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 peeling oxide film by irradiating a CO2 laser from the back surface of a semiconductor substrate, and a transfer step of transferring a semiconductor element to a destination substrate by causing peeling in the peeling oxide film and / or at the interface between the peeling oxide film and the semiconductor substrate. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2007-220749 A 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; forming a laser absorption layer, a Si film, a second device layer, and a second surface film on the second substrate in this order from a surface side; bonding the first substrate and the second substrate with the first surface film and the second surface film; irradiating a laser beam in a pulsed manner from a back surface side of the second substrate to the laser absorption layer to cause the laser absorption layer to absorb the laser beam; 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. Effect 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 description of the drawings]

[0007] [Figure 1] FIG. 11 is an explanatory diagram comparing the power of laser light when a pulse wave and a continuous wave are used. [Diagram 2] 1 is a side view showing an outline of a configuration of overlapping wafers processed in a wafer processing system. [Diagram 3] 1 is a plan view illustrating a schematic configuration of a wafer processing system. [Figure 4] 1 is a side view showing an outline of a configuration of a laser irradiation device according to an embodiment of the present invention. [Diagram 5] 1 is a plan view showing an outline of a configuration of a laser irradiation device according to an embodiment of the present invention. [Figure 6] 4 is an explanatory diagram showing a state in which a laser absorption layer is irradiated with laser light in the embodiment; FIG. [Figure 7] 4 is an explanatory diagram showing a state in which a laser absorption layer is irradiated with laser light in the embodiment; FIG. [Figure 8]10A and 10B are explanatory diagrams showing a state in which a laser absorption layer is irradiated with laser light in a modified example of the present embodiment. [Figure 9] FIG. 13 is an explanatory diagram showing a state in which the second wafer is peeled off from the laser absorption layer. [Figure 10] FIG. 11 is an explanatory diagram illustrating a schematic configuration of a laser irradiation unit according to another embodiment. [Figure 11] 13 is an explanatory diagram showing how the frequency of a laser beam is changed by an acousto-optic modulator in another embodiment. FIG. [Figure 12] 13 is an explanatory diagram showing how the frequency of a laser beam is changed by an acousto-optic modulator in another embodiment. FIG. [Figure 13] FIG. 11 is an explanatory diagram illustrating a schematic configuration of a laser irradiation unit according to another embodiment. [Figure 14] FIG. 11 is an explanatory diagram illustrating a schematic configuration of a laser irradiation unit according to another embodiment. [Figure 15] FIG. 11 is a side view showing an outline of the configuration of a laser irradiation device according to another embodiment. [Figure 16] FIG. 11 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 a state in which a laser absorption layer is irradiated with laser light in another embodiment. [Figure 18] 10A and 10B are explanatory diagrams showing a state in which a laser absorption layer is irradiated with laser light in another embodiment. [Figure 19] 10A and 10B are explanatory diagrams showing a state in which a laser absorption layer is irradiated with laser light in another embodiment. [Figure 20] FIG. 11 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. 4 is a side view showing an outline of the configuration of a holding member. [Figure 23] 4 is a plan view showing an outline of the configuration of a guide portion and a holding member. FIG. [Figure 24]FIG. 11 is an explanatory view showing a state in which a device layer formed on a surface of a second wafer is transferred to a first wafer in another embodiment. [Diagram 25] FIG. 11 is an explanatory view showing a state in which a device layer formed on a surface of a second wafer is transferred to a first wafer in another embodiment. [Figure 26] FIG. 11 is an explanatory view showing a state in which a device layer formed on a surface of a second wafer is transferred to a first wafer in another embodiment. [Figure 27] FIG. 11 is an explanatory view showing a state in which a device layer formed on a surface of a second wafer is transferred to a first wafer in another embodiment. [Figure 28] FIG. 11 is an explanatory view showing a state in which a device layer formed on a surface of a second wafer is transferred to a first wafer in another embodiment. [Figure 29] FIG. 11 is a side view showing an outline of a configuration of an overlapping wafer according to another embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] In recent years, in the manufacturing process of LEDs, a so-called laser lift-off has been performed in which a GaN (gallium nitride) compound crystal layer (material layer) is peeled off from a sapphire substrate using laser light. The reason why laser lift-off is performed in this way is that the sapphire substrate is transparent to short-wavelength laser light (e.g. UV light), so that short-wavelength laser light with high absorption rate can be used for the absorption layer, and there is a wide range of choices for laser light.

[0009] Meanwhile, in the manufacturing process of semiconductor devices, 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, so there is a risk of the device layer being damaged. Therefore, to perform laser lift-off in the manufacturing process of semiconductor devices, laser light in the FIR (far infrared) range is used.

[0010] Generally, for example, a CO2 laser can be used to emit laser light having a wavelength of FIR. In the method described in the above-mentioned Patent Document 1, the peeling oxide film is irradiated with a CO2 laser to cause peeling at the interface between the peeling oxide film and the substrate.

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

[0012] In addition, when the 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 point of view, it is therefore better to irradiate the CO2 laser in a pulsed manner.

[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 CO2 laser. However, the method of Patent Document 1 does not take into consideration the pulsed laser at all, nor does it suggest it. 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 device according to the present embodiment and a wafer processing method as a substrate processing method will be described with reference to the drawings. In this specification and the drawings, elements having substantially the same functional configurations are denoted by the same reference numerals to avoid redundant description.

[0015] In the wafer processing system 1 according to the present embodiment, which will be described later, a process is performed on a laminated wafer T as a laminated substrate in which a first wafer W1 as a first substrate and a second wafer W2 as a second substrate are bonded together as shown in Fig. 2. Hereinafter, in the first wafer W1, the surface that is bonded to the second wafer W2 is referred to as the front surface W1a, and the surface opposite the front surface W1a is referred to as the back surface W1b. Similarly, in the second wafer W2, the surface that is bonded to the first wafer W1 is referred to as the front surface W2a, and the surface opposite the front surface W2a is referred to as the back surface W2b.

[0016] The first wafer W1 is a semiconductor wafer such as a silicon substrate. On the surface W1a of the first wafer W1, a device layer D1 and a surface film F1 are laminated in this order from the surface W1a side. 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. On the surface W2a of the second wafer W2, a laser absorbing layer P, a device layer D2, and a surface film F2 are laminated 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 later. The laser absorbing layer P is, 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 the same as the device layer D1 and the surface film F1 of the first wafer W1, respectively. Then, the surface film F1 of the first wafer W1 and the surface film F2 of the second wafer W2 are bonded. 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. In addition, 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 transport block 20, and a processing block 30 are integrally connected. The load / unload block 10 and the processing block 30 are provided around the transport block 20. Specifically, the load / unload block 10 is disposed on the negative Y-axis side of the transport block 20. A laser irradiation device 31 (described later) of the processing block 30 is disposed on the negative X-axis side of the transport block 20, and a cleaning device 32 (described later) is disposed on the positive X-axis side of the transport block 20.

[0019] The carry-in / out block 10 carries in and out cassettes Ct, Cw1, and Cw2 capable of accommodating a plurality of overlapped wafers T, a plurality of first wafers W1, and a plurality of second wafers W2, for example, between the outside and the inside of the device. The carry-in / out block 10 is provided with a cassette mounting table 11. 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 the present 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 configured to be movable in the horizontal direction, the vertical direction, around the horizontal axis, and around the vertical axis. The configuration of the transfer arm 23 is not limited to this embodiment, and may have any configuration. The wafer transfer device 22 is configured to 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 11, the laser irradiation device 31, and the cleaning device 32, which will be described later.

[0021] The processing block 30 includes 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 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. Note that a pressurized cleaning liquid may be used to clean the surface. The cleaning device 32 may be configured to clean the back surface W1b of the first wafer W1 as well as the front surface W1a.

[0023] The above-described wafer processing system 1 is provided with a control device 40 as a control unit. The control device 40 is, for example, a computer, and has a program storage unit (not shown). The program storage unit stores a program for controlling the processing of the laminated wafer T in the wafer processing system 1. The program storage unit also stores a program for controlling the operation of a drive system such as the above-described various processing devices and transport device to realize wafer processing in the wafer processing system 1, which will be described later. The above-described program may be recorded in a computer-readable storage medium H and installed in 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 suction-holds the entire back surface W1b of the first wafer W1. The chuck 100 may also suction-hold a portion of the back surface W1b. 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 through 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 lower surface side 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 about a 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 lower surface side of the chuck 100. The drive source of the movement mechanism 104 is not particularly limited, but for example, a linear motor is used.

[0027] A laser irradiation unit 110 is provided above the chuck 100. The laser irradiation unit 110 includes a laser head 111, an optical system 112, and a lens 113. The laser head 111 oscillates a laser beam in a pulsed manner. 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, and irradiates the laser beam onto the laminated 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 a lifting mechanism (not shown).

[0028] A transfer pad 120 is provided above the chuck 100 as a transfer unit. The transfer pad 120 is configured to be freely raised and lowered by a lifting 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. Then, the peeled second wafer W2 is transferred from the transfer pad 120 to the transfer arm 23 and carried out from the laser irradiation device 31. The transfer pad 120 may be configured to reverse the front and back surfaces of the wafer by a reversing mechanism (not shown).

[0029] In the laser irradiation device 31 shown in Fig. 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 transport 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 is transferred from the lift pins to the transport arm 23.

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

[0032] First, a cassette Ct storing a plurality of overlapped wafers T is placed on the cassette placement table 11 of the carry-in / out block 10.

[0033] Next, the overlapped wafer T is taken out of 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 lift pins and is adsorbed and held by 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 Figs. 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 rear 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 suppress 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 rotating mechanism 103, and the chuck 100 is moved in the Y-axis direction by the moving mechanism 104. Then, the laser light L is irradiated from the outside to the inside in the radial direction onto the laser absorbing layer P, 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 are misaligned and eccentric in the overlapped wafer T, for example, the eccentricity can be absorbed and the laser light L can be appropriately irradiated to the laser absorption layer P.

[0037] 8, the laser light L may be irradiated in a concentric ring shape on the laser absorption layer P. However, in this case, since the rotation of the chuck 100 and the Y direction of the chuck 100 are alternately performed, it is better to irradiate the laser light L in a spiral shape as described above, because it is possible to shorten the irradiation time and improve the throughput.

[0038] Also, the laser light L may be irradiated from the radially inner side to the outer side in the laser absorbing layer P. However, in this case, since the inner side of the laser absorbing layer P peels off first, the stress accompanying the peeling is directed to the radially outer side, and the part 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 inner side as described above, the stress accompanying the peeling can be released to the outside, making it easier to control the peeling. Also, by appropriately controlling the peeling, it is possible to suppress roughness of the peeled surface.

[0039] In addition, in this embodiment, when irradiating the laser absorption layer P with the laser light L, the chuck 100 is rotated, but the lens 113 may be moved and rotated relatively to the chuck 100. In addition, the chuck 100 is moved in the Y-axis direction, but 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 a pulsed manner, 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 appropriately 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 back surface W2b of the second wafer W2 is adsorbed and held by the transfer pad 120. Thereafter, as shown in FIG. 9(b), while the transfer pad 120 is adsorbing 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, since 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 of 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, and its peeled surface, that is, the front surface W2a, may be cleaned. In this case, the front and back surfaces of the second wafer W2 may be inverted by the transfer pad 120 and transferred to the transfer arm 23.

[0043] On the other hand, the first wafer W1 held by the chuck 100 is raised 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 and cleaned. Note that in the cleaning device 32, the back surface W1b of the first wafer W1 may be cleaned together with the front surface of the laser absorbing layer P. Also, 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 manner, 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, so that the peak power of the laser light L can be increased, and as a result, peeling 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 effect 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 peeled off from the laser absorbing layer P, and the device layer D2 can be transferred to the first wafer W1.

[0046] Here, in order to make the separation of the first wafer W1 and the second wafer W2 uniform within the wafer surface, it is preferable to make 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 in order to make 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 such a case, when the rotation speed of the chuck 100 reaches an upper limit, the interval of the laser light L becomes smaller 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, for example, the following two methods.

[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 radial outside 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 inside, the rotation speed is fastened. The specific adjustment of this rotation speed is arbitrarily set according to the frequency of the laser light L. In this case, the rotation speed of the chuck 100 can be kept constant to keep the interval at which the laser light L is irradiated 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 radial outside 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. The specific adjustment of the 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 to keep the interval at which the laser light L is irradiated constant.

[0049] In order to improve throughput by shortening the processing time (takt) of laser irradiation, it is preferable to maintain the rotation speed of the chuck 100 by 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 the parameters taking into consideration the output and pulse waveform of the laser light L. For example, if the energy of the laser light L required for peeling is the same on the radial outside and inside of the laser absorption layer P, it is necessary to increase the output by increasing the frequency of the laser light L on the outside, and to decrease the output by decreasing the frequency of the laser light L on the inside. Furthermore, when the frequency of the laser light L is changed in the laser oscillator, the pulse waveform of the laser light L also changes. Therefore, complex adjustments taking into consideration 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 have other devices besides the laser oscillator 130, such as an amplifier.

[0054] The optical system 112 has an acousto-optic modulator (AOM) 131 that redirects 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-optical modulator 131 is an optical modulator that electrically controls the intensity and position of the laser light at high speed. As shown in FIG. 11, when the laser light L1 from the laser oscillator 130 is incident on the acousto-optical modulator 131, a voltage is applied to change the refractive index of the laser light L1, thereby redirecting the laser light L1 in different directions. Specifically, the angle of the laser light L1 can be controlled by adjusting the voltage. In this embodiment, for example, the laser light L1 is redirected in two different directions, and the laser light L2 in one direction is irradiated onto the laser absorption layer P, and the laser light L3 in the other direction is not irradiated onto the laser absorption layer P. The frequency of the laser light L2 irradiated onto the laser absorption layer P can be adjusted by controlling the redirection of the laser lights L2 and L3.

[0056] In this case, the frequency of the laser light L2 irradiated to the laser absorption layer P can be adjusted by thinning out the pulses of the laser light L1 using the acousto-optical modulator 131. For example, if the redirection ratio of the laser light L2 and the laser light L3 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 to the laser absorption layer P. On the other hand, if the redirection ratio of the laser light L2 and the laser light L3 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-optical modulator 131 shown in FIG. 12(b) can be adjusted with respect to the frequency of the laser light L1 from the laser oscillator 130 shown in FIG. 12(a). Also, since the frequency of the laser light L1 is the maximum frequency that the acousto-optical 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, since the frequency of the laser light L1 oscillated from the laser oscillator 130 is not changed, the pulse waveform of the laser light L1 does not change, and the pulse waveform of the laser light L2 can be made the same as that of the laser light L1. Therefore, the frequency of the laser light L2 can be easily adjusted, the conventional complicated adjustment as described above is not necessary, and the process control of the laser processing is facilitated.

[0058] In this embodiment, the acousto-optic modulator 131 is used as the optical element, but the present invention is not limited to this. 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 method for controlling the laser light L2 when the laser emitting unit 110 irradiates the laser absorbing layer P with the laser light L2 will be described. As described above, when the irradiating position of the laser light L2 is on the radial outer side of the laser absorbing layer P, the frequency is increased, and when the irradiating position of the laser light L2 is on the inner side, the frequency is decreased.

[0060] A specific example will be described below. 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 each of 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-optical modulator 131 toward the radially outer side of the laser absorption layer P. Then, the frequency of the laser light L2 irradiated to the laser absorption layer P can be set to 100 kHz, which is the same as the frequency of the laser light L1. The output of the laser light L2 is also 40 W, which is the same as the output of the laser light L1. The energy of the laser light L2 is 400 μJ (= 40 W / 100 kHz), and peeling can be performed appropriately.

[0062] On the other hand, for the radially inner side of the laser absorbing layer P, the pulses of the laser light L1 from the laser oscillator 130 are thinned out by half in the acousto-optical modulator 131. Then, the frequency of the laser light L2 irradiated to the laser absorbing layer P can be set to 50 kHz, which is half the frequency of the laser light L1. Furthermore, by thinning out the laser light L1, the output of the laser light L2 also becomes 20 W, which is half the output of the laser light L1. Then, the energy of the laser light L2 becomes 400 μJ (= 20 W / 50 kHz), and peeling can be performed appropriately.

[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 are 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 that maintains 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 does not change, and the pulse waveform of the laser light L2 can be made the same as that of the laser light L1. Therefore, the frequency of the laser light L2 can be easily adjusted, and continuous seamless processing is possible. As a result, the process control of the laser processing becomes easy, and a stable process can be realized.

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

[0066] In the laser irradiation unit 110 of the above embodiment, the acousto-optical 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, the acousto-optical modulator 131 may be provided downstream of the attenuator 132 inside the optical system 112 as shown in Fig. 13. Alternatively, for example, the acousto-optical modulator 131 may be provided downstream of the laser oscillator 130 inside the laser head 111 as shown in Fig. 14. Furthermore, the acousto-optical 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-optical 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 of the laser oscillator 130. The attenuator 132 can adjust such output variations. In addition, 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-optical modulator 131 is 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, when 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 to 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 also not limited to the laser irradiation device 31 of the above embodiment. In the above laser irradiation device 31, the chuck 100 is freely rotatable around the θ axis and freely movable in one axis (Y axis) direction, but it may be moved in two axes (X axis and Y axis).

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

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

[0072] The moving stage 216 is configured to be movable along a rail 217 that is provided on a base 218 and extends 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 laser light L in a pulsed manner. The optical system 222 controls the intensity and position of the laser light L, or attenuates the laser light L to adjust the output. The lens 223 is a cylindrical member, and irradiates the laser light L, which is, for example, a CO2 laser light, onto the overlapped wafer T held by the chuck 210. The lens 223 is configured to be freely raised and lowered by a lifting mechanism (not shown).

[0074] For example, a galvanometer is used for the laser head 221. A plurality of galvanometer mirrors (not shown) are arranged inside the laser head 221. An f-θ lens is used for 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, and is transmitted through the second wafer W2 to be 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 movable up and down by a lifting mechanism (not shown). The configuration of the transport pad 230 is similar to the configuration of the transport pad 120 of the above embodiment.

[0076] In the laser irradiation apparatus 200, the overlapped wafer T is transferred from the transfer arm 23 to the lift pins and is adsorbed and held by 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 to the laser absorbing layer P, the laser light L is scanned in a predetermined scan range A (a square region in FIG. 17). Next, the chuck 210 is moved in the X-axis direction while the irradiation of the laser light L is stopped. In this manner, the irradiation and scanning of the laser light L and the movement of the chuck 210 are repeated to irradiate the laser light L 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 the irradiation and scanning of the laser light L and the movement of the chuck 210 are repeated in the same manner as described above to irradiate the laser light L in a line in the X-axis direction. Then, 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. However, the lens 223 may be moved relatively to the chuck 210 by moving the lens 223.

[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 suction-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 embodiment. That is, since the laser light L is irradiated to the laser absorbing layer P in a pulsed manner, the peak power of the laser light L can be increased, and as a result, peeling can be appropriately caused at the interface between the laser absorbing layer P and the second wafer W2. Moreover, since the laser light L can be irradiated at the same density in the scanning range A, the laser light L can be irradiated uniformly to the laser absorbing layer P.

[0082] In this embodiment, there may be a plurality of laser irradiation units 220. In this case, a plurality of laser beams L can be irradiated onto the laser absorption layer P, thereby shortening the processing time and further improving 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 to 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 a pulsed manner, it is possible to appropriately cause peeling 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 helical (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 rotating the chuck 210 (superimposed wafer T), 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, at least the rotation speed or frequency of the chuck 210 is controlled to adjust the irradiation interval of the laser light L.

[0087] 19, in the outer peripheral portion of the laser absorbing layer P, the chuck 210 is moved from the outside to the inside in the radial direction while rotating, and the laser light L is irradiated in a spiral shape. Then, when the rotation speed of the chuck 210 reaches an upper limit, the rotation of the chuck 210 is stopped at the center portion of the laser absorbing layer P, and the laser light L is irradiated and scanned in the scan range A. Note that the scan range A is illustrated as a square, but the shape of the scan range A is not limited thereto. For example, the scan range A may be a circle.

[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 entire surface of the laser absorbing layer P may be irradiated with the laser light L all 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 arranged 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 FIG. 22 and FIG. 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 member 250 is arranged at a plurality of locations, for example, three locations, on a concentric circle of the chuck 100. The holding member 250 is configured to be movable forward and backward so as to contact or separate from the second wafer W2 by a moving mechanism 251. 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 at a position corresponding to the holding member 250 in the guide portion 240, 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 suppress misalignment and slipping of the second wafer W2. In particular, when the gap between the vertical portion 241 and the second wafer W2 is within the allowable range of misalignment, the guide portion 240 is useful. However, providing both the guide portion 240 and the holding member 250 enhances the effects of centering the overlapped wafer T and preventing misalignment and slipping of the second wafer W2.

[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 not in contact with the second wafer W2. Thereafter, 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 in contact with the side surfaces of the second wafer W2, and these holding members 250 hold the second wafer W2.

[0095] Here, in the case where the guide portion 240 and the holding member 250 are not present, when the laser light L is irradiated in a spiral shape from the outside to the inside in the radial direction of the laser absorbing layer P, as the peeling progresses, a centrifugal force acts on the second wafer W2 because the chuck 100 is rotating, and the second wafer W2 is shifted from the laser absorbing layer P, and during the laser processing, the laser light L may be irradiated to a position other than the processing target position. In addition, the peeled second wafer W2 may slide off. In this regard, in this embodiment, the second wafer W2 is held by the holding member 250, so that such a shift or slide 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, during the movement of the chuck 100, an inertial force acts on the second wafer W2, 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 sucked and held at an appropriate position. Therefore, in this embodiment, the second wafer W2 is held by the holding member 250 even during the movement of the chuck 100, to prevent the second wafer W2 from being displaced.

[0097] The configuration of the holding member for holding 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 by pinching the upper and side surfaces of the second wafer W2 from the sides of the second wafer W2. The holding member may 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 upper surface of the second wafer W2.

[0098] The wafer processing system 1 in the above embodiment includes the cleaning device 32, but the wafer processing system 1 may further include an etching device (not shown). The etching device etches the surface W1a of the first wafer W1 after peeling, specifically, the surface of the laser absorbing layer P. For example, after the cleaning device 32 scrubs the surface of the laser absorbing layer P, a chemical liquid (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 device 32 or the etching device.

[0099] The wafer processing system 1 of the above embodiment may also have a CMP device (not shown). In the CMP device, the surface W1a of the first wafer W1 after peeling, 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 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 the laser light L to peel off the second wafer W2 from the laser absorbing layer P. However, for example, as shown in FIG. 24, the laser absorbing layer P may be peeled off so that the laser absorbing layer P remains on the second wafer W2.

[0101] In this 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, that is, 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 for peeling 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, or the like.

[0103] Next, while the back surface W2b of the second wafer W2 is held by suction on 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] In this embodiment, the same effects as those of the above embodiment can be obtained. That is, since the laser light L is irradiated to the laser absorbing layer P in a pulsed manner, the peak power of the laser light L can be increased, and as a result, peeling can be appropriately 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 a TSV (Through-Silicon Via) on the second wafer W2 in a subsequent semiconductor manufacturing process, for example.

[0105] In this embodiment, the surface of the laser absorbing layer P on the second wafer W2 after peeling may be scrubbed and then CMP processed by the above-mentioned CMP device. In this case, the surface of the laser absorbing layer P can be flattened. Then, 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 wafers T are processed will be described with reference to Figs. 25 to 28.

[0107] A case where the overlapped wafer T shown in FIG. 25 is processed will be described. As shown in FIG. 25(a), the laser absorption 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 absorption layer P1 is, for example, an oxide film (SiO2 film). That is, the second wafer W2, which is Si, the laser absorption layer P1, which is an SiO2 film, and the Si film S, which is Si, are laminated in this order. Note that the laser absorption layer P1 may be formed of a film other than the 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) The first wafer W1 has a surface film F1 formed on the surface W1a thereof, and this surface film F1 and the surface film F2 are bonded together.

[0110] Next, in the laser irradiation device 31 of the wafer processing system 1, as shown in Fig. 25(d), 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, the laser light L causes peeling at the interface between the laser absorbing layer P1 and the Si film S.

[0111] Next, while the back surface W2b of the second wafer W2 is 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, 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, to cause peeling at the interface between the second wafer W2 and the laser absorbing layer P1.

[0113] A case of processing the overlapped wafer T shown in Fig. 26 will be described. 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 laminated in this order from the second wafer W2 side between the second wafer W2 and the device layer D2.

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

[0115] Next, the first wafer W1 and the second wafer W2 are bonded together as shown in Fig. 26(c) The device layer D1 and the 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] Next, in the laser irradiation device 31 of the wafer processing system 1, as shown in Fig. 26(d), 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, the laser light L causes peeling at the interface between the laser absorbing layer P2 and the Si film S.

[0117] Next, while the back surface W2b of the second wafer W2 is adsorbed and held by the transfer pad 120, the transfer pad 120 is raised as shown in Fig. 26(e) 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 absorb the laser light L, i.e., the peeling position of the laser absorbing layer P1, in the same manner as in the case shown in Fig. 24, to cause peeling at the interface between the second wafer W2 and the laser absorbing layer P2.

[0118] A case of processing the overlapped wafer T shown in Fig. 27 will be described. As shown in Fig. 27(a) and (b), between the second wafer W2 and the device layer D2, 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 laminated in this order from the second wafer W2 side.

[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, the laser irradiation unit 110 irradiates the interface between the laser absorbing layer P3 and the second wafer W2 with pulsed laser light L as shown in Fig. 27(d). Then, the laser light L causes peeling at the interface between the laser absorbing layer P3 and the second wafer W2.

[0122] Next, while the back surface W2b of the second wafer W2 is held by suction on the transfer pad 120, the transfer pad 120 is raised as shown in FIG. 27(e) to peel off the second wafer W2 from the laser absorption layer P3.

[0123] The processing of the overlapped wafer T shown in Fig. 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 Fig. 28(a), a device layer D1 and a surface film F1 are formed on the surface W1a of the first wafer W1. That is, the first wafer W1 is a Si-nMOS.

[0124] Next, as shown in Fig. 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 laminated 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) In particular, 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, while the back surface W2b of the second wafer W2 is held by suction on the transfer pad 120, the transfer pad 120 is raised as shown in Fig. 28(e) to peel off 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 manner as in the case shown in Fig. 24, to cause peeling 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 for 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 reflectance 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 in the laser absorption layer P, but even if there is laser light L that has not been completely 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] Moreover, the laser light L reflected by the reflective film R is absorbed by the laser absorption layer P. Therefore, the peeling efficiency of the second wafer W2 can be improved.

[0132] The embodiments disclosed herein should be considered as illustrative and not restrictive in all respects. The above-described embodiments may be omitted, substituted, or modified in various forms 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 the steps of: 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 front surface side, The first substrate and the second substrate are bonded to each other by 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. The substrate processing method according to claim 1 , wherein a first device layer is formed between the surface of the first substrate and the first surface film.

3. 3. The substrate processing method according to claim 1, wherein the laser absorption layer is made of SiGe.

4. 3. The substrate processing method according to claim 1, wherein the laser absorption layer is made of Ge.

5. irradiating the laser absorbing layer with the laser light from the outer side to the inner side 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 of the first substrate and the second substrate in the laminated substrate.

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

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 the step of 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 peeled off.

10. The laser light is irradiated onto the laminated substrate while rotating the laminated substrate; 10. The substrate processing method according to claim 1, wherein a rotation speed of the laminated substrate is faster when the laser light is irradiated to an inner side of the laser absorption layer in the radial direction than when the laser light is irradiated to an outer side of the laser absorption layer in the radial direction, and a frequency of the laser light irradiated to the outer side of the laser absorption layer in the radial direction is higher than a frequency of the laser light irradiated to the inner side.

11. the first surface film is an oxide film; The substrate processing method according to any one of claims 1 to 10, wherein the second surface film is an oxide film.

12. 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 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 front surface side, The first substrate and the second substrate are bonded to each other by the first surface film and the second surface film, a holding portion that holds a rear surface of the first substrate; a laser irradiation unit that irradiates the laser absorption layer with pulsed laser light from a 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 transport unit configured to peel the second substrate from the first substrate between the laser absorption layer and the second substrate and transfer the second device layer and the second surface film to the first substrate.

13. The substrate processing system of claim 12 , wherein a first device layer is formed between the surface of the first substrate and the first surface film.

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

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