Substrate processing method and substrate processing apparatus

Abstract

A method for transferring a device layer formed on the surface of a second substrate to a first substrate in a superposed substrate formed by bonding the first substrate and the second substrate, in which laser is pulsed onto a laser absorption layer formed between the second substrate and the device layer from the back side of the second substrate.

Description

Technical Field

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

[0002] A method for manufacturing a semiconductor device is disclosed in Patent Document 1. The method for manufacturing the semiconductor device includes: a heating step of locally heating a peeling oxide film by irradiating CO 2 laser from the back surface of a semiconductor substrate; and a transfer step of generating peeling at the boundary between the peeling oxide film and / or between the peeling oxide film and the semiconductor substrate to transfer a semiconductor element to a transfer target substrate.

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2007-220749 Summary of the Invention

[0006] Problems to be Solved by the Invention

[0007] In the technology related to the present disclosure, a device layer formed on the surface of a second substrate is appropriately transferred to a first substrate in a laminated substrate formed by bonding the first substrate and the second substrate.

[0008] Solutions to the Problems

[0009] One aspect of the present disclosure is a method of transferring a device layer formed on the surface of a second substrate to a first substrate in a laminated substrate formed by bonding the first substrate and the second substrate. In the method, a laser is pulsed on a laser absorption layer formed between the second substrate and the device layer from the back side of the second substrate.

[0010] Effects of the Invention

[0011] According to the present disclosure, a device layer formed on the surface of a second substrate can be appropriately transferred to a first substrate in a laminated substrate formed by bonding the first substrate and the second substrate. Brief Description of the Drawings

[0012] Figure 1 It is an explanatory diagram comparing the powers of lasers in the case of using pulsed waves and continuous waves.

[0013] Figure 2 It is a side view schematically showing the outline of the structure of a laminated wafer being processed in a wafer processing system.

[0014] Figure 3 It is a top view schematically showing the outline of the structure of a wafer processing system.

[0015] Figure 4 It is a side view showing an outline of the structure of the laser irradiation device according to the present embodiment.

[0016] Figure 5 It is a top view showing an outline of the structure of the laser irradiation device according to the present embodiment.

[0017] Figure 6 It is an explanatory diagram showing a situation where a laser is irradiated onto a laser absorption layer in the present embodiment.

[0018] Figure 7 It is an explanatory diagram showing a situation where a laser is irradiated onto a laser absorption layer in the present embodiment.

[0019] Figure 8 It is an explanatory diagram showing a situation where a laser is irradiated onto a laser absorption layer in a modified example of the present embodiment.

[0020] Figure 9 It is an explanatory diagram showing a situation where a second wafer is peeled off from the laser absorption layer.

[0021] Figure 10 It is an explanatory diagram schematically showing an outline of the structure of a laser irradiation unit according to another embodiment.

[0022] Figure 11 It is an explanatory diagram showing a situation where the frequency of a laser is changed by an acousto-optic modulator in another embodiment.

[0023] Figure 12 It is an explanatory diagram showing a situation where the frequency of a laser is changed by an acousto-optic modulator in another embodiment.

[0024] Figure 13 It is an explanatory diagram schematically showing an outline of the structure of a laser irradiation unit according to another embodiment.

[0025] Figure 14 It is an explanatory diagram schematically showing an outline of the structure of a laser irradiation unit according to another embodiment.

[0026] Figure 15 It is a side view showing an outline of the structure of the laser irradiation device according to another embodiment.

[0027] Figure 16 It is a top view showing an outline of the structure of the laser irradiation device according to another embodiment.

[0028] Figure 17 It is an explanatory diagram showing a situation where a laser is irradiated onto a laser absorption layer in another embodiment.

[0029] Figure 18 It is an explanatory diagram showing a case where a laser is irradiated onto a laser absorption layer in other embodiments.

[0030] Figure 19 It is an explanatory diagram showing a case where a laser is irradiated onto a laser absorption layer in other embodiments.

[0031] Figure 20 It is a side view showing an outline of the structure of a laser irradiation device according to other embodiments.

[0032] Figure 21 It is a side view showing an outline of the structure of a guiding portion.

[0033] Figure 22 It is a side view showing an outline of the structure of a holding member.

[0034] Figure 23 It is a top view showing an outline of the structures of a guiding portion and a holding member.

[0035] Figure 24 It is an explanatory diagram showing a case where a device layer formed on the surface of a second wafer is transferred onto a first wafer in other embodiments.

[0036] Figure 25 It is an explanatory diagram showing a case where a device layer formed on the surface of a second wafer is transferred onto a first wafer in other embodiments.

[0037] Figure 26 It is an explanatory diagram showing a case where a device layer formed on the surface of a second wafer is transferred onto a first wafer in other embodiments.

[0038] Figure 27 It is an explanatory diagram showing a case where a device layer formed on the surface of a second wafer is transferred onto a first wafer in other embodiments.

[0039] Figure 28 It is an explanatory diagram showing a case where a device layer formed on the surface of a second wafer is transferred onto a first wafer in other embodiments.

[0040] Figure 29 It is a side view showing an outline of the structure of overlapping wafers in other embodiments. Detailed implementation manners

[0041] In recent years, in the manufacturing process of LEDs, so-called laser lift-off is performed in which a GaN (gallium nitride) - based compound crystal layer (material layer) is lifted off from a sapphire substrate using a laser. Against the backdrop of performing such laser lift-off, it can be cited that since the sapphire substrate is transparent to short-wavelength lasers (e.g., UV light), short-wavelength lasers with a high absorption rate for the absorption layer can be used, and the range of laser selection is also large.

[0042] On the other hand, in the manufacturing process of semiconductor devices, a device layer formed on the surface of one substrate (a semiconductor such as a silicon substrate) is transferred to another substrate. Silicon substrates are generally transparent to lasers in the NIR (near-infrared) region, but the absorption layer is also transparent to NIR lasers, so there is a risk of damage to the device layer. Therefore, in order to perform laser lift-off in the manufacturing process of semiconductor devices, lasers in the FIR (far-infrared) region are used.

[0043] Generally, for example, lasers with wavelengths in the FIR can be used by CO 2 lasers. In the method described in Patent Document 1 above, by irradiating a peeling oxide film with CO 2 lasers, peeling is generated at the boundary between the peeling oxide film and the substrate.

[0044] Here, the inventors of the present invention have conducted in-depth research and learned that peeling may not occur only by irradiating with CO 2 lasers. That is, it was found that the main cause of peeling is not the energy of the CO 2 lasers, but the peak power (the maximum intensity of the laser). For example, as Figure 1 shown, in the case of continuously oscillating CO 2 lasers (when using a continuous wave), it is difficult to increase the peak power, and peeling may not occur. On the other hand, in the case of pulse-oscillating CO 2 lasers (when using a pulse wave), the peak power can be increased, and thus peeling can occur. In addition, in the present disclosure, the laser obtained by pulse-oscillating CO 2 lasers is a so-called pulsed laser, and its power repeats between 0 (zero) and the maximum value.

[0045] In addition, when continuously oscillating CO 2 lasers, the thermal influence is large, so stable laser lift-off cannot be performed, and the device layer may also be damaged by heat. Therefore, from this perspective, CO 2 lasers can also be irradiated in a pulsed manner.

[0046] As described above, in order to peel the substrate from the peeling oxide film (device layer), it is necessary to pulse-irradiate the peeling oxide film with CO 2Laser. However, in the method of Patent Document 1, pulsed laser is not considered at all, nor is such a disclosure given. Therefore, there is room for improvement in the conventional transfer method of the device layer.

[0047] In the technology related to the present disclosure, in a stacked substrate formed by bonding a first substrate and a second substrate, a device layer formed on the surface of the second substrate is appropriately transferred to the first substrate. Hereinafter, a wafer processing system including a laser irradiation device as a substrate processing device and a wafer processing method as a substrate processing method according to the present embodiment will be described with reference to the drawings. In addition, in the present specification and the drawings, elements having substantially the same functional structure are denoted by the same reference numerals, and thus redundant description is omitted.

[0048] In the wafer processing system 1 described later according to the present embodiment, as Figure 2 shown, processing is performed on a stacked wafer T as a stacked substrate formed by bonding a first wafer W1 as a first substrate and a second wafer W2 as a second substrate. Hereinafter, the surface of the first wafer W1 on the side bonded to the second wafer W2 will be referred to as surface W1a, and the surface on the side opposite to surface W1a will be referred to as back surface W1b. Similarly, the surface of the second wafer W2 on the side bonded to the first wafer W1 will be referred to as surface W2a, and the surface on the side opposite to surface W2a will be referred to as back surface W2b.

[0049] The first wafer W1 is, for example, 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 stacked in the described order from the surface W1a side. The device layer D1 includes a plurality of devices. As the surface film F1, for example, an oxide film (SiO 2 film, TEOS film), SiC film, SiCN film, or adhesive, etc. can be cited. In addition, there is also a case where the device layer D1 and the surface film F1 are not formed on the surface W1a.

[0050] The second wafer W2 is also, for example, a semiconductor wafer such as a silicon substrate. On the surface W2a of the second wafer W2, a laser absorption layer P, a device layer D2, and a surface film F2 are overlapped in the described order from the surface W2a side. The laser absorption layer P absorbs the laser emitted from the laser irradiation unit 110 as described later. The laser absorption layer P uses, for example, an oxide film (SiO 2(membrane), but it only needs to absorb the laser, and there is no particular limitation. 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. Moreover, the surface film F1 of the first wafer W1 is bonded to the surface film F2 of the second wafer W2. In addition, the position of the laser absorption layer P is not limited to the above-described embodiment. For example, it may be formed between the device layer D2 and the surface film F2. Further, there may be a case where the device layer D2 and the surface film F2 are not 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.

[0051] As Figure 3 shown, the wafer processing system 1 has a structure in which the loading / unloading block 10, the transfer block 20, and the processing block 30 are connected integrally. The loading / unloading block 10 and the processing block 30 are provided around the transfer block 20. Specifically, the loading / unloading block 10 is arranged on the negative Y-axis side of the transfer block 20. The laser irradiation device 31, which will be described later, of the processing block 30 is arranged on the negative X-axis side of the transfer block 20, and the cleaning device 32, which will be described later, is arranged on the positive X-axis side of the transfer block 20.

[0052] The loading / unloading block 10 is used for, for example, loading and unloading the cassettes Ct, Cw1, and Cw2 with respect to the outside, and the cassettes Ct, Cw1, and Cw2 can accommodate a plurality of stacked wafers T, a plurality of first wafers W1, and a plurality of second wafers W2, respectively. A cassette mounting table 11 is provided in the loading / unloading block 10. In the illustrated example, a plurality of, for example, three cassettes Ct, Cw1, and Cw2 are freely mounted in a row along the X-axis direction on the cassette mounting table 11. In addition, the number of the cassettes Ct, Cw1, and Cw2 mounted on the cassette mounting table 11 is not limited to this embodiment and can be arbitrarily determined.

[0053] A wafer transfer device 22 is provided in the transfer block 20, and the wafer transfer device 22 is configured to be 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 for holding and transferring the stacked 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, and to rotate about a horizontal axis and a vertical axis. In addition, the structure of the transfer arm 23 is not limited to this embodiment, and any structure can be adopted. Moreover, the wafer transfer device 22 is configured to be able to transfer the stacked 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.

[0054] 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. In addition, the structure of the laser irradiation device 31 will be described later.

[0055] The cleaning device 32 cleans the surface of the laser absorption 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 absorption layer P to brush the surface. In addition, the surface can also be cleaned using pressurized cleaning liquid. Further, the cleaning device 32 may have a structure for cleaning the back surface W1b together with the surface W1a side of the first wafer W1.

[0056] In the above-described wafer processing system 1, a control device 40 is provided as a control unit. The control device 40 is, for example, a computer and has a program storage unit (not shown). A program for controlling the processing of the stacked wafers T in the wafer processing system 1 is stored in the program storage unit. In addition, a program for controlling the operation of the drive systems of the above-described various processing devices, transfer devices, etc. to implement the wafer processing described later in the wafer processing system 1 is also stored in the program storage unit. Further, the above program may be a program recorded on a computer-readable storage medium H and installed in the control device 40 from the storage medium H.

[0057] Next, the above-described laser irradiation device 31 will be described.

[0058] As Figure 4 and Figure 5 shown, the laser irradiation device 31 has a chuck 100 as a holding unit that holds the stacked wafers T through the upper surface. The chuck 100 adsorbs and holds the entire back surface W1b of the first wafer W1. In addition, the chuck 100 may also adsorb and hold a part of the back surface W1b. Lift pins (not shown) for supporting the stacked wafers T from below and lifting and lowering them are provided on the chuck 100. The lift pins pass through through-holes (not shown) formed so as to penetrate the chuck 100 and are configured to be able to move up and down freely.

[0059] The chuck 100 is supported by a slider stage 102 via an air bearing 101. A rotation mechanism 103 is provided on the lower surface side of the slider stage 102. The rotation mechanism 103 has, for example, a motor built therein as a drive source. The chuck 100 is configured to be rotatable about the θ axis (vertical axis) via the air bearing 101 by the rotation mechanism 103. The slider stage 102 is configured to be movable along a guide rail 105 provided on a base 106 and extending in the Y-axis direction by a moving mechanism 104 provided on its lower surface side. In addition, there is no particular limitation on the drive source of the moving mechanism 104, and for example, a linear motor is used.

[0060] A laser irradiation unit 110 is provided above the suction cup 100. The laser irradiation unit 110 includes a laser head 111, an optical system 112, and a lens 113. The laser head 111 oscillates laser light in a pulsed manner. The optical system 112 controls the intensity and position of the laser light or adjusts the output by attenuating the laser light. The lens 113 is a cylindrical member for irradiating the overlapped wafer T held by the suction cup 100 with laser light. In this embodiment, the laser light is CO 2 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. 2 The wavelength of the laser light is, for example, 8.9 μm to 11 μm. The lens 113 is configured to be able to be raised and lowered by a lifting mechanism (not shown).

[0061] In addition, a conveying pad 120 as a conveying unit is provided above the suction cup 100. The conveying pad 120 is configured to be freely raised and lowered by a lifting mechanism (not shown). In addition, the conveying pad 120 has an adsorption surface for the second wafer W2. Moreover, the conveying pad 120 conveys the second wafer W2 between the suction cup 100 and the conveying arm 23. Specifically, after the suction cup 100 is moved to the bottom of the conveying pad 120 (the handover position with the conveying arm 23), the conveying pad 120 adsorbs and holds the back side W2b of the second wafer W2 to peel it from the first wafer W1. Next, the peeled second wafer W2 is handed over from the conveying pad 120 to the conveying arm 23 and is carried out from the laser irradiation device 31. In addition, the conveying pad 120 can be configured to flip the front and back sides of the wafer by a flipping mechanism (not shown).

[0062] exist Figure 5 In the laser irradiation device 31 shown in FIG. 1 , the transfer arm 23 accesses the transfer pad 120 from the positive direction side of the X axis. Figure 5 The laser irradiation device 31 shown is rotated 90 degrees counterclockwise, and the transfer arm 23 accesses the transfer pad 120 from the negative side of the Y axis.

[0063] Furthermore, when the overlapped wafer T is carried into the laser irradiation device 31, the overlapped wafer T is delivered from the transport arm 23 to the lifting pins, and the lifting pins are lowered to place the overlapped wafer T on the suction cup 100. Furthermore, when the peeled second wafer W2 is carried out from the laser irradiation device 31, the overlapped wafer T placed on the suction cup 100 is raised by the lifting pins and delivered from the lifting pins to the transport arm 23.

[0064] Next, wafer processing using the wafer processing system 1 configured as above will be described. In the present embodiment, the first wafer W1 and the second wafer W2 are bonded in advance to form a superimposed wafer T in a bonding device (not shown) outside the wafer processing system 1 .

[0065] First, place the cassette Ct containing a plurality of overlapping wafers T on the cassette stage 11 of the loading / unloading block 10.

[0066] Next, take out the overlapping wafers T in the cassette Ct by the wafer transfer device 22 and transfer them to the laser irradiation device 31. In the laser irradiation device 31, the overlapping wafer T is transferred from the transfer arm 23 to the lift pins, and the suction cup 100 adsorbs and holds the overlapping wafer T. Next, move the suction cup 100 to the processing position by the moving mechanism 104. This processing position is a position where the laser irradiation unit 110 can irradiate the overlapping wafer T (laser absorption layer P) with laser light.

[0067] Next, as Figure 6 and Figure 7 shown, irradiate the laser absorption layer P, more specifically, the boundary between the laser absorption layer P and the second wafer W2, with pulsed laser light L (CO 2 laser) from the laser irradiation unit 110. 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 absorption layer P. Moreover, due to this laser light L, delamination occurs at the boundary between the laser absorption layer P and the second wafer W2. In addition, almost all of the laser light L is absorbed by the laser absorption layer P and does not reach the device layer D2. Therefore, damage to the device layer D2 can be suppressed.

[0068] When irradiating the laser absorption layer P with the laser light L, rotate the suction cup 100 (overlapping wafer T) by the rotation mechanism 103 and move the suction cup 100 in the Y-axis direction by the moving mechanism 104. Then, irradiate the laser absorption layer P with the laser light L from the radially outer side toward the radially inner side. As a result, the irradiation is performed in a spiral shape from the outside to the inside. In addition, Figure 7 the black arrow shown indicates the rotation direction of the suction cup 100.

[0069] The irradiation start position of the laser light L is preferably a position between the outer peripheral end Ea of the second wafer W2 and the bonding end Eb between the first wafer W1 and the second wafer W2 in the overlapping wafer T. In this case, for example, in the overlapping wafer T, even when the centers of the first wafer W1 and the second wafer W2 are deviated and eccentric, the eccentricity can be absorbed to appropriately irradiate the laser absorption layer P with the laser light L.

[0070] In addition, as Figure 8 shown, in the laser absorption layer P, the laser light L can be irradiated in a concentric and annular shape. However, in this case, since the rotation of the suction cup 100 and the movement of the suction cup 100 in the Y direction are alternately performed, irradiating the laser light L in a spiral shape as described above can shorten the irradiation time and improve the productivity.

[0071] In addition, in the laser absorption layer P, the laser L may also be irradiated from the radially inner side toward the radially outer side. However, in this case, since the inner side of the laser absorption layer P is peeled off first, the stress generated by the peeling is directed toward the radially outer side, and sometimes the portion of the outer side that has not been irradiated with the laser L is also peeled off. In this regard, in the case where the laser L is irradiated from the radially outer side toward the radially inner side as described above, the stress generated by the peeling can be released to the outside, so that it is easier to control the peeling. In addition, by appropriately controlling the peeling, it is also possible to suppress roughness of the peeling surface.

[0072] In addition, in the present embodiment, the chuck 100 is rotated when the laser L is irradiated onto the laser absorption layer P, but the lens 113 may be moved to rotate the lens 113 relative 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.

[0073] In this way, in the laser irradiation device 31, the laser L is irradiated onto the laser absorption layer P. Moreover, since the laser L is irradiated in a pulsed manner, the peak power of the laser L can be increased. Therefore, as described above Figure 1 it is possible to generate peeling at the boundary between the laser absorption layer P and the second wafer W2, and thus the second wafer W2 can be appropriately peeled off from the laser absorption layer P.

[0074] Next, the chuck 100 is moved to the transfer position by the moving mechanism 104. Moreover, as Figure 9 shown in (a) of, the back surface W2b of the second wafer W2 is adsorbed and held by the transfer pad 120. After that, as Figure 9 shown in (b) of, while the transfer pad 120 adsorbs and holds the second wafer W2, the transfer pad 120 is raised to peel the second wafer W2 from the laser absorption layer P. At this time, as described above, peeling is generated at the boundary between the laser absorption layer P and the second wafer W2 by irradiating the laser L, so that the second wafer W2 can be peeled off from the laser absorption layer P without applying a large load.

[0075] 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. In addition, before transferring the second wafer W2 taken out from the laser irradiation device 31 to the cassette Cw2, the second wafer W2 may be transferred to the cleaning device 32 to clean its peeling surface, that is, the surface W2a. In this case, the front and back surfaces of the second wafer W2 can be flipped by the transfer pad 120 and transferred to the transfer arm 23.

[0076] On the other hand, the first wafer W1 held by the suction cup 100 is lifted by the lifting pins, and the first wafer W1 is transferred to the transfer arm 23 and transferred to the cleaning device 32. In the cleaning device 32, the surface of the laser absorption layer P, which is the peeling surface, is scrubbed. In addition, in the cleaning device 32, the back surface W1b of the first wafer W1 can be cleaned together with the surface of the laser absorption layer P. Additionally, a cleaning unit for cleaning the surface of the laser absorption layer P and a cleaning unit for cleaning the back surface W1b of the first wafer W1 can be provided separately.

[0077] After that, the first wafer W1 that has undergone all the processes is transferred to the cassette Cw1 on the cassette stage 11 by the wafer transfer device 22. By doing so, a series of wafer processes in the wafer processing system 1 are completed.

[0078] According to the above embodiment, in the laser irradiation device 31, the laser L is pulsed onto the laser absorption layer P, so that the peak power of the laser L can be increased. As a result, peeling can be generated at the boundary between the laser absorption layer P and the second wafer W2. In addition, when the laser L is pulsed, the thermal influence is smaller than when a continuous wave is used, and stable laser peeling can be performed. Therefore, the second wafer W2 can be appropriately peeled from the laser absorption layer P, and thus the device layer D2 can be transferred onto the first wafer W1.

[0079] Here, in order to make the peeling between the first wafer W1 and the second wafer W2 proceed uniformly within the wafer surface, it is preferable to fix the interval of irradiating the laser L, that is, the interval of the pulses. However, in order to fix the interval of the pulses, when the suction cup 100 (the stacked wafer T) rotates, the rotation speed of the suction cup 100 becomes faster as the laser L moves from the radially outer side to the radially inner side. In this case, when the rotation speed of the suction cup 100 reaches the upper limit, the interval of the laser L becomes smaller as the irradiation position of the laser L moves toward the radially inner side, and sometimes the laser L may overlap at the center. Therefore, it is necessary to adjust the irradiation interval of the laser L. For example, there are the following two methods.

[0080] The first method is a method of controlling the rotation speed of the suction cup 100. That is, when the irradiation position of the laser 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 L is on the inner side, the rotation speed is accelerated. In addition, the specific adjustment of the rotation speed is arbitrarily set according to the frequency of the laser L. In this case, the rotation speed of the suction cup 100 can be fixed to fix the interval of irradiating the laser L.

[0081] The second method is a method for controlling the frequency of the laser L. That is, when the irradiation position of the laser L is radially outside the laser absorption layer P, the frequency is increased, and when the irradiation position of the laser L is inside, the frequency is decreased. In addition, the specific adjustment of this frequency is arbitrarily set according to the rotation speed of the chuck 100. In this case, it is also possible to fix the rotation speed of the chuck 100 to fix the interval of irradiating the laser L.

[0082] In addition, in order to shorten the processing time (cycle) of laser irradiation to improve productivity, it is preferable to use a high-frequency laser L and maintain the rotation speed of the chuck 100 in the first method.

[0083] In addition, the above first method and second method can be used in combination. In this case, at a position radially outside, the rotation speed of the chuck 100 is slowed down, and the frequency of the laser L is increased. On the other hand, at a position radially inside, the rotation speed of the chuck 100 is accelerated, and the frequency of the laser L is decreased.

[0084] Here, when controlling the frequency of the laser L in the second method, for example, when controlling the frequency of the laser L in the laser oscillator of the laser head 111, it is necessary to consider the output and pulse waveform of the laser L to adjust the parameters. For example, when the energy of the laser L required for peeling in the radially outer side and the radially inner side of the laser absorption layer P is the same, when increasing the frequency of the laser L on the outer side, the output needs to be increased, and when decreasing the frequency of the laser L on the inner side, the output needs to be decreased. And when changing the frequency of the laser L in the laser oscillator, the pulse waveform of this laser L also changes. Therefore, it is necessary to perform complex adjustments considering the output and pulse waveform of the laser L, and it is difficult to perform process control of laser processing.

[0085] Therefore, in the present embodiment, an acousto-optic modulator as an optical element is used to control the frequency of the laser L. As described above, the laser irradiation unit 110 includes a laser head 111, an optical system 112, and a lens 113.

[0086] As Figure 10 shown, the laser head 111 has a laser oscillator 130 that oscillates the laser in a pulsed manner. The frequency of the laser oscillated from the laser oscillator 130 is the highest frequency that can be controlled by the acousto-optic modulator 131 described later. In addition, the laser head 111 may further have devices other than the laser oscillator 130, such as an amplifier.

[0087] The optical system 112 includes an acousto-optic modulator (AOM) 131 that deflects the laser from the laser oscillator 130 in different directions, and an attenuator 132 as an attenuator that attenuates the laser from the laser oscillator 130 to adjust the output of the laser. The acousto-optic modulator 131 and the attenuator 132 are arranged in the described order from the laser oscillator 130 side.

[0088] The acousto-optic modulator 131 is an optical modulator that electrically controls the intensity and position of a laser at high speed. As Figure 11 shown, when the laser L1 from the laser oscillator 130 is incident on the acousto-optic modulator 131, a voltage is applied to change the refractive index of the laser L1, thereby deflecting the laser L1 in different directions. Specifically, the deflection angle of the laser L1 can be controlled by adjusting the voltage. In the present embodiment, for example, the laser L1 is deflected in two different directions, and the laser L2 in one direction is irradiated on the laser absorption layer P, while the laser L3 in the other direction is not irradiated on the laser absorption layer P. By controlling the deflection of the lasers L2 and L3, the frequency of the laser L2 irradiated on the laser absorption layer P can be adjusted.

[0089] In this case, by using the acousto-optic modulator 131 to perform interval elimination on the pulses of the laser L1, the frequency of the laser L2 irradiated on the laser absorption layer P can be adjusted. For example, if the deflection rates of the lasers L2 and L3 with respect to the laser L1 are set to 100:0 at a certain timing, the laser L1 is directly irradiated on the laser absorption layer P as the laser L2. On the other hand, if the deflection rates of the lasers L2 and L3 with respect to the laser L1 are set to 0:100 at another timing, the laser L2 is 0 (zero), and the laser L2 is not irradiated on the laser absorption layer P. In this case, it is possible to adjust Figure 12 the frequency of the laser L1 from the laser oscillator 130 shown in (a) of Figure 12 the frequency of the laser L2 after deflection by the acousto-optic modulator 131 shown in (b) of Figure 12 In addition, as described above, the frequency of the laser L1 is the highest frequency that the acousto-optic modulator 131 can control, so the frequency of the laser L2 can be adjusted arbitrarily. Furthermore, Figure 12 the horizontal axis of Figure 12 represents time, and the vertical axis represents the intensity of the laser L2. That is, Figure 12 the density in the graph of Figure 12 represents the frequency of the laser L2.

[0090] Moreover, in this case, since the frequency of the laser L1 oscillated from the laser oscillator 130 is not changed, the pulse waveform of the laser L1 remains unchanged, and the pulse waveform of the laser L2 can also be the same as the pulse waveform of the laser L1. Therefore, the frequency of the laser L2 can be easily adjusted without performing the conventional complex adjustment as described above, and thus the process control of the laser processing becomes easy.

[0091] In addition, in the present embodiment, the acousto-optic modulator 131 is used as the optical element, but it is not limited thereto. For example, an electro-optic modulator (EOM) can also be used as the optical element. In addition, optical deflectors such as an acousto-optic deflector (AOD) and an electro-optic deflector (EOD) can also be used.

[0092] Next, a method for controlling the laser L2 when the laser L2 is irradiated from the laser irradiation unit 110 to the laser absorption layer P will be described. As described above, when the irradiation position of the laser L2 is outside the radial direction of the laser absorption layer P, the frequency is increased, and when the irradiation position of the laser L2 is inside, the frequency is decreased.

[0093] Hereinafter, a specific example will be used for explanation. In addition, the numerical values in this specific example are for illustration only, and the present disclosure is not limited to these numerical values. For example, the energy required for peeling both the outside and the inside in the radial direction of the laser absorption layer P is set to 400 μJ. The required frequency of the laser L2 on the outside in the radial direction of the laser absorption layer P is set to 100 kHz, and the required frequency of the laser on the inside is set to 50 kHz. The frequency of the laser L1 from the laser oscillator 130 is 100 kHz, and the output is 40 W.

[0094] In this case, for the outside in the radial direction of the laser absorption layer P, the pulses of the laser L1 from the laser oscillator 130 are not removed at intervals in the acousto-optic modulator 131. Thus, the frequency of the laser L2 irradiated to the laser absorption layer P can be set to 100 kHz, which is the same as the frequency of the laser L1. In addition, the output of the laser L2 also becomes 40 W, which is the same as the output of the laser L1. Moreover, the energy of the laser L2 becomes 400 μJ (= 40 W / 100 kHz), and peeling can be appropriately performed.

[0095] On the other hand, for the inside in the radial direction of the laser absorption layer P, half of the pulses of the laser L1 from the laser oscillator 130 are removed at intervals in the acousto-optic modulator 131. Thus, the frequency of the laser L2 irradiated to the laser absorption layer P can be set to 50 kHz, which is half of the frequency of the laser L1. In addition, by removing the laser L1 at intervals, the output of the laser L2 also becomes half of the output of the laser L1, that is, 20 W. Moreover, the energy of the laser L2 becomes 400 μJ (= 20 W / 50 kHz), and peeling can be appropriately performed.

[0096] In this way, the rotation speed of the chuck 100 is controlled according to the frequency and irradiation position of the laser L2 so that the interval of the pulses is fixed. Moreover, at the center of the laser absorption layer P, the highest rotation speed of the chuck 100 is maintained, and the acousto-optic modulator 131 adjusts the frequency of the laser L2 according to this highest rotation speed. As a result, laser processing that maximally maintains the high rotation speed of the chuck 100 and the high frequency of the laser L2 can be performed, and high-productivity laser processing can be achieved.

[0097] Moreover, in this case, since the frequency of the laser beam L1 from the laser oscillator 130 is not changed, the pulse waveform of the laser beam L1 remains unchanged, and the pulse waveform of the laser beam L2 can also be the same as that of the laser beam L1. Therefore, the frequency of the laser beam L2 can be easily adjusted, enabling continuous seamless processing. As a result, the process control of the laser processing becomes easy, and a stable process can be achieved.

[0098] In addition, in the present embodiment, the output of the laser beam L1 from the laser oscillator 130 is 40 W, so there is no need to adjust the output for the energy of 400 μJ required for peeling. In this regard, for example, when the output of the laser beam L1 is 50 W, the output of the laser beam L1 can be attenuated by 20% in the attenuator 132 to adjust the output.

[0099] In the laser irradiation unit 110 of the above-described embodiment, the acousto-optic modulator 131 is provided at a position upstream of the attenuator 132 inside the optical system 112, but the installation position is not limited thereto. For example, it may be as Figure 13 shown that the acousto-optic modulator 131 is provided at a position downstream of the attenuator 132 inside the optical system 112. Or, for example, it may be as Figure 14 shown that the acousto-optic modulator 131 is provided at a position downstream of the laser oscillator 130 inside the laser head 111. Also, the acousto-optic modulator 131 may be provided at two or more of the above-described installation positions.

[0100] In addition, in the laser irradiation unit 110, after adjusting the frequency and output of the laser beam L2 by the acousto-optic modulator 131, the output can be finely adjusted by the attenuator 132. Here, the output of the laser beam L1 oscillated from the laser oscillator 130 sometimes deviates due to individual differences of the laser oscillator 130. In the attenuator 132, such an output deviation can be adjusted. Further, when always monitoring the output of the laser beam L1 from the laser oscillator 130, feedback control can be performed on the attenuator 132 to adjust the output. Moreover, from the viewpoint of finely adjusting the output of the laser beam L2 by the attenuator 132 in this way, it is preferable to arrange the acousto-optic modulator 131 as Figure 10 shown at a position upstream of the attenuator 132.

[0101] In the laser irradiation unit 110 of the above-described embodiment, the attenuator 132 may be omitted. For example, regarding the output adjustment of the laser L2, the acousto-optic modulator 131 may be used to perform the adjustment instead of the attenuator 132. For example, when the output of the laser L1 is 50 W and the output of the laser L2 required for peeling is 40 W, in the acousto-optic modulator 131, if the deflection ratios of the lasers L2 and L3 with respect to the laser L1 are set to 80:20, the output of the laser L2 can be set to 40 W.

[0102] In the above-described embodiment, the laser L is irradiated in a spiral or concentric circle pattern onto the laser absorption layer P, but the irradiation pattern of the laser L is not limited thereto. In addition, the structure of the apparatus corresponding to such various irradiation patterns is not limited to the laser irradiation apparatus 31 of the above-described embodiment. In the above-described laser irradiation apparatus 31, the chuck 100 is rotatable about the θ axis and movable in one axial direction (Y axis), but it may also be movable in two axes (X axis and Y axis).

[0103] Figure 15 and Figure 16 The laser irradiation apparatus 200 shown in FIG. is an apparatus that moves the chuck 100 in two axes (X axis and Y axis). The laser irradiation apparatus 200 includes a chuck 210 as a holding unit that holds the stacked wafers T by its upper surface. The chuck 210 adsorbs and holds the back surface W1b of the first wafer W1. Lift pins (not shown) for supporting the stacked wafers T from below and raising and lowering the stacked wafers T are provided on the chuck 210. The lift pins pass through through-holes (not shown) formed so as to penetrate the chuck 210 and are configured to be movable up and down.

[0104] The chuck 210 is supported by a slider stage 212 via an air bearing 211. A rotation mechanism 213 is provided on the lower surface side of the slider stage 212. The rotation mechanism 213 has, for example, a motor built therein as a drive source. The chuck 210 is configured to be rotatable about the θ axis (vertical axis) via the air bearing 211 by the rotation mechanism 213. The slider stage 212 is configured to be movable along a guide rail 215 provided on a moving stage 216 and extending in the Y-axis direction by a moving mechanism 214 provided on its lower surface side. In addition, the drive source of the moving mechanism 214 is not particularly limited, and for example, a linear motor is used.

[0105] The moving stage 216 is configured to be movable along a guide rail 217 provided on a base 218 and extending in the X axis by a moving mechanism (not shown) provided on its lower surface side. In addition, the drive source of the moving mechanism is not particularly limited, and for example, a linear motor is used. With this structure, the chuck 210 is rotatable about the θ axis and movable in the X axis and the Y axis.

[0106] Above the suction cup 210, a laser irradiation unit 220 is provided. The laser irradiation unit 220 includes a laser head 221, an optical system 222, and a lens 223. The laser head 221 oscillates a laser beam L in a pulsed manner. The optical system 222 controls the intensity, position of the laser beam L, or attenuates the laser beam L to adjust the output. The lens 223 is a cylindrical member for irradiating the laser beam L, such as a CO 2 laser beam, onto the stacked wafers T held by the suction cup 210. In addition, the lens 223 is configured to be movable up and down by a lifting mechanism (not shown).

[0107] For example, a galvanometer is used for the laser head 221. A plurality of galvanometer mirrors (not shown) are disposed inside the laser head 221. Additionally, an f-θ lens is used for the lens 223. With this structure, the laser beam L input to the laser head 221 is reflected by the galvanometer mirror, propagated through the optical system 222 to the lens 223, passes through the second wafer W2, and is irradiated onto the laser absorption layer P. Moreover, by adjusting the angle of the galvanometer mirror, the laser beam L can be scanned in the laser absorption layer P.

[0108] In addition, a transfer pad 230 as a transfer unit is provided above the suction cup 210. The transfer pad 230 is configured to be movable up and down by a lifting mechanism (not shown). Moreover, the structure of the transfer pad 230 is the same as that of the transfer pad 120 in the above-described embodiment.

[0109] In this laser irradiation apparatus 200, the stacked wafers T are transferred from the transfer arm 23 to the lift pins, and the suction cup 210 adsorbs and holds the stacked wafers T. Next, the suction cup 210 is moved to the processing position by the moving mechanism 214 and the moving stage 216. This processing position is a position where the laser beam L can be irradiated from the laser irradiation unit 220 onto the stacked wafers T (laser absorption layer P).

[0110] Next, as Figure 17 shown, the laser beam L is pulsed and irradiated from the laser irradiation unit 220 onto the laser absorption layer P. At this time, the laser beam L passes through the second wafer W2 from the back surface W2b side of the second wafer W2 and is absorbed in the laser absorption layer P.

[0111] When irradiating the laser beam L onto the laser absorption layer P, the laser beam L is scanned within a predetermined scanning range A ( Figure 17 the square area in). Next, with the irradiation of the laser beam L stopped, the suction cup 210 is moved in the X-axis direction. When the irradiation and scanning of the laser beam L and the movement of the suction cup 210 are repeated in this manner, the laser beam L is irradiated in a row in the X-axis direction. Next, the suction cup 210 is moved in a staggered manner in the Y-axis direction, and the irradiation and scanning of the laser beam L and the movement of the suction cup 210 are repeated in the same manner as above to irradiate the laser beam L in a row in the X-axis direction. Thus, the laser beam L is irradiated onto the laser absorption layer P.

[0112] In addition, in the present embodiment, when irradiating the laser absorption layer P with the laser L, the chuck 210 is moved in the X-axis direction and the Y-axis direction. However, the lens 223 may be moved to relatively move the lens 223 with respect to the chuck 210.

[0113] Next, the chuck 210 is moved to the transfer position by the moving mechanism 214 and the moving stage 216. Further, the back surface W2b of the second wafer W2 is adsorbed and held by the transfer pad 230, and the transfer pad 230 is lifted to peel the second wafer W2 from the laser absorption layer P.

[0114] In the present embodiment, the same effects as those of the above-described embodiment can be obtained. That is, since the laser L is pulsed to the laser absorption layer P, the peak power of the laser L can be increased. As a result, peeling can be appropriately generated at the boundary between the laser absorption layer P and the second wafer W2. Moreover, since the laser L can be irradiated at the same density in the scanning range A, the laser L can be uniformly irradiated to the laser absorption layer P.

[0115] In addition, in the present embodiment, the laser irradiation unit 220 may be plural. In this case, the laser absorption layer P can be irradiated with a plurality of lasers L, so that the processing time can be shortened and the productivity can be further improved.

[0116] In the above-described embodiment, the irradiation and scanning of the laser L and the movement of the chuck 210 are repeated. However, as shown in Figure 18 , in one column in the X-axis direction, the irradiation and scanning of the laser L are performed while moving the chuck 210. Moreover, after irradiating the laser L in one column in the X-axis direction, the chuck 210 is moved in a staggered manner in the Y-axis direction, and the laser L is irradiated to the laser absorption layer P.

[0117] In the present embodiment, the same effects as those of the above-described embodiment can be obtained. That is, since the laser L is pulsed to the laser absorption layer P, peeling can be appropriately generated at the boundary between the laser absorption layer P and the second wafer W2. Moreover, since the irradiation and scanning of the laser L are not stopped in one column in the X-axis direction, the processing time of the laser irradiation can be shortened and the productivity can be further improved.

[0118] The irradiation of the spiral (or concentric) laser L of the above-described embodiment can be combined with the irradiation and scanning of the laser L.

[0119] When the chuck 210 (coincident wafer T) is rotated as described above, in order to fix the interval of the pulses, the rotation speed of the chuck 210 is increased as the laser L moves from the radially outer side to the radially inner side. Therefore, in the above-described embodiment, at least the rotation speed or frequency of the chuck 210 is controlled to adjust the irradiation interval of the laser L.

[0120] In contrast, as Figure 19 shown, at the outer peripheral portion of the laser absorption layer P, while rotating the chuck 210, the irradiation position of the laser L is moved from the radially outer side to the radially inner side by moving the chuck 210, so that the laser L is irradiated in a spiral shape. Moreover, when the rotation speed of the chuck 210 reaches the upper limit, the rotation of the chuck 210 is stopped at the central portion of the laser absorption layer P, and the laser L is irradiated while scanning in the scanning range A. In addition, the scanning range A is illustrated as a square, but the shape of the scanning range A is not limited thereto. For example, the scanning range A may also be circular.

[0121] By changing the irradiation pattern of the laser L at the outer peripheral portion and the central portion of the laser absorption layer P in this way, the laser L can be prevented from overlapping, and the interval of the irradiated laser L, that is, the interval of the pulses, can be fixed. As a result, the peeling of the first wafer W1 and the second wafer W2 can be uniformly performed within the wafer surface.

[0122] In addition, when the irradiation range of the laser L of the laser irradiation unit 220 is large, for example, when the irradiation range is equal to or larger than the diameter of the laser absorption layer P, the laser L can be uniformly irradiated on the entire surface of the laser absorption layer P.

[0123] In the laser irradiation device 31 of the above-described embodiment, a guide portion 240 and a holding member 250 may be provided on the upper surface of the chuck 100 as Figure 20 shown.

[0124] As Figure 21 shown, the guide portion 240 is used to guide the coincident wafer T to the chuck 100. The guide portion 240 has a vertical portion 241 provided to extend vertically upward from the chuck 100, and an inclined portion 242 provided such that the diameter increases as it goes upward from the vertical portion 241. The inner diameter of the vertical portion 241 is slightly larger than the diameter of the coincident wafer T. Moreover, the coincident wafer T disposed above the chuck 100 is centered by the inclined portion 242, and then guided to the vertical portion 241 and held by the chuck 100.

[0125] As Figure 22 and Figure 23As shown, the holding member 250 extends vertically upward from the upper surface of the chuck 100 and is used to hold the side surface of the second wafer W2. The holding members 250 are arranged at a plurality of positions, for example, three positions, on the concentric circles of the chuck 100. The holding member 250 is configured to be retractable in a manner of contacting or separating from the second wafer W2 by a moving mechanism 251. In addition, the holding member 250 is configured to be rotatable integrally with the chuck 100. Moreover, by holding the second wafer W2 with the holding member 250, the position deviation and slipping of the second wafer W2 can be prevented. In addition, a cutout portion 243 is formed at a position corresponding to the holding member 250 in the guiding portion 240, and the holding member 250 moves in the cutout portion 243, so that it does not interfere with the guiding portion 240.

[0126] In addition, in the present embodiment, both the guiding portion 240 and the holding member 250 are provided, but only the guiding portion 240 may be provided, or only the holding member 250 may be provided. In the case where only the guiding portion 240 is provided, the position deviation and slipping of the second wafer W2 can be suppressed by the vertical portion 241. In particular, when the gap between the vertical portion 241 and the second wafer W2 is within the allowable range of the position deviation, the guiding portion 240 is useful. However, when both the guiding portion 240 and the holding member 250 are provided, the centering of the stacked wafer T and the effect of preventing the position deviation and slipping of the second wafer W2 are improved.

[0127] In this case, when the stacked wafer T is held on the chuck 100 at the transfer position, the three holding members 250 are retracted to positions where they do not contact the second wafer W2. After that, after moving the chuck 100 holding the stacked wafer T to the processing position, the three holding members 250 are moved to positions where they contact the side surface of the second wafer W2, and the second wafer W2 is held by these holding members 250.

[0128] Here, in the case where there is no guiding portion 240 and holding member 250, when the laser L is irradiated spirally from the radially outer side to the radially inner side of the laser absorption layer P, as the peeling progresses, since the chuck 100 is rotating, a centrifugal force acts on the second wafer W2, and the second wafer W2 deviates from the laser absorption layer P, so that the laser L may be irradiated to a position other than the processing target position during the laser processing. In addition, the peeled second wafer W2 may also slip. In this regard, in the present embodiment, since the second wafer W2 is held by the holding member 250, the deviation and slipping of the second wafer W2 can be prevented.

[0129] Next, when the chuck 100 is moved to the transfer position after the irradiation of the laser L, the second wafer W2 is also held by the holding member 250. Here, during the movement of the chuck 100, an inertial force acts on the second wafer W2, and the second wafer W2 may shift relative to the laser absorption layer P. In this case, when the back surface W2b of the second wafer W2 is adsorbed and held by the transfer pad 120 later, it is impossible to adsorb and hold the appropriate position. Therefore, in the present embodiment, the second wafer W2 is also held by the holding member 250 during the movement of the chuck 100 to prevent the shift of the second wafer W2.

[0130] In addition, the structure of the holding member that holds the second wafer W2 is not limited to the structure of the holding member 250 described above. For example, the holding member may hold the second wafer W2 in such a manner as to clamp the upper surface and the side surface of the second wafer W2 from the side of the second wafer W2. In addition, the holding member may hold the second wafer W2 from the middle of the laser processing. In addition, when the holding member is made of a material that allows the laser L to pass through, such as silicon, the upper surface of the second wafer W2 can be held.

[0131] Although the wafer processing system 1 of the above embodiment has the cleaning device 32, the wafer processing system 1 may further include an etching device (not shown). The etching device performs an etching process on the surface W1a of the peeled first wafer W1, specifically, the surface of the laser absorption layer P. For example, after the surface of the laser absorption layer P is scrubbed by the cleaning device 32, a chemical solution (etching solution) is supplied to the surface of the laser absorption layer P to perform wet etching on the surface. In addition, the wafer processing system 1 may have either the cleaning device 32 or the etching device.

[0132] In addition, the wafer processing system 1 of the above embodiment may have a CMP device (not shown). In the CMP device, a CMP (Chemical Mechanical Polishing) process is performed on the surface W1a of the peeled first wafer W1, specifically, the surface of the laser absorption layer P. For example, after the surface of the laser absorption layer P is scrubbed by the cleaning device 32, a CMP process is performed on the surface of the laser absorption layer P to planarize the surface of the laser absorption layer P. In addition, the CMP device may be provided outside the wafer processing system 1.

[0133] In the above embodiment, the laser L is irradiated to the boundary between the laser absorption layer P and the second wafer W2 to peel the second wafer W2 from the laser absorption layer P. However, for example, it may be peeled in such a manner that the laser absorption layer P remains on the second wafer W2 as shown in Figure 24 Shown.

[0134] In this case, in the laser irradiation device 31, as shown inFigure 24 As shown in (a) of FIG. , a laser L is pulsed from the laser irradiation unit 110 to the boundary between the laser absorption layer P and the device layer D2. Then, due to this laser L, delamination occurs at the boundary between the laser absorption layer P and the device layer D2.

[0135] In addition, by controlling the energy density of the laser L required for delaminating the laser absorption layer P according to the film type of the laser absorption layer P, the light absorption position of the laser L, that is, the delamination position of the laser absorption layer P, is adjusted. For example, by changing the original output of the laser L, such as adjusting the focal length numerical aperture (NA) of the laser irradiation unit 110 or changing the focusing position of the laser L, the energy density of the laser L can be adjusted.

[0136] Next, while the back surface W2b of the second wafer W2 is adsorbed and held by the transfer pad 120, as Figure 24 shown in (b) of FIG. , the transfer pad 120 is lifted to delaminate the laser absorption layer P from the device layer D2.

[0137] In this embodiment, the same effects as those of the above-described embodiment can also be obtained. That is, since the laser L is pulsed to the laser absorption layer P, the peak power of the laser L can be increased. As a result, delamination can be appropriately generated at the boundary between the laser absorption layer P and the device layer D2. Moreover, the laser absorption layer P remaining on the second wafer W2 is an oxide film (SiO 2 film), and for example, in subsequent semiconductor manufacturing processes, this laser absorption layer P can be used as an oxide film (insulating film) when forming TSVs (Through-Silicon Vias) on the second wafer W2.

[0138] In addition, in this embodiment, the surface of the laser absorption layer P on the delaminated second wafer W2 can be scrubbed, and CMP processing can be performed in the above-described CMP apparatus. In this case, the surface of the laser absorption layer P can be planarized. Moreover, it can be appropriately used as an oxide film (insulating film) when forming TSVs as described above.

[0139] In the above embodiments, the case of processing the Figure 2 shown stacked wafer T has been described, but the processing object is not limited thereto. Hereinafter, the case of processing different types of stacked wafers T will be described using Figures 25 - 28 .

[0140] The case of processing the Figure 25 shown stacked wafer T will be described. As Figure 25As shown in (a) thereof, 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 (SiO 2 film). That is, Si as the second wafer W2, SiO as the laser absorption layer P1 2 film, and Si as the Si film S are sequentially stacked. In addition, the laser absorption layer P1 may be a film that peels at the boundary with the Si film S, and a film other than the oxide film (SiO 2 film) may be used, such as silicon germanium (SiGe) or germanium (Ge).

[0141] Next, as Figure 25 shown in (b) thereof, the device layer D2 and the 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 by ordinary substrate processes (FEOL) and wiring processes (BEOL).

[0142] Next, as Figure 25 shown in (c) thereof, the first wafer W1 and the second wafer W2 are bonded. A surface film F1 is formed on the surface W1a of the first wafer W1, and the surface film F1 is bonded to the surface film F2.

[0143] Next, in the laser irradiation device 31 of the wafer processing system 1, as Figure 25 shown in (d) thereof, the laser L is pulsed from the laser irradiation unit 110 to the boundary between the laser absorption layer P1 and the Si film S. Then, due to this laser L, peeling occurs at the boundary between the laser absorption layer P1 and the Si film S.

[0144] Next, in a state where the back surface W2b of the second wafer W2 is adsorbed and held by the transfer pad 120, as Figure 25 shown in (e) thereof, the transfer pad 120 is raised to peel the laser absorption layer P1 from the Si film S.

[0145] In addition, in the present embodiment, regarding the peeling position of the laser absorption layer P1, the light absorption position of the laser L, that is, the peeling position of the laser absorption layer P1, may be adjusted in the same manner as in the case shown in Figure 24 to cause peeling at the boundary between the second wafer W2 and the laser absorption layer P1.

[0146] The case of processing Figure 26 the bonded wafer T shown is described. As Figure 26 shown in (a) and (b) thereof, between the second wafer W2 and the device layer D2, a laser absorption layer P2 formed of silicon germanium (SiGe) and a Si film S formed of Si are sequentially stacked from the second wafer W2 side.

[0147] Next, as shown in Figure 26 (b) thereof, a device layer D2 and a surface film F2 are formed on the surface of the Si film S.

[0148] Next, as shown in Figure 26 (c) thereof, the first wafer W1 and the second wafer W2 are bonded. 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 is bonded to the surface film F2.

[0149] Next, in the laser irradiation device 31 of the wafer processing system 1, as shown in Figure 26 (d) thereof, laser L is pulsedly irradiated from the laser irradiation unit 110 to the boundary between the laser absorption layer P2 and the Si film S. Then, due to this laser L, delamination occurs at the boundary between the laser absorption layer P2 and the Si film S.

[0150] Next, as shown in Figure 26 (e) thereof, in a state where the back surface W2b of the second wafer W2 is adsorbed and held by the transfer pad 120, the transfer pad 120 is raised to peel off the laser absorption layer P2 from the Si film S. Further, in the present embodiment, regarding the peeling position of the laser absorption layer P2, the light absorption position of the laser L, that is, the peeling position of the laser absorption layer P2, may be adjusted in the same manner as in the case shown in Figure 24 to cause delamination at the boundary between the second wafer W2 and the laser absorption layer P2.

[0151] The case of processing Figure 27 the bonded wafers T shown is described. As shown in (a) and (b) of Figure 27 , a laser absorption layer P3 formed of an oxide film (SiO 2 film), a SiGe film S1 formed of SiGe, and a Si film S2 formed of Si are sequentially stacked from the second wafer W2 side between the second wafer W2 and the device layer D2.

[0152] Next, as shown in Figure 27 (b) thereof, a device layer D2 and a surface film F2 are formed on the surface of the Si film S2 formed of Si.

[0153] Next, as shown in Figure 27 (c) thereof, the first wafer W1 and the second wafer W2 are bonded. 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 is bonded to the surface film F2.

[0154] Next, in the laser irradiation device 31 of the wafer processing system 1, as shown in Figure 27As shown in (d), a laser beam L is pulsed from the laser irradiation unit 110 to the boundary between the laser absorption layer P3 and the second wafer W2. Then, due to this laser beam L, delamination occurs at the boundary between the laser absorption layer P3 and the second wafer W2.

[0155] Next, as Figure 27 shown in (e), 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 to separate the second wafer W2 from the laser absorption layer P3.

[0156] The case of the bonded wafer T shown in the Figure 28 processing will be described. The bonded wafer T has a structure in which a Ge-pMOS is stacked on a Si-nMOS. As Figure 28 shown in (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.

[0157] Next, as Figure 28 shown in (b), the first wafer W1 is bonded to the second wafer W2 which is a Ge-pMOS. On the surface W2a of the second wafer W2, a laser absorption layer P4 formed of an oxide film (SiO 2 film), a device layer D2 formed of Ge, and a surface film F2 are sequentially stacked from the second wafer W2 side.

[0158] Next, as Figure 28 shown in (b), the first wafer W1 is bonded to the second wafer W2. Specifically, the surface film F1 is bonded to the surface film F2.

[0159] Next, in the laser irradiation device 31 of the wafer processing system 1, as Figure 28 shown in (c), a laser beam L is pulsed from the laser irradiation unit 110 to the boundary between the laser absorption layer P4 and the device layer D2. Then, due to this laser beam L, delamination occurs at the boundary between the laser absorption layer P4 and the device layer D2.

[0160] Next, as Figure 28 shown in (d), 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 to separate the laser absorption layer P4 from the device layer D2. In addition, in this embodiment, regarding the delamination position of the laser absorption layer P4, the light absorption position of the laser L, that is, the delamination position of the laser absorption layer P4, can also be adjusted in the same manner as in the Figure 24 case, and delamination occurs at the boundary between the second wafer W2 and the laser absorption layer P4.

[0161] The above Figures 25 - 28Any processing object shown can achieve the same effect as the above-described embodiment.

[0162] In the bonded wafer T processed by the above embodiment, a reflective film R may also be provided between the laser absorption layer P and the device layer D2 as Figure 29 shown. That is, the reflective film R is formed on the surface of the laser absorption layer P opposite to the incident surface of the laser L. The reflective film R uses a material with a high reflectivity and a high melting point for the laser L, such as a metal film. In addition, the device layer D2 is a functional layer, different from the reflective film R.

[0163] In this case, the laser L emitted from the laser irradiation unit 110 passes through the second wafer W2 and is almost completely absorbed in the laser absorption layer P. However, even if there is unabsorbed laser L, it will be reflected by the reflective film R. As a result, the laser L does not reach the device layer D2, and damage to the device layer D2 can be reliably suppressed.

[0164] In addition, the laser 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.

[0165] The embodiments disclosed herein should be considered illustrative in all respects and not restrictive. The above embodiments can be omitted, replaced, or changed in various ways without departing from the appended claims and their gist.

[0166] Description of Reference Numerals

[0167] 31: Laser irradiation device; 100: Chuck; 110: Laser irradiation unit; D1, D2: Device layers; P: Laser absorption layer; T: Bonded wafer; W1: First wafer; W2: Second wafer.

Claims

1. A substrate processing method is a substrate processing method for transferring a device layer formed on the surface of a second substrate to a first substrate in a superposed substrate formed by bonding the first substrate and the second substrate. In this substrate processing method, laser is pulsed onto a laser absorption layer formed between the second substrate and the device layer from the back side of the second substrate. At the outer peripheral portion of the laser absorption layer, the laser is irradiated while rotating the superposed substrate. At the central portion radially inside the outer peripheral portion, the laser is scanned while the rotation of the superposed substrate is stopped.

2. The substrate processing method according to claim 1, characterized in that the energy density of the laser is controlled to adjust the light absorption position of the laser in the laser absorption layer.

3. The substrate processing method according to claim 1, characterized in that when irradiating the laser absorption layer with the laser, pulsed laser is oscillated from a laser oscillator toward an optical element, and the frequency of the laser is adjusted in the optical element.

4. The substrate processing method according to claim 3, characterized in that the pulse waveform of the laser from the laser oscillator is the same as the pulse waveform of the laser irradiated on the laser absorption layer.

5. The substrate processing method according to claim 3, characterized in that the frequency of the laser from the laser oscillator is the highest frequency that the optical element can control.

6. The substrate processing method according to claim 3, characterized in that when irradiating the laser absorption layer with the laser, the laser from the laser oscillator is attenuated in an attenuator.

7. The substrate processing method according to claim 1, characterized in that in the laser absorption layer, a reflective film is formed on the surface opposite to the incident surface of the laser, the laser in the laser irradiated on the laser absorption layer that is not absorbed by the laser absorption layer is reflected by the reflective film, and the laser reflected by the reflective film is absorbed by the laser absorption layer.

8. A substrate processing apparatus is a substrate processing apparatus for transferring a device layer formed on the surface of a second substrate to a first substrate in a superposed substrate formed by bonding the first substrate and the second substrate. The substrate processing apparatus includes: a holding portion that holds the back surface of the first substrate; a laser irradiation portion that, while the holding portion holds the first substrate, pulses laser onto a laser absorption layer formed between the second substrate and the device layer from the back side of the second substrate; a rotation mechanism that rotates the holding portion; a moving mechanism that moves the holding portion; and a control portion that controls the rotation mechanism, the moving mechanism, and the laser irradiation portion, wherein the laser irradiation portion irradiates the laser absorption layer with the laser in a scanning manner, and the control portion controls the rotation mechanism, the moving mechanism, and the laser irradiation portion to perform the following operations: at the outer peripheral portion of the laser absorption layer, the laser is irradiated while rotating the superposed substrate; At the central portion that is radially inner to the outer peripheral portion, the laser is scanned in a state where the rotation of the superposed substrate is stopped.

9. The substrate processing apparatus according to claim 8, wherein: the control unit controls the energy density of the laser to adjust the light absorption position of the laser in the laser absorption layer.

10. The substrate processing apparatus according to claim 8, wherein: the laser irradiation unit includes: a laser oscillator that oscillates the laser in a pulsed manner; and an optical element that deflects the laser from the laser oscillator in different directions, wherein the control unit controls the optical element to adjust the frequency of the laser irradiated onto the laser absorption layer.

11. The substrate processing apparatus according to claim 10, wherein: the pulse waveform of the laser from the laser oscillator is the same as the pulse waveform of the laser irradiated onto the laser absorption layer.

12. The substrate processing apparatus according to claim 10, wherein: the frequency of the laser from the laser oscillator is the highest frequency that the optical element can control.

13. The substrate processing apparatus according to claim 10, wherein: the laser irradiation unit has an attenuator that attenuates the laser from the laser oscillator.

14. The substrate processing apparatus according to claim 10, wherein: the optical element is an acousto-optic modulator.

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