a plan view showing another example of forming a release improving layer according to the present embodiment. [Figure 9] FIG. 10 is an explanatory view showing how the second wafer is peeled off in the present embodiment. [Figure 10] FIG. 10 is an explanatory view showing how the second wafer is peeled off in the present embodiment. [Figure 11] FIG. 10 is an explanatory view showing how the second wafer is pressed. [Figure 12] FIG. 10 is an explanatory view showing how the second wafer is pressed. [Figure 13] FIG. 10 is a side view showing an outline of the configuration of an overlapping wafer according to another embodiment. [Figure 14] FIG. 4 is an explanatory diagram showing the flow of edge trimming processing according to the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] In recent years, the LED manufacturing process has adopted a technique called laser lift-off, in which a GaN (gallium nitride) compound crystal layer (material layer) is peeled off from a sapphire substrate using laser light. The reason for this laser lift-off is that sapphire substrates are transparent to short-wavelength laser light (e.g., UV light), allowing the use of short-wavelength laser light with high absorption in the laser absorption layer, and also providing a wide range of laser light options.

[0009] Meanwhile, in the semiconductor device manufacturing process, a device layer formed on the surface of one substrate (a silicon substrate such as a semiconductor) is transferred to another substrate. Silicon substrates are generally transparent to laser light in the NIR (near infrared) range, but the laser absorption layer is also transparent to NIR laser light, which may damage the device layer. Therefore, to perform laser lift-off in the semiconductor device manufacturing process, laser light in the FIR (far infrared) range is used.

[0010] Generally, a laser beam with a wavelength of FIR can be used, for example, by a CO2 laser. In the method described in the above-mentioned Patent Document 1, a CO2 laser is irradiated onto a peeling oxide film serving as a laser absorption layer, thereby causing peeling at the interface between the peeling oxide film and the substrate.

[0011] However, after careful consideration by the present inventors, it was found that in the laser lift-off method, the substrate and the laser absorbing layer are not properly peeled off, that is, the transfer may not be performed properly. Specifically, if there is a region in the surface of the laser absorbing layer where the laser light is not irradiated and the bonding strength between the laser absorbing layer and the substrate is not reduced, the wafer W may be peeled off from the inside in the region not irradiated with the laser light, and a part of the wafer W (silicon piece) may be transferred together with the device layer to the surface of the laser absorbing layer after the transfer process.

[0012] The technology disclosed herein appropriately separates a second substrate from a first substrate in a laminated substrate in which a first substrate and a second substrate are bonded together. Hereinafter, a wafer processing system as a substrate processing apparatus and a wafer processing method as a substrate processing method according to this embodiment 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.

[0013] 1, the overlapped wafer T, which serves as an overlapping substrate to be processed in the wafer processing according to this embodiment, is formed by bonding a first wafer W1 serving as a first substrate and a second wafer W2 serving as a second substrate. Hereinafter, the surface of the first wafer W1 that is bonded to the second wafer W2 will be referred to as the front surface W1a, and the surface opposite the front surface W1a will be referred to as the back surface W1b. Similarly, the surface of the second wafer W2 that is bonded to the first wafer W1 will be referred to as the front surface W2a, and the surface opposite the front surface W2a will be referred to as the back surface W2b.

[0014] The first wafer W1 is a semiconductor wafer such as a silicon substrate. A device layer D1 including a plurality of devices is formed on the surface W1a of the first wafer W1. A surface film F1 is further formed on the device layer D1, and the first wafer W1 is bonded to the second wafer W2 via the surface film F1. Examples of the surface film F1 include an oxide film (SiO2 film, TEOS film), a SiC film, a SiCN film, or an adhesive. Note that the device layer D1 and the surface film F1 may not be formed on the surface W1a.

[0015] The second wafer W2 is also a semiconductor wafer such as a silicon substrate. A peeling-promoting layer P2, a laser absorbing layer P, a device layer D2, and a surface film F2 are formed on the surface W2a of the second wafer W2 in this order from the surface W2a side, and the second wafer W2 is bonded to the first wafer W1 via the surface film F2. The device layer D2 and the surface film F2 are similar to the device layer D1 and the surface film F1 of the first wafer W1, respectively. The laser absorbing layer P may be a material capable of absorbing laser light (e.g., a CO2 laser), as described below, such as an oxide film (SiO2 film, TEOS film). The peeling-promoting layer P2 is formed to facilitate peeling (transferring) of the second wafer W2 from the first wafer W1, and is made of a material that has lower adhesion to the second wafer W2 (silicon) than to the laser absorbing layer P, such as silicon nitride (SiN). The peeling-promoting layer P2, the laser absorbing layer P, the device layer D2, and the surface film F2 may not be formed on the surface W2a. In this case, the peeling-promoting layer P2 and the laser absorbing layer P are formed on the surface W1a of the first wafer W1 on which the device layer D1 and the surface film F1 are formed, and the device layer D1 is transferred to the second wafer W2.

[0016] The peripheral edge We of the second wafer W2 is chamfered, and the cross-section of the peripheral edge We tapers toward its tip. In the semiconductor device manufacturing process, the backside of the second wafer W2 thus formed may be removed to thin it, and this thinning process may result in the peripheral edge We having a sharp, pointed shape (a so-called knife-edge shape). This may cause chipping at the peripheral edge We of the second wafer W2, potentially damaging the second wafer W2. Therefore, before this thinning process, edge trimming (described below) may be performed to remove the peripheral edge We of the second wafer W2 in advance. The peripheral edge We is the portion removed in this edge trimming, and is, for example, a range of 0.5 mm to 3 mm in the radial direction from the outer edge of the second wafer W2.

[0017] In the wafer processing system 1 according to this embodiment, the aforementioned laser lift-off process as wafer processing, i.e., the process of transferring the device layer D2 to the first wafer W1 side, or the aforementioned edge trim process as wafer processing, i.e., the process of removing the peripheral portion We of the second wafer W2, is performed.

[0018] 2, the wafer processing system 1 has a configuration in which a load / unload block G1, a transfer block G2, and a processing block G3 are integrally connected. The load / unload block G1, the transfer block G2, and the processing block G3 are arranged in this order from the negative side of the X axis.

[0019] The carry-in / out block G1 carries in and out cassettes Ct, Cw1, and Cw2, each capable of accommodating a plurality of overlapping wafers T, a plurality of first wafers W1, and a plurality of second wafers W2, for example, between the outside and the block G1. A cassette mounting table 10 is provided in the carry-in / out block G1. In the illustrated example, the cassette mounting table 10 can freely mount a plurality of cassettes, for example, three cassettes Ct, Cw1, and Cw2, in a line in the Y-axis direction. The number of cassettes Ct, Cw1, and Cw2 mounted on the cassette mounting table 10 is not limited to that in this embodiment and can be determined arbitrarily.

[0020] In the transfer block G2, a wafer transfer device 20 is provided adjacent to the cassette mounting table 10 on the positive side of the X-axis of the cassette mounting table 10. The wafer transfer device 20 is configured to be movable on a transfer path 21 extending in the Y-axis direction. The wafer transfer device 20 also has, for example, two transfer arms 22, 22 that hold and transfer the overlapped wafer T, the first wafer W1, and the second wafer W2. Each transfer arm 22 is configured to be movable horizontally, vertically, around a horizontal axis, and around a vertical axis. Note that the configuration of the transfer arm 22 is not limited to this embodiment and may have any configuration. The wafer transfer device 20 is configured to be able to transfer the overlapped wafer T, the first wafer W1, and the second wafer W2 to the cassettes Ct, Cw1, and Cw2 on the cassette mounting table 10 and to a transition device 30, which will be described later.

[0021] In the transport block G2, a transition device 30 for transferring the overlapped wafer T, the first wafer W1, and the second wafer W2 is provided adjacent to the wafer transport device 20 on the positive X-axis side of the wafer transport device 20.

[0022] The processing block G3 includes a wafer transfer device 40, a peripheral edge removal device 50, a cleaning device 60, an internal laser irradiation device 70, and an interface laser irradiation device 80.

[0023] The wafer transfer device 40 is configured to be movable on a transfer path 41 extending in the X-axis direction. The wafer transfer device 40 also has, for example, two transfer arms 42, 42 that hold and transfer the overlapped wafer T, the first wafer W1, and the second wafer W2. Each transfer arm 42 is configured to be movable horizontally, vertically, around a horizontal axis, and around a vertical axis. The configuration of the transfer arm 42 is not limited to this embodiment and may have any configuration. The wafer transfer device 40 is also configured to be able to transfer the overlapped wafer T, the first wafer W1, and the second wafer W2 to the transition device 30, the edge removal device 50, the cleaning device 60, the internal laser irradiation device 70, and the interface laser irradiation device 80.

[0024] The edge removal device 50 is provided on the Y-axis positive side of the wafer transfer device 40 and performs edge trimming, i.e., removes the edge We of the second wafer W2. The cleaning device 60 is provided on the Y-axis negative side of the wafer transfer device 40 and cleans the overlapped wafer T after peeling or after removing the edge We. The internal laser irradiation device 70, serving as a second laser irradiation unit, is provided on the Y-axis positive side of the wafer transfer device 40 and irradiates the interior of the second wafer W2 with laser light (internal laser light, e.g., YAG laser) to form a peripheral modified layer M2, which serves as a base point for peeling the edge We. The interface laser irradiation device 80 is provided on the Y-axis negative side of the wafer transfer device 40 and irradiates the laser absorption layer P formed on the surface W2a of the second wafer W2 with laser light (interface laser light, e.g., CO2 laser). The configuration of the interface laser irradiation device 80 will be described later.

[0025] The wafer processing system 1 described above is provided with a control device 90 as a control unit. The control device 90 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 overlapped wafer T in the wafer processing system 1. The program storage unit also stores a program for controlling the operation of drive systems such as the various processing devices and transport devices described above to realize wafer processing, which will be described later, in the wafer processing system 1. The program may be recorded on a computer-readable storage medium H and installed into the control device 90 from the storage medium H.

[0026] The wafer processing system 1 is configured as described above, and can perform the above-mentioned laser lift-off process of the overlapped wafer T, i.e., the transfer process of the device layer D2 onto the first wafer W1, and the above-mentioned edge trim process of the second wafer W2, in the wafer processing system 1. Note that, for example, if the edge trim process of the second wafer W2 is not performed in the wafer processing system 1, the edge removal device 50 and the internal laser irradiation device 70 can be omitted.

[0027] Furthermore, in this embodiment, the separation of the second wafer W2 from the first wafer W1 is performed in the interface laser irradiation device 80 as described below, but the wafer processing system 1 may further be provided with a separate separation device as a separation section.

[0028] Next, the interface laser irradiation device 80 will be described.

[0029] 3 and 4, the interface laser irradiation device 80 has a chuck 100 that holds the overlapped wafer T on its upper surface. The chuck 100 holds a part of or the entire back surface W1b of the first wafer W1 by suction. The chuck 100 is provided with lifting pins (not shown) for transferring the overlapped wafer T to and from the transfer arm 42. The lifting pins are inserted through through holes (not shown) formed through the chuck 100 so as to be able to move up and down, and support and lift the overlapped wafer T from below.

[0030] 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 along a rail 105 provided on a base 106 and extending in the Y-axis direction by a movement mechanism 104 provided on the underside of the slider table 102. The drive source of the movement mechanism 104 is not particularly limited, but a linear motor, for example, is used.

[0031] A laser head 110 serving as a laser irradiation unit is provided above the chuck 100. The laser head 110 has a lens 111. The lens 111 is a cylindrical member provided on the lower surface of the laser head 110, and irradiates the overlapped wafer T held by the chuck 100 with laser light. In this embodiment, the laser light is a pulsed CO2 laser light, and the laser light emitted from the laser head 110 passes through the second wafer W2 and is irradiated onto the laser absorption layer P. The wavelength of the CO2 laser light is, for example, 8.9 μm to 11 μm. The laser head 110 is configured to be freely raised and lowered by an elevation mechanism (not shown). A light source of the laser light is provided at a position separate from the laser head 110.

[0032] A transfer pad 120 is provided above the chuck 100 and serves as a peeling unit. The transfer pad 120 has a suction surface on its lower surface for suction-holding the backside W2b of the second wafer W2. The transfer pad 120 is configured to be freely raised and lowered by a lifting mechanism (not shown). The transfer pad 120 transfers the second wafer W2 between the chuck 100 and the transfer arm 42. Specifically, after the chuck 100 is moved to below the transfer pad 120 (a transfer position with the transfer arm 42), the transfer pad 120 is lowered to suction-hold the backside W2b of the second wafer W2, and then the transfer pad 120 is raised again to peel the second wafer W2 from the first wafer W1. The peeled second wafer W2 is transferred from the transfer pad 120 to the transfer arm 42 and carried out of the interface laser irradiation device 80. The transfer pad 120 may be configured to flip the wafer over using a flipping mechanism (not shown).

[0033] Next, a description will be given of wafer processing performed using the wafer processing system 1 configured as described above. The following description will focus on a case where laser lift-off processing is performed in the wafer processing system 1, i.e., a case where the device layer D2 of the second wafer W2 is transferred to the first wafer W1. In this embodiment, the first wafer W1 and the second wafer W2 are bonded together in a bonding apparatus (not shown) external to the wafer processing system 1 to form a laminated wafer T in advance.

[0034] First, a cassette Ct containing a plurality of overlapping wafers T is placed on the cassette mounting table 10 of the carry-in / out block G1. Next, the overlapping wafers T are removed from the cassette Ct by the wafer transfer device 20. The overlapping wafers T removed from the cassette Ct are transferred to the wafer transfer device 40 via the transition device 30, and then transferred to the interface laser irradiation device 80. In the interface laser irradiation device 80, the second wafer W2 is peeled off from the first wafer W1 (laser lift-off process).

[0035] Specifically, the overlapped wafer T, which is attracted to and held by the chuck 100 via the lift pins on the transfer arm 42, is first moved to a processing position by the moving mechanism 104. This processing position is a position where the laser head 110 can irradiate the overlapped wafer T (laser absorption layer P) with laser light.

[0036] Next, as shown in FIGS. 5 and 6, pulsed laser light L (CO2 laser light) is irradiated from the laser head 110 toward the back surface W2b of the second wafer W2. At this time, the laser light L passes through the second wafer W2 and the peeling promoting layer P2 from the back surface W2b side of the second wafer W2 and is absorbed by the laser absorbing layer P. Then, stress is generated inside the laser absorbing layer P that has absorbed the laser light L, as shown in FIG. 7(a). Hereinafter, the stress accumulation layer formed by the irradiation of the laser light in this manner and serving as the base point for peeling of the second wafer W2 (the base point for transferring the device layer D2) may be referred to as the "peeling modified layer M1." Note that almost all of the energy of the laser light L irradiated to the laser absorbing layer P is absorbed by the formation of the peeling modified layer M1, and the laser light L does not reach the device layer D2. This prevents damage to the device layer D2.

[0037] Here, the laser light L irradiated onto the laser absorbing layer P is controlled to an output that does not cause the peeling promoting layer P2 and the laser absorbing layer P to peel off due to stress generated by the irradiation of the laser light L.

[0038] In this way, by irradiating the laser light L, peeling between the peel-promoting layer P2 and the laser absorbing layer P is prevented, and the generated stress has no escape route, so that stress accumulates inside the laser absorbing layer P, thereby forming the peel-modified layer M1. More specifically, for example, the laser absorbing layer P is gasified by irradiating it with laser light, and by eliminating the escape route for the generated gas as described above, compressive stress accumulates as the peel-modified layer M1. Furthermore, for example, heat is generated in the laser absorbing layer P by absorbing the laser light, and shear stress accumulates as the peel-modified layer M1 due to the difference in thermal expansion coefficient between the peel-promoting layer P2 and the laser absorbing layer P.

[0039] The stress generated by the irradiation of the laser light L usually remains at the irradiation position of the laser light L (inside the laser absorbing layer P) as described above, forming a peeling modified layer M1. However, in this embodiment, the peeling promoting layer P2 is formed between the surface W2a of the second wafer W2 and the laser absorbing layer P, and the adhesion between the peeling promoting layer P2 and the second wafer W2 is weaker than the adhesion between the peeling promoting layer P2 and the laser absorbing layer P. Therefore, as shown in FIG. 7(b), the stress generated inside the laser absorbing layer P passes through the peeling promoting layer P2 and accumulates at the interface between the peeling promoting layer P2 and the second wafer W2. In other words, the stress generated by the irradiation of the laser light L migrates to and accumulates at the interface between the peeling promoting layer P2 and the second wafer W2, where it can remain more stably. If stress accumulates at the interface between the peeling promoting layer P2 and the second wafer W2 in this way, the bonding strength between the peeling promoting layer P2 and the second wafer W2 decreases.

[0040] In this embodiment, the laser absorbing layer P is irradiated with the laser light L, i.e., the separation of the separation promoting layer P2 and the second wafer W2 is performed over the entire surface of the laser absorbing layer P in a planar view. Specifically, when the laser absorbing layer P is irradiated with the laser light L, the chuck 100 (superimposed wafer T) is rotated by the rotation mechanism 103, and the chuck 100 is moved in the Y-axis direction by the movement mechanism 104. In this way, the laser light L is irradiated onto the laser absorbing layer P, for example, from the outside to the inside in the radial direction, and as a result, the entire surface of the laser absorbing layer P is irradiated with the laser light L spirally from the outside to the inside. Note that the black arrow in FIG. 6 indicates the rotation direction of the chuck 100. Note that the separation modified layer M1 may be formed from the inside to the outside in the radial direction.

[0041] Here, the formation interval of adjacent peeling modified layers M1, in other words, the pulse interval (frequency) of the laser light L, is controlled to an interval that does not cause peeling in the adjacent peeling modified layers M1 due to the impact generated when forming the peeling modified layers M1. Specifically, for example, it is preferable that adjacent peeling modified layers M1 are formed so that they do not overlap each other in a planar view. In addition, it is preferable that adjacent peeling modified layers M1 are formed close to each other.

[0042] 8, the laser light L may be irradiated concentrically in an annular manner on the laser absorption layer P. In this case, however, since the rotation of the chuck 100 and the Y direction of the chuck 100 are alternately performed, irradiating the laser light L spirally as described above can shorten the irradiation time and improve the throughput.

[0043] In addition, in this embodiment, the chuck 100 is rotated when the laser light L is irradiated onto the laser absorption layer P, but the laser head 110 may be moved and rotated relative to the chuck 100. In addition, the chuck 100 is moved in the Y-axis direction, but the laser head 110 may be moved in the Y-axis direction.

[0044] After the laser light L is irradiated onto the in-plane front surface of the laser absorption layer P, the moving mechanism 104 moves the chuck 100 to a transfer position below the transfer pad 120. At the transfer position, the back surface W2b of the second wafer W2 is suction-held by the transfer pad 120 as shown in FIG. 9(a). Then, the transfer pad 120 is raised as shown in FIG. 9(b), thereby peeling the second wafer W2 from the peeling promoting layer P2 (first wafer W1). As a result, the device layer D2 formed on the surface of the second wafer W2 is transferred to the first wafer W1. At this time, as described above, stress generated by the laser light irradiation accumulates at the interface between the peeling promoting layer P2 and the second wafer W2, reducing the bonding strength. Therefore, the second wafer W2 can be peeled off from the peeling promoting layer P2 without applying a large load.

[0045] As described above, the release modified layers M1 are formed so as not to overlap each other. However, the stress accumulated by the formation of the release modified layers M1 is released to the outside when peeling occurs between the second wafer W2 and the release promoting layer P2 at the positions where the release modified layers M1 are formed. In this embodiment, the release modified layers M1 are formed close to each other as described above. Therefore, when peeling occurs at the positions where adjacent release modified layers M1 are formed, i.e., when stress is released to the outside at the adjacent positions, the stress is released in a chain reaction. That is, when a portion of the interface between the release promoting layer P2 and the second wafer W2 is peeled by raising the transfer pad 120, the entire surface of the second wafer W2 is peeled in a chain reaction starting from the peeled portion. That is, the second wafer W2 can be peeled more appropriately from the release promoting layer P2 without applying a large load.

[0046] As shown in FIG. 1, the laser absorption layer P irradiated with the laser light L may have a region (unpeeled region R1) where the laser light L is not irradiated due to factors such as the frequency of the laser light L and the rotation speed of the chuck 100. This region (unpeeled region R1) is therefore formed on the laser absorption layer P. However, according to this embodiment, the peeling promoting layer P2 is formed of a material with low adhesion to the second wafer W2 (silicon). Therefore, even when the unpeeled region R1 is formed, the peeling promoting layer P2 can be easily peeled from the second wafer W2. Furthermore, since the peeling promoting layer P2 and the second wafer W2 are properly peeled from each other, it is possible to appropriately prevent a portion of the second wafer W2 (silicon chips) from being transferred to the surface of the peeling promoting layer P2 after the second wafer W2 is peeled. This also reduces damage to the second wafer W2 after the peeling.

[0047] To properly separate the separation promoter layer P2 and the second wafer W2 at their interface, the stress generated by the laser beam irradiation must pass through the separation promoter layer P2. Specifically, for example, when the laser absorbing layer P is gasified, the generated gas must pass through the laser absorbing layer P. Furthermore, when separating the separation promoter layer P2 and the second wafer W2 due to differences in thermal expansion coefficients, the heat generated by the laser beam irradiation must be properly transferred to the interface between the separation promoter layer P2 and the second wafer W2. However, if the separation promoter layer P2 has a large thickness, the generated stress may not properly pass through the separation promoter layer P2 and may remain at the interface between the separation promoter layer P2 and the laser absorbing layer P. Therefore, to properly separate the separation promoter layer P2 and the second wafer W2 at their interface, the thickness of the separation promoter layer P2 is preferably thinner than that of the laser absorbing layer P. Specifically, the thickness of the separation promoter layer P2 is preferably about one-tenth the thickness of the laser absorbing layer P. By reducing the film thickness of the release promoting layer P2 in this way, the generated stress can be properly transmitted through the release promoting layer P2, and the bonding strength of the release promoting layer P2 to the second wafer W2 can be reduced, which means that the second wafer W2 can be properly peeled off from the release promoting layer P2.

[0048] However, even if the thickness of the peeling-promoting layer P2 becomes large and the generated stress does not properly pass through the peeling-promoting layer P2 but remains at the interface between the peeling-promoting layer P2 and the laser absorbing layer P, the peeling-promoting layer P2 can act as a protective film for the second wafer W2. That is, when the second wafer W2 is peeled from the inside, it is possible to properly prevent silicon pieces from being transferred to the interface after peeling together with the device layer D2.

[0049] Specifically, a peeling modified layer M1 is formed due to stress generated at the interface between the peeling promoting layer P2 and the laser absorbing layer P, and if stress remains at the interface, the second wafer W2 is peeled from the first wafer W1 at the boundary between the peeling promoting layer P2 and the laser absorbing layer P, as shown in Fig. 10. At this time, the second wafer W2 is peeled from the laser absorbing layer P via the peeling promoting layer P2, so that no part of the second wafer W2 remains at the peeling interface. In other words, this protects the surface W2a of the second wafer W2 and suppresses damage to the peeled surface.

[0050] The second wafer W2 separated from the first wafer W1 is transferred from the transfer pad 120 to the transfer arm 42 of the wafer transfer device 40 and transferred to the cassette Cw2 on the cassette mounting table 10. Note that the surface W2a of the second wafer W2 transferred from the interface laser irradiation device 80 may be cleaned in the cleaning device 60 before being transferred to the cassette Cw2.

[0051] Meanwhile, the first wafer W1 held by the chuck 100 is transferred to the transfer arm 42 of the wafer transfer device 40 via the lifting pins and transferred to the cleaning device 60. In the cleaning device 60, the surface of the peeling promoting layer P2, which is the peeling surface, is scrubbed and cleaned. Note that in the cleaning device 60, the back surface W1b of the first wafer W1 may also be cleaned together with the surface of the peeling promoting layer P2.

[0052] Thereafter, the first wafer W1, which has undergone all processes related to the transfer of the device layer D2 onto the first wafer W1, is transferred by the wafer transfer device 20 to the cassette Cw1 on the cassette mounting table 10 via the transition device 30. In this way, a series of wafer processing steps in the wafer processing system 1 is completed.

[0053] According to the above embodiment, the separation promoting layer P2 is formed between the second wafer W2 and the laser absorption layer P, thereby enabling the second wafer W2 to be appropriately separated from the first wafer W1, i.e., enabling the transfer process of the device layer D2 to be appropriately performed. Specifically, the stress generated in the laser absorption layer P by the irradiation of the laser light moves to the boundary between the second wafer W2 and the separation promoting layer P2, thereby reducing the bonding strength at the boundary between the second wafer W2 and the separation promoting layer P2, enabling the second wafer W2 to be appropriately separated from the separation promoting layer P2. Furthermore, since the separation promoting layer P2 is formed of a material (e.g., SiN) that has low adhesion to the second wafer W2, the separation of the separation promoting layer P2 from the second wafer W2 can be more appropriately performed.

[0054] In the above embodiment, a material with low adhesion to the second wafer W2 (silicon) is used as the release promoting layer P2. However, the material used for the release promoting layer P2 is not limited to this. For example, a material with a different thermal expansion coefficient than that of the second wafer W2 (silicon) may be used. In such a case, the amount of thermal deformation caused by irradiation of the laser light L onto the laser absorption layer P differs between the second wafer W2 and the release promoting layer P2. This generates a shear force at the interface between the second wafer W2 and the release promoting layer P2, enabling the second wafer W2 and the release promoting layer P2 to be separated. In particular, when shear stress is generated and accumulated as the release modified layer M1 at the interface between the second wafer W2 and the release promoting layer P2 as described above, using a material with a different thermal expansion coefficient for the release promoting layer P2 allows for more appropriate separation of the second wafer W2 from the release promoting layer P2.

[0055] In the above embodiment, the second wafer W2 is peeled off from the peeling promoting layer P2 by irradiation with the laser light L, but when peeling off the second wafer W2, warping may occur in the overlapped wafer T. If warping occurs in the overlapped wafer T in this way, there is a risk that the wafer processing system 1 will not be able to perform the wafer processing properly. Therefore, in order to suppress warping of the overlapped wafer T, the overlapped wafer T may be pressed from above when the laser absorbing layer P is irradiated with the laser light L.

[0056] For example, when warpage occurs such that the overlapped wafer T is deformed into an upward convex shape, the center of the overlapped wafer T may be pressed by a pressing member 200 as shown in FIG. 11. Specifically, when peeling off the second wafer W2, first, a peeled modified layer M1 is formed in advance in the center of the laser absorbing layer P, which is the pressing range by the pressing member 200. The direction in which the peeled modified layer M1 is formed in the radial direction is not particularly limited. After the peeled modified layer M1 is formed in the center of the laser absorbing layer P, the center of the overlapped wafer T on which the peeled modified layer M1 has been formed is then pressed by the pressing member 200. Then, with the center pressed by the pressing member 200, a peeled modified layer M1 is formed on the outer periphery of the laser absorbing layer P, and then the second wafer W2 is peeled off. At this time, since the center of the overlapped wafer T is pressed by the pressing member 200, the formation of the peeled and modified layer M1 on the outer periphery of the laser absorption layer P and the occurrence of warping of the overlapped wafer T when the second wafer W2 is peeled off are suppressed.

[0057] In addition, since the overlapped wafer T is rotated when the laser light L is irradiated, it is desirable that the end of the pressing member 200 be configured to be rotatable together with the overlapped wafer T.

[0058] Furthermore, for example, when warpage occurs such that the overlapped wafer T is deformed into a downward convex shape, the peripheral edge We of the overlapped wafer T may be pressed by a pressing member 200 as shown in FIG. 12 . Specifically, when peeling off the second wafer W2, first, a peeled modified layer M1 is formed in advance on the outer periphery of the laser absorbing layer P, which is the pressing range by the pressing member 200. After the peeled modified layer M1 is formed on the outer periphery of the laser absorbing layer P, the outer periphery of the overlapped wafer T on which the peeled modified layer M1 is formed is then pressed by the pressing member 200. Thereafter, with the outer periphery pressed by the pressing member 200, a peeled modified layer M1 is formed on the central portion of the laser absorbing layer P, and then the second wafer W2 is peeled off. At this time, because the outer periphery of the overlapped wafer T is pressed by the pressing member 200, warpage of the overlapped wafer T is suppressed when the peeled modified layer M1 is formed on the central portion of the laser absorbing layer P and when the second wafer W2 is peeled off.

[0059] In the overlapped wafer T processed in the above embodiment, a reflective film R may be provided between the laser absorbing layer P and the device layer D2 as shown in FIG. 13. That is, the reflective film R is formed on the surface of the laser absorbing layer P opposite to the incident surface of the laser light L. The reflective film R is made of a material having a high reflectivity to the laser light L and a high melting point, such as a metal film. The device layer D2 is a layer having a function and is different from the reflective film R.

[0060] In this case, the laser light L emitted from the laser head 110 passes through the second wafer W2 and is almost entirely absorbed by the laser absorption layer P, but even if there is laser light L that has not been absorbed, it is reflected by the reflective film R. As a result, the laser light L does not reach the device layer D2, and damage to the device layer D2 can be reliably suppressed.

[0061] Furthermore, the laser light L reflected by the reflective film R is absorbed by the laser absorption layer P. Therefore, the efficiency of peeling the second wafer W2 can be improved.

[0062] In the above embodiment, the laser lift-off process of the overlapped wafer T, i.e., the transfer process of the device layer D2 onto the first wafer W1, is performed in the wafer processing system 1. However, as described above, the edge trim process of the second wafer W2 can also be performed in the wafer processing system 1. Hereinafter, the case where the edge trim of the second wafer W2 is performed in the wafer processing system 1 will be described.

[0063] First, the overlapped wafer T is removed by the wafer transport device 20 from the cassette Ct placed on the cassette mounting table 10 of the loading / unloading block G1, and then transferred to the wafer transport device 40 via the transition device 30, and then transported to the internal laser irradiation device 70.

[0064] In the internal laser irradiation device 70, as shown in FIG. 14(a), laser light L2 (YAG laser light) is irradiated into the interior of the second wafer W2 to form a peripheral modified layer M2 that serves as a base point for removing the peripheral portion We in the edge trimming process described below. A crack C2 extends from the peripheral modified layer M2 in the thickness direction of the second wafer W2. The upper and lower ends of the crack C2 reach, for example, the back surface W2b and front surface W2a of the second wafer W2, respectively. The overlapped wafer T with the peripheral modified layer M2 formed inside the second wafer W2 is then transported by the wafer transport device 40 to the interface laser irradiation device 80.

[0065] In the interface laser irradiation device 80, the bonding strength between the peeling promoting layer P2 and the second wafer W2 at the peripheral edge We of the overlapped wafer T, which is the removal target of the second wafer W2, is reduced. Specifically, as shown in FIG. 14(b), laser light L (CO2 laser) is irradiated onto the laser absorbing layer P, and stress is generated inside the laser absorbing layer P radially outward of the peripheral modified layer M2 formed by the internal laser irradiation device 70. Furthermore, the generated stress passes through the peeling promoting layer P2, as shown in FIG. 14(c), and thereby stress accumulates at the boundary between the second wafer W2 and the peeling promoting layer P2.

[0066] The overlapped wafer T, in which the peeling modified layer M1 is formed over the entire peripheral edge portion We and the bonding strength between the peeling promoting layer P2 and the second wafer W2 is reduced, is then transported by the wafer transport device 40 to the peripheral edge removal device 50.

[0067] 14(d), the edge removal apparatus 50 removes the edge We of the second wafer W2 from the overlapped wafer T, starting from the edge modified layer M2 and the crack C2 (edge ​​trimming). Note that any edge trimming method can be selected in the edge removal apparatus 50. At this time, the bonding strength between the second wafer W2 and the peeling facilitating layer P2 has been reduced by the formation of the peeling modified layer M1, so that the edge We can be easily removed.

[0068] The overlapped wafer T, from which the peripheral edge We of the second wafer W2 has been removed, is then transferred by the wafer transfer device 40 to the cleaning device 60. In the cleaning device 60, the overlapped wafer T is subjected to scrubbing cleaning. After that, the overlapped wafer T, which has been subjected to all processing, is unloaded from the cleaning device 60 by the wafer transfer device 40, and transferred to the cassette Ct on the cassette mounting table 10 by the wafer transfer device 20 via the transition device 30. In this way, a series of wafer processing steps in the wafer processing system 1 is completed.

[0069] As described above, according to the technology of the present disclosure, the bonding strength between the second wafer W2 and the peeling promotion layer P2 at the peripheral edge We can be reduced in the interface laser irradiation device 80, thereby enabling the peripheral edge removal device 50 to appropriately remove the peripheral edge We, i.e., perform edge trimming.

[0070] The processing order of the overlapped wafer T by the internal laser irradiation device 70 and the interface laser irradiation device 80 is not limited to the above embodiment, and after the peripheral portion We is peeled off in the interface laser irradiation device 80, the peripheral modified layer M2 may be formed in the internal laser irradiation device 70.

[0071] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive, and the above-described embodiments may be omitted, substituted, or modified in various ways without departing from the scope and spirit of the appended claims. [Explanation of symbols]

[0072] D2 Device Layer L laser light P laser absorption layer P2 peel-promoting layer T Polymerized Wafer W1 First wafer W2 Second wafer W2a Surface W2b back

Claims

1. A substrate processing method for processing a laminated substrate in which a first substrate and a second substrate that is a silicon substrate are bonded together, comprising: a peeling-promoting layer and a laser absorbing layer are formed on the second substrate in this order from the second substrate side; The substrate processing method includes: Irradiating the laser absorption layer with a laser beam having a wavelength of far infrared rays from the second substrate side to generate stress at the interface between the laser absorption layer and the peeling-promoting layer, thereby reducing the bonding strength between the laser absorption layer and the peeling-promoting layer; peeling the second substrate from the first substrate along a boundary between the laser absorption layer and the peeling-facilitating layer.

2. 2. The substrate processing method according to claim 1, wherein the second substrate is formed with the peeling-promoting layer, the laser absorption layer, the device layer, and a surface film to be bonded to the first substrate stacked in this order from the second substrate side.

3. 3. The substrate processing method according to claim 2, wherein a reflective film is formed on the second substrate between the laser absorption layer and the device layer.

4. The substrate processing method according to claim 2 , wherein the first substrate has a device layer including a plurality of devices formed thereon.

5. 5. The substrate processing method according to claim 4, wherein a surface film for bonding is further formed on the device layer of the first substrate, and the device layer is bonded to the surface film for bonding of the second substrate via the surface film.

6. 6. The substrate processing method according to claim 5, wherein the surface films of the first substrate and the second substrate are oxide films.

7. The substrate processing method according to claim 5 , wherein the surface film of the first substrate is an adhesive.

8. Reducing the bonding strength between the laser absorption layer and the peeling-promoting layer comprises: By irradiating the laser light in pulses, The substrate processing method according to claim 1 , further comprising forming a release modifying layer that causes the stress to remain at the interface between the laser absorption layer and the release promoting layer.

9. A substrate processing method as described in claim 1, wherein the film thickness of the peeling-promoting layer is such that the stress accumulated at the interface between the laser absorption layer and the peeling-promoting layer remains when the laser light is irradiated.

10. The substrate processing method of claim 1, wherein the laser absorption layer is composed of TEOS.

11. A substrate processing apparatus for processing a laminated substrate in which a first substrate and a second substrate that is a silicon substrate are bonded together, a peeling-promoting layer and a laser absorbing layer are formed on the second substrate in this order from the second substrate side; The substrate processing apparatus includes: a laser irradiation unit that irradiates the laser absorption layer with laser light having a wavelength of far infrared rays; a peeling unit that peels the second substrate from the first substrate; a control unit that controls the operation of the laser irradiation unit and the peeling unit, The control unit irradiating the laser absorption layer with the laser light from the second substrate side to generate stress at the interface between the laser absorption layer and the peeling-promoting layer, thereby reducing the bonding strength between the laser absorption layer and the peeling-promoting layer; and peeling the second substrate from the first substrate along a boundary between the laser absorption layer and the peeling promotion layer.

12. A program that runs on a computer of a control device that controls a substrate processing system to cause the substrate processing system to execute a substrate processing method for processing a laminated substrate in which a first substrate and a second substrate that is a silicon substrate are bonded together, a peeling-promoting layer and a laser absorbing layer are formed on the second substrate in this order from the second substrate side; The substrate processing method includes: Irradiating the laser absorption layer with a laser beam having a wavelength of far infrared rays from the second substrate side to generate stress at the interface between the laser absorption layer and the peeling-promoting layer, thereby reducing the bonding strength between the laser absorption layer and the peeling-promoting layer; peeling the second substrate from the first substrate along a boundary between the laser absorption layer and the peel-facilitating layer.

13. A readable computer storage medium storing a program that runs on a computer of a control device that controls a substrate processing system so as to cause the substrate processing system to execute a substrate processing method for processing a laminated substrate in which a first substrate and a second substrate that is a silicon substrate are bonded together, a peeling-promoting layer and a laser absorbing layer are formed on the second substrate in this order from the second substrate side; The substrate processing method includes: Irradiating the laser absorption layer with a laser beam having a wavelength of far infrared rays from the second substrate side to generate stress at the interface between the laser absorption layer and the peeling-promoting layer, thereby reducing the bonding strength between the laser absorption layer and the peeling-promoting layer; peeling the second substrate from the first substrate along an interface between the laser absorbing layer and the peel-facilitating layer.

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