Substrate processing method and substrate processing system

Abstract

To appropriately transfer a device layer formed on a surface of a second substrate onto a first substrate in a laminated substrate in which the first substrate and the second substrate are bonded together.SOLUTION: In a method for transferring a device layer formed on a second substrate onto a first substrate in a laminated substrate in which the first substrate and the second substrate are bonded together, a first surface film is formed on the first substrate; a laser absorption layer, a Si film, a second device layer, and a second surface film are formed on the second substrate in this order from the surface side; and the first surface film of the first substrate and the second surface film of the second substrate are bonded to each other. The method includes irradiating the laser absorption layer with pulsed laser light from the back side of the second substrate so that the laser absorption layer absorbs the laser light, and peeling off the second substrate from the first substrate between the laser absorption layer and the second substrate to transfer the second device layer and the second surface film onto the first substrate.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a substrate processing method and a substrate processing system. [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 Application Laid-Open No. 2007-220749 Summary of the Invention [Problem to be solved by the invention]

[0004] The technique according to the present disclosure appropriately transfers a device layer formed on the surface of a second substrate to the first substrate in a laminated substrate in which a first substrate and a second substrate are bonded together. [Means for solving the problem]

[0005] One aspect of the present disclosure is a method for transferring a device layer formed on a second substrate to a first substrate in a laminated substrate formed by bonding a first substrate and a second substrate, the method comprising: forming a first surface film on the first substrate; a first device layer is formed between the surface of the first substrate and the first surface film;The second substrate has a laser absorption layer, a Si film, a second device layer, and a second surface film formed in this order from the front surface side, the first substrate and the second substrate are bonded together by the first surface film and the second surface film, and the laser absorption layer is irradiated with pulsed laser light from the back surface side of the second substrate to be absorbed by the laser absorption layer, and the second substrate is peeled off from the first substrate between the laser absorption layer and the second substrate, and the second device layer and the second surface film are transferred to the first substrate. [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, a device layer formed on the surface of the second substrate can be appropriately transferred to the first substrate. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 10 is an explanatory diagram comparing the power of laser light when a pulsed wave and a continuous wave are used. [Figure 2] 1 is a side view showing an outline of the configuration of overlapping wafers processed in a wafer processing system. [Figure 3] FIG. 1 is a plan view schematically illustrating an outline of the configuration of a wafer processing system. [Figure 4] 1 is a side view showing an outline of the configuration of a laser irradiation device according to an embodiment of the present invention. [Figure 5] 1 is a plan view showing an outline of the configuration of a laser irradiation device according to an embodiment of the present invention; [Figure 6] 5A and 5B are explanatory diagrams showing how a laser absorption layer is irradiated with laser light in the present embodiment. [Figure 7] 5A and 5B are explanatory diagrams showing how a laser absorption layer is irradiated with laser light in the present embodiment. [Figure 8] 10A and 10B are explanatory diagrams showing how a laser absorption layer is irradiated with laser light in a modified example of the present embodiment. [Figure 9] FIG. 10 is an explanatory view showing how the second wafer is peeled off from the laser absorption layer. [Figure 10] FIG. 10 is an explanatory diagram schematically illustrating an outline of the configuration of a laser irradiation unit according to another embodiment. [Figure 11] 10A and 10B are explanatory diagrams showing how the frequency of a laser beam is changed by an acousto-optic modulator in another embodiment. [Figure 12] 10A and 10B are explanatory diagrams showing how the frequency of a laser beam is changed by an acousto-optic modulator in another embodiment. [Figure 13] FIG. 10 is an explanatory diagram schematically illustrating an outline of the configuration of a laser irradiation unit according to another embodiment. [Figure 14] FIG. 10 is an explanatory diagram schematically illustrating an outline of the configuration of a laser irradiation unit according to another embodiment. [Figure 15] FIG. 10 is a side view showing an outline of the configuration of a laser irradiation device according to another embodiment. [Figure 16] FIG. 10 is a plan view showing an outline of the configuration of a laser irradiation device according to another embodiment. [Figure 17] 10A and 10B are explanatory diagrams showing how a laser absorption layer is irradiated with laser light in another embodiment. [Figure 18] 10A and 10B are explanatory diagrams showing how a laser absorption layer is irradiated with laser light in another embodiment. [Figure 19] 10A and 10B are explanatory diagrams showing how a laser absorption layer is irradiated with laser light in another embodiment. [Figure 20] FIG. 10 is a side view showing an outline of the configuration of a laser irradiation device according to another embodiment. [Figure 21] FIG. 4 is a side view showing an outline of the configuration of a guide portion. [Figure 22] FIG. 2 is a side view showing an outline of the configuration of a holding member. [Figure 23] FIG. 2 is a plan view showing an outline of the configuration of a guide portion and a holding member. [Figure 24] FIG. 10 is an explanatory view showing how a device layer formed on the surface of a second wafer is transferred to a first wafer in another embodiment. [Figure 25] FIG. 10 is an explanatory view showing how a device layer formed on the surface of a second wafer is transferred to a first wafer in another embodiment. [Figure 26] FIG. 10 is an explanatory view showing how a device layer formed on the surface of a second wafer is transferred to a first wafer in another embodiment. [Figure 27] FIG. 10 is an explanatory view showing how a device layer formed on the surface of a second wafer is transferred to a first wafer in another embodiment. [Figure 28] FIG. 10 is an explanatory view showing how a device layer formed on the surface of a second wafer is transferred to a first wafer in another embodiment. [Figure 29] FIG. 10 is a side view showing an outline of the configuration of an overlapping wafer according to another 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 rates in the 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 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 Patent Document 1, the separation oxide film is irradiated with a CO2 laser to cause separation at the interface between the separation oxide film and the substrate.

[0011] Here, the inventors conducted extensive research and found that simply irradiating a CO2 laser may not result in delamination. In other words, they discovered that the cause of delamination is not the amount of energy of the CO2 laser, but rather the peak power (maximum intensity of the laser light). For example, as shown in FIG. 1, when a CO2 laser is continuously oscillated (using a continuous wave), it is difficult to increase the peak power, and delamination may not occur. On the other hand, when a CO2 laser is oscillated in a pulsed manner (using a pulsed wave), the peak power can be increased, and delamination can occur. Note that the laser light emitted by a pulsed CO2 laser in this disclosure is a so-called pulsed laser, whose power repeatedly fluctuates between 0 (zero) and its maximum value.

[0012] Furthermore, when a CO2 laser is continuously oscillated, the thermal effect is large, making it impossible to perform stable laser lift-off, and there is a risk that the device layer will be damaged by the heat. From this perspective, it is therefore better to irradiate the CO2 laser in pulses.

[0013] As described above, in order to separate the substrate from the separation oxide film (device layer), it is necessary to irradiate the separation oxide film with a pulsed CO laser. However, the method of Patent Document 1 does not take pulsed lasers into consideration or suggest them at all. Therefore, there is room for improvement in the conventional device layer transfer method.

[0014] The technology disclosed herein appropriately transfers a device layer formed on a surface of a second substrate to a first substrate in a laminated substrate formed by bonding a first substrate and a 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 configuration are designated by the same reference numerals, and redundant description will be omitted.

[0015] In a wafer processing system 1 according to this embodiment, which will be described later, processing is performed on a laminated wafer T, which is a laminated substrate formed by bonding a first wafer W1 as a first substrate and a second wafer W2 as a second substrate, as shown in FIG. 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.

[0016] The first wafer W1 is a semiconductor wafer such as a silicon substrate. A device layer D1 and a surface film F1 are stacked in this order on the surface W1a of the first wafer W1. The device layer D1 includes a plurality of devices. 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.

[0017] The second wafer W2 is also a semiconductor wafer such as a silicon substrate. A laser absorbing layer P, a device layer D2, and a surface film F2 are stacked on the surface W2a of the second wafer W2 in this order from the surface W2a side. The laser absorbing layer P absorbs the laser light irradiated from the laser irradiation unit 110, as described below. The laser absorbing layer P may be, for example, an oxide film (SiO2 film), but is not particularly limited as long as it absorbs the laser light. 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 surface film F1 of the first wafer W1 and the surface film F2 of the second wafer W2 are bonded together. The position of the laser absorbing layer P is not limited to the above embodiment, and may be formed between the device layer D2 and the surface film F2, for example. The device layer D2 and the surface film F2 may not be formed on the surface W2a. In this case, the laser absorption layer P is formed on the first wafer W1 side, and the device layer D1 on the first wafer W1 side is transferred to the second wafer W2 side.

[0018] 3, 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) in the processing block 30 is disposed on the negative X-axis side of the transfer block 20, and a cleaning device 32 (described later) is disposed on the positive X-axis side of the transfer block 20.

[0019] The carry-in / out block 10 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. A cassette mounting table 11 is provided in the carry-in / out block 10. In the illustrated example, the cassette mounting table 11 can freely mount a plurality of cassettes, for example, three cassettes Ct, Cw1, and Cw2, in a line in the X-axis direction. The number of cassettes Ct, Cw1, and Cw2 mounted on the cassette mounting table 11 is not limited to that in this embodiment and can be determined arbitrarily.

[0020] 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 W1, and the second wafer W2. Each transfer arm 23 is movable horizontally, vertically, around a horizontal axis, and around a vertical axis. The configuration of the transfer arm 23 is not limited to this embodiment and may be any configuration. The wafer transfer device 22 is configured 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 11, the laser irradiation device 31, and the cleaning device 32, which will be described later.

[0021] The processing block 30 has a laser irradiation device 31 and a cleaning device 32. The laser irradiation device 31 irradiates the laser absorption layer P of the second wafer W2 with laser light. The configuration of the laser irradiation device 31 will be described later.

[0022] The cleaning device 32 cleans the surface of the laser absorbing layer P formed on the front surface W1a of the first wafer W1 separated by the laser irradiation device 31. For example, a brush is brought into contact with the surface of the laser absorbing layer P to scrub the surface. A pressurized cleaning liquid may be used to clean the front surface. The cleaning device 32 may also be configured to clean the back surface W1b of the first wafer W1 as well as the front surface W1a.

[0023] 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 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 40 from the storage medium H.

[0024] Next, the above-mentioned laser irradiation device 31 will be described.

[0025] As shown in Figures 4 and 5, the laser irradiation device 31 has a chuck 100 as a holder that holds the overlapped wafer T on its upper surface. The chuck 100 holds the entire back surface W1b of the first wafer W1 by suction. The chuck 100 may also hold a portion of the back surface W1b by suction. The chuck 100 is provided with lifting pins (not shown) for supporting the overlapped wafer T from below and lifting it up and down. The lifting pins are inserted into through holes (not shown) formed through the chuck 100 and are configured to be freely raised and lowered.

[0026] 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.

[0027] A laser irradiation unit 110 is provided above the chuck 100. The laser irradiation unit 110 has a laser head 111, an optical system 112, and a lens 113. The laser head 111 oscillates a pulsed laser beam. The optical system 112 controls the intensity and position of the laser beam, or attenuates the laser beam to adjust the output. The lens 113 is a cylindrical member that irradiates the laser beam onto the overlapped wafer T held by the chuck 100. In this embodiment, the laser beam is a CO2 laser beam, and the laser beam emitted from the laser irradiation unit 110 passes through the second wafer W2 and is irradiated onto the laser absorption layer P. The wavelength of the CO2 laser beam is, for example, 8.9 μm to 11 μm. The lens 113 is configured to be freely raised and lowered by an elevation mechanism (not shown).

[0028] A transfer pad 120 serving as a transfer unit is provided above the chuck 100. The transfer pad 120 is configured to be freely raised and lowered by an elevation mechanism (not shown). The transfer pad 120 has an adsorption surface for the second wafer W2. The transfer pad 120 transfers the second wafer W2 between the chuck 100 and the transfer arm 23. Specifically, after the chuck 100 is moved to a position below the transfer pad 120 (a transfer position with the transfer arm 23), the transfer pad 120 adsorbs and holds the back surface W2b of the second wafer W2 and peels it off from the first wafer W1. The peeled second wafer W2 is then transferred from the transfer pad 120 to the transfer arm 23 and carried out of the laser irradiation device 31. The transfer pad 120 may be configured to flip the wafer from its front to its back surface using an inversion mechanism (not shown).

[0029] 5, the transport arm 23 accesses the transport pad 120 from the positive side of the X-axis. However, the laser irradiation device 31 shown in FIG. 5 may be rotated 90 degrees counterclockwise so that the transport arm 23 accesses the transport pad 120 from the negative side of the Y-axis.

[0030] When the overlapped wafer T is carried into the laser irradiation device 31, the overlapped wafer T is transferred from the transfer arm 23 to the lift pins, and the lift pins are lowered to place the overlapped wafer T on the chuck 100. When the peeled first wafer W1 is carried out of the laser irradiation device 31, the overlapped wafer T placed on the chuck 100 is lifted by the lift pins, and then transferred from the lift pins to the transfer arm 23.

[0031] Next, a description will be given of wafer processing performed using the wafer processing system 1 configured as described above. In this embodiment, a first wafer W1 and a second wafer W2 are bonded together in a bonding device (not shown) external to the wafer processing system 1 to form an overlapped wafer T in advance.

[0032] 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.

[0033] 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 lifting pins and is held by suction on the chuck 100. Next, the moving mechanism 104 moves the chuck 100 to a processing position. This processing position is a position where the laser irradiation unit 110 can irradiate the overlapped wafer T (laser absorption layer P) with laser light.

[0034] Next, as shown in Figures 6 and 7, the laser irradiating unit 110 irradiates the laser absorbing layer P, more specifically, the interface between the laser absorbing layer P and the second wafer W2 with pulsed laser light L (CO2 laser light). At this time, the laser light L passes through the second wafer W2 from the back surface W2b side of the second wafer W2 and is absorbed in the laser absorbing layer P. Then, this laser light L causes peeling at the interface between the laser absorbing layer P and the second wafer W2. Note that the laser light L is almost entirely absorbed by the laser absorbing layer P and does not reach the device layer D2. This makes it possible to prevent damage to the device layer D2.

[0035] 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. As a result, the laser light L is irradiated onto the laser absorbing layer P from the outside to the inside in the radial direction, and as a result, the laser light L is irradiated spirally from the outside to the inside. Note that the black arrow in FIG. 7 indicates the rotation direction of the chuck 100.

[0036] The irradiation start position of the laser light L is preferably between the outer peripheral edge Ea of the second wafer W2 and the bonding edge Eb of the first wafer W1 and the second wafer W2 in the overlapped wafer T. In this case, even if the center of the first wafer W1 and the center of the second wafer W2 in the overlapped wafer T are misaligned and eccentric, for example, the eccentricity can be absorbed, and the laser light L can be appropriately irradiated onto the laser absorption layer P.

[0037] 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.

[0038] Furthermore, the laser light L may be irradiated from the radially inner side to the radially outer side of the laser absorbing layer P. However, in this case, since the inner side of the laser absorbing layer P peels off first, the stress associated with the peeling is directed radially outward, and the portion on the outer side that is not irradiated with the laser light L may also peel off. In this regard, when the laser light L is irradiated from the radially outer side to the radially inner side as described above, the stress associated with the peeling can be released to the outside, making it easier to control the peeling. Furthermore, by appropriately controlling the peeling, it is also possible to suppress roughness of the peeled surface.

[0039] In addition, in this embodiment, when the laser absorption layer P is irradiated with the laser light L, the chuck 100 is rotated, but the lens 113 may be moved and rotated relative to the chuck 100. In addition, although the chuck 100 is moved in the Y-axis direction, the lens 113 may be moved in the Y-axis direction.

[0040] In this way, in the laser irradiation device 31, the laser absorbing layer P is irradiated with the laser light L. Since the laser light L is irradiated in pulses, the peak power of the laser light L can be increased. Therefore, as described above with reference to FIG. 1, peeling can be caused at the interface between the laser absorbing layer P and the second wafer W2, and the second wafer W2 can be properly peeled off from the laser absorbing layer P.

[0041] Next, the chuck 100 is moved to the delivery position by the moving mechanism 104. Then, as shown in FIG. 9(a), the backside W2b of the second wafer W2 is sucked and held by the transfer pad 120. Thereafter, as shown in FIG. 9(b), while the transfer pad 120 is sucking and holding the second wafer W2, the transfer pad 120 is raised to peel the second wafer W2 from the laser absorbing layer P. At this time, because peeling has occurred at the interface between the laser absorbing layer P and the second wafer W2 due to the irradiation of the laser light L as described above, the second wafer W2 can be peeled off from the laser absorbing layer P without applying a large load.

[0042] The peeled second wafer W2 is transferred from the transfer pad 120 to the transfer arm 23 of the wafer transfer device 22 and transferred to the cassette Cw2 on the cassette mounting table 11. The second wafer W2 transferred from the laser irradiation device 31 may be transferred to the cleaning device 32 before being transferred to the cassette Cw2, where its peeled surface, that is, the front surface W2a, may be cleaned. In this case, the second wafer W2 may be turned over by the transfer pad 120 and then transferred to the transfer arm 23.

[0043] On the other hand, the first wafer W1 held by the chuck 100 is lifted from the chuck 100 by the lifting pins, transferred to the transfer arm 23, and transferred to the cleaning device 32. In the cleaning device 32, the surface of the laser absorbing layer P, which is the peeled surface, is scrubbed. Note that in the cleaning device 32, the back surface W1b of the first wafer W1 may also be cleaned together with the front surface of the laser absorbing layer P. Alternatively, separate cleaning units may be provided for cleaning the front surface of the laser absorbing layer P and the back surface W1b of the first wafer W1, respectively.

[0044] Thereafter, the first wafer W1, which has been subjected to all the processes, is transferred by the wafer transfer device 22 to the cassette Cw1 on the cassette mounting table 11. In this way, a series of wafer processes in the wafer processing system 1 is completed.

[0045] According to the above embodiment, in the laser irradiation device 31, the laser absorbing layer P is irradiated with the laser light L in a pulsed manner, and therefore the peak power of the laser light L can be increased, and as a result, delamination can be caused at the interface between the laser absorbing layer P and the second wafer W2. Furthermore, when the laser light L is irradiated in a pulsed manner, the thermal influence is smaller than when a continuous wave is used, and stable laser lift-off can be performed. Therefore, the second wafer W2 can be appropriately delaminated from the laser absorbing layer P, and the device layer D2 can be transferred to the first wafer W1.

[0046] Here, to ensure uniform peeling of the first wafer W1 and the second wafer W2 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. However, when the chuck 100 (superimposed wafer T) is rotated to keep the pulse interval constant, the rotation speed of the chuck 100 increases as the laser light L moves from the outer side to the inner side in the radial direction. In this case, when the rotation speed of the chuck 100 reaches its upper limit, the interval between the laser light L decreases as the irradiation position of the laser light L moves radially inward, and the laser light L may overlap at the center. Therefore, it is necessary to adjust the irradiation interval of the laser light L, and there are two methods for doing so, for example, as follows.

[0047] The first method is to control the rotation speed of the chuck 100. That is, when the irradiation position of the laser light L is on the radially outer side of the laser absorption layer P, the rotation speed is slowed down, and when the irradiation position of the laser light L is on the inner side, the rotation speed is increased. Note that the specific adjustment of this rotation speed is arbitrarily set according to the frequency of the laser light L. In such a case, the rotation speed of the chuck 100 can be kept constant, and the interval at which the laser light L is irradiated can be kept constant.

[0048] The second method is to control the frequency of the laser light L. That is, when the irradiation position of the laser light L is on the outer side in the radial direction of the laser absorption layer P, the frequency is increased, and when the irradiation position of the laser light L is on the inner side, the frequency is decreased. Note that the specific adjustment of this frequency is arbitrarily set according to the rotation speed of the chuck 100. Even in such a case, the rotation speed of the chuck 100 can be kept constant, and the interval at which the laser light L is irradiated can be kept constant.

[0049] In order to shorten the processing time (takt) of laser irradiation and improve the throughput, it is preferable to maintain the rotation speed of the chuck 100 using a high frequency laser light L in the first method.

[0050] The first and second methods may be used together. In this case, the rotation speed of the chuck 100 is slowed down on the radially outer side, and the frequency of the laser light L is increased. On the other hand, the rotation speed of the chuck 100 is fastened on the radially inner side, and the frequency of the laser light L is decreased.

[0051] Here, when controlling the frequency of the laser light L in the second method, for example, when controlling the frequency of the laser light L in the laser oscillator of the laser head 111, it is necessary to adjust parameters taking into account the output and pulse waveform of the laser light L. For example, if the energy of the laser light L required to peel off the outer and inner radial directions of the laser absorption layer P is the same, increasing the frequency of the laser light L on the outer side will require increasing the output, and decreasing the frequency of the laser light L on the inner side will require decreasing the output. Furthermore, changing the frequency of the laser light L in the laser oscillator will also change the pulse waveform of the laser light L. Therefore, complex adjustments taking into account the output and pulse waveform of the laser light L are required, making process control of the laser processing difficult.

[0052] Therefore, in this embodiment, an acousto-optic modulator is used as an optical element to control the frequency of the laser light L. As described above, the laser irradiation unit 110 includes the laser head 111, the optical system 112, and the lens 113.

[0053] 10, the laser head 111 has a laser oscillator 130 that oscillates a pulsed laser beam. The frequency of the laser beam oscillated from the laser oscillator 130 is the maximum frequency that can be controlled by an acousto-optic modulator 131, which will be described later. The laser head 111 may also have other devices in addition to the laser oscillator 130, such as an amplifier.

[0054] The optical system 112 has an acousto-optic modulator (AOM) 131 that deflects the laser light from the laser oscillator 130 in different directions, and an attenuator 132 that attenuates the laser light from the laser oscillator 130 and adjusts the output of the laser light. The acousto-optic modulator 131 and the attenuator 132 are provided in this order from the laser oscillator 130 side.

[0055] The acousto-optic modulator 131 is an optical modulator that electrically controls the intensity and position of a laser beam at high speed. As shown in FIG. 11 , when a laser beam L1 from a laser oscillator 130 is incident on the acousto-optic modulator 131, a voltage is applied to change the refractive index of the laser beam L1, thereby deflecting the laser beam L1 in different directions. Specifically, the deflection angle of the laser beam L1 can be controlled by adjusting the voltage. In this embodiment, for example, the laser beam L1 is deflected in two different directions, and the laser beam L2 in one direction is irradiated onto the laser absorption layer P, while the laser beam L3 in the other direction is not irradiated onto the laser absorption layer P. By controlling the deflection of the laser beams L2 and L3, the frequency of the laser beam L2 irradiated onto the laser absorption layer P can be adjusted.

[0056] In this case, the frequency of the laser light L2 irradiated onto the laser absorption layer P can be adjusted by thinning out pulses of the laser light L1 using the acousto-optic modulator 131. For example, if the redirection ratio of the laser light L2 and the laser light L3 relative to the laser light L1 is set to 100:0 at a certain timing, the laser light L1 becomes the laser light L2 as it is and is irradiated onto the laser absorption layer P. On the other hand, if the redirection ratio of the laser light L2 and the laser light L3 relative to the laser light L1 is set to 0:100 at another timing, the laser light L2 becomes 0 (zero), and the laser absorption layer P is not irradiated with the laser light L2. In this case, the frequency of the laser light L2 redirected by the acousto-optic modulator 131 shown in FIG. 12(b) can be adjusted relative to the frequency of the laser light L1 from the laser oscillator 130 shown in FIG. 12(a). Furthermore, since the frequency of the laser light L1 is the highest frequency that the acousto-optic modulator 131 can control as described above, the frequency of the laser light L2 can be adjusted arbitrarily. 12, the horizontal axis represents time, and the vertical axis represents the intensity of the laser light L2. That is, the density in the graph of FIG. 12 represents the frequency of the laser light L2.

[0057] Moreover, in this case, the frequency of the laser light L1 emitted from the laser oscillator 130 is not changed, so the pulse waveform of the laser light L1 remains unchanged, and the pulse waveform of the laser light L2 can also be made the same as the pulse waveform of the laser light L1. Therefore, the frequency of the laser light L2 can be easily adjusted, eliminating the need for the conventional complicated adjustments described above, and facilitating process control of the laser processing.

[0058] In this embodiment, the acousto-optic modulator 131 is used as the optical element, but this is not limiting. For example, an electro-optic modulator (EOM) may be used as the optical element. Also, an optical deflector such as an acousto-optic deflector (AOD) or an electro-optic deflector (EOD) may be used.

[0059] Next, a description will be given of a method for controlling the laser light L2 when the laser light L2 is irradiated from the laser irradiation unit 110 to the laser absorption layer P. As described above, when the irradiation position of the laser light L2 is on the outer side in the radial direction of the laser absorption layer P, the frequency is increased, and when the irradiation position of the laser light L2 is on the inner side, the frequency is decreased.

[0060] A specific example will be described below. Note that the numerical values ​​in this specific example are merely examples, and the present disclosure is not limited to these numerical values. For example, the energy required for peeling is 400 μJ on both the radially outer and inner sides of the laser absorbing layer P. The required frequency of the laser light L2 on the radially outer side of the laser absorbing layer P is 100 kHz, and the required frequency of the laser light on the inner side is 50 kHz. The frequency of the laser light L1 from the laser oscillator 130 is 100 kHz, and the output is 40 W.

[0061] In this case, the pulses of the laser light L1 from the laser oscillator 130 are not thinned out in the acousto-optic modulator 131 toward the radially outer side of the laser absorption layer P. This allows the frequency of the laser light L2 irradiated onto the laser absorption layer P to be 100 kHz, the same as the frequency of the laser light L1. Furthermore, the output of the laser light L2 is 40 W, the same as the output of the laser light L1. The energy of the laser light L2 is 400 μJ (= 40 W / 100 kHz), allowing for appropriate peeling.

[0062] On the other hand, for the radially inner side of the laser absorption layer P, the acousto-optic modulator 131 thins out half of the pulses of the laser light L1 from the laser oscillator 130. This makes it possible to set the frequency of the laser light L2 irradiated onto the laser absorption layer P to 50 kHz, which is half the frequency of the laser light L1. Furthermore, by thinning out the laser light L1 in this way, the output of the laser light L2 also becomes 20 W, which is half the output of the laser light L1. The energy of the laser light L2 becomes 400 μJ (= 20 W / 50 kHz), allowing for appropriate peeling.

[0063] In this way, the rotation speed of the chuck 100 is controlled according to the frequency and irradiation position of the laser light L2 so that the pulse intervals become constant. Then, the maximum rotation speed of the chuck 100 is maintained at the center of the laser absorption layer P, and the acousto-optic modulator 131 adjusts the frequency of the laser light L2 in accordance with the maximum rotation speed. This makes it possible to perform laser processing while maintaining the high rotation speed of the chuck 100 and the high frequency of the laser light L2 to the maximum, thereby achieving high-throughput laser processing.

[0064] Moreover, in this case, since the frequency of the laser light L1 from the laser oscillator 130 is not changed, the pulse waveform of the laser light L1 remains unchanged, and the pulse waveform of the laser light L2 can be made the same as the pulse waveform of the laser light L1. Therefore, the frequency of the laser light L2 can be easily adjusted, enabling continuous, seamless processing. As a result, process control of the laser processing becomes easier, and a stable process can be achieved.

[0065] In this embodiment, the output of the laser beam L1 from the laser oscillator 130 was 40 W, so there was no need to adjust the output to achieve the energy of 400 μJ required for delamination. In this regard, if the output of the laser beam L1 is 50 W, for example, the output of the laser beam L1 can be adjusted by attenuating the output of the laser beam L1 by 20% in the attenuator 132.

[0066] In the laser irradiation unit 110 of the above embodiment, the acousto-optic modulator 131 is provided upstream of the attenuator 132 inside the optical system 112, but the installation location is not limited to this. For example, as shown in Fig. 13, the acousto-optic modulator 131 may be provided downstream of the attenuator 132 inside the optical system 112. Alternatively, as shown in Fig. 14, the acousto-optic modulator 131 may be provided downstream of the laser oscillator 130 inside the laser head 111. Furthermore, the acousto-optic modulator 131 may be provided in two or more of the above installation positions.

[0067] In the laser irradiation unit 110, after the frequency and output of the laser light L2 are adjusted by the acousto-optic modulator 131, the output can be finely adjusted by the attenuator 132. Here, the output of the laser light L1 oscillated from the laser oscillator 130 may vary due to individual differences in the laser oscillator 130. The attenuator 132 can adjust such output variations. Furthermore, when the output of the laser light L1 from the laser oscillator 130 is monitored over time, the output can be adjusted by feedback-controlling the attenuator 132. From the viewpoint of finely adjusting the output of the laser light L2 by the attenuator 132 in this way, it is preferable that the acousto-optic modulator 131 be provided upstream of the attenuator 132, as shown in FIG. 10 .

[0068] In the laser irradiation unit 110 of the above embodiment, the attenuator 132 may be omitted. For example, the output of the laser light L2 can be adjusted by the acousto-optic modulator 131 instead of the attenuator 132. For example, if the output of the laser light L1 is 50 W and the output of the laser light L2 required for peeling is 40 W, the output of the laser light L2 can be set to 40 W by setting the redirection ratio of the laser light L2 and the laser light L3 relative to the laser light L1 in the acousto-optic modulator 131 to 80:20.

[0069] In the above embodiment, the laser light L is irradiated onto the laser absorption layer P in a spiral or concentric pattern, but the irradiation pattern of the laser light L is not limited to this. Furthermore, the configuration of the device corresponding to such various irradiation patterns is not limited to the laser irradiation device 31 of the above embodiment. In the above laser irradiation device 31, the chuck 100 is rotatable around the θ axis and movable in one axis (Y axis) direction, but it may be movable in two axes (X axis and Y axis).

[0070] The laser irradiation apparatus 200 shown in Figures 15 and 16 is an apparatus that moves the chuck 100 in two axes (X-axis and Y-axis). The laser irradiation apparatus 200 has a chuck 210 as a holder that holds the overlapped wafer T on its upper surface. The chuck 210 holds the back surface W1b of the first wafer W1 by suction. The chuck 210 is provided with lifting pins (not shown) that support the overlapped wafer T from below and lift it up and down. The lifting pins are inserted into through holes (not shown) formed through the chuck 210 and are configured to be able to move up and down freely.

[0071] The chuck 210 is supported by a slider table 212 via an air bearing 211. A rotation mechanism 213 is provided on the underside of the slider table 212. The rotation mechanism 213 has a built-in motor, for example, as a drive source. The chuck 210 is configured to be rotatable around the θ-axis (vertical axis) by the rotation mechanism 213 via the air bearing 211. The slider table 212 is configured to be movable along rails 215, which are provided on a moving stage 216 and extend in the Y-axis direction, by a moving mechanism 214 provided on the underside of the slider table 212. The drive source of the moving mechanism 214 is not particularly limited, but a linear motor, for example, is used.

[0072] The moving stage 216 is configured to be movable along rails 217 that are provided on a base 218 and extend in the X-axis direction by a moving mechanism (not shown) provided on the underside of the moving stage 216. The driving source of the moving mechanism is not particularly limited, but a linear motor, for example, is used. With this configuration, the chuck 210 is rotatable around the θ-axis and movable in the X-axis and Y-axis directions.

[0073] A laser irradiation unit 220 is provided above the chuck 210. The laser irradiation unit 220 has a laser head 221, an optical system 222, and a lens 223. The laser head 221 oscillates a pulsed laser beam L. The optical system 222 controls the intensity and position of the laser beam L, or attenuates the laser beam L to adjust the output. The lens 223 is a cylindrical member that irradiates the laser beam L, which is, for example, a CO2 laser beam, onto the overlapped wafer T held by the chuck 210. The lens 223 is configured to be freely raised and lowered by an elevation mechanism (not shown).

[0074] A galvanometer, for example, is used in the laser head 221. A plurality of galvanometer mirrors (not shown) are arranged inside the laser head 221. An f-θ lens is used as the lens 223. With this configuration, the laser light L input to the laser head 221 is reflected by the galvanometer mirror, propagates to the lens 223 via the optical system 222, passes through the second wafer W2, and is irradiated onto the laser absorption layer P. Then, by adjusting the angle of the galvanometer mirror, the laser light L can be scanned over the laser absorption layer P.

[0075] A transport pad 230 serving as a transport unit is provided above the chuck 210. The transport pad 230 is configured to be able to move up and down freely using an elevator mechanism (not shown). The configuration of the transport pad 230 is similar to the configuration of the transport pad 120 in the above embodiment.

[0076] In the laser irradiation apparatus 200, the overlapped wafer T is transferred from the transfer arm 23 to the lifting pins and is held by suction on the chuck 210. Then, the chuck 210 is moved to a processing position by the moving mechanism 214 and the moving stage 216. This processing position is a position where the laser irradiation unit 220 can irradiate the overlapped wafer T (laser absorption layer P) with laser light L.

[0077] 17, the laser absorbing layer P is irradiated with pulsed laser light L from the laser irradiation unit 220. At this time, the laser light L passes through the second wafer W2 from the back surface W2b side of the second wafer W2 and is absorbed in the laser absorbing layer P.

[0078] When the laser light L is irradiated onto the laser absorbing layer P, the laser light L is scanned within a predetermined scan range A (a square region in FIG. 17). Next, with the irradiation of the laser light L stopped, the chuck 210 is moved in the X-axis direction. In this manner, irradiation and scanning of the laser light L and movement of the chuck 210 are repeated, so that the laser light L is irradiated in a line in the X-axis direction. Next, the chuck 210 is moved so as to be shifted in the Y-axis direction, and irradiation and scanning of the laser light L and movement of the chuck 210 are repeated in the same manner as above, so that the laser light L is irradiated in a line in the X-axis direction. In this way, the laser absorbing layer P is irradiated with the laser light L.

[0079] In this embodiment, when irradiating the laser absorption layer P with the laser light L, the chuck 210 is moved in the X-axis direction and the Y-axis direction, but the lens 223 may be moved relative to the chuck 210.

[0080] Next, the chuck 210 is moved to the delivery position by the moving mechanism 214 and the moving stage 216. Then, the back surface W2b of the second wafer W2 is sucked and held by the transfer pad 230, and the transfer pad 230 is raised to peel off the second wafer W2 from the laser absorption layer P.

[0081] This embodiment can also achieve the same effects as the above-described embodiment. That is, since the laser absorbing layer P is irradiated with the laser light L in pulses, the peak power of the laser light L can be increased, and as a result, appropriate delamination can be caused at the interface between the laser absorbing layer P and the second wafer W2. Moreover, since the laser light L can be irradiated with the same density in the scan range A, the laser absorbing layer P can be irradiated with the laser light L uniformly.

[0082] In this embodiment, there may be a plurality of laser irradiation units 220. In this case, the laser absorption layer P can be irradiated with a plurality of laser beams L, which can shorten the processing time and further improve the throughput.

[0083] In the above embodiment, irradiation and scanning of the laser light L and movement of the chuck 210 are repeated, but irradiation and scanning of the laser light L may be performed while moving the chuck 210 in a line in the X-axis direction as shown in Fig. 18. Then, after irradiating the laser light L in a line in the X-axis direction, the chuck 210 is moved so as to be shifted in the Y-axis direction, and the laser light L is irradiated onto the laser absorption layer P.

[0084] In this embodiment, the same effects as those of the above embodiment can be obtained. That is, since the laser absorbing layer P is irradiated with the laser light L in pulses, it is possible to appropriately cause delamination at the interface between the laser absorbing layer P and the second wafer W2. Moreover, since the irradiation and scanning of the laser light L is not stopped in one row in the X-axis direction, it is possible to shorten the processing time of the laser irradiation and further improve the throughput.

[0085] The irradiation of the spiral (or concentric) laser light L in the above embodiment and the irradiation and scanning of the laser light L may be combined.

[0086] As described above, when the chuck 210 (superimposed wafer T) is rotated, in order to keep the pulse interval constant, the rotation speed of the chuck 210 increases as the laser light L moves from the outer side to the inner side in the radial direction. Therefore, in the above embodiment, the irradiation interval of the laser light L is adjusted by controlling at least the rotation speed or frequency of the chuck 210.

[0087] 19, in the outer peripheral portion of the laser absorbing layer P, the chuck 210 is rotated and moved from the outer side to the inner side in the radial direction, and the laser light L is irradiated in a spiral. Then, when the rotation speed of the chuck 210 reaches an upper limit, the rotation of the chuck 210 is stopped at the central portion of the laser absorbing layer P, and the laser light L is irradiated and scanned in the scan range A. Note that although the scan range A is illustrated as being rectangular, the shape of the scan range A is not limited thereto. For example, the scan range A may be circular.

[0088] In this way, by changing the irradiation pattern of the laser light L between the outer periphery and the center of the laser absorption layer P, it is possible to prevent overlapping of the laser light L and to make constant the interval at which the laser light L is irradiated, i.e., the pulse interval. As a result, the first wafer W1 and the second wafer W2 can be peeled off uniformly within the wafer surface.

[0089] When the irradiation range of the laser light L from the laser irradiation unit 220 is wide, for example, when the irradiation range is equal to or larger than the diameter of the laser absorbing layer P, the laser light L may be irradiated onto the entire surface of the laser absorbing layer P at once.

[0090] In the laser irradiation device 31 of the above embodiment, a guide portion 240 and a holding member 250 may be provided on the upper surface of the chuck 100 as shown in FIG.

[0091] 21 , the guide portion 240 guides the overlapped wafer T relative to the chuck 100. The guide portion 240 has a vertical portion 241 extending vertically upward from the chuck 100 and an inclined portion 242 whose diameter increases upward from the vertical portion 241. The inner diameter of the vertical portion 241 is slightly larger than the diameter of the overlapped wafer T. The overlapped wafer T placed above the chuck 100 is centered by the inclined portion 242, and is further guided by the vertical portion 241 to be held by the chuck 100.

[0092] As shown in FIGS. 22 and 23 , the holding member 250 extends vertically upward from the upper surface of the chuck 100 and holds the side surface of the second wafer W2. The holding members 250 are arranged at multiple locations, for example, three locations, on a concentric circle of the chuck 100. The holding members 250 are configured to be movable forward and backward by a moving mechanism 251 so as to come into contact with or separate from the second wafer W2. The holding member 250 is also configured to be rotatable integrally with the chuck 100. The holding member 250 holds the second wafer W2, thereby preventing the second wafer W2 from shifting or slipping off. A notch 233 is formed in the guide portion 240 at a position corresponding to the holding member 250, and the holding member 250 moves through the notch 233 so as not to interfere with the guide portion 240.

[0093] In this embodiment, both the guide portion 240 and the holding member 250 are provided, but only the guide portion 240 or only the holding member 250 may be provided. When only the guide portion 240 is provided, the vertical portion 241 can prevent the second wafer W2 from shifting or slipping off. In particular, the guide portion 240 is useful when the gap between the vertical portion 241 and the second wafer W2 is within the allowable range for misalignment. However, providing both the guide portion 240 and the holding member 250 improves the effects of centering the overlapped wafer T and preventing the second wafer W2 from shifting or slipping off.

[0094] In this case, when the overlapped wafer T is held by the chuck 100 at the delivery position, the three holding members 250 are retracted to positions where they do not contact the second wafer W2. After that, the chuck 100 holding the overlapped wafer T is moved to the processing position, and then the three holding members 250 are moved to positions where they contact the side surfaces of the second wafer W2, and these holding members 250 hold the second wafer W2.

[0095] Here, if the guide section 240 or the holding member 250 were not present, when the laser light L was irradiated spirally from the outside to the inside in the radial direction of the laser absorbing layer P, as the peeling progressed, centrifugal force would act on the second wafer W2 because the chuck 100 was rotating, causing the second wafer W2 to shift from the laser absorbing layer P, and there was a risk that the laser light L would be irradiated to a location other than the processing target position during laser processing. There was also a possibility that the peeled second wafer W2 would slide off. In this regard, in this embodiment, the second wafer W2 is held by the holding member 250, so that such shifting or sliding off of the second wafer W2 can be prevented.

[0096] Next, after irradiation with the laser light L, the second wafer W2 is held by the holding member 250 when the chuck 100 is moved to the delivery position. Here, an inertial force acts on the second wafer W2 while the chuck 100 is moving, and the second wafer W2 may be displaced from the laser absorption layer P. In such a case, when the back surface W2b of the second wafer W2 is subsequently sucked and held by the transfer pad 120, the second wafer W2 cannot be held in an appropriate position. Therefore, in this embodiment, the second wafer W2 is held by the holding member 250 even while the chuck 100 is moving, preventing the second wafer W2 from being displaced.

[0097] The configuration of the holding member that holds the second wafer W2 is not limited to the configuration of the holding member 250. For example, the holding member may hold the second wafer W2 from the sides thereof so as to sandwich the top and side surfaces of the second wafer W2. The holding member may also hold the second wafer W2 from the middle of the laser processing. If the holding member is made of a material that transmits the laser light L, such as silicon, it may hold the top surface of the second wafer W2.

[0098] The wafer processing system 1 in the above embodiment includes the cleaning apparatus 32, but the wafer processing system 1 may further include an etching apparatus (not shown). The etching apparatus etches the surface W1a of the first wafer W1 after separation, specifically the surface of the laser absorbing layer P. For example, after the cleaning apparatus 32 scrubs and cleans the surface of the laser absorbing layer P, a chemical solution (etchant) is supplied to the surface of the laser absorbing layer P to wet-etch the surface. The wafer processing system 1 may also include either the cleaning apparatus 32 or the etching apparatus.

[0099] The wafer processing system 1 of the above embodiment may also include a CMP device (not shown). In the CMP device, the surface W1a of the first wafer W1 after separation, specifically the surface of the laser absorbing layer P, is subjected to CMP (Chemical Mechanical Polishing). For example, after the surface of the laser absorbing layer P is scrubbed and cleaned in the cleaning device 32, the surface of the laser absorbing layer P is subjected to CMP processing to flatten the surface of the laser absorbing layer P. The CMP device may be provided outside the wafer processing system 1.

[0100] In the above embodiment, the interface between the laser absorbing layer P and the second wafer W2 is irradiated with laser light L to peel off the second wafer W2 from the laser absorbing layer P, but the peeling may be performed so that the laser absorbing layer P remains on the second wafer W2, as shown in FIG. 24, for example.

[0101] In such a case, in the laser irradiation device 31, as shown in Fig. 24(a), the laser irradiation unit 110 irradiates the interface between the laser absorption layer P and the device layer D2 with pulsed laser light L. Then, the laser light L causes peeling at the interface between the laser absorption layer P and the device layer D2.

[0102] The adjustment of the absorption position of the laser light L, i.e., the adjustment of the peeling position of the laser absorbing layer P, is performed by controlling the energy density of the laser light L required to peel off the laser absorbing layer P according to the film type of the laser absorbing layer P. For example, the energy density of the laser light L can be adjusted by adjusting the focus numerical aperture (NA) of the laser irradiation unit 110, changing the focus position of the laser light L, changing the original output of the laser light L, etc.

[0103] Next, with the back surface W2b of the second wafer W2 being sucked and held by the transfer pad 120, the transfer pad 120 is raised as shown in FIG. 24(b) to peel off the laser absorption layer P from the device layer D2.

[0104] This embodiment can also achieve the same effects as the above-described embodiment. That is, since the laser light L is irradiated to the laser absorbing layer P in pulses, the peak power of the laser light L can be increased, and as a result, appropriate delamination can be caused at the interface between the laser absorbing layer P and the device layer D2. Moreover, the laser absorbing layer P remaining on the second wafer W2 is an oxide film (SiO2 film), and this laser absorbing layer P can be used as an oxide film (insulating film) when fabricating TSVs (Through-Silicon Vias) on the second wafer W2 in a subsequent semiconductor manufacturing process, for example.

[0105] In this embodiment, the surface of the laser absorption layer P on the second wafer W2 after separation may be scrubbed and then subjected to CMP processing using the above-mentioned CMP device. In this case, the surface of the laser absorption layer P can be flattened. As described above, it can be appropriately used as an oxide film (insulating film) when fabricating TSVs.

[0106] In the above embodiment, the case where the overlapped wafer T shown in Fig. 2 is processed has been described, but the processing target is not limited to this. Hereinafter, the case where different types of overlapped wafer T are processed will be described with reference to Figs. 25 to 28.

[0107] The processing of the overlapped wafer T shown in FIG. 25 will be described. As shown in FIG. 25(a), the laser absorbing layer P1 formed between the second wafer W2 and the device layer D2 is formed inside the second wafer W2. The second wafer W2 is, for example, an SOI substrate, and the laser absorbing layer P1 is, for example, an oxide film (SiO2 film). That is, the second wafer W2 is Si, the laser absorbing layer P1 is an SiO2 film, and the Si film S is Si, which are stacked in this order. Note that the laser absorbing layer P1 may be made of a film other than an oxide film (SiO2 film), such as silicon germanium (SiGe) or germanium (Ge), as long as it peels off at the interface with the Si film S.

[0108] 25(b), a device layer D2 and a surface film F2 are formed on the surface of the laser absorption layer P1. The device layer D2 and the surface film F2 are formed in a normal substrate process (FEOL) or wiring process (BEOL).

[0109] Next, the first wafer W1 and the second wafer W2 are bonded together as shown in Fig. 25(c). A surface film F1 is formed on the surface W1a of the first wafer W1, and this surface film F1 and the surface film F2 are bonded together.

[0110] 25(d), in the laser irradiation device 31 of the wafer processing system 1, the laser irradiation unit 110 irradiates the interface between the laser absorbing layer P1 and the Si film S with pulsed laser light L. Then, this laser light L causes peeling at the interface between the laser absorbing layer P1 and the Si film S.

[0111] Next, with the back surface W2b of the second wafer W2 being held by suction on the transfer pad 120, the transfer pad 120 is raised as shown in FIG. 25(e) to peel off the laser absorption layer P1 from the Si film S.

[0112] In this embodiment, too, similarly to the case shown in FIG. 24, the peeling position of the laser absorbing layer P1 may be adjusted to absorb the laser light L, i.e., the peeling position of the laser absorbing layer P1, so that peeling occurs at the interface between the second wafer W2 and the laser absorbing layer P1.

[0113] A description will be given of the processing of the overlapped wafer T shown in Fig. 26. As shown in Fig. 26(a) and (b), a laser absorption layer P2 made of silicon germanium (SiGe) and a Si film S made of Si are stacked in this order from the second wafer W2 side between the second wafer W2 and the device layer D2.

[0114] Next, as shown in FIG. 26(b), a device layer D2 and a surface film F2 are formed on the surface of the Si film S.

[0115] Next, the first wafer W1 and the second wafer W2 are bonded together as shown in Fig. 26(c). A device layer D1 and a surface film F1 are formed on the surface W1a of the first wafer W1, and the surface film F1 and the surface film F2 are bonded together.

[0116] 26(d), in the laser irradiation device 31 of the wafer processing system 1, the laser irradiation unit 110 irradiates the interface between the laser absorbing layer P2 and the Si film S with pulsed laser light L. Then, this laser light L causes peeling at the interface between the laser absorbing layer P2 and the Si film S.

[0117] 26(e), with the back surface W2b of the second wafer W2 being held by suction on the transfer pad 120, the transfer pad 120 is raised to peel off the laser absorbing layer P2 from the Si film S. Note that in this embodiment as well, the peeling position of the laser absorbing layer P1 may be adjusted to the absorption position of the laser light L, i.e., the peeling position of the laser absorbing layer P1, in the same way as in the case shown in FIG.

[0118] The following describes the processing of the overlapped wafer T shown in Fig. 27. As shown in Fig. 27(a) and (b), a laser absorption layer P3 made of an oxide film (SiO2 film), a SiGe film S1 made of SiGe, and a Si film S2 made of Si are stacked in this order from the second wafer W2 side between the second wafer W2 and the device layer D2.

[0119] Next, as shown in FIG. 27(b), a device layer D2 and a surface film F2 are formed on the surface of the Si film S2 made of Si.

[0120] Next, the first wafer W1 and the second wafer W2 are bonded together as shown in Fig. 27(e). A device layer D1 and a surface film F1 are formed on the surface W1a of the first wafer W1, and the surface film F1 and the surface film F2 are bonded together.

[0121] Next, in the laser irradiation device 31 of the wafer processing system 1, as shown in Fig. 27(d), the laser irradiation unit 110 irradiates the interface between the laser absorbing layer P3 and the second wafer W2 with pulsed laser light L. Then, this laser light L causes peeling at the interface between the laser absorbing layer P3 and the second wafer W2.

[0122] Next, with the back surface W2b of the second wafer W2 being sucked and held by the transfer pad 120, the transfer pad 120 is raised as shown in FIG. 27(e) to separate the second wafer W2 from the laser absorption layer P3.

[0123] The processing of the overlapped wafer T shown in Figure 28 will be described. The overlapped wafer T has a structure in which a Ge-pMOS is stacked on a Si-nMOS. As shown in Figure 28(a), a device layer D1 and a surface film F1 are formed on the surface W1a of the first wafer W1. In other words, the first wafer W1 is a Si-nMOS.

[0124] 28(b), the first wafer W1 is bonded to a second wafer W2, which is a Ge-pMOS. On the surface W2a of the second wafer W2, a laser absorption layer P4 made of an oxide film (SiO2 film), a device layer D2 made of Ge, and a surface film F2 are stacked in this order from the second wafer W2 side.

[0125] Next, the first wafer W1 and the second wafer W2 are bonded together as shown in Fig. 28(c) Specifically, the surface film F1 and the surface film F2 are bonded together.

[0126] Next, in the laser irradiation device 31 of the wafer processing system 1, as shown in Fig. 28(d), the laser irradiation unit 110 irradiates the interface between the laser absorption layer P4 and the device layer D2 with pulsed laser light L. Then, the laser light L causes peeling at the interface between the laser absorption layer P4 and the device layer D2.

[0127] Next, with the back surface W2b of the second wafer W2 being sucked and held by the transfer pad 120, the transfer pad 120 is raised as shown in Fig. 28(e) to peel the laser absorbing layer P4 from the device layer D2. Note that in this embodiment as well, the peeling position of the laser absorbing layer P1 may be adjusted to absorb the laser light L, i.e., the peeling position of the laser absorbing layer P1, in the same way as in the case shown in Fig. 24, so that peeling occurs at the interface between the second wafer W2 and the laser absorbing layer P4.

[0128] The same effects as those of the above embodiment can be obtained with any of the processing targets shown in FIGS.

[0129] 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. 29. 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 with respect 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.

[0130] In this case, the laser light L emitted from the laser irradiation unit 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.

[0131] 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.

[0132] 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]

[0133] 31 Laser irradiation device 100 Chuck 110 Laser irradiation unit D1, D2 device layers P laser absorption layer T Polymerized Wafer W1 First wafer W2 Second wafer

Claims

1. A method for transferring a device layer formed on a second substrate to a first substrate in a laminated substrate formed by bonding a first substrate and a second substrate, the method comprising: a first surface film is formed on the first substrate; a first device layer is formed between the surface of the first substrate and the first surface film; a laser absorption layer, a Si film, a second device layer, and a second surface film are formed on the second substrate in this order from the surface side; the first substrate and the second substrate are bonded together at the first surface film and the second surface film, irradiating the laser absorption layer with pulsed laser light from the back surface side of the second substrate so that the laser absorption layer absorbs the laser light; peeling the second substrate from the first substrate between the laser absorption layer and the second substrate, and transferring the second device layer and the second surface film to the first substrate.

2. A method for transferring a device layer formed on a second substrate to a first substrate in a laminated substrate formed by bonding a first substrate and a second substrate, the method comprising: a first surface film is formed on the first substrate; a laser absorption layer made of SiGe, a Si film, a second device layer, and a second surface film are formed on the second substrate in this order from the surface side; the first substrate and the second substrate are bonded together at the first surface film and the second surface film, irradiating the laser absorption layer with pulsed laser light from the back surface side of the second substrate so that the laser absorption layer absorbs the laser light; peeling the second substrate from the first substrate between the laser absorption layer and the second substrate, and transferring the second device layer and the second surface film to the first substrate.

3. A method for transferring a device layer formed on a second substrate to a first substrate in a laminated substrate formed by bonding a first substrate and a second substrate, the method comprising: a first surface film is formed on the first substrate; a laser absorption layer made of Ge, a Si film, a second device layer, and a second surface film are formed on the second substrate in this order from the surface side; the first substrate and the second substrate are bonded together at the first surface film and the second surface film, irradiating the laser absorption layer with pulsed laser light from the back surface side of the second substrate so that the laser absorption layer absorbs the laser light; peeling the second substrate from the first substrate between the laser absorption layer and the second substrate, and transferring the second device layer and the second surface film to the first substrate.

4. A method for transferring a device layer formed on a second substrate to a first substrate in a laminated substrate formed by bonding a first substrate and a second substrate, the method comprising: a first surface film is formed on the first substrate; a laser absorption layer, a Si film, a second device layer, and a second surface film are formed on the second substrate in this order from the surface side; the first substrate and the second substrate are bonded together at the first surface film and the second surface film, While rotating the laminated substrate, irradiating the laser absorption layer with pulsed laser light from the back surface side of the second substrate, so that the laser absorption layer absorbs the laser light; peeling the second substrate from the first substrate between the laser absorption layer and the second substrate, and transferring the second device layer and the second surface film to the first substrate; a rotation speed of the laminated substrate is faster when the laser light is irradiated to the inside of the laser absorption layer in the radial direction than when the laser light is irradiated to the outside of the laser absorption layer, and a frequency of the laser light irradiated to the outside of the laser absorption layer in the radial direction is higher than a frequency of the laser light irradiated to the inside.

5. irradiating the laser absorption layer with the laser light from the outside to the inside in the radial direction; 5. The substrate processing method according to claim 1, wherein the irradiation of the laser light is started between an outer peripheral edge of the second substrate and an outer peripheral edge of the laser absorption layer, which is a joining edge between the first substrate and the second substrate in the laminated substrate.

6. 6. The substrate processing method according to claim 1, wherein the laser light is irradiated in a circular pattern onto the laser absorption layer by alternately rotating the laminated substrate and moving the laminated substrate in a radial direction.

7. 7. The substrate processing method according to claim 1, further comprising cleaning the first substrate from which the second substrate has been separated.

8. 8. The substrate processing method according to claim 1, further comprising etching the first substrate from which the second substrate has been separated.

9. 9. The substrate processing method according to claim 1, further comprising the step of performing a CMP process on the first substrate from which the second substrate has been separated.

10. the first surface film is an oxide film, 10. The substrate processing method according to claim 1, wherein the second surface film is an oxide film.

11. 1. A substrate processing system for transferring a device layer formed on a surface of a second substrate to a first substrate in a laminated substrate formed by bonding a first substrate and a second substrate, the system comprising: a first surface film is formed on the first substrate; a first device layer is formed between the surface of the first substrate and the first surface film; a laser absorption layer, a Si film, a second device layer, and a second surface film are formed on the second substrate in this order from the surface side; the first substrate and the second substrate are bonded together at the first surface film and the second surface film, a holding portion that holds the rear surface of the first substrate; a laser irradiation unit that irradiates the laser absorption layer with pulsed laser light from the back surface side of the second substrate while the holding unit holds the first substrate, so that the laser absorption layer absorbs the laser light; a transfer unit that separates the second substrate from the first substrate between the laser absorption layer and the second substrate and transfers the second device layer and the second surface film to the first substrate.

12. The substrate processing system according to claim 11 , further comprising a cleaning apparatus that cleans the first substrate from which the second substrate has been separated.

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